Spatial contrast of Asian dust concentration between windward and leeward of mountains in Japan during 1-2 April 2007

[ABSTRACT]During massive Asian dust episode for 1-2 April 2007, mass concentration of suspended particulate matter (SPM) rapidly began to increase in the morning on 1 April from coastal side of the Japan Sea. For the daytime 1 April, while rapid SPM increase and extreme high concentrations observed in Hokuriku and Tohoku, SPM concentrations in Kanto remained low level and increased from late afternoon. Ground lidar observation and rawinsonde sounding in Hokuriku show that the top height of dust layer (~ 2 km) approximately correspond to the base of temperature inversion. In Kanto, SPM increase began from east coast and then it advanced westward after 15 LT with easterly wind. The CloudSat/CPR and CALIPSO/CALIOP observations show that clouds over mainland Japan and the Japan Sea was found in the upper-level (> 6 km). Continuous meteorological observations show that cloud condensation and rainfall was not observed over mountains for the daytime 1 April. These results suggest that the temporal delaying of SPM increase in Kanto was caused by an indirect dust transport.