scholarly journals The Mainz profile algorithm (MAPA)

2019 ◽  
Vol 12 (3) ◽  
pp. 1785-1806 ◽  
Author(s):  
Steffen Beirle ◽  
Steffen Dörner ◽  
Sebastian Donner ◽  
Julia Remmers ◽  
Yang Wang ◽  
...  
Keyword(s):  
A Priori ◽  
Scaling Factor ◽  
Least Square ◽  
Trace Gas ◽  
Vertical Profiles ◽  
Mixing Ratios ◽  
Surface Mixing ◽  
Sensitivity Studies ◽  
The Impact ◽  
Good Agreement

Abstract. The Mainz profile algorithm (MAPA) derives vertical profiles of aerosol extinction and trace gas concentrations from MAX-DOAS measurements of slant column densities under multiple elevation angles. This paper presents (a) a detailed description of the MAPA (v0.98), (b) results for the CINDI-2 campaign, and (c) sensitivity studies on the impact of a priori assumptions such as flag thresholds. Like previous profile retrieval schemes developed at MPIC, MAPA is based on a profile parameterization combining box profiles, which also might be lifted, and exponential profiles. But in contrast to previous inversion schemes based on least-square fits, MAPA follows a Monte Carlo approach for deriving those profile parameters yielding best match to the MAX-DOAS observations. This is much faster and directly provides physically meaningful distributions of profile parameters. In addition, MAPA includes an elaborated flagging scheme for the identification of questionable or dubious results. The AODs derived with MAPA for the CINDI-2 campaign show good agreement with AERONET if a scaling factor of 0.8 is applied for O4, and the respective NO2 and HCHO surface mixing ratios match those derived from coincident long-path DOAS measurements. MAPA results are robust with respect to modifications of the a priori MAPA settings within plausible limits.

scholarly journals The Mainz Profile Algorithm (MAPA)

2018 ◽  
Author(s):  
Steffen Beirle ◽  
Steffen Dörner ◽  
Sebastian Donner ◽  
Julia Remmers ◽  
Yang Wang ◽  
...  
Keyword(s):  
A Priori ◽  
Scaling Factor ◽  
Trace Gas ◽  
Aerosol Extinction ◽  
Vertical Profiles ◽  
Mixing Ratios ◽  
Surface Mixing ◽  
Sensitivity Studies ◽  
The Impact ◽  
Good Agreement

Abstract. The Mainz profile algorithm MAPA derives vertical profiles of aerosol extinction and trace gas concentrations from MAX-DOAS measurements of slant column densities under multiple elevation angles. This manuscript presents (a) a detailed description of the MAPA algorithm v0.98, including the flagging scheme for the identification of questionable or dubious results, (b) results for the CINDI-2 campaign, and (c) sensitivity studies on the impact of a-priori assumptions such as flag thresholds. MAPA is based on a profile parameterization combining box profiles, which also might be lifted, and exponential profiles. The profile parameters yielding best match to the MAX-DOAS observations are derived by a Monte Carlo approach, making MAPA much faster than previous parameter-based inversion schemes, and directly providing distributions of profile parameters. The AODs derived with MAPA for the CINDI-2 campaign show good agreement to AERONET if a scaling factor of 0.8 is applied for O4, and the respective NO2 and HCHO surface mixing ratios match those derived from coincident long-path DOAS measurements. MAPA results are robust to modifications of the a-priori MAPA settings within plausible limits.

scholarly journals Retrieval of tropospheric aerosol, NO<sub>2</sub> and HCHO vertical profiles from MAX-DOAS observations over Thessaloniki, Greece

2021 ◽  
Author(s):  
Dimitris Karagkiozidis ◽  
Martina Michaela Friedrich ◽  
Steffen Beirle ◽  
Alkiviadis Bais ◽  
François Hendrick ◽  
...  
Keyword(s):  
Estimation Method ◽  
Correlation Coefficients ◽  
Scaling Factor ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Systematic Bias ◽  
Vertical Profiles ◽  
Ancillary Data ◽  
Tropospheric Aerosol ◽  
Good Agreement

Abstract. In this study we focus on the retrieval of aerosol and trace gas vertical profiles from Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations for the first time over Thessaloniki, Greece. We use two independent inversion algorithms for the profile retrievals: The Mexican MAX-DOAS Fit (MMF) and the Mainz Profile Algorithm (MAPA). The former is based on the Optimal Estimation Method (OEM), while the latter follows a parameterization approach. We evaluate the performance of MMF and MAPA and we validate their retrieved products with ancillary data measured by other co-located reference instruments. We find an excellent agreement between the tropospheric column densities of NO2 retrieved by MMF and MAPA (Slope = 1.009, Pearson's correlation coefficient R = 0.982) and a good correlation for the case of HCHO (R = 0.927). For aerosols, we find better agreement for the aerosol optical depths (AODs) in the visible (i.e., at 477 nm), compared to the UV (360 nm) and we show that the agreement strongly depends on the O4 scaling factor that is used in the analysis. The trace gas differential slant column densities (dSCDs), simulated by the forward models, are also in good agreement, except for HCHO, where larger scatter is observed due to the increased spectral noise of the measurements in the UV. The agreement for NO2 and HCHO surface concentrations is similar to the comparison of the integrated columns with slightly decreased correlation coefficients. The AODs retrieved by the MAX-DOAS are validated by comparing them with AOD values measured by a CIMEL sun-photometer and a Brewer spectrophotometer. Four different flagging schemes were applied to the data in order to evaluate their performance. Qualitatively, a generally good agreement is observed for both wavelengths, but we find a systematic bias from the CIMEL and Brewer measurements, due to the limited sensitivity of the MAX-DOAS in retrieving information at higher altitudes, especially in the UV. An in-depth validation of the aerosol vertical profiles retrieved by the MAX-DOAS is not possible since only in very few cases the true aerosol profile is known during the period of study. However, we examine four cases, where the MAX-DOAS provided a generally good estimation of the shape of the profiles retrieved by a co-located multi-wavelength lidar system. The NO2 surface concentrations are validated against in situ observations and the comparison of both MMF and MAPA revealed good agreement with correlation coefficients of R = 0.78 and R = 0.73, respectively. Finally, the effect of the O4 scaling factor is investigated by intercomparing the integrated columns retrieved by the two algorithms and also by comparing the AODs derived by MAPA for different values of the scaling factor with AODs measured by the CIMEL and the Brewer.

The Impact of Competitive Quasi-Market on Service Delivery in Benue State University, Makurdi Nigeria

GIS Business ◽  
2019 ◽  
Vol 14 (4) ◽  
pp. 85-98
Author(s):  
Idoko Peter
Keyword(s):  
Service Delivery ◽  
A Priori ◽  
Least Square ◽  
Secondary Source ◽  
State University ◽  
Ordinary Least Square ◽  
Negative Effect ◽  
The Impact ◽  
The Relationship

This research the impact of competitive quasi market on service delivery in Benue State University, Makurdi Nigeria. Both primary and secondary source of data and information were used for the study and questionnaire was used to extract information from the purposively selected respondents. The population for this study is one hundred and seventy three (173) administrative staff of Benue State University selected at random. The statistical tools employed was the classical ordinary least square (OLS) and the probability value of the estimates was used to tests hypotheses of the study. The result of the study indicates that a positive relationship exist between Competitive quasi marketing in Benue State University, Makurdi Nigeria (CQM) and Transparency in the service delivery (TRSP) and the relationship is statistically significant (p<0.05). Competitive quasi marketing (CQM) has a negative effect on Observe Competence in Benue State University, Makurdi Nigeria (OBCP) and the relationship is not statistically significant (p>0.05). Competitive quasi marketing (CQM) has a positive effect on Innovation in Benue State University, Makurdi Nigeria (INVO) and the relationship is statistically significant (p<0.05) and in line with a priori expectation. This means that a unit increases in Competitive quasi marketing (CQM) will result to a corresponding increase in innovation in Benue State University, Makurdi Nigeria (INVO) by a margin of 22.5%. It was concluded that government monopoly in the provision of certain types of services has greatly affected the quality of service experience in the institution. It was recommended among others that the stakeholders in the market has to be transparent so that the system will be productive to serve the society effectively

scholarly journals The contribution of natural and anthropogenic very short-lived species to stratospheric bromine

2012 ◽  
Vol 12 (1) ◽  
pp. 371-380 ◽  
Author(s):  
R. Hossaini ◽  
M. P. Chipperfield ◽  
W. Feng ◽  
T. J. Breider ◽  
E. Atlas ◽  
...  
Keyword(s):  
Transport Model ◽  
Three Dimensional ◽  
Chemical Transport Model ◽  
Atmospheric Lifetime ◽  
Tropical Tropopause Layer ◽  
Mixing Ratios ◽  
Tropical Tropopause ◽  
Atmospheric Observations ◽  
Surface Mixing ◽  
The Impact

Abstract. We have used a global three-dimensional chemical transport model to quantify the impact of the very short-lived substances (VSLS) CHBr3, CH2Br2, CHBr2Cl, CHBrCl2, CH2BrCl and C2H5-Br on the bromine budget of the stratosphere. Atmospheric observations of these gases allow constraints on surface mixing ratios that, when incorporated into our model, contribute ~4.9–5.2 parts per trillion (ppt) of inorganic bromine (Bry) to the stratosphere. Of this total, ~76 % comes from naturally-emitted CHBr3 and CH2Br2. The remaining species individually contribute modest amounts. However, their accumulated total accounts for up to ~1.2 ppt of the supply and thus should not be ignored. We have compared modelled tropical profiles of a range of VSLS with observations from the recent 2009 NSF HIPPO-1 aircraft campaign. Modelled profiles agree reasonably well with observations from the surface to the lower tropical tropopause layer. We have also considered the poorly studied anthropogenic VSLS, C2H5Br, CH2BrCH2Br, n-C3H7Br and i-C3H7Br. We find the local atmospheric lifetime of these species in the tropical tropopause layer are ~183, 603, 39 and 49 days, respectively. These species, particularly C2H5Br and CH2BrCH2Br, would thus be important carriers of bromine to the stratosphere if emissions were to increase substantially. Our model shows ~70–73 % and ~80–85 % of bromine from these species in the tropical boundary layer can reach the lower stratosphere.

scholarly journals Impacts of updated spectroscopy on thermal infrared retrievals of methane evaluated with HIPPO data

2014 ◽  
Vol 7 (9) ◽  
pp. 10059-10107
Author(s):  
M. J. Alvarado ◽  
V. H. Payne ◽  
K. E. Cady-Pereira ◽  
J. D. Hegarty ◽  
S. S. Kulawik ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Trace Gases ◽  
Thermal Infrared ◽  
Trace Gas ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Spectroscopic Parameters ◽  
Mixing Ratios ◽  
Aircraft Observations ◽  
The Impact

Abstract. Errors in the spectroscopic parameters used in the forward radiative transfer model can introduce altitude-, spatially-, and temporally-dependent biases in trace gas retrievals. For well-mixed trace gases such as methane, where the variability of tropospheric mixing ratios is relatively small, reducing such biases is particularly important. We use aircraft observations from all five missions of the HIAPER Pole-to-Pole Observations (HIPPO) of the Carbon Cycle and Greenhouse Gases Study to evaluate the impact of updates to spectroscopic parameters for methane (CH4), water vapor (H2O), and nitrous oxide (N2O) on thermal infrared retrievals of methane from the NASA Aura Tropospheric Emission Spectrometer (TES). We find that updates to the spectroscopic parameters for CH4 result in a substantially smaller mean bias in the retrieved CH4 when compared with HIPPO observations. After an N2O-based correction, the bias in TES methane upper tropospheric representative values for measurements between 50° S and 50° N decreases from 56.9 to 25.7 ppbv, while the bias in the lower tropospheric representative value increases only slightly (from 27.3 to 28.4 ppbv). For retrievals with less than 1.6 DOFS, the bias is reduced from 26.8 to 4.8 ppbv. We also find that updates to the spectroscopic parameters for N2O reduce the errors in the retrieved N2O profile.

scholarly journals Aerosol retrieval experiments in the ESA Aerosol_cci project

2013 ◽  
Vol 6 (2) ◽  
pp. 2353-2411 ◽  
Author(s):  
T. Holzer-Popp ◽  
G. de Leeuw ◽  
D. Martynenko ◽  
L. Klüser ◽  
S. Bevan ◽  
...  
Keyword(s):  
A Priori ◽  
Round Robin ◽  
Mixing Ratios ◽  
Aerosol Retrieval ◽  
Standard Product ◽  
Sun Photometer ◽  
Priori Information ◽  
Cloud Mask ◽  
The Impact ◽  
Global Data

Abstract. Within the ESA Climate Change Initiative (CCI) project Aerosol_cci (2010–2013) algorithms for the production of long-term total column aerosol optical depth (AOD) datasets from European Earth Observation sensors are developed. Starting with eight existing pre-cursor algorithms three analysis steps are conducted to improve and qualify the algorithms: (1) a series of experiments applied to one month of global data to understand several major sensitivities to assumptions needed due to the ill-posed nature of the underlying inversion problem, (2) a round robin exercise of "best" versions of each of these algorithms (defined using the step 1 outcome) applied to four months of global data to identify mature algorithms, and (3) a comprehensive validation exercise applied to one complete year of global data produced by the algorithms selected as mature based on the round robin exercise. The algorithms tested included four using AATSR, three using MERIS and one using PARASOL. This paper summarizes the first step. Three experiments were conducted to assess the potential impact of major assumptions in the various aerosol retrieval algorithms. In the first experiment a common set of four aerosol components was used to provide all algorithms with the same assumptions. The second experiment introduced an aerosol property climatology, derived from a combination of model and sun photometer observations, as a priori information in the retrievals on the occurrence of the common aerosol components and their mixing ratios. The third experiment assessed the impact of using a common nadir cloud mask for AATSR and MERIS algorithms in order to characterize the sensitivity to remaining cloud contamination in the retrievals against the baseline dataset versions. The impact of the algorithm changes was assessed for one month (September 2008) of data qualitatively by visible analysis of monthly mean AOD maps and quantitatively by comparing global daily gridded satellite data against daily average AERONET sun photometer observations for the different versions of each algorithm. The analysis allowed an assessment of sensitivities of all algorithms which helped define the best algorithm version for the subsequent round robin exercise; all algorithms (except for MERIS) showed some, in parts significant, improvement. In particular, using common aerosol components and partly also a priori aerosol type climatology is beneficial. On the other hand the use of an AATSR-based common cloud mask meant a clear improvement (though with significant reduction of coverage) for the MERIS standard product, but not for the algorithms using AATSR.

Temporal instability modes of supersonic round jets

2010 ◽  
Vol 662 ◽  
pp. 173-196 ◽  
Author(s):  
LUIS PARRAS ◽  
STÉPHANE LE DIZÈS
Keyword(s):  
A Priori ◽  
Temporal Stability ◽  
Jet Noise ◽  
Base Flow ◽  
Round Jets ◽  
Instability Modes ◽  
Theoretical Predictions ◽  
Mode Characteristics ◽  
The Impact ◽  
Good Agreement

In this study, a comprehensive inviscid temporal stability analysis of a compressible round jet is performed for Mach numbers ranging from 1 to 10. We show that in addition to the Kelvin–Helmholtz instability modes, there exist for each azimuthal wavenumber three other types of modes (counterflow subsonic waves, subsonic waves and supersonic waves) whose characteristics are analysed in detail using a WKBJ theory in the limit of large axial wavenumber. The theory is constructed for any velocity and temperature profile. It provides the phase velocity and the spatial structure of the modes and describes qualitatively the effects of base-flow modifications on the mode characteristics. The theoretical predictions are compared with numerical results obtained for an hyperbolic tangent model and a good agreement is demonstrated. The results are also discussed in the context of jet noise. We show how the theory can be used to determine a priori the impact of jet modifications on the noise induced by instability.

scholarly journals Numerical Investigation of the Impact of H2 Enrichment on Lean Biogas/Air Flames: An Analytical Modelling Approach

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 369
Author(s):  
Filipe M. Quintino ◽  
Edgar C. Fernandes
Keyword(s):  
Laminar Flame ◽  
A Priori ◽  
Kinetic Mechanism ◽  
Laminar Flame Speed ◽  
Independent Variables ◽  
New Correlation ◽  
Dilution Effects ◽  
The Impact ◽  
Good Agreement ◽  
Modelling Approach

The transition from natural gas to renewable gases such as biogas and hydrogen creates an interchangeability challenge. The laminar flame speed SL is a critical parameter in appliance design as it is a unique characteristic of the flame mixture. It is thus essential to evaluate the impact of renewable gases on SL. In this work, 1D simulations were conducted in Cantera with the USC-Mech 2.0 kinetic mechanism. The SL of three base biogas blends (BG100, BG90 and BG80) was computed for H2 enrichment up to 50% in volume, equivalence ratio 0.8≤ϕ≤1.0, p=1 atm and Tu=298 K. It was found that the effect of H2 enrichment is higher for base blends with higher CO2 content as the thermal-diffusive and dilution effects of carbon dioxide are mitigated by hydrogen. The introduction of H2 also increases the H radical pool, which is linked with the increase in SL. A new correlation to model the impact of H2 enrichment, SL(xH2)=ζ(ϕ)/SL′(xCO2)xH2exH2+SL′(xCO2), is proposed, which exhibits good agreement with the literature data and simulations. This equation can be directly used to estimate SL without the need for a priori adaptations of fit parameters as the contributions of CO2 and H2 are isolated in independent variables.

Angular Distribution Studies for 65Zn Nuclei from 63Cu (α, pnγ) Reaction Using Constant Statistical Tensor, Least Square Fitting and σ/J Methods

2021 ◽  
Vol 19 (1) ◽  
pp. 30-37
Author(s):  
Taghreed A. Younis
Keyword(s):  
Least Square ◽  
Spin States ◽  
Least Square Fitting ◽  
Mixing Ratios ◽  
High Spin States ◽  
Multiple Mixing ◽  
Statistical Tensor ◽  
Distribution Studies ◽  
Experimental Values ◽  
Good Agreement

Multiple mixing ratios (δ-values) have been calculated for high-spin states excited in 29𝐶𝑢 63 (α,pnγ) 𝑍𝑛 30 65 in present work using constant statistical tensor (CST), least square fitting (LSF) and σ/J methods together with experimental values reported for such γ-transition the good agreement for (δ-values) calculated in these three methods confirms its validity to calculate the (δ-values) for γ-transition.

Representation of emissions from European major population centeres in MECO(n) - Lessons learned from EMeRGe-EU

2020 ◽  
Author(s):  
Mariano Mertens ◽  
Astrid Kerkweg ◽  
Patrick Jöckel ◽  
Markus Kilian ◽  
Lisa Eirenschmalz ◽  
...  
Keyword(s):  
Source Apportionment ◽  
Potential Model ◽  
Climate Model ◽  
Regional Scale ◽  
Good Representation ◽  
Data Set ◽  
Mixing Ratios ◽  
Extensive Evaluation ◽  
Sensitivity Studies ◽  
The Impact

&lt;p&gt;Comprehensive regional chemistry-climate or chemistry transport models are important tools to study the impact of emissions from major population centres (MPC) and/or investigate potential mitigation options for MPC emissions. Before such models can be employed it is important to investigate how well the models represent observed atmospheric conditions. This comparison helps not only in judging the performance of the models, but allows to test our understanding of chemical and physical processes in the atmosphere. A prerequisite for an extensive evaluation of models are the availability of temporally and spatially high resolved observational data. Such a data set was obtained during the EMeRGe-Europe campaign of the HALO research aircraft in July 2017, which targeted the outflow of different MPC in Europe.&lt;/p&gt;&lt;p&gt;We used the data of the EMeRGe-EU campaign together with ground based observations to evaluate the representation of European MPC emissions in the MECO(n) model system. MECO(n) is a global/regional chemistry-climate model which couples the regional chemistry-climate model COSMO-CLM/MESSy on-line (i.e., during runtime) with the global chemistry climate-model EMAC. The dynamics of EMAC is nudged against ERA-Interim reanalysis data. We performed three nesting steps from 300 km on the global scale to 50 km, 12 km and 7 km on the regional scale. In our evaluation we focus on tropospheric ozone (O&lt;sub&gt;3&lt;/sub&gt;) and related precursors, methane (CH&lt;sub&gt;4&lt;/sub&gt;) and sulphur dioxide (SO&lt;sub&gt;2&lt;/sub&gt;).&amp;#160;&lt;/p&gt;&lt;p&gt;Generally, the comparison between the measurements and the model results shows a good representation of European MPC emissions in MECO(n). In detail, however, the measured mixing ratios of carbon monoxide (CO) and reactive nitrogen (NO&lt;sub&gt;y&lt;/sub&gt;) &amp;#160;are underestimated, while O&lt;sub&gt;3&lt;/sub&gt; and SO&lt;sub&gt;2&lt;/sub&gt; are overestimated by the model. Potential reasons for these differences are too efficient vertical mixing, and underestimation of MPC emissions.&amp;#160;&lt;/p&gt;&lt;p&gt;To test hypotheses for potential model improvements we performed additional sensitivity studies with different nudging data for EMAC and an alternative anthropogenic emission inventory. The differences of the model results to the observations, however, are only slightly influenced by these changes. Accordingly, further hypotheses for potential model improvements needs to be investigated. &amp;#160;While the simulated mixing ratios differ only slightly between the sensitivity studies, the ozone source apportionment results (using a tagging approach) show much larger differences. This indicates the large uncertainty of &amp;#160;source apportionment analyses caused by uncertainties of emission inventories and model dynamics and requires further analysis in the future.&amp;#160;&lt;/p&gt;

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