Changes third in Tb at 19 and 37 GHz have been used as a metric for determining melt onset (Zwally and Fiegles, 1994; Ridley, 1993, and Mote selleck chemicals llc and Anderson, 1995). Steffen et al., (1993) identified wet snow regions using AVHRR (Advanced Very High Resolution Inhibitors,Modulators,Libraries Radiometer), SMMR, SSM/I and in-situ data, based on the relationships between in-situ measurements and horizontally polarized 19 and 37 GHz observation. Specifically, the cross-polarization gradient ratio (XPGR) (Abdalati and Steffen, 1995) approach was used to assess melt zones. XPGR indicates melt when the snow surface contains greater than 1% liquid water by volume. To study seasonal and inter-annual variations in snow melt extent of the ice sheet, Abdalati and Steffen (1997) established melt thresholds in the XPGR by comparing passive microwave satellite data to field observations.

Ashcraft and Long (2005) studied the differentiation between melt and freeze stages of the melt cycle using the SSM/I channel ratios. In 2006, these authors assessed melt detection performance from SSM/I, Inhibitors,Modulators,Libraries SeaWinds on QuikSCAT (QSCAT), and the European Remote Sensing (ERS) Advanced Microwave Instrument (AMI) in scatterometer mode, and concluded that melt estimates Inhibitors,Modulators,Libraries from different sensors were highly correlated. The difference between ascending and descending brightness temperatures Inhibitors,Modulators,Libraries (DAV) (Ramage and Isacks, 2002) measured either at 19.35- or 37- GHz by SSM/I was applied to map Inhibitors,Modulators,Libraries melt extent in Greenland, and the results compared with those obtained from QSCAT (Nghiem et al.

, 2001; Tedesco, 2007).

Although active and passive microwave Inhibitors,Modulators,Libraries systems have performed well in Inhibitors,Modulators,Libraries monitoring melt conditions over the GIS, they are limited in the amount of detail Entinostat Inhibitors,Modulators,Libraries that can be either spatially or temporally resolved. Passive systems have relatively coarse spatial resolution and generally results from maintaining high radiometric resolution, while active systems demonstrate limited or lower temporal resolution (Campbell, 2007). Active systems such as SAR in high-resolution observations of microwave radar backscatter have 16-day ground track repeat cycle, which is too infrequent to capture dynamic melt conditions.Other parts of the EM spectrum offer potential advantages for monitoring melt over the GIS, and may augment the shortcomings of microwave systems.

Data from optical satellites have been used to map surface dynamics related to the melt process over the GIS at higher spatial resolutions.

Brefeldin_A Hall et al. (1990) compared in-situ measurements with Landsat Thematic Mapper (TM)-derived reflectance on Greenland and concluded that Landsat TM was Site URL List 1|]# viable to obtain the physical reflectance of snow and ice. AVHRR visible and near-infrared radiances were used to derive surface albedo over the GIS and were validated by in-situ data (Stroeve et al., 1997).