The horizontal resolution of MIPAS

Limb remote sensing from space provides atmospheric composition measurements at high vertical resolution while the information is smeared in the horizontal domain. The horizontal components of two-dimensional (altitude and along-track coordinate) averaging kernels of a limb retrieval constrained to horizontal homogeneity can be used to estimate the horizontal resolution of limb retrievals. This is useful for comparisons of measured data with modeled data, to construct horizontal observation operators in data assimilation applications or when measurements of different horizontal resolution are intercompared. We present these averaging kernels for retrievals of temperature, H2O, O3, CH4, N2O, HNO3 and NO2 from MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) high-resolution limb emission spectra. The horizontal smearing of a MIPAS retrieval in terms of full width at half maximum of the rows of the horizontal averaging kernel matrix varies typically between about 200 and 350 km for most species, altitudes and atmospheric conditions. The range where 95% of the information originates from varies from about 260 to 440 km for these cases. This information spread is smaller than the MIPAS horizontal sampling, i.e. MIPAS data are horizontally undersampled, and the effective horizontal resolution is driven by the sampling rather than the smearing. The point where the majority of the information originates from is displaced from the tangent point towards the satellite by typically less than 10 km for trace gas profiles and about 50 to 100 km for temperature, with a few exceptions for uppermost altitudes. The geolocation of a MIPAS profile is defined as the tangent point of the middle line of sight in a MIPAS limb scan. The majority of the information displacement with respect to this nominal geolocation of the measurement is caused by the satellite movement and the geometrical displacement of the actual tangent point as a function of the elevation angle

Impacts of meteoric sulfur in the Earth's atmosphere

A meteoric sulfur input function and a sulfur ion chemistry scheme have been incorporated into a chemistry-climate model, in order to study the speciation of sulfur between the stratosphere and the thermosphere (~20 – 120 km), and the impact of the sulfur input from ablation of cosmic dust. The simulations have been compared to rocket observations of SO+ between 85 and 110 km, MIPAS observations of SO2 between 20 and 45 km, and stratospheric balloon-borne measurements of H2SO4 vapor and sulfate aerosol. These observations constrain the present day global flux of meteoric sulfur to ≤ 1.0 t S d-1, i.e. 2 orders of magnitude smaller than the flux of S into the stratosphere from OCS photo-oxidation and explosive volcanic SO2 injection. However, the meteoric sulfur flux is strongly focused into the polar vortices by the meridional circulation, and therefore the contribution of SO2 of meteoric origin to the polar upper stratosphere during winter is substantial (~ 30% at 50 km for a flux of 1.0 t S d-1). The Antarctic spring sulfate aerosol layer is found to be very sensitive to a moderate increase of the input rate of meteoric sulfur, showing a factor of 2 enhancement in total sulfate aerosol number density at 30 km for an input of 3.0 t S d-1. The input rate estimate of 1.0 t S d-1 suggests an enrichment of sodium relative to sulfur of 2.7 ± 1.5 and is consistent with a total cosmic dust input rate of 44 t d-1

Limitations of Near Edge X Ray Absorption Fine Structure as a tool for observing conduction bands in chalcopyrite solar cell heterojunctions

A non optimized interface band alignment in a heterojunctionbased solar cell can have negative eff ects on the current and voltage characteristics of the resulting device. To evaluate the use of Near Edge X ray Absorption Fine Structure spectroscopy NEXAFS as a means to measure the conduction band position, Cu In,Ga S2 chalcopyrite thin film surfaces were investigated as these form the absorber layer in solar cells with the structure ZnO Buffer Cu In,Ga S2 Mo Glass. The composition dependence of the structure of the conduction bands of CuInxGa1 xS2 has been revealed for x 0, 0.67 and 1 with both hard and soft NEXAFS and the resulting changes in conduction band off set at the junction with the bu ffer layer discussed. A comprehensive study of the positions of the absorption edges of all elements was carried out and the development of the conduction band with Ga content was observed, also with respect to calculated densities of state

Intercomparison of ILAS-II version 1.4 and version 2 target parameters with MIPAS-Envisat measurements

This paper assesses the mean differences between the two ILAS-II data versions (1.4 and 2) by comparing them with MIPAS measurements made between May and October 2003. For comparison with ILAS-II results, MIPAS data processed at the Institut für Meteorologie und Klimaforschung, Karlsruhe, Germany (IMK) in cooperation with the Instituto de Astrofísica de Andalucía (IAA) in Granada, Spain, were used. The coincidence criteria of ±300 km in space and ±12 h in time for H<sub>2</sub>O, N<sub>2</sub>O, and CH<sub>4</sub> and the coincidence criteria of ±300 km in space and ±6 h in time for ClONO<sub>2</sub>, O<sub>3</sub>, and HNO<sub>3</sub> were used. The ILAS-II data were separated into sunrise (= Northern Hemisphere) and sunset (= Southern Hemisphere). For the sunrise data, a clear improvement from version 1.4 to version 2 was observed for H<sub>2</sub>O, CH<sub>4</sub>, ClONO<sub>2</sub>, and O<sub>3</sub>. In particular, the ILAS-II version 1.4 mixing ratios of H<sub>2</sub>O and CH<sub>4</sub> were unrealistically small, and those of ClONO<sub>2</sub> above altitudes of 30 km unrealistically large. For N<sub>2</sub>O and HNO<sub>3</sub>, there were no large differences between the two versions. Contrary to the Northern Hemisphere, where some exceptional profiles deviated significantly from known climatology, no such outlying profiles were found in the Southern Hemisphere for both versions. Generally, the ILAS-II version 2 data were in better agreement with the MIPAS data than the version 1.4, and are recommended for quantitative analysis in the stratosphere. For H<sub>2</sub>O data in the Southern Hemisphere, further data quality evaluation is necessary

Carbon monoxide distributions from the upper troposphere to the mesosphere inferred from 4.7 μm non-local thermal equilibrium emissions measured by MIPAS on Envisat

We present global distributions of carbon monoxide (CO) from the upper troposphere to the mesosphere observed by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat. Vertically resolved volume mixing ratio profiles have been retrieved from 4.7 μm limb emission spectra under consideration of non-local thermodynamic equilibrium. The precision of individual CO profiles is typically 5–30 ppbv (15–40% for altitudes greater than 40 km and lower than 15 km and 30–90% within 15–40 km). Estimated systematic errors are in the order of 8–15%. Below 60 km, the vertical resolution is 4–7 km. The data set which covers 54 days from September 2003 to March 2004 has been derived with an improved retrieval version including (i) the retrieval of log(vmr), (ii) the consideration of illumination-dependent vibrational population gradients along the instrument's line of sight, and (iii) joint-fitted vmr horizontal gradients in latitudinal and longitudinal directions. A detailed analysis of spatially resolved CO distributions during the 2003/2004 Northern Hemisphere major warming event demonstrate the potential of MIPAS CO observations to obtain new information on transport processes during dynamical active episodes, particularly on those acting in the vertical. From the temporal evolution of zonally averaged CO abundances, we derived extraordinary polar winter descent velocities of 1200 m per day inside the recovered polar vortex in January 2004. Middle stratospheric CO abundances show a well established correlation with the chemical source CH<sub>4</sub>, particularly in the tropics. In the upper troposphere, a moderate CO decrease from September 2003 to March 2004 was observed. Upper tropospheric CO observations provide a detailed picture of long-range transport of polluted air masses and uplift events. MIPAS observations taken on 9–11 September 2003 confirm the trapping of convective outflow of polluted CO-rich air from Southeast Asia into the Asian monsoon anticyclone, which has been described in previous studies. Upper tropospheric CO plumes, observed by MIPAS on this day, were predominantly located in the Northern Hemisphere. Most of these plumes could be related to Southeast Asian pollution by means of backward trajectory calculations. During 20–22 October, southern hemispheric biomass burning was the most likely source of the major CO plumes observed over the Southern Atlantic and Indian Ocean