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</span></span><!--[endif]--><b style=""><span
style="font-size: 20pt; color: red;">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<o:p></o:p></span></b></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="text-align: center;" align="center"><i
style=""><span style="font-size: 16pt; color: red;">Thian Yew Gan<sup>1,3</sup></span>,
Balaji Rajagopalan <sup>2</sup>, Roger Barry <sup>1</sup>, Adam Gobena<sup>3</sup><o:p></o:p></i></p>
<p class="MsoNormal" style="text-align: justify;"><i style=""><sup>1</sup>National
Snow and <st1:PlaceName w:st="on">Ice</st1:PlaceName>
<st1:PlaceName w:st="on">Data</st1:PlaceName> <st1:PlaceType w:st="on">Center</st1:PlaceType>
(NSIDC), <st1:PlaceType w:st="on">University</st1:PlaceType> of <st1:PlaceName
w:st="on">Colorado</st1:PlaceName> at <st1:City w:st="on">Boulder</st1:City>,
<st1:State w:st="on">Colorado</st1:State><br>
<sup>2</sup>Department of Civil & Architectural Engineering, <st1:PlaceType
w:st="on">University</st1:PlaceType> of <st1:PlaceName w:st="on">Colorado</st1:PlaceName>
at <st1:place w:st="on"><st1:City w:st="on">Boulder</st1:City>, <st1:State
w:st="on">Colorado</st1:State></st1:place><o:p></o:p></i></p>
<p class="MsoNormal" style="text-align: justify;"><i style=""><sup>3</sup>On
leave from Department of Civil & Environmental
Engineering, University of Alberta, <st1:place w:st="on"><st1:country-region
w:st="on">Canada</st1:country-region></st1:place><o:p></o:p></i></p>
<p class="MsoNormal" style="text-align: center;" align="center"><b
style=""><o:p> </o:p></b></p>
<p class="MsoNormal" style="text-align: justify;">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.<span style=""> </span>About
30% of detected decreasing trends in SWE for 1979-2004 are
statistically
significant at <span style="" lang="EL">α</span>/2 = 0.05,
which is about 3 or more times more frequent than detected increasing
trends in
SWE.<span style=""> </span>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. <span style=""> </span>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.<span style="">
</span>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).<span style="">
</span>To assess the possible impact of climatic change to the snowpack
of NA,
the SWE-air temperature relationships are also analyzed.<span style="">
</span>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.<span style=""> </span>More
significant decreasing precipitation
trends are detected from <st1:place w:st="on"><st1:PlaceType w:st="on">University</st1:PlaceType>
of <st1:PlaceName w:st="on">Delaware</st1:PlaceName></st1:place> than
NARR
data but again there are limited agreements between areas of detected
decreasing precipitation trends and decreasing SWE trends.</p>
<p class="MsoNormal" style="text-align: justify;"><o:p> </o:p></p>
<div
style="border-style: ridge none; border-color: windowtext -moz-use-text-color; border-width: 2.25pt medium; padding: 1pt 0in;">
<p class="MsoNormal" style="border: medium none ; padding: 0in;"><span
style="font-size: 16pt; font-family: "Century Gothic","sans-serif";">Thursday,
14 August 2008<span style=""> </span>Foothills
Lab <o:p></o:p></span></p>
<p class="MsoNormal" style="border: medium none ; padding: 0in;"><span
style="font-size: 16pt; font-family: "Century Gothic","sans-serif";">1:00
p.m. (refreshments at 12:45
p.m.)<span style=""> </span>Room 1022<o:p></o:p></span></p>
<p class="MsoNormal" style="border: medium none ; padding: 0in;"><span
style="font-family: "Century Gothic","sans-serif";"><o:p> </o:p></span></p>
</div>
<p class="MsoNormal"><i style=""><span
style="font-size: 9pt; font-family: "Century Gothic","sans-serif";"><o:p> </o:p></span></i></p>
<p class="MsoNormal" style="text-align: center;" align="center"><i
style=""><span style="font-family: "Century Gothic","sans-serif";">For
more
information, contact Teresa Rivas, ext 1437 or <a class="moz-txt-link-abbreviated" href="mailto:rivas@ucar.edu">rivas@ucar.edu</a></span></i><span
style=""><o:p></o:p></span></p>
<pre class="moz-signature" cols="72">--
______________________
Teresa Rivas
Administrator TIIMES
303-497-1437
<a class="moz-txt-link-freetext" href="http://www.tiimes.ucar.edu">http://www.tiimes.ucar.edu</a>
NCAR
The Institute for Integrative & Multidisciplinary Earth Studies (TIIMES)
P.O. Box 3000
FL1-2024
Boulder, CO 80307-3000</pre>
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