Spatial and temporal distributions of NO2 and aerosols over the urban environment of Vienna during the VINDOBONA project (2017-2019)

2020 ◽  
Author(s):  
Stefan Schreier ◽  
Andreas Richter ◽  
Tim Bösch ◽  
Kezia Lange ◽  
Michael Revesz ◽  
...  
Keyword(s):  
Optimal Estimation ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Retrieval Algorithm ◽  
City Center ◽  
Near Surface ◽  
Urban Core ◽  
Spatial And Temporal Distributions ◽  
The City ◽  
Selection Of

<p>Within the scope of the VINDOBONA (VIenna horizontal aNd vertical Distribution OBservations Of Nitrogen dioxide and Aerosols) project, spectral UV/vis measurements at selected viewing directions are performed with three MAX-DOAS (Multi AXis Differential Optical Absorption Spectroscopy) instruments, which are located in the northeast, northwest, and south of the city center of Vienna, Austria. The selection of viewing directions of the three instruments was chosen in a way to provide data for the retrieval of horizontal and vertical trace gas and aerosol distributions, in particular over the urban core.</p><p>In the present work, the profile retrieval algorithm BOREAS (Bremen Optimal estimation REtrieval for Aerosols and trace gaseS) is used to retrieve aerosol and NO2 vertical profiles as well as accompanying parameters aerosol optical depth, tropospheric NO2 vertical columns (TVC NO2), and near-surface NO2 on days with cloudless conditions. The retrieval results are compared with co-located ceilometer, sun photometer, surface air quality, and TVC NO2 measurements, with the latter being obtained by applying the geometrical approximation and converting zenith-sky NO2 measurements.</p>

scholarly journals Parameterizing radiative transfer to convert MAX-DOAS dSCDs into near-surface box averaged mixing ratios and vertical profiles

2012 ◽  
Vol 5 (5) ◽  
pp. 7641-7673 ◽  
Author(s):  
R. Sinreich ◽  
A. Merten ◽  
L. Molina ◽  
R. Volkamer
Keyword(s):  
Boundary Layer ◽  
Radiative Transfer ◽  
Mexico City ◽  
Vertical Gradient ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Transfer Model ◽  
Model Calculations ◽  
Near Surface ◽  
Mixing Ratios

Abstract. We present a novel parameterization method to convert Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) differential Slant Column Densities (dSCDs) into near-surface box averaged volume mixing ratios. The approach is applicable inside the planetary boundary layer under conditions with significant aerosol load, does not require a-priori assumptions about the trace gas vertical distribution and builds on the increased sensitivity of MAX-DOAS near the instrument altitude. It parameterizes radiative transfer model calculations and significantly reduces the computational effort. The biggest benefit of this method is that the retrieval of an aerosol profile, which usually is necessary for deriving a trace gas concentration from MAX-DOAS dSCDs, is not needed. The method is applied to NO2 MAX-DOAS dSCDs recorded during the Mexico City Metropolitan Area 2006 (MCMA-2006) measurement campaign. The retrieved volume mixing ratios of two elevation angles (1° and 3°) are compared to volume mixing ratios measured by two long-path (LP)-DOAS instruments located at the same site. Measurements are found to agree well during times when vertical mixing is expected to be strong. However, inhomogeneities in the air mass above Mexico City can be detected by exploiting the different horizontal and vertical dimensions probed by MAX-DOAS measurements at different elevation angles, and by LP-DOAS. In particular, a vertical gradient in NO2 close to the ground can be observed in the afternoon, and is attributed to reduced mixing coupled with near surface emission. The existence of a vertical gradient in the lower 250 m during parts of the day shows the general challenge of sampling the boundary layer in a representative way and emphasizes the need of vertically resolved measurements.

scholarly journals Technical note: Evaluation of profile retrievals of aerosols and trace gases for MAX-DOAS measurements under different aerosol scenarios based on radiative transfer simulations

2021 ◽  
Vol 21 (17) ◽  
pp. 12867-12894
Author(s):  
Xin Tian ◽  
Yang Wang ◽  
Steffen Beirle ◽  
Pinhua Xie ◽  
Thomas Wagner ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Trace Gases ◽  
Optimal Estimation ◽  
Estimation Algorithm ◽  
Optical Absorption Spectroscopy ◽  
Limited Information ◽  
Inversion Algorithm ◽  
Vertical Column ◽  
Near Surface ◽  
Aerosol Pollution

Abstract. Ground-based Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a state-of-the-art remote sensing technique for deriving vertical profiles of trace gases and aerosols. However, MAX-DOAS profile inversions under aerosol pollution scenarios are challenging because of the complex radiative transfer and limited information content of the measurements. In this study, the performances of two inversion algorithms were evaluated for various aerosol pollution scenarios based on synthetic slant column densities (SCDs) derived from radiative transfer simulations. Compared to previous studies, in our study, much larger ranges of aerosol optical depth (AOD) and NO2 vertical column densities (VCDs) are covered. One inversion algorithm is based on optimal estimation; the other uses a parameterized approach. In this analysis, three types of profile shapes for aerosols and NO2 were considered: exponential, Boltzmann, and Gaussian. First, the systematic deviations of the retrieved aerosol profiles from the input profiles were investigated. For most cases, the AODs of the retrieved profiles were found to be systematically lower than the input values, and the deviations increased with increasing AOD. In particular for the optimal estimation algorithm and for high AOD, these findings are consistent with the results in previous studies. The assumed single scattering albedo (SSA) and asymmetry parameter (AP) have a systematic influence on the aerosol retrieval. However, for most cases the influence of the assumed SSA and AP on the retrieval results are rather small (compared to other uncertainties). For the optimal estimation algorithm, the agreement with the input values can be improved by optimizing the covariance matrix of the a priori uncertainties. Second, the aerosol effects on the NO2 profile retrieval were tested. Here, especially for the optimal estimation algorithm, a systematic dependence on the NO2 VCD was found, with a strong relative overestimation of the retrieved results for low NO2 VCDs and an underestimation for high NO2 VCDs. In contrast, the dependence on the aerosol profiles was found to be rather low. Interestingly, the results for both investigated wavelengths (360 and 477 nm) were found to be rather similar, indicating that the differences in the radiative transfer between both wavelengths have no strong effect. In general, both inversion schemes can retrieve the near-surface values of aerosol extinction and trace gas concentrations well.

scholarly journals Four years of ground-based MAX-DOAS observations of HONO and NO<sub>2</sub> in the Beijing area

2013 ◽  
Vol 13 (4) ◽  
pp. 10621-10660 ◽  
Author(s):  
F. Hendrick ◽  
J.-F. Müller ◽  
K. Clémer ◽  
M. De Mazière ◽  
C. Fayt ◽  
...  
Keyword(s):  
Seasonal Cycle ◽  
Surface Concentration ◽  
Early Morning ◽  
Optical Absorption Spectroscopy ◽  
Oh Radicals ◽  
Beijing City ◽  
City Center ◽  
Data Set ◽  
Near Surface ◽  
Local Noon

Abstract. Ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of nitrous acid (HONO) and its precursor NO2 (nitrogen dioxide) have been performed daily in Beijing city center (39.98° N, 116.38° E) from July 2008 to April 2009 and at the suburban site of Xianghe (39.75° N, 116.96° E) located ~ 60 km east of Beijing from March 2010 to December 2012. This extensive data set allowed for the first time the investigation of the seasonal cycle of HONO as well as its diurnal variation in and in the vicinity of a megacity. Our study was focused on the HONO and NO2 near-surface concentrations (0–200 m layer) and total vertical column densities (VCDs) retrieved by applying the Optimal Estimation Method to the MAX-DOAS observations. Monthly averaged HONO near-surface concentrations at local noon display a strong seasonal cycle with a maximum in late fall/winter (~ 0.8 and 0.7 ppb at Beijing and Xianghe, respectively) and a minimum in summer (~ 0.1 ppb at Beijing and 0.03 ppb at Xianghe). The seasonal cycles of HONO and NO2 appear to be highly correlated, with correlation coefficients in the 0.7–0.9 and 0.5–0.8 ranges at Beijing and Xianghe, respectively. The stronger correlation of HONO with NO2 and also with aerosols observed in Beijing suggests possibly larger role of NO2 conversion into HONO in the Beijing city center than at Xianghe. The observed diurnal cycle of HONO near-surface concentration shows a maximum in the early morning (about 1 ppb at both sites) likely resulting from night-time accumulation, followed by a decrease to values of about 0.1–0.4 ppb around local noon. The HONO/NO2 ratio shows a similar pattern with a maximum in the early morning (values up to 0.08) and a decrease to ~ 0.01–0.02 around local noon. The seasonal and diurnal cycles of the HONO near-surface concentration are found to be similar in shape and in relative amplitude to the corresponding cycles of the HONO total VCD and are therefore likely mainly driven by the balance between HONO sources and the photolytic sink, whereas dilution effects appear to play only a minor role. The estimation of OH radical production from HONO and O3 photolysis based on retrieved HONO near-surface concentrations and calculated photolysis rates indicate that HONO is by far the largest source of OH radicals in winter as well as in the early morning at all seasons, while the contribution of O3 dominates in summer from mid-morning until mid-afternoon.

scholarly journals Characterisation of Central-African aerosol and trace-gas emissions based on MAX-DOAS measurements and model simulations over Bujumbura, Burundi

2017 ◽  
Author(s):  
Clio Gielen ◽  
François Hendrick ◽  
Gaia Pinardi ◽  
Isabelle De Smedt ◽  
Caroline Fayt ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Forest Fires ◽  
Transport Model ◽  
Central Africa ◽  
Optimal Estimation ◽  
Trace Gas ◽  
Chemical Transport Model ◽  
Radiative Power ◽  
First Results ◽  
The City

Abstract. We present MAX-DOAS measurements of NO2, HCHO, and aerosols performed in Central Africa, in the city of Bujumbura, Burundi (3.38° S, 29.3° E). A MAX-DOAS instrument has been operated at this location by BIRA-IASB since late 2013. Aerosol-extinction and trace-gas vertical profiles are retrieved by applying the optimal-estimation-based profiling tool bePRO to the measured O4, NO2 and HCHO slant-column densities. The MAX-DOAS vertical columns and profiles are used for investigating the diurnal and seasonal cycles of NO2, HCHO, and aerosols. Regarding the aerosols, the retrieved AODs are compared to co-located AERONET sun-photometer measurements for verification purposes, while in the case of NO2 and HCHO, the MAX-DOAS vertical columns and profiles are compared to GOME-2 and OMI satellite observations. To characterise the biomass-burning and biogenic emissions in the Bujumbura region, the trace gases and aerosol MAX-DOAS retrievals are used in combination with MODIS fire radiative-power values and the tropospheric 3D chemical transport model IMAGES, as well as simulations from the NOAA backward-trajectory model HYSPLIT. The first results show that the aerosol and HCHO seasonal variation is driven by the alternation of rain and dry periods, the latter being associated with intense biomass-burning agricultural activities and forest fires in the south/south-east and transport from this region to Bujumbura. In contrast, NO2 is seen to depend mainly on local emissions close to the city, due to the short lifetime of this species (typically 1–2 hours).

Retrieval of vertical concentration profiles from OSIRIS UV–visible limb spectra

2002 ◽  
Vol 80 (4) ◽  
pp. 409-434 ◽  
Author(s):  
K Strong ◽  
B M Joseph ◽  
R Dosanjh ◽  
I C McDade ◽  
C A McLinden ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Optimal Estimation ◽  
Gas Absorption ◽  
Forward Model ◽  
Differential Optical Absorption Spectroscopy ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Vertical Profiles ◽  
Uv Visible

The OSIRIS instrument, launched on the Odin satellite in February 2001, includes an optical spectrograph that will record UV–visible spectra of sunlight scattered from the limb over a range of tangent heights. These spectra will be used to retrieve vertical profiles of ozone, NO2, OClO, BrO, NO3, O2, and aerosols, for the investigation of both stratospheric and mesospheric processes, particularly those related to ozone chemistry. In this work, the retrieval of vertical profiles of trace-gas concentrations from OSIRIS limb-radiance spectra is described. A forward model has been developed to simulate these spectra, and it consists of a single-scattering radiative-transfer model with partial spherical geometry, trace-gas absorption, Mie scattering by stratospheric aerosols, a Lambertian surface contribution, and OSIRIS instrument response and noise. Number-density profiles have been retrieved by using optimal estimation (OE) to combine an a priori profile with the information from sets of synthetic ``measurements''. For ozone, OE has been applied both to limb radiances at one or more discrete wavelengths and to effective-column abundances retrieved over a broad spectral range using differential optical absorption spectroscopy (DOAS). The results suggest that, between 15 and 35 km, ozone number densities can be retrieved to 10% accuracy or better on 1 and 2 km grids and to 5% on a 5 km grid. The combined DOAS-OE approach has also been used to retrieve NO2 number densities, yielding 13% accuracy or better for altitudes from 18 to 36 km on a 2 km grid. Differential optical absorption spectroscopy – optimal estimation retrievals of BrO and OClO reproduce the true profiles above 15 km in the noise-free case, but the quality of the retrievals is highly sensitive to noise on the simulated OSIRIS spectra because of the weak absorption of these two gases. The development of inversion methods for the retrieval of trace-gas concentrations from OSIRIS spectra is continuing, and a number of future improvements to the forward model and refinements of the retrieval algorithms are identified. PACS Nos.: 42.68Mj, 94.10Dy

scholarly journals Niche Analysis and Conservation of Bird Species Using Urban Core Areas

2021 ◽  
Vol 13 (11) ◽  
pp. 6327
Author(s):  
Vasilios Liordos ◽  
Jukka Jokimäki ◽  
Marja-Liisa Kaisanlahti-Jokimäki ◽  
Evangelos Valsamidis ◽  
Vasileios J. Kontsiotis
Keyword(s):  
Environmental Variables ◽  
Bird Species ◽  
Green Spaces ◽  
City Center ◽  
Ecological Requirements ◽  
Urban Core ◽  
Priority Species ◽  
Core Areas ◽  
The City ◽  
Eleven Species

Knowing the ecological requirements of bird species is essential for their successful conservation. We studied the niche characteristics of birds in managed small-sized green spaces in the urban core areas of southern (Kavala, Greece) and northern Europe (Rovaniemi, Finland), during the breeding season, based on a set of 16 environmental variables and using Outlying Mean Index, a multivariate ordination technique. Overall, 26 bird species in Kavala and 15 in Rovaniemi were recorded in more than 5% of the green spaces and were used in detailed analyses. In both areas, bird species occupied different niches of varying marginality and breadth, indicating varying responses to urban environmental conditions. Birds showed high specialization in niche position, with 12 species in Kavala (46.2%) and six species in Rovaniemi (40.0%) having marginal niches. Niche breadth was narrower in Rovaniemi than in Kavala. Species in both communities were more strongly associated either with large green spaces located further away from the city center and having a high vegetation cover (urban adapters; e.g., Common Chaffinch (Fringilla coelebs), European Greenfinch (Chloris chloris), Eurasian Blue Tit (Cyanistes caeruleus)) or with green spaces located closer to the city center and having high gray area cover and anthropogenic disturbance level (urban exploiters; e.g., Western Jackdaw (Corvus monedula), House Sparrow (Passer domesticus), Eurasian Magpie (Pica pica)). The eleven species that were common to both study areas similarly used the environmental variables and had similar niches, indicating that birds respond similarly to urbanization irrespective of latitude. Sixteen species in Kavala and eleven species in Rovaniemi were identified as conservation priority species, based on their niche specialization level and conservation status. The management actions proposed for the conservation of priority species will also benefit other species with similar ecological requirements and ultimately help maintain diverse bird communities in small-sized green spaces in urban core areas.

scholarly journals Technical Note: Temporal change in averaging kernels as a source of uncertainty in trend estimates of carbon monoxide retrieved from MOPITT

2013 ◽  
Vol 13 (22) ◽  
pp. 11307-11316 ◽  
Author(s):  
J. Yoon ◽  
A. Pozzer ◽  
P. Hoor ◽  
D. Y. Chang ◽  
S. Beirle ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Atmospheric Chemistry ◽  
Temporal Change ◽  
A Priori ◽  
Optimal Estimation ◽  
Technical Note ◽  
Retrieval Algorithm ◽  
Near Surface ◽  
Surface Level ◽  
Surface Carbon

Abstract. It has become possible to retrieve the global, long-term trends of trace gases that are important to atmospheric chemistry, climate, and air quality from satellite data records that span more than a decade. However, many of the satellite remote sensing techniques produce measurements that have variable sensitivity to the vertical profiles of atmospheric gases. In the case of constrained retrievals like optimal estimation, this leads to a varying amount of a priori information in the retrieval and is represented by an averaging kernel (AK). In this study, we investigate to what extent the estimation of trends from retrieved data can be biased by temporal changes of averaging kernels used in the retrieval algorithm. In particular, the surface carbon monoxide data retrieved from the Measurements Of Pollution In The Troposphere (MOPITT) instrument from 2001 to 2010 were analyzed. As a practical example based on the MOPITT data, we show that if the true atmospheric mixing ratio is continuously 50% higher or lower than the a priori state, the temporal change of the averaging kernel at the surface level gives rise to an artificial trend in retrieved surface carbon monoxide, ranging from −10.71 to +13.21 ppbv yr−1 (−5.68 to +8.84 % yr−1) depending on location. Therefore, in the case of surface (or near-surface level) CO derived from MOPITT, the AKs trends multiplied by the difference between true and a priori states must be quantified in order to estimate trend biases.

scholarly journals PENINGKATAN VISIBILITAS BANGUNAN LAMA, STUDI KASUS JALAN KREMBANGAN BARAT SURABAYA

2020 ◽  
Vol 1 (2) ◽  
pp. 167-179
Author(s):  
Setyo Nugroho
Keyword(s):  
Built Environment ◽  
Vegetation Type ◽  
City Center ◽  
The City ◽  
New Buildings ◽  
Vision Technique ◽  
Selection Of ◽  
Main Factor ◽  
Technique Analysis

Title: The Improvement of Old Building Visibility, Krembangan Barat Street of Surabaya as of Case Study High development in the City center forces old building losing its existence. The main factor old buildings losing its existences are the lack of skyline guideline (new buildings obstruct the view toward old buildings), the changes of traffic direction, and the selection of vegetation type. This paper discusses a brief evaluation of old building visibility through visual experiences, and gives a schematic design as proposal for jalan Krembangan Barat. Serial vision technique analysis is addressed in order to gain the visual and spatial experiences of the built environment. Result shows that three spots of place should be improved in order to perceive the visibility by rehabilitating, adaptive re-using, and providing pedestrian ways to connect one potential spot to others in the corridor of Krembangan Barat.

scholarly journals Horizontal distribution of tropospheric NO<sub>2</sub> and aerosols derived by dual-scan multi-wavelength MAX-DOAS measurements in Uccle, Belgium

2021 ◽  
Author(s):  
Ermioni Dimitropoulou ◽  
Francois Hendrick ◽  
Martina Michaela Friedrich ◽  
Frederik Tack ◽  
Gaia Pinardi ◽  
...  
Keyword(s):  
A Priori ◽  
Elevation Angle ◽  
Optimal Estimation ◽  
Horizontal Distribution ◽  
Optical Absorption Spectroscopy ◽  
Azimuthal Direction ◽  
Vertical Column ◽  
Near Surface ◽  
Multi Wavelength

Abstract. Dual-scan ground-based Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of tropospheric nitrogen dioxide (NO2) and aerosols have been carried out in Uccle (50.8° N, 4.35° E; Brussels region, Belgium) for two years, from March 2018 to February 2020. The MAX-DOAS instrument has been operating in both UV and Visible wavelength ranges in a dual-scan configuration consisting of two sub-modes: (1) an elevation scan in a fixed viewing azimuthal direction and (2) an azimuthal scan in a fixed low elevation angle (2°). By analyzing the O4 and NO2 dSCDs at six different wavelength intervals along every azimuthal direction and by applying a new Optimal-Estimation-based inversion approach, the horizontal distribution of the NO2 near-surface concentrations and vertical column densities (VCDs) and the aerosols near-surface extinction coefficient are retrieved along ten azimuthal directions. The retrieved horizontal NO2 concentration profiles allow the identification of the main NO2 hotspots in the Brussels area. Correlative comparisons of the retrieved horizontal NO2 distribution have been conducted with airborne, mobile, and satellite datasets, and overall a good agreement is found. The comparison with TROPOMI observations reveals that the characterization of the horizontal distribution of tropospheric NO2 VCDs by ground-based measurements, the appropriate sampling of TROPOMI pixels, and an adequate a priori NO2 profile shape in TROPOMI retrievals lead to a better consistency between satellite and ground-based datasets.

scholarly journals Retrieval of nitrogen dioxide stratospheric profiles from ground-based zenith-sky UV-visible observations: validation of the technique through correlative comparisons

2004 ◽  
Vol 4 (3) ◽  
pp. 2867-2904 ◽  
Author(s):  
F. Hendrick ◽  
B. Barret ◽  
M. Van Roozendael ◽  
H. Boesch ◽  
A. Butz ◽  
...  
Keyword(s):  
Estimation Method ◽  
Optimal Estimation ◽  
Optical Absorption Spectroscopy ◽  
Retrieval Algorithm ◽  
Data Sets ◽  
Vertical Distributions ◽  
Uv Visible ◽  
Polar Ozone ◽  
Better Than ◽  
Good Agreement

Abstract. A retrieval algorithm based on the Optimal Estimation Method (OEM) has been developed in order to provide vertical distributions of NO2 in the stratosphere from ground-based (GB) zenith-sky UV-visible observations. It has been applied to observational data sets from the NDSC (Network for Detection of Stratospheric Change) stations of Harestua (60° N, 10° E) and Andøya (69.3° N, 16.1° E) in Norway. The information content and retrieval errors have been analyzed following a formalism used for characterizing ozone profiles retrieved from solar infrared absorption spectra. In order to validate the technique, the retrieved NO2 vertical profiles and columns have been compared to correlative balloon and satellite observations. Such extensive validation of the profile and column retrievals was not reported in previously published work on the profiling from GB UV-visible measurements. A good agreement – generally better than 25% – has been found with the SAOZ (Système d'Analyse par Observations Zénithales) and DOAS (Differential Optical Absorption Spectroscopy) balloon data. A similar agreement has been reached with correlative satellite data from HALogen Occultation Experiment (HALOE) and Polar Ozone and Aerosol Measurement (POAM) III instruments above 25 km of altitude. Below 25 km, a systematic overestimation of our retrieved profiles – by up to 50% in some cases – has been observed by both HALOE and POAM III, pointing out the limitation of the satellite solar occultation technique at these altitudes. We have concluded that our study strengthens our confidence in the reliability of the retrieval of vertical distribution information from GB UV-visible observations and offers new perspectives in the use of GB UV-visible network data for validation purposes.

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