Snow ablation process in the southern mountainous taiga of eastern Siberia, during an early spring

The southern mountain taiga region is the water source of the Lena and Bikal basins. Ma et al. (2000) showed that most of the water in these rivers flows from south-eastern Siberia, which has heavy rain, especially in the summer. From August 2000 to May 2002, we made long-term observations of the water, energy, and carbon cycles on a catchment scale. This paper presents results of an intensive observation on snowmelt, sublimation and energy balance during a spring in 2002. The Mogot experimental watershed is located in the southern mountain region of eastern Siberia (55.5°N, 124.7°E) approximately 60 km north of Tynda, in the Amur region, Russia. The observation site is the catchment of the Nelka River. The basin is about 12 km long and 2.5 km wide, with a total area of approximately 30.8 km2; the slopes are exposed to the northeast and southwest. In this basin, altitudes range from approximately 580 to 1150 m. The land surface is predominantly covered by larch forest, but birch forest partly covers the ridge area and higher elevations are covered by pine forest. Three sites with typical surface conditions were selected to observe meteorological elements. Two sites, LF (Larch forest, 610m) and OP (grassland, 608m) were at the bottom of the valley, and another site ES (Larch forest, 635m) was located in an east slope. Snowmelt begun from 4 April 2002 and snow disappearance date was 7 May 2002. There was large difference of air temperature and relative humidity between Site OP or LF and ES in March 2002, but difference of air temperature and relative humidity between Site OP and LF was not significant. The difference of altitude between OP or LF and ES was approximately 30 m. Thus, this demonstrated that strong inversion layer existed above the snow surface. As season has gone on, then inversion layer was getting weak. Monthly mean evaporation was 0.26 mm/day in March. We also observed evaporation pan observation. The amount of evaporation was 0.24 mm/day so both observational values for evaporation from snowpack were similar. Furthermore, evaporation of site LF was greater than that of site ES. The most important energy to evaporation was soil heat flux during an early spring. Soil heat flux of site LF also was greater than that of site ES. Thus, different soil heat flux made the differences in evaporation. During early spring, strong inversion layer occurred at the atmospheric surface layer above the snow surface. There was good positive correlation between soil heat flux and strength of atmospheric inversion. The strength of atmospheric inversion increased the soil surface flux into a snowpack and we think that soil heat flux contributed the latent heat flux during March because the most of net radiation was negative and sensible heat flux was not significant. Therefore, strong atmospheric inversion caused the energy for latent heat flux and spatial variation of evaporation during early spring.