Seasonal total rainfall (mm per 3-month season) change from the median projected for 2036-2065, relative to present (1976 - 2005), for MAM season under the RCP 4.5 pathway

Seasonal (MAM) rainfall (mm per month) change from the median projected for 2036-2065, relative to present (1976 - 2005), under the RCP 4.5 pathway for the southern African region. To generate the image, nine coarse General Circulation Models (GCM) are downscaled to a finer spatial resolution (0.44°x 0.44°) using the Rossby Centre regional model (RCA4) forcing its lateral boundaries. The model simulated daily rainfall averages, which are used to generate projections of seasonal change. The projections are generated using the medium to low (RCP4.5) pathway which associates CO2 concentrations of approximately 560ppm by the year 2100. The associated RMSD it calculated and shows the uncertainty range of the projected model simulated residual values, and gives a relative perspective of spatial areas associated with higher and lower projection uncertainties.

相较于当前基准期（1976-2005年），典型浓度路径4.5（Representative Concentration Pathway 4.5, RCP4.5）情景下南非地区2036-2065年的季节（MAM，即三月、四月、五月）降雨量（单位：毫米/月）的变化量，该变化以2036-2065年的中位数预测值为参照。为生成该图像，研究采用罗斯比中心区域模式（Rossby Centre regional model, RCA4），通过强迫其侧边界条件，将9个粗分辨率全球环流模式（General Circulation Models, GCM）的结果降尺度至0.44°×0.44°的更高空间分辨率。该模式模拟的日降雨量平均值被用于生成季节尺度的降雨量变化预测结果。本次预测基于中低排放情景（RCP4.5）生成，该情景预计到2100年时大气二氧化碳浓度将达到约560ppm。研究计算了相关的均方根偏差（Root Mean Square Deviation, RMSD），该指标可展示模式模拟残差预测值的不确定性范围，并能相对呈现出预测不确定性高低各异的空间区域。