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Inter-annual Southwest Monsoon Variability and ENSO Impacts in Thailand

Study on the influence of ENSO on the Southwest Monsoon in Thailand using meteorological data and climatology analyses to understand wind patterns and the onset of the rainy season.

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Inter-annual Southwest Monsoon Variability and ENSO Impacts in Thailand

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  1. Inter-annual Variation of Southwest Monsoon and ENSO in Thailand KornraweeSitthichivapakThai Meteorological Department

  2. Research Team • Ms. KornraweeSitthichivapak, Director, Climatology Center. • Mr. Charoon Laohalertchai, Director, Northern Meteorological Center, Chiangmai. • Ms. SugunyaneeYavinchan, Director, Numerical Weather Prediction.

  3. Objective • To study impact of ENSO on SW Monsoon over Thailand • To study mechanism of SW Monsoon, linking to ENSO

  4. Data • 30 years (1971 – 2000) meteorological data • Parameters: MSLP, Wind at 850 and 200 hPa • Climatological data from TMD • Data Reanalysis from ECMWF

  5. Methodology • Analyze monthly wind direction and its speed from July to September at 850 and 200 hPa • Compare monthly wind direction and its speed between ENSO year and neutral year

  6. Method (cont’) • Analyze pattern winds for starting and ending of the rainy season (account for topography) • Compare pattern winds for starting and ending of the rainy season between ENSO year and neutral year

  7. Benefits • To know the variability of the wind patterns for starting and ending of the rainy season • To know the variability of the wind patterns during the SW monsoon in the ENSO year.

  8. Mechanism of Monsoon • Monsoon is the result of the shift of the Inter Tropical Convergence Zone (ITCZ) under the influence of the vertical sun • the South East Trade winds of the Southern Hemisphere have to cross the equator to reach the ITCZ • Coriolis effect in northern hemisphere to turn to its right are deflected eastwards in the Northern Hemisphere transforming into South West trades. • orographic rain

  9. MAY

  10. JUNE

  11. JULY

  12. AUGUST

  13. SEPTEMBER

  14. OCTUBER

  15. Edward Linacre and Bart Geerts:1997 Surface windupper wind

  16. Analyze the climate pattern oscillations and start / end of rainy seasons during neutral and ENSO years

  17. Climate pattern during May 1988 is Lanina year the active southwest monsoon prevail Andaman sea and Thailand 1980 is a neutral year Southwest wind prevail Andaman sea , southern Thailand and upper Thailand • is a El ni no year • Westerly wind prevail • Andaman sea and Thailand

  18. Climate pattern during October 1980is a neutral year the active Easterly wind prevail south China sea , upper Thailand. The Southern Thailand is westerly wind. 1997 is Elnino year Easterlywind prevail South China Sea and Thailand. 1988 is a Lanina Year Northeast wind prevail Northeast Thailand For Southern Thailand is active westerly wind

  19. ComparisonSW Monsoon System • 850 and 200 hPamean wind JJAS in neutralyear • 850 and 200 hPamean wind JJAS in strong El- Nino year • 850 and 200 hPamean wind JJAS in strong La- Nina year

  20. 850 and 200 hPamean wind JJAS in neutralyear

  21. neutral year (850 hPa Mean wind JJAS )

  22. neutral year (200 hPa Mean wind JJAS )

  23. 850 and 200 hPamean wind JJAS in strong El-Ninoyear

  24. 850 and 200 hPamean wind JJAS in strong La-Ninayear

  25. The pattern of southwest monsoon system during June –September

  26. 200 hPa

  27. Variability of the pattern southwest monsoon system during June –September in El nino /La nina Year

  28. ศูนย์ภูมิอากาศ กรมอุตุนิยมวิทยา Climatological Center The Meteorological Department(TMD) On set of summer monsoon over Thailand Criteria used by the Thai meteorological Department • Upper level, westerly wind is changed to easterly • Lower level, wind is changed to westerly or southwest wind • In any 5-day period, there must be at least 3continuous days with rain, or the total 5-day rain must be at least 25 mm with the minimum daily rain of 5 mm.

  29. ศูนย์ภูมิอากาศ กรมอุตุนิยมวิทยา Climatological Center The Meteorological Department(TMD) Onset of rainy season in Thailand (1971-2000) May El nino Lanina Neutral

  30. conclusion • Analysis data from 1971-2000 found that • Neutral year : the beginning of rainy season is mostly mid May • El nino year : the beginning of rainy season is late than neutral year • La nina year : the beginning of rainy season is earlier than neutral year • Analysis of monsoon pattern during May found that • La nina year : Southwest monsoon prevail over the Andaman sea, Thailand and the Gulf of Thailand is stronger and clearer than neutral year and El nino year. • El nino year : Mostly westerly wind prevail the Andaman sea Thailand and the Gulf of Thailand • For the end of rainy season is mostly mid October all condition.

  31. The pattern of the monsoon season from June to September. El nino year : 850 hPa • Southwest monsoon prevail over upper Thailand and more active than normal 200 hPa • Easterly wind prevail over Thailand and active than normal La nina Year : 850 hPa • Southwest monsoon prevail over upper Thailand and weakly than normal 200 hPa • Easterly wind prevail over Thailand and weakly than normal

  32. Thank You for your kind Attention

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