SATELLITE OBSERVATIONS OF ATMOSPHERIC CHEMISTRY Daniel J. Jacob

OBSERVATION BY SOLAR OCCULTATION “satellite sunrise” Tangent point; retrieve vertical profile of concentrations EARTH Recent extensions to lunar and stellar occultation

OBSERVATION BY THERMAL EMISSION (IR, mwave) NADIR VIEW LIMB VIEW elIl(T1) Absorbing gas or aerosol T1 Il(To) To EARTH SURFACE

OBSERVATION BY SOLAR BACKSCATTER (UV-IR) ATMOSPHERE Absorption/ scattering by Earth surface and atmosphere EARTH SURFACE

TOMS OBSERVATION OF ANTARCTIC OZONE HOLE Example of observation by solar backscatter

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 Mesosphere Stratosphere Ozone layer Troposphere

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

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

GEOS-CHEM global model of tropospheric chemistry (www-as. harvard GEOS-CHEM global model of tropospheric chemistry (www-as.harvard.edu/chemistry/trop/geos) Driven by NASA GEOS assimilated meteorological data, 1988-2001 1ox1o- 4ox5o horizontal resolution, 20-48 layers in vertical Simulation of tropospheric ozone-NOx-hydrocarbon chemistry includes ~80 interacting species

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 km2, three cross-track scenes Complete global coverage in 3 days

USE GOME MEASUREMENTS OF NO2 AND HCHO COLUMNS TO MAP NOxAND VOC EMISSIONS Tropospheric NO2 column ~ ENOx Tropospheric HCHO column ~ EVOC ~ 2 km hn (420 nm) BOUNDARY LAYER hn (340 nm) NO2 NO HCHO CO OH hours O3, RO2 hours VOC 1 day HNO3 Emission Deposition Emission NITROGEN OXIDES (NOx) VOLATILE ORGANIC CARBON (VOC)

COLUMN MEASUREMENT OF AN ABSORBING GAS USING SOLAR BACKSCATTER absorption EARTH SURFACE Scattering by Earth surface and by atmosphere ATMOSPHERE Backscattered intensity IB l1 l2 wavelength Slant optical depth “Slant column”

SLANT COLUMNS OF HCHO FROM GOME High values over southeast U. S SLANT COLUMNS OF HCHO FROM GOME High values over southeast U.S. are due to biogenic isoprene emission Palmer et al. [2002]

SLANT COLUMNS OF NO2 FROM GOME Dominant stratospheric contribution (NO2 produced from N2O oxidation) Also see tropospheric hot spots (fossil fuel and biomass burning) Remove stratospheric column and instrument artifacts using data over Pacific Martin et al. [2002]

SLANT COLUMNS OF TROPOSPHERIC NO2 FROM GOME 1996 Martin et al. [2002]

AIR MASS FACTOR (AMF) CONVERTS SLANT COLUMN WS TO VERTICAL COLUMN W “Geometric AMF” (AMFG) for non-scattering atmosphere: q EARTH SURFACE

IN SCATTERING ATMOSPHERE, AMF DEPENDS ON SHAPE OF VERTICAL PROFILE (FOR WHICH GOME PROVIDES NO INFORMATION) GOME sensitivity ILLUSTRATIVE PROFILE OVER TENNESSEE HCHO mixing ratio profile (GEOS-CHEM) what GOME sees AMFG = 2.08 actual AMF = 0.71

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

COMPARE MODEL VERTICAL PROFILES OF HCHO TO (THE FEW COMPARE MODEL VERTICAL PROFILES OF HCHO TO (THE FEW!) AVAILABLE AIRCRAFT OBSERVATIONS SOS (southeast U.S., Jul 1995) NARE (N. Atlantic, Sept 1997) Observations Model Palmer et al. [2001]

DIAGNOSE MODEL CONTAMINATION OF RETRIEVAL BY CORRELATING AMF WITH VERTICAL COLUMN Negative correlation implies that AMF conversion to vertical columns will modify the slant column patterns to better fit the model Martin et al. [2002]

PROPAGATION OF ERRORS IN NO2 RETRIEVAL (errors e in 1015 molecules cm-2) GOME SPECTRUM (423-451 nm) SLANT NO2 COLUMN TROPOSPHERIC SLANT NO2 COLUMN TROPOSPHERIC NO2 COLUMN Fit spectrum e1 = 0.8 Use Central Pacific GOME data with: HALOE to test strat zonal invariance PEM-Tropics, GEOS-CHEM 3-D model to treat tropospheric residual Remove stratospheric contribution, diffuser plate artifact e2 = 0.4 Use radiative transfer model with: local vertical shape factors from GEOS-CHEM local cloud information from CRAG Apply AMF to convert slant column to vertical column e3 = 0.5-3.2 Martin et al. [2002]

CAN WE USE GOME TO ESTIMATE NOx EMISSIONS. TEST IN U. S CAN WE USE GOME TO ESTIMATE NOx 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 NOx GOME GEOS-CHEM (EPA emissions) BIAS = +3% R = 0.79 R = 0.78 Bias = +18% Martin et al. [2002]

GOME RETRIEVAL OF TROPOSPHERIC NO2 vs. GEOS-CHEM SIMULATION (July 1996) Martin et al. [2002] GEIA emissions scaled to 1996

FORMALDEHYDE COLUMNS FROM GOME: July 1996 means Palmer et al. [2001] BIOGENIC ISOPRENE IS THE MAIN SOURCE OF HCHO IN U.S. IN SUMMER GEIA isoprene emissions R = 0.83 Bias 14% Precision: 4x1015 cm-2

Mean daytime HCHO surface observations 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]

GOME DETECTS THE ISOPRENE “VOLCANO” IN THE OZARKS Palmer et al. [2002]

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

YIELD OF HCHO FROM ISOPRENE OXIDATION OH ~1 hour O2 OO. OH days NO NO2 GEOS-CHEM mechanism + HCHO + HO2 O methylvinylketone Palmer et al. [2002]

Model HCHO column [1016 molec cm-2] model without isoprene GEOS-CHEM RELATIONSHIP BETWEEN HCHO COLUMNS AND ISOPRENE EMISSIONS IN N AMERICA Use relationship to map isoprene emissions from GOME observations NW NE GEOS-CHEM July 1996 Model HCHO column [1016 molec cm-2] SW SE model without isoprene Palmer et al. [2002] Isoprene emission [1013 atomC cm-2 s-1]

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

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