Biot-Savart law and the formation mechanism of Somali low-level jet

Abstract

Firstly, we investigate the impact of cross-equatorial Somali low-level jet on the atmospheric circulation in the east of Tibet Plateau using lattice Boltzmann model simulation. Secondly, we study the relationship between thermal conditions on the bottom boundary and the formation of Somali jet based on Biot-Savart law using the data from National Centres for Environmental Prediction (NCEP). As the radiation from the Sun gradually moves from the southern meridian, the temperature on the ground surface of Somali Peninsular and Arabic Peninsular gradually increases. During the same period the surface temperature of the Northern Indian Ocean increases much slower. It is shown that this increase in the temperature difference between the land and sea is inductive to the formation and development of Rayleigh-Benard convection and leads to the increasing relative vorticity strength between positive and negative vertical vortices over the land and sea. According to Biot-Savart law, the increase in vorticity strength will induce correspondingly a large horizontal velocity. The pair of positive and negative vorticity fields over the two Peninsulars and the sea surface is effective in forming and maintaining this current. This mechanism is referred to as "Somali suction pump". It draws air continually from the Southern hemisphere and releases it at the coastal area of Somali.