The symmetry and structural characteristics of the core of the Arabian Subtropical Anticyclone and associated surface climatology over Arabia: A spatial perspective

Abstract

The Arabian High/subtropical Anticyclone (ASA) plays an essential role in regulating weather and climate in the Arabian Peninsula (Arabia) and adjacent countries. However, knowledge of the ASA and related surface conditions in Arabia is limited. Most of our knowledge comes from short-term case studies of weather events. The main goals of this climatic research are to (1) address the spatial structural and symmetry characteristics (shape, direction, intensity, and size) of the ASA core centers for Sep to Mar; and (2) examine related seven month summaries of surface weather characteristics for precipitation, temperature, wind, and particulates with diameters <2.5 μm (PM2.5) over Arabia.Based on a K-means clustering analysis, the monthly core centers of the ASAs at 850 hPa were identified and shape and direction parameters were quantified using the standard deviational ellipse technique. ASAs migrate southeastward across Arabia from Sep to Feb with increases in the average size and decreases in mean heights. Shapes of core centers of the ASAs tended to be elliptical with three dominant orientations. Using a novel spatial–synoptic framework based on a longitudinal-latitudinal positional climatology of the ASA, the ASA has five spatial composites which correspond with different surface climatic conditions. When the ASA is positioned north or northwest of the mean (North and Northwest composites), much of Arabia experiences warm surface air temperature anomalies and negative precipitation anomalies. Both composites showed an increased sensible heat flux into the air over Arabia with the process forming a warmer environment that dries the lower troposphere. The South, East, and Southeast spatial composites were linked with notable negative temperature anomalies and are associated with smaller energy fluxes. These cooler conditions were more pronounced during the South and Southeast composites and were accompanied by positive precipitation anomalies. Dust events, defined by higher PM2.5 amounts, corresponded well with higher surface wind speeds, when the ASA migrates south or southeast from its climatological mean composite.