Simulated impacts of historical land cover changes on global climate in northern winter |
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Authors: | T N Chase R A Pielke Sr T G F Kittel R R Nemani S W Running |
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Institution: | (1) Department of Atmospheric Science Colorado State University, Ft. Collins, CO 80523, USA E-mail: chase@deathstar.atmos.colostate.edu, US;(2) Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, CO 80307, USA, US;(3) School of Forestry, University of Montana, Missoula, MT 59812, USA, US |
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Abstract: | This ten-year general circulation model experiment compared a simulation where land surface boundary conditions were represented
by observed, present day land cover to a simulation where the surface was represented by natural, potential land cover conditions.
As a result of these estimated changes in historical land cover, significant temperature and hydrology changes affected tropical
land surfaces, where some of the largest historical disruptions in total vegetation biomass have occurred. Also of considerable
interest because of their broad scope and magnitude were changes in high-latitude Northern Hemisphere winter climate which
resulted from changes in tropical convection, upper-level tropical outflow, and the generation of low-frequency tropical waves
which propagated to the extratropics. These effects combined to move the Northern Hemisphere zonally averaged westerly jet
to higher latitudes, broaden it, and reduce its maximum intensity. Low-level easterlies were also reduced over much of the
tropical Pacific basin while positive anomalies in convective precipitation occurred in the central Pacific. Globally averaged
changes were small. Comparisons of recent, observed trends in tropical and Northern Hemisphere, mid-latitude climate with
these simulations suggests an interaction between the climatic effects of historical land cover changes and other modes of
climate variability.
Received: 8 September 1998 / Accepted: 31 July 1999 |
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