Suginori Iwasaki

Seasonal Variations of Precipitation Properties Associated with the Monsoon over Palau in the Western Pacific

Abstract In this study, the authors focused on the seasonal variations of precipitation properties over the western Pacific, particularly those associated with the wind direction of the monsoon. An observational project over Peleliu Island in the Republic of Palau was carried out, and data on precipitation, equivalent cloud amount, and precipitable water were collected from 28 June 2001 to 30 April 2002. First, the monsoon season over Palau was defined as a period with 850-hPa zonal-wind sounding data with sustained winds exceeding 5 m s−1. The westerly wind regime continued until 25 November 2001, and the next westerly wind regime began on 18 May 2002. The equivalent cloud amount increased during the period when the westerly wind intensified. The precipitation had a diurnal variation in the active phase of the westerly wind regime, increasing from nighttime to early morning and decreasing in the afternoon. The diurnal variation was weak in the inactive phase and had a lesser afternoon maximum. Precipitat...

Convective vertical velocity and cloud internal vertical structure: An A‐Train perspective

This paper describes a novel use of A-Train observations to estimate vertical velocities for actively growing convective plumes and to relate them to cloud internal vertical structure. Convective vertical velocity is derived from time-delayed (1–2 min) IR measurements from MODIS and IIR. Convective vertical velocities are found to be clustered around 2–4 m/s but the distributions are positively skewed with long tails extending to larger values. Land convection during the 13:30 overpasses has higher vertical velocities than those during the 1:30 overpasses; oceanic convection shows the opposite, albeit smaller, contrast. Our results also show that convection with larger vertical velocity tends to transport larger precipitation-size particle and/or greater amount of water substance to higher altitude and produces heavier rainfall. Finally, we discuss the implications of this study for the designs of future space-borne missions that focus on fast-evolving processes such as those related to clouds and precipitation.

Cloud observation with CRL airborne cloud profiling radar (SPIDER)

Cloud profiling radar can measure global distribution of cloud. Not only the information of the height of cloud tops and bases but also the information of particle shapes and water content (including whether ice or water) are expected. Multiparameter function of radar can be used for such purpose and the precise calibration of radar is necessary. The possibility for usage of sea surface return as an external calibration target is proposed because is stable under known condition of sea state. In addition, results of airborne measurements will be shown.