[A-AS03] Large-scale moisture and organized cloud systems

[AAS03-P07] Remote effects of typhoon on the water vapor transport over western Japan

*Atsushi Hamada^1,2, Yuichiro Kusano³, Bunmei Taguchi¹, Kazuaki Yasunaga¹ (1.Faculty of Sustainable Design, University of Toyama, Toyama, Japan, 2.Center for Environmental Remote Sensing, Chiba University, Chiba, Japan, 3.Graduate School of Science and Engineering, University of Toyama, Toyama, Japan)

Keywords:water vapor, typhoon, atmospheric river

A statistical analysis on the remote effects of typhoons on the moisture fluxes over Kyushu Island, Japan, were conducted, by selecting typhoons that did not approach Japan. We focused on temporal changes in vertically integrated horizontal water vapor flux (eastward one as IEF) and vertically integrated water vapor (IWV) during the days before and after the time when the central pressure of each typhoon was at its lowest (time of maximum development).

The results showed that both the IEF and IWV tended to reach their maximum around Kyushu Island 3–4 days after the time of maximum development. Composite analyses of the atmospheric field were conducted using the cases in which the IEF reached maximum 2–5 days after the time of maximum development. The results showed that a meridional pressure gradient around Kyushu was enhanced by the formation of high-pressure anomalies in the southern part of Kyushu and low-pressure anomalies in the northern part about 3 days after the time of maximum development. The meridional pressure gradient enhanced the westerly wind, resulting in an increase of the IEF. The high and low-pressure anomalies are found to be a part of wave trains like the PJ and EU patterns, respectively.

We also analyzed the factors that caused the IWV enhancement over Kyushu. A positive IWV anomaly appeared around eastern China about 2 days before the time of maximum development, and moved eastward and reached the Kyushu area. A positive relative humidity anomaly in the mid-to-upper troposphere is observed associated with the IWV enhancement, implying a formation of environmental field that is preferring to produce extreme precipitation.