in situ validation of the suppression of rain by smoke from forest fires in the amazon d. rosenfeld...

In Situ Validation of the Suppression of Rain by Smoke

from Forest Fires in the Amazon

D. Rosenfeld and A. Khain (1), A. A. Costa (2), J. C. P. de Oliveira (3), M.O. Andreae (4), P. Artaxo (5)

1. Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel

2. Universidade Estadual do Ceará, Av. Paranjana, 1700 - Campus do Itaperi - Fortaleza - CE / CEP 60740-000, Brazil, [email protected]

3. Universidade Federal do Ceará, Campus do Pici, Caixa Postal 6030 – Fortaleza-CE / CEP 60455-760, Brazil

4. Biogeochemistry Department, Max Planck Institute for Chemistry, P.O. Box 3060, D-55020 Mainz, Germany

5. Instituto de Fisica, Universidade de Sao Paulo, Rua do Matao, Travessa R, 187, CEP 05508-900, Sao Paulo, Brazil

VIRS+PR, Amazon, 1998

13 SEP 14:15

VIRS T-Re

TOMS Aerosol Index13 September 1998

Note that clouds do not precipitate before reaching height of 6.5 km or –12oC isotherm, while containing ample cloud water.

The “Green Ocean” turns dry: Smoky clouds over the Amazon

Note the shallow precipitating clouds, extensive warm rainout, glaciation at T>-10oC, and few lightning

TRMM VIRS+PR, Amazon, 1998 04 13 16:28

VIRS T-Re

The “Green Ocean”: Maritime clouds over the Amazon

North of Ji Parana, 4 October 2002, 16:03 GMT. Moderate smoke,

0 1000 2000 3000 4000 5000 6000 70000

2000

4000

6000

8000

10000

12000

14000

16000Flight 11: 4 Oct 2002

CN, cm-3

CN, cm-3

Pre

ssu

re A

ltit

ud

e0

2000

4000

6000

8000

10000

12000

14000

16000

0

1000

2000

3000

4000

5000

6000

7000

3.753 1043.753 1043.753 1043.753 1043.753 1043.753 104

Flight 11: 4 Oct 2002

P-Alt. CN, cm-3

Pre

ssu

re A

ltit

ud

e

CN

, cm-3

DateTime

MODIS AQUA, 7S-12S, 62W-66W, 4 October 2002, 17:50 GMT.

0.001

0.01

0.1

1

10

100

1000

0 10 20 30 40 50

DSD20021004_H1

151510Z 1731m

151819Z 1899m

152211Z 2150m

152650Z 3069m

153101Z 3635m

153544Z 4265m

N [

cm-3

]

Drop diameter [m]

Lightly smoky conditionsNorth of JPR, Noon.

Near Cruzeiro do Sul, 4 October 2002, 22:10 GMT. Warm Rain, 2.5 km

MODIS AQUA, 5S-10S, 64W-71W, 4 October 2002, 17:50 GMT.

0 1000 2000 3000 4000 5000 6000 70000

2000

4000

6000

8000

10000

12000

14000

16000Flight 14: 5 Oct 2002

CN, cm-3

CN, cm-3P

ress

ure

Alt

itu

de

0

2000

4000

6000

8000

10000

12000

14000

16000

0

1000

2000

3000

4000

5000

6000

7000

3.753 1043.753 1043.753 1043.753 1043.753 1043.753 1043.753 1043.753 104

Flight 14: 5 Oct 2002

P-Alt. CN, cm-3

Pre

ssu

re A

ltit

ud

e

CN

, cm-3

DateTime

0.001

0.01

0.1

1

10

100

1000

0 10 20 30 40 50

DSD20021005_1

163826Z 1475m164111Z 1541m164542Z 2092m165904Z 2948m170418Z 3275m171156Z 3548m172121Z 3631m172157Z 4250m

N [

cm-3

]

Drop diameter [m]

Warm rain evolution over the western tip of the Amazon, Noon.

0.001

0.01

0.1

1

10

100

1000

0 10 20 30 40 50

DSD20021005_2

195200Z 1597m195506Z 1890m195930Z 2338m200551Z 2781m201401Z 2980m202142Z 3640m202635Z 4403m

N [

cm-3

]

Drop diameter [m]

Warm rain evolution over the western tip of the Amazon, afternoon.

0.001

0.01

0.1

1

10

100

1000

0 10 20 30 40 50

DSD20021004_H1

151510Z 1731m

151819Z 1899m

152211Z 2150m

152650Z 3069m

153101Z 3635m

153544Z 4265m

N [

cm-3

]

Drop diameter [m]

Lightly smoky conditionsNorth of JPR, Noon.

Many more droplets for the same supersaturation

Summary of CCN Spectra

Smoky Clean

Smoky Clean

0

0.5

1

1.5

2

2.5

3

3.5

4

0 20 40 60 80 100 120

run92110_rain

Clean 92110

Smoky 9219

Av

era

ge

Ra

in I

nt.

[m

m/h

r]

T [min]

The smoke decreases the rainfall amounts.

0

5

10

15

20

0 1000 2000 3000 4000 5000 6000 7000 8000

W_921_9_921_10

Smoky

Clean

Max

Up

dra

ft [

m s

-1]

t [s]

The smoke increases the updrafts intensity.

Conclusions

1. The aircraft measurements in clean and smoky clouds, up to the 0oC isotherm confirm and strengthen the previous satellite inferences of smoke suppressing warm precipitation in convective clouds.

2. Apparently the giant ash CCN are not significant in initiation of warm rain, even in pyro-cumulus.

3. Model simulations replicate the aircraft measurements and extrapolate them to greater heights in the clouds, supporting the observations that smoky clouds have to exceed the -10oC isotherm level for start precipitating.

4. Simulations show that smoky cumulonimbus produce less precipitation than clean clouds under the same conditions.

5. However, the updrafts velocities in smoky clouds are stronger and supercooled water content is greater, providing better conditions for cloud electrification.

0 5 10 15 20 25 30 35

-40

-30

-20

-10

0

10

20

reff

T [

oC

]

m]

Glaciated

Mixed PhaseRainout

Coalescence

General

Diffusional growth

0 5 10 15 20 25 30 35

-40

-30

-20

-10

0

10

20

reff

T [

oC

]

m]

Glaciated

Mixed Phase

Rainout

Coalescence

Maritime

0 5 10 15 20 25 30 35

-40

-30

-20

-10

0

10

20

reff

T [

oC

]

m]

Glaciated

Mixed Phase

Coalescence

Continental - moderate

Diffusional growth

0 5 10 15 20 25 30 35

-40

-30

-20

-10

0

10

20

reff

T [

oC

]

m]

Glaciated

Mixed Phase

Continental - extreme

Diffusional growth

The classification scheme of convective clouds into microphysical zonesaccording to the shape of the temperature – effective radius relations

Note that in extremely continental clouds re at cloud base is very

small, the coalescence zone vanishes, mixed phase zone starts at T<-15oC, and the glaciation can occur at the most extreme situation at the height of homogeneous freezing temperature of –39oC. In contrast, maritime clouds start with large re

at their base, crossing the precipitation threshold of 14 m short distance above the base. The deep rainout zone is indicative of fully developed warm rain processes in the maritime clouds. The large droplets freeze at relatively high temperatures, resulting in a shallow mixed phase zone and a glaciation temperature reached near –10oC

in situ validation of the suppression of rain by smoke from forest fires in the amazon d. rosenfeld...

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