أثر تغير المناخ في تغير مدة بقاء خط سمك 5400 متر و علاقته بتغير مدد بقاء المنظومات الضغطية السطحية فوق العراق للمدة 1948-2014

Abstract EN

This research aims at studying and analyzing the impact of climate change on one of the most important thickness lines of the atmosphere, thickness line 5400m.

This line separates air masses, which has different properties, within the middle latitudes.

The changes to its recurrence and the days of its existence over Iraq region for the 66-day rainy seasons and six minor climate cycles lasting for (11) years, have been identified in the period 1984-2014.

Thickness line is shown on the thickness maps (1000-500 hpa) from the end of October up to early April only.

By pinpointing the change direction, it was noticed that there was a decrease in recurrence and the days the 5400m thickness line lasts over Iraq due to climate change and the rise in the temperatures of the bottom section of the Troposphere, a matter that gives a clear indication of the increasing thickness of the atmosphere over Iraq region during rainy seasons, weak exchange of air masses, and the formation of atmospheric depressions.

Furthermore, the study shows a change in the days of surface pressure systems accompanying the recurrence of the studied thickness line; there has been a reduction in the days of the Mediterranean depression and integrated depression.

These depressions pull the rear part of the trends of polar cold air masses, a matter which contributes in the development of the front activity, reduction of the atmospheric thickness and increase of the days of Sudan depression due to the low recurrence of both aforesaid depressions.

On the other hand, Siberian and Subtropical high-pressure days, associated with the studied thickness line, have increased; this increases atmospheric stability and acts as pressure barriers preventing progress of atmospheric depressions towards Iraq.

Moreover, the days of the European depressions, associated with the studied thickness line 5400 m, have reduced due to the weak recurrence of the Mediterranean depression and integrated depression, especially the deep ones that pull its trends behind the cold air front.