Academic literature on the topic 'Precipitation variability Botswana'

Abstract A combination of numerous factors, including geographic position, regional orography, and local sea surface temperatures, means that subtropical southern Africa experiences considerable spatial and temporal variability in rainfall and is prone to both frequent flooding and drought events. One system that may contribute to rainfall variability in the region is the mesoscale convective complex (MCC). In this study, Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) data is used to document the precipitation produced by MCCs over southern Africa for the 1998–2006 period. Most of the rainfall associated with MCCs is found to occur over central Mozambique, extending southward to eastern South Africa. High precipitation totals associated with these systems also occur over the neighboring southwest Indian Ocean, particularly off the northeast coast of South Africa. MCCs are found to contribute up to 20% of the total summer rainfall (November–March) in parts of the eastern region of southern Africa. If the month of March is excluded from the analysis, then the contribution increases up to 24%. In general, the MCC summer rainfall contribution for most of the eastern region is approximately between 8% and 16%. Over the western interior and Botswana and Namibia, the MCC contribution is much less (<6%). It is also evident that there is considerable interannual variability associated with the contribution that these systems make to the total warm season rainfall.

This articles presents a new series of maps showing the climate and environmental variability of Botswana. Situated in southern Africa, Botswana has an arid to semi-arid climate, which significantly varies in its different regions: Kalahari Desert, Makgadikgadi Pan and Okavango Delta. While desert regions are prone to droughts and periods of extreme heat during the summer months, other regions experience heavy downpours, as well as episodic and unpredictable rains that affect agricultural activities. Such climatic variations affect social and economic aspects of life in Botswana. This study aimed to visualise the non-linear correlations between the topography and climate setting at the country’s scale. Variables included T °C min, T °C max, precipitation, soil moisture, evapotranspiration (PET and AET), downward surface shortwave radiation, vapour pressure and vapour pressure deficit (VPD), wind speed and Palmer Drought Severity Index (PDSI). The dataset was taken from the TerraClimate source and GEBCO for topographic mapping. The mapping approach included the use of Generic Mapping Tools (GMT), a console-based scripting toolset, which enables the use of a scripting method of automated mapping. Several GMT modules were used to derive a set of climate parameters for Botswana. The data were supplemented with the adjusted cartographic elements and inspected by the Geospatial Data Abstraction Library (GDAL). The PDSI in Botswana in 2018 shows stepwise variation with seven areas of drought: (1) −3.7 to −2.2. (extreme); (2) −2.2 to −0.8 (strong, southern Kalahari); (3) −0.8 to 0.7 (significant, central Kalahari; (4) 0.7 to 2.1 (moderate); (5) 2.1 to 3.5 (lesser); (6) 3.5 to 4.9 (low); (7) 4.9 to 6.4 (least). The VPD has a general trend towards the south-western region (Kalahari Desert, up to 3.3), while it is lower in the north-eastern region of Botswana (up to 1.4). Other values vary respectively, as demonstrated in the presented 12 maps of climate and environmental inventory in Botswana.

Increasing water scarcity in the Southern African Development Community (SADC) region has underscored the need to improve our understanding of the management of water resources. Using total evapotranspiration (TET) and precipitation (P) data of the past 16 years this study used a modified version of the climate moisture index (CMI) in order to evaluate water scarcity throughout the SADC region, by examining the relative importance of P and TET on the variability of the CMI. The CMI value for the Democratic Republic of Congo (CMIDRC = 0.347) as well as for Angola (CMIAngola = 0.351), ranged between 0.25 and 1, characteristic of a humid region, whereas CMI values for Botswana (CMIBotswana = 0.027) and South Africa (CMISouth Africa = 0.075) ranged between −0.6 and 0 or 0 and 0.25, characteristic of semi-arid to sub-humid regions. Namibia (CMINamibia = −0.125) has been experiencing drier conditions. The findings of this linear correlation analysis confirm a strong and significant relationship between DRC-Angola (r = 0.837), and a weak but significant relationship between Botswana–Namibia (r = 0.554) and South Africa–Namibia (r = 0.445) with regard to CMI, and suggest the possibility of transferring water from wetter to drier regions in the SADC study area.

Abstract Smallholder farmers are particularly vulnerable to the effects of climate change and variability in semiarid contexts. Despite the limited adaptation options often used and the largely subsistence agriculture practiced, studies have shown that smallholders have accumulated local knowledge about changes in climatic conditions. Farmers with field experience and an extensive stay in three sites in Palapye, eastern Botswana, were interviewed. This study related farmers’ perceptions of changes in climate with results from analysis of climate data. Major changes perceived are a reduction in rainfall amount, rising temperature, and increasing frequency of drought conditions. Perceived reduction in rainfall amount is confirmed by analysis results as variability in rainfall amount is high throughout the series. Rainfall was poorly distributed and below average at the beginning of the cropping seasons for four years between 2013 and 2017. For 1990, 2003, and 2012, the standardized precipitation index (SPI) was −1.77 (severe drought), −1.37 (moderate drought), and −2.32 (extreme drought), respectively. To minimize impacts on crop production, farmers simultaneously planted different crops based on the perception that climatic impacts on different crops vary and favored crops perceived as drought resistant. Livestock farmers supplemented with livestock feeds, reduced herd size, and moved livestock to areas with better forage. Off-farm incomes from selling products harvested from the wild are important to farmers as a coping strategy, particularly when rain fails. Some female farmers brewed and sold alcohol made locally from sorghum. That local knowledge and perceptions exist and are used by smallholder farmers to adapt to climate change and variability is suggested. Engaging with local knowledge systems is an imperative for climate change policy making.

<div> <p>Water balance studies in the Okavango Delta indicate that more than 90% of inflow into the Delta is lost through evaporation. This coupled with high climatic variability threatens the ecohydrology of the Delta. Trends indicate decreasing rainfall amounts and increasing temperature at the area of the Delta. The main aim of this study was therefore to investigate long term trends and variability in rain onset, cessation, number of rainy days and their impact on the dryness index at the Delta. The impact of the above variables is expressed through the standardized precipitation and evaporation index (SPEI) quantified by aggregating the climate water balance and fitting monthly series to a generalized logistic distribution using L-Moments. The SPEI, determined at windows of different time scales of one, three and twelve months, provided an extensive evaluation of dryness severity and its impact on this sensitive ecosystem. Rain onset and cessation dates were generated from cumulative pentad rainfall&ndash;evapotranspiration relationships. Analysis of climatic data showed mean rain onset occurring in November and ceding in March with average of 44 rainy days between 1970/71 and 2013/14. The results revealed a decrease in the number of rainy days at a rate of 0.16 days/yr and of the duration of the rainy season at 0.25 days/yr with high variability. Annual rainfall was found to decrease at the rate of 1.60 mm/yr with 6.8% probability of failure in rainfall onset. Analysis further revealed that both extreme dryness and wetness are rare phenomena with probabilities of less than 1% and near normal conditions for 67% of the time for all SPEI time scales. Although gradual increase in dryness in the Delta is attributed to high climatic variability, simulations undertaken using Artificial Neural Networks did not predict any major changes in the next five years. However, vulnerability to severe droughts is not completely ruled out because of the high variability in rainfall and of the location of the Delta in a semi-arid zone.&nbsp;</p> </div> <p>&nbsp;</p>