scholarly journals Brief Communication: Drought Likelihood for East Africa

2017 ◽  
Author(s):  
Hui Yang ◽  
Chris Huntingford
Keyword(s):  
East Africa ◽  
Climate Models ◽  
Global Climate ◽  
Extreme Rainfall ◽  
Global Climate Models ◽  
Severe Drought ◽  
East African ◽  
Reanalysis Dataset ◽  
Weather Forecasts ◽  
Medium Range

Abstract. The on-going effects of severe drought in East Africa are causing high levels of malnutrition, hunger, illness and death. Close to 16 million people across Somalia, Ethiopia and Kenya need food, water and medical assistance (DEC, 2017). Many factors influence drought stress and ability to respond. However, inevitably it is asked: are elevated atmospheric greenhouse gas (GHG) concentrations altering the likelihood of extreme rainfall deficits? We find small increases in probability of this for East African, based on merging the observation-based reanalysis dataset by the European Centre for Medium-Range Weather Forecasts (ECMWF) (Dee et al., 2011) with Global Climate Models (GCMs) in the CMIP5 database (Taylor et al., 2012).

scholarly journals Introducing Non-Stationarity Into the Development of Intensity-Duration-Frequency Curves under a Changing Climate

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1008
Author(s):  
Daniele Feitoza Silva ◽  
Slobodan P. Simonovic ◽  
Andre Schardong ◽  
Joel Avruch Goldenfum
Keyword(s):  
Return Period ◽  
Climate Models ◽  
Global Climate ◽  
Extreme Rainfall ◽  
Value Theory ◽  
Extreme Value ◽  
Global Climate Models ◽  
Water Infrastructure ◽  
Planning And Design ◽  
Intensity Duration Frequency

Intensity-duration-frequency (IDF) relationships are traditional tools in water infrastructure planning and design. IDFs are developed under a stationarity assumption which may not be realistic, neither in the present nor in the future, under a changing climatic condition. This paper introduces a framework for generating non-stationary IDFs under climate change, assuming that probability of occurrence of quantiles changes over time. Using Extreme Value Theory, eight trend combinations in Generalized Extreme Value (GEV) parameters using time as covariate are compared with a stationary GEV, to identify the best alternative. Additionally, a modified Equidistance Quantile Matching (EQMNS) method is implemented to develop IDFs for future conditions, introducing non-stationarity where justified, based on the Global Climate Models (GCM). The methodology is applied for Moncton and Shearwater gauges in Northeast Canada. From the results, it is observed that EQMNS is able to capture the trends in the present and to translate them to estimated future rainfall intensities. Comparison of present and future IDFs strongly suggest that return period can be reduced by more than 50 years in the estimates of future rainfall intensities (e.g., historical 100-yr return period extreme rainfall may have frequency smaller than 50-yr under future conditions), raising attention to emerging risks to water infrastructure systems.

scholarly journals Brief communication: Drought likelihood for East Africa

2018 ◽  
Vol 18 (2) ◽  
pp. 491-497 ◽  
Author(s):  
Hui Yang ◽  
Chris Huntingford
Keyword(s):  
East Africa ◽  
Bias Correction ◽  
General Circulation ◽  
Climate Models ◽  
Extreme Rainfall ◽  
General Circulation Models ◽  
Medical Assistance ◽  
East African ◽  
Climatological Variability ◽  
Drought Occurrence

Abstract. The East Africa drought in autumn of year 2016 caused malnutrition, illness and death. Close to 16 million people across Somalia, Ethiopia and Kenya needed food, water and medical assistance. Many factors influence drought stress and response. However, inevitably the following question is asked: are elevated greenhouse gas concentrations altering extreme rainfall deficit frequency? We investigate this with general circulation models (GCMs). After GCM bias correction to match the climatological mean of the CHIRPS data-based rainfall product, climate models project small decreases in probability of drought with the same (or worse) severity as 2016 ASO (August to October) East African event. This is by the end of the 21st century compared to the probabilities for present day. However, when further adjusting the climatological variability of GCMs to also match CHIRPS data, by additionally bias-correcting for variance, then the probability of drought occurrence will increase slightly over the same period.

scholarly journals Increased Drought Risk in South Asia under Warming Climate: Implications of Uncertainty in Potential Evapotranspiration Estimates

2020 ◽  
Vol 21 (12) ◽  
pp. 2979-2996 ◽  
Author(s):  
Saran Aadhar ◽  
Vimal Mishra
Keyword(s):  
Soil Moisture ◽  
South Asia ◽  
Climate Models ◽  
Potential Evapotranspiration ◽  
Global Climate ◽  
Global Climate Models ◽  
Drought Risk ◽  
Severe Drought ◽  
Considerable Uncertainty ◽  
Warming Climate

AbstractObserved and projected changes in potential evapotranspiration (PET) and drought are not well constrained in South Asia. Using five PET estimates [Thornthwaite (PET-TH), Hargreaves–Samani (PET-HS), Penman–Monteith (PET-PM), modified Penman–Monteith (PET-MPM), and energy (PET-EN)] for the observed (1979–2018, from ERA5) and future warming climate, we show that significant warming has occurred in South Asia during 1979–2018. PET changes show considerable uncertainty depending on the method used. For instance, PET-TH has increased significantly while all the other four methods show a decline in PET in the majority of South Asia during the observed period of 1979–2018. The increase in PET-TH is substantially higher than PET-HS, PET-PM, and PET-MPM due to a higher (3–4 times) sensitivity of PET-TH to warming during the observed period. Under the 1.5°, 2.0°, and 2.5°C warming worlds, global climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5 GCMs) project increases in PET and drought frequency over the majority of the regions. Drought estimates based on PET-EN and PET-MPM are consistent with soil moisture–based drought estimates and project a substantial increase in the frequency of severe droughts under warming climate in South Asia. In addition, the projected frequency of severe drought based on PET-TH, which is an outlier, is about 5 times higher than PET-EN and PET-MPM. Methods to estimate PET contribute the most in the overall uncertainty of PET and drought projections in South Asia, primarily due to PET-TH. Drought estimates based on PET-TH are not reliable for the observed and projected future climate. Therefore, future drought projections should be either based on PET-EN/PET-MPM or soil moisture.

scholarly journals Historical and Projected Changes to the Stages and Other Characteristics of Severe Canadian Prairie Droughts

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3370
Author(s):  
Barrie Bonsal ◽  
Zhuo Liu ◽  
Elaine Wheaton ◽  
Ronald Stewart
Keyword(s):  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Severe Drought ◽  
Large Area ◽  
Canadian Prairie ◽  
Canadian Prairies ◽  
Temporal And Spatial Characteristics ◽  
Projected Changes ◽  
Drought Occurrence

Large-area, long-duration droughts are among Canada’s costliest natural disasters. A particularly vulnerable region includes the Canadian Prairies where droughts have, and are projected to continue to have, major impacts. However, individual droughts often differ in their stages such as onset, growth, persistence, retreat, and duration. Using the Standardized Precipitation Evapotranspiration Index, this study assesses historical and projected future changes to the stages and other characteristics of severe drought occurrence across the agricultural region of the Canadian Prairies. Ten severe droughts occurred during the 1900–2014 period with each having unique temporal and spatial characteristics. Projected changes from 29 global climate models (GCMs) with three representative concentration pathways reveal an increase in severe drought occurrence, particularly toward the end of this century with a high emissions scenario. For the most part, the overall duration and intensity of future severe drought conditions is projected to increase mainly due to longer persistence stages, while growth and retreat stages are generally shorter. Considerable variability exists among individual GCM projections, including their ability to simulate observed severe drought characteristics. This study has increased understanding in potential future changes to a little studied aspect of droughts, namely, their stages and associated characteristics. This knowledge can aid in developing future adaptation strategies.

scholarly journals A GCMs-based mathematic model for droughts prediction in the Haihe Basin, China: Multi-GCM Divide-Integration

2016 ◽  
Author(s):  
Dongmei Han ◽  
Denghua Yan ◽  
Xinyi Xu ◽  
Zhongwen Yang ◽  
Yajing Lu
Keyword(s):  
Water Resources ◽  
Spatial Scale ◽  
Climate Models ◽  
Global Climate ◽  
Mathematic Model ◽  
Global Climate Models ◽  
Annual Rainfall ◽  
Severe Drought ◽  
Data Sets ◽  
Integration Model

Abstract. Recently, the skilful prediction of climate change has drawn high attention from the scientific community. Evidence has been reported the skill of prediction is not satisfactory for the magnitude of inter-annual precipitation and extreme precipitation, and at a smaller spatial scale as well. Based on observational data sets and outputs from the Global Climate Models (GCMs), this study aims at achieving a mathematical model, named multi-GCM divide-integration model (MGDI). The MGDI model is developed by hybridizing finer spatial scale and multi-linear regression model (MLRM) on five state-of-art of GCMs to improve the skills of five GCMs, which is applied to the second level of water resources regionalization in China. It is found that the performance after MGDI model correction has been improved significantly over that of individual GCMs. The errors between observation and simulation after correction (1.6 % ~ 4.4%) are within the margin of error (smaller than 5 %) and all of the varying trends in each second level of water resources regionalization were same. Furthermore, this study also used the MGDI model to predict the variation of precipitation and droughts at different spatial scale, including second level of water resources regionalization of China and the whole HHB, for the next 40 years. Predictions indicate the climate will gradually change from drying to wetting over the HHB wherein the trend of annual rainfall is 9.3 mm/10 a. The frequency of drought events will be decreasing as time goes on. The occurrence of mild and severe drought in the Luan River and Jidong Coastal, Tuhai majia River are higher than that in other regions, 9 and 8 respectively. These findings would provide scientific support for current water resources management and future drought-resisting planning of districts in China.

scholarly journals Changes in the Risk of Extratropical Cyclones in Eastern Australia

2013 ◽  
Vol 26 (4) ◽  
pp. 1403-1417 ◽  
Author(s):  
Andrew J. Dowdy ◽  
Graham A. Mills ◽  
Bertrand Timbal ◽  
Yang Wang
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
East Coast ◽  
Global Climate ◽  
Absolute Risk ◽  
Extreme Rainfall ◽  
Global Climate Models ◽  
Extratropical Cyclone ◽  
Extratropical Cyclones ◽  
Eastern Australia

Abstract The east coast of Australia is a region of the world where a particular type of extratropical cyclone, known locally as an east coast low, frequently occurs with severe consequences such as extreme rainfall, winds, and waves. The likelihood of formation of these storms is examined using an upper-tropospheric diagnostic applied to three reanalyses and three global climate models (GCMs). Strong similarities exist among the results derived from the individual reanalyses in terms of their seasonal variability (e.g., winter maxima and summer minima) and interannual variability. Results from reanalyses indicate that the threshold value used in the diagnostic method is dependent on the spatial resolution. Results obtained when applying the diagnostic to two of the three GCMs are similar to expectations given their spatial resolutions, and produce seasonal cycles similar to those from the reanalyses. Applying the methodology to simulations from these two GCMs for both current and future climate in response to increases in greenhouse gases indicates a reduction in extratropical cyclone occurrence of about 30% from the late twentieth century to the late twenty-first century for eastern Australia. In addition to the absolute risk of formation of these extratropical cyclones, spatial climatologies of occurrence are examined for the broader region surrounding eastern Australia. The influence of large-scale modes of atmospheric and oceanic variability on the occurrence of these storms in this region is also discussed.

scholarly journals Analysis of Climate Change and 24-Hour Design Storm Depths for a Range of Return Periods Across South Carolina

2015 ◽  
pp. 70-79
Author(s):  
Derek Hutton ◽  
Nigel B. Kaye ◽  
William D. Martin
Keyword(s):  
South Carolina ◽  
Return Period ◽  
Climate Models ◽  
Global Climate ◽  
Extreme Rainfall ◽  
The State ◽  
Global Climate Models ◽  
Total Rainfall ◽  
Extreme Rainfall Events ◽  
Design Storm

A warming climate leads to a moister atmosphere and more rapid hydrologic cycle. As such, many parts of the country are predicted to experience more total rainfall per year and more frequent extreme rainfall events. Most regions of the country have stormwater systems designed to a standard that matches outflow rates to pre-development values for specified return period storms. Increases in these return period storm depths, as predicted by many global climate models, will stress existing stormwater infrastructure. This paper examines how rainfall patterns will change over the remainder of the century across the state of South Carolina. Rainfall simulations from 134 realizations of 21 global climate models were analyzed across the state of South Carolina through 2099. Results show that there will be increases in both annual total rainfall (ATR) and 24-hour design storm depth for a range of return period storms. Across South Carolina, ATR is predicted to increase by approximately 2.3-4.0 inches over the forecast period while the 100 year design storm depth is predicted to increase by 0.5-1.2 inches depending on location. However there are significant regional variations with the Savannah River Basin experiencing smaller increases in ATR compared to the rest of the state.

scholarly journals Projected climate changes in four different regions in Colombia

2019 ◽  
Vol 8 (1) ◽  
Author(s):  
Oscar D. Molina ◽  
Christian Bernhofer
Keyword(s):  
Relative Humidity ◽  
Statistical Downscaling ◽  
Minimum Temperature ◽  
Climate Models ◽  
Global Climate ◽  
Meteorological Data ◽  
Baseline Period ◽  
Global Climate Models ◽  
Reanalysis Dataset ◽  
Representative Concentration Pathways

Abstract Background Considering the lack of research over this region the Statistical Downscaling Model (SDSM) was used as a tool for downscaling meteorological data statistically over four representative regions in the eastern side of Colombia. Data from the two Global Climate Models CanESM2 and IPSL-CM5A-MR, which are part of the CMIP5-project have been used to project future maximum and minimum temperature, precipitation and relative humidity for the periods 2021–2050 and 2071–2100. For both models, the Representative Concentration Pathways RCP2.6 and RCP8.5 were considered, representing two different possible future emission trajectories and radiative forcings. Predictor variables from the National Centre for Environmental Prediction (NCEP-DOE 2) reanalysis dataset, together with analyzed correlation coefficient (R) and root mean square error (RMSE) were used as performance indicators during the calibration and validation process. Results Results indicate that Maximum and minimum temperature is projected to increase for both Global Climate Models and both Representative Concentration Pathways; relative humidity shows a decreasing trend for all scenarios and all regions; and precipitation shows a slight decrease over three regions and an increase over the warmest region. As expected, the results of the simulation for the period 2071–2100 show a more drastic change when compared to the baseline period of observations. Conclusions The SDSM model proves to be efficient in the downscaling of maximum/minimum temperature as well as relative humidity over the studied regions; while showing a lower performance for precipitation, agreeing with the results for other statistical downscaling studies. The results of the projections offer good information for the evaluation of possible future-case scenarios and decision-making management.

scholarly journals A review of droughts in the African continent: a geospatial and long-term perspective

2014 ◽  
Vol 11 (3) ◽  
pp. 2679-2718 ◽  
Author(s):  
I. Masih ◽  
S. Maskey ◽  
F. E. F. Mussá ◽  
P. Trambauer
Keyword(s):  
East Africa ◽  
Climate Models ◽  
Southern Oscillation ◽  
Global Climate ◽  
Global Climate Models ◽  
Drought Risk ◽  
African Continent ◽  
Change Models ◽  
Continental Scale ◽  
Instrumental Records

Abstract. This paper presents a comprehensive review and analysis of the available literature and information on droughts to build a continental, regional and country level perspective on geospatial and temporal variation of droughts in Africa. The study is based on the review and analysis of droughts occurred during 1900–2013 as well as evidence available from past centuries based on studies on the lake sediment analysis, tree-ring chronologies and written and oral histories and future predictions from the global climate change models. Most of the studies based on instrumental records indicate that droughts have become more frequent, intense and widespread during the last 50 yr. The extreme droughts of 1972–1973, 1983–1984 and 1991–1992 were continental in nature and stand unique in the available records. Additionally, many severe and prolonged droughts were recorded in the recent past such as the 1999–2002 drought in Northwest Africa, 1970s and 1980s droughts in West Africa (Sahel), 2010–2011 drought in East Africa (Horn of Africa) and 2001–2003 drought in Southern and Southeast Africa, to name a few. The available (though limited) evidence before the 20th century confirms the occurrence of several extreme and multi-year droughts during each century, with the most prolonged and intense droughts that occurred in Sahel and Equatorial East Africa regions. Complex and highly variant nature of many physical mechanisms such as El Niño-Southern Oscillation (ENSO), Sea Surface Temperature (SST) and land–atmosphere feedback adds to the daunting challenge of drought monitoring and forecasting. The future predictions of droughts based on global climate models indicate increased droughts and aridity at the continental scale but large differences exist due to model limitations and complexity of the processes especially for Sahel and North Africa regions. However, the available evidence from the past clearly shows that the African continent is likely to face extreme and widespread droughts in future. This evident challenge is likely to aggravate due to slow progress in drought risk management, increased population and demand for water and degradation of land and environment. Thus, there is a clear need for increased and integrated efforts in drought mitigation to reduce the negative impacts of droughts anticipated in future.

scholarly journals High-Resolution Future Projections of Temperature and Precipitation in the Canary Islands

2015 ◽  
Vol 28 (19) ◽  
pp. 7846-7856 ◽  
Author(s):  
Francisco J. Expósito ◽  
Albano González ◽  
Juan C. Pérez ◽  
Juan P. Díaz ◽  
David Taima
Keyword(s):  
Soil Moisture ◽  
Canary Islands ◽  
Climate Models ◽  
Global Climate ◽  
Statistical Significance ◽  
Coupled Model ◽  
Horizontal Resolution ◽  
Global Climate Models ◽  
Reanalysis Dataset ◽  
Temperature And Precipitation

Abstract The complex orography of the Canary Islands favors the creation of microclimates, which cannot be studied using global climate models or regional models with moderate resolution. In this work, WRF is used to perform a dynamic climate regionalization in the archipelago, using the pseudo–global warming technique to compute the initial and boundary conditions from a reanalysis dataset and from results of 14 global climate models. The simulations were performed for three decades, one at present (1995–2004) and two in the future (2045–54 and 2090–99), and for two different greenhouse gas scenarios (RCP4.5 and RCP8.5), defined in phase 5 of the Coupled Model Intercomparison Project. The obtained results, at a 5-km horizontal resolution, show a clear dependence of temperature increase with height and a positive change in diurnal temperature range, which is mainly due to a reduction in soil moisture and a slight decrease in cloud cover. This negative change in soil moisture is mainly a consequence of a decrease in precipitation, although the evaluation of simulated reduction in precipitation does not show statistical significance in most of the Canary Islands for the analyzed periods and scenarios.

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