摘要：We analyze snow cover extent (SCE) trends in the National Oceanic and Atmospheric
Administration's (NOAA) northern hemisphere weekly satellite SCE data using the
Mann–Kendall trend test and find that North American and Eurasian snow cover in the
pan-Arctic have declined significantly in spring and summer over the period of satellite
record beginning in the early 1970s. These trends are reproduced, both in trend direction
and statistical significance, in reconstructions using the variable infiltration capacity (VIC)
hydrological model. We find that spring and summer surface radiative and turbulent fluxes
generated in VIC have strong correlations with satellite observations of SCE. We identify
the role of surface energy fluxes and determine which is most responsible for the observed
spring and summer SCE recession. We find that positive trends in surface net
radiation (SNR) accompany most of the SCE trends, whereas modeled latent heat
(LH) and sensible heat (SH) trends associated with warming on SCE mostly
cancel each other, except for North America in spring, and to a lesser extent for
Eurasia in summer. In spring over North America and summer in Eurasia, the SH
contribution to the observed snow cover trends is substantial. The results indicate that
ΔSNR is the primary
energy source and ΔSH plays a secondary role in changes of SCE. Compared with
ΔSNR and
ΔSH,
ΔLH has a minor influence on pan-Arctic snow cover changes.
