Geoscience Reference
In-Depth Information
As regards the effects of the QTP thermal role and its ensuing
moist process upon monsoon features, numerous Chinese researchers have
demonstrated
7
,
8
that the variation in nonadiabatic heating in the transition
early in summer gives rise to the change in land-sea thermal contrast,
thus providing a favorable background for Asian summer monsoon onset,
which has significant impacts on the outbreak.
9
As shown by Jiang and
Luo,
10
when the East Asian monsoon begins, the nonadiabatic heating
is responsible for tropospheric explosive warming over the Southeast
QTP, leading to change in temperature gradient southward of the east
QTP, consequently resulting in the adjustment of wind field for the
onset of the east Asian monsoon. Jian
11
indicated that the May-June
conspicuous warming due to nonadiabatic heating in the mid-higher
troposphere over the east QTP is of much importance to the northward
march and maintenance of the summer monsoon. Differences in space/
time distribution of QTP summer rainfall also cause variations in the
spatial/temporal distribution of the heat sources over the QTP and
its neighborhood — the variations make atmospheric circulation change
accordingly, finally leading to the difference in the onset time of the
monsoon.
12
Although monsoon researchers, domestic and foreign, diverge
about how the QTP sensible heating affects the summer monsoon onset,
undoubtedly, the QTP heating represents one of the mechanisms of the
monsoon onset.
For lack of observations, how to obtain correct calculation is the
linchpin of studies. The 1961-2001 ECMWF (ERA hereafter) daily
reanalysis was employed to calculate the heat source features. The
atmospheric apparent heat source
Q
1
was found by the use of the “inverse
algorithm” developed by Yanai.
13
Q
1
comprised three terms: local term,
advection term, and vertical transport term.
2. Regional Mean Climate Condition Due to the QTP
Heat Sources
To gain insight into the tropospheric thermal regime 1961-2001
-
associated mean climate condition was analyzed. Over 1961-2001, within
the region of 3000 m, 41-yr monthly climate mean conditions of
Q
1
were
shown by full line with open circles (Fig. 1), indicating that in March-
September,
Q
1
0 as the heat source began intensification from March,
maximizing at 214 W/m
2
Q
1
>
in June, and decreasing thereafter; in October-
February,
Q
1
<
0 suggestive of a cold source, the strongest being in
