An objective index of the onset and demise of the Indian summer monsoon (ISM) is introduced. This index has the advantage of
simplicity by using only one readily available variable, All-India rainfall (AIR), which has been reliably observed for more than a
century. The proposed All-India rainfall onset and demise (AIROD) is shown to be insensitive to all recorded false onsets. By definition,
the seasonal ISM rainfall anomalies become a function of the variations of onset and demise dates, with early onset and late demise
resulting in greater season length and total seasonal rainfall. Seasonal rainfall itself is a strong predictor of the following ENSO phase
and provides a more accurate depiction of the ISM than does the commonly-used June-September (JJAS) All-India monsoon rainfall (AIMR)
index. This new index provides an accurate and comprehensive representation of the seasonal evolution of the ISM by capturing dramatic
changes in large-scale dynamic (i.e. wind- and current-based) and thermodynamic (temperature- and moisture-based) variables, which is
found to make the onset an especially important feature to monitor to understand the evolution of the ensuing monsoon season. In
particular, the zonal (meridional) progression of 300hPa meridional temperature gradient (meridional ocean heat transport) reversal may be
monitored about twenty days before onset to help determine the timing of its arrival. Interannual variability of ISM features and their
associated large-scale phenomena are also analyzed. An early (late) onset corresponds to an increase (decrease) in anomalies of kinetic
energy of 850hPa wind over the Arabian Sea and central Indian rainfall up to fifteen and ten days before onset, respectively. Conversely,
an early (late) demise corresponds to a decrease (increase) in the aforementioned anomalies up to ten days after demise. Additionally, the
preceding December-February ENSO phase is associated with the onset of the ISM, as an early (late) onset is preceded by La Niña (El
Niño). / A Thesis submitted to the Department of Earth, Ocean and Atmospheric Sciences in partial fulfillment
of the Master of Science. / Spring Semester 2016. / March 24, 2016. / Circulations, Index, India, Monsoon, Onset, Rainfall / Includes bibliographical references. / Vasubandhu Misra, Professor Directing Thesis; Robert Hart, Committee Member; Mark Bourassa,
Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_360412 |
| Contributors | Noska, Ryne Garrett (authoraut), Misra, Vasubandhu (professor directing thesis), Hart, Robert E. (Robert Edward) (committee member), Bourassa, Mark Allan (committee member), Florida State University (degree granting institution), College of Arts and Sciences (degree granting college), Department of Earth, Ocean, and Atmospheric Science (degree granting department) |
| Publisher | Florida State University, Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource (109 pages), computer, application/pdf |
| Rights | This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). The copyright in theses and dissertations completed at Florida State University is held by the students who author them. |
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