Areal distribution of the discomfort index in Israel

Abstract

The areal distribution of monthly mean values of the Discomfort Index (DI) in Israel is presented for key hours of the day for the summer half of the year. The DI as used in this study, is defined as the arithmetic average of the dry-bulb and wet-bulb temperature (°C), a value of 24 representing conditions at which half the people would feel uncomfortable. Data were collected from 95 meteorological stations situated in different parts of Israel. The raw data consisted of daily values of dry and wet-bulb temperatures for the hours 08:00, 14:00, and 20:00h for the years 1963–1972. Maximum values of the monthly mean DI in Israel generally occur in August. Geographically, the number of days of the year with DI greater than 24 ranges from 30 in the mountain regions, to 120 in the coastal plain, to 180 in the Jordan Valley, Dead Sea, and Arava regions. The dominant control of the observed distribution of DI in Israel appears to be topography. The DI is not a good measure of human discomfort for particularly hot and dry conditions, typical of those occurring during Sharav weather conditions. For such conditions, a new index was developed based on the difference between the dry-bulb and wet-bulb temperatures. The mean areal distributions of this difference index as well as that of the DI are presented for typical intense Sharav conditions. The new difference index appears to better represent discomfort during such conditions.