Antarctic atmospheric Richardson number from radiosoundings measurements and AMPS

• Main Authors: Yang, Qike, Wu, Xiaoqing, Hu, Xiaodan, Wang, Zhiyuan, Qing, Chun, Luo, Tao, Wu, Pengfei, Guo, Yiming
• Format: Text
• Language: English
• Published: 2022
• Subjects: Antarctic; South Pole; The Antarctic; Antarc*; South pole
• Online Access: https://doi.org/10.5194/acp-2022-352; https://acp.copernicus.org/preprints/acp-2022-352/

Monitoring a wide range of atmospheric turbulence over the Antarctic continent is still tricky, while the atmospheric Richardson number ( Ri a critical parameter determining the possibility of turbulence could be triggered) is easier to obtain. The Antarctic atmospheric Ri , calculated using the temperature and wind speed, was investigated using the daily results from the radiosoundings and forecasts of the Antarctic Mesoscale Prediction System (AMPS). Radiosoundings for a year at three sites (McMurdo, South Pole, and Dome C) were used to quantify the reliability of the AMPS forecasts. The AMPS-forecasted 1/ Ri (inverse of the Richardson number) can identify the main characteristics of atmospheric turbulence over the Antarctic continent in terms of space and time. The correlation coefficients ( R xy ) of 1/ Ri at McMurdo, South Pole, and Dome C are 0.71, 0.66, and 0.68, respectively, where the performance gains during the warm seasons. In addition, a model to improve AMPS-forecasted 1/ Ri has been presented. The monthly median at the three sites and the seasonal median throughout the two vertical cross-sections for the AMPS forecasts are presented. One can observe that the probability of triggering turbulence is primarily concentrated near the ground. In addition, strong wind shears near escarpment regions have been found in the range of 0–5 km above the ground, thus causing atmospheric instability (or a thick boundary layer). In addition, turbulent atmospheres are likely to be triggered over the ocean, moving toward the Antarctic Plateau and becoming stable. Finally, the 1/ Ri at the planetary boundary layer height ( PBLH ), 1/ Ri PBLH , has been provided as a reference standard for judging atmospheric stability. The median value of 1/ Ri PBLH from the combined data of two vertical cross-sections was 0.55, which was used to calculate PBLH and agree well with the AMPS forecasts ( R xy >0.72).