the science of climate change in hawai‘i statistical downscaling of rainfall projections for...
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The Science of Climate Change in Hawai‘i
Statistical Downscaling of Rainfall Projections for
Hawai‘i
Asia Room, East-West Center, 1:30-5:00 pm January 19 & 20,
2011
Oliver Elison Timm1
Thomas W. Giambelluca2
Mami Takahashi2
Henry F. Diaz3
1 International Pacific Research Center, University of Hawaii at Manoa
2 Department of Geography, University of Hawaii at Manoa
3 Earth System Research Laboratory, CIRES, NOAA, Boulder, Colorado
Modelsimulation
20th century
Modelsimulation
21st century
projectedclimate
anomalies
Refinementprocess
projectedchanges in
mean rainfall
projectedchanges in
heavy rainfall
projectedchanges indroughts
From coarse-scale global climate change models to local environmental change
Modelsimulation
20th century
Modelsimulation
21st century
projectedclimate
anomalies
Statisticaldownscaling
projectedchanges in
mean rainfall
projectedchanges in
heavy rainfall
projectedchanges indroughts
From coarse-scale global climate change models to local environmental change
IPCC Fourth Assessment Report, 2007precipitation change for Hawai’i: likely to decrease
Models show a drier climate
Models results inconsistentMost models: drier climate Most models: wetter climate
No significant change Models show a wetter climate
Rain-producing synoptic weather types in Hawai`i(e.g. Chu, Nash and Porter, J. Climate, Vol. 6, 1457-1462, 1993.)
) Frontal system
) Kona storm
) Trade wind
) Ridge wind
monthly mean sea level pressure, Nov-Apr, 1970-2000
HH
High Preciptation Low Preciptation
How does the large-scale circulation control the local rainfall?
Example for Hilo region of Big Island
SLP data from ERA-40 reanalysis
How does the large-scale circulation control the local rainfall?Example for Hilo region of Big Island
9 wettest months 9 driest months
Difference wet-dryRegression Rainfall
vs Projection Index
Wind-based projected changes in seasonally averaged rainfall for Hawai`i(Timm and Diaz, J. Climate, Vol. 22, 4261-4280, 2009)
Histogram of the projected rainfall changes using the six-model ensemble and 134 rainfall stations Histogram of the projected rainfall changes using the six-model ensemble and 134 rainfall stations
Wet season
2070-2099
Dry season
2070-2099
Statistical downscaling with leading modes of climate variability: Southern Oscillation, Pacific North American pattern
=> number of heavy rain event per winter season
500hPa geopotential height anomaly
1000hPa geopot. height anomaly
SO IndexPNA index
Daily rainfall amounts at Naalehu, Big Island
Heavy rain events / wet season (Nov-Apr), Naalehu, Big Island
Number of heavy rain events nn= a0 + a1*SOI +a2*PNA
Statistical downscaling with leading modes of climate variability: Southern Oscillation, Pacific North American pattern
=> number of heavy rain event per winter season
Mean changes for the 12 stations
Observed change
SOI, PNAI estimated change
black: years 1958-1976red: years 1977-2005
1958-1976 1977-2005
Statistical downscaling with leading modes of climate variability:mid 1970s climate shift
Statistical downscaling using Southern Oscillation and Pacific North American Pattern indices:
One model with emissions scenario A1B 2045-2100
Green: present dayRed: 2046-2065Purple: 2081-2100
Green: present dayRed: 2046-2065Purple: 2081-2100
12-station-meanHeavy rain events per wet season
Green: present dayRed: 2046-2065Purple: 2081-2100
Green: present dayRed: 2046-2065Purple: 2081-2100
Statistical downscaling using Southern Oscillation and Pacific North American Pattern indices:
One model with emissions scenario A1B 2045-2100
Statistical downscaling with leading modes of climate variability:
Emissions scenariosA1B A2
The Science of Climate Change in Hawai‘i Statistical Downscaling of Rainfall Projections for
Hawai‘i
Asia Room, East-West Center January 19 & 20, 2011
Oliver Elison Timm1
Thomas W. Giambelluca2
Mami Takahashi2
Henry F. Diaz3
large-scale circulation has strong effect on rain in Hawai`i
slight increase in rainfall during dry months
future climate change projections of IPPC AR4: small reduction in rainfall amounts during the wet months
future trend in mean and heavy rain events still uncertain given the current IPPC AR4 future model projections.
frequency of heavy rain events has decreased in last decades