NUMERICAL STUDY OF THE EFFECT OF SEA SURFACE TEMPERATURE PERTURBATIONS ON A DESERT DEPRESSION

This work aimed to investigate the effect of the perturbations in Mediterranean Sea surface temperature (SST) on the development and track of a desert depression which occurred on 22 to 25 March 2003. The desert depression formed over Algeria in the lee of the Atlas Mountains on 22/00 March in response to midlatitude trough intrusion. It migrated eastward with a high speed and reached Egypt 24/12 March before exiting the northeast African continent toward eastern Mediterranean Sea on 25/12 March. The horizontal scale of the cyclone at the surface varied between 800 and 1000 km during its lifetime, while on the vertical the cyclone extended over 8 km. The cyclone was characterized by a surface pressure anomaly of about 9 hPa with respect to the environment, a pronounced rise of temperature (about 8o C above normal), and strong southerly surface wind that cause rising sand and sand storm over North Africa. Ten simulations in this study are conducted using the Weather Research and Forecasting coupled with Chemistry Model (WRFChem) to explain the Sensitivity of our depression to perturbations in Mediterranean SST. The simulations conclude that the model was able to reasonably reproduce the structure, lifetime, and trajectory of the cyclone. Also, it’s found that a warmer sea increases the surface latent heat fluxes and the upward moisture, favoring development of convection in the storm. The dust was transported all around the cyclone leaving a clear eye at its center and was lofted to altitudes as high as 7 km, becoming subject to long-range transport.