| description abstract | his study examines the atmospheric circulation characteristics of dust outbreaks (DOs) over the central Arabian Peninsula. Based on a 12-yr (1999?2011) Aerosol Robotic Network (AERONET) database over the Solar Village in Saudi Arabia and criteria pertinent to the aerosol optical depth at 500 nm and the Ångström exponent, 177 DOs have been identified. Factor and cluster analysis are further applied on the 1000- and 700-hPa geopotential height daily patterns of the days preceding the onset of the DOs and the days of the DOs? initiation, revealing four main types (clusters) of the atmospheric circulation evolution leading to DOs. During the winter season, the anticyclonic circulation intensifies over the Middle East causing the strengthening of the pressure gradient over the Arabian Peninsula, inducing northerly winds over the study region, thereby favoring dust entrainment in the atmosphere (cluster 1, 16 DOs, 9%). The passage of midlatitude cyclones over the northern or central Arabian Peninsula is frequently accompanied by postfrontal northerly winds also promoting the presence of DOs in the region (cluster 2, 41 DOs, 23%). The DOs during spring are likely favored by the enhancement of convective activity, as the thermal low over the Arabian Peninsula further influences the dynamics of the upper troposphere (cluster 3, 73 DOs, 41%). During summer the pressure gradient over the study region is greatly enhanced due to the extension of the subtropical Azores anticyclone over the Mediterranean. The latter is the main driver triggering the DOs in this cluster category (cluster 4, 46 DOs, 27%). | |
