Synoptic analysis of trough depressions and their impact on rainfall in central and southern Iraq during winter and spring

Abstract

      The study of upper-level pressure patterns is vital in applied climatology because they directly influence surface weather. The 500 mb pressure level is particularly important, as it reflects atmospheric dynamics and circulation systems. Among these, the cut-off low is a key phenomenon associated with instability and plays a major role in rainfall variability. This study analyzes the synoptic impact of cut-off lows on rainfall in Iraq during winter and spring from 2013 to 2023. Results indicate that cut-off lows caused 2,171 rainfall events: 1,140 during the 00 UTC observation and 1,031 during the 12 UTC observation. Seasonally, 1,119 events occurred in winter and 1,052 in spring. The higher winter frequency is linked to active deep low-pressure systems and strong westerly currents, which enhance cut-off low formation. In contrast, spring events are less effective due to weaker cold air masses and stronger temperature gradients.