Radar scatterometry is used extensively in the polar regions as it is highly sensitive to the presence of liquid water at all weather and light conditions. Until now, the technique had not been used in lower latitude regions such as the Himalayas, which, due to the amount of snow and ice, are sometimes referred to as the "third pole".

Prajjwal Panday and colleagues from Clark University found, perhaps unsurprisingly, that the eastern portion of the Himalayas, which is closest to the equator and therefore sees more Sun, has on average an earlier melt onset and a later freeze-up than the central and western Himalayan and the Karakoram regions; it has a melt season that is approximately five weeks longer.

"But we also found that snowmelt dynamics exhibit regional and interannual variability with clear connections to terrain features, in particular elevation and aspect," Panday told environmentalresearchweb. "Our results corroborate the variable responses of glaciers from the east to the northwest, with more melting and faster glacial retreat in the eastern Himalaya, but a lack of any rapid disintegration of glaciers in the northwest Himalaya and Karakoram. As the eastern Himalayas have a longer melt season on average, enhanced melting may amplify the already observed glacial retreat."

The results from the research are summarized in spatial maps of the timing of melt, freeze-up and melt-season duration in the Hindu Kush–Himalaya region. Panday believes that the study provides an overall perspective of regional differences in melt onset, freeze-up and melt duration, which have important implications for glaciological and hydrological processes across the Hindu Kush–Himalaya region.

"Unfortunately trend analysis over a longer time period was not possible because no more data were collected after 2009 because of an antenna-rotation failure on the QuikSCAT satellite," said Panday. "While radar scatterometry is a relatively new technique, our project has shown that it is a valuable tool for this kind of work."

However, Panday is keen to stress that the work would not have been possible without ground-based measurements to validate the satellite data. "The terrain and remoteness of the region make it extremely difficult to take field measurements, so there is not a large amount of data available," said Panday. "But considering the sheer number of people who depend on this region for their water, there is an urgent need for more research in the area."

The researchers published their work in Environmental Research Letters (ERL).