The climatology of planetary boundary layer height in China derived from radiosonde and reanalysis data

The important roles of planetary boundary layer (PBL) in climate, weather and air quality 15 have long been recognized, but little is known about the PBL climatology in China. Using the fineresolution sounding observations made across China and reanalysis data, we conducted a comprehensive investigation of the PBL in China from January 2011 to July 2015. The boundary layer height (BLH) is found to be generally higher in spring and summer than that in fall and winter. The comparison of seasonally averaged BLH derived from observations and reanalysis shows good 20 agreement. The BLH derived from threeor four-times-daily soundings in summer tends to peak in the early afternoon, and the diurnal amplitude of BLH is higher in the northern and western sub-regions of China than other sub-regions. The meteorological influence on the annual cycle of BLH is investigated 4 as well, showing that BLH at most sounding sites is negatively associated with the surface pressure and lower tropospheric stability, but positively associated with the near-surface wind speed and temperature. This indicates that meteorology plays a significant role in the PBL processes. Overall, the key findings obtained from this study lay a solid foundation for us to gain a deep insight into the fundamentals of PBL in China, which helps to understand the roles of PBL playing in the air pollution, weather and 5 climate of China.