Seasonal Rainfall Trends Research Articles

Impact of climate change on the rainfall pattern of Klip River catchment in Ladysmith, KwaZulu Natal, South Africa

Rainfall trend analysis has been of major focus in the past century because of the attention given to climate change by the science and engineering community. According to some latest studies, rainfall is one of the main parameters in any catchment which plays a significant role in flood frequency, flood control as well as water resources planning and management. Ladysmith town in South Africa is flooded almost every year resulting in loss of lives as well as properties and businesses. Thus, this study aimed at determining the monthly and annual rainfall pattern in relation to climate change. The monthly, seasonal and annual rainfall trends for the period 1985 – 2018 were analyzed using Mann-Kendall test and Sen’s slope estimation. Results of this study indicated a variability in seasonal rainfall, with a rainfall increase during December and January of summer months whose Mann-Kendall test results were 1.88 and 0.73, and a major decrease showed in autumn months (March, April, and May) with Mann-Kendall test values of -2.76, -3.53 and -4.09. Thus, the overall results suggest a minor significant change for both Ladysmith and upstream of the Klip river catchment. Based on the analysis, it can be concluded that climate change has an impact on the rainfall spatial pattern of the study area. This correlates well with similar analysis carried out in other areas around the world.

Spatial Patterns and Temporal Trends of Precipitation in the Punjab, Pakistan, 1981-2015

The objective of the current study is to investigate and evaluate the annual and seasonal rainfall trends and patterns of the Punjab province, Pakistan during the 1981-2015. The spatial patterns and temporal trends were identified through the Modified Mann Kendall test. Finding revealed that 13 weather stations of Punjab province have shown the statistically significant decreasing trend of annual and summer monsoon rainfall during the study period. From further investigation, the rainfall during the summer monsoon period (JJAS) found to be increased by 12.45%, similarly the rainfall during the whole of year be also increased by 18.75%. The significant decreasing trends observed with the higher percentage change in annual and monsoon rainfall for the stations of Sialkot and Lahore in the northern and central Punjab. The empirical evidences suggested that northern Punjab gets more moisture as compared the Southern and Western Punjab. This study suggests intensive empirical research in the future to evolve further spatio-temporal trends in the rainfall pattern of Punjab.

Evaluation of district-level rainfall characteristics over Odisha using high-resolution gridded dataset (1901–2013)

In the present global warming era, exploring the regional/district-level changes in rainfall patterns/events is highly essential for understanding the diverse characteristics of rainfall, which will be value added for the policy planning for rainfed agricultural-based states like Odisha, a region that is also highly prone to flood and droughts. Since most of the global and continental scale climate studies rarely contribute for such planning of agro-economic states of India like Odisha, there is a colossal necessity for the analysis of rainfall characteristics at regional/district level. In the present study, the rainfall characteristics at district level over Odisha are extensively evaluated for winter (JF), pre-monsoon (MAM), monsoon (JJAS) and post-monsoon (OND) using India Meteorological Department high-resolution gridded rainfall analysis dataset for the period 1901–2013. The El Nino Southern Oscillation (ENSO) influence on the district-level seasonal rainfall during four distinctive seasons has also been studied. The results suggest that the frequency of various categorical rainfall events and associated seasonal rainfall patterns over Odisha is highly heterogeneous and varies from season to season in magnitude and similar statements can be highlighted for inter-annual variability and coefficient of variation. Although the seasonal rainfall time series is significantly persistent in most of the districts during all the seasons, it is manifested to the normal distribution in majority of districts only for JJAS. Statistical analysis infers that most of the districts possess reasonable abrupt changes in seasonal rainfall during mid- and late twentieth century. A significant increasing (decreasing) trend in the frequency of high-intensity (low-intensity and wet days) rainfall events over most parts of Odisha is observed for all the seasons. A notable decreasing trend in seasonal rainfall is perceived over southern districts during MAM (7–21 mm) and OND (23–49 mm), western districts during MAM (2–41 mm) and JJAS (6–309 mm) and most of the districts during JF (6–46 mm), while increasing trend is prominent over coastal and northern Odisha during MAM (7–46 mm), northern coastal Odisha during JJAS (25–175 mm), northern and northern coastal Odisha during OND (2–64 mm). It has been noticed that the ENSO influence on seasonal rainfall is insignificant during summer monsoon, while it is notable during the other seasons. This study is very useful in determining the effects and assists the risk management for various sectors in acclimating innovative technologies for a sustainable future in the present global warming era.

Seasonal Rainfall Variability and Trend over Kerala

Seasonal Rainfall Variability and Trend over Kerala

Analysis of long-term rainfall trends and change point in West Bengal, India

In this study, an attempt has been made to analyze long-term annual and seasonal rainfall trends along with change point of annual rainfall in West Bengal, India for 102 years (1901 to 2002) using monthly rainfall data of 18 rainfall stations. The Mann-Kendall test is used to identify trend in rainfall time series and Theil-Sen’s slope estimator to assess the magnitude of this trend. Trend-free pre-whitening method is used to eliminate the influence of significant lag-1 correlation from the series. Change in magnitude is derived in terms of percentage change over mean rainfall. Pettitt-Mann-Whitney and standard normal homogeneity test have been used to identify change point of annual rainfall. The results show that significant trend is found at five stations in annual rainfall, six stations in monsoon rainfall, and eight stations in postmonsoon rainfall. Maldah station has recorded highest negative change in magnitude in annual (− 14%) as well as monsoon rainfall (− 20.48%). South 24 Parganas rainfall station exhibits highest positive change in magnitude in annual (+ 13.98%) and monsoon (+ 13.27%) rainfall. Postmonsoon rainfall portrays positive change in magnitude at 16 rainfall stations with highest change in Birbhum station (+ 40.07%). Three most probable change point years of annual rainfall, viz. 1956, 1967, and 1952 have been observed for the rainfall stations situated in northern, southern, and western part in West Bengal. In the post change point period, the number of rainfall stations with decreasing trend has risen in northern and western part whereas it has lessened in southern part.

Spatiotemporal variability of rainfall linked to ground water level under changing climate in northwestern region, Bangladesh

Bangladesh is one of the most climatic hazard-prone countries in the world. Rainfall in Bangladesh is highly variable which depends on each season and location. This study aims to investigate spatiotemporal variability of rainfall linked to groundwater level under changing climate in the northwestern region, Bangladesh during the period of 1976-2016 using rainfall and groundwater level data. A number of statistical approaches such as Mann-Kendall (MK) test, linear regression model, Sen’s slope estimator and Spearman’s rho (SK) test, Coefficient of Variation (CV) were employed to reveal trends and variability of rainfall and groundwater level. Additionally, wavelet transform was applied to assess temporal variability of rainfall time series in the northwestern region, Bangladesh. The results show that the annual rainfall variability was the highest in the Ishwardi station (25.39%) and the lowest was found in Rajshahi (20.70%). The MK test results reveal that the trends of annual and seasonal rainfall decreased gradually, where the highest significant decreasing trend of annual rainfall was found in Rajshahi (-2.976 mm/year) and the lowest decreasing trend was found in Syedpur (-1.278 mm/year). Furthermore, monsoon and winter seasons represent the decreasing trends of rainfall for all the stations. The results of wavelet analysis demonstrate that the monthly rainfall variance of average rainfall in the northwestern region was low from the period of 2006 to 2014, indicating the dry years. The annual and seasonal rainfall trends in the northwestern region were decreased, particularly in the recent decade. The relationship between rainfall and groundwater level indicates that rainfall was decreased and the ground water level was also declining at the same time in the study region. Interestingly, it is observed that a significant high decreasing trend of annual rainfall is found in Rangpur but the annual groundwater level depth is less increased in Rangpur at the same time.

Trend Analyses of Temperature and Rainfall and Their Response to Global CO2 Emission in Masha, Southern Ethiopia

Ethiopia is one of the most vulnerable countries to climate change and often signifies higher probabilities of droughts that have historically affected millions of farmers. The variability in rainfall patterns and drought have disrupted crop production and exacerbated food insecurity in many parts of Ethiopia. This study aimed to investigate seasonal and annual temperature and rainfall trends and their association to the global CO<sub>2</sub> emission. Temperature and rainfall data obtained from the Masha meteorological station and CO<sub>2</sub> from EDGAR 4.3.2 dataset recorded for 36 years. The Linear regression model was used to analyse seasonal temperature and rainfall trends. Pearson’s correlation coefficient employed to measure the relationship between temperature and rainfall and global CO<sub>2</sub> emission. The results showed that there were significant warming trends of seasonal and annual mean temperatures while summer season and annual rainfall significantly declined. The prediction results showed that the summer and annual mean temperatures would be significantly increased while the rainfall decreased for the next 35 years. The cumulative global CO<sub>2</sub> and annual mean temperature and rainfall were correlated significantly at P = 0.0004 and 0.006 for temperature and rainfall, respectively. The results demonstrated clearly that the increasing of temperature and the decreasing of rainfall had a direct relationship with the global CO<sub>2</sub> emissions and suggested that there should be a sound soil and water management, short season seed supply and pipe irrigation practices to reduce the future crop damage in the area.

Rainfall analysis for rain-fed farming in the Great Rift Valley Basins of Ethiopia

AbstractRainfall is the most important source of water for crop production in Ethiopia. However, its temporal and spatial variability is leading to serious food shortages and insecurity in the country. This study was aimed at investigating the characteristics of selected agroclimatic variables over the great Rift Valley regions of Ethiopia. Long term (1981–2010) climate data were analyzed for 17 stations selected based on agroecology representation. Selected descriptors for climate variability and the Mann–Kendall trend test were employed. Onset, cessation, length of growing period (LGP), water requirement satisfaction index and dry spell occurrence during the growing period were determined. The results showed low to very high rainfall variability (14–35%), LGP (20–256 days) and dry spell probability (50–100%) during the main season. Significant (P ≤ 0.05) annual and seasonal rainfall trends were observed in some stations. The probability of occurrence of a dry spell during the seasons was found to be a challenge for most of the stations in the mid and low altitude areas of the basins. Consequently, seasonal water deficit was observed in these areas which hampered crop production. Area specific recommendations are thus required based on specific challenges in the study region.

Uncertainty in Estimated Trends Using Gridded Rainfall Data: A Case Study of Bangladesh

This study assessed the uncertainty in the spatial pattern of rainfall trends in six widely used monthly gridded rainfall datasets for 1979–2010. Bangladesh is considered as the case study area where changes in rainfall are the highest concern due to global warming-induced climate change. The evaluation was based on the ability of the gridded data to estimate the spatial patterns of the magnitude and significance of annual and seasonal rainfall trends estimated using Mann–Kendall (MK) and modified MK (mMK) tests at 34 gauges. A set of statistical indices including Kling–Gupta efficiency, modified index of agreement (md), skill score (SS), and Jaccard similarity index (JSI) were used. The results showed a large variation in the spatial patterns of rainfall trends obtained using different gridded datasets. Global Precipitation Climatology Centre (GPCC) data was found to be the most suitable rainfall data for the assessment of annual and seasonal rainfall trends in Bangladesh which showed a JSI, md, and SS of 22%, 0.61, and 0.73, respectively, when compared with the observed annual trend. Assessment of long-term trend in rainfall (1901–2017) using mMK test revealed no change in annual rainfall and changes in seasonal rainfall only at a few grid points in Bangladesh over the last century.

Impact of Climate Variability on the Rice Yield in Uttar Pradesh: an Agro-Climatic Zone Based Study

In the backdrop of the established fact that the climate and agricultural produce foster a close-knit relation, the present study explores the impacts of climate variability on the rice yields across diverse agro-climatic zones of Uttar Pradesh, India. The time-series non-parametric Mann-Kendall trend test was applied to study long term (both annual and seasonal) weather and yield data sets. Minimum temperature, encompassing all the zones, was found to be increasing within the range of 0.06 to 0.44 °C per decade. The ‘kharif’ season maximum temperature trends were found increasing in most zones. In terms of annual and seasonal rainfall trends, the results were mostly non-significant, except for Bhabhar and Tarai Zone which had witnessed a very high decadal trend indicating towards the occurrences of intense rainfall events. North Eastern Plain Zone needs a special mention owing to its large number of extreme rainfall events in three categories (>50 to 100 to 150 mm/day). Considering the annual/seasonal temperature and rainfall variability in the region, the warming trend along with spatio-temporally uncertain rainfall is likely to inflict significant impact upon the rice crop. Consequently, there is a dire need to devise strategies capable of dealing with the impacts of the prevailing climate variability on rice yields in this state of India through development of suitable adaptation options for sustainable production. The continuous and rigorous studies into this field of agro-meteorology subjected to impact assessment call for international action plans that are designed in a frame of ‘bottom-up approach’ or a ‘local to regional to country level’ strategic implementation of adaptation options to sustain yields in the rice fields.

Recent intensification of the seasonal rainfall cycle in equatorial Africa revealed by farmer perceptions, satellite-based estimates, and ground-based station measurements

Smallholder farmers and livestock keepers in sub-Saharan Africa are on the frontlines of climate variability and change. Yet, in many regions, a paucity of weather and climate data has prevented rigorous assessment of recent climate trends and their causes, thereby limiting the effectiveness of forecasts and other services for climate adaptation. In rainfed systems, farmer perceptions of changing rainfall and weather patterns are important precursors for annual cropping decisions. Here, we propose that combining such farmer perceptions of trends in seasonal rainfall with satellite-based rainfall estimates and climate station data can reduce uncertainties regarding regional climatic trends. In western Uganda, a rural and climatically complex transition zone between eastern and central equatorial Africa, data from 980 smallholder households suggest distinct changes in seasonal bimodal rainfall over recent decades, specifically wetter rainy seasons and drier dry seasons. Data from three satellite-based rainfall products beginning in 1983 largely corroborate respondent perceptions over the last 10–20 years, particularly in the southernmost sites near Queen Elizabeth National Park. In addition, combining all three information sources suggests an increasing trend in annual rainfall, most prominently in the north near Murchison Falls National Park over the past two decades; this runs counter to recent research asserting the presence of a drying trend in the region. Our study is unique in evaluating and cross-validating these multiple data sources to identify climatic change affecting people in a poorly understood region, while providing insights into regional-scale climate controls.

Annual and Seasonal Rainfall Trends in an Equatorial Tropical River Basin in Malaysian Borneo

Annual and seasonal rainfall trends in the Limbang River Basin (LRB), located in the equatorial tropics of Malaysian Borneo, have been characterised through Mann-Kendall and Spearman’s Rho non-parametric tests. Rainfall from 13 rain gauge stations in the LRB for the period 1948–2016 was examined in the present study. Basic statistical analysis of rainfall in the region indicates normal distribution, low missing percentage and homogenous characteristics of precipitation. Annual and seasonal rainfall in the LRB shows spatial variation while considering different rain gauge stations. In annual rainfall, eight stations showed a decreasing trend and five stations showed an increasing trend. Rain gauge stations which showed a statistically significant increase in annual rainfall were Limbang DID (2.77 and 2.85 mm/year) and Long Napir (3.65 and 3.77 mm/year). In recognising the two annual monsoon seasons in this area, a significant increase in rainfall was noticed in Long Napir (2.79 and 2.88 mm/year) during the Southwest monsoon (SWM) period. During the Northeast monsoon (NEM), along with Long Napir (3.90 and 3.95 mm/year), Limbang DID (2.86 and 3.02 mm/year), Pandaruan (1.82 and 1.87 mm/year) and Medamit Nanga (1.93 and 2.00 mm/year) also showed a significant increase in rainfall. At the same time, a distinct trend was noticed in rainfall amounts during the inter-monsoon (IM) periods. During the first inter-monsoon month (April), seven rain gauge stations showed an increasing trend in rainfall, whereas in the second inter-monsoon month (October), nine stations showed a decreasing rainfall trend. In April, Long Napir (1.86 and 1.95 mm/year) indicated a significant increasing trend, whereas in the month of October, the rain gauge station at Ukong showed a significant decreasing trend (− 2.45 and − 2.37 mm/year). Though minor spatial changes in trend characteristics were observed among the rain gauge stations, the LRB as a whole showed a consistent increasing (significant and non-significant) trend in annual and seasonal rainfall.

Analysis of trends in rainfall and dry/wet years over a century in the Eastern Ganga Canal command

In the present study, an attempt has been made to analyse the variability and trends in annual and seasonal rainfall over the Eastern Ganga Canal command area, India. To determine the trend in annual/seasonal rainfall and rainy days, the non‐parametric Mann−Kendall test and Sen's slope method were used over daily gridded rainfall for the time period 1901–2012. The results of the trend analysis revealed a decreasing trend in annual and monsoon rainfall in the range 18.5−61.7 and 19.4−56.7 mm/decade, respectively. For annual and monsoon rainy days, the results demonstrated a decreasing trend which varied from 1.8 to 2.9 and 1.4 to 2.2 days/decade, respectively, and an increasing trend in the range 0.2−1.4 and 1.0 days/decade, respectively. A variability analysis was performed to highlight the need for selecting an appropriate confidence level in trend analysis. It was observed that the grids showing a statistically non‐significant trend at the 95% confidence level exhibit a statistically significant trend at lower confidence levels. An analysis of dry and wet years on an annual scale revealed that the chances of occurrence of a wet year are more in comparison with the chances of occurrence of a dry year in the command area by a ratio of 14:13. However, data from the last one and a half decades has a contradictory trend with higher chances of occurrence of a dry year to very minimal chances of occurrence of a wet year. Dependable rainfall at various probability levels was estimated using a gamma distribution function. It was observed that the 75% dependable weighted annual and seasonal rainfall over the command area (985.48 and 727.54 mm) was significantly different with respect to the climatic mean weighted annual and seasonal rainfall against the weighted mean annual and seasonal rainfall (1,165.93 and 901.95 mm).

Analysis of seasonal and annual rainfall trends for Ranchi district, Jharkhand, India

The aim of this study was to investigate temporal variation in seasonal and annual rainfall trend over Ranchi district of Jharkhand, India for the period (1901–2014: 113 years). Mean monthly rainfall data series were used to determine the significance and magnitude of the trend using non-parametric Mann–Kendall and Sen’s slope estimator. The analysis showed a significant decreased in rainfall during annual, winter and southwest monsoon rainfall while increased in pre-monsoon and post-monsoon rainfall over the Ranchi district. A positive trend is detected in pre-monsoon and post-monsoon rainfall data series while annual, winter and southwest monsoon rainfall showed a negative trend. The maximum decrease in rainfall was found for monsoon (− 1.348 mm year−1) and minimum (− 0.098 mm year−1) during winter rainfall. The trend of post-monsoon rainfall was found upward (0.068 mm year−1). The positive and negative trends of annual and seasonal rainfall were found statistically non-significant except monsoon rainfall at 5% level of significance. Rainfall variability pattern was calculated using coefficient of variation CV, %. Post-monsoon rainfall showed the maximum value of CV (70.80%), whereas annual rainfall exhibited the minimum value of CV (17.09%), respectively. In general, high variation of CV was found which showed that the entire region is very vulnerable to droughts and floods.

Farmers’ perspectives

PurposeUnderstanding farmers’ perceptions of how the climate is changing is vital to anticipating its impacts. Farmers are known to take appropriate steps to adapt only when they perceive change to be taking place. This study aims to analyse how African indigenous vegetable (AIV) farmers perceive climate change in three different agro-climatic zones (ACZs) in Kenya, identify the main differences in historical seasonal and annual rainfall and temperature trends between the zones, discuss differences in farmers’ perceptions and historical trends and analyse the impact of these perceived changes and trends on yields, weeds, pests and disease infestation of AIVs.Design/methodology/approachData collection was undertaken in focus group discussions (FGD) (N = 211) and during interviews with individual farmers (N = 269). The Mann–Kendall test and regression were applied for trend analysis of time series data (1980-2014). Analysis of variance and least significant difference were used to test for differences in mean rainfall data, while a chi-square test examined the association between farmer perceptions and ACZs. Coefficient of variation expressed as a percentage was used to show variability in mean annual and seasonal rainfall between the zones.FindingsFarmers perceived that higher temperatures, decreased rainfall, late onset and early retreat of rain, erratic rainfall patterns and frequent dry spells were increasing the incidences of droughts and floods. The chi-square results showed a significant relationship between some of these perceptions and ACZs. Meteorological data provided some evidence to support farmers’ perceptions of changing rainfall. No trend was detected in mean annual rainfall, but a significant increase was recorded in the semi-humid zone. A decreasing maximum temperature was noted in the semi-humid zone, but otherwise, an overall increase was detected. There were highly significant differences in mean annual rainfall between the zones. Farmers perceived reduced yields and changes in pest infestation and diseases in some AIVs to be prevalent in the dry season. This study’s findings provide a basis for local and timely institutional changes, which could certainly help in reducing the adverse effects of climate change.Originality/valueThis is an original research paper and the historical trends, farmers’ perceptions and effects of climate change on AIV production documented in this paper may also be representative of other ACZs in Kenya.

Spatiotemporal trend analysis of rainfall and temperature, and its implications for crop production

Abstract Global warming is a significant global environmental problem in the 21st century. The problem is high in developing countries, particularly sub-Saharan countries in which the majority of the population live on rainfed agriculture. The present study aimed to undertake spatiotemporal analysis of seasonal and annual rainfall and temperature and its implications. The MK test, Sen's slope and precipitation concentration index (PCI) were applied. Finally, Pearson correlation analysis between climatic variables and crop production was analysed. The Mann–Kendall test results showed that the annual and seasonal rainfall trend was highly variable. The minimum and maximum temperatures have increased by 0.8 and 1.1 °C/year, respectively. Based on PCI results, rainfall during the summer and spring seasons is moderately distributed as compared to annual and winter season rainfall. Based on these observations, the rainfall pattern and distribution of the area could be classified as irregular and erratic distribution. Results of correlation analysis between monthly and seasonal rainfall with crop production were insufficient to conclude the impact of rainfall and temperature on crop production. In view of this, the incidence of food shortage is a common occurrence. Therefore, depending on the historical trend of rainfall variability and prolonged temperature increase, appropriate coping and adaptation strategies need to be encouraged.

Spatio-temporal variation of rainfall over Bihar State, India

AbstractThis study detected, for the first time, the long term annual and seasonal rainfall trends over Bihar state, India, between 1901 and 2002. The shift change point was identified with the cumulative deviation test (cumulative sum – CUSUM), and linear regression. After the shift change point was detected, the time series was subdivided into two groups: before and after the change point. Arc-Map 10.3 was used to evaluate the spatial distribution of the trends. It was found that annual and monsoon rainfall trends decreased significantly; no significant trends were observed in pre-monsoon, monsoon, post-monsoon and winter rainfall. The average decline in rainfall rate was –2.17 mm·year−1and –2.13 mm·year−1for the annual and monsoon periods. The probable change point was 1956. The number of negative extreme events were higher in the later period (1957–2002) than the earlier period (1901–1956).

Spatial variability and temporal trends of precipitation over the Loess Plateau of China: 1957-2013

Accurate information about regional precipitation and trends in spatiotemporal variation is crucial, both from the perspective of quantifying water budgets and to determine appropriate vegetation restoration. The objectives of this study were to evaluate spatiotemporal changes in precipitation and to analyze the monthly, annual, and seasonal precipitation trends of 85 stations in the Loess Plateau during 1957−2013. The Mann−Kendall test and Sen’s slope estimator were applied to analyze the precipitation data. Monthly precipitation trends exhibited apparent regional differences over the Loess Plateau, significant increasing trends in rainfall were found in winter. On the seasonal scale, the magnitude of significant negative trends in seasonal rainfall varied from 0.595 mm/yr2 to 2.732 mm/yr2. The magnitude of significant positive trends varied from 0.010 mm/yr2 to 1.987 mm/yr2. One of the most remarkable findings was that all the stations showed significant positive trends in winter. For annual average rainfall, the magnitude of significant positive trends varied from 2.075 mm/yr2 to 3.427 mm/yr2. No significant negative trends were detected. Although, the annual average rainfall over the Loess Plateau showed a non-significant increasing trend, the seasonal and regional pattern was obvious. Such findings can provide important implications for ecological restoration and farming operations across the study region.

Analysis of rainfall trends over Indo‐Pakistan summer monsoon and related dynamics based on CMIP5 climate model simulations

ABSTRACTUnderstanding 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.

Spatio-temporal variability and trends of precipitation and extreme rainfall events in Ethiopia in 1980–2010

This article summarizes the results from an analysis conducted to investigate the spatio-temporal variability and trends in the rainfall over Ethiopia over a period of 31 years from 1980 to 2010. The data is mostly observed station data supplemented by bias-corrected AgMERRA climate data. Changes in annual and Belg (March–May) and Kiremt (June to September) season rainfalls and rainy days have been analysed over the entire Ethiopia. Rainfall is characterized by high temporal variability with coefficient of variation (CV, %) varying from 9 to 30% in the annual, 9 to 69% during the Kiremt season and 15–55% during the Belg season rainfall amounts. Rainfall variability increased disproportionately as the amount of rainfall declined from 700 to 100 mm or less. No significant trend was observed in the annual rainfall amounts over the country, but increasing and decreasing trends were observed in the seasonal rainfall amounts in some areas. A declining trend is also observed in the number of rainy days especially in Oromia, Benishangul-Gumuz and Gambella regions. Trends in seasonal rainfall indicated a general decline in the Belg season and an increase in the Kiremt season rainfall amounts. The increase in rainfall during the main Kiremt season along with the decrease in the number of rainy days leads to an increase in extreme rainfall events over Ethiopia. The trends in the 95th-percentile rainfall events illustrate that the annual extreme rainfall events are increasing over the eastern and south-western parts of Ethiopia covering Oromia and Benishangul-Gumuz regions. During the Belg season, extreme rainfall events are mostly observed over central Ethiopia extending towards the southern part of the country while during the Kiremt season, they are observed over parts of Oromia, (covering Borena, Guji, Bali, west Harerge and east Harerge), Somali, Gambella, southern Tigray and Afar regions. Changes in the intensity of extreme rainfall events are mostly observed over south-eastern parts of Ethiopia extending to the south-west covering Somali and Oromia regions. Similar trends are also observed in the greatest 3-, 5- and 10-day rainfall amounts. Changes in the consecutive dry and wet days showed that consecutive wet days during Belg and Kiremt seasons decreased significantly in many areas in Ethiopia while consecutive dry days increased. The consistency in the trends over large spatial areas confirms the robustness of the trends and serves as a basis for understanding the projected changes in the climate. These results were discussed in relation to their significance to agriculture.