Annual mean near-surface (2m) temperature (°C) change from the 90% percentile projected for 2066-2095, relative to present (1976 - 2005), under the RCP 4.5 pathway

Annual mean near-surface (2m) temperature (°C) change from the 90% percentile projected for 2066-2095, 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 temperature averages, which are used to generate projections of annual 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.

本数据集表征南非地区在典型浓度路径4.5（RCP 4.5）情景下，针对2066-2095年的90%分位数投影结果，相较于当前基准时段（1976-2005年）的近地表（2米）年平均气温变化（单位：摄氏度）。为生成该数据集对应的可视化图像，研究采用罗斯比中心区域模式（Rossby Centre regional model, RCA4）作为侧边界强迫场，对9套粗分辨率全球环流模式（General Circulation Models, GCM）进行降尺度处理，将其空间分辨率提升至0.44°×0.44°。该模式模拟的日平均气温数据被用于计算年平均气温变化的投影结果。本次投影采用中低排放情景下的典型浓度路径4.5（RCP 4.5），该情景预计到2100年大气二氧化碳浓度约为560ppm。研究中计算了对应的均方根偏差（Root Mean Square Deviation, RMSD），其用于表征模式模拟残差的投影结果的不确定性范围，并可直观反映空间上不同区域的投影不确定性高低差异。