Precipitation Changes, Uncertainties, and Associated Impacts to the Arctic Environment

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.