1. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Remote Sensing I Atmospheric Microwave Remote Sensing Summer 2007 Björn-Martin Sinnhuber Room NW1 - U3215 Tel. 8958 bms@iup.physik.uni-bremen.de www.iup.uni-bremen.de/~bms

2. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Contents Chapter 1Introduction Chapter 2Electromagnetic Radiation Chapter 3Radiative Transfer through the Atmosphere Chapter 4Weighting Functions and Retrieval Techniques Chapter 5Atmospheric Microwave Remote Sensing: A short review of spectroscopy Chapter 6Atmospheric IR & UV/visible Remote Sensing Chapter 7Radar and Sea Ice Remote Sensing Chapter 8Remote Sensing of Ocean Colour

3. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Observations in Spitsbergen (79°N) Fourier Transform Infra-Red Spectrometer (FTIR)

4. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Fourier transformation Wavenumber [cm -1 ] Intensity

5. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Wellenlänge (  m) 13.0 10.0 8.0 Wellenlänge (  m) 9.0 8.7 wavelength (  m) 8.73 8.7 1146.0 1146.5 8.725 8.720 N2ON2O N2ON2O O3O3 O3O3 O3O3 O3O3 Each trace gas has ist own ‘fingerprint‘ in the spectrum

6. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Chapter 6 Atmospheric Infra-red and UV/visible Remote Sensing A short review of infra-red spectroscopy Atmospheric UV/visible remote sensing

7. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Molecular Vibrations

8. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Molecular Vibrations Cl H H Equilibrium distance Higher energy: H Cl squeezedstretched

9. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Harmonic Oscillator H Cl H H

10. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Harmonic Oscillator

11. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Harmonic Oscillator Energy levels:

12. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Spectrum of the Harmonic Oscillator Energy levels: Observed transitions (spectral lines): (independent of v, i.e. all at the same frequency!)

13. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 The Molecular Potential H2H2

14. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 The Morse Potential

15. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Vibrational Levels and Transitions Ignoring anharmonic effects:

16. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Rotational and Vibrational Levels

17. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Rotational and Vibrational Levels

18. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Rotational and Vibrational Transitions

19. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Rotational and Vibrational Transitions P branch

20. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Rotational and Vibrational Transitions R branch

21. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Rotational and Vibrational Transitions Q branch

22. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Rotational and Vibrational Levels

23. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Observed Spectrum of CO

24. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Observed HCN Spectrum at 715 cm -1 Q-branch!

25. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Polyatomic Molecules For a molecule with N atoms 3N degrees of freedom. Translation: 3 degrees of freedom Rotation: 3 degrees of freedom Vibration: 3N-6 degrees of freedom For a linear molecule only 2 rotational degrees of freedom, leaving 3N-5 vibrational degrees of freedom

26. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Example: H2O

27. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 H2O: Symmetric stretch mode

28. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 H2O: Bending mode

29. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 H2O: Asymmetric stretch mode

30. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Example: CO2

31. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Electronic Transitions: Example O 2

32. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Electronic Transitions Example: UV absorption of O 2

33. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Chapter 6 Atmospheric Infra-red and UV/visible Remote Sensing A short review of infra-red spectroscopy Atmospheric UV/visible remote sensing

34. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Example: Ozone Measurements by Dobson Instrument Quartz plates Adjustable wedge Fixed slits Prisms Detector: photomultiplier Org. photographic plate

35. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Principle of Wavelength Pairs (online - off-line) Cross secton  1 2 Known from measurements of solar spectrum Absorber column amount along effective light path

36. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Ozone Measurements by Dobson Instrument NameWL 1 [nm]WL 2 [nm] A305.5325.4 B308.8329.1 C311.45332.4 D317.6339.8 C’332.4453.6 Used wavelength pairs

37. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Differential Optical Absorption Spectroscopy (DOAS) remote sensing measurement of atmospheric trace gases in the atmosphere measurement is based on absorption spectroscopy in the UV and visible wavelength range to avoid problems with extinction by scattering or changes in the instrument throughput, only signals that vary rapidly with wavelength are analysed (thus the differential in DOAS) measurements are taken at moderate spectral resolution to identify and separate different species when using the sun or the moon as light source, very long light paths can be realised in the atmosphere which leads to very high sensitivity even longer light paths are obtained at twilight when using scattered light Courtesy of Andreas Richter, Uni Bremen

38. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Example: Absorber Cross Sections Courtesy of Andreas Richter, Uni Bremen

39. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 DOAS equation I The intensity measured at the instrument is the extraterrestrial intensity weakened by absorption, Rayleigh scattering and Mie scattering along the light path: absorption by all trace gases j extinction by Mie scattering extinction by Rayleigh scattering unattenuated intensity integral over light path scattering efficiency exponential from Lambert Beer’s law Courtesy of Andreas Richter, Uni Bremen

40. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 DOAS equation II if the absorption cross-sections do not vary along the light path, we can simplify the equation by introducing the slant column SC, which is the total amount of the absorber per unit area integrated along the light path through the atmosphere: Courtesy of Andreas Richter, Uni Bremen

41. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 DOAS equation III As Rayleigh and Mie scattering efficiency vary smoothly with wavelength, they can be approximated by low order polynomials. Also, the absorption cross-sections can be separated into a high (“differential”) and a low frequency part, the later of which can also be included in the polynomial: polynomial differential cross-section slant column Courtesy of Andreas Richter, Uni Bremen

42. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 DOAS equation IV Finally, the logarithm is taken and the scattering efficiency included in the polynomial. The result is a linear equation between the optical depth, a polynomial and the slant columns of the absorbers. by solving it at many wavelengths (least squares approximation), the slant columns of several absorbers can be determined simultaneously. polynomial (b p * are fitted) slant columns SC j are fitted absorption cross-sections (measured in the lab) intensity with absorption (the measurement result) intensity without or with less absorption (reference measurement) Courtesy of Andreas Richter, Uni Bremen

43. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Example of DOAS data analysis measurementoptical depth differential optical depth O3O3 H2OH2O NO 2 residual Ring Courtesy of Andreas Richter, Uni Bremen

44. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Example for satellite DOAS measurements Nitrogen dioxide (NO 2 ) and NO are key species in tropospheric ozone formation they also contribute to acid rain sources are mainly anthropogenic (combustion of fossil fuels) but biomass burning, soil emissions and lightning also contribute GOME and SCIAMACHY are satellite borne DOAS instruments observing the atmosphere in nadir data can be analysed for tropospheric NO 2 providing the first global maps of NO x pollution after 10 years of measurements, trends can also be observed 1996 - 2002 GOME annual changes in tropospheric NO 2 A. Richter et al., Increase in tropospheric nitrogen dioxide over China observed from space, Nature, 437 2005 Courtesy of Andreas Richter, Uni Bremen

45. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Satellite Observing Geometries Measured signal: Reflected and scattered sunlight Measured signal: Directly transmitted solar radiation Measured signal: Scattered solar radiation Courtesy of Christian von Savigny, Uni Bremen

46. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Examples: BUV (Backscatter Ultraviolet) instrument on Nimbus 4, 1970-1977 SBUV (Solar Backscatter Ultraviolet) instrument on Nimbus 7, operated from 1978 to 1990 SBUV/2 (Solar Backscatter Ultraviolet 2) instrument on the NOAA polar orbiter satellites: NOAA-11 (1989 -1994), NOAA-14 (in orbit)can measure ozone profiles as well as columns TOMS (Total Ozone Mapping Spectrometer) first on Nimbus 7, operated from 1978 to 1993. Then three subsequent versions: Meteor 3 (1991-1994), ADEOS (1997), Earth Probe (1996-). Measures total ozone columns. GOME (Global Ozone Monitoring Experiment) launched on ESA's ERS-2 satellite in 1995 employs a nadir-viewing BUV technique that measures radiances from 240 to 793 nm. Measures O 3 columns and profiles, as well as columns of NO 2, H 2 O, SO 2, BrO, OClO. SCIAMACHY (Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY) on Envisat is an improved GOME. Examples for UV/visible Nadir Sounders Courtesy of Christian von Savigny, Uni Bremen

47. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Example: Onion peel inversion of occultation observations Earth x1x1 x2x2 x3x3 x4x4 x5x5  (TH 1 )  (TH 2 )  (TH 3 )  (TH 4 )  (TH 5 ) x i : O 3 concentration at altitude z i y j : O 3 column density at tangent height TH j a 11 a 21 /2 a 22 a 32 /2 The matrix elements a ij correspond to geometrical path lengths through the layers Sun Retrieving Profiles from Occultation Measurements Courtesy of Christian von Savigny, Uni Bremen

48. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Example: Solar Occultation Instruments Examples: SAGE (Stratospheric Aerosol and Gas Experiment) Series provided constinuous observations since 1984 to date Latest instrument is SAGE III on a Russian Meteor-3M spacecraft HALOE (Halogen Occultation Experiment) on UARS (Upper Atmosphere Research Satellite) operated from 1991 until end of 2005, employing IR wavelengths POAM (Polar Ozone and Aerosol Measurement) series use UV-visible solar occultation to measure profiles of ozone, H 2 O, NO 2, aerosols GOMOS (Global Ozone Monitoring by Occultation of Stars) on Envisatwill performs UV-visible occultation using stars SCIAMACHY (Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY) on Envisat performs solar and lunar occultation measurements providing e.g., O 3, NO 2, and (nighttime) NO 3 profiles. Courtesy of Christian von Savigny, Uni Bremen

49. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Examples: SME (Solar Mesosphere Explorer) launched in 1981, carried the first ever limb scatter satellite instruments. Mesospheric O 3 profiles were retrieved using the Ultraviolet Spectrometer and stratospheric NO 2 profiles were retrieved using the Visible Spectrometer MSX satellite – launched in 1996, carried a suite of UV/visible sensors (UVISI) SOLSE (Shuttle Ozone Limb Sounding Experiment) flown on the Space Shuttle flight in 1997. Provided good ozone profiles with high vertical resolution down to the tropopause OSIRIS (Optical Spectrograph and Infrared Imager System) launched in 2001 on Odin satellite. Retrieval of vertical profiles of O 3, NO 2, OClO, BrO SCIAMACHY (Scanning Imaging Absorption SpectroMeter for Atmospheric CHartographY), launched on Envisat in 2002. Retrieval of vertical profiles of O 3, NO2, OClO, BrO and aerosols Example: UV/visible Limb Sounders Courtesy of Christian von Savigny, Uni Bremen

50. B.-M. Sinnhuber, Remote Sensing I, University of Bremen, Summer 2007 Satellite Observing Geometries II Observing GeometryProContra OccultationProfile retrieval possible; high accuracy due tostrong signal Poor geographical coverage: only possible for sunrise/sunset NadirNear global coverageOnly column densities LimbProfile information with near global coverage Complicated radiative transfer