Monthly Means Of Daily Average Temperature (C) July

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，人们通过平均气温划分出三大植物温度类群，即高温型植物（mega-thermal plants）：需全年至少4个月的月平均气温高于20℃；低温型植物（micro-thermal plants）：生长在8个月及以上月平均气温低于10℃的区域；以及中纬度的中温型植物（meso-thermal plants），这类植物覆盖南非大部分区域，其生理机能适配南非次大陆多数区域的强烈季节节律。月均气温的逐月变化会影响部分植被与作物物种的地理分布范围与最优生长区，尤其是生命周期为一年及以内的物种。本研究假设某日平均气温由当日最高、最低气温的均值表征，所用气温平均值源自1950–1999年共50年的经过质量控制的日最高、最低气温时序序列，该序列由超过970个合格气象站通过Schulze与Maharaj（2004）开发的插补与记录延伸技术生成。基于这些点位时序序列，研究人员利用区域与季节订正的气温直减率及其他物理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，生成了50年的日平均气温序列。基于上述日平均气温数据，可计算得到全年各月的月平均气温与对应月份的日气温标准差，用于绘制南非共和国（RSA）9个省份、斯威士兰及莱索托的气温地图与统计表格。