Geoscience Reference
In-Depth Information
3. Results and Discussion
3.1
. Observed monthly rainfall during rainy season
The ENSO during 1997-2000 were considered. During 1997-1998 El Nino
started in March 1997 when the highest sea surface temperature occurred
in September 1997, and the El Nino event ended in June 1998. Later,
La Nina occurred in June 1998 and persisted through 2000.
4
The abnormal
rainfall during the rainy season during 1997-2000 was calculated from the
difference in the monthly rainfall with long-term mean as shown in Fig. 2.
It can be seen that the abnormal rainfall during ENSO year 1997-2000 is
strong during the early and end of the rainy season. During this period,
the monthly rainfall during El Nino (1997) shows negative value (below
normal), while positive value (above normal) was found in La Nina (1999-
2000) in most of the regions in Thailand. The decrease or increase in rainfall
during this period was caused by the movement of ITCZ, and is strong in
monsoon. During El Nino (1997), it was found that the ITCZ moves rapidly
within a short time in Thailand and becomes weak in monsoon, whereas
in La Nina year (1999-2000) the ITCZ moves early to Thailand during the
onset of early monsoon and reaches the peak in monsoon.
10
−
12
250.00
200.00
150.00
100.00
50.00
0.00
-50.00
-100.00
-150.00
-200.00
-250.00
Early
Middle
End
Rainy season
North
Northern
Central
East
South (east coast)
South(west coast)
Fig. 2. The rainfall anomalies (mm) during rainy season 1997-2000.
3.2
.Modelsimulation
The rainfall in each rain gauge stations was divided in each region of
Thailand by using area-average. The choice of gauges was by selected
