Tropical cyclone Remote Precipitation (TRP) is an unusual phenomena associated with tropical cyclones. The precipitation area would usually appear in front of and distantly away from the cyclones (Chen et al. 2010). The real time operational forecast is hard to predict the distribution and rate of TRP because which is separated with and away from tropical cyclone itself.

Very heavy rainfall were often appeared in the area around Bohai sea and North China when a typhoon approached or made landfall in south-east coast of China. Both of them are closely related each other. The north rainfall actually is the TRP of the south typhoon. The satellite remotely sensed data can display the rate and distribution of the TRP. Satellite data analysis also shows that TRP phenomena were not only appeared in China but also in Japan. For example, typhoon Songda (0419) with recurving track made landfall in Kyushu on 7 Sep. 2004. In earlier stage, when Songda was in 1300 km south away from Japan on 4 Sep. 2004, extensive heavy rain of TRP was distributed and covered all of Japan. This is the typical TRP for Songda. A serial satellite image in 3-5 Sep. 2004 had displayed the formation and variation of the TRP with typhoon Songda (Wang et al. 2009). TRP phenomena is also appeared in United States associated with Hurricane in Atlantic with different terminology of PRE (Predecessor Rain Events Ahead of Tropical Cyclone)

Statistical analysis shows in China (Cong Chunhua, 2011) that 14.7 % tropical cyclones would produce TRP events in the years of 1971-2006, that imply TRPs are small probability events. Majority of TRP would last more than two days with high rate and extensive distribution. TRP is preferred to appear in July and August. Diagnostic analysis indicates TRP is produced by the interaction between typhoon and mid-latitude westerly trough. Topography also plays an important role for TRP. The characteristics of favorable circulation for TRP in low layer are that there is a deep westerly trough in the north to a typhoon. The moisture transported by peripheral south east flow of typhoon can reach northward distant area in front of the westerly trough. The typhoon circulation is connected with a south west (east) wet flow channel such as a series of cloud cluster in monsoon surge. On the other hand, the upper level divergent area south to the jet stream is overlapped the area where TRP occur.

The numerical experiments demonstrate that the strength of TRP is closely related to typhoon, mid-latitude trough and the terrain effect. The sensitive simulation (Wang et al. 2009) shows that the remote precipitation would greatly decrease if the typhoon is removed. The another sensitive numerical experiment (Cong et al. 2011) shows that the rate of TRP has a direct ratio to strength of the mid-latitude trough. It's also found that the rate of TRP would decrease in certain degree if remove the topography. The numerical simulation on typhoon Tim (Zhu 2000) indicates that the intensity of typhoon would influence the rate and distribution of TRP.

Bibliography

Chen Lianshou, Li Ying, Cheng Zhengquan, 2010: An overview of research and forecasting on rainfall associated with landfalling tropical cyclones. Advances in Atmospheric Sciences, 27(5):967-976.

Cong Chunhua, Chen Lianshou, Li Ying, Lei Xiaotu, 2011: On the study of the mechanism of tropical cyclone remote precipitation. Acta Meteorologica Sinica (waiting for print).

Yongqing Wang, Yuqing Wang, H. Fudeyasu, 2009: The role of typhoon Songda (2004) in producing distantly located heavy rainfall in Japan. Monthly Weather Review, 137:3699-3716.

Zhu Hongyan, Chen Lianshou, Xu Xiangde. 2000: A numerical study of the interaction between typhoon and mid-latitude circulation and its rainfall characteristics, Chinese Journal of Atmospheric Sciences, 24(5):668-675.