| Summary: | Extreme rainfall event is one of natural events frequently generating
serious impact to many sectors. To date, its characteristic is expected being
changing due global climate change. The study was aimed to identify the spatio-
temporal characteristics of extreme rainfall events over Java Island, Indonesia by
focusing analysis to East Java Province.
Some extreme indices calculated as annual series, were generated from
rainfall record within period of 1981 � 2010. The maximum number of
consecutive wet days, number of days where daily rainfall is more than or equal to
20 mm, 50 mm and 90
th
percentile were chosen to represent the frequency of
extreme rainfall events. Meanwhile the highest 1-day rainfall amount, the highest
5-day rainfall amount, annual total and daily rainfall intensity were selected to
represent the intensity of the events. A set of quality control procedures including
duplicated data check, spatial outliers check, missing value check and
homogeneity test was applied prior the analysis. The spatial characteristic of those
events was identified by mapping climatological mean of indices while temporal
characteristic was assessed using the non-parametric Mann-Kendal test.
The quality control procedures selected 84 stations as high quality data
from total of 461 rainfall stations. The spatial pattern of extreme rainfall events
over East Java Province is generally characterized by low frequency and intensity
in the coastal area, and high frequency and intensity in the mountainous area. The
dominant finding from trend assessment is not-significant trend. However, the
consistently significant trend was observed in some districts. Rain stations in
District of Ponorogo, Ngawi, Bojonegoro, Gresik and Sumenep showed
significant negative trend for almost all indices whereas significant positive trend
was found in District of Surabaya and Pasuruan.
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