scholarly journals Determination of an effective trace gas mixing height by differential optical absorption spectroscopy (DOAS)

2009 ◽  
Vol 2 (4) ◽  
pp. 1663-1692 ◽  
Author(s):  
B. Zhou ◽  
S. N. Yang ◽  
S. S. Wang ◽  
T. Wagner
Keyword(s):  
Trace Gases ◽  
Mixing Layer ◽  
Correlation Coefficients ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Gas Mixing ◽  
Mixing Height ◽  
Free Atmosphere ◽  
Layer Height

Abstract. A new method for the determination of the Mixing layer Height (MH) by the DOAS technique is proposed in this article. The MH can be retrieved by a combination of active DOAS and passive DOAS observations of atmospheric trace gases; here we focus on observations of NO2. Because our observations are sensitive to the vertical distribution of trace gases, we refer to the retrieved layer height as an ''effective trace gas mixing height'' (ETMH). By analyzing trace gas observations in Shanghai over one year (1017 hourly means in 93 days in 2007), the retrieved ETMH was found to range between 0.1 km and 2.8 km (average is 0.78 km); more than 90% of the measurements yield an ETMH between 0.2 km and 2.0 km. The seasonal and diurnal variation of the ETMH shows good agreement with mixing layer heights derived from meteorological observations. We investigated the relationship of the derived ETMH to temperature and wind speed and found correlation coefficients of 0.65 and 0.37, respectively. Also the wind direction has an impact on the measurement to some extent. Especially in cases when the air flow comes from highly polluted areas and the atmospheric lifetime of NO2 is long (e.g. in winter), the NO2 concentration at high altitudes over the measurement site can be enhanced, which leads to an overestimation of the ETMH. Enhanced NO2 concentrations in the free atmosphere and heterogeneity within the mixing layer can cause additional uncertainties. Our method could be easily extended to other species like e.g. SO2, HCHO or Glyoxal. Simultaneous studies of these molecules could yield valuable information on their respective atmospheric lifetimes.

scholarly journals Determination of the mixing layer height from regular lidar measurements in the Barcelona area

2004 ◽  
Author(s):  
Michael Sicard ◽  
Carlos Perez ◽  
Adolfo Comeren ◽  
Jose M. Baldasano ◽  
Francesc Rocadenbosch
Keyword(s):  
Mixing Layer ◽  
Layer Height ◽  
Lidar Measurements ◽  
Mixing Layer Height

scholarly journals Doppler Lidar Observations of the Mixing Height in Indianapolis Using an Automated Composite Fuzzy Logic Approach

2018 ◽  
Vol 35 (3) ◽  
pp. 473-490 ◽  
Author(s):  
Timothy A. Bonin ◽  
Brian J. Carroll ◽  
R. Michael Hardesty ◽  
W. Alan Brewer ◽  
Kristian Hajny ◽  
...  
Keyword(s):  
Fuzzy Logic ◽  
Mixing Layer ◽  
Horizontal Wind ◽  
Doppler Lidar ◽  
Mixing Height ◽  
Layer Height ◽  
Fuzzy Logic Approach ◽  
Mixing Layer Height ◽  
Logic Approach ◽  
The Mean

AbstractA Halo Photonics Stream Line XR Doppler lidar has been deployed for the Indianapolis Flux Experiment (INFLUX) to measure profiles of the mean horizontal wind and the mixing layer height for quantification of greenhouse gas emissions from the urban area. To measure the mixing layer height continuously and autonomously, a novel composite fuzzy logic approach has been developed that combines information from various scan types, including conical and vertical-slice scans and zenith stares, to determine a unified measurement of the mixing height and its uncertainty. The composite approach uses the strengths of each measurement strategy to overcome the limitations of others so that a complete representation of turbulent mixing is made in the lowest km, depending on clouds and aerosol distribution. Additionally, submeso nonturbulent motions are identified from zenith stares and removed from the analysis, as these motions can lead to an overestimate of the mixing height. The mixing height is compared with in situ profile measurements from a research aircraft for validation. To demonstrate the utility of the measurements, statistics of the mixing height and its diurnal and annual variability for 2016 are also presented. The annual cycle is clearly captured, with the largest and smallest afternoon mixing heights observed at the summer and winter solstices, respectively. The diurnal cycle of the mixing layer is affected by the mean wind, growing slower in the morning and decaying more rapidly in the evening with lighter winds.

scholarly journals Direct observation of two dimensional trace gas distribution with an airborne Imaging DOAS instrument

2008 ◽  
Vol 8 (3) ◽  
pp. 11879-11907 ◽  
Author(s):  
K.-P. Heue ◽  
T. Wagner ◽  
S. P. Broccardo ◽  
D. Walter ◽  
S. J. Piketh ◽  
...  
Keyword(s):  
Power Plants ◽  
Trace Gases ◽  
Tropospheric Chemistry ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Small Scale ◽  
Two Dimensional ◽  
Gas Distribution ◽  
Dimensional Distribution ◽  
Airborne Imaging

Abstract. In many investigations of tropospheric chemistry information about the two dimensional distribution of trace gases on a small scale (e.g. tens to hundreds of meters) is highly desirable. An airborne instrument based on imaging Differential Optical Absorption Spectroscopy has been built to map the 2-D distribution of a series of relevant trace gases including NO2, HCHO, C2H2O2, H2O, O4, SO2, and BrO on a scale of 100 m. Here we report on the first tests of the novel aircraft instrument over the industrialised South African Highveld, where large variations in NO2 column densities in the immediate vicinity of several sources e.g. power plants or steel works, were measured. The observed patterns in the trace gas distribution are interpreted with respect to flux estimates, and it is seen that the fine resolution of the measurements allows separate sources in close proximity to one another to be distinguished.

Observations of the Martian atmosphere by NOMAD on ExoMars Trace Gas Orbiter

2020 ◽  
Author(s):  
Ann Carine Vandaele ◽  
Arianna Piccialli ◽  
Ian R. Thomas ◽  
Frank Daerden ◽  
Shohei Aoki ◽  
...  
Keyword(s):  
Spectral Range ◽  
Dust Storm ◽  
Trace Gases ◽  
Martian Atmosphere ◽  
Trace Gas ◽  
Ice Clouds ◽  
Mars Atmosphere ◽  
Solar Occultation ◽  
Composition And Structure

<p>The NOMAD (“Nadir and Occultation for MArs Discovery”) spectrometer suite on board the ExoMars Trace Gas Orbiter has been designed to investigate the composition of Mars' atmosphere, with a particular focus on trace gases, clouds and dust probing the ultraviolet and infrared regions covering large parts of the 0.2-4.3 µm spectral range [1,2].</p><p>Since its arrival at Mars in April 2018, NOMAD performed solar occultation, nadir and limb observations dedicated to the determination of the composition and structure of the atmosphere. Here we report on the different discoveries highlighted by the instrument: investigation of the 2018 Global dust storm and its impact on the water uplifting and escape, its impact on temperature increases within the atmosphere as inferred by GCM modeling and observations, the dust and ice clouds distribution during the event, ozone measurements, dayglow observations and in general advances in the analysis of the spectra recorded by the three channels of NOMAD.</p><p>References</p><p>[1] Vandaele, A.C., et al., 2015. Planet. Space Sci. 119, 233-249.</p><p>[2] Vandaele et al., 2018. Space Sci. Rev., 214:80, doi.org/10.1007/s11214-11018-10517-11212.</p>

scholarly journals Tropospheric nitrogen dioxide column retrieval from ground-based zenith-sky DOAS observations

2015 ◽  
Vol 8 (1) ◽  
pp. 935-985
Author(s):  
F. Tack ◽  
F. Hendrick ◽  
F. Goutail ◽  
C. Fayt ◽  
A. Merlaud ◽  
...  
Keyword(s):  
Nitrogen Dioxide ◽  
Correlation Coefficients ◽  
Atmospheric Composition ◽  
Optical Absorption Spectroscopy ◽  
Retrieval Algorithm ◽  
Measuring Instruments ◽  
Reference Spectrum ◽  
Vertical Column ◽  
Residual Amount

Abstract. We present an algorithm for retrieving tropospheric nitrogen dioxide (NO2) vertical column densities (VCDs) from ground-based zenith-sky (ZS) measurements of scattered sunlight. The method is based on a four-step approach consisting of (1) the Differential Optical Absorption Spectroscopy (DOAS) analysis of ZS radiance spectra using a fixed reference spectrum corresponding to low NO2 absorption, (2) the determination of the residual amount in the reference spectrum using a Langley-plot-type method, (3) the removal of the stratospheric content from the daytime total measured slant column based on stratospheric VCDs measured at sunrise and sunset, and simulation of the rapid NO2 diurnal variation, (4) the retrieval of tropospheric VCDs by dividing the resulting tropospheric slant columns by appropriate air mass factors (AMFs). These steps are fully characterized and recommendations are given for each of them. The retrieval algorithm is applied on a ZS dataset acquired with a Multi-AXis (MAX-) DOAS instrument during the Cabauw (51.97° N, 4.93° E, sea level) Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI) held from the 10 June to the 21 July 2009 in the Netherlands. A median value of 7.9 × 1015 molec cm−2 is found for the retrieved tropospheric NO2 VCDs, with maxima up to 6.0 × 1016 molec cm−2. The error budget assessment indicates that the overall error σTVCD on the column values is less than 28%. In case of low tropospheric contribution, σTVCD is estimated to be around 39% and is dominated by uncertainties in the determination of the residual amount in the reference spectrum. For strong tropospheric pollution events, σTVCD drops to approximately 22% with the largest uncertainties on the determination of the stratospheric NO2 abundance and tropospheric AMFs. The tropospheric VCD amounts derived from ZS observations are compared to VCDs retrieved from off-axis and direct-sun measurements of the same MAX-DOAS instrument as well as to data from a co-located Système d'Analyse par Observations Zénithales (SAOZ) spectrometer. The retrieved tropospheric VCDs are in good agreement with the different datasets with correlation coefficients and slopes close to or larger than 0.9. The potential of the presented ZS retrieval algorithm is further demonstrated by its successful application on a 2 year dataset, acquired at the NDACC (Network for the Detection of Atmospheric Composition Change) station Observatoire de Haute Provence (OHP; Southern France).

scholarly journals Detection of O<sub>4</sub> absorption around 328 nm and 419 nm in measured atmospheric absorption spectra

2017 ◽  
Author(s):  
Johannes Lampel ◽  
Johannes Zielcke ◽  
Stefan Schmitt ◽  
Denis Pöhler ◽  
Udo Frieß ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Spectral Data ◽  
Cross Section ◽  
Cross Sections ◽  
Trace Gases ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Absorption Cross ◽  
Peak Absorption ◽  
Spectrally Resolved

Abstract. Retrieving the column of an absorbing trace gas from spectral data requires that all absorbers in the corresponding wavelength range are sufficiently well known. This is especially important for the retrieval of weak absorbers, whose absorptions are often in the 10-4 range. Previous publications on the absorptions of the oxygen dimer O2-O2 (or short: O4) list absorption peaks at 328 nm and 419 nm, for which no spectrally resolved literature cross-sections are available. As these absorptions potentially influence the spectral retrieval of various trace gases, such as HCHO, BrO, OClO and IO, their shape and magnitude needs to be quantified. We assume that the shape of the absorption peaks at 328 nm and 419 nm can be approximated by their respective neighboring absorption peaks. Using this approach we obtain estimates for the wavelength of the absorption and its magnitude. Using Longpath Differential Optical Absorption Spectroscopy (LP-DOAS) observations and Multi-Axis (MAX)-DOAS observations, we estimate the peak absorption cross-sections of O4 to be (1.7 ± 0.2) x 10-47 cm5 molec-2 and determine the wavelength of its maximum at 328.51 ± 0.15 nm. For the absorption at 419.0 ± 0.4 nm a peak O4 cross-section value is determined as (3.7 ± 2.7) x 10-48 cm5 molec-2.

scholarly journals Investigation of the mixing layer height derived from ceilometer measurements in the Kathmandu Valley and implications for local air quality

2017 ◽  
Author(s):  
Andrea Mues ◽  
Maheswar Rupakheti ◽  
Christoph Münkel ◽  
Axel Lauer ◽  
Heiko Bozem ◽  
...  
Keyword(s):  
Black Carbon ◽  
Diurnal Cycle ◽  
Monsoon Season ◽  
Mixing Layer ◽  
Kathmandu Valley ◽  
Mixing Height ◽  
Layer Height ◽  
Emission Fluxes ◽  
Mixing Layer Height ◽  
Carbon Concentrations

Abstract. In this study one year of ceilometer measurements taken in the Kathmandu Valley, Nepal, in the framework of the SusKat project (A Sustainable Atmosphere for the Kathmandu Valley) were analyzed to investigate the diurnal variation of the mixing layer height and its dependency on the meteorological conditions. In addition, the impact of the mixing layer height on the temporal variation and the magnitude of the measured black carbon concentrations are analysed for each season. Based on the assumption that black carbon aerosols are vertically well mixed within the mixing layer and the finding that the mixing layer varies only little during night time and morning hours, black carbon emission fluxes are estimated for these hours and per month. Even though this method is relatively simple, it can give an observationally based first estimate of the black carbon emissions in this region, especially illuminating the seasonal cycle of the emission fluxes. In all seasons the diurnal cycle of the mixing layer height is typically characterized by low heights during the night and maximum values during in the afternoon. Seasonal differences are found in the absolute mixing layer height values and the duration of the typical daytime maximum. During the monsoon season a diurnal cycle has been observed with the smallest amplitude, with the lowest daytime mixing height of all seasons, and also the highest nighttime and early morning mixing height of all seasons. These characteristics can mainly be explained with the frequently present clouds and the associated reduction in incoming solar radiation and outgoing longwave radiation. In general, the black carbon concentrations show a clear anticorrelation with mixing layer height measurements, although this relation is less pronounced in the monsoon season. The daily evolution of the black carbon diurnal cycle differs between the seasons, partly due to the different meteorological conditions including the mixing layer height. Other important reasons are the different main emission sources and their diurnal variations in the individual seasons. The estimation of the black carbon emission flux for the morning hours show a clear seasonal cycle with maximum values in December to April. Compared to the emission flux values provided by different emission databases for this region, the here estimated values are considerably higher. Several possible sources of uncertainty are considered, and even the absolute lower bound of the emissions based on our methodology is higher than in most emissions datasets, providing strong evidence that the black carbon emissions for this region have likely been underestimated in modelling studies thus far.

scholarly journals Characterisation of the mixing height temporal evolution by means of a laser dial system in an urban area – intercomparison results with a model application

2007 ◽  
Vol 25 (10) ◽  
pp. 2119-2124 ◽  
Author(s):  
M. A. García ◽  
M. L. Sánchez ◽  
B. de Torre ◽  
I. A. Pérez
Keyword(s):  
Urban Area ◽  
Lower Layer ◽  
Layer Structure ◽  
Correlation Coefficients ◽  
Temporal Variations ◽  
Mixing Height ◽  
Hysplit Model ◽  
Sensing System ◽  
Early Afternoon

Abstract. Measurements of vertical and temporal variations in ozone and aerosol as extinction over an urban area in Segovia, central Spain, were performed during two summer months in 2004 by means of a commercial Nd:YAG laser DIAL remote sensing system. The Differential Absorption Lidar (DIAL) technique was applied and its description is given. From the profile data, a practical determination of mixing height may be derived. A diurnal evolution for the whole dataset is observed, the highest mean mixing height being reached at 16:00 GMT, 2150 m. The presence of a double-layer structure at night was observed and the layers can be considered residual. On average, the lower layer is formed at 670 m and the upper layer yielded mean heights ranging between 1270 and 1390 m. The estimated mixing heights during the day are also compared with those obtained from the Lagrangian HYSPLIT model. The results show good statistical agreement between both approaches, mainly in the early afternoon, with correlation coefficients around 0.7.

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