Monthly Means Of Daily Average Temperature (C) December

Under conditions of natural vegetation, mean temperatures are used to distinguish between three broad thermal divisions of plants, viz. mega-thermal plants, which require mean monthly temperatures above 20 degree Celsius for at least 4 months of the year; micro-thermal plants, which grow where 8 months or longer have means below 10 degree Celsius; and the meso-thermal plants of the mid-latitudes, which cover most of South Africa, and whose physiology is adapted to the strong seasonal rhythms which are experienced over most of the southern African subcontinent. Month-by-month variations of mean temperature influence the geographic range and the optimum growth areas of certain vegetation and crop species, especially those with life-cycles extending one year or less.

Assuming a daily average temperature to be represented by the mean of that days minimum and maximum temperatures, these averages were derived from the 50 year (1950 – 1999) time series of quality controlled daily minimum and maximum temperatures which were generated from over 970 qualifying temperature stations using infilling and record extension techniques developed by Schulze and Maharaj (2004). From these point location time series, 50 years of daily mean temperature values were derived at each of 429 700 one arc minute (1.7 km x 1.7 km) grid points covering South Africa, using regionally and seasonally determined lapse rates and other physically appropriate spatial interpolation approaches (Schulze and Maharaj, 2004). From the daily values, monthly means and standard deviations of daily values for each month of the year could be computed for purposes of mapping and production of tables of statistics for each of the nine provinces of the RSA as well as for Swaziland and Lesotho.

在自然植被条件下，可借助月均气温划分三大植物温度大类：即高温植物（mega-thermal plants），这类植物需一年中至少4个月的月均气温高于20℃；低温植物（micro-thermal plants），其生长区域内8个月及以上的月均气温低于10℃；以及中纬度地区的中温植物（meso-thermal plants），该类植物覆盖南非大部分区域，其生理机能适配南部非洲次大陆多数区域存在的强烈季节节律。月均气温的逐月变化会影响特定植被与作物物种的地理分布范围与最优生长区域，尤其是那些生命周期为一年及以内的物种。
假设日均气温以当日最高、最低气温的平均值表征，上述气温数据源自1950–1999年共50年的经过质量控制的逐日最高、最低气温时间序列。该数据集由超过970个合格气象站点生成，采用Schulze与Maharaj（2004）提出的插补与记录延伸技术完成数据补全与延伸。基于这些站点尺度的气温时间序列，结合区域与季节确定的气温直减率及其他物理意义合理的空间插值方法（Schulze和Maharaj，2004），在覆盖南非的429700个1弧分（1.7 km ×1.7 km）网格点上分别计算得到了50年的日均气温序列。通过这些日均气温数据，可进一步计算得到各月的月均气温与日均气温标准差，用于绘制南非共和国（RSA）下辖9个省份以及斯威士兰、莱索托的气温分布图与统计表格。