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Aerosols significantly affect cloud microphysics and energy budget in different ways. The contribution of the direct, semi‐direct, and indirect effects of aerosols on radiation are here investigated over the North Atlantic tropical ocean under different aerosol loadings. The Weather Research and Forecasting Model is used to perform a set of numerical idealized experiments, which are forced with prescribed aerosol profiles. We evaluate the effects of aerosols on modeled shallow clouds and surface radiative budget. The results indicate that large aerosol loadings are associated with enhanced cloudiness and reduced precipitation. While the change in rainfall is mainly due to the larger number of smaller droplets, the change in cloudiness is attributed to the effects of absorbing aerosols, mainly dust particles, which are responsible for a rise of temperature that feeds back onto specific humidity. As in the boundary layer the increase of moisture dominates, the net effect is a higher relative humidity, which favors the formation of thin low non‐precipitating clouds. The feedback accounts for a dynamical change in the lower troposphere: shortwave radiation absorption increases temperature at the top of the marine atmospheric boundary‐layer and reduces entrainment of warm and dry air, increasing low level moisture content. Despite the overall increase in cloudiness, daytime cloud cover is reduced. The semi‐direct effect of aerosols on clouds results in a warming of the surface, opposite to the indirect effect. [ABSTRACT FROM AUTHOR]

Quantitative assessment of urbanization effect on surface air temperature (SAT) change provides crucial basis for formal detection and attribution analyses of climate change. However, debates about urbanization‐related warming bias in documented regional SAT trend still persist, mainly due to different determination of rural stations. Here the urbanization effect on SAT change over the Beijing–Tianjin–Hebei region in China during 1980–2019 is estimated through three kinds of ways (i.e., comparisons between urban and rural stations [arithmetically station‐averaged], urban‐dominated and rural‐dominated patches [patch‐weighted mean], and realistic urban and rural areas [area‐weighted mean]). The last method explicitly takes urban and rural land cover fractions into account when calculating urban/rural and regional mean SAT trends. Urbanization‐induced warming in the annual mean SAT change of urban stations (areas) through the three ways are estimated as 0.159°C, 0.195°C, and 0.138°C per decade, respectively. And urbanization effect on regional averaged annual mean SAT calculated by patch‐weighted and area‐weighted methods are 0.113°C and 0.050°C per decade, respectively, which account for 33.8% and 14.8% of the total regional warming. The urbanization effect on observed SAT change estimated by considering realistic urban/rural land cover proportions is much lower than traditional station‐unweighted way. [ABSTRACT FROM AUTHOR]

Using the daily 2 m maximum temperature (Tmax), 2 m minimum temperature (Tmin) and cloud cover data measured at ground sites of the China Meteorological Administration in North China from 2000 to 2017, this study investigates the influence of clouds on the daily temperature range (DTR) defined as the difference between Tmax and Tmin. As expected, the cloud cover shows the similar averaged spatial distribution and monthly variation with Tmin. Surprisingly, it also shows the similar average spatial distribution and monthly variation with Tmax, suggesting the more important roles of regions (latitude) and seasons associated with the variations of land surface temperature, which is further related to solar radiation absorbed and surface heat capacity. By comparing monthly variations of temperature between cloudy and clear skies, we find that clouds can weaken Tmax and increase Tmin, and thus decrease DTR. As a result, the spatial distribution of DTR is opposite to the cloud cover. The clouds have relatively stronger impact on Tmin and DTR over mountain region, which is most likely caused by the stronger longwave cloud radiative forcing associated with higher cloud tops over the mountain region. [ABSTRACT FROM AUTHOR]

To investigate the relationship among summer atmospheric boundary layer (ABL) over the Taklimakan Desert (TD), its land surface parameters and large scale meteorological field, the Urumqi Institute of Desert Meteorology of China Meteorological Administration conducted a comprehensive observation of boundary layer in Tazhong, the hinterland of TD from July 1 to 31, 2016. The correlations between the ABL height and surface sensible heat, latent heat, air temperature, turbulent kinetic energy (TKE) and buoyancy term are analyzed by using the observed GPS sounding data, the surface layer micro meteorological data in the hinterland of the TD and ERA5 reanalysis data so as to study the correlation of the ABL height and Eurasian circulation field. The research results indicate: (1) The height of summer ABL over the TD does not fully correspond with the variation tendency of surface sensible heat flux. In addition to surface sensible heat, large scale advection and residual mixed layer (RML) are also crucial factor influencing ABL. (2) The surface TKE over the TD is consistent with ABL height variation, with the correlation coefficient of 0.62. Hence the equation of ABL height and TKE is expressed as: Y = 1609.2X4 – 12,828X3 + 35,617X2 –39,514X + 15,858. (3) When the ABL height over the TD is quite high, 500 hPa altitude in Xinjiang is mostly controlled by anticyclone circulation, and the easterly low level jet (LLJ) tends to be formed at 850 hPa the next night. (4) The high correlation areas of summer ABL height over the TD and Eurasian temperature field are Xinjiang and Balkash Lake region. Significant positive correlation is identified between the ABL height and the temperature field at 850, 700, and 500 hPa of the above regions. The maximum correlation coefficient reaches 0.7. The study deepens the understanding of the relationship among the ABL process over the TD, land surface parameters and Eurasian circulation. [ABSTRACT FROM AUTHOR]

Previous studies indicate that convective heating variability of the western North Pacific summer monsoon (WNPSM) influences strongly weather and climate over East Asia. Based on daily reanalysis data and interpolated outgoing longwave radiation (OLR) data, this study demonstrates that the WNPSM convection can also cause severe weather events remotely over the Antarctic through the exciting of the Australia‐South Pacific‐Atlantic wave train (ASPA pattern). Surface air temperature (SAT) rises over the Ross Sea‐Mawson‐Dumont d'Urville Seas sector and over the Weddell Sea, while the SAT drops over the Amundsen–Bellingshausen Seas. Concurrently, sea ice concentration (SIC) is reduced over the Ross Sea and enhanced over the Amundsen–Bellingshausen Seas. The result suggests that the newly found ASPA pattern may serve as an important bridge linking the WNPSM convection and the weather over the Antarctic region. The dynamics of ASPA's formation and propagation are also investigated comprehensively. Day‐to‐day energy budget analysis suggests that after its initiation by WNPSM convection, the ASPA pattern is driven by the baroclinic energy conversion from the climatological flow and nonlinear term. The barotropic energy conversion from the climatological flow contributes to positive KE tendency before day +1 and negative KE tendency after day +1. It is therefore extremely important to improve the representations of the climatological‐mean sea ice and jet stream, wave‐mean flow interaction and wave‐wave interaction in the mid‐ and high‐latitudes of the Southern Hemisphere, as well as the convection over the WNPSM region of the Northern Hemisphere in numerical model for a better weather prediction for the Antarctic. [ABSTRACT FROM AUTHOR]

We investigated interdecadal relationship changes between the Arctic oscillation (AO) and Aleutian low (AL) for the period 1980–2021 along with the linkage on surface air temperature (SAT) over Eastern Eurasia during the boreal winter (December–January–February). The AO–AL relationship has weakened since the mid‐1990s. To explore a possible explanation, we compared atmospheric fields for two contrasting periods, one when the AO–AL relationship is the strongest (1986–2006) and one when it is the weakest (2000–2020). In both periods, atmospheric circulation over the Arctic region for the two AO–AL in‐phase relationships (i.e., either +AO/+AL or –AO/−AL) evolves with negative AO‐like patterns, contributing to a weakening AO–AL relationship in concurrent with a cool SAT in Eastern Eurasia. We found that the correlation between AL and SAT over Eastern Eurasia decreases, while the AO and SAT correlation remains unchanged. This implies that low‐frequency atmospheric circulation changes such as those of the AO and AL should be considered when studying SAT changes in Eastern Eurasia. [ABSTRACT FROM AUTHOR]

Extreme temperature events causing significant environmental and humanitarian impacts are expected to increase in frequency and magnitude due to global warming. The latest generation of climate model projections, Coupled Model Intercomparison Project Phase Six (CMIP6), provides a new and improved database to investigate change in future daily scale extreme temperature events. This study examines the changes in 1, 3, and 5 day averaged annual maximum temperature in four large CMIP6 ensembles. It analyses, using a generalized extreme value (GEV) method, the change in extreme daily mean temperatures at 1.5 and 2°C of global warming, levels highlighted by the 2016 Paris Agreement, and additionally at 3°C. Extremely hot events are characterized using the annual maxima of daily near surface air temperature in the SSP370 scenario. Global changes in the mode of the distributions (location parameter) follow long‐term summer warming and show very similar spatial patterns. Changes in variability (scale parameter) show a clear trend of increases over the tropics and decreases over higher latitudes, while changes to the tails of distributions (shape parameter) show less globally consistent trends but clear signals over the Arctic sea ice, behaviour also seen in variability. Risk ratios (RRs) indicating the change in probability of hot daily extremes that currently have a 10 year return period increase globally with mean temperature change, with greater increases over the tropics. Globally averaged changes in RR over land range from 3.1–3.6 to 7.9–8.3 for 1.5 and 3°C of warming, respectively. For the latter case, this indicates previously rare, once‐in‐a‐decade summer extremes will occur almost annually in the future under high warming. [ABSTRACT FROM AUTHOR]

A barrier to urban heat island (UHI) mitigation is the lack of quantitative attribution of the various contributions to UHI intensity. This study demonstrates the daily and seasonal dynamics of UHIs in Hong Kong, a subtropical high‐density city. The nocturnal UHIs of the city are grouped according to various dynamic stability conditions (neutral, weak stable, and strong stable) of the boundary layer. Results indicate that the stronger the atmospheric stability, the more intense the UHI. The atmospheric anomalies linked to these stability classifications are hence revealed. In summer, nights of neutral (strong stable) stratification are controlled by low (high) pressure with rising (sinking) motion, less (more) precipitation, and lower (higher) air temperature at the surface. In winter, the influence of the large‐scale circulation system of the East Asian winter monsoon is significant. In the upper layer, the East Asian jet stream retreats westward (is displaced northward) on nights with neutral (strong stable) atmospheric stratification. At the surface, southeast China is hot and humid on neutral nights, while on strong stable nights, the coastal regions of southeast China are dry, and East Asia is dominated by positive surface air temperature anomalies. Atmospheric anomalies are generally nonsignificant on nights with weak stable stratification in both summer and winter. These findings provide potential predictors for UHI intensity. [ABSTRACT FROM AUTHOR]

Using observations from the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) datasets, the effect of radiative forcing on the development of the stable boundary layer (SBL) and diurnal temperature range (DTR) during summer over the central Heihe River Basin is investigated in this paper. Using a radiative temperature scale based on net longwave radiation (LWnet24), the DTR and the strength of SBL (δTS) are scaled, and the cycle and the year‐to‐year variability before and after scaling are analyzed. The results show that both DTR from air and surface temperatures have a significant correlation with LWnet24, and their correlation coefficients are different over different underlying surfaces. The cycle of DTR from 5‐m air temperature is similar with that of LWnet24. There is only a diurnal cycle in terms of 5‐m air temperature after scaling. Both the trends of the scaled DTR (DTRsc) and the scaled strength of SBL (δTSsc) increase with the growth time of the stable boundary layer (SBL) (τS). The period of τS is similar with that of DTRsc. τS is longer at the oasis site than at the Gobi site, which is related to the oasis effect. In addition, the greater the friction velocity, the smaller the DTRsc and δTSsc. The wind shear enables heat to disperse during SBL. [ABSTRACT FROM AUTHOR]

Surfaces exposed to atmospheric cold temperature and humid environments are prone to ice accretion. Airplanes, electrical power transmission cables, and wind turbines are typical examples for which icing has to be considered. The measurement of the resulting ice shapes is a challenging process. While macroscopic characteristics of the ice geometry can be observed using photography and optical scanning techniques, microscopic measurements are difficult to conduct because grooved surface partially occludes the geometry of chasms. To overcome this optical inaccessibility, we propose a method to carry out detailed high‐resolution measurements of the accretion surface with micro‐computed tomography. This approach provides a unique visualization of the empty spaces in the feather region. The information obtained by this technique can improve the understanding of ice accretion physics and its computational modeling. [ABSTRACT FROM AUTHOR]

We have investigated the effects of land use on past climate change by means of a new 15‐member ensemble of the HadGEM3‐A‐N216 model, usually used for event attribution studies. This ensemble runs from 1960 to 2013, and includes natural external climate forcings with the addition of human land use changes. It supports previously‐existing ensembles, either with only natural forcings, or with all forcings (both anthropogenic and natural, including land use changes), in determining the contribution to the change in risk of extreme events made by land use change. We found a significant difference in near‐surface air temperature trends over land, attributable to the effects of human land use. The main part of the signal derives from a relative cooling in Arctic regions which closely matches that of deforestation. This cooling appears to spread by polar amplification. A similar pattern of change is seen in latent heat flux trend, but significant rainfall change is almost entirely absent. [ABSTRACT FROM AUTHOR]

Observational studies indicated that the East Asian winter monsoon (EAWM) showed significant decadal variations and experienced an interdecadal weakening in the mid‐1980s. How did the EAWM evolve thereafter? In this study, we investigate the decadal variations of the EAWM in the past three decades using five reanalysis datasets and one observational dataset. In total, five members of EAWM system are examined. In the lower troposphere, the Siberian high intensity becomes stronger around 2005 in all five reanalysis datasets, whereas the Aleutian low strengthens in the mid‐1990s and weakens in the mid‐2000s. The two subsystems show opposing changes in the past two decades. In the middle troposphere, the intensity of the East Asian trough remains weakening in recent decades only with some short‐time strengthening around the years of 1995 and 2010. In the upper troposphere, the EAWM index based on the meridional shear of the East Asian jet stream at the 300‐hPa level shows a weak positive trend since the 1990s. It has decadal variations similar to those of the East Asian trough. In the context of these members' changes, the low‐level northerly wind index exhibits two cycles since the year 1980. This index increases in the mid‐1980s, then decreases since the mid‐1990s, and finally increases in the mid‐2000s. Further analysis on the East Asian surface air temperature also reflects similar decadal variations. In summary, unlike the interdecadal shift in the mid‐1980s, the EAWM members (i.e., the Siberian high, the Aleutian low, the low‐level northwesterly wind, the East Asian trough and the East Asian jet stream) do not show consistent decadal variations over the past 30 years. The low‐level members show more significant changes. [ABSTRACT FROM AUTHOR]

The impact of local climate conditions on air temperatures during a hot summer period over the United Kingdom in 2018 is studied using simple sensitivity experiments with a state‐of‐the‐art regional numerical weather prediction system. The experiments are designed to investigate the influence of sea surface temperature (SST) and soil moisture on the air temperatures over land. They involved applying changes to the analysed SST and soil moisture patterns with magnitudes consistent with the differences between forecast analysis and climatology. The results from daily 5‐day forecasts over an 11‐day period show that a 3°C reduction in SSTs reduces the simulated air temperatures averaged over all land points by just over 1°C. Moistening the soil while using the control SSTs reduces the temperatures by a little less than 1°C on average although this can be larger than 3°C locally. While the reduction in SST impacts the daily maximum and minimum temperatures to a similar extent, the increase in soil moisture had little impact on the daily minimum temperatures. [ABSTRACT FROM AUTHOR]

Climate extremes are changing at mid-high latitudes due to the effects of climate change. We defined the duration of surface icing (ice formation on open water) in north China from 1961 to 2015, along with its annual start and end date, based on daily measurements by observers at 346 weather stations. A comprehensive analysis of the temporal and spatial variations in these data showed that the regional mean of annual surface icing duration has a high correlation coefficient of 0.97 with the number of frost days (calculated from the daily minimum temperature below 0 °C), with some discrepancies. As the start date trended later and the end date trended earlier in this region, the surface icing duration decreased by 2.6 days/decade from 1961 to 2015 and the slope became steeper by -4.8 days/decade during the most recent 25 years. These results contribute to a better understanding of changes in climatic extremes related to global climate change. [ABSTRACT FROM AUTHOR]

Improvements in skill of summer forecasted precipitation as produced by the North American multi-model ensemble (NMME) system over the contiguous United States (CONUS) are examined by applying a new bias correction method. The uncorrected precipitation produced by NMME hindcasts exhibits good prediction skill in fall and winter, while the spring and summer forecasts are marked with extremely poor skill. We propose a new method to correct the forecasted precipitation distribution based on skillfully predicted 2-m air temperature (T2m) forecasts to fully exploit the stronger co-variability that exists between precipitation and T2m in nature. The occurrence of enhanced recycled precipitation over CONUS provides an ideal situation to hone precipitation forecast skills using the T2m forecasts. The proposed bias correction is shown to successfully reduce the root mean square error in precipitation hindcasts in summer and can easily be extended to real-time forecasts, thus providing a framework to dynamically link precipitation with other predictors besides T2m. Process understanding of the observed T2m-precipitation relation will offer a framework for diagnosing poor model skill. [ABSTRACT FROM AUTHOR]

We investigated the difference in the fraction of ice (water) cloud bins between eastern and western parts of Eurasia using Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data in January 2007. The fraction of ice cloud bins between −25 and 0 °C was clearly larger in eastern Eurasia than in western Eurasia. A significantly increased (about 20–30%) fraction of ice‐containing clouds is observed in eastern Eurasia in the cloud top temperatures range from −30 to −15 °C. The difference in ice cloud bin fractions between eastern and western Eurasia was remarkable between −20 and −5 °C, being about 20% greater in eastern Eurasia. The fraction of ice cloud bins in the lower troposphere (below 3 km) was larger in eastern Eurasia than in western Eurasia. These results indicate that the ice formation process was more promoted in the lower troposphere in eastern Eurasia than in western Eurasia. This is the first time such results have been obtained from cloud internal structure observations using the CALIPSO active sensor. [ABSTRACT FROM AUTHOR]

Large impacts of global warming and urbanization on near-surface air temperature increase and cooling energy demand are expected for the American Southwest region. The relative importance of these two features and their interactions are studied by means of a mesoscale model with a multilayer building energy model that allows accounting for the feedback between cooling energy consumption and air temperature for a typical summer period in Arizona. This approach allows to separate the impact of global warming from the one due to urbanization, on energy demand and air temperature. Under the highest greenhouse gas emissions scenario (RCP8.5), adverse effects on mean air temperature of global warming overwhelm those from the urbanization of new areas. In particular, the mean temperature increase for a summer period due to global warming and urban expansion in the Phoenix metropolitan area is 3.6 °C and in the Tucson metropolitan area, it is 3.1 °C. These result in an increase in the spatial density of the cooling energy demand (MW km−2) by 36.2 and 42.6% in the respective regions compared to present consumption. The citywide cooling energy demand (MW) on the other hand, is expected to increase up to a factor two (Phoenix) and three (Tucson), with ∼75% of this increase due to urban expansion, and ∼25% due to global warming. [ABSTRACT FROM AUTHOR]

The concentration of aerosols along the Indo-Gangetic Plains (IGP) and their adverse effects on human health and the environment are increasing, particularly in winter, when the IGP is prone to high anthropogenic aerosol loading (i.e. particulate matter - PM). In this study, three reanalysis datasets including the MERRA aerosol reanalysis were analyzed to characterize the relationship between winter atmospheric stability and aerosols. Due to the lack of long-term aerosol observations, an empirical relationship between PM and the atmospheric temperature lapse rate was derived. It is shown that PM and stability have a strong relationship at the lower troposphere. Analyses of Coupled Model Intercomparison Project (CMIP5) single-forcing experiments indicate that the recent stabilization of the atmosphere in the IGP can be explained by both greenhouse gas (GHG) and aerosol forcings. Since a more stable atmosphere traps more PM, stabilization alone can increase aerosols even in the absence of changes in emission sources. Regional simulation with fixed anthropogenic aerosol loading also supports this finding. Thus, enhanced stabilization caused by both aerosols and GHG in the atmosphere can further increase winter aerosol loading in the IGP. [ABSTRACT FROM AUTHOR]

The trends and interannual variations of summer sea ice extents ( SIEs) in both Hudson Bay and the Arctic Ocean are investigated in association with variations in atmospheric circulation and air temperature. The summer SIE variabilities of both Hudson Bay and the Arctic Ocean are well correlated and have a strong negative trend. The negative SIE trends are associated with a summer atmospheric circulation pattern that is characterized by positive anomalies over the Arctic Ocean and negative anomalies over mid-latitudes. The trends are also connected with warm air temperatures over mid- and high-latitudes. The atmospheric circulation and air temperature regressed on the summer SIEs in both Hudson Bay and the Arctic Ocean are quite similar to these trend patterns. On the other hand, the year-to-year variations of the detrended summer SIEs in both Hudson Bay and the Arctic Ocean are not correlated. The summer atmospheric circulation and air temperature over the Arctic Ocean have contributed to the detrended summer Arctic Ocean SIE. In contrast, the detrended summer Hudson Bay SIE is controlled by atmospheric circulation and air temperature in the previous spring. [ABSTRACT FROM AUTHOR]

The microwave temperature sounder (MWTS) on board the third FengYun satellite (FY-3C) is well suited for the detection of tropical cyclones because the observed radiance is insignificantly affected by non-precipitating clouds. In this study, a stepwise multiple linear regression technique is proposed to retrieve the atmospheric temperature profiles based on MWTS measurements. Under clear-sky conditions, the root-mean-square error of retrieved temperature is no >1.4 K, which is low enough to monitor the thermal structure within typhoons. An application of this method to the Super Typhoon Rammasun resolves the warm-core eye and temperature gradients across the eye-wall very well. [ABSTRACT FROM AUTHOR]

We present a comprehensive analysis of temperature-related extreme events in Ny-Ålesund (78.9°N, 11.9°E) using data from three meteorological stations. The results show that annual mean temperatures in Ny-Ålesund increase at a rate that is four times faster than the global mean from 1975 to 2014 with no 'hiatus' in recent decades. The annual diurnal temperature range shows a negative trend as minimum daily temperature increases at a faster rate than maximum daily temperature. A negative trend in cold extremes and a positive trend in warm extremes are observed. This asymmetry hints at potential changes in the probability distribution of temperatures in Ny-Ålesund. [ABSTRACT FROM AUTHOR]

We investigate the time trends in the maximum and minimum temperatures in the United States from 1895 to 2017 using techniques that allow for fractional integration in the detrended series. In doing so we get more accurate estimates of the trends than those obtained using standard methods that impose either stationarity I(0) or nonstationarity I(1). Our results reveal evidence of significant positive trends in both maximum and minimum temperatures, while the difference between them show a significant negative trend as a consequence of the higher increase in the minimum temperatures. Evidence of stationary long memory behavior is also found in the three series examined. [ABSTRACT FROM AUTHOR]

This study quantitatively diagnose the linkage between Total Solar Irradiance ( TSI) and Earth's near-surface air temperature ( TAS) of past 1000-year as simulated by Paleoclimate Modeling Intercomparison Project 3 ( PMIP3) models. The results demonstrate that there is causal feedback of TAS from TSI variations, especially in the tropical and subtropical regions. The consistency between models in simulating solar signal in TAS responses is significant in these regions with more than 70% selected models showing agreement. There is no agreement between models in simulating TSI-TAS relationship in mid and high latitude regions. [ABSTRACT FROM AUTHOR]

This study tests various applications of a new technique for infilling sparse monthly climate data which combines temperature anomalies from gridded observational and reanalysis data sets with baseline climatologies from short-instrumental records. Out-of-sample comparisons between infilled and observed climate data for 53 stations in northeastern Canada suggests that mean absolute errors using the proposed method are ±1 and ±0.5 °C on monthly and annual timescales, respectively. Evaluation of several gridded data sets used to guide infilling suggests that ERA-Interim ( ERAI) and modern-era retrospective reanalysis ( MERRA) reanalyses are the most suitable for this purpose in the Labrador-Ungava region. [ABSTRACT FROM AUTHOR]

Long-term changes in extreme precipitation were studied using data of daily maximum 10-min and hourly precipitation, as well as daily total precipitation for 60 years (1951-2010) in Japan. It was found that extreme 10-min and hourly precipitations, defined from 5-year averages of annual maximum and 95th percentile values, have a high correlation with temperature with a rate of 9.7 ± 4.1% and 8.8 ± 8.3% K−1, respectively. These values are close to the Clausius-Clapeyron ( CC) rate of change in saturation vapor pressure (about 6% per degree), indicating that the CC relation roughly holds for multidecadal changes in extreme short-time precipitation in Japan. [ABSTRACT FROM AUTHOR]

Climate predictions of air temperature in coastal regions represent a great challenge due to the complex interactions among the atmosphere, sea, and land. With approximately 1,200 islands, the Adriatic is a region with a strong land‐sea contrast, land‐atmosphere feedback, and intense air‐sea interaction. Because the Mediterranean has been regarded as a "hot spot" for climate change, regional climate models can be used to provide insight into a more realistic representation of small‐scale weather and climate structure and variability. This advantage is due to the better representation of complex topography, developed coastlines, and land‐sea contrasts, which are important for investigating air temperature trends. The use of regional climate models together with high‐resolution reanalyses and observations in assessments of climate variability and climate change is highly valuable for understanding climate processes at regional scales. The present study focused on air temperature and its trends calculated from measurements and simulated by eight regional climate models from the EURO‐CORDEX database; these data were represented by UERRA reanalyses and E‐OBS gridded data. In the evaluation period (1989–2008), the models' RMSEs were fairly small, in the range 0.5–1.5°C, compared to the historical period (1961–2005), with RMSEs greater than 1.75°C. However, the models showed small absolute trend differences (up to 0.12°C·decade−1 for the historical period). The ensemble means in both periods showed an accuracy improvement of 15–20% compared to the individual models. The models exhibited more success in terms of representing the main statistics and variability of the air temperature structure than in reproducing the temperature trends over 45 years, especially in the northern Adriatic, where there is complex coastal topography and significant seasonal variability in the wind regime. The reanalyses well represented temperature structure but showed less success in explaining the temperature trends than the results from the measured data. [ABSTRACT FROM AUTHOR]

Climate variability, particularly that of the annual air temperature and rainfall, has received a great deal of attention worldwide. The magnitude of the variability or fluctuations of the factors varies according to locations. Hence, examining the spatiotemporal dynamics of meteorological variables in the context of changing climate, particularly in countries where rainfed agriculture is predominant, is vital to assess climate‐induced changes and suggest feasible adaptation strategies. To that end, the present study examines long‐term changes and short‐term fluctuations in monsoonal rainfall and temperature over Kalahandi, Bolangir and Koraput (hereafter KBK) districts in the state of Odisha. Both rainfall and temperature data for period of 1980–2017 were analyzed in this study. Statistical trend analysis techniques namely Mann–Kendall test and Sen's slope estimator were used to examine and analyze the problems. The detailed analysis of the data for 37 years indicate that the annual maximum temperature and annual minimum temperature have shown an increasing trend, whereas the monsoon's maximum and minimum temperatures have shown a decreasing trend. Statistically significant trends are detected for rainfall and also the result is statistically significant at 99% confidence limit during the period of 1980–2017. Rainfall is showing a quite good increasing trend (Sen's slope = 4.034) for JJAS season. In the case of maximum temperature for the observed period, it showed a slight warming or increasing trend (Sen's slope = 0.29) while the minimum temperature trend showed a cooling trend (Sen's slope = −0.006) but result of maximum temperature trend analysis is statistically significant at 95% confidence limit, on the contrary, the trend analysis result of minimum temperature is not statistically significant. [ABSTRACT FROM AUTHOR]

Korean winter temperature exhibits significant year‐to‐year variability, an extreme example of which was the severe cold winter of 2012/2013. Such events can have significant societal and financial impacts. We investigate the seasonal forecast skill for Korean winter temperature using Met Office initialised climate prediction systems. We find significant skill using two independent hindcasts covering the last decades. Observed Korean winter temperature variability appears to be driven by large‐scale dynamical circulation anomalies with centers over the northwest Pacific High (PH) and the Siberian High (SH). While the model has a good simulation of these observed teleconnections, we find that skilfully predicted PH variability dominates the model skill. This is due to the relatively strong PH teleconnection to highly predictable tropical Pacific and Indian Ocean variability. Whereas, observed SH variability is currently much less predictable in seasonal forecast systems. Furthermore, we find that the modelled SH exhibits lower predictability than the observed SH, suggesting a model "signal‐to‐noise" problem over extratropical East Asia which is similar to that reported over northern Europe. We explore one possible pathway, the representation of stratosphere–troposphere coupling, by examining the model simulation of stratospheric sudden warming (SSWs) events. While the SSW frequency and the spatial pattern of surface circulation response appears well simulated, the amplitude of the model response over SH appears anomalously weak. Nevertheless, we conclude that current seasonal forecasts of Korean winter temperature are skilful and have the potential to provide useful climate services. Seasonal prediction of Korean winter temperature and associated circulation. (a) Time series of DJF temperature over Korea in observations (black) and ensemble mean hindcasts from GloSea5 (red) and DePreSys3 (blue). Maps show correlations between the temperature over Korea and mean sea level pressure (MSLP) using observations (b) and ensemble members (c). In (d) we investigate the relationship between observed Korean temperature and the model ensemble mean MSLP predictions. Stippling identifies where correlations are significant at the 90% level according to a two‐tailed t test. The green box shows Korea and black boxes show SH and PH. [ABSTRACT FROM AUTHOR]

Tropical terrestrial ecosystems are the critical driver of the land carbon cycle and climate change. Previous studies have reported strong response in the tropical land carbon cycle to precipitation anomalies in post‐La Niña years. We show that among the post‐La Niña years, 1979 and 1996 stand out strikingly different from other years. 1979 has one of the largest atmospheric CO2 growth rate (CGR) while 1996 has one of the smallest CGR, despite that their annual tropical precipitation anomalies are small. We show that these 2 years correspond to opposite seasonal precipitation anomalies over tropical vegetated lands in the wet‐to‐dry transition seasons in which negative correlation between precipitation and CGR is the strongest. 1979 has large dry anomaly during the transition season, inhibiting land carbon uptake, while 1996 has large wet anomaly during the transition season, favoring more carbon uptake by the tropical ecosystem. Results here highlight the importance of seasonality of climate anomalies and their timing of occurrences with the rhythm of the carbon–climate coupling. Annual atmospheric CO2 growth rate and tropical mean annual temperature and precipitation over vegetated land from 1959 to 2015. Solid dots represent post‐La Niña years. Dots (a, b) represent the years 1979 and 1996, respectively. All the three variables are normalized de‐trended. [ABSTRACT FROM AUTHOR]