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 Meteorology2Sri Lanka Association for the Advancement of Sciences

AIACC Project - AS – 12

Sri Lanka

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

Objectives…

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

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

Downscaling Tools

GCM Based Statistical Downscaling is used

Pattern Scaling Method SimCLIM Software - developed by IGCI,

University of Waikato, New Zealand

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

Climatology of Sri Lanka

Climatological Seasons

First Inter-Monsoon (FIM) March & April

Southwest Monsoon (SWM) May – September

Second Inter-Monsoon (SIM) October & November

Northeast Monsoon (NEM) December – February

Baseline (1961-1990) average Rainfall in

Northeast Monsoon (NEM)

Baseline (1961-1990) average Rainfall in

Southwest Monsoon (SWM)

Baseline (1961-1990) average Rainfall in

First Inter Monsoon (FIM)

Baseline (1961-1990) average Rainfall in

Second Inter Monsoon (SIM)

1961-1990 Baseline average Tmean in Northeast Monsoon

1961-1990 Baseline average Tmean in Second Inter Monsoon

1961-1990 Baseline average Tmean in First Inter Monsoon

1961-1990 Baseline average Tmean in Southwest Monsoon

Observed Climate Changes

in Sri Lanka

Annual minimum air Temperature anomaly trend in Nuwara-Eliya

y = 0.02x - 1.6757

R2 = 0.6888

-2.5-2

-1.5-1

-0.50

0.51

1.5

1901 1909 1917 1925 1933 1941 1949 1957 1965 1973 1981 1989 1997

year

Tm

in A

no

mal

y in

C

(fro

m 1

961-

1990

)

Annual Maximum airTemperature anomaly trend in Nuwara-Eliya

y = -0.0004x + 0.021

R2 = 0.0007

-1.5-1

-0.50

0.51

1.5

1901

1907

1913

1919

1925

1931

1937

1943

1949

1955

1961

1967

1973

1979

1985

1991

1997

year

Tm

ax A

no

mal

y in

C

(fro

m 1

961-

1990

)

       

Annual minimum air Temperature anomaly trend in Puttalam

y = 0.0063x - 0.8009

R2 = 0.2933

-1.5

-1

-0.5

0

0.5

1

1901 1909 1917 1925 1933 1941 1949 1957 1965 1973 1981 1989 1997

year

Tm

in A

no

mal

y in

C (

fro

m

1961

-199

0)

Annual Maximum air Temperature anomaly trend in Puttalam

y = 0.0209x - 1.6402

R2 = 0.6548

-4-3-2-1012

1901

1907

1913

1919

1925

1931

1937

1943

1949

1955

1961

1967

1973

1979

1985

1991

1997

year

Tm

ax A

no

mal

y in

C

(fro

m 1

961-

1990

)

Annual Maximum airtemperature anomaly Colombo

y = 0.0034x - 0.286

R2 = 0.0347

-1.5-1

-0.50

0.51

1.52

2.5

1900

1906

1912

1918

1924

1930

1936

1942

1948

1954

1960

1966

1972

1978

1984

1990

1996

year

Tm

ax A

no

mal

y in

C (

fro

m

1961

-199

0)

Annual minimum air Temperature anomaly trend in Colombo

y = 0.005x - 0.3796

R2 = 0.1976

-1-0.8-0.6-0.4-0.2

00.20.40.60.8

1900 1908 1916 1924 1932 1940 1948 1956 1964 1972 1980 1988 1996

year

Tm

in A

no

mal

y i

n C

(fr

om

19

61-1

990)

• The rate of increase of mean annual air temperature for the 1961-1990 period is in the order of 0.016 0C per year.

Annual rainfall variability in Nuwara-Eliya

-1000

-500

0

500

1000

1500

2000

19

00

19

10

19

20

19

30

19

40

19

50

19

60

19

70

19

80

19

90

20

00

year

RF

an

om

aly

in

mm

(f

rom

19

61

-19

90

)

Annual rainfall variability in Puttalam

-1000

-500

0

500

1000

1500

1900

1910

1920

1930

1940

1950

1960

1970

1980

1990

2000

year

RF

an

om

aly

in m

m (

fro

m

1961

-199

0)

   

Annual rainfall variability in Colombo

-2000

-1500

-1000

-500

0

500

1000

1500

2000

1900

1910

1920

1930

1940

1950

1960

1970

1980

1990

2000

year

RF

an

om

aly

in m

m

(fro

m 1

961-

1990

)

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

 

Season Coefficient of Variation of all Sri Lanka Rainfall

1931 – 1960

1961 - 1990

Northeast Monsoon (Dec. to Feb.)

31% 42%

First Intermonsoon (Mar. to Apr.)

23% 27%

Southwest Monsoon (May. to Sep.)

21% 16%

Second Intermonsoon (Oct. to Nov)

22% 23%

Annual (Jan. to Dec.) 12% 14%

 The Coefficient of Variation of all-Sri Lanka Rainfall during the periods 1931-1960 and 1961-1990.

Future Scenarios

General Circulation Models HadCM3 CGCM CSIRO

Emission Scenarios

A1FI A2 B1

Mean Temperature Change Scenarios in

June 2100

Mean Temperature in June 2100 under the A2

HadCM3

Mean Temperature in June 2100 under the

A1FIHadCM3

Mean Temperature in June 2100 under the B1

HadCM3

Mean Temperature in June 2100 under the A2

CGCM

Mean Temperature in June 2100 under the A1FI

CGCM

Mean Temperature in June 2100 under the B1

CGCM

Mean Temperature in June 2100 under the A2

CSIRO

Mean Temperature in June 2100 under the A1FI

CSIRO

Mean Temperature in June 2100 under the B1

CSIRO

Range of Mean Temperature Increment over the baseline in

June 2100

HadCM3 CSIRO CGCM

A1FI 2.5 – 3.0

2.2 – 2.4 2.0 – 2.2

A2 2.1 – 2.5 1.9 – 2.0 1.7 – 1.8

B1 1.1 – 1.4 1.0 – 1.1 0.9 – 1.0

Rainfall Change Scenarios

in June 2100

Rainfall in June 2050 Under A2HadCM3

Rainfall in June 2025 Under A2HadCM3

Rainfall in June 2100Under A2HadCM3

Rainfall in June 2075 Under A2HadCM3

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.

Acknowledgement

IGCI, University of Waikato, New Zealand is greatly acknowledged

Thank You

Station Topographical Location

Coefficient of Variation (%)

1981 – 1990 1991 - 2000

Colombo Low Country 21% 20%

Galle Low Country 28% 12%

Ratnapura Low Country 23% 15%

Kandy Mid Country 21% 22%

Kenilworth Mid Country 37% 17%

Talawakelle Up Country 28% 21%

Nuwara-Eliya Up Country 26% 13%

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)