Vertical variation of TRMM Precipitation rate in the western Pacific area
Sento Nakai (1), Yukari N. Takayabu (2)
(1) Nagaoka Institute of Snow and Ice Studies, NIED
(2) Center for Climate System Research, University of Tokyo
TRMM/PR 2A25 data were utilized for the analysis of precipitation profile in the western Pacific area. Main purpose is to clarify the difference of precipitation structures between tropics, subtropics and midlatitude. Comparison between precipitation over ocean and that over land were also made. Our interest is in deep precipitation so that shallow precipitation was excluded from the analysis. We designed two-dimensional histograms of precipitation rate R and precipitation increase E(ŬR^(|Ŭz)) versus altitude z. E-z histogram in subtropics and midlatitude in warm period showed similar characteristics to that of tropics. In case of stratiform precipitation, absolute value of E was small at all levels except large positive E at levels of 4-5 km followed by small E at levels of 3-4 km. These deviations of E from zero may be caused by melting of ice-phase precipitation particles. Positive E dominated at levels of 5-6 km in convective precipitation. These levels were higher than positive-E dominant levels of stratiform precipitation, and the growth of precipitation particles by collection was suggested. Convective precipitation was characterized by large deviation of E from zero below 7 km. Especially below 4 km, negative E appeared to the same extent as, and occasionally more frequently than positive E. Depletion of rain by evaporation was quite usual. It was revealed by R-z histogram that the depletion was mainly occurred in weak rain areas. E-z histograms of subtropics and midlatitude in cold period showed the similar characteristics to upper part of the corresponding histograms of the tropics as if the negative temperature difference biased the altitude. Stratiform precipitation over land showed similar characteristics to the corresponding stratifom precipitation over ocean. Convective precipitation over land showed positive E deviation larger than the precipitation over ocean. Negative deviation of convective precipitation over land was largest at a level of 3 km. Mean E distribution in R-z plane showed that the maximum negative E-deviation was composed of enhancement of strong precipitation below 8 km, and of depletion of medium precipitation below 3 km. E deviation of stratiform precipitation was small, however, it tended to be positive above freezing level and negative below.
