Cases of juxtaposition of pressure systems in Iraq

Abstract

The phenomenon of adjacency represents one of the forms that pressure systems take when occupying a specific geographical area. The geographical area they cover varies and appears on surface and upper-level observation maps as a juxtaposition between different pressure systems in terms of climatic characteristics. When analyzing surface observation maps (1000 hPa) and upper-level maps at the pressure level (500 hPa) over a period of 11 years (2010-2020) during the transitional seasons (spring and autumn), five cases and patterns of adjacency were observed at the surface level. The most frequent cases of adjacency were the singular extensions of high-pressure systems with isolated low-pressure systems, with (37, 59) days recorded for the first and second observations during spring, and (24, 11) days for the observations during autumn. However, the adjacency of pressure centers for high-pressure systems with low-pressure systems was the least frequent surface adjacency, with (1-5) days recorded for the two observations during spring only, and autumn showed no occurrence of this adjacency. As for the upper-level air waves, troughs were more present with adjacency cases, reaching (19, 30) days for the two observations during spring and (11, 18) days during autumn, while they were associated with only one day in the case of pressure centers’ adjacency in the first observation.