Abstracts for the 5th International GAME Conf.
3-5 October 2001
Aichi Trade Center
Nagoya Japan
The general climate at hill evergreen forest of tropical monsoon area in northern Thailand
Hideki TAKIZAWA (1), Chatchai TANTASIRIN (2), Nobuaki TANAKA (3), Izumi KOSAKA (1), Natsuko YOSHIFUJI (3), Katunori TANAKA (6), Masakazu SUZUKI (3), Nipon TANGTHAM (2)
(1) Nihon University
(2) Kasetsart University
(3) University of Tokyo
(6) Frontier Research System for Global Change
A field experimental study of energy and water balance in tropical monsoon forest that has clearly dry season has been carried out in the Kog-Ma experimental watershed of GAME/Tropics from February 1997. The Kog-Ma watershed covered by hill evergreen forest situated near Chiangmai and located at an altitude of about 1268-1420m. The purpose of this study is to clarify the general climate conditions such as micro-meteorological features over the canopy, energy and water balance, and canopy condition in hill evergreen forest.
The mean annual precipitation was 1562mm. and about 90% of those were occurred in the rainy season from May to October. The mean annual air temperature is 20.1. The seasonal variation of air temperature was not so big. In rainy season the water vapor pressure is high, 20hPa or more, and contrary the value of the dry season is half of the rainy season. The mean monthly wind speed is almost 2m/s. The wind speed between February and April is comparatively strong, and in November is lowest. This seasonal change was coursed by the variation of wind speed in nighttime. The wind in daytime had clear seasonality. From September to December was an east wind, from May to August was a south wind and from January to April was east and south wind. On the other hand, the wind direction in nighttime is west every season.
The mean annual short wave radiation was 5.6GJ¥m-2¥yr-1. The mean monthly albedo was between from 1.1 to 1.6 and the average was 1.3. The mean annual net radiation was 3.26GJ¥m-2¥yr-1. The high season of the net radiation is from March to May. Because it is a mid rainy season in June when the solar angle at noon is the highest. In energy balance, the latent heat was about 85% of the annual net radiation.
The change of LAI was from 3.5 to 5. The seasonal variation of LAI was not so big. LAI is lowest in end of dry season.
The discharge at the dry season was 1mm/day or more, so this site had big storage. Therefore, in hill evergreen forest LAI does not decrease remarkably at the end of dry season, and the transpiration reduction does not occur clearly.
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