HR: 1340h
AN: A23B-0806    [Abstracts]
TI: Climate Response to Increased Greenness at High Latitudes in Climate Model ARPEGE-CLIMAT
AU: * Zhang, J
EM: jing@gi.alaska.edu
AF: Geophysical Institute, University of Alaska Fairbanks, 903 Koyukuk Dr., Fairbanks, AK 99775 United States
AU: * Zhang, J
EM: jing@gi.alaska.edu
AF: Arctic Region Supercomputing Center, P.O.Box 756020, Fairbanks, AK 99775 United States
AU: Walsh, J E
EM: jwalsh@iarc.uaf.edu
AF: International Arctic Research Center, 930 Koyukuk Dr., Fairbanks, AK 99775 United States
AB: Satellite-derived normalized difference vegetation index(NDVI) indicates that greenness at high latitudes has increased. This increase may result from climate warming in the polar and subpolar regions, the effects of which may include a lengthened growing season, increased CO2 concentration in the atmosphere, and enhanced nutrient availability in the warmed soils and thawed permafrost. However, the feedbacks of increased greenness on climate have not been well documented. In this study we employed the climate model ARPEGE-CLIMAT, a version of the ARPEGE model developed at Meteo-France modified by the Bergen climate model (BCM) group, to identify these impacts. We first conducted a 10-year model simulation of the present climate with a horizontal resolution of T63 (linear grid) and 31 vertical layers with boundary conditions taken from the NCAR/NCEP reanalysis, which served as our control run. A sensitivity simulation with the same integration time was then performed in which the vegetation coverage and leaf area index (LAI) were increased by 20% poleward of 60oN. Through these parallel model simulations we aim to evaluate the impacts of increased greenness on the climate at high latitudes. The comparison of these two simulations indicates that increased greenness results in a significantly increased local evaporation during summer from May to August, which changes local hydrological cycle and energy budgets. Throughout the entire year, the impacts of increased greenness on atmospheric circulation are complex. Sea level pressure (SLP) and surface air temperature show larger anomalies in winter than in summer over the polar and sub-polar regions. The anomalous atmospheric conditions in winter months from October to March are characterized by unfavorable effects on the establishment of winter circulation systems and favorable effects on the retreat of these systems in spring; surface air temperature anomalies are consistent with changes to the atmospheric circulation. Interplay of atmospheric dynamic and thermodynamic processes, triggered by the increased greenness, and impacts of land surface processes are apparently responsible for such atmospheric circulation anomalies.
DE: 3349 Polar meteorology
DE: 3309 Climatology (1620)
DE: 1600 GLOBAL CHANGE (New category)
DE: 1610 Atmosphere (0315, 0325)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting