Climate Means and Climate Variability Scenarios for Mainland Southeast Asia for Impact and

Vulnerability Assessments

Anond Snidvongs1

John L. McGregor2

Nguyen Kim Chi2

Wirote Laongmanee1

Weerasak Weerakant1

Jantira Ratanarat1

1Southeast Asia START Regional Center, Bangkok, Thailand2CSIRO Atmospheric Research, Aspendale, Australia

Outline

Why do we need climate mean and climate variability

CCAM for SE domain and its ‘raw’ outputs

Empirical adjustment of CCAM rainfall outputs

Climate change scenario for each sub-domain

Our scenarios in comparison with others

Projected climate means and variability for each sub domain and at our 3 IV&A Assessment sites

CCAM for Southeast AsiaSome Important Features•18 vertical levels•Final output domain: 5o-35o N and 92o-110o E•Output resolution was interpolated to 0.1o (about 10 km)

Some Selected Daily Outputs•Tmax, min and avg T (oC)•Rainfall (mm/d)•Wind speed (m/s) and direction•Radiation (W/m2)•Specific humidity (kg/kg)•Heat flux (W/m2)•Pressure (hPa)•Cloud cover (%)

Putting Time Slice into the Scenario

•CCAM was run for 10 years each at 360 ppm CO2 baseline, 540 ppm (1.5xCO2) and 720 ppm (2xCO2)

540 ppm

720 ppm

Based on SRES A1FI these CO2 levels correspond to:

•360 ppm 1980-89•540 ppm 2040-49•720 ppm 2066-75

CCAM Output and Verification: Temperature

CCAM Output and Verification: Precipitation

Nan, Thailand

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Udon Thani, Thailand

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Problems with CCAM rainfall outputs

1. Slightly overestimate the annual rainfall2. Rainfall season onset delayed by 8-10 weeks3. Daily variation not large enough4. Overestimate number of rain days

CCAM Precipitation Output Adjustment

Key Principle: Preserve original CCAM spatial and temporal resolutions

•Made statistical adjustment based on cumulative rainfall using a non-linear function to exponentially increase the daily variability•An arbitrary rainfall threshold of 3 mm/day was applied to reduce number of rain days

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CCAM ‘Rescaled’ Output: Precipitation

Udon Thani, Thailand

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Nan, Thailand

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Compare ours with other global scenarios

DEC-JAN 2066-75

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-2 -1 0 1 2 3 4 5 6Temperature Change (oC)

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MK Delta

N Thai

MAR-MAY 2066-75

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JUN-AUG 2066-75

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SEP-NOV 2066-75

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Precip (billion cu.m/qtr)

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Lao PDR (176,100 km2) Mar-Apr-May

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Lao PDR (176,100 km2) Jun-Jul-Aug

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Lao PDR (176,100 km2) Sep-Oct-Nov

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Lao PDR (176,100 km2) Dec-Jan-Feb

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Upper Chao Phraya (116,900 km2) Jun-Jul-Aug

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Upper Chao Phraya (116,900 km2) Sep-Oct-Nov

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Upper Chao Phraya (116,900 km2) Dec-Jan-Feb

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Upper Chao Phraya (116,900 km2) Mar-Apr-May

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NE Thailand (145,200 km2) Jun-Jul-Aug

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NE Thailand (145,200 km2) Sep-Oct-Nov

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NE Thailand (145,200 km2) Dec-Jan-Feb

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NE Thailand (145,200 km2) Mar-Apr-May

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Mekong Delta (30,100 km2) Dec-Jan-Feb

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Mekong Delta (30,100 km2) Mar-Apr-May

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Mekong Delta (30,100 km2) Jun-Jul-Aug

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Mekong Delta (30,100 km2) Sep-Oct-Nov

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Tmax Tmin Precip SolarUbon Rachathani, Thailand

360 ppm 540 ppm 720 ppm

12 May 14 Oct 23 Apr 17 Oct 24 Apr 23 Oct

Ubon Rachathani, Thailand

2. More distinct mid-season dry spell at 540 ppm 3. More continuous rainy season at 720 ppm and total rain increased by about 10%4. More cloud overcastting could compensate for temperature rise

1. Rainfall season onset will be earlier by about 20 days at 540 and 720 ppm

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Ubon Rachathani, Thailand360 ppm 540 ppm 720 ppm

Srad Srad Srad

Precip Precip Precip

Tmax Tmax Tmax

Tmin Tmin Tmin

Seasonal and Annual VariabilityUbon Rachathani, Thailand

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Tmax Tmin Precip SolarSavannakhet, Lao PDR

360 ppm 540 ppm 720 ppm

16 May17 Oct 5 May

13 Oct13 May 16 Oct

Savannakhet, Lao PDR

3. More cloud overcastting could compensate for less temperature rise

1. At 540 ppm, rainfall season onset will be earlier by about 10 days and offset be delayed slightly but no substantial change in total rainfall2. At 720 ppm, only slight shift in rainfall season but total rainfall will be increased by about 20%

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Savannakhet, Lao PDR360 ppm 540 ppm 720 ppm

Srad Srad Srad

Precip Precip Precip

Tmax Tmax Tmax

Tmin Tmin Tmin

Seasonal and Annual VariabilitySavannakhet, Lao PDR

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Tmax Tmin Precip SolarLong An, Vietnam

360 ppm 540 ppm 720 ppm

9 May5 Nov

29 Apr27 Oct

1 May30 Oct

Long An, Vietnam

1. At 540 and 720 ppm, both rainfall season onset and offset will be earlier by about 10 days

3. At 720 ppm the total rainfall will be increased by about 10% but rainfall in Qtr 4 will be less

2. At 540 ppm mid-season dry spell could be more prominent but not so at 720 ppm

Seasonal and Annual VariabilityLong An, Vietnam

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Long An, Vietnam360 ppm 540 ppm 720 ppm

Srad Srad Srad

Precip Precip Precip

Tmax Tmax Tmax

Tmin Tmin Tmin

Site 360 ppm 540 ppm 720 ppm

Ubon Rachathani 76 74 93

Savannakhet 88 83 105

Long An 60 63 79

Average # of days with T > 33 oC

Average # of days with T < 15 oC

Site 360 ppm 540 ppm 720 ppm

Ubon Rachathani 13 17 9

Savannakhet 26 34 19

Long An 0 0 0

Some Conclusions and Implications

1. Under elevated CO2 environment the mean climate of the region will be slightly more wet (10-20%) and more warm (1-2 oC) which may only has a slight effect on water resource (or even be positive impact)

2. Even though the mean climates (T and Precip) will generally not be much affected by CO2 increase but the change in climate variability and seasonality will be more important and the rain-fed agricultural sector is naturally more susceptible to this

3. Inland part of the Mekong Basin (i,.e., Lao PDR and Thailand) has a more abrupt rainy season onset than the delta part (I.e., Vietnam). Ability to do seasonal forecast for rainfall onset will certainly increase capacity of rice farmer to cope with future change in climate variability