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ABSTRACT This study assesses the performance of 28 NASA Earth Exchange Global Daily Downscaled Climate Projections (NEX‐GDDP‐CMIP6) models and their multi‐model ensemble (MME) in simulating mean and extreme precipitation across sub‐Saharan Africa from 1985 to 2014. The Multi‐Source Weighted‐Ensemble Precipitation (MSWEP) and Climate Hazards Group InfraRed Precipitation with Station Data (CHIRPS) are used as reference datasets. Various statistical metrics such as the mean bias (MB), spatial correlation coefficients (SCCs), Taylor skill scores (TSS) and comprehensive ranking index (CRI) are employed to evaluate the performance of NEX‐GDDP‐CMIP6 models at both annual and seasonal scales. Results show that the NEX‐GDDP‐CMIP6 can reproduce the observed annual precipitation cycle in all the subregions, with the model spread within observational uncertainties. The MME also successfully reproduces the spatial distribution of mean precipitation, achieving SCCs and TSSs greater than 0.8 across all subregions. The biases in mean precipitation are consistent across different reference datasets. However, most of the NEX‐GDDP‐CMIP6 models show trends of mean precipitation opposite to observations. While the MME can generally reproduce the spatial distribution of extreme precipitation, its performance varies with the reference dataset, particularly for the number of rainy days (RR1) and maximum consecutive dry days (CDD). TSS values for extreme precipitation indices differ significantly by region, reference data and index, with the lowest values over South Central Africa and the highest over West Southern Africa. The CRI indicates that no single model consistently outperforms others across all subregions, even within the same region, when compared to both MSWEP and CHIRPS. These results may be helpful when using NEX‐GDDP‐CMIP6 models for future projections and impact assessment studies in sub‐Saharan Africa. [ABSTRACT FROM AUTHOR]

Climate change is leading to alterations in the dynamic and thermodynamic climate systems worldwide, including the Indian summer monsoon (ISM), which supports more than a billion population and drives the Indian economy. The anthropogenic climate change induces unprecedented transformations in the natural and ecological systems, such as the increased probability of precipitation extremes, changes in their frequency, duration and spatial variabilities. This current study aims to project the regional landscape‐based metric, velocity of climate change (VoCC) and associated climatic exposure regarding precipitation extremes (PEs) for India and its different biogeographic zones. The climate velocities of mean precipitation, 95th, 99.5th and 99.9th percentiles of precipitation for the ISM season are presented for the historical and three projected time slices under the RCP8.5 scenario. ROM, a state‐of‐the‐art regional earth system model over the CORDEX‐South Asia domain, was used in the study. It was observed that the intense and very intense rainfall (95th, 99.5th and 99.9th percentiles) was enhanced over most of the study region in the near‐ and mid‐future compared to the far‐future. The intense rainfall exhibited higher climate velocity than the mean and very intense precipitation in the near‐future. The southern part of the Indian subcontinent usually displayed positive VoCC values for the historical and near‐future time slices compared to the northern part of the Indian peninsula, particularly the intense and very intense precipitation. The climatic exposure for all‐India was also higher in the near‐ and mid‐future compared to the far‐future, especially for the intense rainfall followed by the mean and very intense rainfall. These results suggest the need for focusing the adaptation and mitigation measures towards managing the near‐term impacts of PEs in relation to the long‐term impacts, especially on the country's diverse flora. [ABSTRACT FROM AUTHOR]

The rise of extreme precipitation events has attracted wide attention throughout the world. However, the analysis of precipitation extremes is not sufficient in the short period of instrumental observation and it is complicated by their non‐stationary behaviours. As a period dominated by natural forcing, the last millennium is helpful for understanding long‐term changes in precipitation extremes. Therefore, this study aimed to (1) investigate changes in daily and subdaily precipitation extremes in China from the last millennium to the end of the twenty‐first century, (2) detect the non‐stationarity of precipitation extremes and (3) compare design storms by using stationary and non‐stationary distributions. The annual maximum 1‐day precipitation (RX1day) and annual maximum 3‐hour precipitation (RX3hour) are used to quantify variations of precipitation extremes. The results show that the trend of RX1day was insignificant for the Medieval Climate Anomaly (MCA, 950–1250) and the Little Ice Age (LIA, 1500–1800). For the historical period (1850–2014), the trend of RX1day and RX3hour was insignificant in most subregions. In addition, the differences for RX1day between the historical period and the MCA/LIA were mostly in the range of −5% to 5%. For the future period (2015–2100), RX1day and RX3hour are projected to increase in almost all land grids compared with the historical period, and they show greater increases in western China than eastern China. The non‐stationarity of RX1day and RX3hour is mainly found under the high‐emission scenario. Moreover, stationary generalized extreme value (GEV) distribution underestimates 50‐year return levels for RX1day and RX3hour in most areas compared with non‐stationary GEV distribution under the high‐emission scenario. Overall, this study suggests that daily and subdaily extreme precipitation will intensify over China in the future. For design storms, non‐stationary methods need to be used for risk management and engineering design under the high‐emission scenario. [ABSTRACT FROM AUTHOR]

Climate change is often described as the average changes in temperature and precipitation; however, it is the change in climate extremes determines the levels of socioeconomic impacts related to climate change. It is generally believed that global warming drives increase in frequency, intensity and duration of precipitation extremes, but these changes vary regionally. Focusing on the relationships between evolution of extreme events and long-term climate change, here we propose a novel classification scheme based on Kӧppen's system and changes in mean and variability of precipitation, divide the global climate into 20 different changing types and reveal the regional evolution of precipitation extremes. We find that precipitation extremes ascend significantly in wetting regions, especially in tropical and temperate zones, independent with changed variability. As for drying regions, the evolution of extremes is related to precipitation variability. An increase of extremes can still be detected in fluctuant-drying areas, while a slight decrease can be seen in stabilized-drying areas. It is surprising to find increase in both wetness and dryness extremes which implies higher intensity of meteorological hazards in densely populated areas. Based on the current and projected growth of population exposure to precipitation extremes, we identify some hotspots with high potential risk in the future.

Precipitation is a meteorological variable that plays a vital role in determining water resources and managing water risks. The intensity and frequency of precipitation extremes have increased in recent years; however, the changes in precipitation regimes across Pakistan remain unclear. This study analysed spatial and temporal changes in the precipitation concentration index (PCI) and concentration index (CI) from 100 meteorological stations across Pakistan from 1981 to 2017. Using innovative trend analysis (ITA) and Pettitt's test, we detected trends and change points in the annual and wet season PCI and CI. Additionally, we examined the relationship between PCI/CI values and latitude and altitude. The results revealed that the CI and PCI ranged between 0.48–0.78 and 10–55, respectively, with higher values being more prevalent in the dry and hot zones of the country. The study established a linear relationship between PCI/CI values, latitude and altitude, with higher values at lower altitudes and a decrease in values from south to north. Most stations presented a significant positive ITA trend for PCI and CI from 1981 to 2017, with a change between 1985 and 1995, indicating an overall increase in heavy precipitation events in the area. These findings are crucial for disaster preparedness, water resource planning, the mitigation of drought and flood risks, and conservation efforts. [ABSTRACT FROM AUTHOR]

A regional earth system model (ROM) was used to examine the projected change in the precipitation extremes (PEs) and associated dynamical and thermodynamical processes over India during the Indian summer monsoon (ISM). In this regard, PEs are computed for India, its six homogeneous regions and subregions the Western Ghats (WG) and central India (CI). The changes are computed for mid‐future (2040–2069: MDF) and far‐future (2070–2099: FRF) with respect to the historical period (1969–2000). ROM showed better resemblance with observation in simulating PEs over other regional climate models (RCMs) that participated in the CORDEX‐CORE simulation. The intense rainfall (95th percentile: R95) is expected to be enhanced over most of the region during MDF that further intensifies in FRF except CNE (central northeast) and NEI (northeast India), where the increase in R95 was restricted only up to MDF. Interestingly, very intense rainfall (99.9th percentile: R99) showed robust increases in both MDF and FRF for all regions. Additionally, long wet (dry) events were shortened (lengthen). Moreover, the short wet and dry spell frequency has increased, while the duration of the wet (dry) spell has decreased (increased) in both time slices over India with noticeable regional variation. This is attributed to the strong cyclonic circulation, reduced vertical wind shear and enhanced moisture transport during the ISM in both time slices. It is very important to highlight the substantial changes in the precipitation extremes to have better planning and strategies that will be helpful to minimize the incurred losses. [ABSTRACT FROM AUTHOR]

The relationship between boreal summer intraseasonal oscillation (BSISO) and precipitation extremes over Indonesia is investigated using observational datasets from 30 years (1987–2016) of rain gauge measurements and the gridded Asian Precipitation‐Highly Resolved Observational Data Integration Towards Evaluation of Water Resources from 1998 to 2015. The results indicate that the frequency of daily extreme precipitation events in Indonesia (defined as total precipitation above the 95th percentile) during extended boreal summer (May–August) is significantly modulated by BSISO, especially over the western and northern regions. Under the influences of BSISO1, the probability of the precipitation extremes over Sumatra and Borneo increases by 20–120% (relative to the seasonal probability) during phases 1–3 and approximately 50–80% over the eastern part of Borneo and Sulawesi during phase 4. Under BSISO2, the probability of the extremes increases up to 40% over Sumatra during phases 1 and 2 and up to 140% over Borneo and Sulawesi during phases 2 and 3. The increase in the probability of extreme summer precipitation is associated with enhanced large‐scale moisture flux convergence and upward moisture transport induced by the active phases of BSISO. These results provide potential information for medium‐ to extended‐range predictions of summer precipitation extremes in Indonesia. [ABSTRACT FROM AUTHOR]

The Regional Atmospheric Modelling System (RAMS) driven by data from the CMIP5 Earth System Model HadGEM2‐ES was used to simulate daily precipitation over the tropical Americas for both current and future climate, including distinct scenarios (representative concentration pathways 4.5 and 8.5) and different time horizons (short‐term, mid‐term and long‐term changes). The major objective was to evaluate possible future changes in extreme events, with emphasis on the intensity of precipitation events and the duration of wet and dry spells. According to RAMS, longer dry spells are expected over most regions of the tropical Americas in the future, with indications for Northeast Brazil, Caribbean, Northern Amazon, and shorter wet spells over Central America and Amazon. With the exception of the Caribbean, there is a general tendency towards the increased frequency of intense precipitation in the tropical Americas. [ABSTRACT FROM AUTHOR]

Precipitation extremes present significant risks to Midwest agriculture, water resources, and natural ecosystems. Recently, there is growing attention to the transitions of precipitation extremes, or shifts between heavy precipitation and drought, due to their profound environmental and socio‐economic impacts. Changes in Midwest precipitation extremes and transitions between extremes over the past few decades have been documented; however, their future changes are still unknown. In this study, we estimate the projected changes in transitions of precipitation extremes in the Midwest based on 17 CMIP6 models. Two Standardized Precipitation Index (SPI) based metrics, intra‐annual variability and transitions, are used to quantify the magnitude, duration, and frequency of variability and transitions between wet and dry extremes. Compared with the observation‐based precipitation datasets, the multimodel ensemble median of CMIP6 can reasonably represent the spatial patterns of SPI extremes and transitions. Climate projections show significantly intensified wet extremes across the Midwest by the end of the century, with a greater increase over the northern Midwest and the Great Lakes region. The short‐term SPI also shows intensified dry extremes over the western half of the Midwest. Consequently, there is a significant increase in the magnitude of intra‐annual variability in most areas. Projections also suggest more frequent and rapid transitions between the wet and dry extremes, especially over the Great Lakes region and northern Midwest. Seasonally, more frequent transitions from a wet spring to a dry summer (or from a dry fall to a wet winter/spring) are projected to occur; and generally, the wet and dry conditions between the transitions are projected to be more intense compared to the historical period. Furthermore, the intensified precipitation extremes and accelerated transitions are greatly alleviated under a lower emission scenario, implying that future changes in hydroclimate extremes, and impacts thereof, in the Midwest are sensitive to climate change mitigation. [ABSTRACT FROM AUTHOR]

Although climatologically dry, the western slopes of the southern Andes of Peru (WSA) can experience precipitation extremes (PEs) during the summer (December–February) resulting in great economic and human losses. Generally, WSA has a positive upslope gradient in precipitation, meaning more rain falls at higher elevations, but observations have shown this gradient can become negative with higher rainfall near the coastal cities. In this study we analyse 2000–2019 regional atmospheric patterns associated with different upslope precipitation gradients and PEs in WSA using principal component analysis methods and surface station observations. Results show important changes in the atmospheric circulation patterns during the occurrence of PE events. A prevailing pattern of negative southerly wind anomalies and regional warming of the southeastern Pacific Ocean leads to significant increases in moisture along the coast of WSA. Eastern moisture flows associated with the presence of the Bolivian High are observed at upper levels of the atmosphere and transport water vapour from the Amazon to the western side of the Andes. Additionally, there is a blocking effect aloft in response to an intense gradient of geopotential height that attenuates the easterly circulations. These large‐scale mechanisms act to concentrate high precipitable water amounts and high levels of convective available potential energy in the troposphere which favours the vertical velocities essential to trigger PEs. These results increase our knowledge of the large‐scale characteristics of PEs to help with forecasting these impactful events and protecting the more than 1.8 million people living in WSA. [ABSTRACT FROM AUTHOR]

The rise of global surface temperature due to warming climate is expected to increase the intensity and occurrence of extreme precipitation events. Previous studies in Southeast Asia revealed complex variations in changes of precipitation extremes. This study presents a spatial–temporal analysis on changes of precipitation extremes in Peninsular Malaysia by utilizing long‐term daily rainfall records at 64 observed stations during 1989–2018. The modified Mann–Kendall and Sen's slope tests were performed to detect the significance and magnitude of trends in eight extreme precipitation indices recommended by the Expert Team on Climate Change Detection and Indices. Statistically significant increasing trends are observed for four of these extreme indices in the annual assessment. Spatial analysis demonstrates an obvious contrast between wet and dry regions in patterns of precipitation extremes. Seasonal analysis reveals the intensity and frequency of wet extremes are enhanced significantly during the northeast monsoon season. Significant correlations are found between precipitation extremes and El Niño–Southern Oscillation, particularly in the northern, eastern and southwest regions. Collectively, the evidence presented suggests that the occurrence of precipitation extremes in Peninsular Malaysia tends to be more frequent and intense over the year and is closely associated with the combined effects of tropical monsoon cycles and El Niño–Southern Oscillation. [ABSTRACT FROM AUTHOR]

Central Asia faces an increasing challenge related to water resources arising from severe droughts and floods that have impacted the region in the past decades. Using a comprehensive set of extreme precipitation indices, we assess the performance of CMIP6 models in representing observed precipitation extremes and investigate future responses of these extremes to greenhouse gas emissions under four shared socioeconomic pathways (SSP). Particularly, this study identifies robust signals of projected changes in spring and summer precipitation extremes over central Asia. Results show that the CMIP6 models reasonably reproduced the spatial distribution and variability of precipitation extremes over southern central Asia (SCA) and northern central Asia (NCA) during the spring and summer seasons, respectively. Across the SSPs, the CMIP6 models project a decrease in total spring wet‐day precipitation amount (PRCPTOT) over SCA and a significant increase in PRCPTOT over the NCA. The projected changes are characterized by a significant increase in maximum consecutive 5‐day precipitation (RX5day), wet‐day intensity (SDII), and the number of heavy precipitation days (R10mm); these suggest that the spring will be characterized by intense precipitation extremes. Moreover, no significant change is projected for consecutive wet days (CWD) and dry spells (CDD) over SCA. Nonetheless, the CMIP6 models project a significant increase in summer PRCPTOT over SCA and a decrease in summer PRCPTOT, RX5day, R10mm, SDII, and CWD over NCA while projecting a significant and robust increase in dry spells. It is also found that the severity of the projected dry spell deepens across the SSP spectra and gets more pronounced towards the end of the 21st century. Notably, the intermodel spread of the precipitation extremes is smaller during the spring over SCA, larger during the summer season over NCA, and more probable in the warmer future. [ABSTRACT FROM AUTHOR]

The precipitation is classified into tropical cyclone (TC)‐induced precipitation and others, that is, non‐TC precipitation in the Asian continent and the western North Pacific. Traditional frequency analysis for the precipitation, which is a mixture series of annual maximum precipitation generated by TC and non‐TC, does not consider the difference in the generation mechanism with the assumption of independently and identically distributed. To reveal the effect of different generation mechanisms on the frequency analysis of the extreme precipitation, a multiplicative mixture frequency analysis (MMFA) model is adopted to study the interaction of non‐TC maximum precipitation (NTCMP) and TC maximum precipitation (TCMP) to the total precipitation frequency. Applying the NTCMP and TCMP data in Fujian Province located in southeast China, the results indicated that (a) the inconsistencies between NTCMP and TCMP are common, and different inconsistent patterns existed in space; (b) Different characteristics of inconsistency between the two types of precipitation had distinct effect on the estimation results of MMFA model, especially for the high return levels; and (c) The estimation results of MMFA model were demonstrated to be more secure and reliable. Therefore, the MMFA model is a suitable approach to solve the problem of mixture precipitation frequency caused by two generation mechanisms of non‐TC and TC. [ABSTRACT FROM AUTHOR]

This study examines the potential implications of 1.5, 2.0, and 3.0°C global warming levels (GWLs) on the austral summer (November–March) extreme precipitation indices over the Zambezi River basin (ZRB) relative to the control period (1971–2000). We computed extreme precipitation based on daily data from observations and the Coordinated Regional Downscaling Experiment (CORDEX)‐Coordinated Output for Regional Evaluations (CORE) multi‐model ensemble mean (ENSMean). First, we evaluated the performance of the CORDEX‐CORE ENSMean in simulating extreme precipitation based on six indices; the number of rainy days (RR1), simple daily intensity index (SDII), maximum consecutive wet days (CWD), maximum consecutive dry days (CDD), heavy precipitation days (R10), and very heavy precipitation days (R20). The results indicate that the CORDEX‐CORE ENSMean can simulate the spatial distributions of extreme precipitation over the ZRB. However, CORDEX‐CORE largely overestimates the magnitudes of RR1 and CWD. The projected changes show a decrease in RR1, CWD, and R10 under all GWLs, with a robust and pronounced decrease under 3.0°C GWL. In contrast, CDD and SDII are projected to increase under all GWLs, with a robust and pronounced increase in CDD under 3.0°C GWL. The regionally averaged changes show that the median values of CWD, RR1, and R10 (SDII and CDD) are projected to decrease (increase) under all GWLs over the ZRB and sub‐basins. The probability density function (PDF) shows negative (positive) shifts in the mean of CWD, RR1, and R10 (SDII and CDD) over the ZRB and sub‐basins under all GWLs. In contrast, R20 is projected to increase (decrease) over most of the western (eastern) ZRB under all GWLs. Assessing the implications of an additional 0.5 and 1.5°C (1.0°C) warming to 1.5°C (2.0°C) GWL shows that limiting GWL to 1.5°C would restrict the future exposure of the ZRB to extreme precipitation. [ABSTRACT FROM AUTHOR]

Knowledge of long‐term changes in climate extremes is vital to better understand climate variability and place present day extreme events in historical context. Analysis of trends in extreme precipitation in Ireland have largely been limited to the second half of the 20th century due to lack of data availability in digital format. Using recently digitized data, this study provides the first assessment of long‐term changes in extreme daily precipitation observed at 30 locations across Ireland. Quality control of rescued data is carried out before selected long‐term stations are tested for homogeneity using the RHtests software. Details of detected breakpoints and the application of adjustments to daily values are discussed. Eleven extreme precipitation indices are calculated on an annual basis and analysed to determine spatial and temporal trends in the frequency, intensity and magnitude of observed precipitation. The persistence of trends for varying record lengths and for two fixed periods (1910–2019 and 1940–2019) of analysis is assessed for all stations and indices. Results show increases in precipitation intensity, especially notable in the east and southeast of the island. Our findings also show that the contribution of heavy and extreme precipitation events to annual totals is increasing, while there was no persistent trends in annual totals or consecutive wet or dry days. [ABSTRACT FROM AUTHOR]

Performance of six models in the Coupled Model Intercomparison Project phase 5 (CMIP5) and their new versions in CMIP phase 6 (CMIP6) in representing the climatological (1976–2005) precipitation extremes over China were evaluated based on five precipitation indices. Improvements are found in CMIP6 models in simulating the climatology of all five indices, in which GFDL‐CM4 and GFDL‐ESM4 show significant improvement. Dry biases over South China (SC) are reduced in five CMIP6 models (BCC‐CSM, CanESM, GFDL‐CM, GFDL‐ESM, and IPSL‐CM), with the largest decreased root‐mean‐square error (RMSE) of 59.2% in GFDL‐CM. The reduced dry biases in CMIP6 can be attributed to more moisture transported into SC from the southern boundary and dynamic processes of the atmosphere except in BCC‐CSM, where the increased evaporation dominates. Additionally, increased heavy precipitation events (>20 mm·day−1) are produced over SC in CMIP6 models. Wet biases over West China (WC) are also reduced. with the largest reduced RMSE of 46.8% in GFDL‐CM, which are related to the reduced precipitation frequency (more than 40%) and weakened precipitation intensity. In addition, the CMIP6 models show a higher skill in simulating the frequency distribution of daily precipitation intensity. More heavy precipitation over SC and Northeast China, and fewer weak precipitation (<20 mm·day−1) over WC can be reasonably reproduced. Although the CMIP6 models have obviously improved in simulating total precipitation on wet days, wet days (WD), simple daily intensity index (SDII), and extreme precipitation amount (R95T), the bias still exists in simulating consecutive dry days (CDD). [ABSTRACT FROM AUTHOR]

This work examines the changes in precipitation characteristics over the Indian region using the latest high‐resolution CORDEX‐CORE model simulations. Individual RCM (COSMO, RegCM4.7, and REMO) experiments, their ensembles, and all RCM ensembles are examined to evaluate their performance using various statistical metrics. It aims to provide a holistic idea for choosing better models for specific analysis (variability, climatology, temporal evolution, indices, etc.) of precipitation distribution over India. The COSMO model experiments show lesser mean bias and have a high correlation coefficient (>0.8) compared to REMO and RegCM4. Each RCM ensemble performs better than its members in representing the spatial patterns of precipitation. Interestingly, the RCM experiments downscaling the forcings from MPI_ESM GCMs and ERA‐Interim outperforms other RCM experiments in the present day period. The probability distribution function reflects that the mean frequency and the intensity of precipitation are best represented in the RegCM4 ensemble. Further, most RCMs agree to a robust increase in low‐intensity rainfall (>0.1–4 mm⋅day‑1) in the future under the RCP8.5 scenario. The intraseasonal variability in terms of active and break spells are best represented in the RegCM4 ensemble. There exists uncertainty in terms of projection of active phases, while all model experiments agree to the decrease in the break phases in the near future compared to the present day. The projected consecutive dry (wet) days and their spells will decrease (increase) over India. The heavy precipitation events are expected to increase (by 18–32 days) along with its contribution (by 14–48%) towards the total precipitation over entire India indicating a possible increase in flooding events in the future. The present‐day ISM characteristics is well captured in the model ensemble compared to individual experiments. The model ensemble indicates towards a robust increase in low‐intensity rainfall in the future. The very heavy precipitation events and its contribution towards total precipitation are increasing in the future. [ABSTRACT FROM AUTHOR]

Precipitation regimes have been predicted to shift to more extreme patterns that are characterized by heavy rainfall events and longer dry intervals. Spatiotemporal variation of precipitation extremes may significantly influence the local ecosystem, especially in the arid and semi‐arid regions. This study investigated the variations in extreme precipitation indices across the arid and semi‐arid land of China from 1960 to 2018. Spatial autocorrelation analysis was also conducted to evaluate spatial autocorrelations within the study area. There was generally an increasing trend of precipitation intensity, however, most stations in the low‐altitude semi‐arid regions showed non‐significant trend. The frequency indices generally showed a decreasing trend in consecutive dry days, and an increasing trend in precipitation days in the arid land and high‐altitude semi‐arid regions, suggesting that the arid and high‐altitude semi‐arid regions are becoming wetter. Signals of decreasing precipitation intensity and frequency were still found, such as increasing trends in consecutive dry days in the stations from the low‐altitude semi‐arid regions, implying the possibility of increased drought risk at small spatial scale. The global Moran's I values indicated that the spatial autocorrelation of the trend in the low‐altitude semi‐arid region is high. The local Moran's I showed that the number of stations with wetting trend in the arid region were much higher than that in the semi‐arid regions. These observations imply that the precipitation extremes in the arid and semi‐arid regions of China are becoming more homogeneous. Hence, this study can serve as a useful reference to the policymakers and stakeholders for framing water resource and ecosystem management strategies in arid regions. [ABSTRACT FROM AUTHOR]

Autumn rainfall in West China, the last rainy season of China, exerts profound impacts on the economic society, therefore, researches on its changes in the context of a warmer world are crucial for better adaptation to climate change. Using the dynamical downscaling performed by the regional climate model RegCM4 from four global climate models, this study firstly evaluated the fidelity of the RegCM4 simulations on the mean and extreme aspects of autumn rainfall in West China, and then projected their changes during the middle and the end of the 21st century under the RCP4.5 scenario. The evaluations indicate a good performance of the RegCM4 downscaling simulations in reproducing the observed spatial distribution of autumn rainfall amount, wet days, maximum consecutive 5‐day precipitation (RX5day), total extremely wet‐day precipitation (R95p), and consecutive dry days (CDD). Under the RCP4.5 scenario, relative to 1986–2005, the amount of autumn rainfall and the frequency of wet days are projected to increase in the northwestern part of West China and to decrease in its southeastern flank, concurrent with greater changes by the end of the 21st century than by the middle of the 21st century. Such an increase is closely associated with the enhancement of zonal water vapour transport and atmospheric unstable stratification, while the projected decrease is largely related to the reduction of moisture supply. Similar changes are also projected for the precipitation extremes Rx5day and R95p. Corresponding to the changing pattern of autumn rainfall, the CDD is projected to decrease in the northwestern part and to increase in the southeastern part of West China. [ABSTRACT FROM AUTHOR]

Daily precipitation data from 21 Chinese Surface Stations for Global Exchange in South China and historical tracks of tropical cyclones (TCs) from International Best Track Archive for Climate Stewardship (IBTrACS) during 1955–2013 are analysed to study changes in extreme precipitation and TC‐related precipitation with respect to global mean temperature. On annual and seasonal bases, there have been significant enhancements in heavy precipitation and suppressions of light and moderate precipitation under global warming conditions. Except in winter, the enhancements in heavy precipitation dominate over the suppressions of light and moderate precipitation, leading to increases of seasonal total precipitation. A significant increase of consecutive dry‐day episodes has been observed, especially in winter and early spring, which is detrimental to spring planting. The top 10% heavy precipitation associated with TCs has increased significantly under global warming conditions, despite a reduction in TC frequency. Finally, we find that TC‐related precipitation per TC storm in South China has increased by an alarming rate of about 50% during the period of 1955–2013. Under global warming conditions, significant enhancements in heavy precipitation and suppressions of light and moderate precipitation, which is controlled by long‐term trend, have been observed on both annual and seasonal bases in South China during 1955–2013. With reduction of light and moderate precipitation, consecutive dry‐day episodes increase significantly, especially in winter and early spring. Although the frequency of tropical cyclones (TCs) has a substantial downward trend, the top 10% heavy precipitation associated with TCs increased significantly. [ABSTRACT FROM AUTHOR]

Non‐stationarities within the predictor–predictand relationships can substantially affect model skill of statistical downscaling approaches. For this reason, an approach is presented which takes varying predictor–predictand relationships explicitly into account. Seasonal aggregated daily precipitation extremes (90th, 95th and 99th quantiles) were assessed by means of 31‐year running contiguous calibration periods. Here, when the end of the time series was reached years from the beginning were attached. Thus, a regression model ensemble (RME) becomes available, with the number of established statistical models corresponding to the number of years within the time series. With respect to non‐stationarities in the projection periods, a novel approach is presented. A single model of the RME is determined for each sub‐period which seems to be the most suitable model (MSM) for assessing precipitation extremes within the respective period. In order to define the MSM weighted correlations of atmospheric circulation composites, represented by the geopotential heights, between reanalysis and model runs were calculated for all significant predictors. The reanalysis period which exhibits the highest mean correlation coefficient is then considered for the projections of the respective period of the model runs. Subsequently, a second selection process was performed in order to determine whether the regression model (RM) established within this period or the model with the highest skill within this period is used for assessing future precipitation extremes. Results have shown that projections can significantly differ depending on whether a non‐stationary or a stationary downscaling setup is used for the assessments. Non‐stationarities occur within the predictor–predictand relationships and affect model skill in the scope of statistical downscaling. In order to improve assessments, a novel circulation‐based approach is introduced to determine the most suitable model for estimating daily precipitation extremes in the Mediterranean area. Although the direction of the future trends is usually the same, the results of the non‐stationary approach can significantly differ from a stationary model setup. [ABSTRACT FROM AUTHOR]

Mean and extreme northwest Australian (NWA) summertime rainfall has increased significantly since 1950. While previous studies have explored a range of possible factors impacting NWA rainfall, the causes of this increase and possible future changes remain uncertain. This study explores the increasing NWA summertime rainfall trends in Coupled Model Intercomparison Project phase 5 (CMIP5) models. By using a suite of models that contributed realizations of the historical period with various forcings, we explore the impact to this region of greenhouse gases and aerosol emissions since 1950 on mean rainfall and three extreme rainfall indices. The observed NWA rainfall trend is better captured in models when all forcings are included compared to simulations with only greenhouse gas forcing or with only natural forcing, although the models have a large spread. We hypothesise that anthropogenic aerosols played a major role in the observed rainfall trends, and the associated increase in monsoonal flow, and hence historicalNat and historicalGHG simulations tend not to capture observed rainfall trend. Throughout the 21st century, CMIP5 models simulate a stronger increase in mean summer precipitation and extreme indices of NWA rainfall in representative concentration pathway (RCP) 8.5 simulations than in RCP2.6. The NWA region shows intensified extreme events with fewer heavy precipitation days, but the reliability of these projections in this region should be further tested with estimates of future anthropogenic aerosol changes. Mean and extreme northwest Australian (NWA) summertime rainfall has increased significantly since 1950. The figure shows spatial trend of summer (DJF) wind at 850 hPa (m s−1 year−1) over the period 1950–2005 in (a) NCEP, (b) historical ensemble mean, (c) historicalAA ensemble mean, (d) historicalGHG ensemble mean in CMIP5 models. We hypothesise that the rainfall increase over NWA can be related to increased monsoonal flow due to increased aerosol emissions in last 56 years. [ABSTRACT FROM AUTHOR]

Cold fronts are the most frequent synoptic systems that affect Southeast Brazil during the whole year. The highest frequency of these systems at these latitudes occurs in the months of spring (SON) and winter (JJA), but the highest associated precipitation occurs in the spring (SON) and summer (DJF). Some of these fronts present light rains but others cause heavy precipitation, giving rise to flooding and landslides, mainly in the summer. Composites of the two cases (light and heavy rainfall) are analysed for the summer season. Large‐scale and regional features are shown to discuss the differences in precipitation. Regional differences are seen in the position and intensity of low pressure and postfrontal high. The differences are also associated with the humidity flux and convergence over the region. The main difference at high levels is the position of the frontal trough, which is close to the region in the wet cases and displaced to the ocean in the dry cases. Features of the Southern Annular Mode and Madden–Julian Oscillation show opposite patterns in the two cases. These modes of variability can modulate extra‐tropical wave trains over the Pacific, which have different behaviour downstream, over South America and South Atlantic Ocean. The eddy kinetic energy is stronger over Southeastern Pacific and Southern South America, and wave activity shows energy propagation towards the continent in the wet cases. Similar analyses with results of a global atmospheric model show that the general atmospheric characteristics of a frontal system are reproduced, as the temperature gradient, the wind confluence and the ridge‐trough pair associated with the frontal system. The model represents the differences with respect to moisture flux and the frontal trough position, but underestimates the moisture convergence, eddy kinetic energy and wave activity, in the wet cases. Composites of cases classified with percentiles of 5 and 95% (dry and wet) are analysed. Regional differences between them are seen in the humidity flux and convergence over the region and in the position and intensity of pressure at sea level. Differences in extra‐tropical wave trains and kinetic energy over the Pacific affect the position and intensity of the frontal trough at high levels. The Center of Weather Forecasting and Climate Studies/National Institute for Space Research Atmospheric Global Circulation Model reproduces the general characteristics of a frontal system, but underestimates the moisture flux and kinetic energy. [ABSTRACT FROM AUTHOR]

Extreme precipitation and associated flooding cause severe damage to society and the environment. Future climate projections suggest an intensification of precipitation extremes in many regions. However, there is an increasing need for climate change impact assessment at higher spatial resolution, particularly for regions with complex geography such as Southeast Asia (SEA). In this study, we analysed the NASA Earth Exchange 0.25° resolution daily precipitation projections from an ensemble of 20 climate models under two emission scenarios RCP4.5 and RCP8.5. The variability in future precipitation projections is analysed and quantified for six geographical subregions, two climatological regions (wet and dry), and the low‐elevation coastal zones in SEA. Various aspects of precipitation structure are studied using indices that characterize precipitation amount, number of heavy precipitation days, extreme precipitation amount, and maximum daily precipitation at annual and seasonal scales. The results show substantial increases in mean and extreme precipitation in many parts of SEA by the end of the 21st century under both emission scenarios, thus increasing the region's vulnerability to precipitation‐driven hazards. The projected centennial increase in total annual precipitation relative to the baseline period of 1970–1999 when averaged over all land grid cells is about 15% under RCP8.5 scenario, with larger values (∼20%) over mainland SEA and Philippines and smaller values (∼6%) in Java island. The projected changes in extreme precipitation are stronger compared to the total annual precipitation under both emission scenarios. The New Guinea and Java regions show the largest and smallest increases in annual maximum daily precipitation, with ensemble mean values of 30 and 17%, respectively, under RCP8.5 scenario. The results also reveal large inter‐model spread in projected changes, particularly during boreal winter and summer months. The study assessed changes in different precipitation characteristics such as the annual maximum daily rainfall (shown here) over nine regional masks in Southeast Asia for the time period 2070–2099 relative to the baseline period of 1970–1999. Results indicate substantial changes in total precipitation and extreme precipitation, particularly for the RCP8.5 scenario. The regional and seasonal variability in future changes and associated uncertainties are described in detail in this study. [ABSTRACT FROM AUTHOR]

This study is to investigate changes in maximum 24‐hr precipitation for 20 stations during the typhoon season (July–October) and how the El Niño–Southern Oscillation (ENSO) may modulate precipitation extremes in Taiwan. Based on the nonparametric Mann–Kendall method and Sens's test, 15 out of 20 stations (three fourth) exhibited an upward trend from 1958 to 2013. Results of the field significance test suggest that the significant increasing trend is not caused by random variability. The method of the non‐stationary generalized extreme value distribution (NGEV) is then applied to determine temporal changes in return levels. Results show that a large majority of stations are marked by an increasing trend in the three chosen return levels (2, 20, and 100 years) over the last 56 years. Therefore, more intense typhoon producing seasonal maximum 24‐hr precipitation has been observed in Taiwan. The waiting time for an extreme event to occur has shortened considerably in recent years. For stations located in western/central Taiwan, an El Niño (La Niña) event favours low (high) precipitation extremes. It is the opposite for stations in northern and eastern Taiwan. Thus, an east–west regional difference in precipitation extremes across Taiwan is noted. A NGEV model based on both time and ENSO as covariates is also applied. Inter‐annual variations influenced by ENSO are more dominant than long‐term trend in return levels for most stations in western/central Taiwan. Historical 24‐hr maximum precipitation during the typhoon season (July–October) is used and a majority of stations in Taiwan are marked by an increasing trend in the three chosen return levels (2, 20, and 100 years) over the last 56 years. An east–west regional difference in precipitation extremes across Taiwan is noted based on the antecedent state of ENSO. Inter‐annual variations influenced by ENSO are more dominant than long‐term trend in return levels for most stations in western/central Taiwan. [ABSTRACT FROM AUTHOR]

In this study, by using the Weather Research and Forecasting (WRF) model, the impact of spectral nudging (SN) on simulating the precipitation extremes and diurnal cycle of precipitation over Coordinated Regional Climate Downscaling Experiment‐East Asia (CORDEX‐EA) domain is evaluated. The simulations are conducted during 1989–2007 driven by the ERA‐Interim reanalysis data with different SN experiments. It is clear that WRF has the ability to reproduce the long‐term climatology as well as the extremes over Asia, while biases are generated in the experiment without SN (NOSN). The simulations with SN, especially SN6 (SN with wavenumber 6) and SN3‐UVT (SN with wavenumber 3 applied to wind and temperature), can efficiently improve the model's skill by reducing the biases of precipitation frequency and intensity as well as the extreme indices except for the consecutive dry days (CDD). The diurnal harmonics of precipitation frequency and amount are well produced by WRF, and the SN experiments also perform better than the NOSN experiment, with SN3‐UVT showing the best skill. However, the SN only with winds shows little improvement in simulating the diurnal cycles, and the additional nudging of temperature can improve the simulation only over south China and Indo‐China. It can be concluded that the strength of nudging parameters can significantly affect the simulation of precipitation, with better performance under the stronger nudging. Moreover, additional nudging of temperature can also improve the simulation. The impact of spectral nudging on simulating the precipitation extremes and diurnal cycle of precipitation over CORDEX‐EA domain is evaluated using WRF. WRF has the ability to reproduce the long‐term climatology as well as the extremes over Asia, while biases are generated in the NOSN experiment. The SN simulations produce better the precipitation extremes and diurnal harmonics. Better simulation of precipitation is performed under the stronger nudging, and additional nudging of temperature can also improve the simulation. [ABSTRACT FROM AUTHOR]

There are two aims of this paper: First, the relationship between daily and hourly precipitation extremes and air temperature is investigated for the validity of Clausius–Clapeyron (C–C) scaling; second, the impact of the atmospheric circulation and transport of humidity on the extreme precipitation events occurrence in Poland is analysed based on data obtained from 26 stations across Poland in the period 1951–2015. It was shown that daily‐scale extreme rainfall is less sensitive to changes in local atmospheric temperature but the hourly intensities reveal a similar behaviour at all stations showing a robust signal over the entire country. Regarding the impact of the large‐scale atmospheric circulation, three types were distinguished in cool part of the year: one connected with the positive phase of the North Atlantic Oscillation (NAO), second with a low‐pressure zone in the north and high‐pressure in the south of Europe and the northern Atlantic and third with a low over central Europe. Each time high precipitation in Poland was connected with the advection of humid air from the western sectors (SW, W or NW). In the warm part of the year three types were distinguished too, Poland was always in the scope of low‐pressure systems with the advection of warm air from the southern sectors or when the warm air from the south meets the colder air from the north. Similar localizations of low centres have been found in the case of local‐scale atmospheric circulation types during events with extreme precipitation. Both in cool and warm part of the year such events are connected with the increase of water vapour in the air. In cool season the wet and warm air masses inflow to Poland the most often from Atlantic, in the warm season—from Mediterranean and/or Black Seas. [ABSTRACT FROM AUTHOR]

ABSTRACT: Regional climate models (RCMs) from the North American Regional Climate Change Assessment Program (NARCCAP) are compared with the two gridded precipitation data sets [Climate Prediction Center (CPC) and the University of Washington (UW)] and the North American regional reanalysis (NARR) to examine if RCMs are able to reproduce very heavy precipitation under similar physical conditions seen in observations. The analysis focuses on contemporary climate (1982–1999) in an upper Mississippi region during the summer (June–July–August) months and utilizes output from NARCCAP RCMs forced with a reanalysis and atmosphere–ocean global climate models (AOGCMs). The NARCCAP models generally reproduce the precipitation frequency versus intensity spectrum seen in observations up to around 25 mm day−1, before producing overly strong precipitation at high intensities. CRCM simulations produce lower precipitation amounts than the rest of the models and observations past the 25 mm day−1 threshold. Further analysis focuses on precipitation events exceeding the 99.5th percentile that occur simultaneously at several points in the region, yielding ‘widespread events’. Apart from the CRCM and EPC2 simulations, models and observations produce peaks in widespread events during 0300–0900 UTC, although the models typically produce slightly weaker intensities compared to observations. Widespread precipitation falls too frequently throughout the day, especially between 1500 and 2100 UTC, compared to observations. Composite precipitation shows inter‐model differences in magnitude and location of widespread events. Examination of additional fields shows that NARCCAP models produce credible representations of very heavy precipitation and their supporting environments when compared to the NARR. [ABSTRACT FROM AUTHOR]

ABSTRACT: Using daily output from 29 climate models provided by the Coupled Model Intercomparison Project Phase 5, we project signals in 12 extreme temperature indices and 12 extreme precipitation indices relative to 1986–2005 over China associated with a 2 °C global warming above pre‐industrial levels under representative concentration pathways 4.5 (RCP4.5) and 8.5 (RCP8.5). The model output reflects the following projected changes: (1) It is robust and statistically significant that warm extremes are more frequent, more persistent, and more intense than those during the baseline period of 1986–2005, and local signals emerge from natural internal variability over most of China. In particular, southern China faces severe heat stress in summer based on warm extreme indices. (2) It is robust and statistically significant that there are fewer cold extremes in China. Most models show no significant changes in the longest duration and intensity of most cold extremes in southern China and northwest China. (3) The multi‐model median shows that more frequent and more intense wet extremes that deliver greater amounts of extreme precipitation occur in China, with a regional mean increase of 16.7–42.8 mm (8–42%) in total amount of annual wet extremes, but these changes are not significant and do not exceed natural internal variability over most of the country. Spatially, the Tibetan Plateau and northeast China have robust and significant changes in part of precipitation extremes, and some changes begin to emerge from natural internal variability at local scale. There are benefits to limiting global warming for China, including less frequent and less persistent warm extremes when comparing 1.5 °C with 2 °C of global warming and a later occurrence of significant changes in climate extremes when compared an intermediate mitigation scenario RCP4.5 with a high emission scenario RCP8.5. [ABSTRACT FROM AUTHOR]

ABSTRACT: In the context of global warming, urban areas are more vulnerable to extreme weather conditions. In this study, four key temperature and precipitation extreme indices, defined by the Expert Team on Climate Change Detection and Indices, are selected to investigate implications of differential effects of 1.5 and 2 °C global warming on extreme weather in China's urban agglomerations (CNUAs). Results indicate that bias‐corrected extreme indices derived from downscaled data sets of National Aeronautics and Space Administration (NASA) Earth Exchange Global Daily Downscaled Projections (NEX‐GDDP) of 19 Coupled Model Intercomparison Project Phase 5 (CMIP5) models under RCP4.5 scenario [representative concentration pathways (RCP)] can be used to study the effects of global warming on extreme indices in locations of CNUAs. An increase in the global warming from 1.5 to 2 °C is likely to exacerbate the intensity of extreme maximum temperature (TXx) and decrease extreme minimum temperature (TNn) in CNUAs. Moreover, additional 0.5 °C warming is more likely than not to increase the intensity of total precipitation of very wet days (R95) and maximum 5‐day precipitation (Rx5day). For the very extreme events (>1.5σ), a global warming increase from 1.5 to 2 °C will lead to extra increase in extreme risk for very extreme TXx, R95p and Rx5day by 4.1, 1.8 and 1.0 times, relative to 1986–2005. Thus, it seems that reducing the 2 °C global warming level by 0.5 °C during the remainder of the 21st century would significantly suppress very extreme heat waves and very extreme wet events in CNUAs. Certainly, the urban heat island and aerosol effects are expected to further enhance such extreme events in the urban areas. The combined influence of global warming and urbanization effects on extreme events needs further study in the future. [ABSTRACT FROM AUTHOR]

This study investigates the El Niño-Southern Oscillation (ENSO)-related seasonal variations in precipitation extremes based on the observed daily precipitation dataset of 23 meteorological stations in Malaysia, spanning a period of 46 years from 1966 to 2011. The extreme indices were a subset of the Expert Team for Climate Change Detection and Indices (ETCCDI) that covers the duration, frequency and intensity aspects of precipitation extremes. Seasonal composites of 'El Niño minus neutral' and 'La Niña minus neutral' years of these indices were computed based on El Niño and La Niña occurrences during the period. The results showed that the ENSO-related variations in precipitation extremes were generally coherent with the variations in total precipitation. Generally, dry (wet) precipitation extremes tended to enhance during El Niño (La Niña); however, this was dependent on season and location. The El Niño and La Niña influences on precipitation extremes were not entirely linear. While the impacts of El Niño and La Niña were generally opposite for most locations and seasons, there were cases where both exerted in-phase influences. The impacts were also dependent on the intensity of the event itself. While the El Niño impacts were generally coherent across different intensities, La Niña can have entirely different impacts among different categories. During December–January–February (DJF), strong (moderate) La Niña caused a significant decrease (increase) in wet precipitation extremes over the Peninsular Malaysia. This was related to the broadening (narrowing and westward displacement) of the anomalous cyclonic circulation over the western north Pacific during strong (moderate) La Niña. Hence, the likelihood for widespread flooding over the east coast of the Peninsular Malaysia during DJF increases during moderate but not during strong La Niña events. [ABSTRACT FROM AUTHOR]

ABSTRACT Owing to their essential influence on human society and natural environment exerted by inducing disasters, such as floods and droughts, further studies on precipitation extremes in China are needed. This study presents the regional frequency and spatial-temporal patterns of precipitation extremes in China based on a high-resolution (0.5° × 0.5°) daily precipitation dataset from 1961 to 2013. With fuzzy c-means, L-moments methods and other scientific statistical tests, a regional frequency analysis ( RFA) is conducted, aiming to further understand the regional and spatial distribution of precipitation extremes across China. The results show that: (1) the whole Mainland China can be divided into 50 homogeneous regions on the basis of the characteristics of mean annual precipitation and location indices. (2) For most of the regions, Generalized Extreme Value ( GEV), Generalized Normal ( GNO) and Pearson type III ( PE3) distributions of precipitation extremes fit well, according to the results of goodness-of-fit ( GOF) test. (3) For RX1DAY, GEV has the best-fit distribution in the east, northeast and southwest of China, whereas GNO distribution mostly fits the northern and parts of southwest and southeast; in addition, regions which fit PE3 and Generalized Logistic ( GLO) distribute dispersedly across the country. (4) For RX5DAY, GEV mainly fits in the middle, southwestern and southern; GNO and PE3 apply best to the northeastern and northern, respectively. (5) Return periods of 20, 50 and 100 years for their best-fit distributions decrease gradually from southeastern China to northwestern China. Compared with the results of GEV distribution fitted to each grid, RFA may provide more accurate estimates of rainfall quantiles. Definitely, the study results will not only benefit further understanding of the unique and complex features of extreme precipitation in the whole Mainland China but also contribute to the nation-scale flood prevention, control and management in the backdrop of the changing climate. [ABSTRACT FROM AUTHOR]

ABSTRACT Trends and variability of extreme precipitation events are important for water-related disaster prevention and mitigation as well as water resource management. Using daily precipitation dataset from 143 meteorological stations in the Yangtze River Basin ( YRB), a suite of heavy and extreme precipitation indices recommended by the Expert Team on Climate Change Detection and Indices, which has rarely been applied in this region, were analysed during 1960-2012. Results showed that simple daily intensity index, very wet day precipitation, extremely wet day precipitation, extremely heavy precipitation days, maximum 1-day precipitation, maximum 5-day precipitation and maximum consecutive dry days all increased significantly during 1960-2012. In contrast, ≥10 mm precipitation days and maximum consecutive wet days decreased significantly, implying that the precipitation processes in YRB were dominated by precipitation events with shorter durations. Geographically, a wetting tendency was observed in the eastern Tibet Plateau and the middle and lower YRB, while the other regions experienced precipitation deficits. The increasing precipitation was mainly due to the intensification of extreme precipitation events and the decreasing precipitation may be attributed to the decrease of ≥10 mm precipitation days or moderate precipitation events. In addition, the regional trends were of greater magnitudes in the middle and lower YRB, indicating more frequent extreme precipitation events in these sub-regions. Time series analysis revealed that most precipitation indices exhibited neither a stable nor a gradual pattern during 1960-2012, but a clearly upward trend, although non-monotonous, since the late-1980s was evident. [ABSTRACT FROM AUTHOR]

ABSTRACT Spatiotemporal variations of extreme precipitation regimes are both caused by the climate change and the natural climate variability. The trends of extreme precipitation indices as an issue of climate change and the possible teleconnection with the ocean-atmospheric modes as an issue of natural climatic variability have been analysed in China. Ten extreme precipitation indices have been used in this study, and the station-based extreme precipitation indices were gridded into 1°latitude × 1°longitude using the angular distance weighting method. For extreme precipitation, an index is more likely influenced by the local topography if it represents the more extreme precipitation and then the regional response of this index to climate changes is more complex. Results of the trends of extreme precipitation indices indicated that three zones can be generally identified in China, namely: (1) a significant drying tendency can be confirmed along the strip stretching in the northeast and southwest direction; (2) northwest China is dominated by a wetting tendency and slight increase of precipitation intensity; and (3) southeast China exhibits a slight wetting tendency but significant intensifying precipitation. The wetting tendency in northwest China may be caused by increasing precipitation during November, December, January, and February. Besides, the teleconnections between precipitation extremes and El Niño-Southern Oscillation ( ENSO), North Atlantic Oscillation ( NAO), Indian Ocean Dipole ( IOD), and Pacific Decadal Oscillation ( PDO) were also analyzed, and results showed that the regional responses of precipitation extremes to ENSO, IOD, NAO, and PDO varied for the climate indices at different stages, such as the precipitation extremes generally tend to be decreasing in the central part of China at the same year of positive ENSO while increasing in the east part of China a year after the positive ENSO. This study provides insights into regional response of weather extremes to global climate indices in China, and these are valuable for developing measures to mitigate the hazards due to weather extremes. [ABSTRACT FROM AUTHOR]

ABSTRACT Extremes of weather and climate can cause disasters such as floods and droughts. Further studies of precipitation extremes are crucial for enabling reliable projections of future changes. In this study, we used a high-resolution (0.5° × 0.5°) gridded precipitation data set to analyse these events across the 11 basins in China between 1961 and 2013 mainly by the Mann-Kendall and generalized extreme value methods. Our results indicated a wetter trend in the Tarim River Basin ( TRB) but drier conditions in the central Yangtze River Basin ( YRB), western Pearl River Basin and eastern Yarlung Tsangpo River Basin. There was an increasing risk of flooding in the mid-lower YRB and Minjiang River Basin ( MRB), and an increasing risk of drought in the central Lantsang River Basin. The results revealed strengthened maximum 1-day precipitation ( RX1DAY) in the Liaohe River Basin ( LB), YRB, MRB and TRB, together with strengthened maximum 5-day precipitation ( RX5DAY) in the Songhua River Basin, MRB and TRB during 1987-2013. RX1DAY and RX5DAY for return periods of 20 and 50 years gradually decreased from southeast to northwest. Along the south-eastern coastline of the Mainland and on Hainan Island, the RX1DAY for the 20- and 50-year return periods would exceed 165 and 195 mm, respectively, whereas the RX5DAY would exceed 270 and 320 mm for the same return periods. Furthermore, summer Southern Oscillation Index ( SOI) positively impacted precipitation extremes in the Yellow River Basin and YRB, and autumn SOI negatively impacted the extremes of the next year in LB and YRB, while winter SOI negatively impacted the extremes of the next year in YRB. Additionally, the East Asia summer monsoon ( EASM) and the South Asia summer monsoon ( SASM) were both associated with precipitation extremes across China; however, EASM contributed more to these events than did the SASM. [ABSTRACT FROM AUTHOR]

ABSTRACT The goal of this article is twofold: first, changes in the spring and summer thermodynamic instability over the North Atlantic European region and the connection with frequency of rain showers at 81 locations across Romania for the period 1961-2010 are analysed; second, the relationship between hourly precipitation extremes and air temperature with respect to the validity of Clausius-Clapeyron ( CC) scaling is investigated. The Best Lifted Index (lftx4) has been selected to quantify the thermodynamic instability. The mechanisms responsible for the rain showers' variability in Romania were analysed using the canonical correlation analysis ( CCA). Results show that the regional distribution of the lftx4 changes is quite similar in the two seasons, with a transition towards thermodynamic stability over most of Mediterranean regions - central Europe and instability in northern Europe, Black Sea, North Atlantic (summer), southern North Atlantic (spring). The frequency of rain showers in Romania exhibits a significant increasing trend in both seasons, which is in agreement with the increase in frequency of Cumulonimbus clouds. In contrast, the frequency of rainfall days does not exhibit any significant trend that shows a shift in the nature of precipitation towards more showers. The CCA shows that the optimum large-scale mechanisms responsible for this behaviour are given by the first CCA pair with the lftx4 pattern represented by a dipole structure with a nucleus of thermodynamic instability centred over Romania. The dynamic factor is an additional ingredient for spring, as precipitable water is for summer. The extreme hourly rainfall intensities reveal a similar behaviour over the entire country: the 90th percentile shows dependence close to the CC relation for all temperatures; the 99th and 99.9th percentiles exhibit rates close to double the CC rate for temperatures between ∼10 and ∼22 °C and negative scaling rates for higher temperatures. The daily intensities have a less clearly defined scaling behaviour. [ABSTRACT FROM AUTHOR]

ABSTRACT Based on the high-resolution gridding data ( CN05) from 2416 station observations, a grid dataset of temperature and precipitation extreme indices with the resolution of 0.5° × 0.5° for China region was developed using the approach recommended by the Expert Team on Climate Change Detection and Indices. This article comprehensively presents temporal and spatial changes of these indices for the time period 1961-2010. Results showed widespread significant changes in temperature extremes consistent with warming, for instance, decreases in cold extremes and increases in warm extremes over China. The warming in the coldest day and night is larger than the warmest day and night, respectively, which is concurrent with the coldest night larger than the coldest day and the warmest night larger than the warmest day. Changes in the number of the cold and warm nights are more remarkable than the cold and warm days. Changes in precipitation extremes are, in general, spatially more complex and exhibit a less widespread spatial coverage than the temperature indices, for instance, the patterns of annual total precipitation amount, average daily precipitation rate, and the proportion of heavy precipitation in total annual precipitation are similar with negative trends in a southwest-northeast belt from Southwest China to Northeast China while positive trends in eastern China and northwestern China. The consistency of changes in climate extremes from the CN05 with other datasets based on the stations and reanalyses is also analysed. [ABSTRACT FROM AUTHOR]

ABSTRACT Land and water management in semi-arid regions requires detailed information on precipitation distribution, including extremes, and changes therein. Such information is often lacking. This paper describes statistics of mean and extreme precipitation in a unique data set from the Mount Kenya region, encompassing around 50 stations with at least 30 years of data. We describe the data set, including quality control procedures and statistical break detection. Trends in mean precipitation and extreme indices calculated from these data for individual rainy seasons are compared with corresponding trends in reanalysis products. From 1979 to 2011, mean precipitation decreased at 75% of the stations during the 'long rains' (March to May) and increased at 70% of the stations during the 'short rains' (October to December). Corresponding trends are found in the number of heavy precipitation days, and maximum of consecutive 5-day precipitation. Conversely, an increase in consecutive dry days within both main rainy seasons is found. However, trends are only statistically significant in very few cases. Reanalysis data sets agree with observations with respect to interannual variability, while correlations are considerably lower for monthly deviations (ratios) from the mean annual cycle. While some products well reproduce the rainfall climatology and some the spatial trend pattern, no product reproduces both. [ABSTRACT FROM AUTHOR]

ABSTRACT While researchers have identified teleconnections between El Niño-Southern Oscillation ( ENSO) and extended winter precipitation extremes in North America using generalized extreme value ( GEV) models, the regional form of the statistical relationship remains an open question. Past work has shown that relatively warm ENSO conditions may be needed to trigger a nonlinear response over North America. However, studies that stratify winters into La Niña, neutral, and El Niño phases have found that precipitation extremes in neutral/La Niña winters respond differently than in El Niño winters, whereas studies that stratify ENSO data into cold/warm conditions have not found evidence for a coherent nonlinear response. Data and methodological differences have made direct comparison between results difficult. In this study, evidence for a nonlinear association between ENSO and precipitation extremes is reassessed by fitting stationary and linear/nonlinear GEV regression models, with the Niño3.4 index as a covariate, to 1-, 5-, and 10-day extended winter precipitation maxima. Two types of nonlinear model - both one-sided GEV regressions where linear relationships are allowed to differ above/below a Niño3.4 index threshold - are considered. In the first, following past work, the breakpoint is fixed at zero, that is stratifying data into warm/cold conditions. In the second, to see whether there is evidence for a differential neutral/La Niña and El Niño response, the breakpoint is allowed to vary freely. Due to the non-nested nature of the set of models, the Akaike Information Criterion is used to assess the relative support for each model. Depending on accumulation time-scale, the strength of evidence favours nonlinear models at 28%-30% of stations when the Niño3.4 breakpoint is free to vary, versus just 3% with a fixed breakpoint. Optimum Niño3.4 breakpoints are positive (> +0.4°C) in the majority of the nonlinear models, confirming that ENSO/precipitation relationships differs between La Niña/neutral and El Niño winters. [ABSTRACT FROM AUTHOR]

ABSTRACT The impact of soil initialization is investigated through perturbation simulations with the regional climate model Consortium for Small-scale Modelling (COSMO) and the Climate Limited-area Modelling ( COSMO-CLM). The focus of the investigation is to assess the sensitivity of simulated extreme periods, dry and wet, to soil moisture initialization in different climatic regions over Europe and to establish the necessary spin-up time within the framework of decadal predictions for these regions. Sensitivity experiments consisted of a reference simulation from 1968 to 1999 and five simulations from 1972 to 1983. The Effective Drought Index ( EDI) is used to select and quantify drought status in the reference run to establish the simulation time period for the sensitivity experiments. Different soil initialization procedures are investigated. The sensitivity of the decadal predictions to soil moisture initial conditions is investigated through the analysis of water cycle components' ( WCC) variability. In an episodic timescale, the local effects of soil moisture on the boundary layer and the propagated effects on the large-scale dynamics are analysed. The results show: (1) COSMO-CLM reproduces the observed features of the drought index. (2) Soil moisture initialization exerts a relevant impact on WCC, e.g. precipitation distribution and intensity. (3) Regional characteristics strongly impact the response of the WCC. Precipitation and evapotranspiration deviations are larger for humid regions. (4) The initial soil conditions (wet/dry), the regional characteristics (humid/dry) and the annual period (wet/dry) play a key role in the time that soil needs to restore quasi-equilibrium and the impact on the atmospheric conditions. Humid areas, and for all regions, a humid initialization, exhibit shorter spin-up times, also soil reacts more sensitive when initialized during dry periods. (5) The initial soil perturbation may markedly modify atmospheric pressure field, wind circulation systems and atmospheric water vapour distribution affecting atmospheric stability conditions, thus modifying precipitation intensity and distribution even several years after the initialization. [ABSTRACT FROM AUTHOR]

ABSTRACT Changes in precipitation extremes for the Basilicata region, southern Italy, have been analyzed using data from 55 precipitation stations with complete daily time series during the period 1951-2010. All the series were submitted to quality control assessment and homogenization. To detect possible trends the time series analysis was performed with the Mann-Kendall non-parametric test. The annual and seasonal total precipitation underwent a general downward trend over the period 1951-2010 mainly due to the autumn-winter decrease of precipitation, although the tendency for the last decade is clearly positive. The precipitation intensity shows a general positive trend, mainly due to the upward trend of spring. The dry spell mean has increased throughout the region over 1951-2010, even if a really important opposite trend characterizes the last decade. The wet spell mean has decreased throughout the region from 1951 to 2010, although a strong inversion of tendency has been recorded in the last 10 years. Trends in the extreme daily precipitation have indicated a general downward tendency, mainly during the summer season. The analysis of multi-day sequences of moderate to heavy rainfall has indicated a corresponding increase in their frequency and intensity, especially in the last decade. The overall results indicate a present hydroclimatic regime characterized by an increase in total rainfall and precipitation intensity and a small decrease in dry spell lengths. The positive change in precipitation magnitude is due to multi-day extreme precipitation rather than to single-day precipitation. This last observation is very important for its huge hydrological impact on the environment. In Basilicata, the increase in intensity/frequency of multi-days extreme events has led to the growth of severe flooding and landsliding events, not only in autumn and winter, but even in the early spring. [ABSTRACT FROM AUTHOR]

ABSTRACT Significant trends in precipitation extremes over Europe since the middle of the 20th century have been found in earlier studies. Most of these studies are based on descriptive indices of moderate extremes that occur on average a few times per year. Here we have analyzed rarer precipitation events which occur on average once in 5, 10 and 20 years in the 1950s and 1960s using extreme value theory. We have focused on the 1-d and 5-d precipitation amounts in Northern and Southern Europe in all four seasons. Changes over the time period 1951-2010 are studied by considering five consecutive 20-year time intervals with 10-year overlap. Despite considerable decadal variability, our results indicate that 5-, 10- and 20-year events of 1-d and 5-d precipitation for the first 20-year period generally became more common during this 60-year period. For all regions, seasons and return periods, the median reduction in return period between the first and last 20-year periods is ∼21% with variations between a decrease of ∼2% and ∼58%. [ABSTRACT FROM AUTHOR]

Daily precipitation data from 590 stations in China covering a period of 1960-2005 are analysed using copulas, the modified Mann-Kendall (MK) trend test and linear regression. Changing characteristics of eight precipitation indices are investigated in both time and space. Results indicate that (1) the regions west of 100°E, particularly northwest China, exhibit a wetting tendency as reflected by increasing/decreasing number of consecutive rain/non-rain days; (2) the drying tendency is observed mainly in the regions covered by the Yellow River basin, the Huaihe River basin, and the Haihe River basin, and relatively moderate changes in precipitation indices are found in northeast China; (3) precipitation extremes are intensifying in the regions east of 100°E, particularly in case of south China, specifically the lower Yangtze River basin, the southeast rivers and the Pearl River basin. The intensification of precipitation extremes in south China is mirrored mainly by the decreasing number of rain days and increasing number of consecutive non-rain days. Besides an increasing percentage of P90 to the annual total precipitation, (4) the intensification of precipitation extremes has the potential to increase the probability of occurrence of natural hazards, particularly floods and droughts. The spatial distribution of flood- and drought-affected crop areas is in agreement with that of precipitation extremes, showing considerable impacts of precipitation extremes on meteor-hydrological hazards. An increasing number of consecutive non-rain days in south China will cause a higher risk of droughts. The regions east of 100°E are heavily populated and are economically developed. Food security, water security, and sustainable socioeconomy in China urgently call for effective water resource management policy. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The historical daily precipitation observations for the Netherlands were fully digitized recently. The homogeneity of the precipitation series was tested by pairwise comparisons of the monthly totals using an algorithm of Menne and Williams. Forty percent of the precipitation series was indicated as inhomogeneous if the algorithm was applied to the untransformed monthly totals. The use of a square-root transformation to reduce the skewness was only successful in an application to the data for the 1951-2009 period. Changes in the annual precipitation amounts, the precipitation amounts in the winter and summer halves of the year, the number of days per year with a precipitation amount greater than 20 or 30 mm, and the 5-d annual maximum precipitation amount were determined both for the period 1951-2009 using the data from 240 stations and the period 1910-2009 with the data from 102 stations. Significant increases were found for all six indices. The centennial increases in mean annual, winter and summer precipitation are 25, 35, and 16%, respectively. The exceedance frequency of the 30 mm threshold almost doubled during the 1910-2009 period. Much attention is given to the field significance of trends, the statistical significance of regional differences in trends and nonlinearity of trends. In contrast to the increase in mean winter precipitation, which is statistically significant for the majority of the stations, the increase in mean summer precipitation is mainly restricted to coastal regions. The mean summer precipitation and the exceedance frequencies of the 20 and 30 mm thresholds show a relatively strong increase from the beginning of the 1980s. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Aiming at better understanding the causes and processes leading to meteorological dry and wet episodes in western Iran, the present study investigates the space and time variability of winter dry/wet events and their associated large-scale atmospheric driving circulations. Using monthly precipitation data of 140 weather stations for 1965-2000, meteorological dry/wet spells are assessed through the 1-month Standardized Precipitation Index (SPI). By applying the Principal Component Analysis (PCA) with Varimax rotation to the SPI field, three sub-regions of independent climatic variability are identified. Large-scale daily atmospheric circulation patterns are then classified into twelve circulation types (CTs) by applying PCA to the 500 hPa geopotential height fields coupled with the non-iterative K-means clustering technique, in which extreme rotated principal component scores, in their positive and negative phases, are considered as potential groups and their centroids are computed by averaging all days that fulfil the extreme score criterion. The linkage between daily CTs and winter dry/wet spells in the region is investigated by correlating the frequencies of occurrence of each CT with the time series of dry/wet events, derived from both the rotated principal component scores of SPI and the SPI series at three representative stations of the identified sub-regions. Severe/extreme events have also been considered. A performance index is applied to test the relationship between CTs and dry/wet events. Results show statistically significant correlations between the frequencies of occurrence of the identified CTs and of dry/wet spells at the three representative stations, suggesting that particular CTs are potential predictors for the winter dry/wet events in western Iran. Copyright © 2011 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Several approaches to estimating distributions of precipitation extremes are compared by means of simulation experiments, and their applications into observed data in the Czech Republic are evaluated. Regional frequency models, which take into account data in fixed or flexible 'regions' when fitting a distribution at any site, lead to estimates with much smaller errors compared to a single-site analysis, and efficiently reduce random and climatologically irrelevant variations in the estimates of the model parameters and high quantiles. The region-of-influence (ROI) methodology with a built-in regional homogeneity test is recognized as a useful approach, with the model based on proximity of sites outperforming the Hosking-Wallis regional frequency analysis. Comparison of estimates of the return period of a heavy precipitation event on 24 June 2009, which triggered a disastrous local flash flood, illustrates that the at-site analysis leads to unrealistic and extremely uncertain estimates that strongly depend on whether or not a single outlying observation is involved in the sample, while all regional methods yield return periods in the same order of several hundreds of years, notwithstanding whether the 2009 data are included in the sample. The ROI method may be found useful for modelling probabilities of other meteorological variables, extremes of which are strongly influenced by sampling variability, and may also represent an efficient tool for 'smoothing' random variations in the estimates of model parameters and high quantiles of precipitation in high-resolution regional climate model simulations. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The article presents a study on the spatial and temporal dynamics of the extreme precipitation patterns in southern Portugal. It states that two extreme precipitation indices to observe the daily precipitation patterns such as the presentation of extremely heavy precipitation events (R30) and the characterization of dry events (RL19) occurrence. Results reveal that the extreme precipitation events' spatial continuity has increased in the country since 1970 while spatial variability decreases.

The article presents a study which investigates trends in multiple characteristics of precipitation extremes over Czech Republic. It notes the use of a high-quality dataset of daily measurements from rain-gauge stations provided by the Czech Hydrometeorological Institute (CHMI). It offers insights on the emerging global picture of prevailing positive trends in heavy precipitation during winter over the mid-latitudinal land areas of the Northern Hemisphere.