On the relationship between the 500 hPa height fluctuations and the atmosphere thickness over Iran and the Middle East

Abstract

This paper focuses on the relationship between the 500 hPa height fluctuations and the associative atmosphere thickness (AT) over Iran and the Middle East between 1961 and 2013. For this purpose, atmospheric Geopotential Height (HGT) data of the 1000 and the 500 hPa levels were obtained from the NCEP/NCAR database covering the domain of longitudes 25°E to 75°E and latitudes 15°N to 45°N. The correlation coefficient was used to investigate the relationship. The results showed that the daily fluctuations at the 500 hPa height and the AT over the Middle East were low. However, the degree of instability of the AT and the 500 hPa height was higher in the fall season, due to the study region being located in the transition region of different air masses. The lowest instability of the 500 hPa height and the AT was observed in summer due to the dominance of the subtropical dynamical high pressure which was observed in the summer season and in low latitudes of the Middle East. Nevertheless, the greatest effects of HGT on the AT were observed in the middle latitudes. This situation was due to the cold weather which attacked from the high latitudes toward the mid-latitudes, as well as the convection of hot air from the equator to the high latitudes, causing a sharp temperature difference in the middle latitudes and strongly affecting the AT. So, the fluctuations of the 500 hPa reached their maximum in the midle latitudes. In general, there was a significant, direct relationship between oscillations of the 500 hPa height and the AT.