**2. Climatology analyses of the satellite-based snow parameters over China**

### **2.1 Introduction**

48 Remote Sensing of Planet Earth

Fig. 1. This conceptual diagram illustrates the connectivity of the positive ice/snow albedo feedback, terrestrial snow and vegetation feedbacks and the negative cloud/radiation

and 1997, the results show that western China did not experience a continual decrease in snow cover during the great warming periods of the 1980s and 1990s. The positive trend of snow cover in western China snow cover is consistent with increasing snowfall, but is in contradiction to regional warming. Xu's result (2007) also show that the SCA of the entire *Tarim* basin in Xinjiang Province revealed a slowly increasing trend from 1958 to 2002, the SCA change in the cold season was positively correlated with the contemporary precipitation change. Wang (2008) reported an inconsistent tend with a reported Northern Hemisphere increasing trend based on limited in situ observations in Xinjiang Province which is a western province in China. While over the area located in the southern parts of the high land of *Tibet Plateau*, China, some investigators explore that annual snow cover has declined by –16% per decade between 1990 and 2001, which is explained due to the contribution of enhanced Indian black carbon (Menon et al., 2010) and the additional absorption of solar radiation by soot on snow cover area (Chand, 2009). Over *Tibetan Plateau* area, Pu's study (2007) indicated that a decreasing trend of snow cover fraction using snow data of 2000–2006 from the Moderate Resolution Imaging Spectroradiometer (MODIS) data is –0.34% per year. In their study, the meteorological station data (Xu, 2007) and the satellite sensor (Scanning Multichannel Microwave Radiometer, SMMR) observed snow depth (SD), NOAA snow cover area data and MODIS snow cover fraction products are used. When concerning the climate change impact on snow cover, the variability of snow cover area is negatively associated with to air

feedback. (Source: Chapin III, 2005)

The climatology features for a long time series of snow parameters over land could provide the signature of climate changes across the globe. According to the IPCC AR4 report, the snow extent is sharply decreasing over Northern Hemisphere from the prediction of the nine General Circulation Models since 2000. This part provides a climatology analysis of the SCA and SWE over China area and *Tibetan Plateau* from the satellite observation. The data set includes snow extent and snow water equivalence. Snow extent products are 24 km daily Northern Hemisphere snow and ice coverage from the NOAA/NESDIS Interactive Multisensor Snow and Ice Mapping System (IMS), Near-Real-Time SSM/I-SSMIS EASE-Grid Daily Global Ice Concentration (NISE) and Snow Extent and the Moderate-resolution Imaging Spectroradiometer (MODIS, TERRA/AQUA) snow cover fraction (SCF) products from 1999 to now, and the SWE products include Global Monthly EASE-Grid Snow Water Equivalent Climatology from 1978 to 2007, and the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) from 2002 to now. The SCF (MODIS) and SWE (AMSR-E) are employed to analyse the ten years' time series over *Tibetan Plateau* (the area is defined by the area where the atmosphere pressure is less than 700 hPa).
