The Effect of SW Drought on Precipitation of

Evapotranspired Origin

1.Hydrology and Water Resources 2.Atmospheric Sciences 3.School of Natural Resources 4.Universidad de Antioquia, Colombia

Francina Dominguez1,2

Juan Camilo Villegas3,4

David D. Breshears3

The goal is to understand how hydrologic variability in the Southwest affects the export of moisture

Dynamic precipitation recycling model

Effect of SW Drought on subsequent Precipitation

R1 exp wd '

0

Export of Moisture from the SW Region

“Hydrologic connectivity is the water-mediated transport of matter, energy and organisms within or between elements of the hydrologic cycle. (Pringle, 2001)

The atmospheric paths of moisture that connect hydrologic units are poorly understood.

What are the effects of changes in atmospheric hydrologic connectivity?

atmospheric

surface

sub surface

Dynamic Precipitation Recycling Model

Dynamic Recycling Model

Dominguez, F. et al., 2006. J. Climate

R1 exp wd '

0

PEywv

xwu

tw

)()(

The principle for all analytic recycling models is the conservation of atmospheric moisture

In the past, recycling models have assumed that the change in moisture storage is negligible.

New model relaxes this assumption

Dynamic Recycling Model

R = (local recycling ratio) w(precipitable water)E(evapotranspiration)

R1 exp wd '

0

In order to solve the equation we change the coordinate system to follow the motion of the air.

0

'exp1 dR

utx

t

To solve, change coordinate system.

vty We basically follow the path of the air.

)1()1( RR

The equation becomes a simple ODE.

mmmm PEyvw

xuw

tw

)()(

R = (local recycling ratio) w(precipitable water)E(evapotranspiration)

Dynamic Recycling Model

In addition to recycling ratios, we can calculate source-sink regions of atmospheric moisture.

Dynamic Recycling Model

R1 exp wd '

0

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

What is the spatial extent of precipitation originating as ET from the South Western US?

Export of SW ET

?

North American Regional Reanalysis (NARR) data. Warm season (Apr-Sep)

Jul 1-15 (1996-1999)

Evapotranspiration from the South West affects precipitation across the United States.

Precipitation originating as ET from SW region.

Legenddgtv13<VALUE>

0 - 0.1

0.2

0.3

0.4

Percent of total Precipitation (falling in each pixel) that originates as ET from SW region.

Legenddgtv11<VALUE>

0 - 0.025

0.026 - 0.05

0.051 - 0.075

0.076 - 0.1

0.101 - 0.15

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Export of SW ET

0.15

0.25

Jul_a

Jul_b

Aug_

a

Aug_

b

Sep_

a

Sep_

b

ET 4

-Cor

ners

(mm

/day

)

Jul 16-31 (1996-1999)

Evapotranspiration from the South West affects precipitation across the United States.

Legenddgtv13<VALUE>

0 - 0.1

0.2

0.3

0.4

Legenddgtv11<VALUE>

0 - 0.025

0.026 - 0.05

0.051 - 0.075

0.076 - 0.1

0.101 - 0.15

Precipitation originating as ET from SW region.

Percent of total Precipitation (falling in each pixel) that originates as ET from SW region.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Export of SW ET

0.15

0.25

Jul_a

Jul_b

Aug_

a

Aug_

b

Sep_

a

Sep_

b

ET 4

-Cor

ners

(mm

/day

)

Aug 1-15 (1996-1999)

At the peak of the Monsoon season, we see a peak in recycled precipitation.

Legenddgtv13<VALUE>

0 - 0.1

0.2

0.3

0.4

Legenddgtv11<VALUE>

0 - 0.025

0.026 - 0.05

0.051 - 0.075

0.076 - 0.1

0.101 - 0.15

Precipitation originating as ET from SW region.

Percent of total Precipitation (falling in each pixel) that originates as ET from SW region.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Export of SW ET

0.15

0.25

Jul_a

Jul_b

Aug_

a

Aug_

b

Sep_

a

Sep_

b

ET 4

-Cor

ners

(mm

/day

)

Aug 16-31 (1996-1999)

Legenddgtv13<VALUE>

0 - 0.1

0.2

0.3

0.4

Legenddgtv11<VALUE>

0 - 0.025

0.026 - 0.05

0.051 - 0.075

0.076 - 0.1

0.101 - 0.15

At the peak of the Monsoon season, we see a peak in recycled precipitation.

Precipitation originating as ET from SW region.

Percent of total Precipitation (falling in each pixel) that originates as ET from SW region.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Export of SW ET

0.15

0.25

Jul_a

Jul_b

Aug_

a

Aug_

b

Sep_

a

Sep_

b

ET 4

-Cor

ners

(mm

/day

)

Sep 1-15 (1996-1999)

Toward the end of the Monsoon, RP diminishes.

Legenddgtv13<VALUE>

0 - 0.1

0.2

0.3

0.4

Legenddgtv11<VALUE>

0 - 0.025

0.026 - 0.05

0.051 - 0.075

0.076 - 0.1

0.101 - 0.15

Precipitation originating as ET from SW region.

Percent of total Precipitation (falling in each pixel) that originates as ET from SW region.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Export of SW ET

0.15

0.25

Jul_a

Jul_b

Aug_

a

Aug_

b

Sep_

a

Sep_

b

ET 4

-Cor

ners

(mm

/day

)

Sep 16-30 (1996-1999)

Legenddgtv13<VALUE>

0 - 0.1

0.2

0.3

0.4

Legenddgtv11<VALUE>

0 - 0.025

0.026 - 0.05

0.051 - 0.075

0.076 - 0.1

0.101 - 0.15

Toward the end of the Monsoon, RP diminishes.

Precipitation originating as ET from SW region.

Percent of total Precipitation (falling in each pixel) that originates as ET from SW region.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Export of SW ET

0.15

0.25

Jul_a

Jul_b

Aug_

a

Aug_

b

Sep_

a

Sep_

b

ET 4

-Cor

ners

(mm

/day

)

Effects of Southwest drought on subsequent precipitation of evapotranspired origin.

Even though NARR doesn’t account for vegetation variability, ET varies as NDVI.

0.1

0.15

0.2

0.25

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Flux

es F

our

Cor

ners

Jul

-Sep

(mm

/day

)

ETPP

Jul – Sep ET and PP

NDVI for late May-June the region encompassing P. edulis (Breshears et al.,2005)

NDVI

0.1

0.15

0.2

0.25

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

ET F

our C

orne

rs J

ul-S

ep (m

m/d

ay)

Precipitation originating as ET from 4-Corners Region varies in agreement with evapotranspiration.

Drought and Recycling

0

0.05

0.1

0.15

0.2

0.25

0.3

0.3519

96

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Prec

ip. O

rigin

atin

g as

ET

from

SW

(m

m/d

ay)

LocalNon-Local

0

0.5

1

1.5

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Rat

io L

ocal

/Non

Loc

al

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Prec

ip. O

rigin

atin

g as

ET

from

SW

(mm

/day

)

LocalNon-Local

Legenddgtv13<VALUE>

0 - 0.1

0.2

0.3

0.4

The drought period presented a sharp decrease in precipitation originating as ET.

Drought and Recycling

Pre-Drought Severe Drought

Legenddgtv13<VALUE>

0 - 0.1

0.2

0.3

0.4

Drought Transition

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Prec

ip. O

rigin

atin

g as

ET

from

SW

(mm

/day

)

LocalNon-Local

Legenddgtv11<VALUE>

0 - 0.025

0.026 - 0.05

0.051 - 0.075

0.076 - 0.1

0.101 - 0.15

This meant that the % of precipitation originating as SW-ET considerably diminished during the drought.

Drought and Recycling

Legenddgtv11<VALUE>

0 - 0.025

0.026 - 0.05

0.051 - 0.075

0.076 - 0.1

0.101 - 0.15

Pre-Drought Severe Drought Drought Transition

2%

6%

10%

14%

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

% o

f Pre

cip.

orig

inat

ing

as S

W E

T Ju

l-Sep

NESDWYKSSW

Adjacent states receive approximately 10% of their Jul-Sep precipitation from the Southwest.

Drought and Recycling

This value dropped to around 6% during the drought

The Dynamic Recycling Model has enabled us to analyze the regions where ET from the Southwest contributes to precipitation.

Including intraseasonal variability.

Conclusions

In conclusion…

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Pre

cip.

Orig

inat

ing

as E

T fro

m

SW

(mm

/s)

LocalNon-Local The recent SW drought had a

significant impact on the precipitation originating as ET from the SW region.

Further Thoughts…

NARR doesn’t include vegetation variability, hence doesn’t account for the regional-scale die-off.

Could the vegetation die-off amplify the effect of the drought on remote precipitation?

Questions?Questions?