Accuracy Analysis of Atmospheric Temperature and Humidity Profiles Retrieved Using a Ground-Based Microwave Radiometer at the Alpine Skiing Venue

Through the measurement results of the Beijing Nanjiao radiosonde in January–October 2021 and measurement data of the automatic station of the Alpine Skiing Venue in Yanqing during the Winter Olympic Games, the accuracies of temperature and humidity profiles retrieved by a ground-based MicroWave Radiometer (MWR) were assessed. The results revealed that the MWR-retrieved temperature profile exhibited a good correlation with the observations from the radiosonde and the automatic station, with relatively small errors and good reliability. However, the MWR-retrieved humidity profile exhibited poor correlation with the observations from the radiosonde and the automatic station (correlation coefficient=0.81). Comparison of the results from the MWR and those of different automatic stations and the radiosonde revealed that at levels of 0.15–0.6 km, the MWR-retrieved temperature profile exhibited a good correlation with the observations from the radiosonde and the automatic station. Furthermore, the Root-Mean-Square Error (RMSE) and Average Deviation (AD) of the MWR-retrieved temperature profile concerning the observation from the automatic station increased with increasing height and nevertheless those of the MWR-retrieved temperature profile with respect to the observation from the radiosonde decreased with increasing height at levels of 0.15–0.6 km. The correlation, RMSE, and AD of the MWR-retrieved relative humidity profile with respect to the observation from the radiosonde and the automatic station increased with increasing height. Based on the comparison between the MWR and the radiosonde, the authors observed a significant positive correlation between the MWR-retrieved temperature and radiosonde observations over the entire sounding height, which is higher in the lower atmosphere than in the upper atmosphere. In contrast, the correlation of the MWR-retrieved humidity profile with the observation from the radiosonde was significantly lower than that of the temperature profile and exhibited a negative correlation at levels of 2.75–3.5 km. The Mean Error (ME) of the MWR-retrieved temperature profile at each sounding height, except at 10 km, was within 2°C. Meanwhile, the RMSE and AD of the MWR-retrieved temperature profile were about 3.4°C and 2.5°C, respectively, at levels of ＜3 km. Furthermore, the RMSE and AD values of all other levels increased with increasing height. The RMSE and AD of the MWR-retrieved humidity profile were expectedly higher than those of the temperature profile at all levels. Meanwhile, the ME of the MWR-retrieved humidity profile was large at most levels, with a maximum of 23.67%. Precipitation caused the error in the MWR-retrieved temperature profile to increase at the most levels for the duration of 0800 LST and 2000 LST, in which the RMSE and AD under precipitation were expectedly higher than those under the no-rain condition at levels ＞0.5 km. However, the RMSE and AD of the MWR-retrieved humidity profile during 0800 LST and 2000 LST in rainy days (at most levels in the lower atmosphere) were expectedly lower than those during clear days, in which the RMSE and AD at 2000 LST degraded dramatically.