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The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction

The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction. Update prepared by Climate Prediction Center / NCEP August 1, 2011. For more information, visit: http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Asian_Monsoons/Asian_Monsoons.shtml. Outline.

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The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction

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  1. The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction Update prepared by Climate Prediction Center / NCEP August 1, 2011 For more information, visit:http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Asian_Monsoons/Asian_Monsoons.shtml

  2. Outline • Recent Evolution and Current Conditions • Monsoon Prediction • Summary • Climatology

  3. Precip Patterns: Last 90 Days During the past 90 days, above-average rainfall was observed over South Asia and the Bay of Bengal except the below-average rainfall over southern and western India. Above-average rainfall was also observed the South China Sea and the western Pacific Ocean. On the other hand, below-average rainfall was seen over East Asia and part of Southeast Asia except the above-average rainfall over Korea and southern Japan. Below-average rainfall was also found over much of the Indian Ocean.

  4. Precip Patterns: Last 30 Days During the past 30 days, above-average rainfall was observed over eastern Arabian Sea, southern Tibetan Plateau, the Bay of Bengal, Korea, the South China Sea, and the western Pacific Ocean. Below-average rainfall was seen over eastern India, eastern China, part of Southeast Asia, and eastern Indian Ocean.

  5. Precip Patterns: Last 5 Days In the past week, the pattern of rainfall anomalies was featured by a structure of four latitudinal bands. Below-average rainfall was observed over 17º-30ºN and 10ºS-equator, and above-average rainfall was found over 0º-17ºN (especially the South China Sea and the Philippine Sea) and 30º-40ºN.

  6. Rainfall Time Seriesover 5x5 lat-lon boxes • *This unified land-only daily precipitation dataset is different from the CMAP dataset used in the previous three spatial maps. • The East Asian Mei-yu/Baiu/Changma has been overall above average this year especially over Korea and southern Japan, in spite of the complex structure over eastern China. • Although below-average rainfall appears over Sri Lanka and southern and western India, the monsoon rainfall over northern and eastern India has been above average this summer. 6

  7. Atmospheric Circulation In the past week, the anomalies of lower-tropospheric winds were characterized by the weaker-than-observed monsoon westerly flow over 15º-22ºN and a cyclonic pattern over the South China Sea and the Philippine Sea. The cross-equatorial flow over the Indian Ocean was stronger than normal.

  8. NCEP/GFS Model Forecasts Bias-Corrected Precip. Anom. for Weak 1 & Week 2 Week-1 Week-2

  9. Prediction of Large-Scale Monsoon Circulation Upper panel: Webster-Yang monsoon index (Webster and Yang 1992) defined as U850 (0-20ºN, 40-110ºE) – U200 (0-20ºN, 40-110ºE).Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that the Webster-Yang monsoon index will be below normal in the next two weeks. Lower panel: Correlation between rainfall and Webster-Yang monsoon index (Webster and Yang 1992; shading) and regression of 850-mb winds on the monsoon index (vectors) for August. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon.

  10. Prediction of South Asian Monsoon Upper panel: South Asian monsoon index (Goswami et al. 1999) defined as V850-V200 over 10-30ºN, 70-110ºE.Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that, in the next two weeks, the South Asian monsoon circulation will be normal. Lower panel: Correlation between rainfall and South Asian monsoon index (Goswami et al. 1999; shading) and regression of 850-mb winds on the monsoon index (vectors) for August. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon. 10

  11. Prediction of East Asia – NW Pacific Monsoon Upper panel: East Asia – Western North Pacific (EAWNP) monsoon index (Wang et al. 2008) defined as U850 (5-15ºN, 40-80ºE) – U850 (20-30ºN, 70-90ºE). Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that, in the next two weeks, the monsoon circulation over Southeast Asia and northwestern Pacific will be mainly near normal. Lower panel: Correlation between rainfall and East Asia – Western North Pacific monsoon index (Wang et al. 2008; shading) and regression of 850-mb winds on the monsoon index (vectors) for August. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon.

  12. Summary • In the past week, the pattern of rainfall anomalies was featured by a structure of four latitudinal bands. Below-average rainfall was observed over 17º-30ºN and 10ºS-equator, and above-average rainfall was found over 0º-17ºN (especially the South China Sea and the Philippine Sea) and 30º-40ºN. • The NCEP Global Forecast System predicts that the Asian monsoon circulation is overall near or below normal in the next two weeks, with above-average rainfall over northeastern India and Korea during week-1 and above-average rainfall over Pakistan, southeastern China and Korea but below-average rainfall over central and southwestern China in week-2.

  13. Onset of the Asian Monsoon

  14. Demise of the Asian Monsoon

  15. Climatology

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