Understanding the major drivers of Ethiopian JJAS rainfall variability is crucial for monitoring climate extremes such as drought and flood events,which have serious implications for lives,livelihoods and food securit...Understanding the major drivers of Ethiopian JJAS rainfall variability is crucial for monitoring climate extremes such as drought and flood events,which have serious implications for lives,livelihoods and food security.This study investi-gates the atmospheric and oceanic mechanisms that modulate JJAS rainfall us-ing composite analysis,probability evaluation of the Z-index,and correlation analysis with leading climate drivers,including sea surface temperatures(SSTs),wind circulation,and outgoing longwave radiation(OLR).The results show that 40.3%of JJAS rainfall is normal,29.5%and 30.2%are dry and wet,respectively.Wet years have sharply increased since 1998,showing a shift in the rainfall patterns.Wind circulation analysis shows that 850 hPa westerly and 200 hPa easterly winds occur during wet years,which enhance the transport of moisture and convection,whereas dry years have their wind patterns in re-verse,suppressing rainfall.The correlation of Sea Surface Temperature with rainfall in JJAS has a very significant negative correlation(-0.8)in central and eastern Pacific SSTs,indicating La Niña enhancing rainfall and El Niño deficit it.Conversely,a significant positive correlation(0.8)in the western Pacific modulating the regional SST anomaly Ethiopian rainfall.The Nino 3.4 Index shows a significant negative relationship(-0.5 to-0.8)with Ethiopia’s JJAS rain,especially in the northeast,central,and eastern regions,the key role of the ENSO in rainfall variability.Moreover,the negative OLR anomaly and high RH,promote cloudiness and precipitation,while dry years are distinguished by the higher OLR anomaly and reduced RH,which suppress convection.These results confirm the leading influence of the El Nino-Southern Oscillation(ENSO)in controlling Ethiopian rainfall variability and suggest that monitor-ing of SST structure,particularly the Nino 3.4 Index,might enhance seasonal rainfall prediction and inform the Ethiopian climatic change strategy.Future studies should incorporate high-resolution modeling,improved observations,advanced statistics,and Machine Learning to better comprehend Ethiopia’s cli-mate extremes.展开更多
Demonstrating Effects of Current and Projected Rainfall Characteristics on Wheat yield has been investigated in Sinana district for the period 1995-2016. Data on rainfall and crop yield for the period 1995-2016 were o...Demonstrating Effects of Current and Projected Rainfall Characteristics on Wheat yield has been investigated in Sinana district for the period 1995-2016. Data on rainfall and crop yield for the period 1995-2016 were obtained from National Meteorological Agency and Sinana District Agricultural Offices, respectively. Following data quality checking, rainfall data (current and future), correlation and regression studies were analyzed using Statistical software like Instat V3.36 and SPSS V20. Downscaling the output of CSIRO-Mk3.6.0 GCM model (daily rainfall data) for RCP8.5 emission scenario using a web based software tool (Marksim GCM) for the period 2020-2049 were used to determine seasonal total rainfall and ascertain its impact on yield. This study used mean, coefficient of variation, correlation and regression analysis to ascertain the relation, cause and effect relationship between rainfall characteristics and wheat yields. The results indicated that the mean onset date of the main rainy season (JJAS) for Robe and Sinana station was June 30 and July 3. Furthermore, the results of Pearson Correlation Coefficients indicated that kiremt rainfall total (JJAS) had moderate positive relationship (r = 0.499) with wheat yield in the study area. It was also observed that nearly fifty percent of total variance of crop yield is explained jointly by kiremt rainfall total and rainy day (R2 value was 47.9%). The result of projected wheat yield indicated that there will be a slight decrease in wheat yield (qt/ha) after 2030 years due to the impact of expected weakening of kiremt rainfall total. Taking in to account the above findings, it could be suggested that the farmers’ community will be encouraged encouraged to utilize timely climate information issued from National Meteorological Agency of Ethiopia (NMA) and other centers for farm level decision to enhance their crop production.展开更多
Climate change has increased extreme events over globe and the most robust occurrences of concurrent drought and floods have become more common in Africa. This study focuses on the observed and projected analysis of r...Climate change has increased extreme events over globe and the most robust occurrences of concurrent drought and floods have become more common in Africa. This study focuses on the observed and projected analysis of rainfall extremes of consecutive dry day (CDD) and maximum monthly five day precipitation (RX5day) from Expert Team on Climate Change Detection and Indices (ETCCDI) in June-August season over Africa. The daily CORDEX Africa, reanalysis and CRU datasets were analyzed for extreme trends under RCP4.5 and RCP8.5 scenarios for the periods of 1980 to 2100. The spatiotemporal variability, trend, and magnitude of JJA seasonal rainfall performance exhibits a significant decreasing tendency over Eastern Africa compared to West Africa. The observed results of consecutive dry day (CDD) reveal that increasing trend and moreover RX5day shows that promising positive trend. Both rainfall extremes are influenced by the combined effect of large scale indexes and appear to be correlated negatively and positively with ENSO, NAO and AO. The CORDEX ensemble mean projections of JJA seasonal rainfall performance show a widespread significant change and the first mode of EOF depicts that 13.8% and 24.9% under the RCP4.5 and the highest variability is under RCP8.5 scenario. The projected CDD extreme exhibit an increasing trend in the coming periods and the percentage change revealed that increasing from 25.11%, 28.02% over West and 26.49%, 31.66% East Africa under RCP4.5 and RCP8.5 scenarios respectively. This situation will exacerbate increasing of frequent and intensified drought extremes over Africa. Additionally, the future RX5day indicated that mixed trend and revealed that increasing 3.72%, 2.54% over West and decreases -16.12%, -22.47% over East Africa under RCP4.5 and RCP8.5 respectively. Generally, rainfall extremes of CDD are projected to increase and RX5day shows a mixed trend in the coming periods over Africa and calls for further verification by using high resolution datasets.展开更多
Rwanda,a landlocked agricultural country,experienced escalating climate risks since 2013 due to rising June to August(JJA)minimum temperatures(Tmin),harming farming zones,lowering yields,risking health,and threaten-in...Rwanda,a landlocked agricultural country,experienced escalating climate risks since 2013 due to rising June to August(JJA)minimum temperatures(Tmin),harming farming zones,lowering yields,risking health,and threaten-ing economy.This study examined drivers of Rwanda’s 2013 warming anom-aly that severely affected eastern/central lowlands,analyzing circulation changes(1983-2021)using multiple datasets including Enhancing National Climate Services for Rwanda(ENACTS-Rwanda),European Centre for Medium-Range Weather Forecasts Reanalysis 5th Generation(ERA5),and National Oceanic and Atmospheric Administration(NOAA)observations.Methodol-ogies included Empirical Orthogonal Function(EOF)decomposition,Mann-Kendall trend tests,Sen’s slope estimator,and composite analysis to quantify trends and atmospheric linkages.Results showed a significant post-2013 Tmin increase(+0.4˚C to+2.1˚C)exceeding maximum temperature(Tmax)trends.EOF analysis identified a dominant warming mode(72%variance,loadings to+0.872)linked to coupled processes such as increased vertical descending,in-creased 850-hPa specific humidity,increased low-level cloud cover,but re-duced precipitation,which collectively promoted nighttime warming through warm advection.The anomaly was amplified by El Niño-Southern Oscillation(ENSO)-induced Pacific warming and enhanced East African moisture transport.These findings demonstrated how local thermodynamic processes interacted with global climate,forcing them to produce extreme Tmin conditions.The results suggested adaptive strategies,including heat-resistant crop cultivation and optimized water management,could mitigate agricultural impacts.Future research should incorporate these mechanisms into regional climate models while quantifying non-meteorological contributions to observed warming trends,providing critical insights for climate resilience planning in Rwanda and sim-ilar regions.展开更多
文摘Understanding the major drivers of Ethiopian JJAS rainfall variability is crucial for monitoring climate extremes such as drought and flood events,which have serious implications for lives,livelihoods and food security.This study investi-gates the atmospheric and oceanic mechanisms that modulate JJAS rainfall us-ing composite analysis,probability evaluation of the Z-index,and correlation analysis with leading climate drivers,including sea surface temperatures(SSTs),wind circulation,and outgoing longwave radiation(OLR).The results show that 40.3%of JJAS rainfall is normal,29.5%and 30.2%are dry and wet,respectively.Wet years have sharply increased since 1998,showing a shift in the rainfall patterns.Wind circulation analysis shows that 850 hPa westerly and 200 hPa easterly winds occur during wet years,which enhance the transport of moisture and convection,whereas dry years have their wind patterns in re-verse,suppressing rainfall.The correlation of Sea Surface Temperature with rainfall in JJAS has a very significant negative correlation(-0.8)in central and eastern Pacific SSTs,indicating La Niña enhancing rainfall and El Niño deficit it.Conversely,a significant positive correlation(0.8)in the western Pacific modulating the regional SST anomaly Ethiopian rainfall.The Nino 3.4 Index shows a significant negative relationship(-0.5 to-0.8)with Ethiopia’s JJAS rain,especially in the northeast,central,and eastern regions,the key role of the ENSO in rainfall variability.Moreover,the negative OLR anomaly and high RH,promote cloudiness and precipitation,while dry years are distinguished by the higher OLR anomaly and reduced RH,which suppress convection.These results confirm the leading influence of the El Nino-Southern Oscillation(ENSO)in controlling Ethiopian rainfall variability and suggest that monitor-ing of SST structure,particularly the Nino 3.4 Index,might enhance seasonal rainfall prediction and inform the Ethiopian climatic change strategy.Future studies should incorporate high-resolution modeling,improved observations,advanced statistics,and Machine Learning to better comprehend Ethiopia’s cli-mate extremes.
文摘Demonstrating Effects of Current and Projected Rainfall Characteristics on Wheat yield has been investigated in Sinana district for the period 1995-2016. Data on rainfall and crop yield for the period 1995-2016 were obtained from National Meteorological Agency and Sinana District Agricultural Offices, respectively. Following data quality checking, rainfall data (current and future), correlation and regression studies were analyzed using Statistical software like Instat V3.36 and SPSS V20. Downscaling the output of CSIRO-Mk3.6.0 GCM model (daily rainfall data) for RCP8.5 emission scenario using a web based software tool (Marksim GCM) for the period 2020-2049 were used to determine seasonal total rainfall and ascertain its impact on yield. This study used mean, coefficient of variation, correlation and regression analysis to ascertain the relation, cause and effect relationship between rainfall characteristics and wheat yields. The results indicated that the mean onset date of the main rainy season (JJAS) for Robe and Sinana station was June 30 and July 3. Furthermore, the results of Pearson Correlation Coefficients indicated that kiremt rainfall total (JJAS) had moderate positive relationship (r = 0.499) with wheat yield in the study area. It was also observed that nearly fifty percent of total variance of crop yield is explained jointly by kiremt rainfall total and rainy day (R2 value was 47.9%). The result of projected wheat yield indicated that there will be a slight decrease in wheat yield (qt/ha) after 2030 years due to the impact of expected weakening of kiremt rainfall total. Taking in to account the above findings, it could be suggested that the farmers’ community will be encouraged encouraged to utilize timely climate information issued from National Meteorological Agency of Ethiopia (NMA) and other centers for farm level decision to enhance their crop production.
文摘Climate change has increased extreme events over globe and the most robust occurrences of concurrent drought and floods have become more common in Africa. This study focuses on the observed and projected analysis of rainfall extremes of consecutive dry day (CDD) and maximum monthly five day precipitation (RX5day) from Expert Team on Climate Change Detection and Indices (ETCCDI) in June-August season over Africa. The daily CORDEX Africa, reanalysis and CRU datasets were analyzed for extreme trends under RCP4.5 and RCP8.5 scenarios for the periods of 1980 to 2100. The spatiotemporal variability, trend, and magnitude of JJA seasonal rainfall performance exhibits a significant decreasing tendency over Eastern Africa compared to West Africa. The observed results of consecutive dry day (CDD) reveal that increasing trend and moreover RX5day shows that promising positive trend. Both rainfall extremes are influenced by the combined effect of large scale indexes and appear to be correlated negatively and positively with ENSO, NAO and AO. The CORDEX ensemble mean projections of JJA seasonal rainfall performance show a widespread significant change and the first mode of EOF depicts that 13.8% and 24.9% under the RCP4.5 and the highest variability is under RCP8.5 scenario. The projected CDD extreme exhibit an increasing trend in the coming periods and the percentage change revealed that increasing from 25.11%, 28.02% over West and 26.49%, 31.66% East Africa under RCP4.5 and RCP8.5 scenarios respectively. This situation will exacerbate increasing of frequent and intensified drought extremes over Africa. Additionally, the future RX5day indicated that mixed trend and revealed that increasing 3.72%, 2.54% over West and decreases -16.12%, -22.47% over East Africa under RCP4.5 and RCP8.5 respectively. Generally, rainfall extremes of CDD are projected to increase and RX5day shows a mixed trend in the coming periods over Africa and calls for further verification by using high resolution datasets.
文摘Rwanda,a landlocked agricultural country,experienced escalating climate risks since 2013 due to rising June to August(JJA)minimum temperatures(Tmin),harming farming zones,lowering yields,risking health,and threaten-ing economy.This study examined drivers of Rwanda’s 2013 warming anom-aly that severely affected eastern/central lowlands,analyzing circulation changes(1983-2021)using multiple datasets including Enhancing National Climate Services for Rwanda(ENACTS-Rwanda),European Centre for Medium-Range Weather Forecasts Reanalysis 5th Generation(ERA5),and National Oceanic and Atmospheric Administration(NOAA)observations.Methodol-ogies included Empirical Orthogonal Function(EOF)decomposition,Mann-Kendall trend tests,Sen’s slope estimator,and composite analysis to quantify trends and atmospheric linkages.Results showed a significant post-2013 Tmin increase(+0.4˚C to+2.1˚C)exceeding maximum temperature(Tmax)trends.EOF analysis identified a dominant warming mode(72%variance,loadings to+0.872)linked to coupled processes such as increased vertical descending,in-creased 850-hPa specific humidity,increased low-level cloud cover,but re-duced precipitation,which collectively promoted nighttime warming through warm advection.The anomaly was amplified by El Niño-Southern Oscillation(ENSO)-induced Pacific warming and enhanced East African moisture transport.These findings demonstrated how local thermodynamic processes interacted with global climate,forcing them to produce extreme Tmin conditions.The results suggested adaptive strategies,including heat-resistant crop cultivation and optimized water management,could mitigate agricultural impacts.Future research should incorporate these mechanisms into regional climate models while quantifying non-meteorological contributions to observed warming trends,providing critical insights for climate resilience planning in Rwanda and sim-ilar regions.
