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Future projections indicate that Indian Summer Monsoon Rainfall (ISMR) faces a "wetter and more variable" climate. However, the reasons remain uncertain. The Last Interglacial (LIG) climate provides a potential analog for future warming. Investigating ISMR responses to these two warming scenarios could help understand the causes of ISMR changes. Using PMIP4 simulations, we find that ISMR became "wetter and more stable" during the LIG, contrasting the future climate. The opposing changes in ISMR variability are related to divergent changes in the El Niño‐Southern Oscillation (ENSO) amplitudes, ENSO‐ISMR relationships, and ENSO‐induced large‐scale atmospheric circulation anomalies. During the LIG, orbital forcing weakened ENSO variability and its impacts on ISMR. A westward positioning of ENSO shifted the atmospheric circulation anomalies westward, suppressing extreme ISMR anomalies. These processes are supported by atmospheric model simulations. Our results suggest that different warming patterns (dynamic effects) are more critical than moisture‐increasing effects in controlling regional climate variability. Plain Language Summary: The Last Interglacial (LIG), approximately 129,000 to 116,000 years before the present, is a potential analog for future warming. We found that the variability of Indian Summer Monsoon Rainfall (ISMR) decreased while its mean state increased during the LIG, which is a "wetter and more stable" climate. This contrasts with the simultaneous increase in both the mean state and variability of ISMR projected in future warming scenarios. The opposing changes in ISMR variability during these two warm periods can be attributed to reverse changes in El Niño‐Southern Oscillation (ENSO) variability and its associated large‐scale circulation. During the LIG, reduced ENSO variability weakened the ENSO‐ISMR relationship. Sea surface temperature anomalies associated with ENSO extended westward in LIG, shifting precipitation and associated heating‐induced atmospheric circulation anomalies westward, which weakened the extreme ISMR anomalies, thus making the ISMR variability stable. This process is further supported by atmospheric general circulation model (CAM5) experiments. Our findings suggest that different external forcing‐induced warming patterns (dynamic effects) can be more critical than moisture‐increasing effects in contributing to regional climate variability change. Key Points: Indian Summer Monsoon Rainfall (ISMR) experienced a more stable climate during the LIG opposite to the change under anthropogenic warmingRelationship between ISMR and ENSO significantly weakened due to the waning ENSO variability induced by orbital forcingA westward positioning of ENSO during the LIG shifted the anomalous large‐scale circulation westward, reducing the extreme ISMR anomalies [ABSTRACT FROM AUTHOR]

In this study, the radiation scheme BCC-RAD (Beijing Climate Center RADiative transfer model) developed for global climate models is implemented into the Global–Regional Integrated SysTem (GRIST) model as an alternative to the default RRTMG (general circulation model (GCM) version of the Rapid Radiative Transfer Model) scheme. Its impact on the simulated climate is comprehensively evaluated under different physics parametrization packages, in comparison with both the CERES (partly from ERA5 reanalysis) observations and multi-model results from CMIP6. The results indicate that under the default physics parameterization package of GRIST (PhysC), BCC-RAD improved the simulated global mean cloud cover by ~3% and the clear-sky outgoing longwave radiation by ~5.6 W/m2. Upon the inclusion of the PhysCN parameterization package, BCC-RAD exhibited further improvement in simulated cloud cover and radiative forcing (particularly longwave radiative forcing, the bias of which decreases from −9.2 W/m2 to −1.8 W/m2), leading it to be closer to observations than RRTMG. Additionally, BCC-RAD improved the simulation of atmospheric temperature and hence notably diminished the apparent overestimation of atmospheric humidity seen in RRTMG. This study demonstrates the advantages of BCC-RAD over RRTMG in certain aspects of the GRIST-simulated climate, verifying its capability for the climate-oriented configuration of GRIST. [ABSTRACT FROM AUTHOR]

Toward the achievement of reliable global kilometer‐scale (k‐scale) climate simulations, we improve the Nonhydrostatic ICosahedral Atmospheric Model (NICAM) by focusing on moist physical processes. A goal of the model improvement is to establish a configuration that can simulate realistic fields seamlessly from the daily‐scale variability to the climatological statistics. Referring to the two representative configurations of the present NICAM, each of which has been used for climate‐scale and sub‐seasonal‐scale experiments, we try to find the appropriate partitioning of fast/local and slow/global‐scale circulations. In a series of sensitivity experiments at 14‐km horizontal resolution, we test (a) the tuning of terminal velocities of rain, snow, and cloud ice, (b) the implementation of turbulent diffusion by the Leonard term, and (c) enhanced vertical resolution. These tests yield reasonable convection triggering and convection‐induced tropospheric moistening, and result in better performance than in previous NICAM climate simulations. In the mean state, double Intertropical Convergence Zone bias disappears, and the zonal contrast of equatorial precipitation, top‐of‐atmosphere radiation balance, vertical temperature profile, and position/strength of subtropical jet are reproduced dramatically better. Variability such as equatorial waves and the Madden–Julian oscillation (MJO) is spontaneously realized with appropriate spectral power balance, and the Asian summer monsoon, boreal‐summer MJO, and tropical cyclone (TC) activities are more realistically simulated especially around the western Pacific. Meanwhile, biases still exist in the representation of low‐cloud fraction, TC intensity, and precipitation diurnal cycle, suggesting that both higher spatial resolutions and further model development are warranted. Plain Language Summary: In the near future, increasing computational power will make it possible to perform a global kilometer‐scale "cloud‐resolving" model (GCRM) simulation on the climate time scale, which is expected to reduce the uncertainty of cloud‐related processes in the climate system. In this sense, it is important to make GCRMs more reliable tools in the evaluation and prediction of the variabilities over a wide range of spatio‐temporal scales. With this perspective, we improve a Japanese GCRM, the Nonhydrostatic Atmospheric Icosahedral Model (NICAM), to achieve the realistic representation of both weather phenomena and climatological features in long‐term simulations. We revise the NICAM by the reconsideration of cloud microphysics properties, the implementation of diffusion processes around strong convection cores, and increased vertical layers. These revisions lead to the substantial improvements in the climatological mean precipitation distributions, radiative energy balance at the top of the atmosphere, westerly jets in the mid‐latitude, and temperature fields. We also find that weather phenomena such as the Asian summer monsoon and tropical cyclone (TC) genesis are simulated more realistically. We expect that, in addition to the above model improvements, kilometer‐scale horizontal resolutions can resolve a part of remaining issues of the representation of TC intensity and precipitation diurnal cycle. Key Points: We improve a global nonhydrostatic atmospheric model focusing on resolution‐independent errors that can exist even in k‐scale climate runsKey improvements are retuning of cloud microphysics properties, consideration of grid‐scale turbulent mixing, and increased vertical layersBiases in mean rainfall, radiation balance, and circulation as well as weather (monsoon, Madden–Julian oscillation, equatorial wave, tropical cyclone) are reduced [ABSTRACT FROM AUTHOR]

In this study, the added value in using the sea level pressure field from the coupled higher‐resolution version of the Max Planck Institute Earth System Model (MPI‐ESM‐HR), compared to the lower‐resolution version (MPI‐ESM‐LR) for circulation typing, within the regional context of Western Europe was examined. The results show that the MPI‐ESM‐HR and the MPI‐ESM‐LR simulations can produce the classified circulation types (CTs) and their long‐term statistical characteristics as obtained from the ERA5 reanalysis. Overall, there are improvements in the composite maps, probability of occurrence and annual cycle of the simulated CTs in the MPI‐ESM‐HR compared to the MPI‐ESM‐LR. The model bias in simulating the structure of anticyclonic circulations over the Western European landmass was reduced by 14% under MPI‐ESM‐HR. Furthermore, under the shared socio‐economic pathways (SSP2‐4.5 and SSP5‐8.5) future emission scenarios, the historical CTs in the region of assessment were classified, suggesting that in Western Europe, the same historical CTs are present under future climate change scenarios. However, the frequency distribution and geographical structure of some of the CTs in Western Europe are projected to change by the MPI‐ESM model, especially under the higher future emission scenario. [ABSTRACT FROM AUTHOR]

Whether the South Asian summer monsoon (SASM) is controlled by local or remote insolation at the orbital band remains uncertain. Here, we perform a transient simulation forced by Earth's orbital parameters between 400 and 350 ka BP, a period characterized by significant contrast between local and remote insolation, to identify the SASM's response to insolation forcing. Simulation results suggest that the primary driver of orbital‐scale SASM variability is the Northern Hemisphere high‐latitude June insolation, as opposed to local insolation. High June insolation in the Southern Hemisphere might reduce the SASM intensity. Remote insolation influences the SASM by altering the latitudinal thermal gradient and, consequently, the meridional position of the South Asian high (SAH). The SAH is associated with intense convection and hence drives the meridional shift of the intertropical convergence zone and the SASM rain belt. Thus, orbital‐scale SASM variability is strongly related to remote insolation forcing. Plain Language Summary: Because the monsoon is directly related to the movement of the subsolar point, insolation changes are important in regulating the South Asian summer monsoon (SASM) intensity at an orbital timescale. However, it remains unclear whether the SASM is driven by local insolation that directly strikes southern Asia, or remote insolation in the high‐latitude Northern Hemisphere or the Southern Hemisphere at the precession band. We find a time window between 400 and 350 ka BP (ka = thousand years, BP = before present) when local and remote insolations differ significantly, allowing us to determine which insolation dominates the SASM at orbital timescales. We use an Earth system model with orbital forcing to run a transient simulation between 400 and 350 ka BP. Simulations suggest that the SASM is primarily influenced by Northern Hemisphere high‐latitude summer insolation rather than local insolation. Additionally, Southern Hemisphere insolation has a negative impact on orbital‐scale SASM variability. Remote insolation influences the SASM by inducing an anomalous meridional thermal gradient, which moves the South Asian high and thus the Intertropical Convergence Zone. Our findings are significant for future SASM projections because the obvious difference between remote and local insolation will reappear in the next 50 ka. Key Points: Local insolation is not the direct driver for orbital‐scale variability of the South Asian summer monsoon (SASM)The meridional shift of the South Asian high (SAH) affects orbital‐scale SASM variabilityRemote insolation influences the meridional shift in the SAH through altering the latitudinal thermal contrast [ABSTRACT FROM AUTHOR]

Under the background of global warming, the frequency and intensity of extreme climate have increased, especially extreme high temperatures. In order to correctly predict the changes in the extreme high temperatures in summer in China in this century, it is urgent to deepen the understanding of the characteristics and physical mechanisms of the extreme high temperatures in summer on the centennial timescale. Many researchers have explored the mechanism of the influences of the variability of the solar cycle on climate change, while the mechanism of the influences of the centennial variation of solar activity on climate change remains elusive. Here, we use the outputs from the Control (CTRL) experiment, Total solar irradiance and Orbital (TSI_ORB) experiment, and Orbital (ORB) experiment from Nanjing Normal University-Holocene (NNU-Hol) experiments to study the extreme high temperatures in summer in China during the Holocene. On the basis of verifying the consistency of the centennial period between the TSI (TSI_ORB minus ORB plus CTRL) experiment and the reconstructed data, we compared the centennial variation characteristics of the summer extreme high temperature in the CTRL experiment and the TSI experiment. It shows that under the modulation of total solar irradiance, the centennial spatial pattern of the summer extreme high temperatures changed from dipole mode to uniform mode, with 300-year and 500-year periodicity, compared to the influence of only internal variability. On the centennial time scale, the greatest difference is located in northeast China. The subsidence movement and the reduction of cloud cover caused by the anticyclone under the control of high-pressure lead to the increase of downward solar radiation, thus making a positive center is showed in northeast China on the impacts of total solar irradiance. Furthermore, the center of the Rossby wave train in the barotropic structure of the upper circulation related to the summer extreme high temperature significantly moves northward. This barotropic structure is composed of continuous pressure ridges from Eurasia to North America and the North Atlantic, which is conducive to the increase of the summer extreme high temperatures. Furthermore, we investigated the underlying physical mechanisms. Under the influence of total solar irradiance, the Pacific Decadal Oscillation (PDO) with the same centennial cycle as extreme high temperatures lead to obvious subsidence movement and increase of radiation flux, causing an increase in extreme high temperatures over northeast China. [ABSTRACT FROM AUTHOR]

The features of monsoon systems in the Northern and Southern Hemispheres are analysed in climate simulations of two atmospheric models: the Brazilian Global Atmospheric Model version 1.2 (BAM‐v1.2) and the UK Met Office Hadley Centre Global Environment Model version 3 (HadGEM3). The results are compared to GPCP precipitation and ERA5 datasets. Although they have different configurations and parameterizations, the purpose is to evaluate their ability in representing key features of the global monsoon system. The spatial extent of the monsoon domains is well simulated by the models, as well as the main characteristics of the monsoons, although precipitation biases are noticed in the regions affected by the systems, consistent with vertical motion and moisture flux biases. The largest precipitation biases are found in the West Pacific Monsoon Region, extended to the east, and in the Australia Monsoon Region extended to the Maritime continent. Deficiencies in precipitation can be related to inaccuracy of vertical motion and humidity flux, as well as to the lack of air–sea interaction. However, the atmospheric circulation features at low and high levels are well represented in all monsoon regions, as well as the annual cycle of precipitation in those regions by both models. The divergence at high levels and convergence at low levels associated with ascending air movement and precipitation in monsoon regions are well represented by the models. An analysis of two monsoon indices at eight monsoon regions showed the models are generally able to simulate the relationship between precipitation and circulation features. In the majority of years, the signs of indices from the models agree with observations. Correlations of precipitation and circulation indices between models and observations show statistically significant values for some monsoon regions. The results obtained contribute to improving knowledge about global monsoon features and their representation in the two models. [ABSTRACT FROM AUTHOR]

Accurate and rapid ocean surface wave simulations are essential for navigation safety, marine activity, and climate change research. However, traditional numerical wave models incur substantial computational costs, especially in long-term simulations for climatology research. Deep-learning methods have shown promise in enabling faster simulations with fewer computational resources. However, the cumulative error in current deep-learning wave models limits their use as surrogate component models in climate modeling. In this work, a deep-learning model, named the Global Wave Surrogate Model for Climate simulation (GWSM4C), was developed based on a convolutional architecture, which accounts for the physical processes (wind waves and swells) of waves. Because GWSM4C can automatically generate initial conditions for each simulation moment depending only on historical wind fields, the accumulation of errors from previous simulated wave states can be avoided. The experimental results demonstrated that simulated global significant wave height produced by GWSM4C exhibited a correlation coefficient of 0.94 and a root-mean-square error of 0.21 m compared with the traditional numerical wave model. Furthermore, the generalization test of the GWSM4C indicates that it is feasible to use GWSM4C for long-term wave simulation in climatology-related studies or to integrate it into a coupled climate model as a surrogate wave component model. • GWSM4C is a cutting-edge cost-effective deep-learning model for climate models. • STE architectures are designed to extract wave propagation features. • GWSM4C produces global wave heights without cumulative errors using wind fields. [ABSTRACT FROM AUTHOR]

The distribution of vegetation across glacial Sundaland and the underlying mechanisms have long been debated. We address this issue by comparing a compilation of vegetation reconstructions with climate simulations from the Community Earth System Model 2 (CESM2). A new n -alkane δ13C record derived from higher plants, covering the period from 21 to 5 cal ka BP in the southern South China Sea, is presented. This record, combined with previous pollen-based reconstructions, indicates that C 3 forests dominated the outer-to-mid shelf regions of the northern Sundaland between the Last Glacial Maximum (LGM) and Heinrich Stadial 1, while open grasslands occupied the inner shelf region. A compilation of vegetation reconstructions shows a glacial contraction of lowland rainforests in longitudinal extent compared to the Holocene, especially in southern Sundaland. Furthermore, the previously proposed "savannah corridor" or "dry tropical forests" existed in the interior of Sundaland during the LGM, extending from the Malay Peninsula to the Lesser Sunda Islands. Modelling studies suggest that changes in the seasonality of precipitation, rather than mean annual rainfall, are more relevant to vegetation changes between the LGM and the Holocene. The glacial emergence of Sundaland caused an eastward shift of the ascending branch of the Walker Circulation and a substantial reduction in atmospheric convection activity over Southeast Asia, leading to a decrease in water availability during the dry season in both hemispheres. The enhanced water stress thus favors the expansion of open environments. • Regional vegetation reconstructions are compared with hydroclimate simulations from the CESM2 model. • Glacial outer-middle continental shelf of northern Sundaland was covered by rainforests. • Savannah landscape or dry tropical forests occupied the glacial interior of Sundaland. • Enhanced dry-season water stress could account for glacial expansion of open environments. [ABSTRACT FROM AUTHOR]

This study tests the nonlinear bias-correction method of regional climate model (RCM) outputs using observations from meteorological stations in the Democratic People's Republic of Korea (DPRK). The correction technique applies to both monthly precipitation and temperature simulated by the RCM, RegCM4.7 for the period 1991–2011. The correction parameters of both monthly precipitation and temperature are investigated for different periods within the observational time to assess the stability of this correction method over time. The results show that this nonlinear bias-correction approach improves significantly the accuracy of the RCM mean monthly precipitation and temperature as well as the values of probability distribution over the study area. The bias-corrected forecast has significant improvement for both monthly precipitation and temperature from about 18.9 mm and 0.7°C of mean absolute error (MAE), and about 16 mm and 0.3°C of the root mean square error over the uncorrected ones, respectively. The correlation coefficient, skill score and the MAE skill are improved significantly over the study region. The successful performance of the bias-correction technique used in this study during the calibration and validation periods will be helped to capture more accurate current climate conditions and to predict future climate change over the DPRK. [ABSTRACT FROM AUTHOR]

Dynamical downscaling generally performs poorly on the Tibetan Plateau (TP), due to the region's complex topography and several aspects of model physics, especially convection and land surface processes. This study investigated the effects of the cumulus parameterization scheme (CPS) and land-surface hydrology scheme (LSHS) on TP climate simulation during the wet season using the RegCM4 regional climate model. To address these issues and seek an optimal simulation, we conducted four experiments at a 20 km resolution using various combinations of two CPSs (Grell and MIT-Emanuel), two LSHSs (the default TOPMODEL [TOP], and Variable Infiltration Capacity [VIC]). The simulations in terms of 2-m air temperature, precipitation (including large-scale precipitation [LSP] and convective precipitation [CP]), surface energy-water balance, as well as atmospheric moisture flux transport and vertical motion were compared with surface and satellite-based observations as well as the ERA5 reanalysis dataset for the period 2006–2016. The results revealed that the model using the Grell and TOP schemes better reproduced air temperature but with a warm bias, part of which could be significantly decreased by the MIT scheme. All schemes simulated a reasonable spatial distribution of precipitation, with the best performance in the experiment using the MIT and VIC schemes. Excessive precipitation was produced by the Grell scheme, mainly due to overestimated LSP, while the MIT scheme largely reduced the overestimation, and the simulated contribution of CP to total precipitation was in close agreement with the ERA5 data. The RegCM4 model satisfactorily captured diurnal cycles of precipitation amount and frequency, although there remained some differences in phase and magnitude, which were mainly caused by the CPSs. Relative to the Grell scheme, the MIT scheme yielded a weaker surface heating by reducing net radiation fluxes and the Bowen ratio. Consequently, anomalous moisture flux transport was substantially reduced over the southeastern TP, leading to a decrease in precipitation. The VIC scheme could also help decrease the wet bias by reducing surface heating. Further analysis indicated that the high CP in the MIT simulations could be attributed to destabilization in the low and mid-troposphere, while the VIC scheme tended to inhibit shallow convection, thereby decreasing CP. This study's results also suggest that CPS interacts with LSHS to affect the simulated climate over the TP. [ABSTRACT FROM AUTHOR]

The impact of climate change on runoff characteristics is investigated for the Upper Tisza basin, in eastern Central Europe. For a reliable estimation of uncertainty, an appropriate stochastic weather generator is embedded into a Monte Carlo cycle capable of generating any large number of independent, equally probable, 100-year-long daily sequences of synthetic data with which a hydrological model is driven in order to obtain the hydrological responses to the meteorological data sequences. According to our results, a decrease of daily average runoff is likely to occur in the future in the Upper Tisza basin, especially in July and August. The occurrence of water levels below the critical low level is estimated to increase between July and October. Level-3 flood warnings are projected to be less frequent in the future; however, they will tend to be more severe than in the historical period. [ABSTRACT FROM AUTHOR]

Advances in computer technology and increasing usage of computer graphics in a broad field of applications lead to rapidly rising demands regarding size and detail of virtual landscapes. Manually creating huge, realistic looking terrains and populating them densely with assets is an expensive and laborious task. In consequence, (semi-)automatic procedural terrain generation is a popular method to reduce the amount of manual work. However, such methods are usually highly specialized for certain terrain types and especially the procedural generation of landscapes composed of different biomes is a scarcely explored topic. We present a novel system, called AutoBiomes, which is capable of efficiently creating vast terrains with plausible biome distributions and therefore different spatial characteristics. The main idea is to combine several synthetic procedural terrain generation techniques with digital elevation models (DEMs) and a simplified climate simulation. Moreover, we include an easy-to-use asset placement component which creates complex multi-object distributions. Our system relies on a pipeline approach with a major focus on usability. Our results show that our system allows the fast creation of realistic looking terrains. [ABSTRACT FROM AUTHOR]

In order to understand the pure long‐term influence of single mega volcanic eruption (SMVE) of universal significance on global and polar region temperature changes, the AD 1258 Samalas mega volcanic eruption in Indonesia which is the largest eruption over the past millennium is selected as an ideal eruption for simulation study based on Community Earth System Model. Both reconstructions and simulations show that the Northern Hemisphere experienced nearly two decades of strong cooling after the Samalas mega eruption. The significant cooling in the Arctic lasts for 16 years, while the cooling in the Antarctic lasts only 2 years. As the volcanic aerosol gradually disappears, stronger cooling occurs in Arctic winter, and warming occurs in Antarctic winter. This asymmetric temperature changes over Arctic and Antarctic after SMVE (such as Samalas) are caused by the combined effects of albedo feedback and ocean‐atmosphere heat exchange related to sea ice. Plain Language Summary: Polar climate is the focus of earth system investigation because they are very sensitive to external forcings and its related impacts on global climate. Volcanic eruption is one of the important external factors affecting global and polar climate change. The AD 1258 Samalas mega volcanic eruption in Indonesia was the largest eruption over the past millennium, which makes it an ideal eruption to study pure long‐term climatic effects of single mega volcanic eruption (SMVE). Here, we use an Earth System Model and find that the duration of surface cooling caused by SMVE (such as Samalas) is longer than we generally believed before and varies in latitude. The Northern Hemisphere experienced nearly two decades of strong cooling after the Samalas event. The significant cooling in the Arctic lasts for 16 years, while the cooling in the Antarctic lasts only 2 years. The SMVE (such as Samalas) could expand Arctic sea ice for more than two decades, but the expansion of Antarctic sea ice lasts only 2–3 years. The asymmetric temperature changes over polar regions are influenced by the combined effects of albedo feedback and ocean‐atmosphere heat exchange related to sea ice. The knowledge gained from this research is critical for improved understanding of the potential long‐term impacts of SMVE on the projected future global and polar region temperature change. Key Points: Both reconstructions and simulations show that the NH experienced nearly two decades of strong cooling after the Samalas mega eruptionA single mega volcanic eruption will cause remarkable asymmetry of temperature variation and duration between the Arctic and AntarcticAsymmetric temperature changes are caused by the combined effects of albedo feedback and ocean‐atmosphere heat exchange related to sea ice [ABSTRACT FROM AUTHOR]

Five 50-year simulations for the 5th version of the climate model of the Marchuk Institute of Numerical Mathematics, Russian Academy of Science (INM RAS), are used to analyze the interannual variability of Arctic stratospheric polar vortex and dates of spring breakup events (springtime transition) in comparison with reanalysis data. Early spring breakup events are accompanied by stronger wave activity in comparison with late ones. Winter seasons with the maximal air volume in the polar stratosphere and conditions sufficient for the formation of polar stratospheric clouds are characterized by relatively early spring breakup events. [ABSTRACT FROM AUTHOR]

During spring 2011, an extreme flood occurred along the Richelieu River located in southern Quebec, Canada. The Richelieu River is the last section of the complex Richelieu basin, which is composed of the large Lake Champlain located in a valley between two large mountains. Previous attempts in reproducing the Richelieu River flow relied on the use of simplified lumped models and showed mixed results. In order to prepare a tool to assess accurately the change of flood recurrences in the future, a state‐of‐the‐art distributed hydrological model was applied over the Richelieu basin. The model setup comprises several novel methods and data sets such as a very high resolution river network, a modern calibration technique considering the net basin supply of Lake Champlain, a new optimization algorithm, and the use of an up‐to‐date meteorological data set to force the model. The results show that the hydrological model is able to satisfactorily reproduce the multiyear mean annual hydrograph and the 2011 flow time series when compared with the observed river flow and an estimation of the Lake Champlain net basin supply. Many factors, such as the quality of the meteorological forcing data, that are affected by the low density of the station network, the steep terrain, and the lake storage effect challenged the simulation of the river flow. Overall, the satisfactory validation of the hydrological model allows to move to the next step, which consists in assessing the impacts of climate change on the recurrence of Richelieu River floods. Plain Language Summary: In order to study the 2011 Richelieu flood and prepare a tool capable of estimating the effects of climate change on the recurrence of floods, a hydrological model is applied over the Richelieu basin. The application of a distributed hydrological model is useful to simulate the flow of all the tributaries of the Richelieu basin. This new model setup stands out from past models due to its distribution in several hydrological units, its high‐resolution river network, the calibration technique, and the high‐resolution weather forcing data set used to drive the model. The model successfully reproduced the 2011 Richelieu River flood and the annual hydrograph. The simulation of the Richelieu flow was challenging due to the contrasted elevation of the Richelieu basin and the presence of the large Lake Champlain that acts as a reservoir and attenuates short‐term fluctuations. Overall, the application was deemed satisfactory, and the tool is ready to assess the impacts of climate change on the recurrence of Richelieu River floods. Key Points: An advanced high‐resolution distributed hydrological model is applied over a U.S.‐Canada transboundary basinThe simulated net basin supply of Lake Champlain and the Richelieu River discharge are in good agreement with observations of the 2011 floodThe flow simulation is challenging due to the topographic and meteorological complexities of the basin and uncertainties in the observations [ABSTRACT FROM AUTHOR]

Extratropical cyclones, major contributors to precipitation in the midlatitudes, comprise mesoscale fronts and fine‐scale convective storms. Intense oceanic cyclones pose natural hazards, making reliable projections of their changes with global warming of great interest. Here, we analyze the first ever global climate simulations to resolve such mesoscale dynamics of extratropical cyclones. The present‐day structure, frequency, and precipitation of the oceanic extratropical cyclones compare well with reanalyses and new satellite datasets that resolve the multiscale cloud‐precipitation system. Simulated precipitation from intense oceanic cyclones increases at a rate of 7%/K1, following Clausius‐Clapeyron, with warming. The same scaling is apparent also in the interhemispheric contrast, suggesting that the latter could serve as a predictor of the former. Projected changes in precipitation from intense oceanic cyclones with warming may thus be testable using a reliable global observation network of precipitation in the present day. Plain Language Summary: Precipitation in midlatitudes is strongly governed by extratropical cyclones. Its future change is of great societal concern for adaptation to a warmer world. In this study, we use a new kind of global model and a new satellite dataset to resolve fine‐scale and frontal features of cyclones and their changes with warming. The simulation shows that the amount of precipitation around the intense oceanic cyclones will increase due to global warming, and furthermore, the rate of precipitation change around the intense oceanic cyclones is closely related to the precipitation contrast between the northern and southern hemispheres in the present climate. This suggests that the future precipitation change associated with intense oceanic cyclones could be inferred from the difference between the northern and southern hemispheres in the present climate. Key Points: The first global climate simulations to explicitly represent the mesoscale dynamics of extratropical cyclones are analyzedPrecipitation from intense cyclones scales with temperatures across hemispheres and with global warming following Clausius‐ClapeyronProjected change in precipitation from intense cyclones may thus be testable using global observations of precipitation in the present day [ABSTRACT FROM AUTHOR]

The study of atmospheric chemistry-climate interactions is one of today's great computational challenges. Advances in the architecture of Graphics Processing Units (GPUs) in both raw computational power and memory bandwidth sparked the interest for General-Purpose computing on graphics accelerators in scientific applications. However, the introduction of GPUs in the High Performance Computing (HPC) landscape increased the complexity of software development, due to the inherent heterogeneity requirements of programming models and design approaches, creating a gap in uptake and attainable performance in the presently available scientific community codes. This paper provides an overview of the challenges encountered when using GPU accelerators to achieve optimal performance to calculate the kinetics of chemical tracers in climate models, the techniques used to address them and the insights gained from the process. The paper presents the development of a chemical kinetics code-to-code parser to automatically generate chemical kinetics calculations on three different generations of GPU accelerators (M2070, K80, and P100). The accelerated portion of the application achieves a speedup of up to 22×, equivalent to performance gains of +19 percent up to +90 percent compared with the processor-only version, when using a cluster of 8 Nodes with dual Intel E5-2680 v3 processor and a Kepler architecture (K80), allowing faster completion of the simulations. The paper also provides practical insights and relevant considerations for the development and acceleration of complex applications. [ABSTRACT FROM AUTHOR]

A subgrid parametrization scheme representing the enhancement of precipitation due to subgrid orography via the seeder–feeder (SF) effect has been modified to account for flow blocking in small Froude number situations. The scheme was validated in a set of limited‐area model simulations with a 1.5 km grid spacing, in which the orography was degraded by varying amounts. For simulations in which the largest orographic scales are still fairly well represented, the SF scheme was able to reduce the precipitation deficit by 30 to 70%. For simulations where the hills were completely subgrid, the SF scheme was still able to reduce the precipitation deficit by 10 to 30%. As well as increasing the integrated precipitation in global simulations with various grid spacings, some of the precipitation production was shifted from the convection scheme, with its very simple microphysical representation, to the microphysics scheme. In a long‐duration climate simulation, the SF scheme enhancements of orographic precipitation perturb the large‐scale hydrological cycle, as evidenced by the far‐field changes in both microphysical and convective precipitation. Changes over major mountain ranges were similar to those described for the case‐studies, so long as the upstream precipitation impinging on the mountains was not reduced by these changes in the global hydrological cycle. Increased atmospheric drying reduces column‐integrated resolved cloud water mixing ratios over mountains, reducing a positive bias in the amount of optically thick cloud with low‐ to mid‐level tops compared to ISCCP satellite observations. The associated reductions in cloud albedo slightly reduced the RMS error in the top‐of‐atmosphere outgoing short‐wave radiative fluxes over mountains compared to CERES satellite observations. [ABSTRACT FROM AUTHOR]

Monsoon and arid regions in the Asia-Africa-Australia (A-A-A) realm occupy more than 60% of the total area of these continents. Geological evidence showed that significant changes occurred to the A-A-A environments of the monsoon and arid regions, the land-ocean configuration in the Eastern Hemisphere, and the topography of the Tibetan Plateau (TP) in the Cenozoic. Motivated by this background, numerical experiments for 5 typical geological periods during the Cenozoic were conducted using a coupled ocean-atmosphere general circulation model to systemically explore the formations and evolutionary histories of the Cenozoic A-A-A monsoon and arid regions under the influences of continental drift and plateau uplift. Results of the numerical experiments indicate that the timings and causes of the formations of monsoon and arid regions in the A-A-A realm were very different. The northern and southern African monsoons existed during the mid-Paleocene, while the South Asian monsoon appeared in the Eocene after the Indian Subcontinent moved into the tropical Northern Hemisphere. In contrast, the East Asian monsoon and northern Australian monsoon were established much later in the Miocene. The establishment of the tropical monsoons in northern and southern Africa, South Asia, and Australia were determined by both the continental drift and seasonal migration of the Inter-Tropical Convergence Zone (ITCZ), while the position and height of the TP were the key factor for the establishment of the East Asian monsoon. The presence of the subtropical arid regions in northern and southern Africa, Asia, and Australia depended on the positions of the continents and the control of the planetary scale subtropical high pressure zones, while the arid regions in the Arabian Peninsula and West Asia were closely related to the retreat of the Paratethys Sea. The formation of the mid-latitude arid region in the Asian interior, on the other hand, was the consequence of the uplift of the TP. These results from this study provide insight to the important roles played by the earth's tectonic boundary conditions in the formations and evolutions of regional climates during geological times. [ABSTRACT FROM AUTHOR]

The article focuses on the climate change during the boring billion era in the history of Earth's deep-time evolution

We assess the effect of the Atlantic multidecadal variability (AMV) on the global monsoon using idealized simulations. Warm AMV phases are associated with a significant strengthening of monsoon precipitation over Northern Africa and India, and anomalously weak monsoon precipitation over South America. Changes in monsoon precipitation are mediated by a change in atmospheric dynamics, primarily associated with a shift in the circulation related to both an enhanced interhemispheric thermal contrast and the remote impact of AMV on the Pacific Ocean, through changes in the Walker circulation. In contrast, the thermodynamic changes are less important. Further experiments show that the impact of AMV is largely due to the tropical component of the sea surface temperature anomalies. However, the extratropical Atlantic also plays a role, especially for northern Africa. Finally, we show that the effect of AMV on monsoons is not linearly related to the magnitude of warming. Plain Language Summary: Global monsoon precipitation variability has substantial effects on about two thirds of the world's population. Therefore, understanding the factors that drive tropical precipitation is societally important. Here we focus on the effect of North Atlantic sea surface temperature (NASST) variability on global monsoon. To do so we use a set of climate model experiments, in which we add a surface temperature anomaly over the North Atlantic Ocean. The novelty of the analysis relies on the decomposition of precipitation changes to understand better their origins. We find that NASST changes have strong impacts on Sahel and Indian summer precipitation and monsoon domain sizes, through shifting northward the atmospheric patterns of moisture convergence. Changes involve increases in the large‐scale warming of the Northern Hemisphere and forcing of the eastern equatorial Pacific Ocean temperature. We highlight the tropical Atlantic basin as critical to explain the effects of NASST variability over the global monsoon. We found that changes in monsoon precipitation are sensitive to the magnitude of the NASST warming. Key Points: Changes in atmospheric circulation dominate the AMV effect on monsoons, while thermodynamic changes are moderateThe tropical North Atlantic largely forces AMV effects, by strengthening interhemispheric thermal gradients and the Walker circulationThe effects of AMV are not linearly related to the magnitude of warming [ABSTRACT FROM AUTHOR]

This study compares the interannual variance of boreal winter near-surface temperature (DJF T2m) with and without performing single model ensemble (SME) in seasonal hindcasts (DEMETER, ENSEMBLES, and NCEP CFSv2) and historical climate simulations (CMIP5). The results demonstrate that the extratropical temperature variability is significantly reduced after performing SME even though the signal in the tropical Pacific remains strong. Cancellation between positive and negative perturbations simulated by individual model members, of both tropical and extratropical origins, leads to the under-simulation. The atmospheric circulation induced by tropical Pacific sea surface temperature is not well represented in global climate models and the simulation is further deteriorated by SME, leading to an unrealistically weak interannual variance of simulated winter temperature in North America. Similar effect was also found in North Eurasia where winter temperature is strongly influenced by atmospheric internal variability and its interaction with land and ice/snow in the middle-high latitudes. The SME procedure should be avoided when evaluating the model performance in simulating the higher-order long-term statistics (such as variance). Variance of individual models should be calculated first and then averaged among members. Models used in seasonal forecast and long-term climate simulation already have good capability in simulating the long-term statistics of stochastic processes in the extratropics, although the capability in accurately simulating the temporal variation is still poor. [ABSTRACT FROM AUTHOR]

The development of model systems requires a detailed assessment of standing genetic variation across natural populations. The Brachypodium species complex has been promoted as a plant model for grass genomics with translation to small grain and biomass crops. To capture the genetic diversity within this species complex, thousands of Brachypodium accessions from around the globe were collected and genotyped by sequencing. Overall, 1897 samples were classified into two diploid or allopolyploid species, and then further grouped into distinct inbred genotypes. A core set of diverse B. distachyon diploid lines was selected for whole genome sequencing and high resolution phenotyping. Genome-wide association studies across simulated seasonal environments was used to identify candidate genes and pathways tied to key life history and agronomic traits under current and future climatic conditions. A total of 8, 22, and 47 QTL were identified for flowering time, early vigor, and energy traits, respectively. The results highlight the genomic structure of the Brachypodium species complex, and the diploid lines provided a resource that allows complex trait dissection within this grass model species. [ABSTRACT FROM AUTHOR]

This study compares the interannual variance of boreal winter near-surface temperature (DJF T2m) with and without performing single model ensemble (SME) in seasonal hindcasts (DEMETER, ENSEMBLES, and NCEP CFSv2) and historical climate simulations (CMIP5). The results demonstrate that the extratropical temperature variability is significantly reduced after performing SME even though the signal in the tropical Pacific remains strong. Cancellation between positive and negative perturbations simulated by individual model members, of both tropical and extratropical origins, leads to the under-simulation. The atmospheric circulation induced by tropical Pacific sea surface temperature is not well represented in global climate models and the simulation is further deteriorated by SME, leading to an unrealistically weak interannual variance of simulated winter temperature in North America. Similar effect was also found in North Eurasia where winter temperature is strongly influenced by atmospheric internal variability and its interaction with land and ice/ snow in the middle-high latitudes. The SME procedure should be avoided when evaluating the model performance in simulating the higher-order long-term statistics (such as variance). Variance of individual models should be calculated first and then averaged among members. Models used in seasonal forecast and long-term climate simulation already have good capability in simulating the long-term statistics of stochastic processes in the extratropics, although the capability in accurately simulating the temporal variation is still poor. [ABSTRACT FROM AUTHOR]

Investigating long-term natural precipitation variability in Northwest China is crucial for our understanding of the recent wetting trend in this region. This study explores the mechanisms of precipitation variations in Northwest China during the mid-Holocene (MH) using the Community Earth System Model (CESM). We emphasize the role of ocean feedbacks in the response of precipitation changes in the summer half-year (April–September; the rainy season of Northwest China) to orbital forcing, via comparing simulation results from the single atmosphere general circulation model (AGCM) and fully coupled atmosphere–ocean general circulation model (AOGCM) of the CESM. The AOGCM simulations reveal a decrease of precipitation in Northwest China during the MH compared to the pre-Industrial (PI) era, matching well with proxy records. The drier MH is reproduced by the AGCM with orbital forcing when the tropical Indian Ocean cooling is taken into account. The tropical Indian Ocean cooling is affected by the decrease of spring insolation, contrasting to Eurasian warming caused by the increase of summer insolation during the MH. The tropical Indian Ocean cooling contributes to a reduction of the upper-level westerlies to the south of the westerly jet axis and hence a northward shift of the westerly jet during the MH relative to the PI, via amplifying the decrease of meridional thermal gradient from the tropical Indian Ocean to northern Eurasia and weakening the strength of the South Asian high. The northward migration of the westerly jet benefits anomalous downward motion and ultimately weakens precipitation in Northwest China during the MH. Therefore, the tropical Indian Ocean plays an important role in orbital forcing of MH precipitation variations in Northwest China. We further infer that abnormal warming of the tropical Indian Ocean is probably a key factor for the recent wetting trend in Northwest China. • Model–proxy comparison reveals a wetting trend in Northwest China since the mid-Holocene. • Tropical Indian Ocean is key to orbital forcing of precipitation changes in Northwest China. • Tropical Indian Ocean warming triggers the recent wetting trend in Northwest China. [ABSTRACT FROM AUTHOR]

Abstract: Regional climate simulations over the continental United States were conducted for the 2011 warm season using the Weather Research and Forecasting model at convection‐permitting resolution (4 km) with two commonly used microphysics parameterizations (Thompson and Morrison). Sensitivities of the simulated mesoscale convective system (MCS) properties and feedbacks to large‐scale environments are systematically examined against high‐resolution geostationary satellite and 3‐D mosaic radar observations. MCS precipitation including precipitation amount, diurnal cycle, and distribution of hourly precipitation intensity are reasonably captured by the two simulations despite significant differences in their simulated MCS properties. In general, the Thompson simulation produces better agreement with observations for MCS upper level cloud shield and precipitation area, convective feature horizontal and vertical extents, and partitioning between convective and stratiform precipitation. More importantly, Thompson simulates more stratiform rainfall, which agrees better with observations and results in top‐heavier heating profiles from robust MCSs compared to Morrison. A stronger dynamical feedback to the large‐scale environment is therefore seen in Thompson, wherein an enhanced mesoscale vortex behind the MCS strengthens the synoptic‐scale trough and promotes advection of cool and dry air into the rear of the MCS region. The latter prolongs the MCS lifetimes in the Thompson relative to the Morrison simulations. Hence, different treatment of cloud microphysics not only alters MCS convective‐scale dynamics but also has significant impacts on their macrophysical properties such as lifetime and precipitation. As long‐lived MCSs produced 2–3 times the amount of rainfall compared to short‐lived ones, cloud microphysics parameterizations have profound impact in simulating extreme precipitation and the hydrologic cycle. [ABSTRACT FROM AUTHOR]

Abstract: In this two‐part paper, a description is provided of a version of the AM4.0/LM4.0 atmosphere/land model that will serve as a base for a new set of climate and Earth system models (CM4 and ESM4) under development at NOAA's Geophysical Fluid Dynamics Laboratory (GFDL). This version, with roughly 100 km horizontal resolution and 33 levels in the vertical, contains an aerosol model that generates aerosol fields from emissions and a “light” chemistry mechanism designed to support the aerosol model but with prescribed ozone. In Part 1, the quality of the simulation in AMIP (Atmospheric Model Intercomparison Project) mode—with prescribed sea surface temperatures (SSTs) and sea‐ice distribution—is described and compared with previous GFDL models and with the CMIP5 archive of AMIP simulations. The model's Cess sensitivity (response in the top‐of‐atmosphere radiative flux to uniform warming of SSTs) and effective radiative forcing are also presented. In Part 2, the model formulation is described more fully and key sensitivities to aspects of the model formulation are discussed, along with the approach to model tuning. [ABSTRACT FROM AUTHOR]

Abstract: In Part 2 of this two‐part paper, documentation is provided of key aspects of a version of the AM4.0/LM4.0 atmosphere/land model that will serve as a base for a new set of climate and Earth system models (CM4 and ESM4) under development at NOAA's Geophysical Fluid Dynamics Laboratory (GFDL). The quality of the simulation in AMIP (Atmospheric Model Intercomparison Project) mode has been provided in Part 1. Part 2 provides documentation of key components and some sensitivities to choices of model formulation and values of parameters, highlighting the convection parameterization and orographic gravity wave drag. The approach taken to tune the model's clouds to observations is a particular focal point. Care is taken to describe the extent to which aerosol effective forcing and Cess sensitivity have been tuned through the model development process, both of which are relevant to the ability of the model to simulate the evolution of temperatures over the last century when coupled to an ocean model. [ABSTRACT FROM AUTHOR]

Dimethyl sulfide (DMS) is a significant source of marine sulfate aerosol and plays an important role in modifying cloud properties. Fully coupled climate simulations using dynamic marine ecosystem and DMS calculations are conducted to estimate DMS fluxes under various climate scenarios and to examine the sign and strength of phytoplankton-DMS-climate feedbacks for the first time. Simulation results show small differences in the DMS production and emissions between pre-industrial and present climate scenarios, except for some areas in the Southern Ocean. There are clear changes in surface ocean DMS concentrations moving into the future, and they are attributable to changes in phytoplankton production and competition driven by complex spatially varying mechanisms. Comparisons between parallel simulations with and without DMS fluxes into the atmosphere show significant differences in marine ecosystems and physical fields. Without DMS, the missing subsequent aerosol indirect effects on clouds and radiative forcing lead to fewer clouds, more solar radiation, and a much warmer climate. Phaeocystis, a uniquely efficient organosulfur producer with a growth advantage under cooler climate states, can benefit from producing the compound through cooling effects of DMS in the climate system. Our results show a tight coupling between the sulfur and carbon cycles. The ocean carbon uptake declines without DMS emissions to the atmosphere. The analysis indicates a weak positive phytoplankton-DMS-climate feedback at the global scale, with large spatial variations driven by individual autotrophic functional groups and complex mechanisms. The sign and strength of the feedback vary with climate states and phytoplankton groups. This highlights the importance of a dynamic marine ecosystem module and the sulfur cycle mechanism in climate projections. [ABSTRACT FROM AUTHOR]

Different multidisciplinary data concerning the paleodynamics of sea-level variations in the Caspian and Black seas are controversial in some aspects. There are at least three paradoxes that are discussed in the paper. The Paradox No. 1 relates to the Early and Late Khvalynian transgressions that occurred in the CS during the second part of MIS 3 (∼35–25 ka BP) and the Late Glacial epoch (∼17–12 ka BP), respectively. It is unclear what the main source or sources of water were that caused them. Paradox No. 2 emerges from the comparison of climate events and transgressive-regressive cycles in the Caspian Sea and the Black Sea. It implies that large sea-level anomalies occurred in accordance with global climate changes (because they are influenced by climate variations). However, other (not so long-lived) sea-level fluctuations are poorly correlated with climate events. The question is why climatically-induced sea-level changes did not follow climatic variations. Paradox No. 3 concerns the contradiction between the massive water discharge from the Black Sea into the Sea of Marmara via the Bosphorus Strait and the Black Sea level fluctuations in the Latest Pleistocene-Holocene that could not exist simultaneously. It is shown that Paradox No. 2 has been solved, at least on conceptual level. Solutions to Paradoxes No. 1 and No. 3 are still lacking: further geological and geochronological evidence as well as climate simulation are required. Formulation of solutions for these paradoxes should make a major contribution not only to the problems of the Caspian and Black seas’ paleogeography, but also provide help in explaining the reasons for inadequate simulation of regional climate changes. This is important in the context of the development of models for future climate prediction. [ABSTRACT FROM AUTHOR]

The lifecycle of South American Monsoon System (SAMS) plays an important role on the duration of the rainy season over large areas of South America, affecting the economy through impacts on agriculture, water resources and energy management. Numerical model prediction of SAMS onset, demise and related atmospheric features is an important tool to be used in management decisions in these sectors. This information is still missing in seasonal predictions, and the purpose of this study is to examine results of a climate simulation using the CPTEC/INPE AGCM to verify its ability in simulating the SAMS onset and demise as well as the associated atmospheric features. The SAMS lifecycle is identified using an index of the zonal humidity flux in the monsoon core. The model captured the atmospheric changes associated with the SAMS lifecycle, although showing differences in intensity and maximum locations of some variables, such as the magnitude of humidity flux, sea level pressure and omega, compared to reanalysis. During the onset, the model simulated the humidity flux direction changes, the eastward shifting of the South Atlantic Subtropical High and the northwesterly moisture flux east of tropical Andes. During the demise, the model simulated the easterly moisture flux directed toward the Amazon region and the reduction of northerly/northwesterly flow over northern South America, as well as the increase of Sea Level Pressure over the continent. Results obtained using a previous version of CPTEC/INPE AGCM are discussed, mainly the improvements, in the new version, of atmospheric variables and annual cycle of precipitation. The model was able to represent the main observed features of the SAMS lifecycle. The method can be useful to identify the onset and demise dates and could be applied to results of seasonal prediction prior to the rainy season, adding information to planning and management actions. [ABSTRACT FROM AUTHOR]

The EC-Earth earth system model has been recently developed to include the dynamics of vegetation. In its original formulation, vegetation variability is simply operated by the Leaf Area Index (LAI), which affects climate basically by changing the vegetation physiological resistance to evapotranspiration. This coupling has been found to have only a weak effect on the surface climate modeled by EC-Earth. In reality, the effective sub-grid vegetation fractional coverage will vary seasonally and at interannual time-scales in response to leaf-canopy growth, phenology and senescence. Therefore it affects biophysical parameters such as the albedo, surface roughness and soil field capacity. To adequately represent this effect in EC-Earth, we included an exponential dependence of the vegetation cover on the LAI. By comparing two sets of simulations performed with and without the new variable fractional-coverage parameterization, spanning from centennial (twentieth century) simulations and retrospective predictions to the decadal (5-years), seasonal and weather time-scales, we show for the first time a significant multi-scale enhancement of vegetation impacts in climate simulation and prediction over land. Particularly large effects at multiple time scales are shown over boreal winter middle-to-high latitudes over Canada, West US, Eastern Europe, Russia and eastern Siberia due to the implemented time-varying shadowing effect by tree-vegetation on snow surfaces. Over Northern Hemisphere boreal forest regions the improved representation of vegetation cover tends to correct the winter warm biases, improves the climate change sensitivity, the decadal potential predictability as well as the skill of forecasts at seasonal and weather time-scales. Significant improvements of the prediction of 2 m temperature and rainfall are also shown over transitional land surface hot spots. Both the potential predictability at decadal time-scale and seasonal-forecasts skill are enhanced over Sahel, North American Great Plains, Nordeste Brazil and South East Asia, mainly related to improved performance in the surface evapotranspiration. [ABSTRACT FROM AUTHOR]

ABSTRACT The lifecycle of South American Monsoon System ( SAMS) plays an important role on the duration of the rainy season over large areas of South America, affecting the economy through impacts on agriculture, water resources and energy management. Numerical model prediction of SAMS onset, demise and related atmospheric features is an important tool to be used in management decisions in these sectors. This information is still missing in seasonal predictions, and the purpose of this study is to examine results of a climate simulation using the CPTEC/ INPE AGCM to verify its ability in simulating the SAMS onset and demise as well as the associated atmospheric features. The SAMS lifecycle is identified using an index of the zonal humidity flux in the monsoon core. The model captured the atmospheric changes associated with the SAMS lifecycle, although showing differences in intensity and maximum locations of some variables, such as the magnitude of humidity flux, sea level pressure and omega, compared to reanalysis. During the onset, the model simulated the humidity flux direction changes, the eastward shifting of the South Atlantic Subtropical High and the northwesterly moisture flux east of tropical Andes. During the demise, the model simulated the easterly moisture flux directed toward the Amazon region and the reduction of northerly/northwesterly flow over northern South America, as well as the increase of Sea Level Pressure over the continent. Results obtained using a previous version of CPTEC/ INPE AGCM are discussed, mainly the improvements, in the new version, of atmospheric variables and annual cycle of precipitation. The model was able to represent the main observed features of the SAMS lifecycle. The method can be useful to identify the onset and demise dates and could be applied to results of seasonal prediction prior to the rainy season, adding information to planning and management actions. [ABSTRACT FROM AUTHOR]

ABSTRACT During the austral summer of 2014 and 2015, a severe drought occurred in southeastern Brazil at the same time when flooding conditions were registered in the state of Acre in the western Amazonia of Brazil. This study aimed the identification of the atmospheric and oceanic large-scale characteristics and regional features associated with these conditions, and verification of the Center of Weather Forecasting and Climate Studies/National Institute of Space Research (CPTEC/INPE) atmospheric global circulation model ability in reproducing the observed features. The state of Acre was chosen as a pilot area of the PULSE-Brazil project - a web platform tool that contains climate, ecological and health data for Brazil. The observational data and model results were analysed for the climatological period of 1981-2010. Correlation analyses between precipitation over west Amazon and atmospheric and oceanic variables indicated the main patterns in both data sets. Extreme wet and dry Januaries over west Amazon were selected to explore the regional and large-scale associated features. The general results of climate analyses indicated an opposite relation of precipitation between western Amazon and southeastern Brazil, in January, besides the typical precipitation dipole between the south Atlantic convergence zone and southeastern South America. This configuration is related to anomalous humidity flux at low levels and associated anomalous sea level pressure over southeastern South America induced by subsidence. The role of convection anomalies over the Pacific Ocean on South America anomalies is discussed. The wet and dry cases in Acre region display opposite atmospheric anomalies over South America that are linked to wavetrains over the Pacific Ocean, likely related to the opposite conditions of Indonesia-Pacific tropical convection. Similar patterns of the dry cases were observed during January of 2014 and 2015. The model reproduced some observed atmospheric patterns related to precipitation extremes and the results are discussed in terms of regional and large-scale climate variability. [ABSTRACT FROM AUTHOR]

A reconstructed land use/land cover change (LUCC) dataset was used with the Community Earth System Model (CESM) to conduct a climate sensitivity analysis over the past two millennia. Compared to a controlled experiment conducted with the CESM, the LUCC showed significant biogeophysical effects on global climate on multi-decadal to centennial time scales. The global annual mean temperature and precipitation show clear decadal and multi-centennial scale oscillations when the LUCC effect was considered in the CESM simulation. With increased crop acreage and decreased natural vegetation over the past two millennia, the reflected terrestrial solar radiation has increased and the net terrestrial radiation has decreased, leading to a decrease in the global annual mean temperature. Global annual mean precipitation has also decreased along with decreased evaporation and atmospheric humidity. Our simulation suggests that LUCC mainly influences convective precipitation and has little influence on large-scale precipitation. The impact of LUCC has latitudinal and seasonal differences. The largest response of temperature to LUCC has occurred in the middle latitudes of the Northern Hemisphere (NH), while the largest precipitation response occurred at lower latitudes of the NH. The responses of temperature and precipitation to LUCC is stronger in winter and spring than in summer and autumn. [ABSTRACT FROM AUTHOR]

This study provides an overview of the Asian monsoon and its change as simulated by atmosphere-ocean coupled general circulation models and high-resolution atmospheric general circulation models, focusing on the seasonal mean circulation and precipitation climatology. After reviewing the drivers of and the elements that affect the monsoon, the ability of those climate models to reproduce the Asian monsoon is assessed. The Asian monsoon is better reproduced in the Coupled Modeling Intercomparison Project phase 5 (CMIP5) models than in the CMIP3 models, although biases remain. Projected future changes in the Asian monsoon at the end of the 21st century are then reviewed. Overall projections are similar for both CMIP3 and CMIP5 models with increases in precipitation, albeit with weakened circulation in the South Asian summer, enhanced circulation and increased precipitation in the East Asian summer, and latitude-dependent changes in the winter monsoon circulation in East Asia. However, differences exist in the projected local changes, leading to uncertainty in projections. [ABSTRACT FROM AUTHOR]

The abrupt shift of the East Asian winter monsoon (EAWM) is closely linked to the Atlantic meridional overturning circulation (AMOC) triggered by freshwater hosing at millennium timescale. However, the mechanisms of the EAWM response to North Atlantic freshwater forcing are still not fully understood. This study focuses on the role of the Tibetan Plateau in millennium-scale EAWM variability, both in terms of the Siberian high and monsoonal northerlies, by performing two groups of sensitivity experiments at 8.2 ka BP forced by the same North Atlantic freshwater hosing, with different scenarios of the topography of the Tibetan Plateau. Simulation results reveal that the Tibetan Plateau played a crucial role in the EAWM response to North Atlantic freshwater forcing. Despite anomalous surface cooling over the Siberian and Mongolian regions caused by the slowdown of the AMOC, North Atlantic freshwater hosing could not effectively enhance the Siberian high with the lower Tibetan Plateau. Furthermore, with the lower Tibetan Plateau, the hosing-induced enhancement of monsoonal northerlies over East Asian coastal regions dramatically dwindled. The role of the Tibetan Plateau was mainly via amplifying the westward shift of the Asian subtropical westerly jet, which was triggered by AMOC-induced increase of meridional thermal gradient at 500 hPa over West Asia. The westerly jet's westward shift generated anomalous updrafts over the Northwest Pacific and Tibetan Plateau. The former updrafts created an anomalous cyclone over the Northwest Pacific, enhancing the monsoonal northerlies. The latter updrafts induced compensating downdrafts over Mongolia, and hence enhanced the Siberian high. Our results emphasize that the enhanced EAWM during the North Atlantic cold events was most likely linked to the upper-level westerly jet rather than the previous proposed local surface cooling. • The Tibetan Plateau played a critical role in millennium-scale EAWM variability. • Freshwater hosing enhanced the EAWM via the westward shift of the westerly jet. • The Tibetan Plateau amplified the westward movement of the westerly jet. [ABSTRACT FROM AUTHOR]

The animal species depicted in the rock art of Shuwaymis, Saudi Arabia, provide a record of Holocene climatic changes, as seen by the engravers. Of 1903 animal engravings, 1514 contained sufficient detail to allow identification with confidence. In addition, the stratigraphy of the engravings and the depiction of domesticates provide a broad chronological framework that allows a division into images created during the Holocene humid phase and animals represented after the onset of desert conditions. Despite the large sample size, only 16 animal species could be identified, which represents an extraordinarily narrow species spectrum. Comparison with the scarce faunal record of the Arabian Peninsula shows that all larger animals that are thought to have been present in the area were also depicted in the rock art. The contemporaneous presence of at least four large carnivores during the Holocene humid phase suggests that prey animals were abundant, and that the landscape consisted of a mosaic of habitats, potentially with thicker vegetation along the water courses of the wadis and more open vegetation in the landscape around them. Community Earth System Models (COSMOS) climate simulations show that Shuwaymis was at the northern edge of the African Summer Monsoon rainfall regime. It is therefore possible that Shuwaymis was ecologically connected with southwestern Arabia, and that an arid barrier remained in place to the north, restricting the dispersal of Levantine species into Arabia. [ABSTRACT FROM AUTHOR]

Several proxy data indicate an aridification of the East African climate during the Neogene, which might be influenced by the orographic changes of the East African Rift System (EARS) induced by tectonic forcing during the last 20 million years. To investigate the impact of the orography and especially of the rifts, the regional climate model CCLM is used, covering the EARS with Lake Victoria in the centre of the model domain. CCLM is driven by the ERA-Interim reanalysis and applied with a double-nesting method resulting in a very high spatial resolution of 7 km. The resolution clearly shows the shoulders and rifts of the western and eastern branch of the EARS and the Rwenzoris within the western branch. To analyse the orographic influence on climate, a new technique of modifying the orography is used in this sensitivity study. The shoulders of the branches are lowered and the rifts are elevated, resulting in a smoothed orography structure with less altitude difference between the shoulders and rifts. The changes in 2 m-temperature are very local and associated with the changes in the orography. The vertically integrated moisture transport is characterised by less vortices, and its zonal component is increased over the branches. The resulting amount of precipitation is mainly decreased west of the western branch and increased in the rift of the western branch. In the eastern branch, however, the changes in the amount of precipitation are not significant. The changes in the precipitation and temperature patterns lead to a shift of biomes towards a vegetation coverage characterised by more humid conditions in the northern part of the model domain and more arid conditions in the South. Thus, the aridification found in the proxy data can be attributed to the orographic changes of the rifts only in the northern model domain. [ABSTRACT FROM AUTHOR]

Climate change and extreme climate events have a significant impact on societies and ecosystems. As a result, climate change projections, especially related with extreme temperature events, have gained increasing importance due to their impacts on the well-being of the population and ecosystems. However, most studies in the field are based on coarse global climate models (GCMs). In this study, we perform a high resolution downscaling simulation to evaluate recent trends of extreme temperature indices. The model used was Weather Research and Forecast (WRF) forced by MPI-ESM-LR, which has been shown to be one of the more robust models to simulate European climate. The domain used in the simulations includes the Iberian Peninsula and the simulation covers the 1986–2005 period (i.e. recent past). In order to study extreme temperature events, trends were computed using the Theil-Sen method for a set of temperature indexes defined by the Expert Team on Climate Change Detection and Indices (ETCCDI). For this, daily values of minimum and maximum temperatures were used. The trends of the indexes were computed for annual and seasonal values and the Mann-Kendall Trend test was used to evaluate their statistical significance. In order to validate the results, a second simulation, in which WRF was forced by ERA-Interim, was performed. The results suggest an increase in the number of warm days and warm nights, especially during summer and negative trends for cold nights and cold days for the summer and spring. For the winter, contrary to the expected, the results suggest an increase in cold days and cold nights (warming hiatus). This behavior is supported by the WRF simulation forced by ERA-Interim for the autumn days, pointing to an extension of the warming hiatus phenomenon to the remaining seasons. These results should be used with caution since the period used to calculate the trends may not be long enough for this purpose. However, the general sign of trends are similar for both simulations despite some differences in their magnitudes. [ABSTRACT FROM AUTHOR]

Recent advances in high-performance computing technologies, applied in climate science, are allowing increases in model complexity, model resolution, and the number of simulations run. The interactive exploration and analysis of these complex, multi-field climate data sets have been identified as one of the major current challenges in scientific visualization. For example, without direct 3D multi-field visualization, it is difficult to recognize the important correlative effects between vertical wind velocities and transport of the volumetric atmosphere. As such data have complicated 3D structures and are highly time-dependent, a visualization approach must handle these dynamic data in a highly interactive way. In this paper, an efficient multi-field visualization framework is proposed for Earth climate simulation data. A novel visualization pipeline is presented for on-demand data processing, enabling scalable handling of large-scale climate data sets. The hardware-accelerated multi-field visualization method used in the framework allows interactive and accurate visualization of multiple intersecting climate phenomena. An information-theoretic-based wind-field analysis method is also implemented within the visualization framework to help scientists gain a deeper understanding of the underlying multi-field climate data. Graphical abstract: [ABSTRACT FROM AUTHOR]

Regional climate simulation can generally be improved by using an RCM nested within a coarser-resolution GCM. However, whether or not it can also be improved by the direct use of a state-of-the-art GCM with very fine resolution, close to that of an RCM, and, if so, which is the better approach, are open questions. These questions are important for understanding and using these two kinds of simulation approaches, but have not yet been investigated. Accordingly, the present reported work compared simulation results over China from a very-fine-resolution GCM (VFRGCM) and from RCM dynamical downscaling. The results showed that: (1) The VFRGCM reproduces the climatologies and trends of both air temperature and precipitation, as well as inter-monthly variations of air temperature in terms of spatial pattern and amount, closer to observations than the coarse-resolution version of the GCM. This is not the case, however, for the inter-monthly variations of precipitation. (2) The VFRGCM captures the climatology, trend, and inter-monthly variation of air temperature, as well as the trend in precipitation, more reasonably than the RCM dynamical downscaling method. (3) The RCM dynamical downscaling method performs better than the VFRGCM in terms of the climatology and inter-monthly variation of precipitation. Overall, the results suggest that VFRGCMs possess great potential with regard to their application in climate simulation in the future, and the RCM dynamical downscaling method is still dominant in terms of regional precipitation simulation. [ABSTRACT FROM AUTHOR]

Three different estimates of shortwave attenuation depth (SWAD) of photosynthetically active radiation (PAR) derived from remotely sensed ocean colour data have been tested in an ocean general circulation model (OGCM) forced with interannual atmospheric forcings. Two estimates (referred to as [ K d (PAR) ] 1 - 1 and [ K d (PAR) ] 2 - 1 ) are calculated from different algorithms based on the diffusive attenuation coefficient at 490 nm and the third one ( [ K d (AVE) ] 1 - 1 ) is just an average of [ K d (PAR) ] 1 - 1 and [ K d (PAR) ] 2 - 1 . [ K d (PAR) ] 2 - 1 is larger than [ K d (PAR) ] 1 - 1 almost everywhere in the tropical oceans. Our results show that the OGCM with [ K d (PAR) ] 2 - 1 produces warmer sea surface temperature (SST) in the eastern equatorial Pacific and Atlantic and leads to reduce a cold bias in the equatorial cold tongue regions. It has warmer subsurface temperatures in the low latitude, a slower meridional velocity and Pacific equatorial undercurrent (EUC) than the model with [ K d (PAR) ] 1 - 1 . These results are similar to previous studies, although we use a different model and different methods. This study has further analysis and firstly reveals that slower EUC and meridional velocity in the model with [ K d (PAR) ] 2 - 1 are mainly related to the changes of the acceleration due to zonal density gradient. This acceleration driving the EUC eastward in the subsurface becomes smaller in the subsurface along the equatorial Pacific. However, near the sea surface, the zonally averaged accelerations over the different ocean basins are larger in the model with [ K d (PAR) ] 2 - 1 than that with [ K d (PAR) ] 1 - 1 , which pushes back the poleward meridional transport. The interannual variability in the model with [ K d (PAR) ] 2 - 1 is generally weaker than that in the experiment with [ K d (PAR) ] 1 - 1 due to a deeper mixed layer depth. The vertical temperature errors averaged horizontally within the domain of 30°S to 30°N in the experiment with [ K d (AVE) ] 1 - 1 are almost in the middle of errors of the other two experiments. This indicates that the effect of the SWAD on the simulation of the vertical temperature profile is largely linear. [ABSTRACT FROM AUTHOR]

In-process measurements by machine tools offer high product quality, lower manufacturing costs, high productivity and a real-life assessment of product quality. Measurement errors of machine tools are influenced by complex environmental factors on the shop floor (e.g. temperature). The project “Traceable In-Process Dimensional Measurement” (TIM) aims for the ability to measure fabricated parts accurately in-process under the influence of the previously named factors. The development of a mobile climate simulation chamber is one of the work packages in this project and has the objective to simulate shop floor conditions to which a machine tool is exposed in its daily use. Based on the analysis of the variety of influencing factors, different concepts for the design of the mobile simulation chamber have been elaborated and the final concept was chosen. The validation of the final concept was supported by a computational fluid dynamics simulation and a modified temperature sensor distribution that is fit for the described purpose with regard to the mobility and thermal stability of the system. [ABSTRACT FROM AUTHOR]

Using the low-resolution (T31, equivalent to 3.75° × 3.75°) version of the Community Earth System Model (CESM) from the National Center for Atmospheric Research (NCAR), a global climate simulation was carried out with fixed external forcing factors (1850 Common Era. (C.E.) conditions) for the past 2000 years. Based on the simulated results, spatio-temporal structures of surface air temperature, precipitation and internal variability, such as the El Niño-Southern Oscillation (ENSO), the Atlantic Multi-decadal Oscillation (AMO), the Pacific Decadal Oscillation (PDO), and the North Atlantic Oscillation (NAO), were compared with reanalysis datasets to evaluate the model performance. The results are as follows: 1) CESM showed a good performance in the long-term simulation and no significant climate drift over the past 2000 years; 2) climatological patterns of global and regional climate changes simulated by the CESM were reasonable compared with the reanalysis datasets; and 3) the CESM simulated internal natural variability of the climate system performs very well. The model not only reproduced the periodicity of ENSO, AMO and PDO events but also the 3-8 years variability of the ENSO. The spatial distribution of the CESM-simulated NAO was also similar to the observed. However, because of weaker total irradiation and greenhouse gas concentration forcing in the simulation than the present, the model performances had some differences from the observations. Generally, the CESM showed a good performance in simulating the global climate and internal natural variability of the climate system. This paves the way for other forced climate simulations for the past 2000 years by using the CESM. [ABSTRACT FROM AUTHOR]

A method is described for the generation of climate scenarios in a form suitable for driving agricultural models. The scenarios are tailored to the region in southeastern South America bounded by 25–40° S, 45–65° W, denoted here as SESA. SESA has been characterized by increasing summer precipitation, particularly during the late 20th century, which, in the context of favorable market conditions, has enabled increases in agricultural production. Since about year 2000, however, the upward tendency appears to have slowed or possibly stopped, raising questions about future climate inputs to regional agricultural yields. The method is not predictive in the deterministic sense, but rather attempts to characterize uncertainty in near-term future climate, taking into account both forced trends and unforced, natural climate fluctuations. It differs from typical downscaling methods in that GCM information is utilized only at the regional scale, subregional variability being modeled based on the observational record. Output, generated on the monthly time scale, is disaggregated to daily values with a weather generator and used to drive soybean yields in the crop model DSSAT-CSM, for which preliminary results are discussed. The simulations produced permit assessment of the interplay between long-range trends and near-term climate variability in terms of agricultural production. [ABSTRACT FROM AUTHOR]

Three different estimates of shortwave attenuation depth (SWAD) of photosynthetically active radiation (PAR) derived from remotely sensed ocean colour data have been tested in an ocean general circulation model (OGCM) forced with interannual atmospheric forcings. Two estimates (referred to as [Kd(PAR)1-1 and [Kd(PAR)]2-1) are calculated from different algorithms based on the diffusive attenuation coefficient at 490 nm and the third one ([Kd (AVE)]1-1 is just an average of [Kd(PAR)]1-1 and [Kd(PAR)]2-1. [Kd (PAR)]2-1 is larger than [Kd(PAR)]1-1 almost everywhere in the tropical oceans. Our results show that the OGCM with [Kd(PAR)]1-1 produces warmer sea surface temperature (SST) in the eastern equatorial Pacific and Atlantic and leads to reduce a cold bias in the equatorial cold tongue regions. It has warmer subsurface temperatures in the low latitude, a slower meridional velocity and Pacific equatorial undercurrent (EUC) than the model with [Kd(PAR)]1-1. These results are similar to previous studies, although we use a different model and different methods. This study has further analysis and firstly reveals that slower EUC and meridional velocity in the model with [Kd (PAR)]2-1 are mainly related to the changes of the acceleration due to zonal density gradient. This acceleration driving the EUC eastward in the subsurface becomes smaller in the subsurface along the equatorial Pacific. However, near the sea surface, the zonally averaged accelerations over the different ocean basins are larger in the model with [Kd(PAR)]2-1 than that with [Kd(PAR)]1-1, which pushes back the poleward meridional transport. The interannual variability in the model with [Kd(PAR)]2-1 is generally weaker than that in the experiment with [Kd(PAR)]1-1 due to a deeper mixed layer depth. The vertical temperature errors averaged horizontally within the domain of 30°S to 30°N in the experiment with [Kd(AVE)]1-1 are almost in the middle of errors of the other two experiments. This indicates that the effect of the SWAD on the simulation of the vertical temperature profile is largely linear. [ABSTRACT FROM AUTHOR]

Decadal-scale oscillations of the level of the Caspian Sea (CS) primarily stem from variations in runoff from the Volga River. Therefore, although the image of the CS within the climate models is very simplified, changes in the level of the CS can be used to assess the ability of climate models to reproduce the water budget over the East European Plain. The proxy dataset comprises a number of detailed maps of the CS for the main regression stages and transgression stages during the last 30 ka together with information about sea-level positions. We compare observed or reconstructed CS level positions during the last millennium and modern periods with the CS level positions calculated based on simulations in experiments using the CMIP5/PMIP3 protocol. The modelled data could be verified based on how well the models simulate: a) the observed decadal-scale CS level dynamics during the twentieth century; and b) the Derbentian regression, transition to New-Caspian (5th phase) highstand and slight lowering of the CS level at the end of the nineteenth century. [ABSTRACT FROM AUTHOR]