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“Traditional” terminology

Arabic word “mausim” means“season” “Traditional” terminology Loose definition: a wind/precipitation pattern that shifts seasonally Classical criteria (Ramage 1971) Prevailing wind shifts 120 o between Jan & July Average frequency of prevailing wind > 40%

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“Traditional” terminology

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  1. Arabic word “mausim” means“season” “Traditional” terminology Loose definition: a wind/precipitation pattern that shifts seasonally Classical criteria (Ramage 1971) Prevailing wind shifts 120o between Jan & July Average frequency of prevailing wind > 40% Speed of mean wind exceeds 3 m/s Pressure patterns satisfy a steadiness criterion Classical Example: Indian Monsoon

  2. N. H. Summer Other Examples North American West African African Winter (Indian Summer) East Asian N.W. Australian N. H. Winter

  3. Tibetan plateau: range of 60°C Ocean: range of 3 to 5°C Surface temperature range that results in the monsoon Sea surface temperature variations are much smaller than land surface temperature variations. (Mainly the seasonal cycle) Kump et al. text (2004)

  4. Monsoon schematic Wallace and Hobbs textbook (1977)

  5. Combined Monsoon System (Webster et. al. 1988)

  6. Orography(Webster et. al. 1988)

  7. Upper Tropospheric Temperature JJA DJF

  8. 90 E Upper Tropospheric Temperature Seasonal Variation 30 N Jan July 110 W Dec 90 E 110 W

  9. 250 mbZonal Wind(JJA) Wind Upper Trop Temp

  10. 250 mbZonal Wind(DJF) Wind Upper Trop Temp

  11. Vertical Motions (Webster et. al. 1988)

  12. Meridional Circulation, 90E 1978-79 (Yanai et. al.)

  13. Trade winds June-August winds Dec-Feb winds(SW monsoon) (NW monsoon) SW monsoon winds NE monsoon winds

  14. 5N Jan Meridional Wind 925 mb 5N - 925 - July 5N 925 mb 5N - 925 -

  15. Zonal Wind(JJA) Wind up to 100 mb (0-120 E) (0-40 E)

  16. 3-d View (Webster et. al. 1988)

  17. Outgoing Longwave Radiaton SON SON JJA DJF MAM DJF

  18. Indian Monsoon - Rainfall 1963, 71

  19. Indian Monsoon - Interannual Variability -1

  20. Indian Monsoon - Interannual Variability -2

  21. (*) Eastward progression of regions of both enhanced and suppressed tropical rainfall, mainly over the Indian Ocean and Pacific Ocean. (*) Anomalous rainfall is usually first evident over the western Indian Ocean; propagates over warm western and central tropical Pacific. (*) Pattern of tropical rainfall weakens/disappears over the cooler waters of the eastern Pacific; reappears over the Atlantic and Indian Ocean. (*) Each cycle lasts approximately 30-60 days (*) Apparently anti-correlated with El Nino Madden-Julian Oscillation

  22. MJO-mature

  23. (material from second Webster chapter not included here)

  24. North American Monsoon -1

  25. (Late June - Early September) North American Monsoon - description * Summer daytime heating over the Sonoran Desert of Mexico and Arizona forms large surface low-pressure cell over the region, * The low draws moist tropical air from the Gulfs of California and Mexico, triggering thunderstorms as it is lifted by the mountains and solar heating. * The monsoonal circulation does not produce thunderstorms every day but rather occurs in a pattern that has "bursts" and "breaks:" Burst: A movement of a weak trough in the upper level westerly wind into the southwest U.S. which spreads upper level cold air into the region. In the lower levels of the atmosphere, strong surface heating and southerly winds transport moisture into the region, creating unstable conditions and leading to widespread thunderstorm outbreaks. "Break: An enhanced ridging of the Pacific subtropical High Pressure moves inland, effectively cutting off the moisture flow and stabilizing the atmosphere"

  26. Late June - Early September Burst and Break Burst Break weak disturbances in the upper atmosphere act to focus thunderstorm activity over the 4 corners for a period of a few days to more than a week

  27. More on the North American Monsoon On a typical Arizona Monsoon day, thunderstorms initially develop I n the early afternoon over the higher mountains and the Mogollon Rim. Rain-cooled air from these thunderstorms descends from the high country and into the desert. Acting like a cold front, this mesoscale outflow induces the hot desert air to rise, again producing thunderstorms. Over the higher deserts, they usually occur during the mid to late afternoon, while over the lower deserts storm activity is most common during the late afternoon and evening. Generally, thunderstorm activity ceases around midnight.

  28. North American Monsoon - more description During the monsoon season, the region receives most of its annual precipitation, approximately 35 to 45 percent for Arizona and New Mexico and 60 percent for northern Mexico. For example, Acapulco rainfall totals 51.8 inches June-October (more than 9 inches each month except October), while only 3.3 inches falls during the rest of the year.

  29. North American Monsoon - rainfall

  30. July 500 mb height High Anticyclonic circulation around High involves flow from Gulfs of California and Mexico into Northwest Mexico and Southwest US

  31. May October 500 mb heights: May, August, October August High

  32. North American Monsoon - setup and decay

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