scholarly journals Projected future daily characteristics of African precipitation based on global (CMIP5, CMIP6) and regional (CORDEX, CORDEX-CORE) climate models

2021 ◽  
Author(s):  
Alessandro Dosio ◽  
Martin W. Jury ◽  
Mansour Almazroui ◽  
Moetasim Ashfaq ◽  
Ismaila Diallo ◽  
...  
Keyword(s):  
East Africa ◽  
Southern Africa ◽  
Climate Models ◽  
Precipitation Intensity ◽  
Regional Models ◽  
The West ◽  
Precipitation Frequency ◽  
Global Models ◽  
Dry Spells ◽  
Precipitation Characteristics

AbstractWe provide an assessment of future daily characteristics of African precipitation by explicitly comparing the results of large ensembles of global (CMIP5, CMIP6) and regional (CORDEX, CORE) climate models, specifically highlighting the similarities and inconsistencies between them. Results for seasonal mean precipitation are not always consistent amongst ensembles: in particular, global models tend to project a wetter future compared to regional models, especially over the Eastern Sahel, Central and East Africa. However, results for other precipitation characteristics are more consistent. In general, all ensembles project an increase in maximum precipitation intensity during the wet season over all regions and emission scenarios (except the West Sahel for CORE) and a decrease in precipitation frequency (under the Representative Concentration Pathways RCP8.5) especially over the West Sahel, the Atlas region, southern central Africa, East Africa and southern Africa. Depending on the season, the length of dry spells is projected to increase consistently by all ensembles and for most (if not all) models over southern Africa, the Ethiopian highlands and the Atlas region. Discrepancies exist between global and regional models on the projected change in precipitation characteristics over specific regions and seasons. For instance, over the Eastern Sahel in July–August most global models show an increase in precipitation frequency but regional models project a robust decrease. Global and regional models also project an opposite sign in the change of the length of dry spells. CORE results show a marked drying over the regions affected by the West Africa monsoon throughout the year, accompanied by a decrease in mean precipitation intensity between May and July that is not present in the other ensembles. This enhanced drying may be related to specific physical mechanisms that are better resolved by the higher resolution models and highlights the importance of a process-based evaluation of the mechanisms controlling precipitation over the region.

scholarly journals Evaluation of Modeled Precipitation in Oceanic Extratropical Cyclones Using IMERG

2019 ◽  
Vol 33 (1) ◽  
pp. 95-113 ◽  
Author(s):  
Catherine M. Naud ◽  
Jeyavinoth Jeyaratnam ◽  
James F. Booth ◽  
Ming Zhao ◽  
Andrew Gettelman
Keyword(s):  
Climate Models ◽  
Extratropical Cyclone ◽  
High Temporal Resolution ◽  
Extratropical Cyclones ◽  
Precipitation Frequency ◽  
Precipitation Characteristics ◽  
Satellite Retrievals ◽  
Precipitation Changes ◽  
Western Half ◽  
Eastern Half

ABSTRACT Using a high-spatial- and high-temporal-resolution precipitation dataset, Integrated Multi-satellite Retrievals for GPM (IMERG), extratropical cyclone precipitation is evaluated in two reanalyses and two climate models. Based on cyclone-centered composites, all four models overestimate precipitation in the western subsiding and dry side of the cyclones, and underestimate the precipitation in the eastern ascending and moist side. By decomposing the composites into frequency of occurrence and intensity (mean precipitation rate when precipitating), the analysis reveals a tendency for all four models to overestimate frequency and underestimate intensity, with the former issue dominating in the western half and the latter in the eastern half of the cyclones. Differences in frequency are strongly dependent on cyclone environmental moisture, while the differences in intensity are strongly impacted by the strength of ascent within the cyclone. There are some uncertainties associated with the observations: IMERG might underreport frozen precipitation and possibly exaggerate rates in vigorously ascending regions. Nevertheless, the analysis suggests that all models produce extratropical cyclone precipitation too often and too lightly. These biases have consequences when evaluating the changes in precipitation characteristics with changes in cyclone properties: the models disagree on the magnitude of the change in precipitation intensity with a change in environmental moisture and in precipitation frequency with a change in cyclone strength. This complicates accurate predictions of precipitation changes in a changing climate.

scholarly journals Potential changes in the number of wet days and its effect on future intense and annual precipitation in northern Oman

2017 ◽  
Vol 49 (1) ◽  
pp. 237-250 ◽  
Author(s):  
Luminda Niroshana Gunawardhana ◽  
Ghazi A. Al-Rawas ◽  
Andy Y. Kwarteng ◽  
Malik Al-Wardy ◽  
Yassine Charabi
Keyword(s):  
General Circulation ◽  
Climate Models ◽  
Coastal Region ◽  
General Circulation Models ◽  
Precipitation Intensity ◽  
Annual Precipitation ◽  
Monsoon Period ◽  
Precipitation Characteristics ◽  
The Future ◽  
Precipitation Records

Abstract The changes in the number of wet days (NWD) in Oman projected by climate models was analyzed, focusing mostly on variation of precipitation intensity and its effect on total annual precipitation (PTOT) in the future. The daily precipitation records of 49 gage stations were divided into five regions. Of the five general circulation models studied, two of them were selected based on their performance to simulate local-scale precipitation characteristics. All regions studied, except the interior desert region of the country, could experience fewer wet days in the future, with the most significant decreases estimated in southern Oman. The contribution from the cold frontal troughs to the PTOT in the northeast coastal region would decrease from 85% in the 1985–2004 period to 79% during the 2040–2059 period and further decrease to 77% during the 2080–2099 period. In contrast, results depict enhanced tropical cyclone activities in the northeast coastal region during the post-monsoon period. Despite the decreases in the NWD, PTOT in all regions would increase by 6–29% and 35–67% during the 2040–2059 and 2080–2099 periods, respectively. These results, therefore, show that increases in precipitation intensity dominate the changes in PTOT.

Daily precipitation characteristics of RegCM4 and WRF in China and their interannual variations

2020 ◽  
Vol 82 ◽  
pp. 97-115
Author(s):  
X Kong ◽  
A Wang ◽  
X Bi ◽  
J Wei
Keyword(s):  
Extreme Precipitation ◽  
Climate Models ◽  
Daily Precipitation ◽  
Regional Climate ◽  
Precipitation Amount ◽  
Extreme Rainfall ◽  
Horizontal Resolution ◽  
Interannual Variations ◽  
Precipitation Frequency ◽  
Precipitation Characteristics

To evaluate and clarify the daily precipitation characteristics (i.e. amount, frequency and intensity) of the regional climate models (RCMs) in China, long-term simulations were carried out using RegCM4.5 and Weather Research and Forecasting model (WRF), which were nested within the European Centre for Medium-Range Weather Forecasts (ECMWF)’s 20th century reanalysis (ERA-20C) between 1901 and 2010. The 2 RCMs were initially run at a resolution of 50 km. Analyses mainly compared the model-simulated climatic means and interannual variations of precipitation characteristics with those of dense and high-quality station observations (STN) from 1961-2010. Both models satisfactorily reproduced the seasonal mean precipitation amount, but they overestimated its frequency and underestimated its intensity. Extreme rainfall frequency was also underestimated by both RCMs. In winter (DJF), the interannual variabilities in dry days, light precipitation and moderate precipitation were well represented by both models. However, they poorly reproduced the counterparts of extreme precipitation in winter. In summer (JJA), the 2 RCMs performed well in simulating the interannual variability of extreme precipitation. Comparably, RegCM outperformed WRF in reproducing the spatial patterns of precipitation amount, interannual variations in extreme precipitation and rain events. By contrast, WRF better represented precipitation frequency in different sub-regions overall. Moreover, when the horizontal resolution of RegCM was increased from 50 to 25 km, there was a slight improvement in the representation of precipitation amount and intensity. Our results show that RCMs perform well in reproducing actual climatic means and interannual variations of daily precipitation characteristics in China, and that high-resolution RCM simulations can produce improved results for precipitation amount and intensity.

Introduction

2018 ◽  
Author(s):  
Marina Sharpe
Keyword(s):  
West Africa ◽  
Great Lakes ◽  
East Africa ◽  
North Africa ◽  
Southern Africa ◽  
Theoretical Approach ◽  
Central Africa ◽  
Horn Of Africa ◽  
Refugee Protection

This introductory chapter begins by presenting the book’s structure in section A. Section B then delineates the book’s contours, outlining four aspects of refugee protection in Africa that are not addressed. Section C provides context, with a contemporary overview of the state of refugee protection in Africa. It also looks at the major aspects of the refugee situations in each of Africa’s principal geographic sub-regions: East Africa (including the Horn of Africa), Central Africa and the Great Lakes, West Africa, Southern Africa, and North Africa. Section D then concludes with an outline of the theoretical approach to regime relationships employed throughout the book.

Comparative Analysis or Precipitation Variation Characteristics between Subtropical Monsoon Climate and Temperate Monsoon Climate-Take Changsha and Chengde for Example

2021 ◽  
Vol 7 (5) ◽  
pp. 1113-1122
Author(s):  
Bo Chen ◽  
Shi-jun Xu ◽  
Xin-ping Zhang ◽  
Yi Xie
Keyword(s):  
Climate Change ◽  
Extreme Precipitation ◽  
Precipitation Intensity ◽  
Annual Precipitation ◽  
Wet Season ◽  
Precipitation Frequency ◽  
Extreme Precipitation Events ◽  
Average Precipitation ◽  
Autumn And Winter ◽  
Average Annual Precipitation

Using the methods of literature review, regression analysis and moving average, this paper selects the daily precipitation of Changsha and Chengde from 1951 to 1986 as samples, and analyzes the average precipitation, precipitation frequency, precipitation intensity, extreme precipitation time and other indicators of Changsha and Chengde from the perspective of interannual and seasonal changes Trends. The researches show that: the average precipitation of Changsha in the 36 years is 1151.2mm, spring is the wet season, autumn and winter are the dry seasons, and the maximum average precipitation is in spring; the average annual precipitation, precipitation frequency in spring, summer and winter, annual precipitation frequency, annual precipitation intensity and extreme precipitation events show a decreasing trend. The average annual precipitation of Chengde city is 454.1 mm, wet season in summer and dry season in spring, autumn and winter; the average annual precipitation, precipitation in four seasons, annual precipitation frequency, precipitation frequency in spring, autumn and winter, annual precipitation intensity and extreme precipitation events show a decreasing trend, while the precipitation frequency in summer shows an increasing trend. The study of regional climate change based on the time series data of this stage is of great significance to comprehensively understand the law of regional climate change and predict the future trend of climate change.

scholarly journals Divergent responses of biomass accumulation and its allocation to the altered precipitation regimes among different degraded grasslands in China

2021 ◽  
Author(s):  
Tianxue Yang ◽  
Junda Chen ◽  
Xiaoyue Zhong ◽  
Xuechen Yang ◽  
Gui Wang ◽  
...  
Keyword(s):  
Climate Models ◽  
Plant Biomass ◽  
Inorganic Nitrogen ◽  
Precipitation Amount ◽  
Soil Layer ◽  
Ecosystem Functions ◽  
Precipitation Frequency ◽  
Positive Effects ◽  
Altered Precipitation ◽  
Precipitation Regimes

Abstract Purpose Climate models predict shifts in precipitation patterns characterized by increased precipitation amount and decreased frequency for semi-arid grasslands in northeast China. However, under these novel climatic conditions, potential differences in plant biomass and its allocation among different degraded grasslands remain unclear.Methods We conducted a mesocosm experiment to test the effects of higher precipitation amount (increased by 50% from the long-term mean) and lower frequency (decreased by 50%) on plant biomass and allocation in the lightly degraded (LDG), moderately degraded (MDG), and severely degraded grasslands (SDG).Results Lower precipitation frequency promoted belowground biomass (BGB), while reducing aboveground biomass (AGB) allocation through enhancing soil water variability. Higher precipitation amount enhanced AGB in LDG and MDG, but not in SDG due to less soil inorganic nitrogen. Lower precipitation frequency weakened the positive effects of higher precipitation amount on biomass. Under altered precipitation, adjustment of AGB vs. BGB allocation was the primary biomass allocation strategy in LDG and SDG. However, to maintain water acquirement, plants in MDG preferred to adjust root vertical distribution, and allocated more roots to the deep soil layer where had a relatively stable water source. This strategy was driven by the changes in plant community composition of the dominant species in MDG.Conclusions The findings of this research emphasized the importance of considering the degradation level of grasslands when predicting the responses of the ecosystem functions to the projected changes in precipitation regime. These findings are critical for making feasible decisions for the sustainable management of degraded grasslands.

scholarly journals Changes in Winter Atmospheric Rivers along the North American West Coast in CMIP5 Climate Models

2015 ◽  
Vol 16 (1) ◽  
pp. 118-128 ◽  
Author(s):  
Michael D. Warner ◽  
Clifford F. Mass ◽  
Eric P. Salathé
Keyword(s):  
Water Vapor ◽  
North American ◽  
West Coast ◽  
American West ◽  
Climate Models ◽  
Water Vapor Transport ◽  
The West ◽  
North American West ◽  
The North ◽  
Extreme Precipitation Events

Abstract Most extreme precipitation events that occur along the North American west coast are associated with winter atmospheric river (AR) events. Global climate models have sufficient resolution to simulate synoptic features associated with AR events, such as high values of vertically integrated water vapor transport (IVT) approaching the coast. From phase 5 of the Coupled Model Intercomparison Project (CMIP5), 10 simulations are used to identify changes in ARs impacting the west coast of North America between historical (1970–99) and end-of-century (2070–99) runs, using representative concentration pathway (RCP) 8.5. The most extreme ARs are identified in both time periods by the 99th percentile of IVT days along a north–south transect offshore of the coast. Integrated water vapor (IWV) and IVT are predicted to increase, while lower-tropospheric winds change little. Winter mean precipitation along the west coast increases by 11%–18% [from 4% to 6% (°C)−1], while precipitation on extreme IVT days increases by 15%–39% [from 5% to 19% (°C)−1]. The frequency of IVT days above the historical 99th percentile threshold increases as much as 290% by the end of this century.

Taxonomy of the genus Ehrharta (Poaceae) in southern Africa: the Villosa group

Bothalia ◽  
1987 ◽  
Vol 17 (2) ◽  
pp. 191-194 ◽  
Author(s):  
G. E. Gibbs Russell
Keyword(s):  
Southern Africa ◽  
West Coast ◽  
Far East ◽  
Sandy Soils ◽  
Species Group ◽  
Southern Coast ◽  
Succulent Karoo ◽  
The West

The Villosa species group in the genus  Ehrharta Thunb. is differentiated morphologically by very large, profusely hairy, bearded and aristate spikelets and by a suffrutescent habit, with culms woody at the base and with reduced leaf blades. The Villosa group is composed of two species, one with a variety: E. thunbergii Gibbs Russell, nom. nov., E. villosa Schult. f. var.  villosa and E. villosa var. maxima Stapf. Members of the group occur on sandy soils in the Succulent Karoo and Fynbos Biomes, along the west coast in Strandveld and on the southern coast as far east as the Fish River. Morphologically, the group appears to be related to the Calycina and Capensis groups.

scholarly journals Seasonal and diurnal variability in air pollutants and short-lived climate forcers measured at the Rwanda Climate Observatory

2018 ◽  
Author(s):  
H. Langley DeWitt ◽  
Jimmy Gasore ◽  
Maheswar Rupakheti ◽  
Katherine E. Potter ◽  
Ronald G. Prinn ◽  
...  
Keyword(s):  
Air Pollution ◽  
East Africa ◽  
Biomass Burning ◽  
Southern Africa ◽  
Ozone Concentration ◽  
Air Pollutants ◽  
Sub Saharan Africa ◽  
Pollution Transport ◽  
Diurnal Variability ◽  
Air Masses

Abstract. Air pollution is still largely unstudied in sub-Saharan Africa, resulting in a gap in scientific understanding of emissions, atmospheric processes, and impacts of air pollutants in this region. The Rwanda Climate Observatory, a joint partnership between MIT and the government of Rwanda, has been measuring ambient concentrations of key long-lived greenhouse gases and short-lived climate-forcing pollutants (CO2, CO, CH4, BC, O3) with state-of-the-art instruments on the summit of Mt. Mugogo (1.586° S, 29.566° E, 2590 m above sea level) since May 2015. Rwanda is a small, mountainous, and densely populated country in equatorial East Africa, currently undergoing rapid development but still at less than 20 % urbanization. The position and meteorology of Rwanda is such that the emissions transported from both the northern and southern African biomass burning seasons affect BC, CO, and O3 concentrations in Rwanda. Black carbon concentrations during Rwanda's two dry seasons, which coincide with the two biomass burning seasons, are higher at Mt. Mugogo than in major European cities. Higher BC baseline concentrations at Mugogo are loosely correlated with fire radiative power data for the region acquired with MODIS satellite instrument. Spectral aerosol absorption measured with a dual-spot Aethalometer also varies in different seasons, likely due to change in types of fuel burned and direction of pollution transport to the site. Ozone concentration was found to be higher in air masses from southern Africa than from northern Africa during their respective biomass burning seasons. These higher ozone concentration in air masses from the south could be indicative of more anthropogenic emissions mixed with the biomass burning emissions from southern Africa as Rwanda is downwind of major East African capital cities in this season. During the rainy season, local emitting activities (e.g., cooking, transportation, trash burning) remain steady, regional biomass burning is low, and transport distances are shorter as rainout of pollution occurs regularly. Thus local pollution at Mugogo can be estimated during this time period. Understanding and quantification of the percent contributions of regional and local emissions is essential to guide policy in the region. Our measurements indicate that air pollution is a current and growing problem in equatorial East Africa that deserves immediate attention.

scholarly journals The potential value of seasonal forecasts in a changing climate in southern Africa

2014 ◽  
Vol 18 (4) ◽  
pp. 1525-1538 ◽  
Author(s):  
H. C. Winsemius ◽  
E. Dutra ◽  
F. A. Engelbrecht ◽  
E. Archer Van Garderen ◽  
F. Wetterhall ◽  
...  
Keyword(s):  
Climate Change ◽  
Heat Stress ◽  
Southern Africa ◽  
Weather Conditions ◽  
Stress Conditions ◽  
Mitigation Measures ◽  
Seasonal Forecasts ◽  
Weather Forecasts ◽  
Dry Spells ◽  
The Future

Abstract. Subsistence farming in southern Africa is vulnerable to extreme weather conditions. The yield of rain-fed agriculture depends largely on rainfall-related factors such as total seasonal rainfall, anomalous onsets and lengths of the rainy season and the frequency of occurrence of dry spells. Livestock, in turn, may be seriously impacted by climatic stress with, for example, exceptionally hot days, affecting condition, reproduction, vulnerability to pests and pathogens and, ultimately, morbidity and mortality. Climate change may affect the frequency and severity of extreme weather conditions, impacting on the success of subsistence farming. A potentially interesting adaptation measure comprises the timely forecasting and warning of such extreme events, combined with mitigation measures that allow farmers to prepare for the event occurring. This paper investigates how the frequency of extreme events may change in the future due to climate change over southern Africa and, in more detail, the Limpopo Basin using a set of climate change projections from several regional climate model downscalings based on an extreme climate scenario. Furthermore, the paper assesses the predictability of these indicators by seasonal meteorological forecasts of the European Centre for Medium-Range Weather Forecasts (ECMWF) seasonal forecasting system. The focus is on the frequency of dry spells as well as the frequency of heat stress conditions expressed in the temperature heat index. In areas where their frequency of occurrence increases in the future and predictability is found, seasonal forecasts will gain importance in the future, as they can more often lead to informed decision-making to implement mitigation measures. The multi-model climate projections suggest that the frequency of dry spells is not likely to increase substantially, whereas there is a clear and coherent signal among the models of an increase in the frequency of heat stress conditions by the end of the century. The skill analysis of the seasonal forecast system demonstrates that there is a potential to adapt to this change by utilizing the weather forecasts, given that both indicators can be skilfully predicted for the December–February season, at least 2 months ahead of the wet season. This is particularly the case for predicting above-normal and below-normal conditions. The frequency of heat stress conditions shows better predictability than the frequency of dry spells. Although results are promising for end users on the ground, forecasts alone are insufficient to ensure appropriate response. Sufficient support for appropriate measures must be in place, and forecasts must be communicated in a context-specific, accessible and understandable format.

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