Geoscience Reference
In-Depth Information
June.
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On an interannual time-scale, the year-to-year variability of the
SCSSM onset date and intensity in May has a strong projection onto the
summer rainfall anomalous pattern in the East China and West Pacific
Ocean, foreshadowing the development of the full-scale Asian summer
monsoon during the subsequent months.
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These scientific issues have
called for a multi-national atmospheric and oceanographic observational
and research plan, the SCS Monsoon Experiment (SCSMEX), which was
aimed to a better understanding of the onset, maintenance, and variability
of the SCSSM (for a overview, see Ref. 7).
In the past decades, efforts have been made to explore various aspects of
the SCSSM and led to significant progress. However, some open issues still
remain. For example, what is the driving mechanism of the SCSSM onset?
While many studies focused on the large-scale environmental condition
favorable for the SCSSM onset, the role of the local air-sea interaction
and the three-dimensional water vapor profile has rarely been addressed,
partially due to shortage of reliable observations in an appropriate time-
space resolution. Using ship observations, Chu and Chang
9
identified
the development of a warm-core eddy in the central SCS immediately
before onset of the SCSSM attributing to the radiative warming and the
downwelling driven by the surface anti-cyclonic flows, which helps lowering
atmospheric surface pressure. However, their data analysis is limited to 1966
only. The air-sea heat exchanges during different stages of the SCSSM onset
have also been explored by using the station observations in the SCS.
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Though considerable air-sea flux exchanges were identified during the
monsoon onset, the direction of the heat transportation varies from one
study to another, partially because of the difference of the observation
location and time.
12
So far there is no conclusive result on how the air-sea
interaction and water vapor profile may affect the
thermodynamic
condition which leads to the onset and northward propagation of the
SCSSM.
The recently available satellite observations of the sea surface
temperature (SST), precipitation, humidity, air temperature, and surface
wind provide accurate and high-resolution coverage in the ocean regions
where the conventional observation is rare. This provides an unprecedented
opportunity to investigate the complicated physical processes relevant
to the SCSSM onset. Among satellite sensors, the Atmospheric Infrared
Sounder (AIRS) is a facility instrument aboard the NASA's Earth
Observing System (EOS) polar-orbiting platform and is the most advanced
moisture and air temperature sounding system. It constitutes an innovative
atmospheric sounding group of visible, infrared, and microwave sensors
in situ
