Characteristics of vertical atmosphere based on five-year microwave remote sensing data over Wuhan region

摘要

To enhance the understandings of the regional climatic characteristics, vertical distributions of temperature and relative humidity (RH), height of atmospheric boundary layer (ABLH), integrated water vapor (IWV), and liquid water path (LWP) were analyzed based on five-year observations from a ground-based microwave radiometer over Wuhan. Performance of ground-based microwave radiometer (MWR) was also estimated by comparing with the radiosonde (RS) data. The temperature profile measured by the microwave radiometer was better under cloudy conditions, while the RH profile had higher accuracy under cloud-free conditions. The IWV from MWR generally showed a good consistency with RS data (R2 0.95), whereas a slight underestimation was found under cloud-free conditions as the slope of linear regression was 0.898. Variations of temperature and humidity profiles showed a distinct seasonal cycle in this region. Two abrupt turning points happened around April and October respectively, resulting in cold winters and hot and wet summers. The highest and lowest values of temperature appeared at -15 and - 6 local time respectively and the vertical extension of temperature fluctuated between 5 and 7 km depending on the season, mainly related to incoming solar irradiation intensity. Due to the inhomogeneity of temperature changes in vertical direction, the ABLH also showed distinct diurnal (0.79-1.98 km) and seasonal (1.12-2.01 km) variations. The IWV was a unimodal distribution in a year. The minimum and maximum were found in December (-10.3 kg/m2) and July (-54.7 kg/m2). An abnormal high RH (a positive anomaly of -5.7% below 2 km) was observed in February, higher than January and March. Meanwhile, the highest average LWP (114.4 g/m2) was also observed in February. Low temperature and increasing IWV caused more water vapor to condense into water droplets and form clouds in the atmosphere, and thus the RH and LWP increased. The above findings provided estimations of microwave radiometer performance and enhanced our understandings of the regional climatic characteristics.