Top PDF An improved NO<sub>2</sub> retrieval for the GOME-2 satellite instrument

An improved NO<sub>2</sub> retrieval for the GOME-2 satellite instrument

An improved NO<sub>2</sub> retrieval for the GOME-2 satellite instrument

and also to better results than obtained using only the liquid water cross-section. In Fig. 7, the retrieved fit coefficients are shown for the sand signal in GOME-2 data from August 2007. As expected, the largest signals are found over deserts in Africa and Australia, but other regions with bare soil can also be detected, for example in the Canadian Arctic. Higher values are also observed over the ocean close to the estuary

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An improved tropospheric NO<sub>2</sub> retrieval for satellite observations in the vicinity of mountainous terrain

An improved tropospheric NO<sub>2</sub> retrieval for satellite observations in the vicinity of mountainous terrain

with corresponding columns deduced from ground-based in situ observations over the Swiss plateau and the Po Valley illustrates the promise of our new retrieval. It partially reduces the underestimation of the OMI VTCs at polluted sites in winter and fall and generally improves the agreement in terms of slope and correlation at rural stations. It does not solve, however, the issue that the OMI DOMINO product tends to overestimate

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Analysing spatio-temporal patterns of the global NO<sub>2</sub>-distribution retrieved from GOME satellite observations using a generalized additive model

Analysing spatio-temporal patterns of the global NO<sub>2</sub>-distribution retrieved from GOME satellite observations using a generalized additive model

covering the wavelength range between 240 and 790 nm with moderate spectral res- olutions. While GOME was primarily designed for the observation of the ozone layer, in addition, many other trace gases can be also analysed from the spectra, several of them for the first time from space (e.g. Burrows et al., 1999). The satellite oper- ates in a nearly polar, sun-synchronous orbit at an altitude of 780 km with an equator

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Error correlation between CO<sub>2</sub> and CO as constraint for CO<sub>2</sub> flux inversions using satellite data

Error correlation between CO<sub>2</sub> and CO as constraint for CO<sub>2</sub> flux inversions using satellite data

Components of the observational errors are not strictly in- dependent. We will simplify here by ignoring their covari- ance. The error variances add quadratically (if the errors are independent). The instrument error includes measure- ment noise and retrieval error (Engelen et al., 2002, 2006). Smoothing error introduced by the averaging kernels of the satellite instrument is a source of retrieval error, but can be canceled by smoothing the CTM profiles with the same av- eraging kernels (Jones et al., 2003; Heald et al., 2004). For- ward model error is the dominant source of observational er- ror for CO observations from space (Heald et al., 2004) and may be dominant for CO 2 observations depending on data
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Simultaneous measurements of OClO, NO<sub>2</sub> and O<sub>3</sub> in the Arctic polar vortex by the GOMOS instrument

Simultaneous measurements of OClO, NO<sub>2</sub> and O<sub>3</sub> in the Arctic polar vortex by the GOMOS instrument

The first measurements of OClO in the stratosphere were performed in Antarctica by Solomon et al. (1987) from a ground-based station. Since then, other measurements have been performed by using ground-based (Miller et al., 1999), balloon-borne (Canty et al., 2005; Pommereau and Piquard, 1994; Renard et al., 1997; Riviere et al., 2003) or satel- lite measurements (Krecl et al., 2006; Wagner et al., 2002). However, the measurements performed using ground-based instruments do not allow the retrieval of vertical distribu- tions. Furthermore, like balloon-borne measurements, they are localised and do not give a global coverage. Some of these satellite instruments used a nadir geometry to re- trieve the total vertical column densities of OClO: this is the case for Global Ozone Monitoring Experiment (GOME) on ERS-2 (Burrows et al., 1999), SCanning Imaging Absorp- tion spectroMeter for Atmospheric CHartographY (SCIA- MACHY) onboard ENVISAT (Bovensmann et al., 1999) and Ozone Monitoring Instrument (OMI) on EOS-Aura (Levelt et al., 2006). The instrument Optical Spectrograph and In- fraRed Imager System (OSIRIS) onboard the Odin satellite (Llewellyn et al., 2004) uses the limb scattering technique to retrieve vertical profiles of concentrations of OClO (Krecl et al., 2006). Moreover, SCIAMACHY has a limb-viewing mode and can also retrieve such vertical profiles. All these satellite perform daytime measurements. However, no re- sults have been published for the moment. Note that the Stratospheric Aerosol and Gas Experiment III (SAGE III) on the Meteor-3M satellite (McCormick et al., 1991) could also perform lunar occultations and limb-scatter measure- ments in order to retrieve OClO vertical distributions but, for the moment, no results concerning this have been pub- lished. The Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument on ENVISAT (see e.g., Bertaux et al., 1991; Kyr¨ol¨a et al., 2004) is designed to retrieve the vertical concentrations of trace gases, including nighttime OClO. The stellar occultation technique used by GOMOS al- lows the measurements of OClO during nighttime. GOMOS is the only satellite instrument able to perform such nighttime measurements in the stratosphere. Preliminary results for the year 2003 have suggested the presence of a maximum in the OClO concentration in the equatorial upper stratosphere (Fussen et al., 2006). For the moment, the OClO product ob- tained from the GOMOS spectra has not been validated with data from other instruments. Even if these OClO measure- ments are not validated, this article highlights the capabilities of GOMOS to ensure a global monitoring of OClO and NO 2
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A new stratospheric and tropospheric NO<sub>2</sub> retrieval algorithm for nadir-viewing satellite instruments: applications to OMI

A new stratospheric and tropospheric NO<sub>2</sub> retrieval algorithm for nadir-viewing satellite instruments: applications to OMI

air mass factors are the same as those used in the retrieval. Figure 5a and c illustrate stratospheric and tropospheric re- trievals, respectively, in an unmasked (clean) part of the east- ern Pacific. The retrieved stratospheric vertical column (red curve in Fig. 5a) is biased high because the simulated tropo- spheric data were intentionally made 50 % larger than the a priori troposphere in the unmasked regions. This bias affects the retrieved stratosphere via the second term in Eq. (25). Figure 5c shows the corresponding tropospheric retrieval. As expected from Eq. (27), the retrieval (red) follows the a priori (blue) rather than the true data (black), on average. However, it is evident that some of the smaller-scale differential struc- ture in the original data is preserved in the retrieval.
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First quantitative bias estimates for tropospheric NO<sub>2</sub> columns retrieved from SCIAMACHY, OMI, and GOME-2 using a common standard

First quantitative bias estimates for tropospheric NO<sub>2</sub> columns retrieved from SCIAMACHY, OMI, and GOME-2 using a common standard

Boersma, K. F., Eskes, H. J., Dirksen, R. J., van der A, R. J., Veefkind, J. P., Stammes, P., Huijnen, V., Kleipool, Q. L., Sneep, M., Claas, J., Leit ˜a o, J., Richter, A., Zhou, Y., and Brun- ner, D.: An improved tropospheric NO 2 column retrieval algorithm for the Ozone Monitoring Instrument, Atmos. Meas. Tech., 4, 1905–1928, doi:10.5194/amt-4-1905-2011, 2011. Bovensmann, H., Burrows, J. P., Buchwitz, M., Frerick, J., Noel, S., Rozanov, V. V., Chance,

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The CU mobile Solar Occultation Flux instrument: structure functions and emission rates of NH<sub>3</sub>, NO<sub>2</sub> and C<sub>2</sub>H<sub>6</sub>

The CU mobile Solar Occultation Flux instrument: structure functions and emission rates of NH<sub>3</sub>, NO<sub>2</sub> and C<sub>2</sub>H<sub>6</sub>

For measurements from the mobile laboratory the azimuth and elevation angles change rapidly over the course of an RD. It is therefore important to characterize the ILS (Hase et al., 1999) over a wide range of azimuth and elevation angle pairs. This was tested in a laboratory setup where the solar tracker was pointed at a globar to observe atmospheric water vapor over a distance of several meters along the path between the FTS and the globar. The light emitted by the globar is col- limated and directed onto the solar tracker. The FTS with solar tracker is positioned on a rotatable platform. The ILS has been determined using the retrieval code LINEFIT (Hase et al., 1999) version 14 using water vapor absorption lines in the spectral range at 1950–1900 for the InSb and at 1820– 1800 cm −1 for the MCT detector. The modulation efficiency at maximum OPD is shown in Fig. 4 for different azimuthal and elevation angles, and the results are further discussed in Sect. 3.1.2 and Table 4.
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Retrieval algorithm for CO<sub>2</sub> and CH<sub>4</sub> column abundances from short-wavelength infrared spectral observations by the Greenhouse Gases Observing Satellite

Retrieval algorithm for CO<sub>2</sub> and CH<sub>4</sub> column abundances from short-wavelength infrared spectral observations by the Greenhouse Gases Observing Satellite

priori, and its variance was calculated for each month and grid box of GPV data. An a priori value of unity and variance of (0.05) 2 are used for the radiance adjustment factor. As stated above, aerosol scattering modifies the equivalent optical path length, which may lead to large errors in the retrieved column amounts. To represent the equiva- lent optical path modification, AOD and the surface pressure are included in the state

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Retrieval of near-surface sulfur dioxide (SO<sub>2</sub>) concentrations at a global scale using IASI satellite observations

Retrieval of near-surface sulfur dioxide (SO<sub>2</sub>) concentrations at a global scale using IASI satellite observations

strong ones are known. While this could be explained by an artefact of the calcu- lated HRI due to sand emissivity, which strongly affects the thermal infrared measure- ments, it is noteworthy that the issue is not observed similarly above other deserts. For instance, in Fig. 7 we compare the distribution of measured HRI and the to- tal column of H 2 O for three desert regions: the Sahara, the center of Australia and

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A method for improved SCIAMACHY CO<sub>2</sub> retrieval in the presence of optically thin clouds

A method for improved SCIAMACHY CO<sub>2</sub> retrieval in the presence of optically thin clouds

Within the parameter vector we define that scattering at particles takes place in a plane parallel geometry at one cloud layer with a geometrical thickness of 0.5 km homo- geneously consisting of fractal ice crystals with 50 µm ef- fective radius. In addition, scattering happens at a stan- dard LOWTRAN summer aerosol profile with moderate ru- ral aerosol load and Henyey-Greenstein phase function and a total aerosol optical thickness of about 0.136 at 750 nm and 0.038 at 1550 nm. Both cloud parameters are aimed at opti- cally thin cirrus clouds because on the one hand it is not pos- sible to get enough information from below an optically thick cloud and on the other hand the foregoing cloud screening fil- ters already the optically thick clouds. Additionally, Schneis- ing et al. (2008) found that thin cirrus clouds are most likely the reason for shortcoming of the WFM-DOAS 1.0 CO 2 re-
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A comparison of DOAS observations by the CARIBIC aircraft and the GOME-2 satellite of the 2008 Kasatochi volcanic SO<sub>2</sub> plume

A comparison of DOAS observations by the CARIBIC aircraft and the GOME-2 satellite of the 2008 Kasatochi volcanic SO<sub>2</sub> plume

The retrieval of the aerosol optical properties is addressed and external information is included, however the influence of the aerosols on the O 4 slant column is outweighed by a large [r]

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An aircraft based three channel broadband cavity enhanced absorption spectrometer for simultaneous measurements of NO<sub>3</sub>, N<sub>2</sub>O<sub>5</sub> and NO<sub>2</sub>

An aircraft based three channel broadband cavity enhanced absorption spectrometer for simultaneous measurements of NO<sub>3</sub>, N<sub>2</sub>O<sub>5</sub> and NO<sub>2</sub>

Eq. (1). However, resultant improvements in detection limits are offset by an increase in noise associated with fewer photons arriving at the detector per unit time due to the ac- companying reduction in light intensity transmitted through the cavity which is roughly proportional to 1 − R(λ). Sensitivity can also be improved by using a more luminous light source. This is because signal increases proportionally to the number of photons

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On the improvement of NO<sub>2</sub> satellite retrievals – aerosol impact on the airmass factors

On the improvement of NO<sub>2</sub> satellite retrievals – aerosol impact on the airmass factors

by 10% from 425 to 450 nm. This variation is relatively small and will largely cancel if it is linear with wavelength but might be relevant in some cases. For different solar zenith angles (SZA), the general trend shows that the AMF increases for higher sun, but for specific cases, this tendency can also be reverted. In some circumstances (not presented here), when considering fine aerosol, a decrease occurs with high sun, and

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Influence of the substrate on the overall sensor impedance of planar H<sub>2</sub> sensors involving TiO<sub>2</sub>–SnO<sub>2</sub> interfaces

Influence of the substrate on the overall sensor impedance of planar H<sub>2</sub> sensors involving TiO<sub>2</sub>–SnO<sub>2</sub> interfaces

As revealed by Figs. 5 and 6 , the substrate (glass) conduc- tivity of a type-A sensor is about 100 times higher than that of the measurement environment at the same temperatures. Fig- ure 7 demonstrates that the type-B substrate (insulated glass) leads to a slightly higher shunt conductance (parallel to the coated IDT) than the test bed alone. This means that the test bed influence can be neglected for “high-conductivity” sub- strates as in type-A sensors, but must be taken into account with “low-conductivity” substrates as in type-B sensors.
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The European CO<sub>2</sub>, CO, CH<sub>4</sub> and N<sub>2</sub>O balance between 2001 and 2005

The European CO<sub>2</sub>, CO, CH<sub>4</sub> and N<sub>2</sub>O balance between 2001 and 2005

Fig. 1. Spatial extent of the region under study including: Albania (ALB), Austria (AUT), Belgium (BEL), Bosnia and Herzegovina (BIH), Bulgaria (BGR), Croatia (HRV), Cyprus (CYP), Czech Republic (CZE), Denmark (DNK), Estonia (EST), Finland (FIN), France (FRA), Germany (DEU), Greece (GRC), Hungary (HUN), Iceland (ISL), Ireland (IRL), Italy (ITA), Kosovo (UNK), Latvia (LVA), Lithuania (LTU), Luxembourg (LUX), Macedonia (MKD), Malta (MLT), the Nether- lands (NLD), Norway (NOR), Poland (POL), Portugal (PRT), Romania (ROU), Serbia and Montenegro (SCG), Slovakia (SVK), Slovenia (SVN), Spain (ESP), Sweden (SWE), Switzer- land (CHE) and United Kingdom (GBR)
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Technical Note: Feasibility of CO<sub>2</sub> profile retrieval from limb viewing solar occultation made by the ACE-FTS instrument

Technical Note: Feasibility of CO<sub>2</sub> profile retrieval from limb viewing solar occultation made by the ACE-FTS instrument

on temperature. In fact, it may be shown that for a micro-window corresponding to a CO 2 line with a low value of the lower state energy E ”, there exists a tangent height at which the temperature Jacobian is almost equal to zero (Park, 1997) and the sign of the temperature Jacobian is positive above this critical altitude and negative below. Finally, spectral regions for which radiative transfer model is not relevant are rejected.

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Comparisons of continuous atmospheric CH<sub>4</sub>, CO<sub>2</sub> and N<sub>2</sub>O measurements &ndash; results from a travelling instrument campaign at Mace Head

Comparisons of continuous atmospheric CH<sub>4</sub>, CO<sub>2</sub> and N<sub>2</sub>O measurements &ndash; results from a travelling instrument campaign at Mace Head

of 0.01–0.04 µmol mol −1 compared to the dry G2301 instru- ment. The calibration suite of the CRDS systems consists of four cylinders filled with synthetic gas mixture by Deuste Steininger (Mühlhausen, Germany). They were calibrated by the MPI-BGC GasLab in Jena using CRDS. The two CRDS instruments are routinely calibrated once per month, accord- ing to a calibration sequence where each standard is mea- sured four times for 20 min (the first 10 minutes are not used to calculate the response function since they still incorpo- rate a settling-in effect). The measurement interval is 5 s. The sample flow rate is about 0.3 slpm at about 1 bar absolute pressure. In this study we will use hourly aggregates for the intercomparison, since the data is computed and stored like this in the common database.
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Five years of CO, HCN, C<sub>2</sub>H<sub>6</sub>, C<sub>2</sub>H<sub>2</sub>, CH<sub>3</sub>OH, HCOOH and H<sub>2</sub>CO total columns measured in the Canadian high Arctic

Five years of CO, HCN, C<sub>2</sub>H<sub>6</sub>, C<sub>2</sub>H<sub>2</sub>, CH<sub>3</sub>OH, HCOOH and H<sub>2</sub>CO total columns measured in the Canadian high Arctic

In contrast to these measurements, the ground-based FTIR technique can provide total columns, with good sensitiv- ity in the lower troposphere (compared to satellite measure- ments), as well as long-term spectral acquisition, in clear- sky conditions, thereby enabling an assessment of the tem- poral variabilities of the target species in the high Arctic (compared to campaign-based measurements). We focused on these species because there remain numerous gaps in the available observational data sets, especially at high latitudes. Furthermore, the transport and the degradation mechanisms of non-methane hydrocarbons (NMHCs) are poorly under- stood and should be better quantified in order to increase our ability to predict trace gas concentrations and variability in models (Stavrakou et al., 2009).
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Atmospheric homogeneous nucleation of H<sub>2</sub>SO<sub>4</sub> and H<sub>2</sub>O

Atmospheric homogeneous nucleation of H<sub>2</sub>SO<sub>4</sub> and H<sub>2</sub>O

et al., 2008), and recently we have redesigned the nucleation reactor (Fig. 1) to in- crease the range of residence times (50 – 240 s). In the present study, we report the results taken with both this new and old nucleation reactors, to understand how different residence times affect nucleation rates and processes. The new nucleation reactor was designed to reduce wall loss of aerosol precursors significantly, by using a larger diam-

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