the inter-comparison of sciamachy and radar cloud top heights

The inter-comparison of SCIAMACHY and radar cloud top

heights

Alexander A. Kokhanovsky(1), C. Naud(2), A. Devasthale(3)

(1)Institute of Remote Sensing, Bremen UniversityBremen, Germany

(2) NASA GISS, New York, USA(3) Max Planck Institute for Meteorology, Hamburg, Germany

alexk@iup.physik.uni-bremen.de

CONTENTS

1. Rationale

2. Cloud retrievals using SACURA: the accuracy of the forward model

3. Inter-comparison study

4. Conclusions

Rationale: The validation of satellite-derived cloud top heights is needed to establish

the accuracy of a given technique for the CTH determination. This can be done

either using highly accurate lidar or radar systems in space or on ground.

CLOUD RETRIEVALS USING SACURA: THE ACCURACY OF

THE FORWARD MODEL and the physical principles behind

retrievals

The cloud optical thickness determination: the physical principle

0.65 m ,2003Kokhanovsky and Rozanov

Symbols-SCIATRAN

The effective radius determination from a satellite ,2003Kokhanovsky and Rozanov 1.55 m

The cloud top height determination from a satellite The physical principle behind the retrieval

0250 , 5, 60l m

Preliminary results !

Teh cloud geometrical thickness/bottom height determination from a satellite

0 5.5 , =20, 60h km

Inter-comparisons

36.6N; 97.5W

Radar: 35-GHz Millimeter wave Cloud Radar

36.6N; 97.5W

ARM (USA):

25min 0.5deg

Low clouds

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00

500

1000

1500

2000

2500

3000

10.03.2003

CT

H, m

CF

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00

500

1000

1500

2000

2500

3000

28.03.2003

CT

H, m

CF

scia scia

CF CFradar

Low clouds

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00

500

1000

1500

2000

2500

3000

22.05.2007

CT

H, m

CF

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00

500

1000

1500

2000

2500

3000

06.11.2003

CTH

, m

CFCF CF

scia scia

radar

High Clouds

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00

2000

4000

6000

8000

10000

12000

14000

04.06.2003

CT

H, m

CF

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00

2000

4000

6000

8000

10000

12000

14000

12.11.2003

CT

H, m

CF

High Clouds

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00

2000

4000

6000

8000

10000

12000

14000

22.11.2004

CT

H, m

CF0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

0

2000

4000

6000

8000

10000

12000

14000

31.10.2003

CT

H, m

CF

The inter-comparisons of CTHs derived using SCIAMACHY,

MODIS, and MERIS

0 2 4 6 8 10 12 14 160

2

4

6

8

10

12

14

16

C

TH

, km

(sa

telli

te)

CTH, km (radar)

SACURA/SCIAMACHY ESA/MERIS NASA/MODIS

radar

satellite

Date(d/m/year) Radar SCIA MERIS MODIS

10/03/2003 1.73 1.46 2.21 1.37

28/03/2003 2.04 1.45 2.01 2.91

22/05/2003 1.73 1.45 2.50 2.09

06/11/2003 1.32 1.44 1.71 -

16/11/2003 1.37 1.45 0.73 -

10/06/2004 1.86 2.30 1.61 -

26/ 04/2007 1.46 1.45 3.12 -

Table 2. Cloud top heights (in km) of high-level clouds derived from radar and satellite data

Date(d/m/year) Radar SCIA MERIS MODIS

17/04/2003 11.66 14.54 5.31 -

15/05/2003 11.54 9.35 5.20 10.39

04/06/2003 10.60 12.31 5.10 -

31/10/2003 13.20 11.87 6.61 11.32

12/11/2003 9.56 9.82 6.92 8.35

13/11/2003 10.64 8.09 6.91 9.51

22/11/2004 11.04 8.27 6.64 -

Table 1. Cloud top heights (in km) of low-level clouds derived

from radar and satellite data

Statistical data: average CTH (km)Radar SCIA MERIS MODIS

Low-level clouds

1.64 1.57 1.98 2.12

High-level clouds

10.46 10.0 6.10 9.89

Conclusions

• The max error of the cloud top height retrievals for low clouds (below 2km) is in the range [-0.5km; 0.5km]

• The max error for high clouds(10-12km) is in the range [-3km;+3km].

Acknowledgements

J. P. BurrowsW. von Hoyningen-Huene

V. V. Rozanov, H. Bovensmann, M. Vountas, W. Lotz

ESA, DLR