Global distributions of profiles of sulphur hexafluoride (SF6) have been retrieved from limb emission spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on ...Envisat covering the period September 2002 to March 2004. Individual SF6 profiles have a precision of 0.5 pptv below 25 km altitude and a vertical resolution of 4?6 km up to 35 km altitude. These data have been validated versus in situ observations obtained during balloon flights of a cryogenic whole-air sampler. For the tropical troposphere a trend of 0.227±0.008 pptv/yr has been derived from the MIPAS data, which is in excellent agreement with the trend from ground-based flask and in situ measurements from the National Oceanic and Atmospheric Administration Earth System Research Laboratory, Global Monitoring Division. For the data set currently available, based on at least three days of data per month, monthly 5° latitude mean values have a 1? standard error of 1%. From the global SF6 distributions, global daily and monthly distributions of the apparent mean age of air are inferred by application of the tropical tropospheric trend derived from MIPAS data. The inferred mean ages are provided for the full globe up to 90° N/S, and have a 1? standard error of 0.25 yr. They range between 0 (near the tropical tropopause) and 7 years (except for situations of mesospheric intrusions) and agree well with earlier observations. The seasonal variation of the mean age of stratospheric air indicates episodes of severe intrusion of mesospheric air during each Northern and Southern polar winter observed, long-lasting remnants of old, subsided polar winter air over the spring and summer poles, and a rather short period of mixing with midlatitude air and/or upward transport during fall in October/November (NH) and April/May (SH), respectively, with small latitudinal gradients, immediately before the new polar vortex starts to form. The mean age distributions further confirm that SF6 is destroyed in the mesosphere to a considerable amount. Model calculations with the Karlsruhe simulation model of the middle atmosphere (KASIMA) chemical transport model agree well with observed global distributions of the mean age only if the SF6 sink reactions in the mesosphere are included in the model.
Global distributions of profiles of sulphur hexafluoride (SF sub(6)) have been retrieved from limb emission spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) ...on Envisat covering the period September 2002 to March 2004. Individual SF sub(6) profiles have a precision of 0.5 pptv below 25 km altitude and a vertical resolution of 4-6 km up to 35 km altitude. These data have been validated versus in situ observations obtained during balloon flights of a cryogenic whole-air sampler. For the tropical troposphere a trend of 0.227 plus or minus 0.008 pptv/yr has been derived from the MIPAS data, which is in excellent agreement with the trend from ground-based flask and in situ measurements from the National Oceanic and Atmospheric Administration Earth System Research Laboratory, Global Monitoring Division. For the data set currently available, based on at least three days of data per month, monthly 5 degree latitude mean values have a 1 sigma standard error of 1%. From the global SF sub(6) distributions, global daily and monthly distributions of the apparent mean age of air are inferred by application of the tropical tropospheric trend derived from MIPAS data. The inferred mean ages are provided for the full globe up to 90 degree N/S, and have a 1 sigma standard error of 0.25 yr. They range between 0 (near the tropical tropopause) and 7 years (except for situations of mesospheric intrusions) and agree well with earlier observations. The seasonal variation of the mean age of stratospheric air indicates episodes of severe intrusion of mesospheric air during each Northern and Southern polar winter observed, long-lasting remnants of old, subsided polar winter air over the spring and summer poles, and a rather short period of mixing with midlatitude air and/or upward transport during fall in October/November (NH) and April/May (SH), respectively, with small latitudinal gradients, immediately before the new polar vortex starts to form. The mean age distributions further confirm that SF sub(6) is destroyed in the mesosphere to a considerable amount. Model calculations with the Karlsruhe simulation model of the middle atmosphere (KASIMA) chemical transport model agree well with observed global distributions of the mean age only if the SF sub(6) sink reactions in the mesosphere are included in the model.
During the CRISTA-1 mission three pronounced fingerlike structures reaching from the lower latitudes to the mid-latitudes, so-called streamers, were observed in the measurements of several trace ...gases in early November 1994. A simulation of these streamers in previous studies employing the KASIMA (Karlsruhe Simulation Model of the Middle Atmosphere) and ROSE (Research on Ozone in the Stratosphere and its Evolution) model, both being Eulerian models, show that their formation is due to adiabatic transport processes. Here, the impact of mixing on the development of these streamers is investigated. These streamers were simulated with the CLaMS model (Chemical Lagrangian Model of the Stratosphere), a Lagrangian model, using N2O as long-lived tracer. Using several different initialisations the results were compared to the KASIMA simulations and CRISTA (Cryogenic Infrared Spectrometer and Telescope for the Atmosphere) observations. Further, since the KASIMA model was employed to derive a 9-year climatology, the quality of the reproduction of streamers from such a study was tested by the comparison of the KASIMA results with CLaMS and CRISTA. The streamers are reproduced well for the Northern Hemisphere in the simulations of CLaMS and KASIMA for the 6 November 1994. However, in the CLaMS simulation a stronger filamentation is found while larger discrepancies between KASIMA and CRISTA were found especially for the Southern Hemisphere. Further, compared to the CRISTA observations the mixing ratios of N2O are in general underestimated in the KASIMA simulations. An improvement of the simulations with KASIMA was obtained for a simulation time according to the length of the CLaMS simulation. To quantify the differences between the simulations with CLaMS and KASIMA, and the CRISTA observations, the probability density function technique (PDF) is used to interpret the tracer distributions. While in the PDF of the KASIMA simulation the small scale structures observed by CRISTA are smoothed out due to the numerical diffusion in the model, the PDFs derived from CRISTA observations can be reproduced by CLaMS by optimizing the mixing parameterisation. Further, this procedure gives information on small-scale variabilities not resolved by the CRISTA observations.
Within the framework of the NDSC (Network for the Detection of Stratospheric Change) ground-based FTIR solar absorption spectra have been routinely recorded at Izaña Observatory (28° N, 16° W) on ...Tenerife Island since March 1999. By analyzing the shape of the absorption lines, and their different temperature sensitivities, the vertical distribution of the absorbers can be retrieved. Unique time series of subtropical profiles of O3, HCl, HF, N2O, and CH4 are presented. The effects of both dynamical and chemical annually varying cycles can be seen in the retrieved profiles. These include enhanced upwelling and photochemistry in summer and a more disturbed atmosphere in winter, which are typical of the subtropical stratosphere. A detailed error analysis has been performed for each profile. The output from two different three-dimensional (3-D) chemical transport models (CTMs), which are forced by ECMWF analyses, are compared to the measured profiles. Both models agree well with the measurements in tracking abrupt variations in the atmospheric structure, e.g. due to tropical streamers, in particular for the lower stratosphere. Simulated and measured profiles also reflect similar dynamical and chemical annual cycles. However, the differences between their mixing ratios clearly exceed the error bars estimated for the measured profiles. Possible reasons for this are discussed.
Validation of MIPAS ClONO2 measurements Höpfner, M.; von Clarmann, T.; Fischer, H. ...
Atmospheric chemistry and physics discussions,
10/2006, Letnik:
6, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Altitude profiles of ClONO2 retrieved with the IMK (Institut für Meteorologie und Klimaforschung) science-oriented data processor from MIPAS/Envisat (Michelson Interferometer for Passive Atmospheric ...Sounding on Envisat) mid-infrared limb emission measurements between July 2002 and March 2004 have been validated by comparison with balloon-borne (Mark IV, FIRS2, MIPAS-B), airborne (MIPAS-STR), ground-based (Spitsbergen, Thule, Kiruna, Harestua, Jungfraujoch, Izaña, Wollongong, Lauder), and spaceborne (ACE-FTS) observations. With few exceptions we found very good agreement between these instruments and MIPAS with no evidence for any bias in most cases and altitude regions. For balloon-borne measurements typical absolute mean differences are below 0.05 ppbv over the whole altitude range from 10 to 39 km. In case of ACE-FTS observations mean differences are below 0.03 ppbv for observations below 26 km. Above this altitude the comparison with ACE-FTS is affected by the photochemically induced diurnal variation of ClONO2. Correction for this by use of a chemical transport model led to an overcompensation of the photochemical effect by up to 0.1 ppbv at altitudes of 30?35 km in case of MIPAS-ACE-FTS comparisons while for the balloon-borne observations no such inconsistency has been detected. The comparison of MIPAS derived total column amounts with ground-based observations revealed no significant bias in the MIPAS data. Mean differences between MIPAS and FTIR column abundances are 0.11±0.12×1014 cm?2 (1.0±1.1%) and ?0.09±0.19×1014 cm?2 (?0.8±1.7%), depending on the coincidence criterion applied. ?2 tests have been performed to assess the combined precision estimates of MIPAS and the related instruments. When no exact coincidences were available as in case of MIPAS ? FTIR or MIPAS ? ACE-FTS comparisons it has been necessary to take into consideration a coincidence error term to account for ?2 deviations. From the resulting ?2 profiles there is no evidence for a systematic over/underestimation of the MIPAS random error analysis.
Recent analysis of observations of stratospheric polar ozone and a state-of-the-art CTM indicate a tight correlation between solar particle flux and the residuum between observation and model ozone ...concentration in the middle stratosphere during polar winter (Sinnhuber et al., 2006). Here we analyse the results of a multiannual run with the KASIMA model for possible signatures of solar variability. Whereas the model generally shows a good agreement between ground based and satellite based observations of long-lived tracers and ozone, we find for mid stratospheric ozone at high latitudes generally a good correlation between the model and observations. Only in the years 1994/95 and 2003 observations clearly indicate a ozone deficit compared to the model results. For the year 2003, a model simulation with additional NOx according MIPAS-observations reduces this disagreement. We speculate that NOx transported downward in the course of the winter can partially explain the correlation with observation but argue, that also specific transport properties could cause deviations between model and observation adding artificially to this correlation.
Observational data from 0.6-1.3 cm are reported for the S 106 nebula and discussed in terms of a wind model for bipolar outflows from young stellar objects. Optical, IR and radio data are presented, ...including a comparison between thermal emission from dust and radio emission from a gas. The data indicate that a single star is exciting the entire nebula and is associated with an equatorial gap at all frequencies. A point source with two components has been detected in the center of the gap. The 130 K temperature dominates the 10 micron feature, and a second component has been detected but not resolved. The S 106 radio lobes contain clumped structures with electron densities reaching 40,000/cu cm. The central, BO III-O9V type, star loses mass at a rate of 0.000016 solar mass per year, with densest mass outflows occurring at the equator.
GL961: an infrared double source LENZEN, R; HODAPP, K.-W; REDDMANN, T
Astronomy and astrophysics (Berlin),
08/1984, Letnik:
137, Številka:
2
Journal Article
Recenzirano
High resolution near infrared maps (2.2 microns, 3.6 microns) are presented which demonstrate that GL961 is an infrared double source composed of two pointlike components which are separated by about ...5 arcsec. Optical (0.9 micron) identifications (Eiroa, 1981) refer to the western component for which a color temperature of about 1050 K at 3 microns is deduced. The VLA-position, in constrast, coincides with that of the eastern much redder component. To explain the 3.1 micron-absorption feature observed for the whole complex (Willner et al., 1982), an absorption depth of at least 0.6 mag is required even for the bluer component. The infrared polarization is paralle to the direction of separation of these two components; the main direction of CO-mass outflow is nearly perpendicular to it. Within the conical nebula GGD18 near GL961 another pointlike IR-source has been found which seems to be the exciting source of this nebula.
In the framework of the ENVISAT validation programme, the first flight of the Michel-son Interferometer for Passive atmospheric sounding (MIPAS-B) in the tropics was performed from Teresina in Brazil ...( similar to 5 degree S) on 13-14 June 2005. Thanks to the stratospheric wind system governed by the quasi-biennial oscillation, a long boomerang flight could be established. This allowed, apart from the validation tasks, numerous dedicated scientific studies such as time-resolved measurements around sunrise, 3-D cloud surveys below 20 km, pointing at the outflow of convective systems, and fine sampling of the tropical tropopause layer. The measurements covered latitudes from the equator to about 10 degree S. The focus of the paper will be on the distribution and budget of nitrogen constituents and tracer correlations in comparison to 3-D chemistry model calculations. The relevance of the nitrogen chemistry in the tropics will be put into perspective with observations performed in middle and high latitudes. Tracer correlations will be discussed to illustrate the different behavior of transport and photochemistry in the tropics.
