Paz, S. (Department of Geography, University of Haifa, Israel)
Kutiel, H. (same affiliation)
Several studies have been published during the last few years dealing with the relationship between rainfall totals and pressure field. However, most of them dealt with analysis of case studies. The purposes of the present study are to find which of the anomalies in sea level pressure (SLP) may result in corresponding changes in the rainfall regime in Israel, to define the kind of relationship between SLP and rainfall in Israel and to group stations into regions, in which similar pressure fields may result in alike rainfall conditions.
Data and Methodology:
Twelve rainfall stations, sampling all climatic regions of Israel, were selected. Monthly totals for the period 1961-1990 were analyzed. SLP data at 72 grid points in the region delimited by latitudes 20░N and 60░N and longitudes 20░W and 50░W for the same period, were also analized.
Monthly rainfall totals for each month and each station, were normalized and classified according to the criteria as follows:
2.5
Average pressure maps of dry or wet conditions for each month were prepared and the regional flows associated with these conditions were derived from the maps.
Correlations between rainfall totals in each of the twelve stations in Israel and pressure in grid points were calculated amd mapped. Rainfall stations were grouped into regions, according to their correlation coefficients with the different grid points.
The mean location and magnitude of the main pressure systems during the period 1961-1990 were definde and mapped, and mean anomalies in SLP characteristic of wet and dry months were identified.
Conclusions:
The main results are as follows:
1. The highest standard deviations were observed in the vicinity of the Icelandic low and the Siberian anticyclone. 2. Analysis of the average monthly pressure maps (1961-1990) show that in the majority of winter months in Israel, there is a tendency to eastern or south-eastern winds, which means that the Israeli region has a higher tendency to dry conditions than to wet conditions. 3. ZI and MI indices values may adequately predict, the directions of the main flow during a certain month. 4. The spatial correlation between SLP and rainfall increased from October to April, meaning that rainfall is more uniform toward the end of the rainy season.