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This study presents a comprehensive analysis of rainfall trends in the middle Euphrates region of Iraq, extending from 1980 to 2018, including wide region between the stations of Samawa, Al-Najaf, Karbala, Hilla, and Diwaniya. The research aims to fill a critical gap in the understanding of regional hydrological patterns and provide essential insights for sustainable water resource management. Using advanced statistical methods, such as the MannKendall test and Sen’s slope estimator, along with autocorrelation and cross-correlation analyses, we detected slight trends that were not previously reported. Principally, the Mann-Kendall test indicated no significant overall trends, while Sen’s slope estimator identified slight positive and negative trends at specific stations, highlighting local climatic variations. the findings reveal that all stations, except Samawa, indicated stationarity and homogeneity, with a particularly strong positive mutual correlation between Karbala and Hilla stations (0.7693 at lag 0). This research contributes new insights into rainfall variability in the Middle Euphrates, in Iraq, which presents significant data to improve water resource management strategies and inform future hydrological studies in the region. [ABSTRACT FROM AUTHOR]

Studying rainfall patterns is very important because agricultural production and flood conditions depend on proper water management. Therefore, accurately identifying trends in climate scenarios is essential to achieve this goal. This study, therefore, analyses rainfall trends using the Mann–Kendall test (MKT), modified Mann–Kendall test (MMKT), Spearman rank correlation (SRC), Şen slope estimator (SSE), and innovative trend analysis method (ITAM). This investigation analyses annual, monsoon, autumn, summer, and winter rainfall trends using the most extensive hydrometeorological time series from 1901 to 2020. Five such methods of trend analysis use 120 years of gridded meteorological data from the India Meteorological Department for the neighbouring four river basins Kangsabati, Keliaghai, Silabati, and Dwarkeswer in east India. For the winter period, no significant trend is detected using the MKT, MMKT, SRC, and SSE. While the ITAM detects a significant trend at 88% of grid points of the study area. During other seasons, the MKT, MMKT, SRC and SSE notice trends for 76% of grid points with less significance than the ITAM method. Overall results obtained using the ITAM and MMKT methods are proved to be more effective in detecting sensitive trends. This study can serve as scientific support for the identification and strategic mitigation of climatic change impacts on water management to reduce the risk of climate change. [ABSTRACT FROM AUTHOR]

The objective of this research is to select the best orbital sensor for rainfall estimates (monthly and annual scales) and to analyze the frequency and magnitude of extreme rainfall events and their trends and disruptions based on the use of satellite rainfall product data for the Cananeia–Iguape Coastal System (CICS). Data from four satellite rainfall products were used to identify the correspondence with seven points on the surface of the study area. Statistical metrics were used to identify the best satellite rainfall product. After identifying the sensor with the best performance in estimating orbital precipitation, extreme events were identified by the Standardized Precipitation Index (SPI) on a one-month (SPI-1), three-month (SPI-3), and twelve-month (SPI-12) scale. Trend and rupture detection in the time series were performed using different statistical techniques (Mann–Kendall, Pettitt, Standard Normal Homogeneity Test, or Buishand test). Among the satellite rainfall products, CHIRPS had the best measurements for the analyzed points on the surface. The year 1983 was characterized as very rainy, also marked by the occurrence of El Niño, and was marked by the rupture of the rains at all points (IDs 1, 2, 3, 4, 5, 6, and 7) analyzed in the month of June. The decrease in monthly rainfall was more significant in the months of February (at points IDs 1, 2, 3, 5, and 7) and April (IDs 1, 3, 5, and 7). Decreased rainfall may cause CICS mangrove shrinkage. These results showed the importance of studying rainfall in an area with mangroves in order to understand the dynamics of vegetation in the face of climate change. [ABSTRACT FROM AUTHOR]

Southeastern South America (SESA) experienced some of the largest positive trends in total and extreme precipitation of the Southern Hemisphere during the last decades. The City of Buenos Aires, the second largest mega‐city of SESA, has been particularly hard‐hit by these trends due to its flat topography and poor natural drainage. Recent studies suggest that these precipitation extremes may exacerbate even further under global warming, but the physical mechanisms responsible for such events have not been documented for this region so far. This study quantifies the relative contributions of dynamics (atmospheric fronts) and thermodynamics (vertical stability) on the observed variations and trends of daily, seasonal and annual precipitation over the City of Buenos Aires between 1981 and 2020 by splitting the precipitation events into convective and stratiform. Results show that the relative contributions from dynamics and thermodynamics depend on the season under consideration: the positive trends in summer precipitation have been favoured by a net increase in vertical instability with a negligible contribution from dynamics, while the increased frequency of fronts in autumn and winter, when no changes in vertical instability have been observed, has contributed to the higher frequency of cold‐season convective events. [ABSTRACT FROM AUTHOR]

Rainfall is one of the dominating climatic parameters that affect water availability. Trend analysis is of paramount significance to understand the behavior of hydrological and climatic variables over a long timescale. The main aim of the present study was to identify trends and analyze existing linkages between rainfall and streamflow in the Nilwala River Basin (NRB) of Southern Sri Lanka. An investigation of the trends, detection of change points and streamflow alteration, and linkage between rainfall and streamflow were carried out using the Mann–Kendall test, Sen's slope test, Pettitt's test, indicators of hydrological alteration (IHA), and Pearson's correlation test. Selected rainfall-related extreme climatic indices, namely, CDD, CWD, PRCPTOT, R25, and Rx5, were calculated using the RClimdex software. Trend analysis of rainfall data and extreme rainfall indices demonstrated few statistically significant trends at the monthly, seasonal, and annual scales, while streamflow data showed non-significant trends, except for December. Pettitt's test showed that Dampahala had a higher number of statistically significant change points among the six rainfall stations. The Pearson coefficient correlation showed a strong-to–very-strong positive relationship between rainfall and streamflow. Generally, both rainfall and streamflow showed non-significant trend patterns in the NRB, suggesting that rainfall had a higher impact on streamflow patterns in the basin. The historical trends of extreme climatic indices suggested that the NRB did not experience extreme climates. The results of the present study will provide valuable information for water resource planning, flood and disaster mitigation, agricultural operations planning, and hydropower generation in the NRB. [ABSTRACT FROM AUTHOR]

This paper describes the long-term grid-point rainfall trends in the context of climate change, recent regionalised rainfall decline and drought events for mainland Portugal, which is teleconnected, in most cases, to the trends of mathematical descriptions of the North Atlantic Oscillation (NAO) during the century from October 1919 to September 2019. Grid-point rainfall dataset (1919–2019, from 126 centroids in a regular mesh over the country) have been constructed from high-quality ground-based data and as such, it provides a reliable source for the analysis of rainfall trends at different timescales: October–December, January–March, December–March, and the hydrological year. The Mann–Kendall (MK) coupled with Sen's slope estimator test are applied to quantify the trends. The Sequential Mann–Kendall (SQMK) analysis is implemented to obtain the fluctuation of the progressive trends along the studied 100-year period. Because of their pivotal role in linking and synchronising climate variability, teleconnections to the North Atlantic Ocean are also explored to explain the rainfall trends over the Portuguese continuum. The results provide a solid basis to explain the climate change effects on the Portuguese rainfall based on significant associations with strong negative correlations between changes in rainfall and in NAO indices. These strong opposing correlations are displayed in most of the winter seasons and in the year. After the late 1960s, a generalised rainfall decrease emerges against a background of significant upward trends of the NAO; such coupled behaviour has persisted for decades. Regionalised droughts at three identified climatic regions, based on factor analysis and Standardised Precipitation Index (SPI), are also discussed, concluding that the frequency of severe droughts may increase again, accompanied by a stronger influence of the recently more positive and unusual winter season and annual NAO indices. [ABSTRACT FROM AUTHOR]

Understanding changes in rainfall at a continental scale can inform adaptation and resilience in all sectors that are sensitive to rainfall. This study examined spatiotemporal changes in annual and seasonal rainfall, extreme and non‐extreme rainfall, and their probability and intensity over the period from 1960 to 2019 across Australia for six rainfall zones (RZs) using high‐quality daily rainfall from 7,593 climate stations. The results revealed statistically significant changes in long‐term rainfall, with an increasing trend in Northern and Central Australia, and a decreasing trend across Southern Australia where the main agricultural areas are located. The cross‐wavelet power spectrum analysis denoted strong coherent resonance cycles in spring–summer or autumn–winter seasons with varying phase differences across six RZs. More specifically, summer rainfall occurred more regularly in the summer‐dominant and arid RZs, whereas winter rainfall became more unreliable in the winter‐ and winter‐dominant RZs. The changes in regional rainfall were characterized by changes in probability and/or intensity of extreme and non‐extreme rainfall revealed through the Spearman Rank correlation. The upward trend in summer‐dominant and arid RZs appears to be a result of increased extreme rainfall intensity and probability, and non‐extreme rainfall probability, especially in summer. The decreased rainfall in the rest of the RZs can be attributed to decreased extreme rainfall probability and non‐extreme rainfall intensity. These results can help decision makers in the agricultural and water resources management sectors identify risks and opportunities, and to devise strategic plans to mitigate droughts through land use planning and construction of infrastructure. [ABSTRACT FROM AUTHOR]

Climate change is supposed to alter not only the mean and variability but also the distribution of rainfall. Changes in rainfall distribution during the monsoon months (June to September) of Bangladesh are evaluated in this study using quantile regression. Monthly rainfall data for the period 1961–2014 recorded at 18 locations distributed over the country were used for this purpose. Distributional changes of monthly rainfall showed downward convergent lines are dominant in peak monsoon months of June, July and August at 28%, 50% and 28% stations, respectively, followed by horizontally divergent lines at 17% of stations during those months. The dominating category of last monsoon month (September) rainfall was found upward divergent lines at 50% stations. The results revealed a decrease in many rainfall quantiles from June to August and increase in September in most of the stations. The increasing trend lines of September rainfall quantiles were found to become more diverse with time, which indicates an increase in rainfall extremes and the possibility of more floods which are already very common in the last month of monsoon in Bangladesh. The decrease in lower quantiles of rainfall in most of the monsoon months may cause an increase in the probability of droughts in the country. The study provided more insight on monsoon rainfall changes and improved understanding of climate change impacts on monsoon rainfall regime which can help in planning climate change adaptations in Bangladesh. [ABSTRACT FROM AUTHOR]

For improving sustainable water resources management and planning at local and regional scales, specifically in small islands, long-term and recent rainfall trends due to temporal shifts in major climatic drivers should be investigated based on dense and long-running ground data series — as done in this research work for the North Atlantic Portuguese island of Madeira (741 km2). Monthly, wet season and annual rainfall trends have been obtained via the non-parametric Mann-Kendall (MK) and the Sen's slope estimator tests for 41 rain gauges spanning from 1940/41 to 2016/17 (77 hydrological years, each starting on October 1). By means of the Sequential Mann-Kendall (SQMK) test, abrupt temporal shifts in the wet season and annual rainfall, and in the North Atlantic Oscillation index (NAOI) series have been identified on the late 1960's — sandwiched by two subperiods with clearly opposite trends. In general, the results suggest considerably and statistically significant decreases in rainfall, exacerbated in recent years at the central region of the island — one of the most important locations in terms of fresh water security. Additionally, this work provides a solid basis to explain the climate change effects on the Madeira rainfall, suggesting that abrupt changes of the island's rainfall variability can be directly linked to those of the North Atlantic Oscillation (NAO) climatic driver based on the strong established teleconnection. These findings are expected to contribute to the improvement of actions towards sustainable water management in the island, and of some other small islands with climatic characteristics influenced as well by large-scale circulation patterns. [ABSTRACT FROM AUTHOR]

The rainfall series from the South African Astronomical Observatory in Cape Town, South Africa, is one of the longest known single site instrumental records in the southern hemisphere, spanning over 176 years. Rainfall data are analysed to determine trends and periodicity in the series for annual, seasonal and monthly time scales. Using the Mann Kendall test and Sen's slope, significant negative rainfall trends are recorded for the months of March and October, and for the spring season (from September to November). Using the Mann Kendall and its modified versions to account for serial correlation, as well as a multi‐temporal trend analysis, we demonstrate a positive rainfall trend during the first 60 years (i.e., 1841–1900), which thereafter changes to a long‐term (1900–2016) negative trend, but incorporating a shorter 40 years significant positive trend between 1930 and 1970. We identify cyclic patterns with recorded periods of 9–12 years, 16–30 years and 30–42 years for rainfall, the Southern annular mode (SAM) and Southern oscillation index (SOI). In addition to the notable 9–12 years rainfall cycle that is evidently associated with sunspot cycles, 20–30 years and longer 32–40 years rainfall, solar, SAM and SOI cycles are also identified. [ABSTRACT FROM AUTHOR]

ABSTRACT: Understanding the spatio‐temporal variability of rainfall over mountainous regions such as the Andes is crucial for the maintenance of water resources and ecosystems. This study provided a comprehensive analysis of the signal, statistical significance and spatial pattern of rainfall trends in central and southern Peruvian Andes (CSPA) from 1965 to 2010. Rainfall from 47 quality‐controlled rain gauge stations was examined using the hydrologic calendar year. Total and extreme rainfall indices proposed by the Expert Team on Climate Change Detection and Indices (ETCCDI) were calculated and trends were examined with Mann–Kendall test and Sen's slope estimator. Significant regional patterns of changes in rainfall extremes were investigated and compared with previous studies. Four major regions of stations were identified based on principal component analysis and clustering techniques: Amazon, central Pacific, southern Pacific and Titicaca basins. Statistically significant trend patterns showed that the annual total rainfall has decreased in the Amazon basin, despite the increase in the number of rainy days and some extreme rainfall indices. Decrease in 1‐day and 5‐day yearly maximum rainfall was observed in central Pacific, along with an increase in the number of wet days. Positive trends in indices related to the intensity of very strong daily rainfall were detected in southern Pacific. Titicaca basin showed an increase in the intensity of rainfall extremes. Rainfall variability and trends were evaluated during contrasting El Niño‐Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). Most stations in the CSPA exhibited positive (negative) anomaly of total and extreme rainfall indices (consecutive dry days) during La Niña (El Niño) years. Positive (negative) anomalies of annual total rainfall and consecutive dry days during positive (negative) PDO occurred in the Amazon, southern Pacific and Titicaca basins, respectively. The ENSO–PDO conditions may have influenced the complex and mostly non‐statistically significant long‐term trends in CSPA. [ABSTRACT FROM AUTHOR]

ABSTRACT: Understanding the effects of climate change and global warming on the South Asian summer monsoon rainfall trend is critically important for millions of inhabitants of this region. This study investigates seasonal (June–September) rainfall trend over the Indo‐Pakistan subcontinent by using 36 climate model outputs from the World Climate Research Programme's Coupled Model Inter‐comparison Project Phase 5. The historical (1951–2005) and future (2006–2100) simulations under two representative concentration pathways (RCPs), RCP4.5 and RCP8.5, are analysed for this purpose. Model reproducibility is evaluated based on spatial correlation of seasonal rainfall and vertically integrated meridional moisture transport between simulated and observed fields. It is found that the majority of models shows reasonable skill in capturing the observed pattern of rainfall climatology and trend over the subcontinent. Our results showed that the models are more skilful in simulating seasonal mean moisture transport than trend over the Arabian Sea and Bay of Bengal. Of the 36 models analysed, only two models HadGEM2‐AO and CNRM‐CM5 closely approximate both the climatology and trend based on statistical performance metrics. Our results suggest that the strengthening of northwards moisture transport over the Arabian Sea and Bay of Bengal is a likely reason for the increasing rainfall trend over Indo‐Pakistan subcontinent in a warmer climate. The RCP8.5 indicates marked increase in both rainfall and moisture transport trends compared to RCP4.5 forcing scenario. [ABSTRACT FROM AUTHOR]

The study of regional rainfall trends over South Asia is critically important for food security and economy, as both these factors largely depend on the availability of water. In this study, South Asian summer monsoon rainfall trends on seasonal and monthly (June-September) time scales have been investigated using three observational data sets. Our analysis identify a dipole-type structure in rainfall trends over the region north of the Indo-Pak subcontinent, with significant increasing trends over the core monsoon region of Pakistan and significant decreasing trends over the central-north India and adjacent areas. The dipole is also evident in monthly rainfall trend analyses, which is more prominent in July and August. We show, in particular, that the strengthening of northward moisture transport over the Arabian Sea is a likely reason for the significant positive trend of rainfall in the core monsoon region of Pakistan. In contrast, over the central-north India region, the rainfall trends are significantly decreasing due to the weakening of northward moisture transport over the Bay of Bengal. The leading empirical orthogonal functions clearly show the strengthening (weakening) patterns of vertically integrated moisture transport over the Arabian Sea (Bay of Bengal) in seasonal and monthly interannual time scales. The regression analysis between the principal components and rainfall confirm the dipole pattern over the region. Our results also suggest that the extra-tropical phenomena could influence the mean monsoon rainfall trends over Pakistan by enhancing the cross-equatorial flow of moisture into the Arabian Sea. [ABSTRACT FROM AUTHOR]

The aim of the present study is to examine the trends in magnitude and intensity of precipitation and peak floods of different magnitudes for seven major river basins in India. Data pertaining to daily flows for about 30-odd years and precipitation for 61 years (from 1951 to 2012) were analysed. Linear trends were calculated for the number of rainy days, rainfall intensity and occurrence of flood peaks for all basins. Using the Sen’s slope estimator, it was found that annual peak rainfall increases for most of the basins in India. From the Mann–Kendall test and Sen’s slope, it was found that the Cauvery and Brahamani and Baitarani basins show a rising trend in the number of rainy days, but the trend was falling for five other basins. When the basins were classified as mountains and plains, it was found that the number of daily rainfall events of different magnitudes was more in the mountains compared to the plains. The rivers which flow from west to east direction have more rainy days compared to those which flow towards the west. It was observed that in general the number of rainy days was falling while the number of intense events was increasing. The number of flood peaks of smaller magnitude in different decades showed slight falling trend. It was also found that there was falling or no trend for severe floods. Anthropogenic activities (construction of storage reservoirs, diversions, urbanization, land-use change, and soil and water conservation measures, etc.) have probably affected the generation of peak floods in the rivers of India. River regulation through storage reservoirs in the past 50 years has resulted in the reduction of peak flows. Hence with the same rainfall, the flood peaks would have increased under virgin conditions. [ABSTRACT FROM AUTHOR]

The aim of this study is to update the analysis of historical rainfall trends with reference to the work from previous studies, through optimizing the highest spatial resolution with the longest possible period of analysis, i.e., 1921-2015. Two interlinked datasets, namely the district rainfall and individual rainfall stations datasets were used for the trend analyses, namely, daily time series of 60 individual rainfall stations and the daily district rainfall of 88 of 94 rainfall districts in South Africa. The extreme precipitation indices defined by the World Meteorological Organization Expert Team on Climate Change Detection and Indices were applied. In general, the results show an increase in rainfall for most rainfall stations in the southern interior of South Africa, and indications of decreases in rainfall in the far northern and north-eastern parts. The increase in the annual rainfall in the south is reflected in the seasonal trends, where summer rainfall shows a similar increase, but also extends into the central interior. For other seasons, most of the country shows no significant historical trends in annual total rainfall. From the extreme rainfall analyses, an increase in daily rainfall extremes in the southern to western interior is apparent. Also, most of the country experienced increases in the intensity of daily rainfall, which confirms global results in general. Decreases in rainfall from wet spells were noted in most places over the east and north-east, while the southern and eastern parts along the escarpment experienced shorter annual dry spells. This study improves on previous studies in the region by more than doubling the analysis period, largely eliminating the influence that decadal-scale cycles might have on analyses over shorter periods. However, some differences in the trend results compared to previous studies are apparent, e.g., less pronounced drying in the east and the previously observed increase in rainfall in the western and southern interior not extending as far as the south-western Cape. The observed trends broadly confirm those of projected changes in summer rainfall, i.e., an increase in the west and decrease in the east. [ABSTRACT FROM AUTHOR]

The current study was conducted to examine the impact of climate change on rainfall in Jharkhand state of India. It deals with the analysis of the historical spatiotemporal variability of rainfall on the annual, seasonal and monthly scale in 18 districts of the state Jharkhand over a period of 102 years (1901-2002). Mann-Kendall trend test and Sen's slope method were applied to detect trends and the magnitude of change over the time period of 102 years (1901-2002). Mann Whitney Pettit's method and Cumulative deviations test were applied for detection of shift point in the series. The results obtained year 1951 to be the most probable shift point in annual rainfall. The trend analysis along with the percent change for the data series before (1901-1951) and after the shift point (1952-2002) was also done. A significant downward rainfall trend was found in annual, monsoon and winter rainfall over the period of 102 years. The maximum decrease was found for the Godda (19.77%) and minimum at Purbi Singhbum station (1.95%). Trend analysis before shift point, i.e., during 1901-1951 showed an upward trend in annual rainfall and after shift point (1952-2002) a downward trend. The trend analysis for entire Jharkhand demonstrated a significant downward trend in annual and monsoon rainfall with a decrease of 14.11% and 15.65% respectively. A downward trend in seasonal rainfall will have a more pronounced effect on agricultural activities in the area as it may affect the growth phase of the kharif crops (May-October) in the region. [ABSTRACT FROM AUTHOR]

The coastlines have been identified as the most vulnerable regions with respect to hydrological hazards as a result of climate change and variability. The east of peninsular Malaysia is not an exception for this, considering the evidence of heavy rainfall resulting in floods as an annual phenomenon and also water scarcity due to long dry spells in the region. This study examines recent trends in rainfall and rainfall- related extremes such as, maximum daily rainfall, number of rainy days, average rainfall intensity, heavy rainfall days, extreme rainfall days, and precipitation concentration index in the east coast of peninsular Malaysia. Recent 40 years (1971-2010) rainfall records from 54 stations along the east coast of peninsular Malaysia have been analyzed using the non-parametric Mann-Kendall test and the Sen's slope method. The Monte Carlo simulation technique has been used to determine the field significance of the regional trends. The results showed that there was a substantial increase in the annual rainfall as well as the rainfall during the monsoon period. Also, there was an increase in the number of heavy rainfall days during the past four decades. [ABSTRACT FROM AUTHOR]

Jordan, with limited rainfall, has per capita water availability of 135 m3/yr making it one of the water-poorest countries in the world. We analyzed the most comprehensive modern rainfall data set to date, consisting of 44 years of daily measurements from 58 stations primarily in the western, populated and agricultural portion of Jordan over the period 1970-2013 to assess temporal trends, variability, and spatial patterns. From 1995 to 2013, 13 of 19 years showed rainfall less than the mean, which has a probability <8.35% of chance occurrence. We used nonparametric statistical analysis and found 38 of 58 stations experienced an annual rainfall decrease at an average rate of 1.2 mm/yr. Over all 58 stations, the average decrease was 0.41 mm/yr. The annual coefficient of variation of daily rainfall showed a long-term increase of ∼2-3% at 90% of stations. Analysis of annual variance of daily rainfall suggests decreasing variance in the low rainfall areas to the southwest and east and increasing variance in the high rainfall areas to the northwest, a pattern consistent with principal component analysis. Strict multiple hypothesis testing procedures using the k-familywise error rate approach reinforced and confirmed the statistically significant regional rainfall decline as well as the spatial patterns of increasing and decreasing rainfall variability. [ABSTRACT FROM AUTHOR]

In the literature, there is substantial evidence presented of enhancement of vegetation growth and regrowth with rainfall. There is also much research presented on the decline in rainfall with land clearance. This article deals with the well documented decline in rainfall in south west Western Australia and discusses the literature that has been presented as to the rationale for the decline. The original view was that it was the result of climate change. More recent research points to the compounding effect of land use change. In particular, one study estimated, through simulation work with atmospheric models, that up to 50% of the decline could be attributed to land use change. For South Australia, there is an examination the pattern of rainfall decline in one particular region, using Cummins on the Eyre Peninsula as an example location. There is a statistically significant decrease in annual rainfall over time in that location. This is mirrored for the vast majority of locations studied in South Australia, most probably having the dual drivers of climate and land use change. Conversely, it is found that for two locations, Murray Bridge and Callington, southeast of Adelaide, there is marginal evidence for an increase in annual rainfall over the last two decades, during which, incidentally, Australia experienced the most severe drought in recorded history. The one feature common to these two locations is the proximity to the Monarto plateau, which lies between them. It was the site of extensive revegetation in the 1970s. It is conjectured that there could be a connection between the increase in rainfall and the revegetation, and there is evidence presented from a number of studies for such a connection, though not specifically relating to this location. [ABSTRACT FROM AUTHOR]

Understanding precipitation variations on various timescales and their correlations is important for assessment of flood risk and utilization of water resources. In this study, the spatial and temporal patterns of precipitation concentration in the upper reaches of the Huai River, China, were investigated using two indices: the precipitation concentration index (PCI) and the concentration index (CI) for measuring seasonality and daily heterogeneity using monthly and daily precipitation series, respectively. In particular, the trends of PCI and CI were tested by the Mann-Kendall method, and relationship among PCI, CI and percentage of precipitation contributed by the rainiest days was analyzed by the linear correlation analysis. The results show a significant seasonality of the rainfall distribution and very in homogeneous temporal distribution of the daily rainfall in the south part of the study area, especially in the three reservoirs. Positive trends in the PCI and CI were found at most stations, although none of the PCI trends were statistically significant. Daily heterogeneity of the rainfall in a year is highly correlated with the heavy rainfall amount of the 15 % rainiest days, and seasonality in rainfall distribution over a year can be partly explained by the daily rainfall heterogeneity. [ABSTRACT FROM AUTHOR]

A study of long-term rainfall trends in Spain over the last 90 years has been made on the basis of 66 long-time series following data and homogeneity checks. These data series were employed to analyse mean rainfall trends in Spain and in the Atlantic and Mediterranean basins. The study continued with an analysis of series trends in yearly totals together with their spatial distribution and was completed with an examination of monthly trends. [ABSTRACT FROM AUTHOR]

The objective of this work is to study rainfall variability in different timescales in central Argentina. Rainfall trends were maximum in summer in the west of the study region, showing rainfall decrease in the west and recent period. 15, 23 and 30 years significant cycles were detected. The interannual summer rainfall variability was study in 3 sub-regions, based on the comparison of the atmospheric and oceanic variables behavior in years with deficit and excess of rainfall. The geopotential height was the best discriminator variable. Rainfall greater than normal was associated with the weakness of the Pacific heights and lows and the intensification of the Atlantic heights in the region next to the continent. The central Pacific Ocean water warming (positive phase of ENSO-El Niño Southern Oscillation) was another factor related to rainfall all over the area. A multiple linear regression model was developed and explained the 43,3% of the summer rainfall variance. [ABSTRACT FROM AUTHOR]

Over the past 40 years there have been significant changes in Australian rainfall with increases in the north-west and decreases in the east. Tropical cyclones (TCs) and other closed low pressure systems are important synoptic systems that provide a large proportion of Australia's annual rainfall. This study examines the proportion of rainfall that can be attributed to TCs over the 1970-2009 period, and to TCs combined with other closed lows over the 1989-2009 period. The contribution of these systems to Australian rainfall trends is also analysed. Tropical cyclones are found to have little influence on rainfall trends over the full time period. However, when the more recent 21-year period is considered, TCs and other closed low pressure systems can partially explain the positive rainfall trend in the north-west. Similarly, other closed low pressure systems, such as cut-off lows and east coast lows, can explain some of the negative rainfall trend in the south-east. The contribution of TCs and other closed low pressure systems to rainfall trends in the north and south-east is found to be predominantly due to respective increases and decreases in the rainfall producing efficiency of the systems. An understanding of the influence of these synoptic systems on Australian rainfall in the current climate is vital for evaluating how Australia's water budget may change in future climates. [ABSTRACT FROM AUTHOR]

Summary: High percentages of the yearly total precipitation concentration in a few very rainy days can increase the risks of floods and soil instability. In this paper, an investigation of the spatial and temporal patterns of daily and monthly precipitation concentration in Calabria (Southern Italy) has been carried out by means of a homogenous daily precipitation data set. The results show that a very dishomogeneous temporal distribution of the daily rainfall characterizes the eastern side of the region with rain gauges in which one quarter of the rainiest days represents almost three quarters of the total pluviometric amount, and a western side which presents a more homogenous temporal distribution of the rainfall. Moreover, the application of the Mann–Kendall test has shown a clear tendency toward a weaker seasonality of the rainfall distribution. [ABSTRACT FROM AUTHOR]

A new monthly precipitation database has been developed for conterminous provinces in Spain by exploiting the total amount of data available at Spanish Meteorological Agency (AEMET, formerly INM). The new MOPREDAS (monthly precipitation database of Spain) database has been constructed by using all 6821 original data series that have been recorded for at least 10 years. These provide a total of 2670 complete, homogeneous series for the period 1946-2005, and are the most complete and extensive monthly precipitation dataset available in Spain at present. MOPREDAS has been created with the aim of analysing the behaviour of precipitation in the conterminous provinces of Spain, and to help validate the downscaling of climate models on a detailed spatial level. To this end, the station data were also interpolated on a regular grid, at 1/10 of degree of resolution, over the whole Spain. Trend analysis confirms great spatial and temporal variability in the behaviour of precipitation across Spain. The monthly precipitation trends vary from month to month, from coherent spatial trend patterns in March, June (both with a general and significant negative trend) and October (general positive trends), to highly regionalized trend patterns in July (with positive trends in north-west and mainly negative in the remainder), February and April (positive and negative trends in the south-east, respectively). These results suggest that both global and local factors affect the spatial distribution of trends in the Iberian Peninsula. Mountain ranges seem to be the most significant geographical factor in determining the spatial distribution of monthly trends on a detailed, sub-regional spatial scale. These results show that it is possible to accurately delineate the areas affected by different precipitation trends if a dense spatial database is available. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Abstract: Rainfall variability is an important feature of semi-arid climates, and climate change is likely to increase that variability in many of these regions. An understanding of rainfall variability and trends in that variability is needed to help vulnerable dryland agriculturalists and policymakers address current climate variation and future climate change. The goals of this paper are to examine this climatic phenomenon in semi-arid Botswana, to investigate these results for signs of climate change, and to explore the policy implications for climate adaptation. To reach these goals, the paper determines rainfall variability and monthly and annual trends in that variability. The results agree with earlier work showing gradients in rainfall and rainfall variability across Botswana. The results also identify a trend towards decreased rainfall throughout the nation, which is associated with decreases in the number of rainy days. Both the drying trend and decrease in rainy days agree with climate change projections for southern Africa. The paper discusses policies that the government could adopt to help its farmers adapt to climate change. [ABSTRACT FROM AUTHOR]

The article presents an analysis of monthly precipitation trends in Iberian Peninsula's eastern Mediterranean fringe. The analysis show high temporal and spatial variability. Trends for winter months are prevailed by an East-West gradient with a latitudinal temporal change. Positive trends are primarily situated in coastland areas and negative ones in overriding inland.

The article reports on the study that examines the trends in Australian precipitation from 1970 to 2006 using daily rainfall dataset. The findings of the study suggested a linkage between changes in the monsoon trough and rainfall trends over northwestern Australia. It revealed a dominant change in total rainfall by trends in heavy rainfall events across the nation. It also found a decline in frequency of extreme rainfall events along the Queensland coast during summer and autumn, showing changes in the position of the precipitation distribution.

Abstract: Winter rainfall on the Iberian Peninsula presents a significant decrease in its western and central areas throughout the second half of the 20th century, whereas over the eastern fringe it shows hardly any variation. This spatial distribution of precipitation trends are related to teleconnection indices trends and changes in the frequency of surface circulation patterns over Western Europe. We determined these circulation patterns by carrying out a daily objective synoptic classification by means of a principal components analysis (PCA) using sea-level pressure (SLP) data. In order to better understand Iberian winter precipitation trends, circulation patterns are associated with those teleconnection patterns that have an important influence on Iberian rainfall: Arctic Oscillation (AO), North Atlantic Oscillation (NAO) and Western Mediterranean Oscillation (WeMO). The circulation pattern showing the biggest increases involves high pressure over Central Europe. This pattern is showing a positive AO and NAO phase, and simultaneously, a negative WeMO phase. [Copyright &y& Elsevier]

This study addresses the long-term rainfall trends, their temporal variability and uncertainty over mainland Portugal, a small country on the most western European coast. The study was based on monthly, seasonal and annual rainfall series spanning for a period of 106 years, between October 1913 and September 2019 (herein after referred to as global period), at 532 rain gauges evenly distributed over the country (c.a. 6 rain gauges per 1000 km 2 ). To understand the rainfall behavior over time, an initial sub-period with 55 years and a final sub-period with 51 years were also analyzed along with the global period. The trends identification and the assessment of their magnitude were derived using the nonparametric Mann-Kendall (MK) test coupled with the Sen's slope estimator method. The results showed that after the initial sub-period with prevailing increasing rainfall, the trends were almost exclusively decreasing. They were also so pronounced that they counterbalanced the initial rainfall increase and resulted in equally decreasing trends for the global period. The study also shows that approximately from the late 1960s on, the rainy season pattern has changed, with the last months prior to the dry season showing a sustained decrease of their relative contributions to the annual rainfalls. Overall, the results support the hypothesis of less uncertainty on the pronounced decrease of rainfall over mainland Portugal in recent years, which is expected to continue. They also show that the asymmetry between a less wet North, yet still wet, and an arid South is becoming much more marked. [ABSTRACT FROM AUTHOR]

Since several datasets are available with marked differences, the assessment of precipitation data is a key aspect to support the choice of the most adequate precipitation product for a certain research or operational application. In the present study, we evaluated the use of the daily rainfall dataset from CHIRPS with spatial resolution of 0.05° for different purposes in the states of the Brazilian Legal Amazon. We compared monthly rainfall, annual rainfall indices and their trends calculated using CHIRPS data and rain gauge observations with a point-to-pixel analysis. The use of daily CHIRPS data provided mean monthly rainfall similar to that obtained using data from the rain gauge stations, but CHIRPS data tend to underestimate the values for the rainiest months. The correlation was usually lower in the western Amazon, especially during its rainy season. The same underestimation was observed for extreme rainfall indices. CHIRPS product produces more similar results to rain gauge data for the indices PRCPTOT, nP, and R95pad, while strong underestimate the most extreme rainfall indices (R50mm, Rx1day, Rx5days). For the 45 stations and 15 rainfall indices analysed, 63 significant trends were detected using rain gauge data, of which only 13 were detected using CHIRPS product. Therefore, the use of CHIRPS data does not well represent the trends in rainfall indices. • Use of the rainfall dataset from CHIRPS for different purposes in Brazilian Amazon. • CHIRPS data tend to underestimate the rainfall for the rainiest months. • The correlation was greater for the rainy season in eastern Amazonia. • CHIRPS data underestimate the extreme rainfall indices. [ABSTRACT FROM AUTHOR]

Trend detection in hydro-climatological time series is a prime task under the context of climate changes. Rainfall is a key component of the water cycle and its variability can profoundly influence agriculture, ecosystems and water resource management. In this paper, an innovative trend analysis (ITA) method with a significant test is used for rainfall trend detection at 14 stations in the Yangtze River Delta (YRD) during 1961–2016. The trends are separately evaluated for low (<10th percentile), medium (10th–90th percentile) and high (>90th percentile) rainfall at the annual and seasonal scales. The slope and significance of the rainfall trends derived from the ITA method are compared with those from the classical trend analysis methods Theil-Sen approach and Mann-Kendall test, respectively. The ITA shows significant increasing trends at the 99% confidence level in annual rainfall at all stations. While the same significant increasing trends are identified for summer and winter, decreasing trends dominate in spring and autumn. Contrasting trends are found for extreme rainfall with strong increasing trends in high rainfall in summer and winter and decreasing trends in low rainfall in spring and autumn. The results of the ITA confirmed by the classical trend analysis methods call for more attention to the risk management of flood in extreme seasons and drought in transitional seasons across the YRD region. • Trends analysis of rainfall across the Yangtze River Delta is performed by the innovative trend analysis (ITA) method. • Separate trends in low, medium and high rainfall are quantitatively calculated based on the ITA method. • Some advantages of the ITA method to classical trend methods (Mann-Kendall test and Theil-Sen approach) are presented. • High rainfall in summer showed significant increase while low rainfall in spring and autumn exhibited decrease. [ABSTRACT FROM AUTHOR]

The present study aims at statistical analysis of pre-monsoon rainfall at Kolkata, India over a span of 45 yr (1970–2014) with special emphasis on the effect of urbanisation on pre-monsoon rainfall at Alipore, a core area of Kolkata ( 22 ∘ 34 ′ N ; 88 ∘ 24 ′ E ) India, where the urbanisation is almost static during the period 1970–2014 and Dumdum ( 22 ∘ 65 ′ N ; 88 ∘ 45 ′ E ), the outer periphery of Kolkata, where the urbanisation is still an ongoing process. As pre-monsoon rainfall is an effect of mesoscale convective development (horizontal dimensions 5–500 km), the two stations namely Dumdum and Alipore which are nearly 22 km apart from each other are taken into consideration in this study. To determine the possible changes in the pre-monsoon rainfall in both stations, a non-parametric Wilcoxon Signed Rank Sum test is conducted. This test reveals that the annual average pre-monsoon rainfall increased at Dumdum in post-urbanisation period, i.e., 1991–2014 compared to Alipore during the same period. It is important to note that the result of statistical analysis almost tallies with that of the geographical one. [ABSTRACT FROM AUTHOR]

Understanding rainfall pattern in the face of increased climate variability and change is crucial in determining management strategies for the associated risks. Analysis was performed for a 50-year rainfall data (1961-2010), collected on a daily basis from a meteorological station located in central Marsabit, northern Kenya. The data was computed for yearly rainfall pattern and changes in the yearly number of rainy and dry days. The results showed a reduction in yearly rainfall totals by more than 500mm and an increase in the yearly number of dry days by 19.6. The pattern is likely to affect crop and livestock production unless adaptation measures are identified and supported. [ABSTRACT FROM AUTHOR]