Main results obtained by Siberia Regional Project of GAME
Tetsuo Ohata (1), Yoshihiro Fukushima (2)
(1) ILTS, Hokkaido Univ/FORSGC
(2) Research Institute for Humanity and Nature
GAME selected one of their field experiment site in Siberia. Importance of this area was, first, that it is a northern region with widely covered snow cover/permafrost and possess typical surface such as taiga forest and tundra which occupies a large area on Eurasia Continent. Second is that there is abundant freshwater runoff to the Arctic Ocean which may strongly affect the ocean circulation. Thirdly, this region is one center of the recent intense warming and better understanding is needed on the response of the land surface and possible feedback to the climate system.
In order to progress the study, we set up the following objectives.
1) Clarify the physical processes of the land-surface/atmosphere interacting system.
2) Clarify the characteristics and variability of regional energy/water cycle.
3) Obtain the climate trend and land-surface change during the past 50 years and evaluate possible feedback processes.
4) Improve and develop models describing the energy/water exchange and atmosphere-land surface systems.
5) Collection and archive of regional ground based/satellite data.
6) Establishment of observational network for long-term variation study, and development of hardware.
The four main strategy for implementation was to select one main drainage for study, which was Lena River, eastern most drainage among the three large Arctic flowing rivers. Second was to establish three local observation sites for intensive study from the criteria of land surface condition and climate in the drainage (Tundra area facing Arctic Ocean, flat taiga with little precipitation, mountain taiga with much precipitation). Third was to hold an intensive study period for investigating the land surface / atmosphere interaction and spatial and temporal variability of water/energy fluxes in a regional scale (100km scale), which was implemented in year 2000. Involve researchers of various discipline which can contribute to the understanding of the water/energy cycle in this region.
The study period was 1996-2001, and tight cooperation between Japanese and Russian institution/scientist lead to a success.
The main results obtained are as follows.
(1) Tundra surface processes: Shallow permafrost seem to have rather strong effect on heat budget at the surface. Hydrological response (summer evaporation) of tundra surface is rather stable in comparison to heat supply to the atmosphere (sensible heat), but drainage runoff seem to be regulated by the winter inhomogenous accumulation of snow, which is determined by winter climate.
(2) Flat taiga surface processes: The seasonal progress of heat/water exchange differs between the type of the forest, such as most dominant larch and pine, at both the influence of snow cover is masked by the canopies . Grass surface in comparison with nearby forest show different seasonal progress of fluxes, little lower evaporation and very low sensible heat supply to the atmosphere, result of shallow permafrost. Inter-annual variation of evaporation seem to be small in the forest, although soil moisture show strong inter-annual variability, mainly due to the active function of the trees.
(3) Land/surface atmosphere interaction at flat taiga: According to the aircraft observation of heterogenous land surface at 100km scale including Lena River, distribution of low level heat/water fluxes (100m) show complex pattern influenced by characteristics of boundary layer and local circulation.
(4) Precipitation recycling: Stable Isotope analysis show the seasonal change in the character of precipitation recycling, weaker in the early summer and stronger in late summer.
(5) Hydrological models sensitivity tests: Hydrological models were developed applicable to the large drainage, and result showed that drainage is more sensitive to change in precipitation than to air temperature.
(6) Development of automated year-round observation system: Automated observation system made success in acquiring year-round meteorological and ground surface data at the three local observation sites
