Decadal variation and trend of boundary layer height and possible contributing factors in China

Observational evidence has indicated a significant decline in the planetary boundary layer height (BLH) in China since the 2000s. However, the specific factors contributing to this decline have remained unclear. This study uses an approach based on partial derivative equation to investigate the individual and combined impacts of six potential land surface factors (sensible heat flux, latent heat flux, air temperature, specific humidity, wind speed, and vertical velocity) on the variation and trend of BLH in China from 2000 to 2016. The results reveal that wind speed predominantly influences BLH variation in most months, except for the period from June to August, where air temperature becomes the primary driver. Regarding the BLH trend, sensible heat flux plays a dominant role in most months and across various regions of China. However, during the June to August timeframe, the change in latent heat flux, driven by vegetation greening in northern China, becomes the primary factor influencing the BLH trend. These findings provide important insights for regional sustainable management and environmental protection, supporting policymakers and local administrations in China.