Thomas P. Kurosu

An improved retrieval of tropospheric nitrogen dioxide from GOME

[1] We present a retrieval of tropospheric nitrogen dioxide (NO2) columns from the Global Ozone Monitoring Experiment (GOME) satellite instrument that improves in several ways over previous retrievals, especially in the accounting of Rayleigh and cloud scattering. Slant columns, which are directly fitted without low-pass filtering or spectral smoothing, are corrected for an artificial offset likely induced by spectral structure on the diffuser plate of the GOME instrument. The stratospheric column is determined from NO2 columns over the remote Pacific Ocean to minimize contamination from tropospheric NO2. The air mass factor (AMF) used to convert slant columns to vertical columns is calculated from the integral of the relative vertical NO2 distribution from a global 3-D model of tropospheric chemistry driven by assimilated meteorological data (Global Earth Observing System (GEOS)-CHEM), weighted by altitude-dependent scattering weights computed with a radiative transfer model (Linearized Discrete Ordinate Radiative Transfer), using local surface albedos determined from GOME observations at NO2 wavelengths. The AMF calculation accounts for cloud scattering using cloud fraction, cloud top pressure, and cloud optical thickness from a cloud retrieval algorithm (GOME Cloud Retrieval Algorithm). Over continental regions with high surface emissions, clouds decrease the AMF by 20– 30% relative to clear sky. GOME is almost twice as sensitive to tropospheric NO2 columns over ocean than over land. Comparison of the retrieved tropospheric NO2 columns for July 1996 with GEOS-CHEM values tests both the retrieval and the nitrogen oxide radical

Mapping isoprene emissions over North America using formaldehyde column observations from space

good simulation of both the GOME data (r 2 = 0.69, n = 756, bias = +11%) and the in situ summertimeHCHOmeasurementsoverNorthAmerica(r 2 =0.47,n=10,bias= � 3%).The GOMEobservationsshowhighvaluesoverregionsofknownhighisoprene emissions anda day-to-day variability that is consistent with the temperature dependence of isoprene emission. Isoprene emissions inferred from the GOME data are 20% less than GEIA on average over North America and twice those from the U.S. EPA Biogenic Emissions Inventory System (BEIS2) inventory. The GOME isoprene inventory when implemented in the GEOS-CHEM model provides a better simulation of the HCHO in situ measurements thaneitherGEIAorBEIS2(r 2 =0.71,n=10,bias= � 10%). INDEXTERMS:0312Atmospheric Composition and Structure: Air/sea constituent fluxes (3339, 4504); 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305);0365 Atmospheric Composition and Structure: Troposphere— composition and chemistry; 0394 Atmospheric Composition and Structure: Instruments and techniques; 0399 Atmospheric Composition and Structure: General or miscellaneous; KEYWORDS: Isoprene, Formaldehyde, GOME, biogenic emissions, satellite instrument, volatile organic compounds

Quantifying the seasonal and interannual variability of North American isoprene emissions using satellite observations of the formaldehyde column

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, D12315, doi:10.1029/2005JD006689, 2006 Quantifying the seasonal and interannual variability of North American isoprene emissions using satellite observations of the formaldehyde column Paul I. Palmer, 1,2 Dorian S. Abbot, 1 Tzung-May Fu, 1 Daniel J. Jacob, 1 Kelly Chance, 3 Thomas P. Kurosu, 3 Alex Guenther, 4 Christine Wiedinmyer, 4 Jenny C. Stanton, 5 Michael J. Pilling, 5 Shelley N. Pressley, 6 Brian Lamb, 6 and Anne Louise Sumner 7 Received 20 September 2005; revised 19 December 2005; accepted 14 February 2006; published 27 June 2006. [ 1 ] Quantifying isoprene emissions using satellite observations of the formaldehyde (HCHO) columns is subject to errors involving the column retrieval and the assumed relationship between HCHO columns and isoprene emissions, taken here from the GEOS- CHEM chemical transport model. Here we use a 6-year (1996–2001) HCHO column data set from the Global Ozone Monitoring Experiment (GOME) satellite instrument to (1) quantify these errors, (2) evaluate GOME-derived isoprene emissions with in situ flux measurements and a process-based emission inventory (Model of Emissions of Gases and Aerosols from Nature, MEGAN), and (3) investigate the factors driving the seasonal and interannual variability of North American isoprene emissions. The error in the GOME HCHO column retrieval is estimated to be 40%. We use the Master Chemical Mechanism (MCM) to quantify the time-dependent HCHO production from isoprene, a- and b-pinenes, and methylbutenol and show that only emissions of isoprene are detectable by GOME. The time-dependent HCHO yield from isoprene oxidation calculated by MCM is 20–30% larger than in GEOS-CHEM. GOME-derived isoprene fluxes track the observed seasonal variation of in situ measurements at a Michigan forest site with a 30% bias. The seasonal variation of North American isoprene emissions during 2001 inferred from GOME is similar to MEGAN, with GOME emissions typically 25% higher (lower) at the beginning (end) of the growing season. GOME and MEGAN both show a maximum over the southeastern United States, but they differ in the precise location. The observed interannual variability of this maximum is 20–30%, depending on month. The MEGAN isoprene emission dependence on surface air temperature explains 75% of the month-to-month variability in GOME-derived isoprene emissions over the southeastern United States during May–September 1996–2001. Citation: Palmer, P. I., et al. (2006), Quantifying the seasonal and interannual variability of North American isoprene emissions using satellite observations of the formaldehyde column, J. Geophys. Res., 111, D12315, doi:10.1029/2005JD006689. 1. Introduction [ 2 ] Emissions of volatile organic compounds (VOCs) from the terrestrial biosphere have important implications Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA. Now at the School of Earth and Environment, University of Leeds, Leeds, UK. Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachu- setts, USA. National Center for Atmospheric Research, Boulder, Colorado, USA. Department of Chemistry, University of Leeds, Leeds, UK. Department of Civil and Environmental Engineering, Washington State University, Pullman, Washington, USA. Battelle, Columbus, Ohio, USA. Copyright 2006 by the American Geophysical Union. 0148-0227/06/2005JD006689 for tropospheric ozone (O 3 ) [Wang and Shallcross, 2000], organic aerosols [Claeys et al., 2004], and climate change [Sanderson et al., 2003]. Local VOC emission data, representative of scales less than 1 km, are difficult to extrapolate, and consequently the magnitude and variabil- ity of these emissions is not well understood on conti- nental scales. Standard emission inventories based on ecosystem data and emission factors [Guenther et al., 2005] are poorly constrained. We have shown previously that observations of formaldehyde (HCHO) columns from the Global Ozone Monitoring Experiment (GOME) satel- lite instrument [Chance et al., 2000] provide information to estimate biogenic VOC emissions, specifically isoprene emissions, on a global scale and with resolution of the order of 100 km [Palmer et al., 2003]. We examine here the quantitative value of these data for better understand- D12315 1 of 14

Satellite observations of formaldehyde over North America from GOME

Formaldehyde (HCHO) is an important indicator of tropospheric hydrocarbon emissions and photochemical activity. We present HCHO observations over North America for July 1996 from the GOME instrument on-board the ESA ERS-2 satellite. Slant columns are determined to < 4 × 1015 molecules cm−2 sensitivity by directly fitting GOME radiance measurements. These show a distinct enhancement over the southeastern United States, consistent with a large regional source from oxidation of non-methane hydrocarbons including in particular isoprene. Conversion of slant to vertical columns is done by combining species vertical distribution information from the GEOS-CHEM 3-D tropospheric chemistry and transport model with scattering weights from the Smithsonian Astrophysical Observatory LIDORT multiple scattering radiative transfer model. The results demonstrate the ability to measure HCHO from space in typical continental atmospheres, and imply that space-based measurements of HCHO may provide valuable information on emission fluxes of reactive hydrocarbons.

Spatial distribution of isoprene emissions from North America derived from formaldehyde column measurements by the OMI satellite sensor

Received 10 May 2007; revised 19 September 2007; accepted 25 October 2007; published 26 January 2008. [1] Space-borne formaldehyde (HCHO) column measurements from the Ozone Monitoring Instrument (OMI), with 13 � 24 km 2 nadir footprint and daily global coverage, provide new constraints on the spatial distribution of biogenic isoprene emission from North America. OMI HCHO columns for June-August 2006 are consistent with measurements from the earlier GOME satellite sensor (1996–2001) but OMI is 2–14% lower. The spatial distribution of OMI HCHO columns follows that of isoprene emission; anthropogenic hydrocarbon emissions are undetectable except in Houston. We develop updated relationships between HCHO columns and isoprene emission from a chemical transport model (GEOS-Chem), and use these to infer top-down constraints on isoprene emissions from the OMI data. We compare the OMI-derived emissions to a state-of-science bottom-up isoprene emission inventory (MEGAN) driven by two land cover databases, and use the results to optimize the MEGAN emission factors (EFs) for broadleaf trees (the main isoprene source). The OMI-derived isoprene emissions in North America (June–August 2006) with 1 � 1 resolution are spatially consistent with MEGAN (R 2 = 0.48–0.68) but are lower (by 4–25% on average). MEGAN overestimates emissions in the Ozarks and the Upper South. A better fit to OMI (R 2 = 0.73) is obtained in MEGAN by using a uniform isoprene EF from broadleaf trees rather than variable EFs. Thus MEGAN may overestimate emissions in areas where it specifies particularly high EFs. Within-canopy isoprene oxidation may also lead to significant differences between the effective isoprene emission to the atmosphere seen by OMI and the actual isoprene emission determined by MEGAN.

Ozone profile and tropospheric ozone retrievals from the Global Ozone Monitoring Experiment: Algorithm description and validation

Received 18 May 2005; revised 4 August 2005; accepted 1 September 2005; published 29 October 2005. [1] Ozone profiles are derived from back scattered radiance spectra in the ultraviolet (289–339 nm) measured by the Global Ozone Monitoring Experiment (GOME) using the optimal estimation technique. Tropospheric Column Ozone (TCO) is directly derived using the known tropopause to divide the stratosphere and troposphere. To optimize the retrieval and improve the fitting precision needed for tropospheric ozone, we perform extensive wavelength and radiometric calibrations and improve forward model inputs. The a priori influence of retrieved TCO is � 15% in the tropics and increases to � 50% at high latitudes. The dominant error terms are the smoothing errors, instrumental randomnoise errors, and systematic temperature errors. We compare our GOME retrievals with Earth-Probe Total Ozone Mapping Spectrometer (TOMS) Total column Ozone (TO), Dobson/Brewer (DB) TO, and ozonesonde TCO at 33 World Ozone and Ultraviolet Radiation Data Centre (WOUDC) stations between 71� S and 75� N during 1996–1999. The mean biases with TOMS and DB TO are within 6 DU (2%, 1 DU = 2.69 � 10 16 molecules cm � 2 ) at most of the stations. The retrieved Tropospheric Column Ozone (TCO) captures most of the temporal variability in ozonesonde TCO; the mean biases are mostly within 3 DU (15%) and the standard deviations (1s) are within 3–8 DU (13–27%). We also compare our retrieved ozone profiles above � 15 km against Stratospheric Aerosol and Gas Experiment II measurements from 1996 to 1999. The mean biases and standard deviations are usually within 15%.

Evidence of lightning NOx and convective transport of pollutants in satellite observations over North America

Column observations of NO2 by GOME and CO by MOPITT over North America and surrounding oceans for April 2000 are analyzed using a regional chemical transport model. Transient enhancements in these measurements due to lightning NOx production or convective transport are examined. Evidence is found for lightning enhancements of NO2 over the continent and western North Atlantic and for convective transport enhancements of CO over the ocean. The two independent satellite measurements show consistent enhancements related to convective events. Model results suggest that the enhancements are particularly large in the lower troposphere due to convective downdrafts of lightning NOx and shallow convection of CO, implying that low-altitude aircraft in situ observations are potentially critical for evaluating the model simulations and validating satellite observations of these transient features.

Evaluation of GOME satellite measurements of tropospheric NO2 and HCHO using regional data from aircraft campaigns in the southeastern United States

[1] We compare tropospheric measurements of nitrogen dioxide (NO2) and formaldehyde (HCHO) from the Global Ozone Monitoring Experiment (GOME) satellite instrument with in situ measurements over eastern Texas and the southeast United States. On average, the GOME and in situ measurements of tropospheric NO2 and HCHO columns are consistent despite pronounced sampling differences. The geometric mean in situ to GOME ratios over the campaign are 1.08 for NO2 and 0.84 for HCHO, with corresponding geometric standard deviations of 1.27 and 1.38. The correlation of the observed column spatial variability between the two NO2 measurement sets is encouraging before (r 2 = 0.54, n = 18) and after (r 2 = 0.67, n = 18) correcting for a sampling bias. Mean relative vertical profiles of HCHO and NO2 calculated with a global three-dimensional model (GEOS-CHEM) and used in the GOME retrieval are highly consistent with in situ measurements; differences would affect the retrieved NO2 and HCHO columns by a few percent. GOME HCHO columns over eastern Texas include contributions from anthropogenic volatile organic compound (VOC) emissions but are dominated by biogenic VOC emissions at the regional scale in August–September when HCHO columns are within 20% of those over the southeastern United States. In situ measurements show that during summer the lowest 1500 m (the lower mixed layer) contains 75% of the tropospheric NO2 column over Houston and Nashville, and 60% of the HCHO column over Houston. Future validation of space-based measurements of tropospheric NO2 and HCHO columns over polluted regions should include coincident in situ measurements that span the entire satellite footprint, especially in the heterogeneous mixed layer. INDEX TERMS: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0365 Atmospheric Composition and Structure: Troposphere— composition and chemistry; 0394 Atmospheric Composition and Structure: Instruments and techniques;

Net ecosystem fluxes of isoprene over tropical South America inferred from Global Ozone Monitoring Experiment (GOME) observations of HCHO columns

Click Here JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, D20304, doi:10.1029/2008JD009863, 2008 for Full Article Net ecosystem fluxes of isoprene over tropical South America inferred from Global Ozone Monitoring Experiment (GOME) observations of HCHO columns Michael P. Barkley, 1 Paul I. Palmer, 1 Uwe Kuhn, 2,3 Juergen Kesselmeier, 2 Kelly Chance, 4 Thomas P. Kurosu, 4 Randall V. Martin, 4,5 Detlev Helmig, 6 and Alex Guenther 7 Received 24 January 2008; revised 17 June 2008; accepted 22 July 2008; published 17 October 2008. [ 1 ] We estimate isoprene emissions over tropical South America during 1997–2001 using column measurements of formaldehyde (HCHO) from the Global Ozone Monitoring Experiment (GOME) satellite instrument, the GEOS-Chem chemistry transport model, and the MEGAN (Model of Emissions of Gases and Aerosols from Nature) bottom-up isoprene inventory. GEOS-Chem is qualitatively consistent with in situ ground-based and aircraft concentration profiles of isoprene and HCHO, and GOME HCHO column data (r = 0.41; bias = +35%), but has less skill in reproducing wet season observations. Observed variability of GOME HCHO columns over South America is determined largely by isoprene and biomass burning. We find that the column contributions from other biogenic volatile organic compounds (VOC) are typically smaller than the column fitting uncertainty. HCHO columns influenced by biomass burning are removed using Along Track Scanning Radiometer (ATSR) firecounts and GOME NO 2 columns. We find that South America can be split into eastern and western regions, with fires concentrated over the eastern region. A monthly mean linear transfer function, determined by GEOS-Chem, is used to infer isoprene emissions from observed HCHO columns. The seasonal variation of GOME isoprene emissions over the western region is broadly consistent with MEGAN (r = 0.41; bias = 25%), with largest isoprene emissions during the dry season when the observed variability is consistent with knowledge of temperature dependence. During the wet season, other unknown factors play a significant role in determining observed variability. Citation: Barkley, M. P., P. I. Palmer, U. Kuhn, J. Kesselmeier, K. Chance, T. P. Kurosu, R. V. Martin, D. Helmig, and A. Guenther (2008), Net ecosystem fluxes of isoprene over tropical South America inferred from Global Ozone Monitoring Experiment (GOME) observations of HCHO columns, J. Geophys. Res., 113, D20304, doi:10.1029/2008JD009863. 1. Introduction [ 2 ] Tropical terrestrial ecosystems are a significant source of biogenic volatile organic compounds (BVOCs). The dominant nonmethane BVOC is isoprene (C 5 H 8 ), which represents almost half of the global annual nonmethane VOC flux [Guenther et al., 1995, 2006]. Tropical ecosystems contribute nearly 75% of the global atmospheric isoprene School of GeoSciences, University of Edinburgh, Edinburgh, UK. Biogeochemistry Department, Max Planck Institute for Chemistry, Mainz, Germany. Now at Agroscope Reckenholz-Taenikon Research Station, Zurich, Switzerland. Atomic and Molecular Physics Division, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA. Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada. INSTAAR, University of Colorado, Boulder, Colorado, USA. Biosphere-Atmosphere Interactions Group, Atmospheric Chemistry Division, NCAR, Boulder, Colorado, USA. Copyright 2008 by the American Geophysical Union. 0148-0227/08/2008JD009863

Undersampling correction for array detector-based satellite spectrometers

09.00 budget [Guenther et al., 2006], reflecting a year-long growing season, warm temperatures, and high solar insola- tion. The high VOC loading and favorable atmospheric conditions (high concentrations of the hydroxyl radical, OH) ensures that the tropics also exert considerable influ- ence on global tropospheric photochemistry [Andreae and Crutzen, 1997]. Isoprene has a strong influence on the oxidation capacity of the atmospheric boundary layer [Poisson et al., 2000; Monson and Holland, 2001], and can contribute to the formation of tropospheric ozone [Wang and Shallcross, 2000; Sanderson et al., 2003] and be a precursor of secondary organic aerosol [Claeys et al., 2004; Henze and Seinfeld, 2006], thereby playing a signif- icant role in determining Earth’s climate. Isoprene emis- sions also represent a significant loss of fixed carbon from the terrestrial biosphere, relative to the net biome produc- tivity [Kesselmeier et al., 2002a]. [ 3 ] Global and regional isoprene emissions, determined by bottom-up models constrained by sparse in situ data, are poorly known [Guenther et al., 1995, 2006; Potter et al., D20304 1 of 24