Snow disappearance in Eastern Siberia and its relationship to atmospheric influences

Abstract

Abstract:In the present study, we examine the climatological features and interannual variations in snow disappearance within the Lena River Basin, Eastern Siberia, during a recent 15-year period (1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000), and the relationship of snow disappearance to atmospheric conditions. According to the climatology of the day of the year on which snow disappears, the boundary of snow disappearance within the Lena River Basin migrates rapidly northward from mid-April until early June, with minimum interannual variation occurring in the middle part of the basin. In addition, the preceding snow disappearance is apparent in the central Lena River Basin. Melting of snow within the Lena River Basin commonly occurs within 30 days of complete snow disappearance under certain atmospheric conditions: daily mean air temperature in excess of −10°C, greater than 2 hPa of water vapor pressure, and, hence, more than 170 W m −2 of downward longwave radiation under clear sky conditions. Composite analysis using a reanalysis dataset demonstrates that the increase in air temperature and water vapor that accompanies snow melting is due to wet (and warm) air advection in conjunction with enhanced water vapor convergence over the central Lena River Basin during the 30-day period prior to snow disappearance.

Snowmelt and Atmospheric Heating Processes over Eastern Mongolia

“…Time series analysis showed substantial snowmelt events at BU under certain atmospheric conditions-air temperature exceeding −10°C and increased water vapor pressure in excess of 1.9 hPa-and consequently increased downward longwave radiation of more than 194 W m −2 under clear-sky conditions. Interestingly, these critical values agree well with the corresponding values (−10°C, 2 hPa, and 170 W m −2 , respectively) obtained for eastern Siberia (Iijima et al 2007), although the yearly-maximum snow depth is approximately 40 cm (more than the few centimeters in eastern ; red denotes heating and blue cooling) on the previous days (a, b) and the days highlighted (c, d) composited for 8 days having a temperature increase more than 7°C from the previous days at Bayan Unjuul. The domain for the atmospheric heat budget is denoted by the thick lines.…”

“…Iijima et al (2007) found that the increase in air temperature and water vapor that accompanies snow melting over eastern Siberia is due to warm and wet air advection in conjunction with enhanced water vapor convergence. On the other hand, Ueda et al (2003) identified the horizontal warm advection as a primary factor of the snowmelt on the East European Plain and the adiabatic heating of descending air as a secondary factor.…”

“…Since then, considerable evidence of such correlation has been accumulated from analyses of satellite-observed snow data (e.g., Hahn and Shukla 1976) and ground-based snow data (e.g., Shinoda 2001;Shinoda et al 2001;Ueda et al 2003) and numerical simulations (e.g., Barnett et al 1989). On the other hand, there have been a few attempts to explore the physical processes that cause snowmelt on the continent (Ueda et al 2003;Iijima et al 2007). The above-mentioned studies dealt only with areas of deep snow exceeding a few tens of centimeters.…”

“…Thus, it is vital to identify the snowmelt timing and its physical processes on a daily basis. Iijima et al (2007) demonstrated that the increase in air temperature and water vapor that accompanies snow melting over eastern Siberia is due to warm and wet air advection in conjunction with enhanced water vapor convergence. Nemoto (2007) determined that snowmelt in Mongolia was due to a higher air temperature and concurrent increased downward longwave radiation on the basis of limited data recorded by only one station during 2005, but he did not reveal why the temperature increased.…”

The surface energy balance of a polygonal tundra site in northern Siberia – Part 1: Spring to fall

“…In both investigated years, the timing of the snow melt is almost identical. Iijima et al (2007) point out that snow cover disappearance in eastern Siberia is strongly related to the attenuation of the Siberian High with subsequent advection of warm and moist air masses from the west. According to the distinct contribution of sensible atmospheric heat flux to the snow melt, our measurements indicate the presence of warm air masses.…”