Evaluation of Atmospheric Blocking Effects on Weather Events in Iraq

Abstract

Atmospheric blocking has received a lot of attention in recent years due to its impacts on mid-latitude circulation and then on weather extremes such as cold spells, heat waves, drought, and heavy rain. In this paper, the effects of atmospheric blocking on weather events ''rainfall in particular'' over Iraq are evaluated. Daily meteorological data from the National Centers for Environmental Prediction (NCEP) for the period 2002-2018 were analyzed to identify different atmospheric blocking systems over Iraq and surrounded regions. In order to locate the blocks on maps, the study domain is extended from 10-70o N and 10-70o E for mean sea level pressure. This study state two cases of Omega blocking system occurred on 25 Jan 2006 and 01-03 Feb 2006. Rainfall observed by the Tropical Rainfall Measurements Mission (TRMM) along with true color cloud images detected by the Moderate Resolution Imaging Spectrora-diometer (MODIS) were employed for determining the severity and trajectory of rainstorms associated with atmospheric blocking systems. NCEP provides data with a spatial resolution of 2.5o × 2.5o while TRMM is 0.25o × 0.25o. Analysis of one typical year (2016) showed that among 24 blocking systems detected during the period of this work, 37.5% were Omega blocks, 20.8% were Cut-off low blocks, 16.7% were Rex blocks, and the percentage of the Cut-off high and Split flow blocks were 12.5% each. The results also indicated that the strongest blocking was the Omega blocking that occurred on 01-03 Feb 2006 and resulted in 120 mm rainfall.