scholarly journals Tropospheric NO<sub>2</sub> columns: a comparison between model and retrieved data from GOME measurements

2001 ◽  
Vol 1 (2) ◽  
pp. 411-438
Author(s):  
A. Lauer ◽  
M. Dameris ◽  
A. Richter ◽  
J. P. Burrows
Keyword(s):  
Atmospheric Chemistry ◽  
Regional Differences ◽  
Climate Model ◽  
Source Distribution ◽  
Satellite Measurements ◽  
New Approach ◽  
Tropospheric No2 ◽  
Global Coverage ◽  
First Time ◽  
Fully Coupled

Abstract. Tropospheric NO2 plays a variety of significant roles in atmospheric chemistry. In the troposphere it is one of the most significant precursors of photochemical ozone (O3) production and nitric acid (HNO3). In this study tropospheric NO2 columns were calculated by the fully coupled chemistry-climate model ECHAM4.L39(DLR)/CHEM. These have been compared with tropospheric NO2 columns, retrieved using the tropospheric excess method from measurements by the Global Ozone Monitoring Experiment (GOME) of up-welling earthshine irradiance and the extraterrestrial radiance. GOME is part of the core payload of the second European Research Satellite (ERS-2). For this study the first five years of GOME measurements have been used. The period of five years of observational data is sufficient to enable a comparison based on climatological averages and with global coverage, focussing on the geographical distribution of the tropospheric NO2, for the first time. A new approach of analysing regional differences (i.e. on continental scales) by calculating individual averages for different environments provides more detailed information about specific NOx sources and of their seasonal variations. The results obtained enable the validity of the model NO2 source distribution and the assumptions used to separate tropospheric and stratospheric parts of the NO2 column amount from the satellite measurements to be investigated.

scholarly journals Tropospheric NO<sub>2</sub> columns: a comparison between model and retrieved data from GOME measurements

2002 ◽  
Vol 2 (1) ◽  
pp. 67-78 ◽  
Author(s):  
A. Lauer ◽  
M. Dameris ◽  
A. Richter ◽  
J. P. Burrows
Keyword(s):  
Atmospheric Chemistry ◽  
Regional Differences ◽  
Climate Model ◽  
Source Distribution ◽  
Satellite Measurements ◽  
New Approach ◽  
Tropospheric No2 ◽  
Global Coverage ◽  
First Time ◽  
Fully Coupled

Abstract. Tropospheric NO2 plays a variety of significant roles in atmospheric chemistry. In the troposphere it is one of the most significant precursors of photochemical ozone (O3) production and nitric acid (HNO3). In this study tropospheric NO2 columns were calculated by the fully coupled chemistry-climate model ECHAM4.L39(DLR)/CHEM. These have been compared with tropospheric NO2 columns, retrieved using the tropospheric excess method from measurements by the Global Ozone Monitoring Experiment (GOME) of up-welling earthshine radiance and the extraterrestrial irradiance. GOME is part of the core payload of the second European Research Satellite (ERS-2). For this study the first five years of GOME measurements have been used. The period of five years of observational data is sufficiently long to facilitate for the first time a comparison based on climatological averages with global coverage, focussing on the geographical distribution of the tropospheric NO2. A new approach of analysing regional differences (i.e. on continental scales) by calculating individual averages for different environments provides more detailed information about specific NOx sources and of their seasonal variations. The results obtained enable the validity of the model NO2 source distribution and the assumptions used to separate tropospheric and stratospheric parts of the NO2 column amount from the satellite measurements to be investigated.

scholarly journals Impact of high solar zenith angles on dynamical and chemical processes in a coupled chemistry-climate model

2003 ◽  
Vol 3 (4) ◽  
pp. 3681-3711
Author(s):  
D. Lamago ◽  
M. Dameris ◽  
C. Schnadt ◽  
V. Eyring ◽  
C. Brühl
Keyword(s):  
Atmospheric Chemistry ◽  
Lower Stratosphere ◽  
Climate Model ◽  
Chemical Processes ◽  
Sensitivity Experiment ◽  
Mean Values ◽  
Ozone Destruction ◽  
The Impact ◽  
Fully Coupled ◽  
Ozone Column

Abstract. Actinic fluxes at high solar zenith angles (SZAs) are important for atmospheric chemistry, especially under twilight conditions in polar winter and spring. The results of a sensitivity experiment employing the fully coupled 3D chemistry-climate model ECHAM4.L39(DLR)/CHEM have been analysed to quantify the impact of SZAs greater than 87.5° on dynamical and chemical processes in the lower stratosphere, in particular their influence on the ozone layer. Although the actinic fluxes at SZAs larger than 87.5° are small, ozone concentrations are significantly affected because daytime photolytic ozone destruction is switched on earlier, especially the conversion of Cl2 and Cl2O2 into ClO at the end of polar night in the lower stratosphere. Comparing climatological mean ozone column values of a simulation considering SZAs up to 93° with those of the sensitivity run with SZAs confined to 87.5° total ozone is reduced by about 20% in the polar Southern Hemisphere, i.e., the ozone hole is "deeper'' if twilight conditions are considered in the model because there is 2–3 weeks more time for ozone destruction. This causes an additional cooling of the polar lower stratosphere (50 hPa) up to −4 K with obvious consequences for chemical processes. In the Northern Hemisphere the impact of high SZAs cannot be determined on the basis of climatological mean values due to the pronounced dynamic variability of the stratosphere in winter and spring.

Weekly cycle of NOx emissions as laboratory of atmospheric chemistry

2021 ◽  
Author(s):  
Steffen Beirle ◽  
Steffen Dörner ◽  
Vinod Kumar ◽  
Thomas Wagner
Keyword(s):  
Atmospheric Chemistry ◽  
Emission Reduction ◽  
Power Plants ◽  
Nox Emissions ◽  
Satellite Measurements ◽  
Weekly Cycle ◽  
Christian Culture ◽  
Tropospheric No2 ◽  
Reduction Of Nox ◽  
The Mean

&lt;p&gt;Satellite observations provide unique information on the amount and spatial distribution of tropospheric NO2. Several studies use such datasets for deriving NOx emissions. However, due to nonlinearities in the NOx chemistry (i.e., the dependency of the OH concentration and thus the NO2 lifetime on the NO2 concentration), the observed column densities of NO2 are not directly proportional to the underlying NOx emissions. Consequently, a certain reduction in NOx emissions could result in disproportionate reduction of the corresponding NO2 columns, which could be stronger or weaker depending on the chemical state (O3, NOx and VOC levels) and conditions like temperature, humidity and acitinic flux. This effect complicates the quantification of NOx emissions from satellite measurements of NO2, and e.g. biases the emission reduction as derived from the reduction of NO2 column densities observed during recent lockdowns. &amp;#160;&lt;/p&gt;&lt;p&gt;Here we quantify the nonlinearity of the NOx system for different cities as well as power plants by investigating the effect of reduced NOx emissions on days of rest, i.e. Fridays/Sundays in Muslim/Christian culture, respectively. The reduction of NOx emissions is thereby quantified based on the continuity equation by calculating the divergence of the mean NO2 flux. This method has been proven to be sensitive for localized sources, where the uncertainties due to NO2 lifetime are small (Beirle et al., Sci. Adv., 2019). This reduction in emissions is then set in relation to the corresponding reduction of NO2 columns integrated around the source, which strongly depend on the NO2 lifetime.&lt;/p&gt;

scholarly journals Retrieval of tropospheric NO<sub>2</sub> columns from SCIAMACHY combining measurements from limb and nadir geometries

2012 ◽  
Vol 5 (4) ◽  
pp. 5043-5105 ◽  
Author(s):  
A. Hilboll ◽  
A. Richter ◽  
A. Rozanov ◽  
Ø. Hodnebrog ◽  
A. Heckel ◽  
...  
Keyword(s):  
Systematic Bias ◽  
Satellite Measurements ◽  
Matching Algorithm ◽  
The Earth ◽  
Novel Approach ◽  
Tropospheric No2 ◽  
Invaluable Tool ◽  
Global Coverage ◽  
Sector Method

Abstract. Satellite measurements of atmospheric trace gases have proved to be an invaluable tool for monitoring the Earth system. When these measurements are to be used for assessing tropospheric emissions and pollution, as for example in the case of nadir measurements of nitrogen dioxide (NO2), it is necessary to separate the stratospheric from the tropospheric signal. The SCIAMACHY instrument offers the unique opportunity to combine its measurements in limb and nadir viewing geometries into a tropospheric data product, using the limb measurements of the stratospheric NO2 abundances to correct the nadir measurements' total columns. In this manuscript, we present a novel approach to limb/nadir matching, calculating one stratospheric NO2 value from limb measurements for every single nadir measurement, abandoning global coverage for the sake of spatial accuracy. As a comparison, modelled stratospheric NO2 columns from the Oslo CTM2 are evaluated as stratospheric correction, and both datasets are confronted with the originally used reference sector method. Our study shows that stratospheric NO2 columns from SCIAMACHY limb measurements very well reflect stratospheric conditions. The zonal variability of stratospheric NO2 is captured by our matching algorithm, and the quality of the resulting tropospheric NO2 columns improves considerably. Modelled stratospheric NO2 columns from the Oslo CTM2 agree remarkably well with the measurements. Both datasets need to be matched to the level of the nadir measurements, however, because a time and latitude dependent bias between both stratospheric datasets and the measured nadir columns can be observed over clean regions. After accounting for this systematic bias between SCIAMACHY nadir observations and the stratospheric columns, both new stratospheric correction methods provide a significant improvement to the retrieval of tropospheric NO2 columns from the SCIAMACHY instrument.

scholarly journals Analysis of tropospheric NO2 over Iraq using OMI satellite measurements

2020 ◽  
Vol 29 (1) ◽  
pp. 3-16
Author(s):  
Jasim Rajab ◽  
Ali Al-Salihi ◽  
Ahmed Hassan ◽  
Jasim Kadhum ◽  
Hwee San Lim
Keyword(s):  
Atmospheric Chemistry ◽  
Weather Conditions ◽  
Trace Gas ◽  
Linear Growth Rate ◽  
Anthropogenic Emissions ◽  
Ozone Monitoring Instrument ◽  
Satellite Measurements ◽  
Monsoon Period ◽  
Tropospheric No2 ◽  
Hot Weather

Tropospheric nitrogen dioxide (NO2) is a trace gas with important impact on atmospheric chemistry, human health and a key pollutant in particular cities, measured from space since the mid-1990s by the GOME, SCIAMACHY, OMI, and GOME-2 instruments. This study present ten years (monthly and yearly averaged) dataset from Ozone Monitoring Instrument (OMI) used to investigate tropospheric NO2 characteristics and variations over Iraq during 2005–2014. Annual NO2 shows an elevation from the northern to the southern and highest values was at central parts of Iraq. Monthly distributions revels higher values NO2 in winter and summer than spring and autumn seasons, and rising NO2 throughout study period over industrial and crowded urban zones. The trend analysis over Baghdad shows a linear growth rate 9.8% per year with an annual average (5.6·1015 molecules per 1 cm2). The air mass trajectory analysis as hotspot regions shows seasonal fluctuations between winter and summer seasons depend on weather conditions and topography. The increased NO2 values in winter are due to anthropogenic emissions and subsequent plumes from Europe. In addition, in summer because of hot weather and large paddy fields emissions. The lowest NO2 value was at monsoon period mostly linked to the rains. The OMI data and satellite information are able to observe the troposphere NO2 elevation at different regions.

scholarly journals Improvements to the retrieval of tropospheric NO<sub>2</sub> from satellite – stratospheric correction using SCIAMACHY limb/nadir matching and comparison to Oslo CTM2 simulations

2013 ◽  
Vol 6 (3) ◽  
pp. 565-584 ◽  
Author(s):  
A. Hilboll ◽  
A. Richter ◽  
A. Rozanov ◽  
Ø. Hodnebrog ◽  
A. Heckel ◽  
...  
Keyword(s):  
Earth System ◽  
Spatial Accuracy ◽  
Satellite Measurements ◽  
Matching Algorithm ◽  
The Earth ◽  
Novel Approach ◽  
Tropospheric No2 ◽  
Invaluable Tool ◽  
Global Coverage

Abstract. Satellite measurements of atmospheric trace gases have proved to be an invaluable tool for monitoring the Earth system. When these measurements are to be used for assessing tropospheric emissions and pollution, as for example in the case of nadir measurements of nitrogen dioxide (NO2), it is necessary to separate the stratospheric from the tropospheric signal. The SCIAMACHY instrument offers the unique opportunity to combine its measurements in limb- and nadir-viewing geometries into a tropospheric data product, using the limb measurements of the stratospheric NO2 abundances to correct the nadir measurements' total columns. In this manuscript, we present a novel approach to limb/nadir matching, calculating one stratospheric NO2 value from limb measurements for every single nadir measurement, abandoning global coverage for the sake of spatial accuracy. For comparison, modelled stratospheric NO2 columns from the Oslo CTM2 are also evaluated for stratospheric correction. Our study shows that stratospheric NO2 columns from SCIAMACHY limb measurements very well reflect stratospheric conditions. The zonal variability of the stratospheric NO2 field is captured by our matching algorithm, and the quality of the resulting tropospheric NO2 columns improves considerably. Both stratospheric datasets need to be adjusted to the level of the nadir measurements, because a time- and latitude-dependent bias to the measured nadir columns can be observed over clean regions. After this offset is removed, the two datasets agree remarkably well, and both stratospheric correction methods provide a significant improvement to the retrieval of tropospheric NO2 columns from the SCIAMACHY instrument.

scholarly journals Nitrogen compounds and ozone in the stratosphere: comparison of MIPAS satellite data with the Chemistry Climate Model ECHAM5/MESSy1

2007 ◽  
Vol 7 (4) ◽  
pp. 9899-9924
Author(s):  
C. Brühl ◽  
B. Steil ◽  
G. Stiller ◽  
B. Funke ◽  
P. Jöckel
Keyword(s):  
Satellite Data ◽  
Climate Model ◽  
Chemical Species ◽  
Simulated Data ◽  
Experimental Uncertainty ◽  
Diurnal Cycles ◽  
Global Coverage ◽  
The Antarctic ◽  
First Time ◽  
Middle Stratosphere

Abstract. The chemistry climate model ECHAM5/MESSy1 (E5/M1) in a setup extending from the surface to 80 km with a vertical resolution of about 600 m near the tropopause with nudged tropospheric meteorology allows a direct comparison with satellite data of chemical species at the same time and location. Here we present results out of a transient 10 years simulation for the period of the Antarctic vortex split in September 2002, where data of MIPAS on the ENVISAT-satellite are available. For the first time this satellite instrument opens the opportunity, to evaluate all stratospheric nitrogen containing species simultaneously with a good global coverage, including the source gas N2O which allows an estimate for NOx-production in the stratosphere. We show correlations between simulated and observed species in the altitude region between 10 and 50 hpa for different latitude belts, together with the Probability Density Functions (PDFs) of model results and observations. This is supplemented by global charts on pressure levels showing the satellite data and the simulated data sampled at the same time and location. We demonstrate that the model in most cases captures the partitioning in the nitrogen family, the diurnal cycles and the spatial distribution within experimental uncertainty. There appears to be, however, a problem to reproduce the observed nighttime partitioning between N2O5 and NO2 in the middle stratosphere.

scholarly journals Nitrogen compounds and ozone in the stratosphere: comparison of MIPAS satellite data with the chemistry climate model ECHAM5/MESSy1

2007 ◽  
Vol 7 (21) ◽  
pp. 5585-5598 ◽  
Author(s):  
C. Brühl ◽  
B. Steil ◽  
G. Stiller ◽  
B. Funke ◽  
P. Jöckel
Keyword(s):  
Satellite Data ◽  
Climate Model ◽  
Chemical Species ◽  
Simulated Data ◽  
Experimental Uncertainty ◽  
Diurnal Cycles ◽  
Global Coverage ◽  
The Antarctic ◽  
First Time ◽  
Middle Stratosphere

Abstract. The chemistry climate model ECHAM5/MESSy1 (E5/M1) in a setup extending from the surface to 80 km with a vertical resolution of about 600 m near the tropopause with nudged tropospheric meteorology allows a direct comparison with satellite data of chemical species at the same time and location. Here we present results out of a transient 10~years simulation for the period of the Antarctic vortex split in September 2002, where data of MIPAS on the ENVISAT-satellite are available. For the first time this satellite instrument opens the opportunity, to evaluate all stratospheric nitrogen containing species simultaneously with a good global coverage, including the source gas N2O and ozone which allows an estimate for NOx-production in the stratosphere. We show correlations between simulated and observed species in the altitude region between 10 and 50 hpa for different latitude belts, together with the Probability Density Functions (PDFs) of model results and observations. This is supplemented by global maps on pressure levels showing the comparison between the satellite and the simulated data sampled at the same time and location. We demonstrate that the model in most cases captures the partitioning in the nitrogen family, the diurnal cycles and the spatial distribution within experimental uncertainty. This includes even variations due to tropospheric clouds. There appears to be, however, a problem to reproduce the observed nighttime partitioning between N2O5 and NO2 in the middle stratosphere using the recommended set of reaction coefficients and photolysis data.

scholarly journals Cloud base height retrieval from multi-angle satellite data

2018 ◽  
Author(s):  
Christoph Böhm ◽  
Odran Sourdeval ◽  
Johannes Mülmenstädt ◽  
Johannes Quaas ◽  
Susanne Crewell
Keyword(s):  
Reanalysis Data ◽  
Horizontal Resolution ◽  
Cloud Base ◽  
Height Distribution ◽  
Satellite Measurements ◽  
New Approach ◽  
Global Coverage ◽  
One Year ◽  
Terra Satellite ◽  
Cloud Base Height

Abstract. Clouds are a key modulator of the Earth energy budget at the top of the atmosphere and at the surface. While the cloud top height is operationally retrieved with global coverage, only few methods have been proposed to determine cloud base heights (zbase) from satellite measurements. This study presents a new approach to retrieve cloud base heights using the Multi-angle Imaging SpectroRadiometer (MISR) on the Terra satellite. It can be applied if some cloud gaps occur within the chosen distance of typically 10 km. The MISR cloud base height (MIBase) algorithm then determines zbase from the ensemble of all MISR cloud top heights retrieved at a 1.1-km horizontal resolution in this area. MIBase is first calibrated using one year of ceilometer data from more than 1500 sites within the continental United States of America. The 15th percentile of the cloud top height distribution within a circular area of 10 km radius provides the best agreement with the ground-based data. The thorough evaluation of the MIBase product zbase with further ceilometer data yields a correlation coefficient of about 0.66. For a three year period, the median zbase is generated globally on a 0.25° × 0.25° grid. It shows plausible results in particular over sea as well as for seasonal differences. The potential of the full 16 years of MISR data is demonstrated for the southeast Pacific revealing inter-annual variability in zbase in accordance with reanalysis data.

scholarly journals Axial Compressor Mean-Line Analysis: Choking Modelling and Fully-Coupled Integration in Engine Performance Simulations

2021 ◽  
Vol 6 (1) ◽  
pp. 4
Author(s):  
Ioannis Kolias ◽  
Alexios Alexiou ◽  
Nikolaos Aretakis ◽  
Konstantinos Mathioudakis
Keyword(s):  
Axial Compressor ◽  
Engine Performance ◽  
Engine Model ◽  
Multi Stage ◽  
Transient Simulations ◽  
Full Knowledge ◽  
Compressor Performance ◽  
First Time ◽  
Performance Calculation ◽  
Fully Coupled

A mean-line compressor performance calculation method is presented that covers the entire operating range, including the choked region of the map. It can be directly integrated into overall engine performance models, as it is developed in the same simulation environment. The code materializing the model can inherit the same interfaces, fluid models, and solvers, as the engine cycle model, allowing consistent, transparent, and robust simulations. In order to deal with convergence problems when the compressor operates close to or within the choked operation region, an approach to model choking conditions at blade row and overall compressor level is proposed. The choked portion of the compressor characteristics map is thus numerically established, allowing full knowledge and handling of inter-stage flow conditions. Such choking modelling capabilities are illustrated, for the first time in the open literature, for the case of multi-stage compressors. Integration capabilities of the 1D code within an overall engine model are demonstrated through steady state and transient simulations of a contemporary turbofan layout. Advantages offered by this approach are discussed, while comparison of using alternative approaches for representing compressor performance in overall engine models is discussed.

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