Investigating the response of the Botswana High to El Niño Southern Oscillation using a variable resolution global climate model

Abstract

The Botswana High is an important component of the regional atmospheric circulation during austral spring, summer and autumn. While the high tends to be stronger during El Niño and weaker during La Niña, its direct response to El Niño Southern Oscillation (ENSO) remains unknown. To that end, a variable resolution global climate model (Model Prediction Across Scales version 7, hereafter MPAS) is applied with relatively high resolution (48 km grid spacing) over southern Africa and a coarser resolution (240 km grid spacing) over the rest of the globe for the study period 1980-2010. The rst model experiment uses observed SSTs everywhere during the study period, while the second experiment uses observed SSTs everywhere except over the Paci c Ocean, where monthly climatological SSTs are imposed. The model results were validated against satellite data (Global Precipitation Climatology Project, GPCP), reanalysis datasets (Climate Forecast System Reanalysis, CFSR; European Centre for Medium-Range Weather Forecasts version 5, ERA5). The results of the study show that the MPAS model gives a credible simulation of the temporal variability of the Botswana High, the seasonal rainfall and 500 hPa geopotential heights over southern Africa. In the absence of ENSO forcing, the amplitude of the Botswana High variability reduces but the signal of the variability remains. Hence, this study shows that ENSO enhances the strength of the Botswana High but does not aid in the formation of the Botswana High.

The Impact of Drought on HIV Care in Rural South Africa: An Interrupted Time Series Analysis

“…Drought years calculated from the Riverview-SPI, which typically coincide with El Nino events while wet years coincide with La Nina events in the Hlabisa subdistrict, are consistent with previous studies which found similar results over the Southern African region (Gore et al 2020 ; Maoyi and Abiodun 2021 , 2022 ). That is because El Nino years are characterised by anomalous upper tropospheric convergence (at 200 hPa) over the Southern African domain leading to increased subsidence and drought conditions, while La Nina years were characterised by anomalous upper tropospheric divergence (at 200 hPa) which may lead to enhanced convection and increased rainfall over the region (Maoyi and Abiodun 2021 , 2022 ). The years 2014, 2015 and 2016 were particularly dry years in Hlabisa, as demonstrated by the SPI.…”

Mapping Climate Parameters over the Territory of Botswana Using GMT and Gridded Surface Data from TerraClimate

“…Mapping climate parameters using advanced cartographic methods is presently the subject of intense research. Approaches to image processing [1,2], climate data modelling [3] and landscape studies [4] have largely converged on the requirements for the importance of cartographic visualisation for a proper environmental analysis for feature extraction and evaluation. While standard methods of handling spatial data such as Geographic Information Systems (GIS) are popular for climate and environmental mapping [5][6][7], superior performance has been demonstrated by incorporating advanced scripting solutions for complex cartographic tasks.…”