| This study aims to make a regional characterization of the performance of
the rain retrieval algorithm BRAIN. This algorithm estimates the rain rate
from brightness temperatures measured by the TRMM Microwave Imager (TMI)
onboard the TRMM satellite. In this stage of the study, a comparison between
the rain estimated from Precipitation Radar (PR) onboard TRMM (2A25 version
5) and the rain retrieved by the BRAIN algorithm is presented, for about 30
satellite overpasses over the Central and Eastern Mediterranean during the
period October 2003–March 2004, in order to assess the behavior of the
algorithm in the Eastern Mediterranean region. BRAIN was built and tested
using PR rain estimates distributed randomly over the whole TRMM sampling
region. Characterization of the differences between PR and BRAIN over a
specific region is thus interesting because it might show some local trend
for one or the other of the instrument.
The checking of BRAIN results against the PR rain-estimate appears to be
consistent with former results i.e. a somewhat marked discrepancy for the
highest rain rates. This difference arises from a known problem that affect
rain retrieval based on passive microwave radiometers measurements, but some
of the higher radar rain rates could also be questioned.
As an independent test, a good correlation between the rain retrieved by
BRAIN and lighting data (obtained by the UK Met. Office long range detection
system) is also emphasized in the paper. |