1. High resolution climate simulations and future change over Vietnam
Kim Nguyen, Jack Katzfey and John McGregor
9-14th December 2012
Melbourne

2. OUTLINES
Conformal Cubic Atmospheric Model (CCAM) simulation forced by ERA-Interim at 20 km over Vietnam (preliminary study)
Rainfall for the wet and dry half years compared against GPCP (2.5 degree), CRU (0.5 degree) and APHRODITE (0.25 degree)
Inter-annual variability of rainfall and El Nino Southern Oscillation (ENSO)
2. Changes in rainfall by 2030 using results from the previous project (PCCSP, CMIP3 high emission scenario A2) 60 km CCAM global simulation

3. CCAM SURFACE ELEVATION
Elevation (meter)

4. MSLP AND 1000 hPa WIND April to September (summer half year)
Southwesterly from Bay of Bengal
Cross-equatorial flow from the Southern Hemisphere
April to September
(summer half year)
October to March
(winter half year)
Northeasterly originated from Mongolia and northern China merges with easterly flow from the Pacific
MSLP AND 1000 hPa WIND
plot_climatic_wind.jnl

5. SUMMER MONSOON MEAN RAINFALL
April to September
High rainfall on the windward side and less rain on the lee ward side (rain shadow)

6. WINTER MONSOON MEAN RAINFALLNE
WINTER MONSOON MEAN RAINFALL
October to March
High rainfall along windward side of the Truong Son range

7. RAINFALL BIAS April to September October to March
Rainfall bias in mm day-1, with red overestimation and blue underestimation and only bias at 95th significant level shown
RAINFALL BIAS
April to September
October to March

8. MONTHLY RAINFALL AMOUNT AND BIAS AVERAGED OVER VIETNAMmm

9. APR-SEP
OCT-MAR
-14.75
North Vietnam
North VN

10. APR-SEP
OCT-MAR
Central Vietnam
Central VN

11. APR-SEP
OCT-MAR
South Vietnam
South VN

12. ENSO

13. Interannual variability of rainfall and ENSO
ENSO is defined using Nino 3.4 index.
El Nino/La Nina when all Nino 3.4 indices of the season are at least 0.5oC above/below normal.
Neutral season when all Nino 3.4 indices of the season are between -0.5oC and +0.5oC, exclusively
Wet season (summer monsoon) from April to September
Dry season (winter monsoon) from October to December of the current year and January to March of the following year

14. RAINFALL ANOMALY APRIL TO SEPTEMBER In general, rainfall over Vietnam
influence of ENSO is moderate and patchy
slightly above normal in neutral years
slightly below normal under both ENSO phases, except for the southern tip of South Vietnam, where rainfall above normal under La Nina years
RAINFALL ANOMALY
APRIL TO SEPTEMBER
above normal
everywhere
slightly above normal
below normal
In the wet season, ENSO moderately and patchy influences rainfall over VN maybe due to wind is south-westerly
Explain what is El Nino, La Nina and neutral

15. RAINFALL ANOMALY OCTOBER TO MARCH
ENSO has strong influence on rainfall along the east coast of Vietnam.
El Nino (La Nina) years, rainfall along the east coast is below (above) normal.
below normal
above normal
In El Nino years, rainfall is below normal may be TC genesis is shifted east to central and eastern Pacific. Whereas in La Nina years, TC genesis is closer to VN, rainfall is above normal.
Also, wind has two components: northeasterly and easterly from the Pacific. This easterly is weaken in El Nino and strengthen in La Nina years

16. PREDICTION OF FUTURE RAINFALL CHANGE OVER VIETNAM BY 2030
USING PREVIOUS PROJECT (PCCSP, CMIP3, A2) CCAM 60 KM GLOBAL SIMULATIONS

17. SURFACE ELEVATION

18. RAINFALL CHANGE BY 2030 IN GFDL2.1
OCT-MAR
APR-SEP
CCAM
OBS rainfall trend (%/year )
Increase rainfall
decrease rainfall

19. RAINFALL CHANGE BY 2030 IN ECHAM5
OCT-MAR
APR-SEP
CCAM
OBS rainfall trend (%/year )

20. RAINFALL CHANGE BY 2030 IN UKMO HadCM3
APR-SEP
OCT-MAR
UKMO
UKMO
Rainfall changes in mm day-1, with red increase and blue decrease and stippling shows changes at 95th significant level
The host GCM UKMO HadCM3 shows changes not significant in both seasons, except for the southern tip VN, where rainfall is predicted to decrease with significant in wet season VN
CCAM
CCAM shows increase in both seasons along the east coast with significant only in the wet season

21. CONCLUSIONS
Climatic rainfall for the wet and dry seasons over Vietnam and surrounding regions was validated against observed GPCP, CRU and APHRODITE. CCAM captures well the mean rainfall patterns for both seasons and closely resembles APHRODITE rainfall patterns
Influence of ENSO on rainfall over Vietnam
in the wet season: patchy and moderate, above normal rainfall in neutral years
in the dry season: strongly along the east coast, El Nino (La Nina) years rainfall is below (above) normal.
Future changes: CCAM forced by host GFDL2.1 SST captures well observed rainfall trend. CCAM projects rainfall increase along the east coast and decrease in the north Vietnam.

22. THANK YOU
CCAM Downscaling for Viet Nam | Kim Nguyen

23. CCAM Downscaling for Viet Nam | Peter Hoffmann

24. Keith Linda CCAM OBS Tropical depression < 34 knots
Low resolution and not well defined pressure center

25. RAINFALL CHANGE BY 2030 IN ECHAM5
Rainfall changes in mm day-1, with red increase and blue decrease and stippling shows changes at 95th significant level
The host GCM ECHAM5 shows decrease/increase in wet/dry season but not significant
CCAM shows increase in both seasons from south of central to north Vietnam, but significant only over central Vietnam
The differences between CCAM and host GCM rainfall change in the wet season is mainly over orography
RAINFALL CHANGE BY 2030 IN ECHAM5
ECHAM5
OCT-MAR
APR-SEP
CCAM

26. RAINFALL CHANGE BY 2030 IN GFDL2.1
Rainfall changes in mm day-1, with red increase and blue decrease and stippling shows changes at 95th significant level
The host GCM GFDL2.1 shows changes not significant in dry season. In wet season, rainfall is predicted to decrease with significant over Cambodia, south and north VN
RAINFALL CHANGE BY 2030 IN GFDL2.1
GFDL2.1
OCT-MAR
APR-SEP
CCAM
CCAM shows increase in wet season along the east coast

27. CCAM SURFACE ELEVATION
Central Vietnam
South China Sea
Bay of Bengal
Tibetan Plateau
Thailand
Cambodia
Laos
North
South
Vietnam
CCAM SURFACE ELEVATION
Elevation (meter)
20km resolution region