[Tiimes-extended] REMINDER - Seminar at 1:00at FL2-1022

[Teresa Rivas]

* *

 

*Changes to North American Snowpacks from 1979-2004 Based on the Snow 
Water Equivalent Data of SMMR & SSM/I Passive Microwave and Related 
Climatic Factors*

 

/Thian Yew Gan^1,3 , Balaji Rajagopalan ^2 , Roger Barry ^1 , Adam 
Gobena^3 /

/^1 National Snow and Ice Data Center (NSIDC), University of Colorado at 
Boulder, Colorado
^2 Department of Civil & Architectural Engineering, University of 
Colorado at Boulder, Colorado/

/^3 On leave from Department of Civil & Environmental Engineering, 
University of Alberta, Canada/

* *

Changes to the North American (NA) Snowpacks from 1979-2004 based on the 
Snow Water Equivalent (SWE) values retrieved from the SMMR and SSM/I 
Passive Microwave data were analyzed using the non-parametric Kendall's 
test.  About 30% of detected decreasing trends in SWE for 1979-2004 are 
statistically significant at ?/2 = 0.05, which is about 3 or more times 
more frequent than detected increasing trends in SWE.  Significant 
decreasing trends in SWE are more extensive in Canada than in the U.S., 
where such decreasing trends are mainly found along the American 
Rockies.  The overall mean trend magnitudes are about -0.4 to -0.5 
mm/year which means an overall reduction of snow depth of about 10 to 13 
cm (assuming a snowpack density of 0.1) which can have significant 
impact to regions relying on spring snowmelt for water supply.  The PC1 
of NA's SWE are found to be significantly correlated to the Pacific 
Decadal Oscillation (PDO) index, marginally correlated to the Pacific 
North American (PNA) pattern, but not much related to El Nino Southern 
Oscillation (ENSO).  To assess the possible impact of climatic change to 
the snowpack of NA, the SWE-air temperature relationships are also 
analyzed.  Trend analysis of both the gridded, 2-m air temperature data 
of the North American Regional Reanalysis (NARR) and that of the 
University of Delaware showed little agreement between areas of detected 
increasing temperature trends and decreasing SWE trends based on passive 
microwave data, but extensive areas of negative correlations between SWE 
and temperature exist both across the U.S. and Canada except in January, 
and the distribution of these areas of negative correlation closely 
follow the areas of the decreasing trends detected from the SWE data.  
More significant decreasing precipitation trends are detected from 
University of Delaware than NARR data but again there are limited 
agreements between areas of detected decreasing precipitation trends and 
decreasing SWE trends.

 

Thursday, 14 August 2008                                      Foothills Lab

1:00 p.m. (refreshments at 12:45 p.m.)                Room 1022

 

/ /

/For more information, contact Teresa Rivas, ext 1437 or rivas at ucar.edu/

-- 
______________________
Teresa Rivas
Administrator TIIMES
303-497-1437

http://www.tiimes.ucar.edu

NCAR
The Institute for Integrative & Multidisciplinary Earth Studies (TIIMES)
P.O. Box 3000
FL1-2024
Boulder, CO 80307-3000

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