Monday, March 10, 2014

Snow cyberseminars at CUASHI

In this early 2014 CUASHI sponsored three cyberseminars on snow modelling.  Here they are below.

Presenter: Dr. Jeff Dozier - University of California, Santa Barbara, Bren School of Environmental Science & Management
in conjunction with Dr. Anne Nolin - Oregon State University, Department of Geosciences

Title: Assessing Snow and Snowmelt Runoff in Remote Mountain Ranges
Our objective is to estimate seasonal snow volumes, relative to historical trends and extremes, in snow-dominated mountains that have austere infrastructure, sparse gauging, challenges of accessibility, and emerging or enduring insecurity related to water resources. The world's mountains accumulate substantial snow and, in some areas, produce the bulk of the runoff. In ranges like Afghanistan's Hindu Kush, availability of water resources affects US policy, military and humanitarian operations, and national security. The rugged terrain makes surface measurements difficult and also affects the analysis of remotely sensed data. To judge feasibility, we consider two regions, a validation case and a case representing inaccessible mountains. For the validation case, we use the Sierra Nevada of California, a mountain range of extensive historical study, emerging scientific innovation, and conflicting priorities in managing water for agriculture, urban areas, hydropower, recreation, habitat, and flood control. For the austere regional focus, we use the Hindu Kush, where some of the most persistent drought in the world causes food insecurity and combines with political instability, and occasional flooding. Our approach uses a mix of satellite data and spare modeling to present information essential for planning and decision making, ranging from optimization of proposed infrastructure projects to assessment of water resources stored as snow for seasonal forecasts. We combine optical imagery (MODIS on Terra/Aqua), passive microwave data (SSM/I and AMSR-E), retrospective reconstruction with energy balance calculations, and a snowmelt model to establish the retrospective context. With the passive microwave data we bracket the historical range in snow cover volume.

Presenter: Dr. Michael Durand, Assistant Professor, Ohio State University

Title: Microwaves and snow grains: Monitoring the changing mountain snowpack
Abstract:  Snow is a vital water resource for over a sixth of the world's population. There are concerns about the impact of changing timing of snowmelt runoff in a warming climate. Microwave radiation has been measured from space and exploited to estimate snow water equivalent (SWE) for decades. Current algorithms struggle to successfully estimate SWE in mountainous areas. Use of microwave data for snowpack characterization for hydrologic studies has been stymied by the complex role of snow microstructure and layering on snow microwave emission, the large spatial scale of the passive microwave (PM) measurements compared with dominant montane landscape spatial scales, and vegetation attenuation of PM measurements.  Here, we summarize recent advances in these three areas, and assess the prospect of large-scale SWE estimation in mountainous areas.

Presenter: Dr. David Robinson, Rutgers University, Department of Geography

Title: Large-scale Snow Extent over Northern Hemisphere Lands
Annual snow cover extent (SCE) over Northern Hemisphere (NH) lands averages 25.8 million square kilometers.  It ranges from an average of 47.1 million sq. km. in January to 3.0 million sq. km. (mostly atop the Greenland Ice Sheet) in August. SCE is calculated at the Rutgers Global Snow Lab from daily SCE maps produced by meteorologists at the National Ice Center, who rely primarily on visible satellite imagery to construct the maps.

Annual SCE over NH lands has averaged lower since the late 1980s than earlier in the satellite era that began in the late 1960s.  This is most evident from late winter through spring, and in the past decade has been exceedingly pronounced at high latitudes in May and June. The most recent four Mays have had four of the five lowest NH SCEs on record, with Eurasian (Eur) SCE at a record low in 2013. North American (NA) SCE achieved a record minimum in May 2010, but of late has not been as consistently low as over Eur. The past six Junes have seen record minimum SCEs over the NH and Eur, with five of these six Junes the lowest over NA.  The recent early timing of arctic snowmelt appears to be occurring at an equivalent if not greater pace than the loss of summer Arctic sea ice extent.

While when projecting snow melt discharge it is much preferable to know the water equivalent of a snowpack (SWE) rather than its extent, the response of streamflow to seasonal SCE changes has been found to be significant within large basins in Siberia and the North American arctic.  Along with an overview of continental SCE kinematic, this hydrological relationship will be examined in this presentation, along with results looking at satellite microwave derived SWE and discharge, which also show promising results on a large scale. 

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