Abstracts for the 5th International GAME Conf.
3-5 October 2001
Aichi Trade Center
Nagoya Japan
Water and energy flux observation over an alas lake in Central Yakutia, Eastern Siberia
Yoshiyuki Ishii (1), Hironori Yabuki (2), Nakako Kobayashi (3), Hiroki Tanaka (4), Hisanori Tanaka (5), Roman V. Desyatkin (6)
(1) Institute of Low Temperature Science, Hokkaido University
(2) Frontier Observational Research System for Global Change
(3) Graduate School of Environmetal Studies, Nagoya University
(4) Graduate School of Agriculture, Kyoto University
(5) Terrestrial Environment Research Center, University of Tsukuba
(6) Institute for Biological Problems of Cryolithozone, SB, RAS
Alas is a concave landform that is formed after the forest has been cleared in an area where the permafrost has high ice content. It is a characteristic land feature in central Yakutia, especially on the right bank of the Lena River. Water and energy flux observation were made over an alas lake during the summer of 2000. The objectives of this study are to clarify the difference in the surface energy balance over the lake/grassland/forest, and to learn how the water balance components affect the seasonal and inter-annual variation in alas water levels. A 1.5 m x 1.5 m platform was constructed on the water surface at the center of the lake. Net radiation, wind direction, wind speed, air temperature and relative humidity were measured at the height of 2 m above the water surface. Precipitation, water temperatures at the lake surface and bottom, water level, specific electrical conductivity (S.E.C.) of the water were also measured. These observations were carried out from April 18 to September 10. In addition, topographical relieves of the alas were surveyed in July, and the lake area/depth survey were made once a month from May to October. Evaporation amount from the lake surface was calculated by using the Bowen ratio method and Penman method. The result of energy partitioning over the lake showed that latent heat flux over the lake was largest among those over the forest canopy and the grassland. Its maximum daily mean value was nearly 280 W/m2, occurred in the beginning of June. However, net radiation was almost same over the each land surface. Total evaporation amount from the lake during the observation period was calculated 451 mm. Water level of the lake decreased from 70 to 40 cm with an almost constant rate during the observation period, except for the short times of 4 remarkable rainfall events. Water volume of the lake in September reduced up to 38 % of it in May. Meanwhile, the S.E.C. of lake water increased from 60 to 150 mS/m during the same period. This means that the increase of S.E.C. is mainly due to the evaporative condensation of the solute in the lake water. At the time of 4 remarkable rainfall events, the ratio of the water level rise to the total precipitation ranged between 1.3 and 1.6 with an average of 1.5. It is difficult to define the drainage area of the alas lake clearly. However, the ratio of 1.5 means small contribution of the surface/subsurface inflow component to the lake water balance.
Submittal Information
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Institute of Low Temperature Science, Hokkaido University | |
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Kita 19, Nishi 8, Kita-ku, Sapporo 060-0819 | |
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ishiiy@pop.lowtem.hokudai.ac.jp | |