1. SATELLITE OBSERVATIONS OF ATMOSPHERIC CHEMISTRY Daniel J. Jacob

2. OBSERVATION BY SOLAR OCCULTATION (UV to near-IR) EARTH “satellite sunrise” Tangent point; retrieve vertical profile of concentrations Recent extensions to lunar and stellar occultation Examples: SAGE, GOMOS

3. OBSERVATION BY THERMAL EMISSION (IR,  wave) EARTH SURFACE I (T o ) Absorbing gas or aerosol ToTo T1T1  I (T 1 ) LIMB VIEW NADIR VIEW Examples: MLS, MOPITT, MIPAS, TES, HRDLS

4. OBSERVATION BY SOLAR BACKSCATTER (UV to near-IR) absorption wavelength   Slant optical depth EARTH SURFACE Scattering by Earth surface and by atmosphere Backscattered intensity I B “Slant column” Examples: TOMS, GOME, SCIAMACHY, OMI

5. LIDAR MEASUREMENTS EARTH SURFACE backscatter by atmosphere Laser pulse Examples: LITE, CALYPSO

6. MOST OBSERVATIONS OF ATMOSPHERIC COMPOSITION FROM SPACE HAVE BEEN FOR THE STRATOSPHERE Tropopause Stratopause Observation of troposphere is far more difficult because of clouds particles (dust) water vapor continuum strat ozone layer Stratosphere Troposphere Ozone layer Mesosphere

7. 2002 2002 2004 2004 2004 2004 2004 PRESENT AND FUTURE SATELLITE MEASUREMENTS FOR TROPOSPHERIC CHEMISTRY

8. ATMOSPHERIC CHEMISTRY MODELS AND SATELLITE OBSERVATIONS: THE ODD COUPLE SATELLITE SPECTRA “L1 DATA” ATMOSPHERIC CONCENTRATIONS “L2 DATA” RETRIEVAL A PRIORI INFORMATION vertical gradient, concentration range, correlations… SCIENTIFIC ANALYSIS “L4 DATA” CLIMATOLOGICAL IN SITU OBSERVATIONS ATMOSPHERIC CHEMISTRY MODELS EVALUATION ASSIMILATION INCREASED KNOWELDGE INCEST?

9. GEOS-CHEM global model of tropospheric chemistry (www-as.harvard.edu/chemistry/trop/geos) Driven by NASA GEOS assimilated meteorological data, 1988-2001 1 o x1.25 o - 4 o x5 o horizontal resolution, 20-48 layers in vertical Simulation of tropospheric ozone-NO x -hydrocarbon chemistry includes ~80 interacting species

10. THE GOME SATELLITE INSTRUMENT Nadir-viewing solar backscatter instrument (237-794 nm) Low-elevation polar sun- synchronous orbit, 10:30 a.m. observation time Field of view 320x40 km 2, three cross-track scenes Complete global coverage in 3 days

11. USE GOME MEASUREMENTS OF NO 2 AND HCHO COLUMNS TO MAP NO x AND VOC EMISSIONS Emission NO h (420 nm) O 3, RO 2 NO 2 HNO 3 1 day NITROGEN OXIDES (NO x )VOLATILE ORGANIC CARBON (VOC) Emission VOC OH HCHO h (340 nm) hours CO hours BOUNDARY LAYER ~ 2 km Tropospheric NO 2 column ~ E NOx Tropospheric HCHO column ~ E VOC Deposition GOME

12. AIR MASS FACTOR (AMF) CONVERTS SLANT COLUMN  S TO VERTICAL COLUMN  “Geometric AMF” (AMF G ) for non-scattering atmosphere: EARTH SURFACE 

13. IN SCATTERING ATMOSPHERE, AMF DEPENDS ON SHAPE OF VERTICAL PROFILE (FOR WHICH GOME PROVIDES NO INFORMATION) Observations Model SOS (southeast U.S., Jul 1995) NARE (N. Atlantic, Sept 1997) Palmer et al. [2001]

14. CALCULATE AMF FOR EVERY GOME SCENE USING LOCAL SHAPE FACTORS FROM GEOS-CHEM Geometric AMF GOME efficiency = f (sun angle, albedo, cloud…) RADIATIVE TRANSFER MODEL Vertical concentration profile shape factor ATMOSPHERIC CHEMISTRY MODEL (GEOS-CHEM) Vertical column = Slant column AMF From GOME From model

15. GOME sensitivity ILLUSTRATIVE PROFILE OVER TENNESSEE HCHO mixing ratio profile (GEOS-CHEM) what GOME sees AMF G = 2.08 actual AMF = 0.71

16. SLANT COLUMNS OF NO 2 FROM GOME Dominant stratospheric contribution (NO 2 produced from N 2 O oxidation) Also see tropospheric hot spots (fossil fuel and biomass burning) Martin et al. [2002] Remove stratospheric column and instrument artifacts using data over Pacific

17. SLANT COLUMNS OF TROPOSPHERIC NO 2 FROM GOME 1996 Martin et al. [2002]

18. GOME RETRIEVAL OF TROPOSPHERIC NO 2 vs. GEOS-CHEM SIMULATION (July 1996) Martin et al. [2002] GEIA emissions scaled to 1996

19. PROPAGATION OF ERRORS IN NO 2 RETRIEVAL (errors  in 10 15 molecules cm -2 ) GOME SPECTRUM (423-451 nm) SLANT NO 2 COLUMN TROPOSPHERIC SLANT NO 2 COLUMN TROPOSPHERIC NO 2 COLUMN Fit spectrum Remove stratospheric contribution, diffuser plate artifact Use Central Pacific GOME data with: HALOE to test strat zonal invariance PEM-Tropics, GEOS-CHEM 3-D model to treat tropospheric residual Apply AMF to convert slant column to vertical column Use radiative transfer model with: local vertical shape factors from GEOS-CHEM local cloud information from CRAG          Martin et al. [2002]

20. CAN WE USE GOME TO ESTIMATE NO x EMISSIONS? TEST IN U.S. WHERE GOOD A PRIORI EXISTS Comparison of GOME retrieval (July 1996) to GEOS-CHEM model fields using EPA emission inventory for NO x GOME GEOS-CHEM (EPA emissions) BIAS = +3% R = 0.79 Martin et al. [2002] R = 0.78 Bias = +18%

21. FORMALDEHYDE COLUMNS FROM GOME: July 1996 means BIOGENIC ISOPRENE IS THE MAIN SOURCE OF HCHO IN U.S. IN SUMMER Palmer et al. [2001] GEIA isoprene emissions R = 0.83 Bias 14% Precision: 4x10 15 cm -2

22. SLANT COLUMNS OF HCHO FROM GOME High values over southeast U.S. are due to biogenic isoprene emission Palmer et al. [2002]Note “isoprene volcano” over the Ozarks

23. DEPENDENCE OF GOME HCHO COLUMNS OVER THE OZARKS ON SURFACE AIR TEMPERATURE Temperature dependence of isoprene emission (GEIA) Palmer et al. [2002]

24. MODEL AS INTERMEDIARY FOR GOME VALIDATION: EVALUATE AGAINST IN SITU SURFACE OBSERVATIONS Mean daytime HCHO surface observations Jun-Aug 1988-1998 Model (1996) vs. observations Palmer et al. [2002]

25. USING GOME HCHO COLUMNS TO MAP ISOPRENE EMISSIONS isoprene HCHO hours OH h, OH hours Displacement/smearing length scale 10-100 km

26. GEOS-CHEM RELATIONSHIP BETWEEN HCHO COLUMNS AND ISOPRENE EMISSIONS IN N AMERICA Use relationship to map isoprene emissions from GOME observations Palmer et al. [2002] GEOS-CHEM July 1996 NWNE SESW Isoprene emission [10 13 atomC cm -2 s -1 ] Model HCHO column [10 16 molec cm -2 ] model without isoprene

27. MAPPING OF ISOPRENE EMISSIONS FOR JULY 1996 BY SCALING OF GOME FORMALDEHYDE COLUMNS [Palmer et al., 2002] GEIA (IGAC inventory) BEIS2 (official EPA inventory) GOME COMPARE TO…

28. NEXT STEP: GLOBAL MAPPING OF VOC EMISSIONS FROM SPACE! T. Kurosu (SAO) and P. Palmer (Harvard) T. Kurosu (SAO) and P.I. Palmer (Harvard)