Since then, the land-atmosphere interaction studies have made great progress. In recent years, in addition to the land surface processes’ local and regional effects, studies have revealed that the land surface processes have had remote effects on precipitation and atmospheric circulation at global scale. This presentation reports the results from the GEWEX/LS4P (Impact of initialized land temperature and snowpack on sub-seasonal to seasonal prediction) 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. The LS4P Phase I (LS4P-I) experiment focused on the Tibetan Plateau (TP) LST/SUBT contribution for subseasonal-to-seasonal (S2S) predictability. The summer 2003, when there was a severe drought/flood over the southern/northern part of the Yangtze River basin, respectively, has been selected as the focus case. The cause of the 2003 drought has never been identified. More than forty institutions worldwide have participated in this effort, many of which are the major climate/weather centers.
With the newly developed LS4P initialization method for TP land temperature, the observed surface temperature anomaly over the TP has been partially produced by the LS4P-I model ensemble mean, and 8 hotspot regions in the world were identified where June precipitation is significantly associated with anomalies of May TP land temperature. Consideration of the TP LST/SUBT effect has produced about 25%-50% of observed precipitation anomalies in most hotspot regions. A TP- RM (Rocky Mountains) Circumglobal (TRC) wave train has also been identified. The multiple models have shown more consistency in the hotspot regions along the TRC wave train. This study suggests that the TP LST/SUBT effect is a first-order source of S2S precipitation predictability, comparable in magnitude to that of the sea surface temperature effect.

