On the Summertime Planetary Boundary Layer with Different Thermodynamic Stability in China: A Radiosonde Perspective

Abstract

Strongly influenced by thermodynamic stability, the planetary boundary layer (PBL) is key to the exchange of heat, momentum, and moisture between the ground surface and free troposphere. The PBL with different thermodynamic stability across the whole of China, however, is not yet well understood. In this study, the occurrence frequency and spatial distribution of the convective boundary layer (CBL), neutral boundary layer (NBL), and stable boundary layer (SBL) were systematically investigated, based on intensive summertime soundings launched at 1400 Beijing time (BJT) throughout China’s radiosonde network (CRN) for the period 2012 to 2016. Overall, the occurrences of CBL, NBL, and SBL account for 70%, 26%, and 4%, respectively, suggesting that CBL dominates in summer throughout China. In terms of the spatial pattern of PBL height, a prominent north–south gradient can be found with higher PBL height in northwest China. In addition, the PBL heights of CBL and NBL were found to be positively (negatively) associated with near-surface air temperature (humidity), whereas no apparent relationship was found for SBL. Furthermore, clouds tend to reduce the occurrence frequency, irrespective of PBL type. Roughly 70% of SBL cases occur under overcast conditions, much higher than those for NBL and CBL, indicating that clouds govern to some extent the occurrence of SBL. In contrast, except for the discernible changes in PBL height under overcast conditions relative to those under clear-sky conditions, the changes in PBL height under partly cloudy conditions are no more than 170 m for both NBL and CBL types.

Shift in the Temporal Trend of Boundary Layer Height in China Using Long‐Term (1979–2016) Radiosonde Data

“…The spatial pattern of BLH exhibits a west‐to‐east gradient, decreasing from Western China to Eastern China. We find that this is in good agreement with the spatial pattern as measured at 1400 BJT (Zhang et al, ). On average, the BLHs at 2000 BJT show a high degree of variance throughout the whole mainland China, ranging from 100 to 2,000 m with most BLHs measured in the range from 100 to 600 m (Figure S2).…”

On the Relationship Between Aerosol and Boundary Layer Height in Summer in China Under Different Thermodynamic Conditions

“…The NBL generally refers to the neutrally stratified residual layer that starts from the ground surface (Liu & Liang, ). The spatial and temporal variability of these three PBL regimes over China were revealed by Zhang et al (). Nevertheless, the knowledge regarding how these three dominant PBL types interact with aerosol pollution remains poorly understood.…”

“…Besides, the enhancement of aerosol concentrations were tightly associated with increases in cloud cover (CLD; Miao, Guo, Liu, Liu, Li, et al, ). This is likely due to the fact that clouds tended to reduce the solar radiation reaching ground surface and thus suppress vertical turbulence and mixing (Guo, Miao, et al, ; Zhang et al, ). Among others, the increases in aerosol concentrations were accompanied by high relative humidity (RH) conditions, where enhanced hygroscopic growth and multiphase reactions facilitated the increases in particle size and mass (Miao, Guo, Liu, Liu, Zhang, et al, ; Tie et al, ; Zhong et al, ).…”

“…The China radiosonde network operated by the China Meteorological Administration (CMA) provides us a unique opportunity to study the features of PBL across China (Guo, Miao, et al, ; Zhang et al, ). Given the ignorance of PBL regimes in previous studies, one of the principle goals is to examine the interaction between aerosol and BLH under CBL, NBL, and SBL conditions.…”

Synoptic patterns and sounding‐derived parameters associated with summertime heavy rainfall in Beijing

“…In addition to the large-scale synoptic forcings, the local thermodynamic characteristics of the atmosphere are also found to be closely associated with the occurrence of heavy precipitation (Dyson et al, 2015). Among others, the soundings from radiosonde are the key measurements for characterizing the thermodynamic conditions of the atmosphere (Seidel et al, 2010;Dyson et al, 2015;Guo et al, 2016;Li et al, 2017;Zhang et al, 2018;Miao et al, 2018;Miao and Liu, 2019). The pioneering work by Fawbush and Miller (1954) has indicated the role of sounding patterns in predicting high-impact severe weather, followed by Beebe (1955) and Miller (1972) who used a wide range of soundings to analyse the atmospheric environment for tornados.…”