B. Distribution of occurrence and contribution
Fig.1 shows the distribution of daily rainfall in different
rainfall classes along with their contribution to the total
rainfall in different years. It is seen that no rain is the largest
occurrence rainfall range, occurred almost half of the total
days and the second largest class is 0-3mm, occurred about
20-30% of the total days in gauges rainfall situation. While,
the statistical results for TRMM rainfall situation are opposite
to that in gauges rainfall situation, the largest rainfall
occurrence is 0-3mm, account for about 40% of the total days
and no rain situation is followed (account for about 30%). It
can also be seen that although the occurrences of small rain
(0-3mm) are as high as 40-50% of the total days, the
contribution to the total rain amount are only about 4% in any
3757
rainfall data.
It is important to note that the high rainfall ranges play a
significant role in contributing rain amount to the total rainfall.
The high rainfall classes (>50mm) occurs only about 1.1%
(maximal 3% in 1998) of the total days and contributes 22.4%
average (maximal 32.5% in 1998) of the total rainfall for rain
gauge data and 15% average (maximal 38.3% in 1998) for
TRMM data. The occurrences of the middle class rainfall
ranges (3-50mm) are general equivalent (account for 27.7%
average) for rain gauge and TRMM rainfall data in every year,
but different for the contribution to the total rainfall. For class
3-10mm, the statistical results for TRMM rainfall situation are
match well with its counterpart in every year. And for range
10-25mm, the contribution is larger in 2000 and smaller in
2001 than the ones of rain gauge rainfall, in other years they
are nearly equivalent each other. Except for 1998, the larger
contributions are received for TRMM rainfall data in class
25-50mm. So, the daily TRMM rainfall data are good at
determining rain occurrence rather than determining the
rainfall amount.