Satellite-Monitored Snow Cover in the Climate System - Satellite-based Applications on Climate Change - page 181

underlying soil temperature and local river runoff. Groisman et al. ( 1994 ) found a
retreat of North American springtime snow associated with strong warming. The
extent of boreal snow during spring was significant lower during the 1990s than at
any time in the previous century (IPCC 2007 ). Barnett et al. ( 2005 ) concluded
future water supplies may be hindered in a warmer climate with less snowfall and
earlier melting. In the background of global warming, how the snow cover will
change is a challenging scientific question.
12.4 Numerical Simulations
Atmospheric general circulation models (AGCMs) coupled with various Land
Surface Models LSMs are popular tools for examining the snow-atmosphere
interaction studies, largely because the numerical model can be easy manipulated
via deliberate changes to physics processes or parameterizations in controlled
experiments. Numerical simulations also provide a method to explore the climate
system with some extreme snow situations that could not happen in nature.
Various AGCM modeling studies (Bamzai and Marx 2000 ; Barnett et al. 1988 ;
Dash et al. 2005 ; Dong and Valdes 1998 ; Vernekar et al. 1995 ) have been
conducted to support the snow-monsoon inverse relationship first suggested by
Blanford ( 1884 ). These studies indicate the AGCMs are able to reproduce an
inverse snow-monsoon relationship and snow-cover and snow-mass impact on
climate on a seasonal time scale. Ferranti and Molteni ( 1999 ) investigated the
effect of springtime snow conditions over Eurasia on the monsoon circulation by
using ensemble simulations. The results suggested Eurasian snow depth is probabi-
listically predictable and that it does influence the seasonal-mean monsoon inde-
pendently of the ENSO phase. As a result, proper observations and simulations of
the Eurasian snowfield can provide an additional and independent contribution to
monsoon prediction.
Several prior studies have attempted to quantify the snow role in the cold region
climate (Gong et al. 2004b ; Vavrus 2007 ; Walsh et al. 1985 ; Watanabe and Nitta
1998 ). However, those earlier works have been limited in spatial and temporal
extent. Prescribed excessive or deficient snow over a specific region, such as
Eurasia and Siberia, has been investigated based on the observed fluctuation over
monthly to seasonal time scales.
Due to the limitation and imperfections of snow schemes in land surface models,
some simulation studies get conflicting results, even with the same model. For
example, Zhang and Tao ( 2001 ) created a conceptual model to explain the possible
mechanism on the impact of the inphase change of snow cover over the TP with the
EASM and summer rainfall over Yangtze River Basin. They further verified their
conclusion by model simulations with excessive/deficient snow depth in the winter.
However, with the same IAP-9L AGCM model and the updated snow data, Li and
Chen ( 2006 ) obtained an opposite result.