WP3.1 Radiative closure (EUCAARI)

Radiative closure

• Use in-situ measured (and inferred) aerosol optical properties and radiative transfer code to model fluxes

• Compare with broad band radiometer measurements on aircraft

• To date:– Identification of suitable flights (B362 and B374)– Assessment of accuracy of BBRs and need for

pitch/roll corrections– Preliminary calculations with Edwards and Slingo

(1996)

B362 May 6, 2008

58

56

54

52

50

48

La

titu

de

(d

eg

)

1050-5Longitude (deg)

Flight Track

B362

100

80

60

40

20

0

CN

(cm-310

3)

12:0006/05/2008

12:15 12:30 12:45 13:00 13:15

Time (GMT)

1.0

0.8

0.6

0.4

0.2

SS

A

12

8

4

abs - 550 nm

(m·10

-6)

300

200

100

0 sca

t-55

0 nm

(m

·10

-6)

15x103

10

5

0

Alt

(fee

t)

80

60

40

20

RH

(%)

1000

800

600

400

200

0

CO

(ppm

)

Run 6 - B to A, 10 kft Run 7- B to A, 2.5 kft Run 8 - A to B, 100 ft

B362

B374 – Radiation flight with CMET

58

56

54

52

50

La

titu

de

(de

g)

-10 -5 0Longitude (deg)

Flight Track

May 14, 2008

51.3

51.2

51.1

51.0

50.9

50.8

50.7

Latit

ude

(deg

)

-13.5 -13.0 -12.5 -12.0 -11.5 -11.0Longitude (deg)

B A

τ(dry)=0.21

τ(dry)=0.24

BBR data from B374

1250

1200

1150

1100

1050

1000

Dow

nwel

ling

Rad

iatio

n / c

os(S

ZA

) (

W m

-2))

-13.0 -12.5 -12.0 -11.5Longitude (along 51 N line)

DRE = -17. 5 W m-2

Run 7 at 24,000 ft (390 mb) Run 5 at 6000 ft Run 2 at 2400 ft (930 mb) Runs 3,4 at 100 ft

Modelled clear sky flux (no aerosol)

With aerosol (dry)

Aerosol hygroscopicity during B374

120x10-6

80

40

0

Nep

h G

reen

Sca

tterin

g (5

50 n

m)

10:0014/05/2008

11:00 12:00 13:00 14:00

dat

80

60

40

20

0

RH

(%

) Green Dry Scattering Green Wet Scattering Wet RH Dry RH

1.8

1.6

1.4

1.2

1.0Hyg

rosc

opic

gro

wth

fact

or, f

(RH

)

908070605040Relative Humidity (%)

Wet nephelometer provides f(RH), ϐ/ ϐ0

Need D/D0 for full mie scattering code(Tang 1997 growth not appropriate)

Further work

• Still to do….– Radiative closure with BBRs for aerosol runs

(wet aerosol – properties now available from use of wet neph data)

– Analysis of orbits/SWS/SHIMS data (to be done by Debbie O’Sullivan, Met Office)

– More radiation flights?