Rainfall

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Rainfall Temperature Scenarios for Sri Lanka
under the anticipated Climate Change B.R.S.B.
Basnayake1, Janaka Ratnasiri2, J.C.
Vithanage2 1Centre for Climate Change Studies,
Department of Meteorology 2Sri Lanka Association
for the Advancement of Sciences AIACC Project
- AS 12 Sri Lanka
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Outline..

• Objectives
• Downscaling of GCM
• Baseline (1961 1990) climatology
• Observed Climate Change in Sri Lanka
• Temperature change Scenarios under the A1FI, A2
  B1 Scenarios with HadCM3, CGCM CSIRO
• Rainfall change Scenarios under the A2 Scenario
  with HadCM3
• Conclusion

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Objectives

• Projection of Rainfall Temperature Scenarios,
  which are applicable to Sri Lanka based on
  General Circulation Model (GCM) results

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Downscaling of GCM

• Since Sri Lanka is an Island
• Resolution power of the grid points of the GCMs
  (300 km X 300 km) are not sufficient enough
• High diversity of altitude from sea level within
  short distance

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Downscaling Tools

• GCM Based Statistical Downscaling is used
• Pattern Scaling Method
• SimCLIM Software - developed by IGCI, University
  of Waikato, New Zealand

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Baseline (1961 1990) Climatology

• ANUSPLIN Software developed by Australian
  National University (ANU) is used to spatially
  interpolate the rainfall and temperature fields
  with terrain effect

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• Climatology of Sri Lanka

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Climatological Seasons

• First Inter-Monsoon (FIM)
• March April
• Southwest Monsoon (SWM)
• May September
• Second Inter-Monsoon (SIM)
• October November
• Northeast Monsoon (NEM)
• December February

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Baseline (1961-1990) average Rainfall in
Southwest Monsoon (SWM)
Baseline (1961-1990) average Rainfall in
Northeast Monsoon (NEM)
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Baseline (1961-1990) average Rainfall in Second
Inter Monsoon (SIM)
Baseline (1961-1990) average Rainfall in First
Inter Monsoon (FIM)
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1961-1990 Baseline average Tmean in Northeast
Monsoon
1961-1990 Baseline average Tmean in Second Inter
Monsoon
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1961-1990 Baseline average Tmean in First Inter
Monsoon
1961-1990 Baseline average Tmean in Southwest
Monsoon
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Observed Climate Changes in Sri Lanka
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• The rate of increase of mean annual air
  temperature for the 1961-1990 period is in the
  order of 0.016 0C per year.

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• Annual average of rainfall over Sri Lanka has
  been decreased by about 7, during 1961 to 1990
  period compared to 1931 to 1960 period.
•  

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The Coefficient of Variation of all-Sri Lanka
Rainfall during the periods 1931-1960 and
1961-1990.
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Future Scenarios
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General Circulation Models

• HadCM3
• CGCM
• CSIRO

• Emission Scenarios
• A1FI
• A2
• B1

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Mean Temperature Change Scenarios in June 2100
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Mean Temperature in June 2100 under the A2 HadCM3
Mean Temperature in June 2100 under the
A1FI HadCM3
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Mean Temperature in June 2100 under the B1 HadCM3
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Mean Temperature in June 2100 under the A2 CGCM
Mean Temperature in June 2100 under the A1FI CGCM
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Mean Temperature in June 2100 under the B1 CGCM
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Mean Temperature in June 2100 under the A2 CSIRO
Mean Temperature in June 2100 under the A1FI CSIRO
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Mean Temperature in June 2100 under the B1 CSIRO
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Rainfall Change Scenarios in June 2100
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Rainfall in June 2050 Under A2 HadCM3
Rainfall in June 2025 Under A2 HadCM3
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Rainfall in June 2075 Under A2 HadCM3
Rainfall in June 2100 Under A2 HadCM3
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Conclusions

• Projected Mean Temperature increases under
  different scenarios for different GCM models with
  varying magnitudes.
• Projected June Rainfall increases with HadCM3
  under A2 Scenario. The increments are much more
  higher on the western slopes of the central hills
  (windward side) compared to leeward side.

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Acknowledgement

• IGCI, University of Waikato,
• New Zealand is greatly acknowledged

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• Thank You

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The Coefficient of Variation of southwest monsoon
rainfall at selected stations in low, mid and up
country regions during 1981-1990 and 1990-2000
periods (Basnayake and Punyawardane, 2003)