CRISTA validation of ROSE/DLR v2.4

Data from the CRISTA-2 (Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere) mission from 8.-16. August 1997 were used for a validation of the ROSE/DLR model. Information about CRISTA-2 can be found on the CRISTA homepage. Results of a CRISTA validation campaign is given in table 3. Total ozone columns were calculated from CRISTA-2 derived ozone profiles and assimilated into the ROSE model. Afterwards, profiles modelled by ROSE were compared with the original CRISTA-2 profiles. The number of CRISTA-2 measurements on each ROSE level is given in table 1 and the number of CRISTA-2 profiles used is given in table 2.

Validation of ROSE/DLR v 2.2 with CRISTA-2 revealed significant differences between model and measurements especially in the mid latitude and subpolar region.

As a first, pragmatic approach to correct this model behaviour SAGE measurements are used. A height and latitude dependent factor between ROSE/DLR ozone profiles and SAGE II measurements is calculated for four seasons. This factor is applied to the modeled ozone profiles as a last step before the data output.  During that 'correction' the total ozone column amount remains constant to avoid any smoothing effect.

Explanations for these differences between measurements and model are under examination.

Results

Figures 1,3,5,7,9,11,13 show the comparison of the mean, modelled ROSE ozone profile (black) versus the mean, measured CRISTA-2 ozone profile (blue) for a certain latitude interval. A green area marks the standard deviation of all ROSE profiles used in the comparison and black bars mark the standard deviation of all CRISTA-2 profiles used in the comparison. Looking at averaged profiles is justified through a relatively 'quiet' meteorological situation during the CRISTA-2 mission.

Figures 2,4,6,8,10,12,14 show the relative (black) and absolute (red) difference between the mean, modelled ROSE ozone profile and the mean, measured CRISTA-2 ozone profile. The relative difference is calculated as the ratio of absolute difference and CRISTA-2 measured value.

Figure 1: Mean, modelled ROSE ozone profile (black) versus the mean, measured CRISTA-2 ozone profile (blue) for 60 - 74 deg North. Green area marks standard deviation of all ROSE profiles and black bars mark the standard deviation of all CRISTA-2 profiles used.

Figure 2: Relative (black) and absolute (red) difference between the mean, modelled ROSE ozone profile and the mean, measured CRISTA-2 ozone profile for 60 - 74 deg North.

Figure 3: Mean, modelled ROSE ozone profile (black) versus the mean, measured CRISTA-2 ozone profile (blue) for 40 - 60 deg North. Green area marks standard deviation of all ROSE profiles and black bars mark the standard deviation of all CRISTA-2 profiles used.

Figure 4: Relative (black) and absolute (red) difference between the mean, modelled ROSE ozone profile and the mean, measured CRISTA-2 ozone profile for 40 - 60 deg North.

Figure 5: Mean, modelled ROSE ozone profile (black) versus the mean, measured CRISTA-2 ozone profile (blue) for 20 - 40 deg North. Green area marks standard deviation of all ROSE profiles and black bars mark the standard deviation of all CRISTA-2 profiles used.

Figure 6: Relative (black) and absolute (red) difference between the mean, modelled ROSE ozone profile and the mean, measured CRISTA-2 ozone profile for 20 - 40 deg North.

Figure 7: Mean, modelled ROSE ozone profile (black) versus the mean, measured CRISTA-2 ozone profile (blue) for 20 deg South to 20 deg North. Green area marks standard deviation of all ROSE profiles and black bars mark the standard deviation of all CRISTA-2 profiles used.

Figure 8: Relative (black) and absolute (red) difference between the mean, modelled ROSE ozone profile and the mean, measured CRISTA-2 ozone profile for 20 deg South to 20 deg North.

Figure 9: Mean, modelled ROSE ozone profile (black) versus the mean, measured CRISTA-2 ozone profile (blue) for 20 - 40 deg South.
Green area marks standard deviation of all ROSE profiles and black bars mark the standard deviation of all CRISTA-2 profiles used.

Figure 10: Relative (black) and absolute (red) difference between the mean, modelled ROSE ozone profile and the mean, measured CRISTA-2 ozone profile for 20 - 40 deg South.

Figure 11: Mean, modelled ROSE ozone profile (black) versus the mean, measured CRISTA-2 ozone profile (blue) for 40 - 60 deg South.
Green area marks standard deviation of all ROSE profiles and black bars mark the standard deviation of all CRISTA-2 profiles used.

Figure 12: Relative (black) and absolute (red) difference between the mean, modelled ROSE ozone profile and the mean, measured CRISTA-2 ozone profile for 40 - 60 deg South.

Figure 13: Mean, modelled ROSE ozone profile (black) versus the mean, measured CRISTA-2 ozone profile (blue) for 60 - 74 deg South.
Green area marks standard deviation of all ROSE profiles and black bars mark the standard deviation of all CRISTA-2 profiles used.

Figure 14: Relative (black) and absolute (red) difference between the mean, modelled ROSE ozone profile and the mean, measured CRISTA-2 ozone profile for 60 - 74 deg South.

Comparison statistics (same as for the comparison CRISTA-2 vs. ROSE/DLR v2.2):

ROSE level no. No. CRISTA-2 data ROSE level no. No. CRISTA-2 data ROSE level no. No. CRISTA-2 data
1 54 15 23139 29 17717
2 379 16 23178 30 14715
3 1206 17 23204 31 8879
4 3394 18 23221 32 3923
5 8628 19 23189 33 1253
6 14747 20 23089 34 283
7 18476 21 22971 35 58
8 21125 22 22839 36 7
9 22054 23 22714 37 1
10 22574 24 22557    
11 22807 25 22310    
12 22954 26 21893    
13 23031 27 21301    
14 23081 28 19982    

Table 1: Frequency distribution of used CRISTA-2 ozone profile data (on ROSE levels)

geographical region no. of profiles in CRISTA vs. ROSE comparison
60 - 74 deg North 2574
40 - 60 deg North 3355
20 - 40 deg North 3025
20 deg South - 20 deg North 5736
20 -40 deg South 2986
40 - 60 deg South 3316
60 - 74 deg South 2426

Table 2: Number of CRISTA-2 profiles used in the comparison separated in geographical regions.

  systematic error [%] statistical error [%]
height [km] 40 deg South 0 deg 40 deg North 40 deg South 0 deg 40 deg North
55 26 25 25 8.6 6.8 5.6
50 16 14 13 2.4 2.1 1.9
45 12 12 12 2.0 2.0 2.0.
35 9 11 10 109 1.7 1.8
25 9 10 10 107 2.1 2.0
20 14 19 10 2.4 5.7 4.2

Table 3: CRISTA-2 systematic and statistical error derived from comparisons with ozone soundings. Relative errors refer to volume mixing ratios [ppmv]. Error estimation below 19 km was not possible due to the small ozone mixing ratios of 0.1 - 0.2 ppmv which is below the detection limit. (University of Wuppertal, 2000)

The World Data Center for Remote Sensing of the Atmosphere is a service of the German Remote Sensing Data Center (DFD)

Copyright © 1997, 1998, 1999, 2000, 2001, 2002 German Aerospace Center (DLR)

Author: Marion Schroedter-Homscheidt