Seasonal total rainfall (mm per 3-month season) change from the 10% percentile projected for 2036-2065, relative to present (1976 - 2005), for DJF season under the RCP 4.5 pathway

Seasonal (DJF) rainfall (mm per month) change from the 10% percentile 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.

本数据集为南部非洲地区在典型浓度路径4.5（Representative Concentration Pathway 4.5, RCP 4.5）情景下，以1976-2005年为基准期，2036-2065年预测降雨量序列10%分位值对应的季节性（DJF，即12月、1月、2月）月降雨量（单位：毫米/月）变化量。本数据集配套可视化图像的生成流程如下：选取9套粗分辨率全球环流模式（General Circulation Models, GCM）的输出结果，通过罗斯比中心区域模式（Rossby Centre regional model, RCA4）进行空间降尺度处理，将空间分辨率提升至0.44°×0.44°，并以该区域模式作为侧边界强迫场。该区域模式模拟的日降雨量平均值被用于计算季节性降雨量变化的预测结果。本次预测基于中低排放情景RCP 4.5开展，该情景预计到2100年大气二氧化碳浓度将达到约560ppm。研究同时计算了对应的均方根偏差（Root Mean Square Deviation, RMSD），该指标可表征模式模拟残差预测值的不确定性范围，并可直观反映不同空间区域的预测不确定性高低分布情况。