ESE315 Assignment 7

1. [20 credits] Describe the three circulation cells of the atmosphere's mean meridional circulation (MMC). Draw schematically on a globe the circulation, surface wind directions, surface pressure systems, and distribution of precipitation. Describe how surface pressure and precipitation are linked to the MMC.
2. [20 credits] Describe what the Gulf Stream is, how it is formed, and what it does to the climates in the North Atlantic.
3. [20 credits] Describe the 'thermohaline circulation'. What is it driven by? Draw the overall structure of the global thermohaline circulation for the current climate.
4. [20 credits] Draw, using the NCEP reanalysis dataset, the climatological January and July surface pressure (contours) and surface wind patterns (vectors or wind barbs). Mark the subtropical high pressure systems around the world associated with the descending air of the Hadley cell.
5. [20 credits] In the previous plot, mark the spatial area of Asian monsoon, using the following criterion: the prevailing wind direction shifts 120 degrees between January and July. You are only required to roughly estimate this by eye. You are not required to do a calculation for the change in wind direction.

By the way, the above criterion is only one of the four classic monsoon criteria proposed by Ramage in 1971. The four criteria were:

• Prevailing wind shifts 120° between January and July
• Average frequency of prevailing wind > 40%
• Speed of mean wind exceeds 3 m/s
• Pressure patterns satisfy a steadiness criterion