Raman lidar measurement of water vapor and ice clouds associated with Asian dust layer over Tsukuba, Japan

The vertical distributions of particle extinction, backscattering, depolarization, and water vapor mixing ratio were measured using a Raman lidar over Tsukuba (36.1 degreesN, 140.1 degreesE), Japan, on 23 - 24 April 2001. Ice clouds associated with the Asian dust layer were observed at an altitude of similar to 6 - 9 km. The relative humidities in the cloud layer were close to the ice saturation values and the temperature at the top of the cloud layer was similar to - 35 degreesC, suggesting that the Asian dust acted as ice nuclei at the high temperatures. The meteorological analysis suggested that the ice-saturated region was formed near the top of the dust layer where the moist air ascended in slantwise fashion above the cold-frontal zone associated with extratropical cyclone.