Aircraft Observations in Siberia

The Frontier Observational Research System for Global Change (FORSGC) conducts research in close cooperation with the FRSGC in order to clarify the processes of global change. In this edition, Dr. Hironori Yabuki talks about the airplane observation in Siberia.

Dr. Hironori Yabuki (Hydrological Cycle Observational Research Program)

Clarifying the hydrological cycles of Siberia on the Eurasian continent, where the snow and ice is thought to be sensitive to minute climate variations, is extremely important for comprehending the variations in Asian monsoons and global climate systems. An understanding of the hydrological process occurring in the Lena River, the mouth of which is located in the vicinity of the Arctic Ocean, is especially important, not only for elucidating the climate systems in Asian Monsoon regions, but also for those in the Arctic and for the whole globe.

Research conducted in that area over the past several years has clarified 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. In the year 2000, based on the knowledge of these basic processes and regional characteristics, the ground observations were intensified (photograph 1), and aircraft was used to establish three-dimensional observations.

Photograph 1: Ground observation point monitoring equipment

A) Forest canopy observation tower

B) Forest floor radiation observation station

C) Alas grasslands observation station

D) Alas lake observation station

The observation area is the north ern side of Yakutsk. The area includes Spasskaya Pad, where the Taiga forests are located, and Tungulu, which lies in the Alas zone*. The period for intensified observation was scheduled from April to June 2000. This time frame includes periods of snowfall, snowmelt, before leaves open, and after foliation. During this period, nine aircraft observations were conducted between 24 April and 19 June.

The aircraft observations were conducted using a grid observation on the left and right banks of the Lena River at low altitude (100 m and 150 m) so that clear spatial distributions of the flux**es could be obtained over the right bank of the Lena River which is mostly covered by the Alas grasslands, and the left bank of the Lena River where mature larch forests and red pine forests grow. To reveal the structure of the atmospheric boundary layer and the local cycles occurring due to the presence of the Lena River, the turbulent fluxes were observed by taking measurements at altitudes of 100m, 150m, 300m, 800m, and 1500m using a broad flight path covering the left and right banks of the Lena River.

On the observation days, the lowest flight altitude was just 100 m, and the size of the aircraft as viewed from the ground (photograph 2) surprised the local residents as well as the Japanese and Russian researchers. This incidence eventually became an opportunity for the local residents to show interest in the observation study, and we were able to receive their total cooperation.

Photograph 2: An aircraft flying at an altitude of 100 m above the Alas grasslands observation station on the right bank of the Lena River.

The aircraft observations were conducted only in the year 2000, but the ground observations still continue even now, and in the future, we intend to clarify the temporal and spatial characteristics of heat and water exchanges on a basin scale using this combined analysis.

*Alas zone: Refers to the area of land in the Taiga forest where a long period of heat erosion has caused the forest to disappear and be taken over by grasslands. The forms a hole that has been eaten out of the middle of the Taiga forest.

**Flux: In this context, refers to the water and heat budget (amount of water and heat being transferred) at the Earth's surface.

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