Shipboard Investigation of Air-sea Interaction and Cloud Processes in the VOCALS Stratocumulus Region

C. W. Fairall(1), D. Wolfe (1), S. Pezoa (1),S. de Szoeke(1), L. Bariteau (1, 2), Efthymios Serpetzoglou

(3), Virendra Ghate (3), and Paquita Zuidema (3)

Results from NOAA Stratus Cruises2001-2006

Observation SystemsAir-sea Fluxes, Clouds, Precipitation

Cloud Radar and Microwave Radiometer

Measurement Systems for PACS/Stratus Cruises

Instrument/Variable Oct 01 Nov 03 Dec 04 Oct 05 Oct 06 Flux X X X X X Sonde X X X X X Aerosol X X X X Microwave X X X X X Ceilometer X ~ X X X Cloud radar X X ~ C-band radar X X X Drizzle radar X X X X

96oW 90oW 84oW 78oW 72oW 66oW

32oS

24oS

16oS

8oS

0o

Cloud-Aerosol-Drizzle Connection

Cloud-aerosol Indirect Effect Example from Stratus2005:

Minimum in PBL aerosol concentration corresponds to broken cloud period and much higher transmission of solar flux to ocean.

Broken cloud period was during a POC with drizzling mesoscale cloud features.

Note cloud LWP about the same for solid vs broken clouds.

0 5 10 15 20 250

50

100IR

Clo

ud

Fo

rcin

g (

W/m

2 )x-01 o-03 dia-04 rt tri-05 *06

0 5 10 15 200.4

0.6

0.8

1

Local Time of Day (hr)

Clo

ud

fra

ctio

n (

m)

0 5 10 15 201000

1200

1400

1600

1800

Clo

ud

top

(m

)

x-01 o-03 dia-04 rt tri-05 *06

0 5 10 15 20800

1000

1200

1400

1600

Clo

ud

ba

se (

m)

0 5 10 15 200

100

200

LW

P (

g/m

2 )

x-01 o-03 dia-04 rt tri-05 *06

0 5 10 15 200

200

400

600

Local Time of Day (hr)

Clo

ud

Th

ick

(m)

0 5 10 15 20

102

Ae

roso

l (#

/cm3 )

Local Time of Day (hr)

x-01 o-03 dia-04 rt tri-05 *06

Deduce Cloud Optical Properties:Observed cloud transmission coefficient

294.5 294.6 294.7 294.8 294.9 2950

500

1000S

ola

r F

lux

(W/m

2 )

294.5 294.6 294.7 294.8 294.9 2950

0.5

1

Julian Day (2001)

So

lar

Tra

nsm

issi

on

Co

eff.

STRATUS Cloud Optical Properties:LWP and Aerosol Relationships

From the Diurnal Averaging

0 50 100 150 2000

1

2

3

4

5

Op

tica

l Th

ick/

(Nae

r1/

3)

LWP (g/m2)

x-01 o-03 dia-04 rt tri-05 *06

0 50 100 150 2000

5

10

15

20

25

Op

tica

l Th

ick)

LWP (g/m2)

x-01 o-03 dia-04 rt tri-05 *06

Calif Coast

145W Equatorial Pac

Observed Optical thickness vs Observed LWP. Calif coast Naer=300/cc; Eq Pac Naer=50/cc

Observed Optical thickness divided by 1-third power of Observed Aerosol Number Concentration versus Observed LWP

Daily-averaged Stratus observations:SST and Sea-air Temperature difference

280 300 320 340 36017.5

18

18.5

19

19.5

20

Ts

(C)

Local Time of Day (hr)

x-01 o-03 dia-04 rt tri-05 *06

280 300 320 340 360-0.5

0

0.5

1

1.5

2

Ts

- T

a (

C)

Local Time of Day (hr)

x-01 o-03 dia-04 rt tri-05 *06

280 300 320 340 3600

50

100IR

Clo

ud

Fo

rcin

g (

W/m

2 )x-01 o-03 dia-04 rt tri-05 *06

280 300 320 340 3600

0.5

1

Local Time of Day (hr)

Clo

ud

fra

ctio

n (

m)

280 300 320 340 36010

1

102

103

Ae

roso

l (#

/cm

3 )

Local Time of Day (hr)

x-01 o-03 dia-04 rt tri-05 *06

280 300 320 340 3600

100

200

300

LW

P (

g/m

2 )

x-01 o-03 dia-04 rt tri-05 *06

280 300 320 340 3600

500

1000

Local Time of Day (hr)

Clo

ud

Th

ick

(m)

280 300 320 340 3601000

1500

2000

2500

Clo

ud

top

(m

)

x-01 o-03 dia-04 rt tri-05 *06

280 300 320 340 360500

1000

1500

2000

Clo

ud

ba

se (

m)

Diurnal and Daily Average File Formats

• yxz(:,1)=jdd;Julian Day• yxz(:,2)=rld;Downward IR flux W/m^2• yxz(:,3)=rlclrd;Clear sky downward IR flux W/m^2• yxz(:,4)=rsd;Downward solar flux W/m^2• yxz(:,5)=rsclrd;Clear sky downward solar flux W/m^2• yxz(:,6)=tsgd;Ship thermosalinograph water temperature (5 m depth)• yxz(:,7)=tsd; ESRL seasnake water temperature (5 cm depth)• yxz(:,8)=tad; Air Temperature (18 m) C• yxz(:,9)=tau opt; Cloud optical thickness• yxz(:,10)=zbmd; Median cloud base height m• yxz(:,11)=topd; Cloud top height• yxz(:,12)=wmd; Cloud liquid water path g/m^2• yxz(:,13)=cldfd; Cloud fraction• yxz(:,14)=aer_mnd1; Aerosol number, size>.1 micron and size<.2 micron• yxz(:,15)=aer_mnd2; Aerosol number, size>.3 micron and size<.5 micron• yxz(:,16)=aer_mnd3; Aerosol number, size>1 micron and size<5 micron• yxz(:,17)=yrr; Year of the cruise• yxz(:,18)=raind; Rain rate mm/hr• yxz(:,19)=uxd; Northerly wind component m/s• yxz(:,20)=uyd; Easterly wind component m/s• yxz(:,21)=ud; Wind speed m/s• yxz(:,22)=hsd; Sensible heat flux W/m^2• yxz(:,23)=hld; Latent heat flux W/m^2• yxz(:,24)=taud; Stress N/m^2• yxz(:,25)=zb1d; 15% cloud base height m• yxz(:,26)=clodthkd; Cloud thickness m• yxz(:,27)=ndd; Number cloud drops deduced from optical thickness• yxz(:,28)=latd; Latitude• yxz(:,29)=lond; Longitude