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The Science of Climate Change in Hawai‘i

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 Timm 1 Thomas W. Giambelluca 2 Mami Takahashi 2 Henry F. Diaz 3.

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The Science of Climate Change in Hawai‘i

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  1. 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

  2. From coarse-scale global climate change models to local environmental change Model simulation 20th century projected changes in heavy rainfall projected climate anomalies Refinement process projected changes in mean rainfall Model simulation 21st century projected changes in droughts

  3. From coarse-scale global climate change models to local environmental change Model simulation 20th century projected changes in heavy rainfall projected climate anomalies Statistical downscaling projected changes in mean rainfall Model simulation 21st century projected changes in droughts

  4. IPCC Fourth Assessment Report, 2007 precipitation change for Hawai’i: likely to decrease Models show a drier climate No significant change Models show a wetter climate Most models: drier climate Models results inconsistent Most models: wetter climate

  5. Rain-producing synoptic weather types in Hawai`i (e.g. Chu, Nash and Porter, J. Climate, Vol. 6, 1457-1462, 1993.) ) Frontal system ) Trade wind ) Ridge wind ) Kona storm

  6. How does the large-scale circulation control the local rainfall? Example for Hilo region of Big Island monthly mean sea level pressure, Nov-Apr, 1970-2000 High Preciptation Low Preciptation H H SLP data from ERA-40 reanalysis

  7. 9 wettest months 9 driest months How does the large-scale circulation control the local rainfall? Example for Hilo region of Big Island Regression Rainfall vs Projection Index Difference wet-dry

  8. 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 Dry season 2070-2099 Wet season 2070-2099

  9. Statistical downscaling with leading modes of climate variability: Southern Oscillation, Pacific North American pattern => number of heavy rain event per winter season Daily rainfall amounts at Naalehu, Big Island 500hPa geopotential height anomaly 1000hPa geopot. height anomaly Heavy rain events / wet season (Nov-Apr), Naalehu, Big Island PNA index SO Index

  10. Statistical downscaling with leading modes of climate variability: Southern Oscillation, Pacific North American pattern => number of heavy rain event per winter season Number of heavy rain events n n= a0 + a1*SOI +a2*PNA

  11. Statistical downscaling with leading modes of climate variability: mid 1970s climate shift Observed change black: years 1958-1976 red: years 1977-2005 1958-1976 1977-2005 Mean changes for the 12 stations SOI, PNAI estimated change

  12. Statistical downscaling using Southern Oscillation and Pacific North American Pattern indices: One model with emissions scenario A1B 2045-2100 Green: present day Red: 2046-2065 Purple: 2081-2100 12-station-mean Heavy rain events per wet season

  13. Statistical downscaling using Southern Oscillation and Pacific North American Pattern indices: One model with emissions scenario A1B 2045-2100 Green: present day Red: 2046-2065 Purple: 2081-2100

  14. Statistical downscaling with leading modes of climate variability: Emissions scenarios A1B A2

  15. 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 • future climate change projections of IPPC AR4: • small reduction in rainfall amounts during the wet months • slight increase in rainfall during dry months • frequency of heavy rain events has decreased in last decades • future trend in mean and heavy rain events still uncertain given the current IPPC AR4 future model projections.

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