A Novel Approach to Validate Satellite Snowfall Retrievals by Ground-Based Point Measurements

Hwayoung Jeoung,Guosheng Liu,Shangyong Shi

doi:10.3390/rs14030434

Abstract

A novel method has been proposed for validating satellite radar snowfall retrievals using surface station observations over the western United States mountainous region, where the mean snowfall rate at a station depends on its elevation. First, all station data within a 1° × 1° grid are used to develop a snowfall rate versus elevation relation. This relation is then used to compute snowfall rate in other locations within the 1° × 1° grid, as if surface observations were available everywhere in the grid. Grid mean snowfall rates are then derived, which should be more representative to the mean snowfall rate of the grid than using data at any one station or from a simple mean of all stations in the grid. Comparison of the so-derived grid mean snowfall rates with CloudSat retrievals shows that the CloudSat product underestimates snowfall by about 65% when averaged over all the 768 grids in the western United States mountainous regions. The bias does not seem to have clear dependency on elevation but strongly depends on snowfall rate. As an application of the method, we further estimated the snowfall to precipitation ratio using both ground and satellite measured data. It is found that the rates of increase with elevation of the snowfall to precipitation ratio are quite similar when calculating from ground and satellite data, being about 25% per kilometer elevation up or approximately 4% per every degree Cuisses of temperature drop.

Highlights

Glacier and snowpack over high mountains are critical water resources to populations living in the lowland regions
The mean snowfall rates are generally larger at SNOTEL than at GHCND stations
As an application of the new validation dataset created in this study, we study the snowfall to precipitation ratio over the west U.S mountainous region and examine how well this ratio can be estimated from satellite radar observations

Summary

Introduction

Glacier and snowpack over high mountains are critical water resources to populations living in the lowland regions. In the western United States (U.S.), the bulk of surface water resources, as represented by the flow of the Colorado and Columbia River systems, is derived from melted winter snowpack [3]. Glacier is depleting over a global scale [4,5]. In the western U.S, it is observed that mountain snowpack is declining accompanied with rising surface temperature and early start of snow melting in the recent decades [6], which threatens the water resources in the western states [7]. The long-term variation of snowfall is an important indicator of climate change in both regional and global scales [8,9] and a key component of the hydrological cycle in the mid- and high latitudes [10,11,12,13]

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Conclusion