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Envisat Symposium, April 23 – 27, 2007, Montreux bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Cloud sensitivity studies.

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Presentation on theme: "Envisat Symposium, April 23 – 27, 2007, Montreux bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Cloud sensitivity studies."— Presentation transcript:

1 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Cloud sensitivity studies for stratospheric and lower mesospheric ozone profile retrievals from limb scattered solar radiance T. Sonkaew, C. von Savigny, A. Rozanov, V. Rozanov, H. Bovensmann and J.P. Burrows Institute of Environmental Physics and Remote Sensing, University of Bremen, Bremen, Germany

2 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Outline Introduction Methodology Retrieval algorithm and Forward simulation Linear approximation Sensitivity studies Weighting functions Cloud parameters Ground albedo Viewing angles Conclusions Future work 2

3 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Introduction Clouds cover 60% of atmosphere, 7% of tropospheric volume. [Lelieveld et al., 1989 and Pruppacher and Jaenicke, 1995] Photo by R. Macatangay The reflectance at 443 nm from SCIAMACHY data using SACURA, 1 Jan 2006 – 31 Dec 2006 3

4 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Introduction Clouds interact with the incoming solar radiation and long wavelength radiation emitted from the Earth. Clouds have an impact on the trace gas retrieval. 4 line of sigh t

5 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen How to estimate the impact of clouds on the ozone retrieval? Cloudiness scenario Cloud free scenario Simulated limb radiance spectra Retrieval in cloud free scenario Ozone vertical profile Ozone profile in cloudy atmosphere True ozone profile Radiative transfer code “ SCIATRAN ” Vertical P, T and albedo 5

6 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Retrieval Algorithm Combined the O 3 profile in the Hartley, Huggins and Chappuis bands Burrows et al., [1999] 1 = 525 nm 3 =675 nm 2 =602 nm The Chappuis bands in visible allow to retrieve O 3 between 15-40 km [Flittner,2000; McPeters,2000; von Savigny,2002] The absorption cross section of O 3 in different temperatures and wavelengths in the Chappuis band (red arrows) used for O 3 retrievals. 6

7 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Retrieval Algorithm The Hartley bands in UV allow to retrieve O 3 between 35-65 km. Wavelengths 264, 267.5, 273.5, 283, 286, 288, 290 and 305 nm are chosen. [Rohen,2006] Burrows et al., [1999] 8 7

8 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Retrieval Algorithm Normalization step: reduce impact of ground albedo and cloud on O 3 retrieval. Reference tangent heights: Combination of the Chappuis bands wavelengths: Combination of the Hartley and Chappuis bands wavelengths: employ the retrieval vectors Wavelengths (nm)264 267.5 273.5 283 286 288 290 305 525 602 675 TH start (km) TH ref (km) 52 52 52 45 45 45 45 35 9 9 9 71 71 71 68 65 65 61 55 41 41 41 8

9 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Retrieval Algorithm Numerical retrieval step: nonlinear Newtonian iteration optimal estimation [Rodger, 1976] SCIATRAN V 2.2 radiative transfer model [Rozanov et al., 2007] using Discrete Ordinate Method (DOM) [Chandrasekhar, 1950] SCIATRAN set up Aerosol : none Ground albedo : 0.3 (for general cases) Weighting function : single scattering Cloud model : Mie phase function 9

10 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Use linear approximation to estimate the error. 1010

11 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Error Estimation + : S = I 0 at 600 nm ◆ : S = Normalized triple + : S = I 0 at 600 nm ◆ : S = Normalized triple 1

12 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Error Estimation < 0, always < 0 + - > 0 Can we use linear approximation to predict the error? 1212

13 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Sensitivity studies Weighting functions of cloud-free 1313

14 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Sensitivity studies Weighting functions of cloud-free and cloudy atmosphere 1414

15 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Sensitivity studies Different weighting functions of cloud-free and cloudy atmosphere 264 nm273 nm 286 nm 290 nm 305 nm CHAPPUIS 1515

16 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen The retrieval ozone profiles from synthetic data The combined Hartley, Huggins and Chappuis bands O 3 profiles in from modeled calculation in cloud-free and cloudy atmosphere. Cloud parameters: cloud height 4-7 km, τ =20, r e =10  m, SZA = 30 o, SAA = 30 o 1616

17 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Sensitivity studies Cloud types : (cloud level and cloud optical thickness) Cirrus Cirrostratus Deep convection Altocumulus Altostratus Nimbostratus Cumulus Stratocumulus Stratus 0 - 3.6 3.6 – 23 23 – 379 High cloud (6-15 km)Middle cloud (2-7 km)Low cloud (1-3 km)  The cloud reflectance at 630 nm as function of . [Roebeling et al., 2005] The relative O 3 error for low cloud, r e = 10  m, and SZA = SAA = 30 o (SZA ~ 22 o and SAA ~ 70 o at TH = 25 km ) The relative O 3 error for middle cloud, r e =10  m and SZA = SAA = 30 o (SZA ~ 22 o and SAA ~ 70 o at TH = 25 km ) The relative O3 error for high cloud, re=10  m and SZA = SAA = 30 o (SZA ~ 22 o and SAA ~ 70 o at TH = 25 km ) 1717

18 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen a) different cloud altitudes The relative error of O 3 retrieval profiles for cloud parameters: τ = 10, r e = 10  m and SZA = SAA = 30 o. Sensitivity studies Geometrical cloud thickness 1818

19 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Sensitivity studies Geometrical cloud thickness The relative error of O 3 retrieval profiles for cloud parameters: τ = 10, r e = 10  m and SZA = SAA = 30 o. b) cloud center 4.9 km c) cloud center 10.5 km 1919

20 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Sensitivity studies Cloud effective radius The reflection function of water clouds for different values of r e at τ = 30 and SZA = 45 o. [Kokhanovsky, 2001] 1 0. 8 0.60.6 0.40.4 0.20.2 0 0.50.5 11.51.5 2.02.0 2.52.5 The relative error of O 3 retrieval profiles for different r e. Cloud parameters: τ = 10, 2-7 km and SZA = SAA = 30 o 2020

21 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Sensitivity studies Surface ground albedo The relative error of O 3 retrieval profiles for different ground albedo. Cloud parameter: τ = 10, r e = 10  m, SZA = SAA= 30 o and cloud altitude 2-7 km. 2121

22 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Sensitivity studies Solar zenith angle Solar azimuth angle The relative error of O 3 retrieval profiles for different SZAs. Cloud parameter: τ = 10, r e = 10  m, SAA = 30 o and cloud altitude 2-7 km. 2 The relative error of O 3 retrieval profiles for different SAAs. Cloud parameter: τ = 10, r e = 10  m, SZA = 30 o and cloud altitude 2-7 km.

23 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Sensitivity studies Viewing angles represent for SCIAMACHY (SZA ≈ 62, SAA ≈ 33 at TH 25 km) (SZA ≈ 30, SAA ≈ 55 at TH 25 km) (SZA ≈ 40, SAA ≈ 130 at TH 25 km) (SZA ≈ 70, SAA ≈ 160 at TH 25 km) (SZA ≈ 78, SAA ≈ 175 at TH 25 km) Cloud parameter: τ = 10, r e = 10  m and cloud altitude 2-7 km. 2323

24 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Sensitivity studies Overview of cloud sensitivity to O 3 The optical cloud thickness (left) and cloud effective radius (right) from SCIAMACHY data, using SACURA, 19 September 2007. [http://www.iup.physik.uni-bremen.de/~sciaproc/SACURA] Frequent cloud :  < 10, r e = 20  m 2424

25 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Sensitivity studies Overview of cloud sensitivity to O 3 for frequent cloud Altitude (km) 15 km 20 km 30 km 40 km 50 km 60 km 15 km 20 km 30 km 40 km 50 km 60 km SZA = 50 o, SAA = 32 o (SZA ~ 30 o, SAA = 55 o ) * SZA = 85 o, SAA = 22 o (SZA = 62 o, SAA = 33 o ) * SZA = 68 o, SAA = 157 o (SZA = 78 o, SAA = 175 o ) * < 3 % < 2.5 % < 2 % < 0.5 % < 0.1 % < 0.1 % < 3 % < 2.5 % < 2 % < 0.5 % < 0.1 % < 0.1 % < 5 % < 5 % < 2.5 % < 0.5 % < 0.1 % < 0.1 % < 5 % < 5 % < 2.5 % < 0.5 % < 0.1 % < 0.1 % < 10 % < 7 % < 3 % < 1 % < 0.5 % < 0.1 % < 10 % < 7 % < 3 % < 1 % < 0.5 % < 0.1 % * = at TH 25 km 2525

26 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Low bias error ( ε = - ) High bias error ( ε = + ) 2626 Comparison results with the error estimation

27 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen * exact x approximation * exact x approximation ~ 70% ~ 40% Triplet 600 nm 2727

28 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen * exact x approximation * exact x approximation Triplet 600 nm 2828

29 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Conclusions The combined Chappuis and Hartley band retrieval allows us to obtain the O 3 profiles from the lower stratosphere to lower mesosphere. The O 3 retrievals are sensitive to clouds in the Chappuis bands, between 15 -25 km sensitive to cloud parameters τ, high cloud and viewing angles not much sensitive to cloud parameters: r e. The effect of neglecting clouds in the retrievals is less than 10 % at all altitudes for frequent clouds. Linear approximation can not apply to estimate the O3 retrieval error from clouds. 2929

30 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Future activities Test, how clouds sensitivity to ozone retrieval depends on SZA and SAA on TH references. 3030

31 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen THE END…. ……..Thank you ……..Thank you

32 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Retrieval Algorithm 8 In linear approximation, limb radiance corresponding to the perturbed ozone profile can be written:

33 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Comparison results with the error estimation Low bias error High bias error TH 2626

34 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Comparison results with the error estimation 1919 Low bias error High bias error TH

35 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen 1919 Low bias error High bias error

36 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen 1919

37 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Sensitivity studies Solar azimuth angle 1717 Cloud parameter: τ = 10, r e = 10  m and cloud altitude 2-7 km. a) viewing angles represent for SCIAMACHY b) viewing angles represent for OSIRIS

38 Envisat Symposium, April 23 – 27, 2007, Montreux thiranan@iup.physik.uni- bremen.de SADDU Meeting, 16-17 June 2008, IUP-Bremen Low bias error High bias error Low bias error High bias error 2626 Comparison results with the error estimation

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