TOPIC FRONTIER Newsletter No.10 Mar.2000 

Frontier Observational Research System for Global Change

Here, we Like to introduce the activities of researchers of the FORSGC who work on global change together with the FRSGC. In the most recent issue, Dr. Tetsuo Ohhata, group leader of the Hydrological Cycle Observational Research Program, explains the intensified observation of the hydrological cycle in Siberia during the year 2000.

@  The Year 2000 intensified observation in Siberia

Tetsuo Ohhata
Hokkaido University,The Institute of Low Temperature Science, also a scientist at FORSGC

@The characteristics of heat and water exchanges on typical land in the Siberian Taiga (at a scale of several kilometers),and also of the accumulation and outflow of water on the land surface,have become clearer,due to research gathered over the past several years.

 In the year 2000 ,we will intensify ground observations,and introduce observation using airplanes,to clarify the three dimensional structure and seasonal variation of the atmosphere- land system.In the Taiga zone,along the Lena River,about 70 %of the land is covered with Taiga forests.Other areas are bare lands, grasslands,and watery lands,including areas such as lakes and rivers.In the forests, the most predominant kind of tree,among several other kinds,is larch.Further,the kind of tree,tree density,tree height,and tree age all depend on the respective forests in which they grow.These differences in land areas correspond to those of responses of water- energy,and to atmospheric forces, which cause the seasonal and daily variations.In the atmosphere- land system, its variety is reflected,and still a peculiar feature is maintained,responding to non-linear dynamics independently.

 Over time,this atmosphere- land system exhibits certain features.The snow cover, existing from winter to spring,and having high albedo,controls hydrological circulation rhythm and a certain amount of energy circulation.

 In addition,as the temperature increases and frozen soil thaws,deciduous trees have leaves,and they start to operate as part of a water- heat exchange process through the evaporation of water.

 The formation- extinction of the snow cover and the accretion of the leaves control water- energy circulation rhythm,but its extent of the control largely depends on land surfaces.

 Therefore,we expect to answer to the following questions:
(1 )How does the land area in this district respond to the atmospheric forcing? What kind of characteristics and variability does water- heat exchange have?
(2 )What kind of characteristics does the water/energy regime have in the atmosphere- land system during each time period of seasonal change?How is its time variation?What kind of influence do the snow cover and forests have over the state?
(3 )Can we apply the existing various models of one- dimension water- heat exchange,and of the atmospheric processes, to Siberia?

 In the year 2000 ,we will take the following four new measures.An outline of the observation is shown in Figure 1 .
(1 )The ground observations of water-energy exchange on a patch scale will be increased,totaling five sites of tower- mast and four spots of simple observation in a wide area;in the forests along the left and right coasts of the Lena river,and on the grass lands.
(2 )We will measure sensible heat and latent heat (heat transported by water vapor)in a wide area,and collect water vapor samples by aircraft observations.
(3 )We will intensify sonde observation at four sites near Yakutsk.
(4 )We will investigate the applicability and reproducibility of the one dimension water-heat exchange model and the atmosphere model,based on various data.

 The observation area is the northern side of Yakutsk,including Spasskaya Pad and Tynguru in the Alas zone.The term for intensified observation is scheduled from April to June 2000 ,and includes time periods of fallen snow and melting snow, before and after the forest leaves come out. During that period,we will make nine flight observations from April 10 through June 20 .

Figure 1 : Conceptual figure on 2000 intensified observation
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