1 1 Trajectory Analysis of Saudi Arabian Dust Storms 2 3 Michael Notaro 4 Nelson Center for Climatic Research, University of Wisconsin-Madison 5 1225 West Dayton Street, Madison, Wisconsin 53706 6 *
[email protected], 608-261-1503 7 8 Fahad Alkolibi, Eyad Fadda, Fawzieh Bakhrjy 9 King Saud University 10 11 Revised Research Article to the Journal of Geophysical Research-Atmospheres 12 13 Abstract 14 15 Temporal and spatial characteristics of Saudi Arabian dust storms, with focus on 16 associated air parcel trajectories, are investigated using station and gridded weather 17 observations and remotely-sensed aerosol optical depth (AOD). For 13 focal stations, an 18 extensive pool of 84-hour backward trajectories is developed for dust storm days, and the 19 trajectories are grouped into 3-5 representative clusters based on the K-means technique 20 and Silhouette Coefficients. 21 Saudi Arabian dust storms are most prominent during February-June, with a mid- 22 winter peak along the southern coast of the Red Sea, spring peak across northern Saudi 23 Arabia around the An Nafud Desert, and early summer peak in eastern Saudi Arabia around 24 the Ad Dahna Desert. Based on backward trajectories, the primary local dust source is the 25 Rub Al Khali Desert and the primary remote sources are the Saharan Desert, for western 26 Saudi Arabia, and Iraqi Deserts, for northern and eastern Saudi Arabia. During February- 27 April, the Mediterranean storm track is active, with passing cyclones and associated cold 28 fronts carrying Saharan dust to Saudi Arabian stations along the northern coast of the Red 29 Sea.