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Precipitation Changes, Uncertainties, and Associated Impacts to the Arctic Environment. Michael Rawlins Alexander Shiklomanov Richard Lammers Katelyn Dolan Charles Vorosmarty. Arctic Research Consortium of the United States 2007 Annual Meeting and Arctic Forum May 24, 2007. - PowerPoint PPT Presentation
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Precipitation Changes, Uncertainties, and Associated
Impacts to the Arctic Environment
Michael Rawlins
Alexander Shiklomanov
Richard Lammers
Katelyn Dolan
Charles Vorosmarty
Arctic Research Consortium of the United States
2007 Annual Meeting and Arctic Forum
May 24, 2007
It is very likely that precipitation over the past century has
increased across the mid and high-latitudes of the Northern
Hemisphere---with the largest trends having come during
winter---and recent model simulations suggest that future
increases are likely to occur.
Summary Statement:
20th Century Precipitation Changes
“It is probable that there
was an increase in arctic
precipitation over the past
century”
Arctic Climate Impacts
Assessment, 2005
The largest increases have
occurred during winter
Arctic Climate Impacts
Assessment, 2005
• All 21 AR4 models have increasing trend in ensemble mean
• Only 4 have an ensemble run with a negative trend result
Kattsov et al., JGR, in press
Winter trends are similar to
annual means
Summer shows no systematic
changes
Kattsov et al., JGR, in press
Frequency of summer wet days and days with heavy rains
Sun and Groisman, 2000, Int. J. Climatol.
Trends in annual precipitation for the western part of the
former USSR (years: 1936-1997)
North of 60 N: Significant trend in TOTAL and HEAVY (90th percentile) P
South of 55 N: Significant trend in TOTAL, HEAVY and VERY HEAVY (99th) P
Key Uncertainties in Estimating Arctic Precipitation
• The sparse network of in situ observations
• The difficulty in obtaining estimates of solid precipitation in
windy environments
• Slow progress in exploiting remote sensing techniques for
measuring high-latitude precipitation
• Compounding effects of elevation on precipitation
Arctic Climate Impacts Assessment, 2005
Rawlins et al., 2006, GRL
Counterintuitive precipitation trends, relative to discharge trend, partially explained by gage density
change
Gauge undercatch is a significant problem, especially in winter
Yang et al., 2005, GRL
January Correction Factor July Correction Factor
Most General Circulation
Models (GCMs) tend to
overestimate precipitation...
http://igloo.atmos.uiuc.edu/IPCC/
Future Precipitation Changes
Precipitation increases (2000-2100) are projected to
be greatest during winter across high northern
latitudes
IPCC 4th Assessment, 2007
December-February June-August
• All model suggest future precipitation increases across region 60N –
pole
• Departures range between 5 to 15 cm (~ 10% to 30% of mean)
http://igloo.atmos.uiuc.edu/IPCC/
The models suggest that precipitation increases across the Arctic will far
exceed the global trends.
Kattsov et al., JGR, in press
Winter Cyclones in the NCAR CCSM3
• Increased cyclone-associated precipitation
• Increased atmospheric precipitable water
Percent Increase in Precipitable Water
Finnis et al., JGR, in press
*
*
*
** *
Magnitude of P-E changes (1950-2050) vary widely among models and are
significantly correlated with initial precipitation conditions
Holland et al., JGR, in press
Changes in Snowfall and Impact on
River Runoff
Discharge from the
major Russian rivers
has increased...
Peterson et al., 2002, Science
...but annual precipitation does not explain the increase
Berezovskaya et al., 2002, GRL
Discharge trends are greatest in the north
where permafrost is most extensive...
A. Shiklomanov, U. New Hampshire
...and where snowfall increases are also noted
Derived Snowfall Derived Rainfall
Rawlins et al., 2006, GRL
The snowfall trends are consistent, spatially,
with trends in observed runoff
Scenarios for future snowfall show both winners and losers
Rawlins et al., 2007, in prep.
Larger changes emerge for the more extreme A2 emissions scenario
Rawlins et al., 2007, in prep.
Summary
• In situ data show an increase in 20th century precipitation. Largest
increase in winter season.
• Positive snowfall trends are noted where increases in Eurasian
river discharge have occurred.
• Models depict future precipitation and P-E increases, but spread
is significant.
• Estimates of derived snowfall useful for regional water resource
assessments.