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Kornrawee Sitthichivapak Thai Meteorological Department

Inter-annual Variation of Southwest Monsoon and ENSO in Thailand. Kornrawee Sitthichivapak Thai Meteorological Department. Research Team. Ms. KornraweeSitthichivapak, Director, Climatology Center. Mr. Charoon Laohalertchai, Director, Northern Meteorological Center, Chiangmai.

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Kornrawee Sitthichivapak Thai Meteorological Department

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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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