Elucidating the impact of high- and low-pressure systems on temperature inversion from nine years of radiosonde observations in Beijing

Abstract

Temperature inversion (TI) has long been recognized to play an important role in air quality and convection initiation, mainly through modulating the dynamic and thermodynamic processes of planetary boundary layer (PBL). Yet, our knowledge remains poor regarding the relationship between TI and the synoptic systems. Here we use nine years (2011–2019) of high-resolution radiosonde data from the Beijing site to quantify the impact of TI on the dynamic and thermodynamic conditions associated with the activities of synoptic systems. The monthly, seasonal and diurnal changes of the TI occurrence frequencies are first analyzed, and the surface-based inversions (SBIs) are found more related to the surface properties, whereas elevated inversions (EIs) are potentially more influenced by thermodynamic and dynamic characteristics of the atmosphere. A novel method based on the threshold of seasonal averaged sea level pressure for identifying the centers of high-pressure system (HPS) and low-pressure system (LPS) is developed. Statistical analyses show that the pressure gradients are stronger in the presence of TI, when HPS or LPS centers approach the observational site of interest from the northwest. The pressure difference becomes larger between the center and the site when the HPS or LPS center locates farther. Height-resolved zonal and meridional temperature advection and wind anomalies are further investigated, showing that the EIs are possibly related to the downslope intrusion of cold air under the control of HPS and to the heat transportation under the control of LPS over the mountain slopes. The TI-favored temperature advection brought by the prevailing wind of the synoptic systems, aided by topographic uplifting, may also reinforce the occurrence of EI.