HR: 0800h
AN: C31A-0308    [Abstracts]
TI: Air Temperature Lapse Rate Dynamics in a Snow-Dominated Mountainous Watershed
AU: * Hubbart, J A
EM: hubb8662@uidaho.edu
AF: Jason A. Hubbart, Department of Forest Resources, University of Idaho, College of Natural Resources , Moscow, ID 83843-1133 United States
AU: Link, T E
EM: tlink@uidaho.edu
AF: Jason A. Hubbart, Department of Forest Resources, University of Idaho, College of Natural Resources , Moscow, ID 83843-1133 United States
AB: Spatial variation in snowpack processes owing to topographic effects is complicated by air temperature inversions that may be an important factor in determining the timing and rate of snowmelt. This process is of great interest in mountainous regions where snowmelt is one of the largest surface water inputs controlling runoff. Localized temperature inversions, coupled with topographic shading of solar radiation and windspeed reductions can produce ablation patterns that proceed from ridgetops to valley bottoms in some catchments. To develop a better understanding of this process, 38 temperature data loggers were installed in transect spanning three second-order catchments in the Mica Creek Experimental Watershed (MCEW) in northern Idaho. Results indicate that strong temperature inversions occur from low to upper mid slopes during daylight hours. Between the months of November 2003 and April 2004, inversions typically spanned the lower 140 vertical meters. These inversions resulted in lapse rates of 54.6, 12.8, and 11.4 §C/km at 12:00, 15:00, and 18:00hrs respectively on sunny days, and lapse rates of 19.9, 6.4, and 2.1 §C/km at 12:00, 15:00, and 18:00hrs respectively on cloudy days. At approximately 140 m the temperature pattern began to revert back to normal lapse rates. At this scale (i.e. less than 1km), the observed lapse rates could lead to highly variable impacts on snowmelt due to the dramatic deviation from average environmental lapse rates of approximately -5 to -6 §C/km. This work has shown that the classic assumption of normal lapse prevailing in mountainous catchments can be incorrect. The violation of the standard assumption that air temperature decreases with altitude holds important implications for development of distributed climate surfaces to drive distributed snowmelt models.
DE: 3322 Land/atmosphere interactions
DE: 1854 Precipitation (3354)
DE: 1860 Runoff and streamflow
DE: 1863 Snow and ice (1827)
DE: 1878 Water/energy interactions
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting