Actual Vapour Pressure (May)

Actual vapour pressure is the variable expressing atmospheric moisture content through the partial pressure exerted by the water vapour present in the atmosphere. The monthly uncorrected vapour pressure, ed, at any given location in South Africa was subsequently held constant for that entire month and derivatives of ed, such as daily maximum and minimum relative humidity or daily vapour pressure deficit which depend on ratios of uncorrected actual to saturated vapour pressure, were then computed using daily maximum/minimum temperatures as inputs to daily saturated vapour pressure calculations, which were in turn used with that location's monthly uncorrected actual vapour pressure.

实际水汽压（actual vapour pressure）是通过大气中所含水汽的分压来表征大气水汽含量的变量。针对南非任意指定地点，其未校正月度水汽压（ed）在整月内保持恒定；依赖未校正实际水汽压与饱和水汽压（saturated vapour pressure）比值的ed衍生变量，例如日最高相对湿度、日最低相对湿度或日水汽压差（vapour pressure deficit），则以每日最高、最低气温作为输入计算每日饱和水汽压，再结合该地点的未校正月度实际水汽压完成计算。