Thomas Röckmann | Utrecht University (original) (raw)
Uploads
Papers by Thomas Röckmann
The Journal of Physical Chemistry A, 2007
The relative photolysis rates of HCHO and HCDO have been studied in May 2004 at the European Phot... more The relative photolysis rates of HCHO and HCDO have been studied in May 2004 at the European Photoreactor Facility (EUPHORE) in Valencia, Spain. The photolytic loss of HCDO was measured relative to HCHO by long path FT-IR and DOAS detection during the course of the experiment. The isotopic composition of the reaction product H 2 was determined by isotope ratio mass spectrometry (IRMS) on air samples taken during the photolysis experiments. The relative photolysis rate obtained by FTIR is j HCHO /j HCDO ) 1.58 ( 0.03. The ratios of the photolysis rates for the molecular and the radical channels obtained from the IRMS data, in combination with the quantum yield of the molecular channel in the photolysis of HCHO, Φ HCHOfH 2 +CO (JPL Publication 06-2), are j HCHOfH 2 +CO /j HCDOfHD+CO ) 1.82 ( 0.07 and j HCHOfH+HCO /(j HCDOfH+DCO + j HCDOfD+HCO ) ) 1.10 ( 0.06. The atmospheric implications of the large isotope effect in the relative rate of photolysis and quantum yield of the formaldehyde isotopologues are discussed in relation to the global hydrogen budget.
Journal of Geophysical Research, 2012
1] We present the first inverse modeling study to estimate CO emissions constrained by both surfa... more 1] We present the first inverse modeling study to estimate CO emissions constrained by both surface and satellite observations. Our 4D-Var system assimilates National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA/ESRL) Global Monitoring Division (GMD) surface and Measurements Of Pollution In The Troposphere (MOPITT) satellite observations jointly by fitting a bias correction scheme. This approach leads to the identification of a positive bias of maximum 5 ppb in MOPITT column-averaged CO mixing ratios in the remote Southern Hemisphere (SH). The 4D-Var system is used to estimate CO emissions over South America in the period 2006-2010 and to analyze the interannual variability (IAV) of these emissions. We infer robust, high spatial resolution CO emission estimates that show slightly smaller IAV due to fires compared to the Global Fire Emissions Database (GFED3) prior emissions. South American dry season (August and September) biomass burning emission estimates amount to 60, 92, 42, 16 and 93 Tg CO/yr for 2006 to 2010, respectively. Moreover, CO emissions probably associated with pre-harvest burning of sugar cane plantations in São Paulo state are underestimated in current inventories by 50-100%. We conclude that climatic conditions (such as the widespread drought in 2010) seem the most likely cause for the IAV in biomass burning CO emissions. However, socio-economic factors (such as the growing global demand for soy, beef and sugar cane ethanol) and associated deforestation fires, are also likely as drivers for the IAV of CO emissions, but are difficult to link directly to CO emissions.
Journal of Geophysical Research, 2000
Carbon dioxide in the middle atmosphere is mass independently enriched in the hea _vy oxygen isot... more Carbon dioxide in the middle atmosphere is mass independently enriched in the hea _vy oxygen isotopes relative to trot>ost•heric values. That is, increasing with altitude, the •70/•60 ratio shows an additional enl•an•ement over what is expected on the basis of the •80/•60 increase. As tropospheric CO2 has a mass-dependent isotopic composition that varies by less ß 18 ...... than 3%0 •n/5 O, •sotop•c measurements of m•ddle atmospheric CO2, combined w•th a quantitative understanding of the enrichment mechanism, could provide valuable information regarding processes such as stratosphere-troposphere exchange and the mean age of an air mass. It is known that the mass-independent enrichment in stratospheric CO: occurs when CO,_ quenches an O(•D) atom formed by the photolysis of 03, but the details of this process remain uncertain. Here a series of laboratory and numerical experiments are presented which have been performed to study the time evolution and final equilibrium values of the CO2 + O(•D) reaction in an effort to reach a better understanding of the CO2 enrichment mechanism. Results show that while the isotopic composition of the CO2 reservoir is qualitatively controlled by the isotopic composition of the O(D) reservoir, there are a number of comphcat•ng factors. The simple mixing model discussed here consistently overpredicts the measured isotopic enrichment, thus indicating the CO2 + O(1D) isotopic exchange is more complicated than has generally been recognized. 1. Introduction Although CO2 is chemically inert throughout most of the atmosphere, it is a vital atmospheric constituent, inextricably linked to the Earth's biosphere. The largest fluxes of the global carbon cycle are those that link atmospheric CO2 to the oceans and to land vegetation. Atmospheric concentrations of CO2 have grown by approximately 30% over the past 2 centuries, to a current level of 360 ppmv, presently increasing at a rate of about 1.5 ppmv yr -• [Houghton et al. , 1996]. This is largely the result of human activities, particularly the combustion of fossil fuels and land use conversion. The atmospheric CO2 concentration is affected by processes that operate on different timescales, including interaction with the silicate cycle, dissolution in the oceans, and the annual cycles of photosynthesis and respiration.
Atmospheric Chemistry and Physics, 2012
We report the first data set of atmospheric abundances for the following four perfluoroalkanes
Atmospheric Chemistry and Physics, 2012
More than 450 air samples that were collected in the upper troposphere -lower stratosphere (UTLS)... more More than 450 air samples that were collected in the upper troposphere -lower stratosphere (UTLS) region by the CARIBIC aircraft (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) have been analyzed for molecular hydrogen (H 2 ) mixing ratios (χ (H 2 )) and H 2 isotopic composition (deuterium content, δD).
Atmospheric Chemistry and Physics, 2003
... changed. The results in Table 2 show that the total anthro-pogenic source, which accounts for... more ... changed. The results in Table 2 show that the total anthro-pogenic source, which accounts for the difference between the pre-industrial and present emissions, is considerably de-pleted relative to the pre-industrial source. The ...
Atmospheric Chemistry and Physics, 2007
We have used high spectral resolution spectroscopic measurements from the MIPAS instrument on the... more We have used high spectral resolution spectroscopic measurements from the MIPAS instrument on the Envisat satellite to simultaneously retrieve vertical profiles of H 2 O and HDO in the stratosphere and uppermost troposphere. Variations in the deuterium content of water are expressed in the common δ notation, where δD is the deviation of the Deuterium/Hydrogen ratio in a sample from a standard isotope ratio. A thorough error analysis of the retrievals confirms that reliable δD data can be obtained up to an altitude of ∼45 km. Averaging over multiple orbits and thus over longitudes further reduces the random part of the error. The absolute total error of averaged δD is between 36‰ and 111‰. With values lower than 42‰ the total random error is significantly smaller than the natural variability of δD. The data compare well with previous investigations. The MIPAS measurements now provide a unique global data set of highquality δD data that will provide novel insight into the stratospheric water cycle.
Atmospheric Chemistry and Physics, 2002
Measurements of the complete isotopic composition of atmospheric CO ( 13 CO, 14 CO, C 17 O, C 18 ... more Measurements of the complete isotopic composition of atmospheric CO ( 13 CO, 14 CO, C 17 O, C 18 O) have been carried out at the high northern latitude stations Spitsbergen, Norway, and Alert, Canada. The annual changes of the isotope signatures reflect the seasonally varying contributions from the individual CO sources and the OH sink. Short-term variability is small at the remote sampling locations. Nevertheless, the interannual variability is considerable, in particular for the summer minimum. The most prominent event was a strong increase in CO in 1998 that persisted for several months. Using the isotope signatures it is possible to clearly identify extraordinarily strong biomass burning during that season as the cause for this large-scale CO anomaly. In 1997, on the other hand, biomass burning emissions were very low, leading to an unusually low summer minimum and corresponding isotope signatures. The results underscore that monitoring of CO and its isotopic composition at remote high latitude stations is a valuable tool to better understand long-term variations of CO that are representative for the whole high northern latitude region.
Atmospheric Chemistry and Physics, 2014
Atmospheric Chemistry and Physics, 2012
Air samples collected at Cape Grim, Tasmania between 1978 and 2008 and during
Atmospheric Chemistry and Physics, 2013
The Journal of Physical Chemistry A, 2007
The relative photolysis rates of HCHO and HCDO have been studied in May 2004 at the European Phot... more The relative photolysis rates of HCHO and HCDO have been studied in May 2004 at the European Photoreactor Facility (EUPHORE) in Valencia, Spain. The photolytic loss of HCDO was measured relative to HCHO by long path FT-IR and DOAS detection during the course of the experiment. The isotopic composition of the reaction product H 2 was determined by isotope ratio mass spectrometry (IRMS) on air samples taken during the photolysis experiments. The relative photolysis rate obtained by FTIR is j HCHO /j HCDO ) 1.58 ( 0.03. The ratios of the photolysis rates for the molecular and the radical channels obtained from the IRMS data, in combination with the quantum yield of the molecular channel in the photolysis of HCHO, Φ HCHOfH 2 +CO (JPL Publication 06-2), are j HCHOfH 2 +CO /j HCDOfHD+CO ) 1.82 ( 0.07 and j HCHOfH+HCO /(j HCDOfH+DCO + j HCDOfD+HCO ) ) 1.10 ( 0.06. The atmospheric implications of the large isotope effect in the relative rate of photolysis and quantum yield of the formaldehyde isotopologues are discussed in relation to the global hydrogen budget.
Journal of Geophysical Research, 2012
1] We present the first inverse modeling study to estimate CO emissions constrained by both surfa... more 1] We present the first inverse modeling study to estimate CO emissions constrained by both surface and satellite observations. Our 4D-Var system assimilates National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA/ESRL) Global Monitoring Division (GMD) surface and Measurements Of Pollution In The Troposphere (MOPITT) satellite observations jointly by fitting a bias correction scheme. This approach leads to the identification of a positive bias of maximum 5 ppb in MOPITT column-averaged CO mixing ratios in the remote Southern Hemisphere (SH). The 4D-Var system is used to estimate CO emissions over South America in the period 2006-2010 and to analyze the interannual variability (IAV) of these emissions. We infer robust, high spatial resolution CO emission estimates that show slightly smaller IAV due to fires compared to the Global Fire Emissions Database (GFED3) prior emissions. South American dry season (August and September) biomass burning emission estimates amount to 60, 92, 42, 16 and 93 Tg CO/yr for 2006 to 2010, respectively. Moreover, CO emissions probably associated with pre-harvest burning of sugar cane plantations in São Paulo state are underestimated in current inventories by 50-100%. We conclude that climatic conditions (such as the widespread drought in 2010) seem the most likely cause for the IAV in biomass burning CO emissions. However, socio-economic factors (such as the growing global demand for soy, beef and sugar cane ethanol) and associated deforestation fires, are also likely as drivers for the IAV of CO emissions, but are difficult to link directly to CO emissions.
Journal of Geophysical Research, 2000
Carbon dioxide in the middle atmosphere is mass independently enriched in the hea _vy oxygen isot... more Carbon dioxide in the middle atmosphere is mass independently enriched in the hea _vy oxygen isotopes relative to trot>ost•heric values. That is, increasing with altitude, the •70/•60 ratio shows an additional enl•an•ement over what is expected on the basis of the •80/•60 increase. As tropospheric CO2 has a mass-dependent isotopic composition that varies by less ß 18 ...... than 3%0 •n/5 O, •sotop•c measurements of m•ddle atmospheric CO2, combined w•th a quantitative understanding of the enrichment mechanism, could provide valuable information regarding processes such as stratosphere-troposphere exchange and the mean age of an air mass. It is known that the mass-independent enrichment in stratospheric CO: occurs when CO,_ quenches an O(•D) atom formed by the photolysis of 03, but the details of this process remain uncertain. Here a series of laboratory and numerical experiments are presented which have been performed to study the time evolution and final equilibrium values of the CO2 + O(•D) reaction in an effort to reach a better understanding of the CO2 enrichment mechanism. Results show that while the isotopic composition of the CO2 reservoir is qualitatively controlled by the isotopic composition of the O(D) reservoir, there are a number of comphcat•ng factors. The simple mixing model discussed here consistently overpredicts the measured isotopic enrichment, thus indicating the CO2 + O(1D) isotopic exchange is more complicated than has generally been recognized. 1. Introduction Although CO2 is chemically inert throughout most of the atmosphere, it is a vital atmospheric constituent, inextricably linked to the Earth's biosphere. The largest fluxes of the global carbon cycle are those that link atmospheric CO2 to the oceans and to land vegetation. Atmospheric concentrations of CO2 have grown by approximately 30% over the past 2 centuries, to a current level of 360 ppmv, presently increasing at a rate of about 1.5 ppmv yr -• [Houghton et al. , 1996]. This is largely the result of human activities, particularly the combustion of fossil fuels and land use conversion. The atmospheric CO2 concentration is affected by processes that operate on different timescales, including interaction with the silicate cycle, dissolution in the oceans, and the annual cycles of photosynthesis and respiration.
Atmospheric Chemistry and Physics, 2012
We report the first data set of atmospheric abundances for the following four perfluoroalkanes
Atmospheric Chemistry and Physics, 2012
More than 450 air samples that were collected in the upper troposphere -lower stratosphere (UTLS)... more More than 450 air samples that were collected in the upper troposphere -lower stratosphere (UTLS) region by the CARIBIC aircraft (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) have been analyzed for molecular hydrogen (H 2 ) mixing ratios (χ (H 2 )) and H 2 isotopic composition (deuterium content, δD).
Atmospheric Chemistry and Physics, 2003
... changed. The results in Table 2 show that the total anthro-pogenic source, which accounts for... more ... changed. The results in Table 2 show that the total anthro-pogenic source, which accounts for the difference between the pre-industrial and present emissions, is considerably de-pleted relative to the pre-industrial source. The ...
Atmospheric Chemistry and Physics, 2007
We have used high spectral resolution spectroscopic measurements from the MIPAS instrument on the... more We have used high spectral resolution spectroscopic measurements from the MIPAS instrument on the Envisat satellite to simultaneously retrieve vertical profiles of H 2 O and HDO in the stratosphere and uppermost troposphere. Variations in the deuterium content of water are expressed in the common δ notation, where δD is the deviation of the Deuterium/Hydrogen ratio in a sample from a standard isotope ratio. A thorough error analysis of the retrievals confirms that reliable δD data can be obtained up to an altitude of ∼45 km. Averaging over multiple orbits and thus over longitudes further reduces the random part of the error. The absolute total error of averaged δD is between 36‰ and 111‰. With values lower than 42‰ the total random error is significantly smaller than the natural variability of δD. The data compare well with previous investigations. The MIPAS measurements now provide a unique global data set of highquality δD data that will provide novel insight into the stratospheric water cycle.
Atmospheric Chemistry and Physics, 2002
Measurements of the complete isotopic composition of atmospheric CO ( 13 CO, 14 CO, C 17 O, C 18 ... more Measurements of the complete isotopic composition of atmospheric CO ( 13 CO, 14 CO, C 17 O, C 18 O) have been carried out at the high northern latitude stations Spitsbergen, Norway, and Alert, Canada. The annual changes of the isotope signatures reflect the seasonally varying contributions from the individual CO sources and the OH sink. Short-term variability is small at the remote sampling locations. Nevertheless, the interannual variability is considerable, in particular for the summer minimum. The most prominent event was a strong increase in CO in 1998 that persisted for several months. Using the isotope signatures it is possible to clearly identify extraordinarily strong biomass burning during that season as the cause for this large-scale CO anomaly. In 1997, on the other hand, biomass burning emissions were very low, leading to an unusually low summer minimum and corresponding isotope signatures. The results underscore that monitoring of CO and its isotopic composition at remote high latitude stations is a valuable tool to better understand long-term variations of CO that are representative for the whole high northern latitude region.
Atmospheric Chemistry and Physics, 2014
Atmospheric Chemistry and Physics, 2012
Air samples collected at Cape Grim, Tasmania between 1978 and 2008 and during
Atmospheric Chemistry and Physics, 2013