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Wind-evaporation feedback, angular momentum conservation, and the abrupt onset of monsoons

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dc.contributor.advisor Kerry A. Emanuel. en_US
dc.contributor.author Boos, William R. (William Ronald), 1975- en_US
dc.contributor.other Massachusetts Institute of Technology. Dept. of Earth, Atmospheric, and Planetary Sciences. en_US
dc.date.accessioned 2008-11-07T19:08:52Z
dc.date.available 2008-11-07T19:08:52Z
dc.date.copyright 2008 en_US
dc.date.issued 2008 en_US
dc.identifier.uri http://hdl.handle.net/1721.1/43149
dc.description Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2008. en_US
dc.description Includes bibliographical references (p. 167-174). en_US
dc.description.abstract This thesis examines the mechanisms responsible for the abrupt onset of monsoon circulations, focusing on the role played by wind-evaporation feedback and its interaction with angular momentum conserving flow. The first half of the thesis examines the effect of wind induced surface heat exchange (WISHE) on nonlinear, axisymmetric Hadley circulations in a convective quasi-equilibrium framework. For thermal forcings localized off the equator, WISHE is found to reduce the critical forcing amplitude needed to produce angular momentum conserving flow. For forcings that are subcritical even with the effects of WISHE, the combination of WISHE and momentum advection is shown to nonlinearly enhance the circulation strength for all but the weakest forcings. These results hold for the time-dependent response to seasonally varying forcings: for forcings of intermediate strength, WISHE produces an abrupt onset of solsticial flow when only a linear response would otherwise occur, while for strong forcings WISHE shifts the abrupt onset to an earlier time in the seasonal cycle. The second half of the thesis examines the consistency of these idealized results with the onset of the South Asian monsoon in both observations and a detailed three-dimensional model. Observational composites of monsoon onset are consistent with a wind-evaporation feedback in that the increase in baroclinic flow during onset is accompanied by a large increase in surface enthalpy flux over the off-equatorial ocean. This increase in surface enthalpy flux is collocated with the peak increase in deep tropospheric ascent. Results from the three-dimensional numerical model were less conclusive in that this model did not successfully simulate an abrupt monsoon onset even with WISHE, although WISHE did strongly control the intensity and spatial structure of the model's mean summer circulation. en_US
dc.description.abstract (cont) In particular, a version of the model integrated without WISHE failed to produce a strong, angular momentum conserving monsoon circulation. Combined with the axisymmetric model results from the first half of the thesis, this suggests that the thermal forcing of the South Asian land mass may not be sufficiently strong in the absence of WISHE to produce angular momentum conserving monsoon flow. en_US
dc.description.statementofresponsibility by William Ronald Boos. en_US
dc.format.extent 174 p. en_US
dc.language.iso eng en_US
dc.publisher Massachusetts Institute of Technology en_US
dc.rights M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. en_US
dc.rights.uri http://dspace.mit.edu/handle/1721.1/7582 en_US
dc.subject Earth, Atmospheric, and Planetary Sciences. en_US
dc.title Wind-evaporation feedback, angular momentum conservation, and the abrupt onset of monsoons en_US
dc.type Thesis en_US
dc.description.degree Ph.D. en_US
dc.contributor.department Massachusetts Institute of Technology. Dept. of Earth, Atmospheric, and Planetary Sciences. en_US
dc.identifier.oclc 247997786 en_US


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