The Remote Effects of Tibetan Plateau Spring Land Temperature on Global Summer Precipitation—The GEWEX/GASS/LS4P First Phase Activity

Dr. Robert Dickinson has made pioneering contribution on the land surface modeling and land/atmosphere interaction studies. His works has been followed by numerous researches in this fields. In recent years, in addition to the land surface processes’ local and regional effects, studies have revealed the land surface processes’ remote effects. This presentation reports the first phase activity and preliminary results from the GEWEX/Global Atmospheric System Study (GASS)/Impact of initialized land temperature and snowpack on subseasonal to seasonal prediction (LS4P) Initiative, which aims to improve the subseasonal to seasonal prediction (S2S) over different regions through initialization of large scale land surface temperature (LST)/subsurface temperature (SUBT) over high elevation regions in climate models.

Basin-wide tropical sea surface temperature (SST) anomalies are known to play a major role in causing extreme events, such as droughts and floods. SST has been shown to have predictive value for land precipitation. The predictive skill for precipitation anomalies, however, in spring and summer months has remained stubbornly low for years. Encouraged by preliminary studies, which reveals the effect of the spring LST/SUBT in Rocky Mountains and Tibetan Plateau on the later spring/summer downstream drought/flood/heat waves (Xue et al., 2016, 2018; Diallo et al., 2019), the GEWEX/GASS/LS4P project is the first that introduces spring LST/SUBT anomalies over the high mountain areas as a factor to improve the S2S precipitation prediction. East Asia has been selected as the focus area in the first phase experiment because of the presence of the high elevation Tibetan Plateau and the availability of large observational data from the Third Pole Experiment (TPE). More than forty (40) institutions world-wide, which include many major meteorological centers, are participating in the LS4P. Three tasks have been defined. Based on the preliminary results from the experiments assigned in the three tasks and data analyses of observational data, it has been established that, for the first time, the spring LST/SUBT in Tibetan Plateau may have a global impact on summer precipitation and its S2S prediction. The potential hot spots of Tibetan Plateau effects have been identified: they are the eastern part of China, South Asia, mid-latitude North America, Northern S. America, Sahel, West Europe and Eurasian continent, along with Indonesia and Australia. Meanwhile, preliminary results have also shown that for many climate models it is a great challenge to preserve the imposed LST/SUBT anomalies and to reproduce the observed land surface anomalies. More tests with improved soil memory will be conducted to further confirm these effects and potentially identify more hot spots in the world. The success in the first phase research raises further scientific questions and opens the door for more research on LST/SUBT effect and relevant mechanisms.

Reference

Diallo, I., Y. Xue, Q. Li, F. De Sales, W. Li, (2019). Dynamical downscaling the impact of spring Western U.S. land surface temperature on the 2015 flood extremes at the Southern Great Plains: Effect of domain choice, dynamic cores and land surface parameterization. Climate Dynamics 53(1-2), 1039-1061. DOI: https://doi.org/10.1007/s00382-019-04630-6

Xue, Y., C. M. Oaida, I. Diallo, J. D. Neelin, S. Li, F. De Sales, Y. Gu, D. A. Robinson, R. Vasic, L. Yi, (2016). Spring land temperature anomalies in northwestern US and the summer drought over Southern Plains and adjacent areas. Environmental Research Letter, 11(4), 044018, doi:10.1088/1748-9326/11/4/044018.

Xue Y., I. Diallo, W. Li, J. D. Neelin, P. C. Chu, R. Vasic, W. Guo, Q. Li, D. A. Robinson, Y. Zhu, C. Fu, and C. M. Oaida (2018). Spring land surface and subsurface temperature anomalies and subsequent downstream late spring-summer droughts/floods in North America and East Asia. Journal of Geophysical Research: Atmospheres, 123, 5001-5019. https://doi.org/10.1029/2017JD028246