Multiangle cloud remote sensing from

Transcription

1 Multiangle cloud remote sensing from POLDER3/PARASOL Cloud phase, optical thickness and albedo F. Parol, J. Riedi, S. Zeng, C. Vanbauce, N. Ferlay, F. Thieuleux, L.C. Labonnote and C. Cornet Laboratoire d'optique Atmosphérique, Université des Sciences et Technologies de Lille 1/27

2 Instrumental Background CNES/LOA instrument, Parasol launched Dec ~ 705 km polar orbits, ascending (13:30 a.m.) Data available from March 2005 to Jan 2010 within A-TRAIN and more Sensor Characteristics 10 spectral bands ranging from to µm 3 polarised channels Wide FOV CCD Camera with 1800 km swath width +/- 43 degrees cross track +/- 51degrees along track Multidirectionnal observations (up to 16 directions) Spatial resolution : 6x7 km No onboard calibration system - Inflight vicarious calibration : 2-3% absolute calibration accuracy 1% interband 0.1% interpixel over clouds 2/27

3 ERB, WV and Clouds Level 2 processing scheme Level 1 georeferenced data Int. Sinusoidal grid 6km x 6km Gazeous absorption correction Clear sky only Cloud detection Water vapor content Cloud phase Ice only Cloud Optical Thickness and spectral albedo SW albedo integration Microphysical index from polarisation Rayleigh and Oxygen cloud pressure Level 2 gridded product Int. Sinusoidal 20km x 20km Apparent pressure determination 3/27

4 Multiangle polarisation measurements and Cloud Phase Liquid Ice 4/27

5 MODIS/Aqua and PARASOL Observation of Clouds and Aerosols Properties MODIS Sci. Team Meeting Oct Multiangle polarisation measurements and Cloud Phase Cloud phase at 20x20 km resolution Liquid, Ice, Mixed, Unknow with individual quality index within each. 5/30

6 MODIS/Aqua and PARASOL Observation of Clouds and Aerosols Properties MODIS Sci. Team Meeting Oct Multiangle multispectral measurements Cloud optical thickness is retrieved under up to 16 directions Directional product provided at = 670nm (land) and 865 nm (ocean) 6/30

7 MODIS/Aqua and PARASOL Observation of Clouds and Aerosols Properties MODIS Sci. Team Meeting Oct Multiangle multispectral measurements Cloud spherical albedo is retrieved under up to 16 directions Directional product provided at = 670nm (land) and 865 nm (ocean) 7/30

8 Multiangle multispectral measurements λ = 443 nm nm 3 Spectral λ = 670 nm nm Cloud Albedo λ = 865 nm nm SW CLOUD ALBEDO 8/27

9 Analysis of cloud phase against MODIS and CALIOP 9/27

10 Cloud phase as seen by POLDER, MODIS & CALIOP Level 2 official data POLDER MODIS CALIOP PM dataset: (Level 2 of MODIS & POLDER data ) resolution : 20 x 20km2 sinusoidal grid MODIS averaged over POLDER pixel CALTRACK dataset: (Level 2 of MODIS, POLDER & CALIOP data ) resolution : 5km available through ICARE Data & Services Center lille1.fr Period: From 12/2007 to 11/ /27

11 MODIS / POLDER global match & mismatch Data: PM dataset, 12/ /2008, [90 S 90 N] 11/27

12 Geographical Distributions of Phase Frequency 4/10 Data: PM dataset, 12/ /2008, [90 S 90 N] 12/27

13 5/10 View zenith angle analysis of Phase detection Data: PM dataset, 12/ /2008, [90 S 90 N] CALIOP SAMPLING LOCATION 13/27

14 POLDER/MODIS phase in CALIOP space Data: CALTRACK dataset, 12/ /2008, [90 S 90 N] 14/27

15 POLDER/MODIS vs CALIOP phase product Data: CALTRACK dataset, 12/ /2008, [90 S 90 N] 15/27

16 Sensitivity to thin cirrus 16/27

17 Analysis of cloud optical thickness/albedo POLDER / MODIS 17/27

18 Measured reflectance (a1) SZA = deg (b1) SZA = deg 0.7 Measured Reflectance Measured Reflectance Retrieved albedo should be independant of viewing geometry Viewing Zenith Angle (deg) Viewing Zenith Angle (deg) Retrieved «directionnal» albedo (a2) SZA = deg (b2) SZA = deg 0.7 "Directional" Albedo 0.7 "Directional" Albedo Viewing Zenith Angle (deg) Retrieved «average» albedo Albedo RMS of : 0.8 (a3) SZA = deg (b3) SZA = deg 0.7 Averaged Albedo 0.6 Averaged Albedo Red : clouds Green : clear sky land Blue : clear sky ocean Viewing Zenith Angle (deg) Plots here for 2 sun elevations, as a function of view zenith angle for clouds in clear sky Viewing Zenith Angle (deg) Viewing Zenith Angle (deg) 18/27

19 Testing cloud models from multiangle observation 19/27

20 Testing cloud models from multiangle observation Baran & Labonnote (2001) 20/27

21 From Zhang et al, 2009 (ACP) 21/27

22 From Zhang et al, 2009 (ACP) 22/27

23 POLDER vs MODIS Optical thickness for different phase categories 23/27

24 POLDER vs MODIS Scaled Optical thickness for different phase categories 24/27

25 Optical thickness and scaled optical thickness zonal variation 25/27

26 View zenith angle analysis MODIS POLDER 26/27

27 Summary POLDER phase product provides a reliable information on thermodynamic phase independant of cloud temperature and particle size In conjunction, POLDER and MODIS can be used to create a reference cloud phase dataset for benchmark studies of models or other sensors POLDER multiangle observations provide a unique way to constrain cloud models (micro and macro physics) and get «less biased» optical thickness/albedo Comparing scaled optical thickness (or albedo) can make our life easier in a first stage for this GEWEX exercise 27/27