Precipitation Intensity

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Precipitation Intensity
Eric Salathé

• Climate Impacts GroupDepartment of Atmospheric
  SciencesUniversity of Washington

2
Climate Change North America
Summer
Winter
Annual
3
Climate Change Pacific Northwest Precipitation
Change in U.S. PNW precipitation by monthfrom
1990s to futuresimulated by 20 climate models
Precipitation Change ()
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Changes in Pacific Storm Track

• Consensus of current Global Climate Models
• Intensification of Mid-latitude storms
• Less frequent storms
• Northward shift in storm track

5
Shift in Pacific Storm Track
J Yin, Geophys Res Lett, 2005
Temperature Change 1980-2000 to 2080-2100
Change in Storm Growth
S Pole
S Pole
N Pole
N Pole
EQ
EQ
6
Shift in Pacific Storm Track
1950-2000 to 2050-2100 Nov-Dec-Jan
20th Century Model Composite
Observed (NCEP-NCAR Reanalysis)
21st Century Model Composite
Salathé, Geophys Res Lett, 2006
7
Shift in Aleutian Low
1950-2000 to 2050-2100 Nov-Dec-Jan
Observed
20th Century Model Composite
Salathé, Geophys Res Lett, 2006
8
Movement of Jetstream
1950s
9
Movement of Jetstream
1960s
10
Movement of Jetstream
1970s
11
Movement of Jetstream
1980s
12
Movement of Jetstream
1990s
13
Movement of Jetstream
1950s
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Are extreme rain events becoming more frequent?

• Valérie Dulière, Philip Mote, Eric Salathé,
  Josiah Mault and Marketa McGuire Elsner
• (Climate Impacts Group, University of Washington)

2008 Pacific Northwest Weather Workshop
Source THE OREGONIAN/Bruce Ely
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The Chehalis River flooding
Source THE OREGONIAN/Bruce Ely
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The Centralia station
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The Centralia station
Distribution function of daily precipitations from
1948 to 2006
10 cm
5 cm
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The Centralia station
Distribution function of daily precipitations from
1948 to 2006 (Zoom)
10 cm
5 cm
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The Centralia station
Distribution function of daily precipitations from
1948 to 2006 (Zoom)
1994, 1986
1951, 1981
1990
2006
1986
1990
2001
1996
1986
10 cm
5 cm
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The Centralia station
Distribution function of daily precipitations from
1948 to 2006 (Zoom)
Since 1948, 80 of the 20 greatest extreme daily
rain events occurred after 1985!
1994, 1986
1951, 1981
1990
2006
1986
1990
2001
1996
1986
10 cm
5 cm
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The Centralia station
Return period of annual maximum daily
precipitation
--1948-1976 --1977-2006
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The Past 50 Years
Source THE OREGONIAN/Bruce Ely
23
The Cooperative Observer Program network
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The Centralia station
Return period of annual maximum daily
precipitation
10-year Return

Percent Change
--1948-1976 --1977-2006
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Percentages of change in the annual maximum daily
precipitation with a 10 years return period for
each station
1
2
3
4
5
6
7
8
9
10
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1
2
3
4
5
6
7
10
8
9
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What Do Climate Models Project for the Future?
Source THE OREGONIAN/Bruce Ely
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Projected Future Changes from Climate
Models (2046-2065 versus 1981-2000)
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Projected Future Changes from Climate
Models (2046-2065 versus 1981-2000)
SRES A1B
SRES B1
IPSL
ECHAM5
CCSM3
Percentages of change in the annual maximum daily
precipitation with a 10 years return period for
each grid cell between 1981-2000 and 2046-2065.
30
Projected Future Changes from Climate
Models (2046-2065 versus 1981-2000)
SRES A1B
SRES B1
IPSL
18.8
11.8
ECHAM5
CCSM3
Percentages of change in the annual maximum daily
precipitation with a 10 years return period for
each grid cell between 1981-2000 and 2046-2065.
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Projected Future Changes from Climate
Models (2046-2065 versus 1981-2000)
SRES A1B
SRES B1
IPSL
18.8
11.8
ECHAM5
11.4
10.6
CCSM3
Percentages of change in the annual maximum daily
precipitation with a 10 years return period for
each grid cell between 1981-2000 and 2046-2065.
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Projected Future Changes from Climate
Models (2046-2065 versus 1981-2000)
SRES A1B
SRES B1
IPSL
18.8
11.8
ECHAM5
11.4
10.6
CCSM3
12.2
10.8
Percentages of change in the annual maximum daily
precipitation with a 10 years return period for
each grid cell between 1981-2000 and 2046-2065.
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Projected Future Changes from Climate
Models (2046-2065 versus 1981-2000)
Number of days per year with P gt 0.4 inches
Number of days per year
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Number of days per year with P gt 0.4 inches
P gt 1.6 inches
Number of days per year
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Projected Future Changes from Climate
Models (2046-2065 versus 1981-2000)
Number of days per year with P gt 0.4 inches
P gt 1.6 inches P gt 2.8 inches
Number of days per year
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GOING TO THE EXTREMES

• GOING TO THE EXTREMES AN INTERCOMPARISON OF
  MODEL-SIMULATED HISTORICAL AND FUTURE CHANGES IN
  EXTREME EVENTS CLAUDIA TEBALDI , KATHARINE
  HAYHOE, JULIE M. ARBLASTER and GERALD A. MEEHL,
  Climatic Change (2006) 79 185-211
• 9 Global Model Simulations for IPCC
• 1. Number of days with precipitation greater than
  10 mm (precip gt 10).
• 2. Maximum number of consecutive dry days (dry
  days).
• 3. Maximum 5-day precipitation total (5 day
  precip).
• 4. Simple daily intensity index, defined as the
  annual total precipitation divided by the number
  of wet days (precip intensity).
• 5. Fraction of total precipitation due to events
  exceeding the 95th percentile of the
  climatological distribution for wet day amounts (
  precip gt 95th).

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Going to Extremes
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Going to Extremes
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Mesoscale Effects

• Global models do not resolve fine-scale
  processes such as topographic precipitation
• Downscaling methods are used to account
  for regional effects
• Statistical downscaling uses observed
  relationship between large-scale and fine-scale
  patterns to extrapolate to climate model results
• Regional climate model simulates fine-scale
  physical processes

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Change in Orographic Enhancement
1990-2000 to 2045-2055 Sept-Oct-Nov
Downscaling without wind effect
Downscaling with wind effect
Salathé, Geophys Res Lett, 2006
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Mesoscale Climate Model

• Based on Regional Weather Model (MM5, WRF)
• Nested grids 135-45-15 km
• Advanced land-surface model (NOAH) with
  interactive deep soil temperature
• Global Climate Model used as Input (boundary
  conditions)

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Autumn Precipitation Changes
Change in Orographic Enhancement
Change in Autumn precipitation rate from 1990s to
2050sas simulated in regional climate model
WindsShift toOnshore
Rain increases along mountain ridge
mm per day
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MM5 vs Statistical Downscaling
Statistical Downscaling
MM5
P only
P Wind
Change in November Precip (mm/day) 1990s to
2050s
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• Conclusions
• This is the beginning of our work.
• According to the observations from the COOP
  network, extreme rain events have globally
  increased in frequency and intensity between
  1948-1976 and 1977-2006 over the Washington
  state.
• According to global climate models (IPSL, ECHAM5
  and CCSM3), extreme rain events will in average
  be more intense and more frequent in 2046-2065
  than now, over the PNW region.
• Coming next
• Analysis of output from regional climate models.

Source http//www.earthcam.com/