design rainfalls for australia - australia's official … modelling workshop 3–6 october 2005...
TRANSCRIPT
BMRC Modelling Workshop 3–6 October 2005
Revision of Design Rainfalls for Australia:A Pilot Study – Part 1
Dörte Jakob,1 Brian Taylor2 and Karin Xuereb2
Bureau of Meteorology (1BMRC, 2Hydrology)
BMRC Modelling Workshop 3–6 October 2005
Terminology - design rainfall
• IFD - intensity frequency duration
• DDF - depth duration frequency
• AR&R - Australian Rainfall and Runoff
BMRC Modelling Workshop 3–6 October 2005
Intensity-frequency-duration curves
Duration5M 10M 30M 1H 2H 6H 24H
1
5
10
20
50
100
200
Rai
nfal
l Int
ensi
ty (m
m/h
our)
72H 1 year 5 years 20 years100 years
ARI
ARIaverage recurrence interval
BMRC Modelling Workshop 3–6 October 2005
50-year 7-day precipitation (inches)
Source: HDSC (Hydrometeorological Design Studies Center)
BMRC Modelling Workshop 3–6 October 2005
50-year 7-day precipitation (inches)
16
16Up to 15 inches in Louisiana between 24 August and 1 September 2005, 14.82’’ in Big Branch, LA
(Source: Wikipeda)
BMRC Modelling Workshop 3–6 October 2005
Summarising sample properties
Rainfall measurements
Annual maximum series
Ordered Sample
Location
Scale
Skewness
L-moments
BMRC Modelling Workshop 3–6 October 2005
Rainfall frequency curve
Return period in years
Brisbane Regional Office
(129 annual maxima, duration 1 day)
BMRC Modelling Workshop 3–6 October 2005
Climate variability
Franks and Kuczera(2002)
Expected two-parameter lognormalquantiles and their 90% probability limits for Barwon River @Brewarrina(NSW). Samples stratified 1930–1945 and 1946–1983.
BMRC Modelling Workshop 3–6 October 2005
Location of gauges
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28°S 28°S
27°S 27°S
�0 5025
Kilometres
! Daily
#* Continuous
�) Alert gauge
!( DIPNR/DNRM
BMRC Modelling Workshop 3–6 October 2005
Regionalisation approachesRegion – set of sites, usually geographically contiguous, frequency curves are approximately the same (apart from a scaling factor)
‘Spider web’ approach ‘Region of influence’ approach
Clusters Circles
RT = RMED xT
frequency curve = index rainfall * growth curve
BMRC Modelling Workshop 3–6 October 2005
Mapping index
rainfall
Index rainfall – median of annual maxima at a site, scaling factor
ANUSPLIN – software developed at ANU Canberra, employing technique of thin-plate spline smoothing
BMRC Modelling Workshop 3–6 October 2005
Grids of index rainfall (24 hours)
ARR87 Pilot study
BMRC Modelling Workshop 3–6 October 2005
http://www.bom.gov.au/hydro/has/hrs10.shtml
HYDROLOGY REPORT SERIES
HRS Report No. 10
A PILOT STUDY TO EXPLORE METHODS FOR
DERIVING DESIGN RAINFALLS FOR AUSTRALIA -
PART 1
Hydrology Unit
Melbourne
June 2005
Link to report