QUNATITATIVE PRECIPITATION FORECASTING USING CLOUD-BASED
TECHNIQUES ON AVHRR DATA
L Billa, S.B. Mansor, A.R. Mahamud
SNML, ITMA,University Putra Malaysia,43400 Serdang, Selangor, Malaysia
biwal2000@yahoo.com , (shattri, arm)@eng.upm.edu.my
Commission V11, WG V11/5
KEYWORDS: Real- time, High resolution, Precipitation, Modeling, Classification, Processing,
Estimation,
ABSTRACT
Tri-yearly recurrence of flooding in Malaysia has made floods the most important significant natural disaster in the country in terms of
cost and damage to property. Many hydrological and hydraulic flood models have been implemented but are yet to meet the requirement
of a near real-time flood forecasting. This study envisage the "Nowcasting System" through the operational coupling of quantitative
precipitation forecasting (QPF) in remote sensing with hydrological and hydraulic oriented GIS to argument the problem. The paper
presents the first phase of the study in the application of cloud model-based techniques in the extraction of precipitation from NOAA-
AVHRR data for flood warning system. It discusses object oriented cloud classification techniques using Ecognition software to identify
major cumulus cloud types. Cloud brightness temperature (TB) threshold levels are established and evaluated based on the digital number
values in channels 1 & 2 of the AHVRR data. The intensity and dimensions of rain baring pixels are measured after a mask has been
applied to extrude clouds and various enhancements and filtering processes. Estimates of expected precipitation are derived based on the
assumption that every cloud pixel has a constant unit rain-rate of 3mm, which is appropriate for tropical precipitation over 2.5% %i2.5%
arcas around the equator. «
Over the years various flood forecasting and warning system
based on an advanced hydraulic model has been applied in
Malaysia. However, the systems have been limited to the
forecasting of water levels in the major rivers. These forecasts
proved inadequate for their inability to predict impending
floods thus, they have had limited effect in reducing costs and
damage to life and property due to flood (Figl). As it's
understood that it neither possible nor desirable to stop flood
completely the is a shift in the approach to flood early warning.
Hydrologists are recognizing the practical limitations of rain
gauges for measuring mean rainfall over large areas and
inaccessible areas. They are increasingly turning to remote
sensing as a possible means for quantifying the precipitation
input in hydrological models, particularly in areas in of few
surface gauges.
Introduction
Malaysia experiences some form of flood every year due to its
tropical location between latitude 7N and 5S and also it being
in the path of the adverse effects the monsoon weather
phenomena. It has two monsoons seasons a year, the north-east
that occur from November to March and the south-west
monsoons from May to September. In between the two
monsoons are the two inter-monsoon periods in April and
October that are generally characterised by variable winds and
thunderstorm in the afternoon. According to the history there is
a serious flood vent every three years.
see
AT Sn +
Fig1. Flash Flood in Malaysia 2003 Fig 2. Langat River Basin
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