Investigating the Development of Summertime Planetary Boundary Layer around Ngoring Lake Border over Tibetan Plateau using WRF model: a Case Study

On 28 July 2012, consecutive 3-hourly radio sounding data was obtained around Ngoring Lake border over Tibetan Plateau. The observed results indicated that the low-level structures of planetary boundary layer (PBL) mainly behaved as stable layer during daytime while a nearly neutral layer was sustained from 2300 Local Time (LT) to 0500 LT below 400 m above ground level. It is hypothesized that the thermal effect of the Ngoring Lake likely modulates the PBL structure. Using the weather research and forecasting (WRF) model coupled with lake scheme, we explored the structure and mechanism of the PBL. Six PBL schemes were evaluated for the simulations from 0200 LT 28 July to 0600 LT 29 July 2012, including three non-local closure (i.e., ACM2, YSU, TEMF) and three local closures PBL schemes (i.e., MYJ, Boulac, UW). The results suggested that ACM2 and YSU had a better performance than the others for lake surface temperature, 2m temperature and 2 m specific humidity. In term of PBL depth, only ACM2 reproduced the variance of observation, especially during the nighttime. However, in the wind field, all PBL schemes cannot represent low-level jet of wind speed profile although the wind direction was fairly reproduced. It was found from ACM2 simulation, in the presence of southeast wind, cold (warm) air was advected from Ngoring Lake surface layer southeastly during the daytime (nighttime) and impacted the low-level lake border PBL. Also, lake-land circulation contributed to formation of the above PBL structure. -2016-->>