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SATELLITE REMOTE SENSING OF TERRESTRIAL CLOUDS Alexander A. Kokhanovsky

SATELLITE REMOTE SENSING OF TERRESTRIAL CLOUDS Alexander A. Kokhanovsky Institute of Remote Sensing, Bremen University P. O. Box 330440 Bremen, Germany alexk@iup.physik.uni-bremen.de. Hot issues in cloud research Optical properties of ice and mixed clouds

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SATELLITE REMOTE SENSING OF TERRESTRIAL CLOUDS Alexander A. Kokhanovsky

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  1. SATELLITE REMOTE SENSING OF TERRESTRIAL CLOUDS Alexander A. Kokhanovsky Institute of Remote Sensing, Bremen University P. O. Box 330440 Bremen, Germany alexk@iup.physik.uni-bremen.de

  2. Hot issues in cloud research Optical properties of ice and mixed clouds Absorption of solar radiation by clouds Gas-aerosol-cloud interactions 3-D effects in clouds Clouds and climate

  3. ENVISAT Start: 28.2.2002

  4. SCIAMACHY Instrument SCIAMACHY = SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY • Characteristics: • UV/Vis/NIR Spectrometer: 240 - 2380 nm • Spectral resolution: • 0.2 – 1.5 nm • 8000 spectral points • SCIAMACHY measures: • Reflected solar light (nadir) • Scattered solar light (limb) • Transmitted solar/moon light (occultation) • Solar Irradiance

  5. PARAMETERS to be retrieved: Cloud optical thickness /5-100/ Cloud top height /0.5-10km/ Cloud cover /0-1/ Cloud albedo/0.3-0.8/ Liquid water path /50-200 / Thermodynamic phase /ice, water or mixed clouds/ Average size of droplets/crystals

  6. The retrieval techniques 1: The look-up-table approach cloud surface

  7. 2: The semi-analytical approach

  8. Optical characteristics of clouds Trishchenko and Liu, 2001 Kokhanovsky, 2003 ISCCP data Surface observations Number of cases Optical thickness

  9. The physics behind the semi-analytical approach Sun Satellite 1 2

  10. The cloud optical thickness determination

  11. The accuracy of the semi-analytical asymptotic theory

  12. The accuracy of the semi-analytical asymptotic theory

  13. The accuracy of the semi-analytical asymptotic theory

  14. Image of Western Europe from Sea-viewing Wide Field of view Sensor 1-km spatial resolution 2001 10 11

  15. Retrieved cloud optical thickness distribution

  16. Retrieved cloud albedo distribution

  17. Frequency distribution: optical thickness

  18. Frequency distribution:spherical albedo

  19. Hurricane Erin grazes Bermuda A satellite photo of Hurricane Erin September 9, 2001 Posted: 11:04 PM EDT (0304 GMT) Hurricane Erin, 1-17 September, 2001 MIAMI, Florida (CNN) -- Hurricane Erin continued to gain strength Sunday but posed increasingly less threat to land as it strayed farther out in the Atlantic. The worst part of the storm, with maximum sustained winds of 195 km/h, passed to the northeast of Bermuda

  20. Hurricane optical thickness distribution

  21. Hurricane optical thickness distribution near its eye

  22. Hurricane optical thickness distribution in the eye

  23. 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 1.0 1.5 2.0 2.5 Other applications Experiment/Antarctic snow /, Grenfell et al., JGR, D,1994 Experiment/sea foam/, Frouin et al., JGR, C, 2001 measurements approximation spherical albedo wavelength, micrometers

  24. Cloud top height determination from a satellite The geometry of the problem

  25. Cloud top height determination from a satellite The accuracy of the forward model Nadir observation, solar zenith angle – 20 degrees Cloud optical thickness –20.

  26. Cloud top height determination from a satellite The accuracy of the forward model

  27. Cloud top height determination from a satellite The physical principle behind the retrieval

  28. Cloud geometrical thickness determination from a satellite Preliminary results !

  29. Table 1. Characteristics of selected space instruments, related to measurements of the backscattered light in the oxygen A-band (7550-7750 ). Instrument Platform Year Spectral interval, Spectral resolution, Spatial resolution, km2 GOME ERS-2 1995 5760-7940 3.3 40*320 SCIAMACHY ENVISAT 2002 6040-8050 4.8 30*60 MERIS ENVISAT 2002 7600 25 0.3*0.3 or 1.1*1.1 GLI ADEOS-II 2002 7630 80 0.25*0.25 and 1.0*1.0 POLDER ADEOS-II 2002 7633 7651 100 400 6.0*7.0

  30. Cloud top height determination from SCIAMACHY Typical SCIAMACHY spectra in the oxygen A-band

  31. Cloud top height determination from SCIAMACHY

  32. Cloud top height determination from SCIAMACHY

  33. Cloud top height determination from GOME data using oxygen A-band information as compared to ATSR-2 IR retrievals (ERS-2 satellite)

  34. Conclusions • Most of important cloud parameters can be retrieved using spectral top of atmosphere reflectance. • Cases of inhomogeneous clouds can bias retrieval results considerably. This should be clarified in future research. • The information on clouds obtained on a global and regional scale should enhance our studies of climate change, including anthropogenic influences on cloud microphysical and optical properties • and

  35. Clouds are important and

  36. Clouds are beautiful! Hurricane Erin, Sept 9th, 2001

  37. SCIAMACHY observes NLC SCIAMACHY Limb profile without NLCs SCIAMACHY Limb profile With NLCs

  38. Global detection of NLC with SCIAMACHY NLC Season 2002 NLC Season 2002/2003

  39. Noctilucent clouds Photos: Pekka Parviainen

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