28/1/08Dr. J.J. Remedios, ERCA Space 2 1 Observations of tropospheric chemistry from space I J.J. Remedios EOS-SRC, Physics and Astronomy, University of Leicester, U.K.

28/1/08Dr. J.J. Remedios, ERCA Space 2 2 Themes of Lecture Part I: Introduction to observing tropospheric chemistry  Important parameters for tropospheric chemistry  Spectroscopy: scattered sunlight and thermal infra-red emission  Observing the Earth: nadir vs limb  Current instruments Part II: Examples of instruments and observations  GOME/SCIAMACHY/OMI: NO 2, HCHO, Glyoxal, BrO  MOPITT: CO  MIPAS AND ACE: Organic compounds such as PAN, acetone, formic acid, methanol, hydrocarbons

28/1/08Dr. J.J. Remedios, ERCA Space 2 3 SOME KEY QUESTIONS BEING ADDRESSED BY SPACE OBSERVATIONS OF TROPOSPHERIC COMPOSITION AND CHEMISTRY PART I

28/1/08Dr. J.J. Remedios, ERCA Space 2 4 SCIENCE IMPERATIVES: CH 4 : CLIMATE AND OH (SCIAMACHY) Images courtesy of MOPITT team Frankenburg et al. Heidelburg, KNMI Science paper

28/1/08Dr. J.J. Remedios, ERCA Space 2 5 SCIENCE AND POLICY IMPERATIVES: AIR QUALITY NO 2 (SCIAMACHY) SCIAMACHY tropospheric NO 2 columns, annual average: Heidelburg Richter et al., Nature, 2005: NO 2 over China

28/1/08Dr. J.J. Remedios, ERCA Space 2 6 MODIS Fire Map MODIS Fire Map: 9 th - 19 th July, 2004

28/1/08Dr. J.J. Remedios, ERCA Space 2 7 MOPITT CO July 2001 “Surface” Level Monthly mean CO observed from daytime retrievals of CO (“surface” retrieved level) – figure from N. Richards, PhD thesis, Leicester, We get similar result for July 2004, showing that African biomass burning is a “climatological” feature

28/1/08Dr. J.J. Remedios, ERCA Space 2 8 OMI NO 2 : JULY AATSR LST: July PUBLIC IMPACT AND PUBLIC KNOWLEDGE

28/1/08Dr. J.J. Remedios, ERCA Space 2 9 Some major Atmospheric Composition Instruments ERS-1/2 (1990s)  GOME (T)  ATSR-1/2 (T)  MWR (T H2O) ENVISAT (2002)  MIPAS (UT)  SCIAMACHY (T)  GOMOS  AATSR (T)  MERIS (T H2O)  MWR (T H2O) NASA MISSIONS (1999, 2004)  MOPITT (T) ON EOS-TERRA  AIRS (T) ON EOS-AQUA  TES (T), OMI (T), MLS (UT) ON EOS-AURA METOP (2007)  IASI (T), GOME-2 (T) T=Troposphere UT = Upper troposphere ATSR series only produces aerosols currently as do many of the others

28/1/08Dr. J.J. Remedios, ERCA Space 2 10 Parameters for tropospheric chemistry Essentially we want to observe: gases which are direct pollutants, gases which control the lifetimes of pollutant and greenhouse gases, gases which are important in climate-chemistry interactions Aerosols and clouds (not covered in these lectures) Hence: Ozone and its precursors Hydroxyl radical: OH and its sources and sinks NOx (NO,NO 2 ) and NOy (HNO 3, PAN, organic nitrates) VOCs (formaldehyde, glyoxal, hydrocarbons such as ethane, ethyne, PAN, acetone, methanol…) Halogens Sulphur compounds

28/1/08Dr. J.J. Remedios, ERCA Space 2 11 Influences on tropospheric chemistry Natural sources and sinks  Vegetation  Oceans  Volcanoes  Snow Sunlight and photochemistry Clouds Anthropogenic emissions  Industry  Transport  Agricultural practices especially burning and intensive cultivation. Implication: we wish to observe a large number of species on a regional basis throughout the globe

28/1/08Dr. J.J. Remedios, ERCA Space 2 12 Parameters for tropospheric chemistry HOW DO WE OBSERVE THESE GASES IN THE TROPOSPHERE? Ultra-violet/visible radiation/near infra-red – O 3 and reactive gases [UV/VIS/NIR] Shortwave infra-red radiation (SWIR) – CO and climate gases Thermal infra-red radiation (TIR OR MIR) – O 3, CO, climate and reactive gases

28/1/08Dr. J.J. Remedios, ERCA Space 2 13 SOURCES OF SIGNALS FOR PASSIVE INSTRUMENTS: SOLAR RADIATION AND TERRESTRIAL RADIATION

28/1/08Dr. J.J. Remedios, ERCA Space 2 14 SOLAR UV-VIS-SWIR AND TERRESTRIAL THERMAL I/R RADIATION

28/1/08Dr. J.J. Remedios, ERCA Space 2 15 THE PLANCK FUNCTION IS AT THE HEART OF OBSERVATIONS FROM SPACE! SO ALSO IS SPECTROSCOPY!!

28/1/08Dr. J.J. Remedios, ERCA Space 2 16 Planck’s Radiation Law – Earth and Sun SUNEARTH U/V VIS SWIR TIR FIRMICRO WAVE

28/1/08Dr. J.J. Remedios, ERCA Space 2 17 SCIAMACHY SPECTRA – SIMULATIONS I

28/1/08Dr. J.J. Remedios, ERCA Space 2 18 SCIAMACHY SPECTRA – SIMULATIONS II

28/1/08Dr. J.J. Remedios, ERCA Space 2 19 EXAMPLE FIT TO WEAK SPECTRAL FEATURES: SCIAMACHY CO Can fit to very weak absorbers!! [Frankenberg et al, 2005]

28/1/08Dr. J.J. Remedios, ERCA Space 2 20 Infra-red emission spectrum to space [Nadir signal for an i/r instrument] 10  m 4  m20  m 5  m 12  m window 8  m window CO 2 O3O3 N 2 O, CH 4 H2OH2O

28/1/08Dr. J.J. Remedios, ERCA Space 2 21 NADIR INFRA-RED TRANSMISSION TO SPACE Clerbaux et al., ACP, 2003

28/1/08Dr. J.J. Remedios, ERCA Space 2 22 INFRA-RED LIMB SPECTRUM LONGER PATHLENGTH SO MORE SENSITIVE The total spectral region (4.15 – 14.6μm) of MIPAS as measured at 18.7 km tangent altitude, this region is divided in 5 spectral intervals (A, AB, B, C, D); the large number of spectral emission lines demonstrates the enormous amount of information in the measurements; a considerable number of trace constituents can be detected as indicated. Fischer et al, ACPD, 2007

28/1/08Dr. J.J. Remedios, ERCA Space 2 23 INFRA-RED LIMB SPECTRUM EXAMPLE MIPAS SPECTRA I

28/1/08Dr. J.J. Remedios, ERCA Space 2 24 Example MIPAS SPECTRA II: CO 2

28/1/08Dr. J.J. Remedios, ERCA Space 2 25 Example MIPAS spectra III

28/1/08Dr. J.J. Remedios, ERCA Space 2 26 Instruments for tropospheric chemistry WHAT SORTS OF INSTRUMENT DO WE CURRENTLY USE? Nadir sounders – sensing throughout the troposphere at high spatial but low vertical (mostly) resolution Limb sounders – mid- to upper troposphere at high vertical resolution but low spatial resolution Low Earth Orbit (LEO) instruments – overwhelming configuration Geostationary (GEO) instruments – only just starting to be used for trace gases other than water vapour. Spectrometers – the majority “High” resolution radiometers – e.g. MOPITT

28/1/08Dr. J.J. Remedios, ERCA Space 2 27 Spectroscopy Major gases dominate the spectrum Chemistry demands detection and analysis of very weak spectral features:  Instrument noise performance  Instrument stability and calibration  Spectral resolution It is incredible what modern spectroscopic systems can achieve!

28/1/08Dr. J.J. Remedios, ERCA Space 2 28 Nadir and Limb measurements [Illustrated for SCIAMACHY]

28/1/08Dr. J.J. Remedios, ERCA Space 2 29 CURRENT IMPORTANT NADIR SOUNDERS FOR TROPOSPHERIC CHEMISTRY INSTRUMENTSATELLITEORBITTYPE REGION MOPITTEOS-TERRALEOGAS CORRELATION RADIOMETRY I/R TESEOS-AURALEOFTS 1 I/R IASIMETOPLEOFTS 1 I/R GOME, GOME- 2 ERS-2, METOP LEOGRATING 2 UV/VISIBLE SCIAMACHYENVISATLEOGRATING 2 UV/VISIBLE/NIR 3 OMIEOS-AURALEOGRATING 2 UV/VISIBLE 1. Fourier Transform Spectrometer. 2. Grating Spectrometer. 3. Near infra-red.

28/1/08Dr. J.J. Remedios, ERCA Space 2 30 CURRENT IMPORTANT LIMB SOUNDERS FOR TROPOSPHERIC CHEMISTRY INSTRUMENTSATELLITEORBITTYPE REGION ACESCISATLEOFTS 1 I/R MIPASENVISATLEOFTS 1 I/R MLSEOS-AURALEOSPECTRO- RADIOMETER MICROWAVE 1. Fourier Transform Spectrometer. 2. Grating Spectrometer. 3. Near infra-red.

28/1/08Dr. J.J. Remedios, ERCA Space 2 31 Summary part I Tropospheric chemistry has some big impacts and space measurements are increasingly being used to investigate and monitor it. Spaceborne observations are currently passive instruments, i.e. using natural sources of radiation. Both Sun and Earth radiation (sources) are driven by the Planck function Chief technique is nadir sounding but limb sounding provides vertical resolution of the mid-to upper troposphere. Instruments are usually spectrometers or of equivalent “high” spectral resolution enabling measurements of many chemical species.