Statistical Characteristics of Cloud Precipitation in the Motuo Area Observed by X-band Dual-Polarization Phased Array Radar

During the second comprehensive scientific expedition to the Qinghai Tibet Plateau, an X-band phased array polarimetric radar (X-PAR) was installed in Motuo. For the first time, the most advanced dual-polarization phased array radar is used to continuously observe the precipitation in the valley area. The monthly, diurnal, and altitude variations of echo intensity and echo top height of precipitation in Motuo were quantitatively analyzed using the observation data of Motuo X-PAR from November 2019 to October 2020 to reveal the characteristics of precipitation in the southeast valley of the plateau. The results are then compared to those obtained using Doppler radar during the summer monsoon in Naqu. The results show that: (1) The echo peak height, echo area, proportion of strong echo, and echo distribution range from April to October are greater than those from November to March in Motuo, indicating that the precipitation frequency is high and convective precipitation is more from April to October, particularly in June. However, the increase in the number of weak echoes in April shows that the echo intensity from April to October is less than from November to March. According to the monthly variation characteristics of cloud precipitation in Motuo and the plateau monsoon index, the year is divided into the dry season (November to March) and the rainy season (April to October). (2) The echo frequency, top height, and area of precipitation in the rainy season are higher than those in the dry season. The diurnal variations of echo frequency, top height, and area show that the strongest convection occurs in the afternoon in both seasons. Precipitation occurs primarily in the afternoon and first half of the night during the dry season and in the second half of the night during the rainy season. (3) In Motuo, the echo intensity of precipitation is mostly less than 30 dBZ. The echo frequency is higher both in dry and rainy seasons for altitude >3 km and <3 km, respectively. (4) During the summer monsoon, the echo peak height of Motuo is lower than that of Naqu, and the diurnal variation trend of its peak height and area differs from that of Naqu. Besides, daily precipitation in Naqu is primarily concentrated in the afternoon and the first half of the night. In contrast, precipitation in Motuo is focused mainly in the second half of the night. The characteristics of cloud precipitation in the dry season of Motuo are similar to those in the summer monsoon period of Naqu.