Intercomparison of planetary boundary-layer height in Mexico City as retrieved by microwave radiometer, micro-pulse lidar and radiosondes

Abstract

The planetary boundary layer (PBL) height plays a major role in air quality and weather forecast studies. However, it cannot be directly measured as it can only be determined from the measured profiles of atmospheric parameters such as., temperature, moisture, and aerosol backscatter based on different retrieval mechanisms. This paper presents the PBL features such as., stable boundary layer (SBL), convective boundary layer (CBL), and residual layer (RL) detected from the microwave radiometer (MWR), mini Micro Pulse Lidar (MPL), and radiosondes (RS) and an intercomparison was done between the instruments during the period of 16 February – 31 May 2019 in Mexico City. RS were launched thrice a day during this period at 06 LST, 12 LST, and 18 LST respectively. The PBL heights comparison was classified into 3 categories: MWR-RS, mini MPL-RS, and mini MPL-MWR. The daytime CBL heights for the MWR-RS comparison correlate well (r = 0.96 at 12 LST, r = 0.88 at 18 LST) as well as RL height (r = 0.94 at 06 LST). The CBL and RL heights for the mini MPL-RS and mini MPL-MWR comparison also agree very well (0.89 < r < 0.99). Overall, the corresponding SBL height comparisons at 06 LST yielded lower agreements (r < 0.66) with the lowest correlation values for the mini MPL-MWR comparison (r = 0.39), which is likely due to the inability of the mini MPL to detect aerosol backscatter below ~120 m above ground level (agl) as well as the stability of the atmosphere, which prevents uniform mixing of the aerosol particles.