[Show abstract][Hide abstract] ABSTRACT: We present the characterization and application of a new gas chromatography-time-of-flight mass spectrometry instrument (GC-TOFMS) for the quantitative analysis of halocarbons in air samples. The setup comprises three fundamental enhancements compared to our earlier work (Hoker et al., 2015): (1) full automation, (2) a mass resolving power R = m/Δ m of the TOFMS (Tofwerk AG, Switzerland) increased up to 4000 Th/Th and (3) a fully accessible data format of the mass spectrometric data. Automation in combination with the accessible data allowed an in-depth characterization of the instrument. Mass accuracy was found around 5 ppm after automatic recalibration of the mass axis in each measurement. A TOFMS configuration giving R = 3500 was chosen to provide an R-to-sensitivity ratio suitable for our purpose. Calculated detection limits were as low as a few femtograms as mass traces could be made highly specific for selected molecule fragments with the accurate mass information. The precision for substance quantification was 0.15 % at the best for an individual measurement and in general mainly determined by the signal-to-noise ratio of the chromatographic peak. The TOFMS was found to be linear within a concentration range from about 1 pg to 1 ng of analyte per Liter of air. At higher concentrations, non-linearities of a few percent were observed (precision level: 0.2 %) but could be attributed to a potential source within the detection system. A straight-forward correction for those non-linearities was applied in data processing, again by exploiting the accurate mass information. Based on the overall characterization results, the GC-TOFMS instrument was found to be very well-suited for the task of quantitative halocarbon trace gas observation and a big step forward compared to scanning, low resolution quadrupole MS and a TOFMS technique reported to be non-linear and restricted by a small dynamical range.
[Show abstract][Hide abstract] ABSTRACT: Profiles of CFC-11 (CCl3F) and CFC-12 (CCl2F2) of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) abord the European satellite Envisat have been retrieved from versions MIPAS/4.61–MIPAS/4.62 and MIPAS/5.02–MIPAS/5.06 level-1b data using the scientific level-2 processor run by Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research (IMK) and Consejo Superior de Investigaciones Científicas (CSIC), Instituto de Astrofísica de Andalucía (IAA). These profiles have been compared to measurements taken by the balloon borne Cryosampler, Mark IV (MkIV) and MIPAS-Balloon (MIPAS-B), the airborne MIPAS stratospheric aircraft (MIPAS-STR), the satellite borne Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) and the High Resolution Dynamic Limb Sounder (HIRDLS) as well as the ground based Halocarbon and other Atmospheric Trace Species (HATS) network for the reduced spectral resolution period (RR: January 2005–April 2012) of MIPAS Envisat. ACE-FTS, MkIV and HATS also provide measurements during the high spectral resolution period (FR: July 2002–March 2004) and were used to validate MIPAS Envisat CFC-11 and CFC-12 products during that time, as well as ILAS-II profiles. In general, we find that MIPAS Envisat shows slightly higher values for CFC-11 at the lower end of the profiles (below ~ 15 km) and in a comparison of HATS ground-based data and MIPAS Envisat measurements at 3 km below the tropopause. Differences range from approximately 10–50 pptv (~ 5–20 %) during the RR period. In general, differences are slightly smaller for the FR period. An indication of a slight high-bias at the lower end of the profile exists for CFC-12 as well, but this bias is far less pronounced than for CFC-11, so that differences at the lower end of the profile (below ~ 15 km) and in the comparison of HATS and MIPAS Envisat measurements taken at 3 km below the tropopause mainly stay within 10–50 pptv (~ 2–10 %) for the RR and the FR period. Above approximately 15 km, most comparisons are close to excellent, apart from ILAS-II, which shows large differences above ~ 17 km. Overall, percentage differences are usually smaller for CFC-12 than for CFC-11. For both species – CFC-11 and CFC-12 – we find that differences at the lower end of the profile tend to be larger at higher latitudes than in tropical and subtropical regions. In addition, MIPAS Envisat profiles have a maximum in the mixing ratio around the tropopause, which is most obvious in tropical mean profiles. Estimated measurement noise alone can, in most cases, not explain the standard deviation of the differences. This is attributed to error components not considered in the error estimate and also to natural variability which always plays a role when the compared instruments do not measure exactly the same air mass. Investigations concerning the temporal stability show very small negative drifts in MIPAS Envisat CFC-11 measurements. These drifts vary between ~ 1–3 % decade−1. For CFC-12, the drifts are also negative and close to zero up to ~ 30 km. Above that altitude larger drifts of up to ~ 50 % decade−1 appear which are negative up to ~ 35 km and positive, but of a similar magnitude, above.
[Show abstract][Hide abstract] ABSTRACT: The Arctic winter 2010/2011 was characterized by a persistent vortex with extremely low temperatures in the lower stratosphere above northern Scandinavia leading to a strong activation of chlorine compounds (ClOx) like Cl, Cl2, ClO, ClOOCl, OClO, and HOCl, which rapidly destroyed ozone when sunlight returned after winter solstice. The MIPAS-B (Michelson Interferometer for Passive Atmospheric Sounding) and TELIS (TErahertz and submillimeter LImb Sounder) balloon measurements obtained in northern Sweden on 31 March 2011 inside the polar vortex have provided vertical profiles of inorganic and organic chlorine species as well as diurnal variations of ClO around sunrise over the whole altitude range in which chlorine has been undergoing activation and deactivation. This flight was performed at the end of the winter during the last phase of ClOx deactivation. The complete inorganic and organic chlorine partitioning and budget for 31 March 2011, assumed to be representative for the late-winter Arctic stratosphere, has been derived by combining MIPAS-B and TELIS simultaneously observed molecules. A total chlorine amount of 3.41 ± 0.30 parts per billion by volume is inferred from the measurements (above 24 km). This value is in line with previous stratospheric observations carried out outside the tropics confirming the slightly decreasing chlorine amount in the stratosphere. Observations are compared and discussed with the output of a multi-year simulation performed with the chemistry climate model EMAC (ECHAM5/MESSy Atmospheric Chemistry). The simulated stratospheric total chlorine amount is in accordance with the MIPAS-B/TELIS observations, taking into account the fact that some chlorine source gases and very short-lived species are not included in the model.
[Show abstract][Hide abstract] ABSTRACT: MIPAS-Envisat is a satellite-borne sensor which was measuring vertical profiles of a wide range of trace gases from 2002 to 2012 using IR emission spectroscopy. We present geophysical validation for the operational retrieval (version 6.0) of N2O, CH4, CFC-12 and CFC-11 by the European Space Agency (ESA) of MIPAS-Envisat. The geophysical validation data are derived from measurements of samples collected by a cryogenic whole air sampler flown to altitudes of up to 34 km by means of large scientific balloons. In order to increase the number of coincidences between the satellite and the balloon observations we applied a trajectory matching technique. The results are presented for different time periods due to a change in the spectroscopic resolution of MIPAS as of early 2005. Retrieval results for N2O, CH4 and CFC-12 show partly good agreement for some altitude regions, which differs for the periods with different spectroscopic resolution. However, significant differences to the balloon data are also observed for some altitude regions, which depend on species and spectroscopic resolution. These differences need to be considered when using these data. The CFC-11 results from the operation retrieval version 6 cannot be recommended for scientific studies due to a systematic overestimation of the CFC-11 mixing ratios.
[Show abstract][Hide abstract] ABSTRACT: The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) was an infra-red (IR) limb emission spectrometer on the Envisat platform. It measured during day and night, pole-to-pole, over an altitude range from 6 to 70 km in nominal mode and up to 170 km in special modes, depending on the measurement mode, producing more than 1000 profiles day−1. We present the results of a validation study of methane version V5R_CH4_222 retrieved with the IMK/IAA MIPAS scientific level 2 processor. The level 1 spectra are provided by ESA, the version 5 was used. The time period covered corresponds to the period when MIPAS measured at reduced spectral resolution, i.e. 2005–2012. The comparison with satellite instruments includes the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS), the HALogen Occultation Experiment (HALOE), the Solar Occultation For Ice Experiment (SOFIE) and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). Furthermore, comparisons with MkIV balloon-borne solar occultation measurements and with air sampling measurements performed by the University of Frankfurt are presented. The validation activities include bias determination, in selected cases, assessment of histograms and comparison of corresponding climatologies. Above 50 km altitude, MIPAS methane mixing ratios agree within 3% with ACE-FTS and SOFIE. Between 30 and 40 km an agreement within 3% with SCIAMACHY has been found. In the middle stratosphere, there is no clear indication of a MIPAS bias since comparisons with various instruments contradict each other. In the lower stratosphere (below about 25–30 km) MIPAS CH4 is biased high with respect to satellite instruments, and the most likely estimate of this bias is 14%. However, in the comparison with CH4 data obtained from cryosampler measurements, there is no evidence of a MIPAS high bias between 20 and 25 km altitude. Precision validation is performed on collocated MIPAS-MIPAS pairs and suggests a slight underestimation of its errors by a factor of 1.2. A parametric model consisting of constant, linear, QBO and several sine and cosine terms with different periods has been fitted to the temporal variation of differences of stratospheric CH4 measurements by MIPAS and ACE-FTS for all 10° latitude/1–2 km altitude bins. Only few significant drifts can be calculated, due to the lack of data. Significant drifts with respect to ACE-FTS tend to have higher absolute values in the Northern Hemisphere, have no pronounced tendency in the sign, and do not exceed 0.2 ppmv per decade in absolute value.
[Show abstract][Hide abstract] ABSTRACT: We present the application of time-of-flight mass spectrometry (TOF MS) for the analysis of halocarbons in the atmosphere after cryogenic sample preconcentration and gas chromatographic separation. For the described field of application, the quadrupole mass spectrometer (QP MS) is a state-of-the-art detector. This work aims at comparing two commercially available instruments, a QP MS and a TOF MS, with respect to mass resolution, mass accuracy, stability of the mass axis and instrument sensitivity, detector sensitivity, measurement precision and detector linearity. Both mass spectrometers are operated on the same gas chromatographic system by splitting the column effluent to both detectors. The QP MS had to be operated in optimised single ion monitoring (SIM) mode to achieve a sensitivity which could compete with the TOF MS. The TOF MS provided full mass range information in any acquired mass spectrum without losing sensitivity. Whilst the QP MS showed the performance already achieved in earlier tests, the sensitivity of the TOF MS was on average higher than that of the QP MS in the "operational" SIM mode by a factor of up to 3, reaching detection limits of less than 0.2 pg. Measurement precision determined for the whole analytical system was up to 0.2% depending on substance and sampled volume. The TOF MS instrument used for this study displayed significant non-linearities of up to 10% for two-thirds of all analysed substances.
[Show abstract][Hide abstract] ABSTRACT: We report on HCFC-22 data acquired by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) in reduced spectral resolution nominal mode in the period from January 2005 to April 2012 from version 5.02 level-1b spectral data and covering an altitude range from the upper troposphere (above cloud top altitude) to about 50 km. The profile retrieval was performed by constrained nonlinear least squares fitting of measured limb spectral radiances to modelled spectra. The spectral ν4-band at 816.5 ± 13 cm−1 was used for the retrieval. A Tikhonov-type smoothing constraint was applied to stabilise the retrieval. In the lower stratosphere, we find a global volume mixing ratio of HCFC-22 of about 185 pptv in January 2005. The linear growth rate in the lower latitudes lower stratosphere was about 6 to 7 pptv yr−1 in the period 2005–2012. The obtained profiles were compared with ACE-FTS satellite data v3.5, as well as with MkIV balloon profiles and in situ cryosampler balloon measurements. Between 13 and 22 km, average agreement within −3 to +5 pptv (MIPAS–ACE) with ACE-FTS v3.5 profiles is demonstrated. Agreement with MkIV solar occultation balloon-borne measurements is within 10–20 pptv below 30 km and worse above, while in situ cryosampler balloon measurements are systematically lower over their full altitude range by 15–50 pptv below 24 km and less than 10 pptv above 28 km. Obtained MIPAS HCFC-22 time series below 10 km altitude are shown to agree mostly well to corresponding time series of near-surface abundances from NOAA/ESRL and AGAGE networks, although a more pronounced seasonal cycle is obvious in the satellite data, probably due to tropopause altitude fluctuations and subsidence of polar winter stratospheric air into the troposphere. A parametric model consisting of constant, linear, quasi-biennial oscillation (QBO) and several sine and cosine terms with different periods has been fitted to the temporal variation of stratospheric HCFC-22 for all 10° latitude/1 to 2 km altitude bins. The relative linear variation was always positive, with relative increases of 40–70% decade−1 in the tropics and global lower stratosphere, and up to 120% decade−1 in the upper stratosphere of the northern polar region and the southern extratropical hemisphere. In the middle stratosphere between 20 and 30 km, the observed trend is not consistent with the age of stratospheric air-corrected trend at ground, but stronger positive at the Southern Hemisphere and less strong increasing in the Northern Hemisphere, hinting towards changes in the stratospheric circulation over the observation period.
[Show abstract][Hide abstract] ABSTRACT: The three-dimensional quantification of small-scale processes in the upper troposphere and lower stratosphere is one of the challenges of current atmospheric research and requires the development of new measurement strategies. This work presents the first results from the newly developed Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) obtained during the ESSenCe (ESa Sounder Campaign) and TACTS/ESMVal (TACTS: Transport and composition in the upper troposphere/lowermost stratosphere, ESMVal: Earth System Model Validation) aircraft campaigns. The focus of this work is on the so-called dynamics-mode data characterized by a medium-spectral and a very-high-spatial resolution. The retrieval strategy for the derivation of two- and three-dimensional constituent fields in the upper troposphere and lower stratosphere is presented. Uncertainties of the main retrieval targets (temperature, O3, HNO3, and CFC-12) and their spatial resolution are discussed. During ESSenCe, high-resolution two-dimensional cross-sections have been obtained. Comparisons to collocated remote-sensing and in situ data indicate a good agreement between the data sets. During TACTS/ESMVal, a tomographic flight pattern to sense an intrusion of stratospheric air deep into the troposphere was performed. It was possible to reconstruct this filament at an unprecedented spatial resolution of better than 500 m vertically and 20 × 20 km horizontally.
[Show abstract][Hide abstract] ABSTRACT: In this study we reexamine nearly four decades of in situ balloon based stratospheric observations of SF6 and CO2 with an idealized model and reanalysis products. We use new techniques to account for the spatial and temporal inhomogeneity of the sparse balloon profiles and to calculate stratospheric mean ages of air more consistently from the observations with the idealized model. By doing so we are able to more clearly show and account for the variability of mean age of air throughout the bulk of the depth of the stratosphere. From an idealized model guided by the observations, we identify variability in the mean age due to the seasonal cycle of stratospheric transport, the quasi-biennial oscillation (QBO) in tropical zonal winds, major volcanic eruptions, and linear trends that vary significantly with altitude. We calculate a negative mean age trend in the lowest 5 km of the stratosphere that agrees within uncertainties with a trend calculated from a set of chemistry climate model mean ages in this layer. The mean age trends reverse sign in the middle and upper stratosphere and are in agreement with a previous positive trend estimate using the same observational data set, although we have substantially reduced the uncertainty on the trend. Our analysis shows that a long time series of in situ profile measurements of trace gases such as SF6 and CO2 can be a unique and useful indicator of stratospheric circulation variability on a range of time scales and an important contributor to help validate the stratospheric portion of global chemistry climate models. However, with only SF6 and CO2 measurements, the competing effects on mean age between mean circulation and mixing (tropical entrainment) are not uniquely separable.
[Show abstract][Hide abstract] ABSTRACT: We present the application of Time-of-Flight Mass Spectrometry (TOF MS) for the analysis of halocarbons in the atmosphere, after cryogenic sample preconcentration and gas chromatographic separation. For the described field of application, the Quadrupole Mass Spectrometer (QP MS) is the state-of-the-art detector. This work aims at comparing two commercially available instruments, a QP MS and a TOF MS with respect to mass resolution, mass accuracy, sensitivity, measurement precision and detector linearity. Both mass spectrometers are operated on the same gas chromatographic system by splitting the column effluent to both detectors. The QP MS had to be operated in optimised Single Ion Monitoring (SIM) mode to achieve a sensitivity which could compete with the TOF MS. The TOF MS provided full mass range information in any acquired mass spectrum without losing sensitivity. Whilst the QP MS showed the performance already achieved in earlier tests, the sensitivity of the TOF MS was on average higher than that of the QP MS in the "operational" SIM mode by a factor of up to 3 reaching detection limits of less than 0.2 pg. Measurement precision determined for the whole analytical system was up to 0.2% depending on substance and sampled volume. The TOF MS instrument used for this study displayed significant non-linearities of up to 10% for two third of all analysed substances.
[Show abstract][Hide abstract] ABSTRACT: During the recent SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) project an extensive data set of all halogen species relevant for the atmospheric budget of total organic bromine was collected in the western Pacific region using the Falcon aircraft operated by the German Aerospace agency DLR (Deutsches Zentrum fur LUft- und Raumfahrt) covering a vertical range from the planetary boundary layer up to the ceiling altitude of the aircraft of 13 km. In total, more than 700 measurements were performed with the newly developed fully automated in situ instrument GHOST-MS (Gas chromatograph for the Observation of Tracers - coupled with a Mass Spectrometer) by the Goethe University of Frankfurt (GUF) and with the onboard whole-air sampler WASP with subsequent ground-based state-of-the-art GC/MS analysis by the University of East Anglia (UEA). Both instruments yield good agreement for all major (CHBr3 and CH2Br2) and minor (CH2BrCl, CHBrCl2 and CHBr2Cl) VSLS (very short-lived substances), at least at the level of their 2 sigma measurement uncertainties. In contrast to the suggestion that the western Pacific could be a region of strongly increased atmospheric VSLS abundance (Pyle et al., 2011), we found only in the upper troposphere a slightly enhanced amount of total organic bromine from VSLS relative to the levels reported in Montzka and Reimann et al. (2011) for other tropical regions. From the SHIVA observations in the upper troposphere, a budget for total organic bromine, including four halons (H-1301, H-1211, H-1202, H-2402), CH3Br and the VSLS, is derived for the level of zero radiative heating (LZRH), the input region for the tropical tropopause layer (TTL) and thus also for the stratosphere. With the exception of the two minor VSLS CHBrCl2 and CHBr2Cl, excellent agreement with the values reported in Montzka and Reimann et al. (2011) is found, while being slightly higher than previous studies from our group based on balloon-borne measurements.
[Show abstract][Hide abstract] ABSTRACT: The effects of chemical two-way mixing on the Extratropical Transition Layer (ExTL) near the subtropical jet (STJ) is investigated by stratospheric tracer-tracer correlations. To this end, in-situ measurements were performed west of Africa (25- 32°N) during the TACTS/ESMVal mission in August/September 2012. The Atmospheric chemical Ionization Mass Spectrometer AIMS sampling HCl and HNO3 was for the first time deployed on the new German High Altitude and LOng range research aircraft HALO. Measurements of O3, CO, ECMWF analysis and the tight correlation of the unambiguous tracer HCl to O3 and HNO3 in the lower stratosphere were used to quantify the stratospheric content of these species in the ExTL. With increasing distance from the tropopause the stratospheric content increased from 10% to 100% with differing profiles for HNO3 and O3. Tropospheric fractions of 20% HNO3 and 40% O3 were detected up to a distance of 30 K above the tropopause.
[Show abstract][Hide abstract] ABSTRACT: The three-dimensional quantification of small scale processes in the upper troposphere and lower stratosphere is one of the challenges of current atmospheric research and requires the development of new measurement strategies. This work presents first results from the newly developed Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) obtained during the ESSenCe and TACTS/ESMVal aircraft campaigns. The focus of this work is on the so-called dynamics mode data characterized by a medium spectral and a very high spatial resolution. The retrieval strategy for the derivation of two- and three-dimensional constituent fields in the upper troposphere and lower stratosphere is presented. Uncertainties of the main retrieval targets (temperature, O3, HNO3 and CFC-12) and their spatial resolution are discussed. During ESSenCe, high resolution two-dimensional cross-sections have been obtained. Comparisons to collocated remote-sensing and in-situ data indicate a good agreement between the data sets. During TACTS/ESMVal a tomographic flight pattern to sense an intrusion of stratospheric air deep into the troposphere has been performed. This filament could be reconstructed with an unprecedented spatial resolution of better than 500 m vertically and 20 km × 20 km horizontally.
[Show abstract][Hide abstract] ABSTRACT: In this work, we have revisited the spectroscopy of the R(6) manifold of the ν3 band of methane which is particularly suitable for in situ laser monitoring of CH4. For that purpose, a home-made Difference Frequency Generation (DFG) laser emitting at 3.24 µm has been coupled to a cryogenically-cooled optical cell to investigate the temperature dependences of the air-broadening, the air-narrowing and the air-mixing coefficients of these ν3 R(6) manifold transitions. The temperatures of the measurements range from 213.5 K to room temperature. These are typically the temperatures found in the troposphere and the lower stratosphere. Finally, the measured spectroscopic parameters have been used to process the in-situ methane absorption spectra recorded by a balloon-borne laser diode spectrometer.
Journal of Quantitative Spectroscopy and Radiative Transfer 08/2013; DOI:10.1016/j.jqsrt.2013.08.003 · 2.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This work reassesses the global atmospheric budget of H2 with
the TM5 model. The recent adjustment of the calibration scale for
H2 translates into a change in the tropospheric burden.
Furthermore, the ECMWF Reanalysis-Interim (ERA-Interim) data from the
European Centre for Medium-Range Weather Forecasts (ECMWF) used in this
study show slower vertical transport than the operational data used
before. Consequently, more H2 is removed by deposition. The
deposition parametrization is updated because significant deposition
fluxes for snow, water, and vegetation surfaces were calculated in our
previous study. Timescales of 1-2 h are asserted for the transport of
H2 through the canopies of densely vegetated regions. The
global scale variability of H2 and δ[DH2] is
well represented by the updated model. H2 is slightly
overestimated in the Southern Hemisphere because too little
H2 is removed by dry deposition to rainforests and savannahs.
The variability in H2 over Europe is further investigated
using a high-resolution model subdomain. It is shown that discrepancies
between the model and the observations are mainly caused by the finite
model resolution. The tropospheric burden is estimated at 165±8
Tg H2. The removal rates of H2 by deposition and
photochemical oxidation are estimated at 53±4 and 23±2 Tg
H2/yr, resulting in a tropospheric lifetime of 2.2±0.2
Also accessible through Utrecht University repository: http://dspace.library.uu.nl/handle/1874/275776
Journal of Geophysical Research Atmospheres 05/2013; DOI:10.1002/jgrd.50204 · 3.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The TACTS (Transport and Composition in the UTLS) mission is the first
large atmospheric mission of the new German research aircraft HALO.
TACTS aims at improving our understanding of the transport processes
which determine the chemical composition in the UTLS with a special
emphasis on the transition from summer to fall. The mission was flown in
August and September 2012 with a fully equipped aircraft carrying 13
different instruments measuring a wide range of chemical tracers with
different lifetimes and different source-sink characteristics. The
payload consists of both in-situ and remote sensing instruments. In
addition to TACTS the same payload was employed to measure the chemical
composition during a large north-south transect as part of the ESMVal
project. Data are available up to to altitudes above 15 km, potential
temperatures above 400 K and covering the latitude range from 65°S
to 80°N. Due to the large payload a very wide range of measurements
allows for a very good characterisation of the chemical composition. All
instruments performed well and close to complete data sets are available
for all flights performed during both missions. We present an overview
of the scientific aims of TACTS, the payload, the measurements performed
and some selected first results.
[Show abstract][Hide abstract] ABSTRACT: Dynamic and chemical processes modify the ozone (O3) budget of the upper
troposphere/lower stratosphere, leading to locally variable O3 trends.
In this region, O3 acts as a strong greenhouse gas with a net positive
radiative forcing. It has been suggested, that the correlation of the
stratospheric tracer hydrochloric acid (HCl) with O3 can be used to
quantify stratospheric O3 in the UT/LS region (Marcy et al., 2004). The
question is, whether the stratospheric contribution to the nitric acid
(HNO3) budget in the UT/LS can be determined by a similar approach in
order to differentiate between tropospheric and stratospheric sources of
HNO3. To this end, we performed in situ measurements of HCl and HNO3
with a newly developed Atmospheric chemical Ionization Mass Spectrometer
(AIMS) during the TACTS (Transport and Composition in the UTLS) / ESMVal
(Earth System Model Validation) mission in August/September 2012. The
linear quadrupole mass spectrometer deployed aboard the new German
research aircraft HALO was equipped with a new discharge source
generating SF5- reagent ions and an in-flight calibration allowing for
accurate, spatially highly resolved trace gas measurements. In addition,
sulfur dioxide (SO2), nitrous acid (HONO) and chlorine nitrate (ClONO2)
have been simultaneously detected with the AIMS instrument. Here, we
show trace gas distributions of HCl and HNO3 measured during a
North-South transect from Northern Europe to Antarctica (68° N to
65° S) at 8 to 15 km altitude and discuss their latitude
dependence. In particular, we investigate the stratospheric ozone
contribution to the ozone budget in the mid-latitude UT/LS using
correlations of HCl with O3. Differences in these correlations in the
subtropical and Polar regions are discussed. A similar approach is used
to quantify the HNO3 budget of the UT/LS. We identify unpolluted
atmospheric background distributions and various tropospheric HNO3
sources in specific regions. Our observations can be compared to data
from remote sensing instruments. Further, they will help to validate
global chemistry-climate models to gain a better understanding of the
trace gas distribution in the UT/LS. Marcy, T. P., Fahey, D. W., Gao,
R. S., Popp, P. J., Richard, E. C., Thompson, T. L., Rosenlof, K. H.,
Ray, E. A., Salawitch, R. J., Atherton, C. S., Bergmann, D. J., Ridley,
B. A., Weinheimer, A. J., Loewenstein, M., Weinstock, E. M., and
Mahoney, M. J.: Quantifying stratospheric ozone in the upper troposphere
with in situ measurements of HCl, Science, 304, 261-265, 2004.