Climatic variations in the boundary layer height of arid and semiarid areas in East Asia and North Africa

Based on the era-20c,climatic variations of the boundary layer height (blh) over arid and semiarid areas in east asia and north africa that span 1900–2010 were analyzed. in east asia,the blh exhibited a descending trend from arid region centers to the periphery. over the past 111 years,the blh has had a rising trend of 14.0 m decade−1. in the representative region (ea1) of the eastern areas with the 111-year average of 725 m and a decreasing trend of −1.6 m decade−1. in the representative region (ea2) of the western areas with the 111-year average of 792 m. from the mid-1960s to 1970s,ea1’s blh had a sharp rise that caused the average to increase by 93 m after the 1980s. in north africa,the blh exhibited a high spatial distribution in the western and southern areas and a relatively low spatial distribution in the eastern and northern areas. over the past 111 years,the blh has had a rising trend of 9.7 m decade−1. in the representative region (na1) of the southwestern region with the 111-year average of 915 m and a decreasing trend of −6.3 m decade−1. in the representative region (na2) of other regions with the 111-year average of 882 m. in the 1940s and the 1970s,na1’s blh had two obvious increases that caused the average to increase by 51 m and 22 m,respectively,while na2’s blh had two obvious declines that caused the average to decrease by 48 m and 7 m,respectively. on the spatial distribution,the blh,sensible heat flux,latent heat flux,and volumetric soil water had a good corresponding relationship. on the temporal change,the blh in east asia had a stronger correlation with thermodynamic factors,whereas the blh in north africa had a stronger correlation with dynamic factors. besides,the upper-level stratification also has some influence on the blh’s change. © 2017,meteorological society of japan.