Regional Diurnal Variations of Precipitation Parameters Observed with Tropical Rainfall Measuring Mission (TRMM) Microwave
imager (TMI) and TRMM Precipitation Radar (PR)
Fumie Akimoto Furuzawa (1), Kenji Nakamura (1)
(1) Hydrospheric Atmospheric Research Center (HyARC), Nagoya University
Satellite observations of precipitation from space can
get continuous, simultaneous and global informations. These global
observations of rainfall activities with satellites are important
because measurements of rainfall all over the ocean or tropical forest
can be hardly done by ground-based observations. The TRMM satellite
can detect directly obscured precipitation under the clouds by using
microwave more exactly than other infrared or optical satellites.
TRMM satellite has two microwave sensors; a precipitation radar (PR)
and a TRMM microwave imager (TMI). The PR is an active radar which can
determine 3 dimensional structure of precipitation system and
precipitation parameters such as storm type and storm height. The rain
rate is derived from TMI brightness temperatures and PR radar
reflectivities, separately. We analyzed the PR and TMI data over the
ocean, land and coastlines by using the global each-passage data for
June 1998, December 1998 - February 1999 (DJF) and obtained some
results as follows. The PR reveals that 1) rainfall with a low storm
height over land is dominant in winter or from 6 LT to 14 LT. There
exists a convective rain more frequently from 12 LT to 20 LT and a
stratiform rain exists more frequently in winter and from 6 LT to 8
LT. 2) drop size of precipitation has many larger drops from 18 LT to
24 LT for both convective and stratiform rains over the ocean and land
on June and for both convective and stratiform rains over land on
DJF. The diurnal variation is small over the ocean on DJF. Moreover it
has many larger drops at tropics and especially lower in winter
midlatitude, regardless of over the ocean and land on June and DJF.
Especially, small size of precipitations are dominant over Tibetan
plateau and the Andes. 3) monthly rainfall amount is the maximum at 19
LT on June and 15 LT on DJF over land, though TMI shows that the time
is delayed a few hours. Difference between PR and TMI diurnal
variations of rainfall rate is appeared from 10 LT to 17 LT and TMI
rainfall rate is smaller than PR at the period. This is probably due
to frequently appeared convective rain and/or frequently appeared
shallow rain, as shallow rains have smaller TMI rainfall rate than PR
and convective rains have also smaller TMI rainfall rate. Moreover,
this period is coincident with the period without many large rain
drops. This may imply that the TMI underestimates the surface rainfall
rate at the case of rainfall without many large drops. We will discuss
about the relationship on characteristics of rainfall and rainfall
rates derived from PR and TMI.
Submittal Information
Name :
Date :
Fumie Akimoto Furuzawa
09-Aug-04-16:38:29
Organization :
Theme :
Hydrospheric Atmospheric Research Center (HyARC), Nagoya Univ.