Heinrich Bovensmann

SCIAMACHY: Mission Objectives and Measurement Modes

Abstract SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) is a spectrometer designed to measure sunlight transmitted, reflected, and scattered by the earth’s atmosphere or surface in the ultraviolet, visible, and near-infrared wavelength region (240–2380 nm) at moderate spectral resolution (0.2–1.5 nm, λ/Δλ ≈ 1000–10 000). SCIAMACHY will measure the earthshine radiance in limb and nadir viewing geometries and solar or lunar light transmitted through the atmosphere observed in occultation. The extraterrestrial solar irradiance and lunar radiance will be determined from observations of the sun and the moon above the atmosphere. The absorption, reflection, and scattering behavior of the atmosphere and the earth’s surface is determined from comparison of earthshine radiance and solar irradiance. Inversion of the ratio of earthshine radiance and solar irradiance yields information about the amounts and distribution of important atmospheric constituents and the spectral reflecta...

Retrieval of atmospheric CO2 with enhanced accuracy and precision from SCIAMACHY: validation with FTS measurements and comparison with model results

The Bremen Optimal Estimation differential optical absorption spectroscopy (DOAS) (BESD) algorithm for satellite based retrievals of XCO_2 (the column-average dry-air mole fraction of atmospheric CO_2) has been applied to Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) data. It uses measurements in the O_2-A absorption band to correct for scattering of undetected clouds and aerosols. Comparisons with precise and accurate ground-based Fourier transform spectrometer (FTS) measurements at four Total Carbon Column Observing Network (TCCON) sites have been used to quantify the quality of the new SCIAMACHY XCO_2 data set. Additionally, the results have been compared to NOAAs assimilation system CarbonTracker. The comparisons show that the new retrieval meets the expectations from earlier theoretical studies. We find no statistically significant regional XCO_2 biases between SCIAMACHY and the FTS instruments. However, the standard error of the systematic differences is in the range of 0.2 ppm and 0.8 ppm. The XCO_2 single-measurement precision of 2.5 ppm is similar to theoretical estimates driven by instrumental noise. There are no significant differences found for the year-to-year increase as well as for the average seasonal amplitude between SCIAMACHY XCO_2 and the collocated FTS measurements. Comparison of the year-to-year increase and also of the seasonal amplitude of CarbonTracker exhibit significant differences with the corresponding FTS values at Darwin. Here the differences between SCIAMACHY and CarbonTracker are larger than the standard error of the SCIAMACHY values. The difference of the seasonal amplitude exceeds the significance level of 2 standard errors. Therefore, our results suggest that SCIAMACHY may provide valuable additional information about XCO_2, at least in regions with a low density of in situ measurements.

Remote sensing of fugitive methane emissions from oil and gas production in North American tight geologic formations

In the past decade, there has been a massive growth in the horizontal drilling and hydraulic fracturing of shale gas and tight oil reservoirs to exploit formerly inaccessible or unprofitable energy resources in rock formations with low permeability. In North America, these unconventional domestic sources of natural gas and oil provide an opportunity to achieve energy self-sufficiency and to reduce greenhouse gas emissions when displacing coal as a source of energy in power plants. However, fugitive methane emissions in the production process may counter the benefit over coal with respect to climate change and therefore need to be well quantified. Here we demonstrate that positive methane anomalies associated with the oil and gas industries can be detected from space and that corresponding regional emissions can be constrained using satellite observations. On the basis of a mass-balance approach, we estimate that methane emissions for two of the fastest growing production regions in the United States, the Bakken and Eagle Ford formations, have increased by 990 ± 650 ktCH4 yr−1 and 530 ± 330 ktCH4 yr−1 between the periods 2006–2008 and 2009–2011. Relative to the respective increases in oil and gas production, these emission estimates correspond to leakages of 10.1% ± 7.3% and 9.1% ± 6.2% in terms of energy content, calling immediate climate benefit into question and indicating that current inventories likely underestimate the fugitive emissions from Bakken and Eagle Ford.

Comparison of measurements and model calculations of stratospheric bromine monoxide

Ground-based zenith sky UV-visible measurements of stratospheric bromine monoxide (BrO) slant column densities are compared with simulations from the SLIMCAT three-dimensional chemical transport model. The observations have been obtained from a network of 11 sites, covering high and midlatitudes of both hemispheres. This data set gives for the first time a near-global picture of the distribution of stratospheric BrO from ground-based observations and is used to test our current understanding of stratospheric bromine chemistry. In order to allow a direct comparison between observations and model calculations, a radiative transfer model has been coupled to the chemical model to calculate simulated slant column densities. The model reproduces the observations in general very well. The absolute amount of the BrO slant columns is consistent with a total stratospheric bromine loading of 20 ± 4 ppt for the period 1998-2000, in agreement with previous estimates. The seasonal and latitudinal variations of BrO are well reproduced by the model. In particular, the good agreement between the observed and modeled diurnal variation provides strong evidence that the BrO-related bromine chemistry is correctly modeled. A discrepancy between observed and modeled BrO at high latitudes during events of chlorine activation can be resolved by increasing the rate constant for the reaction BrO + ClO → BrCl + O 2 to the upper limit of current recommendations. However, other possible causes of the discrepancy at high latitudes cannot be ruled out.

The Ozone Hole Breakup in September 2002 as Seen by SCIAMACHY on ENVISAT

An unprecedented stratospheric warming in the Southern Hemisphere in September 2002 led to the breakup of the Antarctic ozone hole into two parts. The Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) on the European Environmental Satellite (ENVISAT ) performed continuous observations of limb-scattered solar radiance spectra throughout the stratospheric warming. Thereby, global measurements of vertical profiles of several important minor constituents are provided with a vertical resolution of about 3 km. In this study, stratospheric profiles of O3 ,N O 2, and BrO retrieved from SCIAMACHY limb-scattering observations together with polar stratospheric cloud (PSC) observations for selected days prior to (12 September), during (27 September), and after (2 October) the ozone hole split are employed to provide a picture of the temporal evolution of the Antarctic stratosphere’s three-dimensional structure.

Atmospheric water vapor amounts retrieved from GOME satellite data

A new method for the retrieval of global atmospheric vertical column amounts of water vapor from measurements of the Global Ozone Monitoring Experiment (GOME) is presented. The method is based on a modified Differential Optical Absorption Spectroscopy (DOAS) approach, taking into account the effects arising from strong wavelength dependent absorptions. In this paper the feasibility of this approach is demonstrated and first estimates on the retrieval precision and the accuracy of the H 2 O data product are given by comparison with selected Special Sensor Microwave Imager (SSM/I) data.

FIRST OBSERVATION OF THE OIO MOLECULE BY TIME-RESOLVED FLASH PHOTOLYSIS ABSORPTION SPECTROSCOPY

Abstract In the time-resolved flash photolysis of I 2 in O 3 , in addition to the IO electronic bands between 21500 and 26000 cm −1 , a new absorption spectrum has been observed between 15000 and 21500 cm −1 , which is attributed to the A-X electronic bands of the OIO radical. A number of spectroscopic constants of the A state of OIO were determined by linear least-squares fitting the observed spectrum: ν 1 (symmetric IO stretch) ω 1 = 631 cm −1 , ν 1 anharmonicity constant ω 1 χ 1 = 2.6 cm −1 , ν 2 (OIO angle bend) ω 2 = 177 cm −1 , electronic energy with respect to the ground state T e = 14553 cm −1 . These values are in good agreement with those expected from measurements of the same electronic bands in OClO and OBrO.

Measurements of iodine monoxide (IO) above Spitsbergen

Zenithskymeasurementsofscatteredlighthave been made at Ny-Alesund, Spitsbergen (79N, 12E) since thebeginningof1995. Adierentialopticalabsorptionspec- troscopy (DOAS)algorithm hasbeenusedtoretrievedier- ential slant column densities (DSCD) of IO for the observa- tionsfrom1995-1998. IOwasdetectedeveryyearforseveral days within each month. Model simulations result in an es- timatedstratosphericIOmixingratiointherangefrom0.65 to 0.80 (0:2) pptv in polar spring 1997. In addition, indi- cations for the presence of tropospheric IO have been found in late spring and summer of each year.

Retrieval of total water vapour column amounts from GOME/ERS-2 data

Abstract A method for the retrieval of vertical column amounts of atmospheric water vapour from measurements of the Global Ozone Monitoring Experiment (GOME) in the visible spectral region is presented. Originally developed for the determination of global ozone concentrations, the GOME instrument is operating successfully on ERS-2 since 1995, providing information also on several other atmospheric constituents like NO 2 , BrO, OClO, H 2 CO, SO 2 , and recently also H 2 O. The method for the derivation of water vapour amounts is based on the Differential Optical Absorption Spectroscopy (DOAS) approach, which has been extended to take into account effects arising from a strongly wavelength dependent absorption. Further improvements of the algorithm now allow to retrieve water vapour column densities under all cloud conditions. First results show an acceptable agreement between total water vapour columns derived from GOME measurements and H 2 O columns obtained from the Special Sensor Microwave Imager SSM/I data, although the scatter of the GOME data is high, which needs to be further investigated.

Global atmospheric monitoring with SCIAMACHY

Abstract SCIAMACHY (SCanning Imaging Absorption spectrometer for Atmospheric CHartographY) is a space based spectrometer designed to measure sunlight transmitted, reflected and scattered by the Earth atmosphere or surface. It is a contribution to the Envisat-1 satellite to be launched in late 1999. SCIAMACHY measurements will provide amounts and distribution of 0 3 , BrO, OCl0, ClO, S0 2 , H 2 CO, N0 2 , CO, CO 2 , CH 4 , H 2 O, N 2 0, pressure, temperature, aerosol, radiation, cloud cover and cloud top height from atmospheric measurements in nadir, limb and occultation geometry. By the combination of the near simultaneous limb and nadir observations SCIAMACHY is one of a limited number of instruments which is able to detect tropospheric column amounts of 0 3 , N0 2 , CO, CH 4 , H 2 O, N 2 0, S0 2 , H 2 CO, and BrO down to the planetary boundary layer under cloud free conditions.