THESIS
2022
1 online resource (xxix, 269 pages) : illustrations (some color)
Abstract
The monsoons are often viewed as sea-breeze circulations driven by solar radiations and
land-sea thermal contrast, and modified by compressibility and rotation effects. This
highly idealized model is recently improved by considering a fully coupled land-ocean-atmosphere
nature of the monsoon. In East Asia, the monsoons are further shaped by the
unique geographical setting and weather dynamics. During the Meiyu season, a quasi-stationary
monsoon front stretching thousands of kilometers wide perennially causes
torrential rains and severe floods. This brings us to a few core questions: Where did all
those water vapors come from when apparently local evaporation does not suffice to
supply all of them? How can we understand the monsoons better from the perspective
of moisture?
This thesis co...[
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The monsoons are often viewed as sea-breeze circulations driven by solar radiations and
land-sea thermal contrast, and modified by compressibility and rotation effects. This
highly idealized model is recently improved by considering a fully coupled land-ocean-atmosphere
nature of the monsoon. In East Asia, the monsoons are further shaped by the
unique geographical setting and weather dynamics. During the Meiyu season, a quasi-stationary
monsoon front stretching thousands of kilometers wide perennially causes
torrential rains and severe floods. This brings us to a few core questions: Where did all
those water vapors come from when apparently local evaporation does not suffice to
supply all of them? How can we understand the monsoons better from the perspective
of moisture?
This thesis contains four main chapters address the above questions. By backtracking
the moisture two weeks before precipitation using a reanalysis-driven semi-Lagrangian
model, we established a moisture source-receptor (SR) network for multiple regions in
East Asia during the warm season. The network reveals an equal (or even greater)
importance of non-local terrestrial sources compared to the oceanic sources. The network
also demonstrates pronounced intraseasonal variabilities and is further shaped by the El
Niño Southern Oscillation. Four main moisture corridors are found to sustain the heavy
monsoon rainbands in East Asia. Interesting circumglobal wave trains attributable to the
pathways are discovered at a two-week lead time. Applying a more sophisticated 3-D
Lagrangian moisture tracking model on the global scale, we find that 62% of continental
precipitation is sustained by terrestrial evaporation. The world’s leading moisture
sources and a new concept of cascading moisture recycling are also proposed. The final
study discovers a dual regime of MCSs closely tied to the monsoon annual cycle and
reveals the prevailing environments for convective initiation under the two regimes.
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