The Different Influence of the Residual Layer on the Development of the Summer Convective Boundary Layer in two Deserts in Northwest China

The development of the atmospheric boundary layer is closely connected with the exchange of momentum, heat and mass near the earth surface, especially for a convective boundary layer (CBL). Besides being modulated by the buoyancy flux near the earth surface, some studies point out that a neutrally stratified residual layer is also crucial for the appearance of a deep CBL. To verify the importance of the residual layer, the CBLs over two deserts in northwest China, the Badan Jaran and Taklimakan deserts are investigated. The summer mean CBL depth over the Taklimakan desert was shallower than that over the Badan Jaran desert, with even the sensible heat flux of the former being stronger. Meanwhile, the climatological mean residual layer in the Badan Jaran desert was much deeper and neutrally stratified in summer. Moreover, a significant and negative correlation between the lapse rate of the residual layer and the CBL depth was found over the Badan Jaran desert. The different lapse rates of the residual layer in the two regions are partly connected with the advection heating from large-scale atmospheric circulation. The advection heating tends to reduce the temperature difference in the 700 to 500 hPa layer over the Badan Jaran desert, and increase the stability in the same atmospheric layer over the Taklimakan desert. The advection due to climatological mean atmospheric circulation is more effective at modulating the lapse rate of the residual layer than that from varied circulation.