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ABSTRACT: The estimated future changes of precipitation and precipitation‐related climate indices for the Carpathian Region are analysed in this paper. Eleven regional climate model (RCM) simulations from the ENSEMBLES project taking into account the intermediate A1B emission scenario are used, hence, the analysis also includes uncertainty assessments. Validation results showed that in the target area RCM simulations overestimate precipitation throughout the year, except in summer, when underestimation occurs. In order to eliminate these systematic errors before the detailed analysis, percentile‐based bias correction is applied to the raw RCM outputs, for which the high‐quality CARPATCLIM database (1961–2010) serves as a reference. Using the bias‐corrected RCM simulations, precipitation totals and several precipitation‐related indices (describing both wet and dry climatic conditions) are calculated for the 1961–2100 time period on seasonal scale for the entire Carpathian Region, and also for five subregions (Slovakia, Ukraine, Hungary, Romania, and Serbia) within this area. The results from RCM simulations are inconsistent for some indices in some seasons, thus introducing uncertainties to the climatic projections. However, according to our results, drier summers are very likely to occur in the future, mainly in the southern parts of the selected domain. More frequent and more intense extreme precipitation events are estimated for winter and autumn, especially in the northern regions. Our conclusions suggest that the spatial distribution of precipitation is not likely to change remarkably in the future, however, the annual distribution of precipitation is projected to be restructured. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper presents an analysis of winter climate variability based on daily mean temperature and precipitation data since 1970 in the Chic-Chocs Mountain range (located in the Gaspé Peninsula, Eastern Quebec, Canada). Mountain environments are particularly sensitive to rapid climate change and are therefore good indicators of recent global warming. The main goal of this study is to demonstrate how joint probability temperature/precipitation distributions can be used to estimate winter condition changes (trends) for six meteorological stations in the study area (the altitudinal range for the stations is from 5 to 574 m). The presence and persistence of snow cover was also estimated. Previous studies have shown a lack of evidence of significant trends in snow-cover characteristics (density, depth and snow water equivalent (SWE)) from the early 1980s to the present, despite an increase in temperature over the same period. A reanalysis of these data sets in addition to the use of a combination of temperature and precipitation data categorized into four modes (warm/wet, warm/dry, cold/wet and cold/dry) was also performed. Despite this new analysis, no clear evidence of climate change could be found in the study area over the last four decades. The results revealed that patterns and trends are quite different from one station to another, but when the environment is taken into account (valley or plateau, coastal versus inland) some apparent patterns emerge. [ABSTRACT FROM AUTHOR]

The homogenization of climate observational series is a needed process before undertaking confidently any study of their internal variability, since changes in the observation methods or in the surroundings of the observatories, for instance, can introduce biases in the data of the same order of magnitude than the underlying climate variations and trends. Many methods have been proposed in the past to remove the unwanted perturbations from the climatic series, and some of them have been implemented in software packages freely available on the Internet. The Spanish project MULTITEST was intended to test their performance in an automatic way with synthetic monthly series of air temperature and atmospheric precipitation, to update inter‐comparison results from former projects, especially those of the COST Action ES0601. Several networks representing different climates and station densities were used to test a variety of homogenization packages on hundreds of random samples. Results were evaluated mainly in the form of root mean squared errors and errors in the trend of the series, showing that ACMANT, followed by Climatol, minimized these errors. However, other packages performed also relatively well, even outperforming them when there were simultaneous biases of the same sign in most or all the test series. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper analyses the influence of different types of El Niño-Southern Oscillation ( ENSO) events on South American precipitation under a climate change scenario. We use two sub-selections of Coupled Model Intercomparison Project Phase 5 (CMIP5) models that have a good representation of teleconnections to the region, albeit with reduced magnitude anomalies. Comparing historical simulations and the RCP 8.5 scenario experiments, after removing the trend in the mean due climate change, the sub-ensemble means show similar global sea surface temperature anomalies and South American precipitation anomaly patterns in the future. No robust changes in the pattern or magnitude of precipitation anomalies are found, despite significant ENSO-related shifts in the Pacific basin, as highlighted in other studies. However, if the models are analysed individually, some show relatively strong changes in ENSO-related precipitation anomalies for both canonical and Modoki events. We show that, in individual models, tropical teleconnection changes associated with ENSO are primarily driven by changes in the magnitude of ENSO-related circulation but with no agreement on the sign. Increases in background moisture, which have been hypothesized to drive an intensification of ENSO-related precipitation anomalies, are of secondary importance. [ABSTRACT FROM AUTHOR]

Results from the multiple‐realization, single‐model ensemble called "d4PDF" were used to generate hydroclimate indices for present and future climates over the Indochina region. The model performed reasonably well in capturing the reference precipitation characteristics of the present climate (1951–2010), in particular the seasonal pattern (e.g., JJA and SON) and intensity‐based indices such as SDII, R95p, Rx1D, and Rx3D. Under the +4 K future simulation conditions for 2051–2110, comprising six prescribed sea‐surface temperature scenarios, substantial and statistically significant increases in precipitation frequency (R10 and R20) and intensity (SDII, Rx1D, and Rx3D) were projected over the Indochinese Peninsula with a high degree of consistency. However, there were greater uncertainties in the changes significance of mean precipitation either during early dry‐season (DJF) or late monsoon (SON) indices demonstrated by results of the parametric U test in some river catchments, such as the Chao Phraya, Red River, central Mekong, lower Irrawaddy, and Salween Basins, where the projection consistencies in a positive change direction were less than 50%. Comparison of basin‐wide empirical probability distributions of precipitation indices pointed to a robust increase in the frequency of the occurrence of heavy precipitation in intensity indices (e.g., Rx1D, Rx3D, and SDII). The relationship between d4PDF precipitation and total runoff generation outputs from the land surface component was investigated. The results show a high degree of temporal correspondence across the region under the present climate in several seasonal and intensity indices, except during the dry period (DJF and MAM). Finally, we found that εP(P, R) of the annual and seasonal climatological indices of the future climate were always positive and larger than unity, with a median εP(P, R) of 1.28–2.04. The results strongly reaffirm the role of rainfall as the main driver of runoff changes due to its faster response relative to change in precipitation at the Indochina Region. [ABSTRACT FROM AUTHOR]

This study examines the 1950–2017 temporal changes in climate extremes in Israel, which is located in the East Mediterranean (EM), a region which suffers from a scarcity of long and reliable datasets. It is well known that most long‐term records are affected by artificial shifts most commonly caused by station relocation, instrumental modification and local environmental changes. Therefore, for the first time, a thorough homogenization (detection and correction) routine was developed and implemented in the long‐term records. Consequently, a new daily adjusted dataset has been generated, including 34 temperature stations and 60 precipitation stations. Based on this comprehensive dataset, 38 extreme indices recommended by the Expert Team on Climate Change Detection and the Expert Team on Sector‐specific Climate Indices have been calculated. These indices will help various sectors to plan properly mitigation actions and adaptation for climate change, in addition to facilitating future studies for the EM. The results showed highly significant changes in temperature extremes associated with warming, especially for those indices derived from the daily minimum temperature (TN, 1950–2017), whereas the maximum temperature (TX) exhibited a similar increasing magnitude of the TN (~0.55°C/decade) in the last 30 years. The warming trends, which are non‐monotonic, seem to have been particularly strong since the early 1990s. The coastal area is characterized by higher heat stress during the nighttime, while mountains exhibit a strong tendency towards increasing temperatures during the noon hours. A reduction in the total precipitation amount and in the number of wet days with a tendency towards more intense wet days was found. Although all the regional trends of the precipitation indices were not statistically significant (p ≤.05), they showed a fine spatial coherence. [ABSTRACT FROM AUTHOR]

Projections of climate change impacts over Europe are derived using a new quantile–quantile adjustment method. E‐OBS high‐resolution gridded data sets of daily observed precipitation and 2‐m surface minimum and maximum temperatures have been used as the current climate baseline. For projections, the same meteorological variables have been obtained from a set of regional climate models (RCMs) integrated in the EURO‐CORDEX project, and by considering the RCP4.5 and RCP8.5 future emissions scenarios. To enhance the reliability of RCM data at local scale, new developments of a previous quantile–quantile adjustment have been applied to the simulated regional scenarios. This method focuses not only on the bulk spectrum of the cumulative distribution functions but also on its tails. Results show an overall improvement in reproducing the present climate baseline when using calibrated series instead of raw RCM outputs. Next, we have used these locally adjusted series to quantify the climate change signal through a number of annual and seasonal indicators. A significant increase of the minimum and maximum temperatures in all seasons is projected over Europe, being more marked in the Mediterranean for summer and autumn. Prospects on future seasonal and annual changes in precipitation are more diverse, showing an overall decrease in southern Europe and the Mediterranean, while precipitation is expected to increase towards the north of the continent. With these sources of information at hand, including and accounting for the identification of the most vulnerable geographical areas, policy makers and stakeholders can respond more effectively to the future challenges imposed by climate change. [ABSTRACT FROM AUTHOR]

The Mackenzie River basin (MRB), which covers a geographic region from central Alberta of Canada to the coast of Arctic Ocean, has an area of approximately 1.8 × 106 km2. In this study, the regional climate of MRB, in particular the precipitation and air temperature from the late spring to the fall (May–October), was simulated using a regional climate model Weather Research and Forecasting (WRF). In the open water season of May–October, Mackenzie River provides a critical corridor for Canada's Arctic transportation network. With nine sets of physical parameterizations of WRF selected, we simulated the climate of MRB over representative dry, normal, and wet years to identify the best setting prior to performing the 27‐year simulation for 1979–2005. The major physical parameterizations considered were shortwave (Dudhia, CAM, and RRTMG) and longwave radiation scheme (RRTM, CAM, and RRTMG), microphysics scheme (WRF Double‐Moment 6‐class, WRF Single‐Moment 5‐class, Stony Brook University, and Morrison double‐moment), and cumulus parameterization (Kain–Fritsch, Betts–Miller–Janjic, Tiedtke, and New Simplified Arakawa–Schubert). The simulation for MRB by each set of parameterizations of WRF is assessed using root‐mean‐square error (RMSE), absolute error percentage, and bias maps. After a detailed fine tuning process, and from verifying the 1979–2005 long‐term simulations of WRF, WRF generally simulated realistic air temperature and precipitable water over MRB, but precipitation is over‐simulated, especially at Canadian Rockies. Air temperature simulated is sensitive to selected parameterizations of radiation and mircophysics but not precipitation simulated. Surface variables of sea surface temperature, sea ice fraction, and snow depth are essential for the accuracy of albedo and air temperature estimated. Air temperature and precipitable water are simulated to be reasonable over the domain, but the precipitation is over‐simulated around the high terrain areas. [ABSTRACT FROM AUTHOR]

Precipitation plays an essential role in hydrological cycle, water resource availability, and ecological economics sustainable development both within the Qilian Mountains (QM) and its surrounding. On the basis of meteorological station records and reanalysis data sets, we investigate the variations of precipitation in the QM during 1960–2014 and their connection to the shifts of regional atmospheric water vapour. Results show that precipitation in the QM as a whole has experienced pronounced wetting at an annual rate of 6.95 mm/decade. Significant (at 95% confidence level) precipitation increase mainly occurs in JJA (June–August) and slightly in DJF (December–February). The evident increase of precipitation appears in the mid‐east of the QM. Furthermore, the increasing rates of annual, JJA, and SON (September–November) precipitation increase with elevation, indicating obvious elevation‐dependent precipitation increase in the QM. The atmospheric precipitable water (PW) for annual, JJA, and SON time series over the targeted region generally shows significant increasing trends, especially during 1979–2014. The meridional and zonal water vapour budgets positively and negatively contribute to the regional net water vapour budget, respectively. Moreover, we demonstrate that the zonal water vapour budgets are strongly intensified and meanwhile the meridional ones except in transitional seasons are weakened. Thus, regional net water vapour budgets for annual and seasonal time series are increased. All in all, the shifts of the regional atmospheric water vapour, such as the increases of PW and water vapour budget (referring to the zonal and regional net water vapour budgets), agree with the result that the QM precipitation increases from 1960 to 2014, which suggests the QM wetting trend is in connection with the changes of the atmospheric water vapour. [ABSTRACT FROM AUTHOR]

A 30‐year high‐resolution (4 km) regional climate simulation (October 1981 to September 2011) is conducted in the interior western United States (IWUS) using the weather research and forecasting (WRF) model. The high spatial resolution is motivated by the IWUS complex terrain environment and the high spatial variability of atmospheric and land surface variables. The simulation, driven by the NCEP climate forecast system reanalysis, is convection‐permitting and uses the Noah multi‐physics land surface model. Modelled surface temperature, precipitation, and snow water equivalent (SWE) are evaluated against snowpack telemetry (SNOTEL) data and against the parameter‐elevation regressions on independent slopes model (PRISM) data set. The modelled daily minimum and maximum surface temperatures match the 4‐km resolution PRISM data, with spatial correlation coefficients close to 1. The simulation accurately captures the observed distribution and amount of seasonal precipitation and the mountain snowpack in the IWUS, although discrepancies exist, especially over the high‐elevation ridges. Simulated seasonal precipitation correlates well with observations, with correlation coefficients exceeding 0.85 for PRISM over the whole domain and 0.88 for SNOTEL over the mountain ranges. The simulation also replicates the spatial pattern of extreme precipitation events well, although it overestimates precipitation intensity and maximum duration of dry spells and underestimates the frequency of wet days. The simulated seasonal mountain snowpack and its spring melt‐off timing show a negative bias at most SNOTEL sites. This validation justifies the use of the 30‐year IWUS data set as a high‐resolution data source, almost equivalent to a reanalysis. [ABSTRACT FROM AUTHOR]

Using accurate precipitation data is critical to climate and hydrology research, but current studies have found that the precipitation measured by various standard precipitation gauges (P m) is much smaller than actual precipitation and there is a necessity to conduct bias correction before using the gauge‐measured precipitation (P m) data. Using the daily P m, wind speed and temperature data from 553 weather stations in China over 1961–2015, the wind‐induced error ( ∆PDL), trace precipitation ( ΔP t) and wetting loss ( ΔP w) and the corrected precipitation (P c) were systematically estimated. Consequently, the originally P m‐based climate zone division changed after the precipitation bias correction. The climate zone re‐division was conducted using four P c‐based indices, that is, annual mean precipitation P ¯ , Erinc's index I m, Sahin's index Ish and the United Nations Environment Programme (UNEP) aridity index I A. The results showed that annual mean correction amounts ( P ¯ diff) over 1961–2015 varied between 40.5 and 600.2 mm with the average value of 146.2 mm in China. The ranges of annual mean values of ∆ P ¯ t was 11.6–35.3 mm with an average of 24.8 mm, of ∆ P ¯ w was 3.6–74.2 mm with an average of 34.07 mm and of ∆ P ¯ DL was 1.4–525.7 mm with an average of 87.3 mm, respectively. The spatial distribution of P ¯ diff decreased from the northwest to the southeast. Annual P ¯ diff was generally smaller than 100 mm in northwestern China, but greater than 150 mm in southeastern China. By climate zone re‐division, the areas of severe arid decreased but the areas of severe humid areas increased, which indicated that actual climate conditions of China should be wetter than present assessment results. In conclusion, the bias correction indicated that a corrected climate zone division should be referred in future climatic change research. [ABSTRACT FROM AUTHOR]

Precipitation falling in the Snowy Mountains region of south‐east Australia is a critical resource—providing water for hydroelectricity, as well as irrigated agriculture and environmental flows throughout the economically important Murray River system. Improved understanding of the drivers of precipitation variability is therefore a key research aim. Focussing on synoptic types responsible for delivering precipitation ≥10 mm per day, an analysis is presented of the large‐scale atmospheric circulation drivers (“teleconnections”) of seasonal synoptic type frequency using cross‐wavelet and boosted regression tree methods. Results demonstrate that relationships are not stationary over the period 1900–2012, and complex interactions between teleconnections and synoptic atmospheric circulation drive precipitation variability. Importantly, we demonstrate that teleconnections do not act in isolation. Relationships with the tropical Pacific Ocean are shown to be key drivers of synoptic types associated not only with the dominant tropical moisture pathways to the Snowy Mountains, but also with extra‐tropical sources. Tropical sea surface temperatures are therefore shown to drive synoptic type frequency and facilitate the dominance of synoptic types with tropical moisture sources, most notability since the 1950s. [ABSTRACT FROM AUTHOR]

ABSTRACT The stationarity of rainfall annual maxima statistics is investigated in a northern Italian area characterized by important spatial variations in orography and precipitation climatology. Climatic changes in Italian recorded temperature series are widely acknowledged. In 2016, though, there is still discussion on the stationarity of the statistics of precipitation and its extremes in Italy. By means of standard hypothesis testing techniques, it is shown, for the first time in Italy, that changes in rainfall annual maxima climatology are indeed present in the period 1950-2005, relevant with regard to global climate change. In particular, in the rainy mountainous northwestern part of Lombardy, adjacent to the Swiss and Piedmont border, the annual maxima distribution for 6 to 24-h event durations significantly moves towards higher values when going from the first half (1950-1977) to the second half (1978-2005) of the period. It is remarkable, moreover, that for 1-h duration the distribution significantly moves towards lower values, suggesting a possible change in the precipitation regime. After compensating for data density changes by 'bootstrap' resampling, a median increase for all durations has also been confirmed for the (less rainy) Alpine area in northeastern Lombardy. Such changes in climatology have practical importance, because stationarity is a customary assumption when rainfall annual maxima frequencies are estimated for civil engineering. [ABSTRACT FROM AUTHOR]

ABSTRACT: The creation of baseline climate series is the first step towards the analysis of climate characteristics and behaviour in any region of the world. The objective of this article is to construct homogeneous precipitation series for the period 1982–2011, for the study of its spatial distribution and temporal evolution (dynamics) in the Province of Santa Elena, most occidental region of continental Ecuador. Data from 22 rainfall stations at the study location enabled the construction of five precipitation series using statistical and correlation techniques to complete information gaps. Precipitations present irregular temporal and spatial variation throughout the year, with a wet season between December and May. The December–January–February (DJF) and March–April–May (MAM) trimesters account for 59.7 and 39.1 of annual rainfall. The dry season, between June and November, presents almost zero rainfall. Small precipitations were also identified in coastal, topographically low areas, with precipitations more frequent events towards the continental region. Throughout the years, there has been high variability in precipitations, with the occurrence of wet‐dry episodes associated with the ‘El Niño–La Niña’ events, which were correlated with the sea surface temperature values of the Oceanic Niño Index. Trend analysis detected an average increase in rainfall of 2.1 mm year−1 in the Province, however, the trimestral rates oscillated between 2.2 and 4.3 mm quart−1. The construction of these precipitation series has been an important step for the spatial‐temporal characterization of this peculiar tropical climate region that presents arid characteristics. These series can be applied to base scenarios for the development of climate studies and water resource management in the region. [ABSTRACT FROM AUTHOR]

ABSTRACT: In this research, different characteristics (duration, affected area, extremity, and synoptic conditions) related to extreme precipitation events (EPEs), and the trends in frequency of EPEs in the Vosges Mountains (VG) region (north‐eastern France) have been analysed and the events were evaluated on regional scale using the Weather Extremity Index. The index combines three aspects of an EPE – rarity, spatial extent, and duration – and it enables a quantitative comparison of these aspects in a data set of EPEs. In this study, 54 EPEs (which occurred during 1960–2013) were selected using daily precipitation totals from meteorological stations. Although possible maximum duration of an EPE was set to 10 days, all detected EPEs lasted 1–5 days. The prevailing short EPEs (1–2 days) affected smaller areas as compared to long EPEs (3–5 days). Instead of the winter maximum of mean precipitation in the VG, the autumn EPEs prevailed in the data set (40% of all EPEs including the four strongest EPEs). Using the manual and the automated catalogues (Grosswetterlagen and SynopVisGWL, respectively), majority of the 54 EPEs was found associated with the west cyclonic weather type; however, none of the five maximum events was produced by this weather type. The two strongest EPEs were related to the stationary cold front rather than to the expected strong zonal circulation. The EPEs were mostly related to strong southwest airflow and flux of specific humidity. No significant trend was found in frequency of EPEs during the 54 years. Our results highlight new insights into the extreme precipitation in VG region. We believe that the ranking of EPEs according to their extremity in the VG region provides useful information for local decision making authorities, engineers, and risk managers. [ABSTRACT FROM AUTHOR]

This study presents (1) the temporal variations and trends of monthly and daily temperature and precipitation extremes in Alaska, and (2) the synoptic-scale circulation patterns associated with these extremes. The analysis is based on daily station observations of maximum temperature, minimum temperature and precipitation from 1948-2012 as well as monthly average temperatures and precipitation from 1920-2012 from 13 Alaska climate divisions. The frequencies of daily and monthly temperature extremes show variability and trends over the past 50-90 years consistent with a warming climate in Alaska. This warming is superimposed on low-frequency variability attributed to the Pacific Decadal Oscillation. Unlike the temperature extremes, occurrences of heavy-precipitation extremes do not display a coherent signal through time. The changes do not appear to be linked with an overall increase in the variance of temperature or precipitation. Composite analysis of sea level pressure (SLP) anomalies associated with a representative sample of different daily and monthly temperature extremes across Alaska shows that temperature and moisture advection, subject to topographic and coastal influences, is a key driver of these events. Composite SLP fields for daily and monthly extremes are similar, especially in winter, indicating that monthly extremes represent the recurrence of daily extreme patterns during those extreme months. The SLP anomalies were also often reduced in magnitude in the summer events compared with winter, consistent with the lower variance of temperature and SLP during summer. [ABSTRACT FROM AUTHOR]

ABSTRACT The seasonal distribution of mean precipitation and heavy rainfalls during 1960-2013 was analysed based on daily precipitation totals from 168 rain gauging stations in the Vosges Mountains area, north-eastern France. Concerning mean precipitation, an ancient Hrudička's index designed as a half-time of precipitation during a year, surprisingly well expresses the seasonality of precipitation and its clear correlation with the mean annual totals in the studied region. The annual course of mean precipitation leads to a distinction of four groups of stations with respect to the position of stations: MT, mountainous stations with maxima of precipitation in winter and an overall highest mean annual totals; LSp, stations situated on leeward slopes of the Vosges Mountains with two maxima of precipitation (primary in winter and secondary in summer); URP, leeward stations located in the Upper Rhine River Plain with the most humid summer season, and the lowest mean annual totals; WSd, windward stations not influenced by the Vosges Mountains, with relatively evenly distributed precipitation, and slight maxima in autumn. For the heavy precipitation, 1-10-days totals have been considered to be 'heavy' subsequent to applying the three common methods - peaks over threshold ( POT), block maxima ( BM), and return period estimates based on generalized extreme value distribution. Varying criteria have been employed. The BM method for annual maxima indicates that the heavy rainfall generally occurs during the most humid season although it can also occur anytime during the year. The POT and return period estimates methods reveal that the seasonality of extremes is threshold-dependent and that probably the threshold sensitivity is also related to the degree of orographic influence - higher occurrence of summer events in the lee while lesser occurrence of winter events in mountains, at higher threshold and shorter duration of event. [ABSTRACT FROM AUTHOR]

ABSTRACT Precipitation in the Tibetan Plateau ( TP) reaches its peak in summer. The seasonal projection skill of a statistical downscaling model ( SDM) for summer precipitation in the TP was compared with that of direct model output. The SDM, which is based on canonical correlation analysis ( CCA), significantly increased the projection skill. The CCA reveals the flow patterns behind the seasonal projection skill of summer precipitation in the TP between 1961 and 2012 and quantifies its relative contributions. East Asia 500 hPa geopotential height ( ZG500), tropical Indian Ocean sea surface temperature ( SST) and east Asia 850 hPa meridional water vapour flux ( MWVF850), obtained from the Max Planck Institute Earth System Model, low-resolution ( MPI- ESM- LR) simulations for phase 5 of the Coupled Model Intercomparison Project under the representative concentration pathway ( RCP) 2.6, RCP4.5 and RCP8.5 scenarios are considered as potential predictors. The SDMs are established in 1961-2005, validated in 2006-2012 and applied in 2013-2100. The ensemble canonical correlation ( ECC) is also applied to improve projection skill. The following results are obtained: (1) The SDM projection skill for each predictor is higher than that of the MPI-ESM-LR climate model, and ECC performs even better. (2) Spatial correlation patterns of different predictors with influence on the TP are well recognized by CCA. The high relevance of ZG500 can be explained by the thermal adaptation theory, that of SST exhibits a canonical Indian Ocean Dipole mode, and MWVF850 shows a simple water vapour link. (3) The amount of summer precipitation in the TP will slightly decrease under RCP2.6 by −3.4 mm decade−1, whereas RCP4.5 and RCP8.5 reveal an increase by 2.4 and 18.4 mm decade−1, respectively. [ABSTRACT FROM AUTHOR]

ABSTRACT Monthly mean satellite data from the Global Precipitation Climatology Project ( GPCPv2) are used to examine the year-by-year variability of precipitation over the Mediterranean Basin and its changes over the period 1979-2010. The results show that the mean annual precipitation averaged over the study area has slightly increased from 1979 to 2010 by 1.28 mm or by 0.2% (trend not statistically significant at the 95% confidence level). Nevertheless, examining the trends at a local scale, spatial and temporal patterns are revealed, with opposite trends in adjacent areas and increasing precipitation in summer and autumn against almost unchanged or decreasing precipitation in winter and spring, respectively. Inter-decadal changes of precipitation are detected, with precipitation decreasing in the 1980s, then increasing through the late 1990s and finally declining in the 2000s before levelling off since 2007. These changes are significantly anti-correlated ( R = −0.57, up to −0.66 in winter) with the North Atlantic Oscillation ( NAO) index, thus confirming the critical role of this large-scale teleconnection for the regional precipitation over the basin. [ABSTRACT FROM AUTHOR]

ABSTRACT We examine secular changes and multidecadal climate variability on a seasonal scale in northern France over the last 500 years and examine the extent to which they are driven by large-scale atmospheric variability. Multiscale trend analysis and segmentation procedures show statistically significant increases of winter and spring precipitation amounts in Paris since the end of the 19th century. This changes the seasonal precipitation distribution from one with a pronounced summer peak at the end of the Little Ice Age to an almost uniform distribution in the 20th century. This switch is linked to an early warming trend in winter temperature. Changes in spring precipitation are also correlated with winter precipitation for time scales greater than 50 years, which suggests a seasonal persistence. Hydrological modelling results show similar rising trends in river flow for the Seine at Paris. However, such secular trends in the seasonal climatic conditions over northern France are substantially modulated by irregular multidecadal (50-80 years) fluctuations. Furthermore, since the end of the 19th century, we find an increasing variance in multidecadal hydroclimatic winter and spring, and this coincides with an increase in the multidecadal North Atlantic Oscillation ( NAO) variability, suggesting a significant influence of large-scale atmospheric circulation patterns. However, multidecadal NAO variability has decreased in summer. Using Empirical Orthogonal Function analysis, we detect multidecadal North Atlantic sea-level pressure anomalies, which are significantly linked to the NAO during the Modern period. In particular, a south-eastward (south-westward) shift of the Icelandic Low (Azores High) drives substantial multidecadal changes in spring. Wetter springs are likely to be driven by potential changes in moisture advection from the Atlantic, in response to northward shifts of North Atlantic storm tracks over European regions, linked to periods of positive NAO. Similar, but smaller, changes in rainfall are observed in winter. [ABSTRACT FROM AUTHOR]

ABSTRACT Under the framework of an project 'Building Asian Climate Change Scenarios by Multi-Regional Climate Models Ensemble', the ability of eight regional climate models and two fine-resolution global climate models to reproduce late 20th century (1981-2000) precipitation climatology is assessed. Future precipitation change (2041-2060) under the A1B scenario is also quantified by applying four different ensemble methods: equal weighting, weighted mean ( WM), reliability ensemble averaging ( REA) and performance-based ensemble averaging, after applying fourfold cross-validation using observation and multi-model-simulated precipitation. The results indicate that the ensemble of simulated precipitation outperforms any single RCM in many aspects. Among the four ensemble approaches, the WM and REA methods show better skill in improving the simulation results, and are used for ensemble prediction of regional climate in Asia. Under the A1B scenario, the WM method estimates future precipitation change of approximately 0.2 mm day−1 with less precipitation in northern and western China and northern India, and more precipitation in most other areas in Asia. The future annual precipitation will decrease by 0.1-0.5 mm day−1 in northern India, Pakistan and the central area of southern China. No significant change is found over eastern Kazakhstan, Mongolia, north-central and western China. [ABSTRACT FROM AUTHOR]

ABSTRACT Long historical climate records usually contain non-climatic changes that can influence the observed behaviour of meteorological variables. The availability of parallel measurements offers an ideal occasion to study these discontinuities as they record the same climate. The transition from manual to automatic measurements has been analysed in this study. The dataset has been obtained from two independent climate networks in the Piedmont region, in Northwest Italy. From this dataset, 17 pairs of stations with up to 17 years of overlapping have been identified. On average the overlapping period is 12 years with 8760 daily data matched for a pair of stations. This dataset has proven valuable because it has made it possible to study a set of independently managed pairs of standard-quality stations, while most previous studies in this field analysed data from well-maintained instruments with the same operator, often at meteorological offices. The transition between two networks has highlighted important differences in the amount of precipitation and in the number of rainy days. On average, the automatic network has measured 12% less precipitation and has recorded 9% more rainy days (8 days) per year than the manual network. Both of these differences produce a spurious change in the precipitation of the analysed area, thus showing the importance of having a homogeneous dataset to identify real climate variations. [ABSTRACT FROM AUTHOR]

ABSTRACT Quantifying precipitation variability and trends is difficult and merits regular reassessment. In the present study, the seasonal homogenized precipitation series in Switzerland is investigated for the period 1901-2013 in terms of trends, inter-annual variability and the influence of large-scale flow. An objective clustering is applied, resulting in 32 distinct precipitation regions. Trends are analysed for all 32 regions with moving trend windows, and statistical significance ( p < 0.05) is assessed with Theil-Sen trend estimates and nonparametric Mann-Kendall trend tests. Inter-annual precipitation varies considerably regionally and seasonally. Of 2720 analysed trend windows of 33-113 years in length, 194 (7.1%) show a significantly positive trend and 10 (0.4%) a significantly negative trend. Most of the significantly positive trends are found for 50+ year series for winter, autumn and the year. 81% of the annual and 72% of the winter series show positive trends (0-3% per decade) for the 1901-2013 period. The trends are significant for 34% (22%) of the annual (winter) series. Long-term trends are generally in line with earlier estimates in literature considering somewhat shorter time periods. Significantly negative trends are only found for winter in the most recent decades. No significant trends are found for inter-annual variability and changes in the 10th and 90th percentile seasonal extreme precipitation thresholds. The influence of large-scale flow on precipitation variability is strongest in winter. The leading pattern for northern Switzerland ( nS) is the Euro-Atlantic blocking pattern. For southern Switzerland ( sS), the Eastern Atlantic (Scandinavian) pattern is dominant in winter (autumn). In nS, wet (dry) seasons are linked to south-westerly (north-easterly) flow. In sS, wet (dry) seasons are linked to southerly (northerly) flow. Strong evidence for imprints of atmospheric blocking on seasonal precipitation variability is found in winter and autumn. In spring, a high pressure anomaly stretching from the mid-Atlantic to central Europe is indicative of dryness in nS. [ABSTRACT FROM AUTHOR]

In this study, we investigate the influence of global climate oscillations on the local temperature and precipitation over the United Arab Emirates (UAE), which is one of the driest regions in the world with very high temperatures and low precipitation. The identification and assessment of remote interactions (teleconnections) are carried out by using ground station and gridded data sets. Monthly rainfall data from six ground stations over the UAE for the period of 1982-2010 is used in this study along with the long-term gridded precipitation and temperature data from the Global Precipitation Climatology Center and Global Historic Climatic Network. Linear correlations, wavelet analysis, and cross-wavelet analysis have been applied to identify the relation between climate indices and precipitation (temperature). The analysis reveals that the strong variability in precipitation is closely associated with the Southern Oscillation Index (SOI) and the Indian Ocean Dipole Index (IOD) during the months of August-March, September-January, respectively. In case of temperature, the strong variability is associated with the North Atlantic Oscillation Index (NAO) and the East Atlantic Oscillation Index (EAO) during the months of April-October, July-December. Spatial analysis of cross-wavelet reveals that the winter precipitation is significantly influenced by SOI and temperature during summer by the NAO. This research concludes that the negative phases of SOI (NAO) play a significant role in the increase of precipitation (decrease in summer temperatures) over the UAE region. [ABSTRACT FROM AUTHOR]

Groundwater is the source of almost 85% of freshwater requirement in rural India and 50% in urban India. Bihar is particularly reliant on groundwater, as it has the lowest supply of piped drinking water among Indian states. We examine the exposure of this resource to stress due to climate change; specifically, we estimate the influence of climate parameters on availability of groundwater in Bihar in about 10 years (2021) and 40 years (2051) from the most recent reference-point of 2011 for which data are available. Considering the estimated increase in temperature in Bihar of 0.32 °C and 1.28 °C from the reference period under high-end scenario, annual replenishable groundwaterwould decrease by 4.6 and 17.8%, respectively, for 2021 and 2051. An estimated increase in annual average precipitation by 1.6 and 6.4% from the reference period under low-end scenario would increase estimated recharge levels by only 0.6 and 2.4%, respectively, in 2021 and 2051. The combined impact of estimated change in climate parameters (temperature and precipitation) would bring groundwater availability from 24 litres per capita per day (lpcd) now to 23 lpcd by 2021 and 20 lpcd by 2051 under worst-climate scenario (high-end temperature and low-end precipitation). Projections of population growth for the years examined compared to the Indian population in 2011 revealed the reduction in water availability further to an estimated 20 lpcd by 2021 and to 13 lpcd by 2051 under 'pessimistic scenario' (worst-climate and high-end population). Planned artificial replenishment can fill the gap neither in the shorter nor in the longer term. We therefore conclude that due to the cumulative effects of climate and population, groundwater scarcity in Bihar could reach a level well below the minimum lpcd set by the Government of India and by WHO, unless effective corrective interventions will occur. [ABSTRACT FROM AUTHOR]

ABSTRACT An international programme dedicated to the study of the Third Pole Environment ( TPE) is now developing. The TPE region is centred on the Tibetan Plateau and concerns the interests of the surrounding countries and regions. To improve input for hydrological research, we collected precipitation data on 241 meteorological stations across the TPE region; these data were obtained from various countries, thus including various types of gauges. Employing the procedure recommended by the World Meteorological Organization ( WMO), a full version of bias adjustment was applied to the data, including adjustments for wind-induced error, wetting loss, evaporation loss and trace amount for each station. The results reveal that the average annual precipitation has increased considerably from a minimum of 4 mm to a maximum of 409 mm with an overall mean of 27% from the adjustment, the largest bias being found in the Chinese standard precipitation gauge ( CSPG) which was used in the central TPE region. In addition, the bias shows variable spatial and temporal patterns in different climate zones throughout this area. It is expected that this study and its results will be beneficial for hydrological and climatic studies over the TPE region. [ABSTRACT FROM AUTHOR]

ABSTRACT Daily precipitation data from 34 weather stations in Northeast China from 1960 to 2008 are used to examine trends in the occurrence of dry days and prolonged dry episodes. Trends in the mean length and frequency of prolonged dry episodes, as well as the number of dry days within prolonged dry episodes ( DDPDE), are computed regionally and for individual stations at the threshold levels of 1 and 2 mm day−1. Regionally, the number of dry days is increasing in the summer half-year and decreasing in the winter half-year. DDPDE is significantly increasing in the summer half-year; the increased frequency of dry spells has the greatest effect. The mean length of prolonged dry episodes in the winter half-year has decreased significantly. Our results indicate that neither the frequency nor the mean length of prolonged dry episodes, alone, can adequately describe the short-term dry conditions of an area. Multiple characteristics of dry spells, including frequency, length, and the number of DDPDE should be considered. DDPDE is a function of both the frequency and length of dry episodes, but may be more influenced by one or the other characteristics of dry spells, depending on the season or region. [ABSTRACT FROM AUTHOR]

ABSTRACT Various types of studies require a sufficiently long series of data processed identically over the entire area. For climate analysis, it is necessary that analysed time series are homogeneous, which means that their variations are caused only by variations in weather and climate. Unfortunately, most of the climatological series are inhomogeneous and contain outliers that may significantly affect the analysis results. The 137 stations with precipitation measurement belonging to the meteorological station network governed by the Meteorological and Hydrological Service of Croatia were selected for the present analysis. Most of the data series cover a period from the late 1940s or early 1950s through the year 2010. For quality control and homogenization, an approach based on the software ProClimDB/Anclim was applied. In this study, we describe the results from the quality control and homogenization process for monthly precipitation sums as well as the spatial relationship of precipitation in the Croatian region. The precipitation network in Croatia is fairly homogeneous as only 23% of the 137 analysed stations are found to be inhomogeneous. [ABSTRACT FROM AUTHOR]

Annual, seasonal and monthly variations in precipitation during the period 1911-2011 were evaluated using spatially interpolated monthly precipitation records at 165 stations with more than 30 years of data (of which 32 stations had 101 years of data referring to full length of study period). Historical trends and cyclic patterns of precipitation and links to teleconnection indices were analysed. The results show that annual precipitation in Finland increased by 0.92 ± 0.50 mm year−1 ( p < 0.05) during the study period (1911-2011), and showed negative relationships with the East Atlantic/West Russia ( EA/ WR) teleconnection pattern ( ρ = −0.41, p < 0.05) through the years 1950-2011. However, there were spatial (north-south/east-west) differences between regions. The time cycle ( λ) for annual precipitation cycles was estimated to 149 years ( R2=0.15), and 1964 was indicated as the turning point from a negative (dry) to a positive (wet) phase. Analysis of seasonal and monthly cycles showed larger variations, depending mainly on teleconnection effects. Analysis of seasonal precipitation determined increasing trends for winter (by 0.46 ± 0.19 mm year−1) and summer (by 0.32 ± 0.29 mm year−1), while no clear trend was found for spring and autumn precipitation ( p > 0.05). Winter precipitation was most strongly correlated with the North Atlantic Oscillation ( NAO) index ( ρ = 0.55, p < 0.05), while the EA/ WR pattern was the most significant teleconnection index for precipitation variations in spring ( ρ = −0.33, p < 0.05) and summer ( ρ = −0.49, p < 0.05); the precipitation variability during autumn was negatively associated with the Scandinavia ( SCA) pattern ( ρ = −0.40, p < 0.05). The results clearly indicate that Finland has experienced wetter climate than normal conditions during recent decades, and precipitation in the Fenno-Scandinavian climate is controlled by a number of climate teleconnection indices, not just the NAO as previously assumed. [ABSTRACT FROM AUTHOR]

ABSTRACT Ethiopia has wide eco-environmental diversity ranging from extreme heat at one of the lowest places in the world to one of the coolest summits in Africa. Associated with this environmental diversity and climate change, climatic extremes are expected to change over time and also vary across eco-environments in the country. This study was conducted to examine the trends of past precipitation and temperature extremes over three eco-environments in Ethiopia. The study involved analysis of 20 extreme indices computed from daily temperature and precipitation data spanning over 42 years (1967-2008). The climate data were obtained from 11 stations selected from three major eco-environments (pastoral, agropastoral and highland). The results indicated positive trends for maximum value of the maximum temperature ( TXx), warm days ( TX90p), warm nights ( TN90p) and warm spell duration indicators ( WSDI) and negative trends for cool days ( TX10p), cool nights ( TN10p) and cold spell duration indicators ( CSDI) in more than 8 of the 11 stations studied. However, most of the trends were not significant at many of the stations and the significant trends were not uniquely differentiated by eco-environments. Unlike temperature extremes, precipitation extreme trends showed high variability among nearby stations within eco-environments and were not significant at many of the stations studied. It is concluded that trends of temperature and precipitation extremes vary considerably among stations located within a given eco-environment indicating that the response of local climate to global warming could be different in physiographically diverse regions. [ABSTRACT FROM AUTHOR]

ABSTRACT Extreme rainfall events pose considerable threats to society and critical infrastructure yet, by definitions, these events are rare. Reliable estimates of the likelihood of such events are required to assist with impact quantification and risk management. Regional frequency analysis of pooled extreme rainfall to estimate the likely impacts of a changing climate is a well established method to assess the probability of these extremes. Previous analyses of country-wide changes to UK extreme daily rainfall have used the 9 Hadley UK Precipitation ( HadUKP) regions (Alexander and Jones, 2000), which are not appropriate for use with extremes. While these characterize well the mean daily intensity and frequency within each region, extreme rainfall climatology differs from that of the mean characteristics. As a result the existing HadUKP regions do not represent extreme rainfall behaviour adequately, with regard to the frequency, intensity or timing of extreme events. Focussing on many extreme rainfall characteristics, such as the seasonal timing and magnitude of maxima, this article presents a formal representation of extreme regions which specifically describe extreme spatial and temporal characteristics. The article concludes with a brief exploration of improved event estimation using these extreme rainfall regions. The new regional definitions provide clearer upward trends in annual maxima over the period 1961-2010 than those estimated using the HadUKP regional pools. © 2013 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

ABSTRACT Northern Tunisia is the rainiest part of the country where most of the water management structures (dams, reservoirs, etc) are located. Its strategic situation with respect to surface water resources encourages the investigation of the climate change impacts projected by climate models. The goal of this study is first to compare the observed precipitation with climate model outputs, and then to evaluate the future changes projected by different climate models. The study area is subdivided into four regions: the upstream and downstream transboundary Medjerda basin, the northern coastal basins and the eastern coastal basins. A database provided by the Tunisian hydrological service includes 388 stations with complete monthly precipitation data over the period 1961-2000. An ensemble of Regional Climate Models ( RCM) simulations provided by the European Union-funded project ENSEMBLES are used. Six RCM model runs ( CNR-A, DMI-A, DMI-B, ICT-E, SMH-B and SMH-E) are analysed, for the control period 1961-2000 and two projection periods, 2011-2050 and 2051-2090. The models efficiency in reproducing seasonal precipitation amounts and variability is evaluated. A 1-km monthly precipitation reference grid is computed through the interpolation of rainfall observations during the period 1961-2000 with kriging techniques. Monthly precipitation series averaged over the four basins are built for comparison during the control period. The RCM outputs are evaluated with respect to the annual precipitation cycle and rainfall frequency distribution using robust statistics. For the control period, features of the seasonal regimes are well reproduced by all models. It is found that models underestimate seasonal precipitation on average by 20%. The discrepancy between model outputs and observations depends on the season. For the future, in summer and autumn the different models do not project major changes in the seasonal distributions. However, for winter and spring, all the models project a significant decrease of precipitations. Copyright © 2013 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

ABSTRACT It is important to investigate potential changes in temperature, precipitation and solar radiation for assessing the impacts of future climate change on agricultural production for specific regions. In this study, climate scenarios of precipitation, temperature and solar radiation for the North China Plain ( NCP) were constructed in terms of stochastic daily weather sequences. A nonhomogeneous hidden Markov model ( NHMM) was used to downscale daily precipitation projections at 32 stations during winter wheat and summer maize growing seasons for a baseline (1966-2005) and a 21st century (2080-2099) A1B scenario, using selected general circulation models ( GCMs). A climatological seasonal cycle of regional-averaged daily reanalysis precipitation was used as input to the down-scaling for the baseline simulation; this input was then scaled by the precipitation changes from GCM projections to generate down-scaled stochastic simulations of precipitation in the 21st century. Temperature was generated using a weakly stationary generating process, conditional on precipitation occurrence, with 21st century additive changes taken from the GCMs at the regional scale. Three hypotheses about changes in solar radiation (−20%, 0% and 20%) were made considering the large uncertainty in its future change. The down-scaled simulations exhibit station increases in the mean daily rainfall of 13.9-69.7% in the scenarios driven by the GCM with the projected largest and multi-model mean precipitation increase for the wheat season, with changes of 0.4-29.9% for the maize season. In the scenario driven by the GCM with the largest projected precipitation decrease, the simulated rainfall decreases at all stations, with changes ranging from −24.6 to −0.1% for the wheat and maize seasons, respectively. Temperature increases by about 3.7 °C for the wheat season and 3.6 °C for the maize season. [ABSTRACT FROM AUTHOR]

ABSTRACT The Middle East and North Africa ( MENA) region can be considered as the most water-scarce region of the world. The Intergovernmental Panel on Climate Change projects strong changes in climate across MENA, further exacerbating pressure on available water resources. The objective of this study is to undertake a climate change assessment for 22 MENA countries in order to quantify the problems these countries may encounter up to 2050. To evaluate climate change in MENA, nine global circulation models representing two future periods (2020-2030 and 2040-2050) were statistically downscaled and compared with a current climate, defined as the period 2000-2009. Besides precipitation only this study also focuses on change in water demand by vegetation reference evapotranspiration ( ETref). It was found that for both future periods the annual precipitation sum will decrease for the majority of countries, with decreases of 15-20% for the latter period. For some countries, e.g. Djibouti and Yemen, an increase in annual precipitation of 15-20% was found. The annual ETref shows an increase for all countries for both future periods, with the strongest increases for the latter period. For the extreme situation, it was found that the minimum monthly and annual precipitation sum does not become smaller in the future climate. It in fact increases. In contrast, the maximum monthly and annual ETref increases for all countries. This indicates that projected changes in demand are likely to have a more adverse effect than changes in supply. Spatial analysis showed that the largest precipitation decreases are to be found in southern Egypt, Morocco, central and coastal Algeria, Tunisia, central Libya, Syria, and central and eastern Iran. A case study for Morocco revealed that the potential water deficit, which is already apparent for the current climate, becomes even larger for the future climate. [ABSTRACT FROM AUTHOR]

The dense, intact rainforests of the Guianas (northern Amazonia) are important for the regulation of the local and regional climate, but preclude easy access so a large data gap exists. The rainforest-savannah boundary may also be particularly susceptible to increasing pressures from ecosystem exploitation and climate change. It is important therefore to establish a baseline climate regime so that the impacts of any future change can be determined. Currently this area is not covered by the publicly available climate data sets, so interpolated data sets are not an accurate representation of the climate of this area, emphasizing the need for a more detailed analysis in this region. Here, we collate the available data sets and use these to derive maps of observed precipitation and temperature across the region. To overcome the limitations in the inadequate observational data sets, we also test and use the ECMWF ERA-40 reanalysis data set for the period 1958-2001 at a ∼125 km2 (1.125°) resolution. Mean differences (biases) and annual average spatial correlations are examined between modelled and observed time series comparing the seasonal cycles and the yearly, monthly and monthly anomaly time series. The results show that with the exception of sub-grid resolution mountain environments, reanalysis data for the Guianas provide a consistent and relatively accurate spatial distribution of temperature. Precipitation is modelled less accurately, with best results for the average timings, length and severity of the dry periods. This study provides consistent and quantitative details on the spatial variations in seasonality, particularly in areas lacking observations, thereby advancing beyond previous studies. Precipitation is highly variable in the region so care must be taken when averaging modelled data over large geographical areas for comparisons with gridded data sets based on few observations. This is the first comprehensive study of the recent historical climate and its variability in this area. Copyright © 2011 The Authors. Journal compilation © 2011 The Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Extratropical and tropical influences on Tibetan Plateau severe and extreme dry and wet summer months are investigated focussing on the large-scale circulation and using results of the coupled climate model ECHAM5/MPI-OM. A pre-industrial control run and scenario runs for the 4th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) are considered. Tibetan Plateau precipitation in months of wetness and drought is related to atmospheric circulation anomalies in the North-Atlantic/European sector and to sea surface temperature anomalies in the Tropics. Drought on the Tibetan Plateau is associated with a pronounced wave train bridging Eurasia from the North Atlantic to Asia. Increased transient eddy activity in the North Atlantic storm track has a more south-west to north-east orientation. This supports a high pressure anomaly over the eastern North Atlantic and Scandinavia which excites a cross Eurasian wave train reducing the moisture inflow to the Tibetan Plateau from the Arabian Sea. A concurrent warming in the tropical Indian Ocean increases the low level monsoonal westerlies deviating the moisture transport from the Bay of Bengal towards the Indochinese Peninsula and the Philippines. Wetness on the Tibetan Plateau is dominated by a cooling in the tropical oceans, whereas atmospheric flow is predominantly zonal in the extratropics of North America and Europe. Thus, moisture inflow can reach the Tibetan Plateau via the Arabian Sea, the Bay of Bengal and the mid-latitude westerlies. Future scenarios show little change of atmospheric flow composites for wetness and dryness; the Tibetan Plateau droughts increase by 10% for an A1B-scenario, while extreme wet summer months are reduced by approximately 1%. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

This article focuses on some recent changes observed in the Tropics with special emphasis on the African monsoon region using high-resolution gridded precipitation from the Climatic Research Unit (period 1979-2002), outgoing longwave radiation at the top of the atmosphere from the National Oceanic and Atmospheric Administration and atmospheric reanalyses from the Climate Prediction Center (NCEP-DOE2, period 1979-2007). The results show a rainfall increase in North Africa since the mid-90s with significant northward migrations of rainfall amounts, i.e. + 1.5° for the 400 mm July to September isohyets, whereas deep convection has significantly increased and shifted northward. The subsidence branch of the northern meridional overturning has also been reinforced and shifted by 1° latitude northward in winter. At larger scale, an unambiguous reorganisation of the circulation with increasing subsidence in high troposphere over the Mediterranean and increasing ascendance in the African Intertropical Convergence Zone in northern summer has been noticed in the meridional cell overturning. After 1993-1994, the migration of the Saharan heat low towards northwest has been more marked (+1° to + 2° in latitude; − 1° to − 2° in longitude), whereas its centre intensified at the peak of the tropical rainy season (+10 gpm thickness in the 700-925 hPa layer). These changes are associated with significant reinforcements of the southwesterly low-level winds and Tropical Easterly jet and with a northward shift of the African Easterly jet. Analyses of Global Circulation Model outputs issued from Intergovernmental Panel on Climate Change (A1B scenario and from forced experiments on the ARPEGE-climat (Action de Recherche Petite Echelle Grande Echelle) and Atmospheric Global Circulation Model show that at least part of these changes could be due to the recent warming observed in the Mediterranean/Saharan region. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

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A recent study on cloud observations reports an increase in total cloud cover at Faraday/Vernadsky since 1960 in the annual and wintertime data. The aim of this present study is to investigate whether this increase in total cloud cover has influenced the precipitation in this region. For this purpose, precipitation observations at the Antarctic base Faraday/Vernadsky between 1960 and 1999 were analysed. A positive trend, significant at the 5% level, was found in the number of precipitation events recorded during winter, showing an increase of 13 events per decade. The annual number of precipitation days has increased by 5.7 per decade during the period of investigation, with highest increase rates being observed in winter and autumn. The characteristics of these findings confirm that results previously published though trends presented here are ∼50% smaller due to a more thorough data quality control of the observational data. These results indicate that an increase in total cloud cover at Faraday/Vernadsky observed since 1960 in the annual and wintertime data is reflected in higher numbers of precipitation events and days. Analyses of the precipitation type found an increase in the proportion of events of non-frozen precipitation, which is significant (1% level) on an annual basis as well as in spring and autumn (both significant at 5% level). This is a clear manifestation of the year round temperature increase observed over the Antarctic Peninsula. The increase in non-frozen precipitation will have reduced the albedo in the region and will thus have contributed to the temperature-albedo feedback. To refreeze rain that is draining through glaciers energy is extracted from the surrounding ice, thereby physically corroding the ice. This will have contributed to the observed retreat of glaciers around the Antarctic Peninsula. As non-frozen precipitation falling on frozen ground cannot be stored but instead runs off, less water will be available for the ecosystem. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

The article presents a discussion on the use of a Support Vector Machine (SVM) in downscaling precipitation to river basin in India. It describes a methodology which uses predictor variables from the National Center for Environmental Protection (NCEP) and from the third Canadian general circulation model (CGCM3) for special report of emission scenarios (SRES). The data includes thermodynamic parameters related with precipitation. NCEP and CGCM3 data were used to study seasonal stratification. Using the model the study found that precipitation is expected to increase in several emission scenarios. An overview of the study is provided.

The article examines time variations of the effects of the modes on temperature and precipitation at more than 100 European stations are for period 1958-1998. Time variations are investigated by running correlations with the 15-year window. The spatial structure of the variations are assessed by cluster analysis of time variations of correlations. The groupings together with changes in the intensity and position of the circulation modes suggest possible mechanisms of the time variations in the circulation-to-climate effects.

This article presents a study regarding the trends in extreme daily temperature and precipitation near Lake Hövsgöl, Mongolia. From 1963 to 2002, a long-term set of daily maximum and minimum temperature and precipitation data are analyzed for the Lake Hövsgöl area in Mongolia. It examines eight indices of extreme precipitation and six indices of extreme temperature. Results revealed that climate conditions over northern Mongolia are changing as showed by a warming trend identified during the research period.