scholarly journals An alternative way to evaluate chemistry-transport model variability

2017 ◽  
Vol 10 (3) ◽  
pp. 1199-1208 ◽  
Author(s):  
Laurent Menut ◽  
Sylvain Mailler ◽  
Bertrand Bessagnet ◽  
Guillaume Siour ◽  
Augustin Colette ◽  
...  
Keyword(s):  
Transport Model ◽  
Model Performance ◽  
Error Statistics ◽  
Chemistry Transport Model ◽  
Temporal Correlations ◽  
Time Period ◽  
The Difference ◽  
Model Variability ◽  
Spatial Locations ◽  
Statistical Indicators

Abstract. A simple and complementary model evaluation technique for regional chemistry transport is discussed. The methodology is based on the concept that we can learn about model performance by comparing the simulation results with observational data available for time periods other than the period originally targeted. First, the statistical indicators selected in this study (spatial and temporal correlations) are computed for a given time period, using colocated observation and simulation data in time and space. Second, the same indicators are used to calculate scores for several other years while conserving the spatial locations and Julian days of the year. The difference between the results provides useful insights on the model capability to reproduce the observed day-to-day and spatial variability. In order to synthesize the large amount of results, a new indicator is proposed, designed to compare several error statistics between all the years of validation and to quantify whether the period and area being studied were well captured by the model for the correct reasons.

scholarly journals Variability of springtime transpacific pollution transport during 2000–2006: the INTEX-B mission in the context of previous years

2010 ◽  
Vol 10 (3) ◽  
pp. 1345-1359 ◽  
Author(s):  
G. G. Pfister ◽  
L. K. Emmons ◽  
D. P. Edwards ◽  
A. Arellano ◽  
T. Campos ◽  
...  
Keyword(s):  
Transport Model ◽  
Pollution Transport ◽  
Chemistry Transport Model ◽  
Pollution Levels ◽  
Annual Variability ◽  
Source Regions ◽  
Time Period ◽  
The Pacific ◽  
The Us ◽  
Transport Experiment

Abstract. We analyze the transport of pollution across the Pacific during the NASA INTEX-B (Intercontinental Chemical Transport Experiment Part B) campaign in spring 2006 and examine how this year compares to the time period for 2000 through 2006. In addition to aircraft measurements of carbon monoxide (CO) collected during INTEX-B, we include in this study multi-year satellite retrievals of CO from the Measurements of Pollution in the Troposphere (MOPITT) instrument and simulations from the chemistry transport model MOZART-4. Model tracers are used to examine the contributions of different source regions and source types to pollution levels over the Pacific. Additional modeling studies are performed to separate the impacts of inter-annual variability in meteorology and dynamics from changes in source strength. Interannual variability in the tropospheric CO burden over the Pacific and the US as estimated from the MOPITT data range up to 7% and a somewhat smaller estimate (5%) is derived from the model. When keeping the emissions in the model constant between years, the year-to-year changes are reduced (2%), but show that in addition to changes in emissions, variable meteorological conditions also impact transpacific pollution transport. We estimate that about 1/3 of the variability in the tropospheric CO loading over the contiguous US is explained by changes in emissions and about 2/3 by changes in meteorology and transport. Biomass burning sources are found to be a larger driver for inter-annual variability in the CO loading compared to fossil and biofuel sources or photochemical CO production even though their absolute contributions are smaller. Source contribution analysis shows that the aircraft sampling during INTEX-B was fairly representative of the larger scale region, but with a slight bias towards higher influence from Asian contributions.

scholarly journals Representing the effects of stratosphere–troposphere exchange on 3-D O<sub>3</sub> distributions in chemistry transport models using a potential vorticity-based parameterization

2016 ◽  
Vol 16 (17) ◽  
pp. 10865-10877 ◽  
Author(s):  
Jia Xing ◽  
Rohit Mathur ◽  
Jonathan Pleim ◽  
Christian Hogrefe ◽  
Jiandong Wang ◽  
...  
Keyword(s):  
Potential Vorticity ◽  
Transport Model ◽  
Model Performance ◽  
Surface Concentration ◽  
Weather Research And Forecasting ◽  
Regional Models ◽  
Transport Models ◽  
Reference Case ◽  
Chemistry Transport Model ◽  
Spatially Varying

Abstract. Downward transport of ozone (O3) from the stratosphere can be a significant contributor to tropospheric O3 background levels. However, this process often is not well represented in current regional models. In this study, we develop a seasonally and spatially varying potential vorticity (PV)-based function to parameterize upper tropospheric and/or lower stratospheric (UTLS) O3 in a chemistry transport model. This dynamic O3–PV function is developed based on 21-year ozonesonde records from World Ozone and Ultraviolet Radiation Data Centre (WOUDC) with corresponding PV values from a 21-year Weather Research and Forecasting (WRF) simulation across the Northern Hemisphere from 1990 to 2010. The result suggests strong spatial and seasonal variations of O3 ∕ PV ratios which exhibits large values in the upper layers and in high-latitude regions, with highest values in spring and the lowest values in autumn over an annual cycle. The newly developed O3 ∕ PV function was then applied in the Community Multiscale Air Quality (CMAQ) model for an annual simulation of the year 2006. The simulated UTLS O3 agrees much better with observations in both magnitude and seasonality after the implementation of the new parameterization. Considerable impacts on surface O3 model performance were found in the comparison with observations from three observational networks, i.e., EMEP, CASTNET and WDCGG. With the new parameterization, the negative bias in spring is reduced from −20 to −15 % in the reference case to −9 to −1 %, while the positive bias in autumn is increased from 1 to 15 % in the reference case to 5 to 22 %. Therefore, the downward transport of O3 from upper layers has large impacts on surface concentration and needs to be properly represented in regional models.

scholarly journals Transpacific pollution transport during INTEX-B: spring 2006 in context to previous years

2009 ◽  
Vol 9 (4) ◽  
pp. 17817-17849 ◽  
Author(s):  
G. G. Pfister ◽  
L. K. Emmons ◽  
D. P. Edwards ◽  
A. Arellano ◽  
G. Sachse ◽  
...  
Keyword(s):  
Transport Model ◽  
Pollution Transport ◽  
Chemistry Transport Model ◽  
Pollution Levels ◽  
Annual Variability ◽  
Source Regions ◽  
Time Period ◽  
The Pacific ◽  
The Us ◽  
Transport Experiment

Abstract. We analyze the transport of pollution across the Pacific during the NASA INTEX-B (Intercontinental Chemical Transport Experiment Part B) campaign in spring 2006 and examine how this year compares to the time period for 2000 through 2006. In addition to aircraft measurements of carbon monoxide (CO) collected during INTEX-B, we include in this study multi-year satellite retrievals of CO from the Measurements of Pollution in the Troposphere (MOPITT) instrument and simulations from the chemistry transport model MOZART-4. Model tracers are used to examine the contributions of different source regions and source types to pollution levels over the Pacific. Additional modeling studies are performed to separate the impacts of inter-annual variability in meteorology and dynamics from changes in source strength. Interannual variability in the tropospheric CO burden over the Pacific and the US as estimated from the MOPITT data range up to 7% and a somewhat smaller estimate (5%) is derived from the model. When keeping the emissions in the model constant between years, the year-to-year changes are reduced to (2%), but show that in addition to changes in emissions, variable meteorological conditions also impact transpacific pollution transport. We estimate that about 1/3 of the variability in the tropospheric CO loading over the contiguous US is explained by changes in emissions and about 2/3 by changes in meteorology and transport. Biomass burning sources are found to be a larger driver for inter-annual variability in the CO loading compared to fossil and biofuel sources or photochemical CO production even though their absolute contributions are smaller. Source contribution analysis shows that the aircraft sampling during INTEX-B was fairly representative of the larger scale region, but with a slight bias towards higher influence from Asian contributions.

scholarly journals Dynamically controlled ozone decline in the tropical mid-stratosphere observed by SCIAMACHY

2019 ◽  
Vol 19 (2) ◽  
pp. 767-783 ◽  
Author(s):  
Evgenia Galytska ◽  
Alexey Rozanov ◽  
Martyn P. Chipperfield ◽  
Sandip. S. Dhomse ◽  
Mark Weber ◽  
...  
Keyword(s):  
Residence Time ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Satellite Measurements ◽  
Linear Change ◽  
Chemistry Transport Model ◽  
Negative Change ◽  
Time Period ◽  
Scanning Imaging ◽  
Odd Nitrogen

Abstract. Despite the recently reported beginning of a recovery in global stratospheric ozone (O3), an unexpected O3 decline in the tropical mid-stratosphere (around 30–35 km altitude) was observed in satellite measurements during the first decade of the 21st century. We use SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) measurements for the period 2004–2012 to confirm the significant O3 decline. The SCIAMACHY observations show that the decrease in O3 is accompanied by an increase in NO2. To reveal the causes of these observed O3 and NO2 changes, we performed simulations with the TOMCAT 3-D chemistry-transport model (CTM) using different chemical and dynamical forcings. For the 2004–2012 time period, the TOMCAT simulations reproduce the SCIAMACHY-observed O3 decrease and NO2 increase in the tropical mid-stratosphere. The simulations suggest that the positive changes in NO2 (around 7 % decade−1) are due to similar positive changes in reactive odd nitrogen (NOy), which are a result of a longer residence time of the source gas N2O and increased production via N2O + O(1D). The model simulations show a negative change of 10 % decade−1 in N2O that is most likely due to variations in the deep branch of the Brewer–Dobson Circulation (BDC). Interestingly, modelled annual mean “age of air” (AoA) does not show any significant changes in transport in the tropical mid-stratosphere during 2004–2012. However, further analysis of model results demonstrates significant seasonal variations. During the autumn months (September–October) there are positive AoA changes that imply transport slowdown and a longer residence time of N2O allowing for more conversion to NOy, which enhances O3 loss. During winter months (January–February) there are negative AoA changes, indicating faster N2O transport and less NOy production. Although the variations in AoA over a year result in a statistically insignificant linear change, non-linearities in the chemistry–transport interactions lead to a statistically significant negative N2O change.

scholarly journals The CHIMERE v2020r1 online chemistry-transport model

2021 ◽  
Author(s):  
Laurent Menut ◽  
Bertrand Bessagnet ◽  
Régis Briant ◽  
Arineh Cholakian ◽  
Florian Couvidat ◽  
...  
Keyword(s):  
Meteorological Parameters ◽  
Transport Model ◽  
Model Performance ◽  
Subgrid Scale ◽  
Chemistry Transport Model ◽  
Meteorological Model ◽  
Online Mode ◽  
Range Transport ◽  
Emission Activity ◽  
Operator Integration

Abstract. The CHIMERE v2020r1 model replaces the v2017r5 version and provides numerous novelties. The most important of which is the online coupling with the WRF meteorological model, via the OASIS3-MCT external coupler. The model can still be used in offline mode; the online mode enables taking into account the direct and indirect effects of aerosols on meteorology. This coupling also enables using the meteorological parameters with sub-hourly time-steps. Some new parameterizations are implemented to increase the model performance and the user's choices: DMS emissions, additional schemes for SOA formation with VBS and H2O, improved schemes for mineral dust, biomass burning and sea-salt emissions. The NOx emissions from lightning is added. The model also includes the possibility to use the splitting-operator integration technique. The subgrid scale variability calculation of concentrations due to emission activity sectors is now possible. Finally, a new vertical advection scheme has been implemented, able to simulate more correctly long-range transport of thin pollutants plumes.

scholarly journals A quasi chemistry-transport model mode for EMAC

2011 ◽  
Vol 4 (1) ◽  
pp. 195-206 ◽  
Author(s):  
R. Deckert ◽  
P. Jöckel ◽  
V. Grewe ◽  
K.-D. Gottschaldt ◽  
P. Hoor
Keyword(s):  
Water Vapor ◽  
Nitric Acid ◽  
Atmospheric Chemistry ◽  
Transport Model ◽  
Climate Simulation ◽  
Chemistry Transport Model ◽  
Mixing Ratios ◽  
Reference Simulation ◽  
The Difference ◽  
Chemical Water

Abstract. A quasi chemistry-transport model mode (QCTM) is presented for the numerical chemistry-climate simulation system ECHAM/MESSy Atmospheric Chemistry (EMAC). It allows for a quantification of chemical signals through suppression of any feedback between chemistry and dynamics. Noise would otherwise interfere too strongly. The signal is calculated from the difference of two QCTM simulations, a reference simulation and a sensitivity simulation. In order to avoid the feedbacks, the simulations adopt the following offline chemical fields: (a) offline mixing ratios of radiatively active substances enter the radiation scheme, (b) offline mixing ratios of nitric acid enter the scheme for re-partitioning and sedimentation from polar stratospheric clouds, (c) and offline methane oxidation is the exclusive source of chemical water-vapor tendencies. Any set of offline fields suffices to suppress the feedbacks, though may be inconsistent with the simulation setup. An adequate set of offline climatologies can be produced from a non-QCTM simulation using the setup of the reference simulation. Test simulations reveal the particular importance of adequate offline fields associated with (a). Inconsistencies from (b) are negligible when using adequate fields of nitric acid. Acceptably small inconsistencies come from (c), but should vanish for an adequate prescription of chemical water vapor tendencies. Toggling between QCTM and non-QCTM is done via namelist switches and does not require a source code re-compilation.

scholarly journals Simulating CH<sub>4</sub> and CO<sub>2</sub> over South and East Asia using the zoomed chemistry transport model LMDzINCA

2017 ◽  
Author(s):  
Xin Lin ◽  
Philippe Ciais ◽  
Philippe Bousquet ◽  
Michel Ramonet ◽  
Yi Yin ◽  
...  
Keyword(s):  
East Asia ◽  
Transport Model ◽  
Model Performance ◽  
Horizontal Resolution ◽  
Surface Fluxes ◽  
Vertical Resolution ◽  
Monitoring Networks ◽  
Atmospheric Measurements ◽  
Monsoon Period ◽  
Chemistry Transport Model

Abstract. The increasing availability of atmospheric measurements of greenhouse gases (GHGs) from surface stations can improve the retrieval of their fluxes at higher spatial and temporal resolutions by inversions, provided that chemistry transport models are able to properly represent the variability of concentrations observed at different stations. South and East Asia (SEA) is a region with large and very uncertain emissions of carbon dioxide (CO2) and methane (CH4), the most potent anthropogenic GHGs. Monitoring networks have expanded greatly during the past decade in this region, which should contribute to reducing uncertainties in estimates of regional GHG budgets. In this study, we simulate concentrations of CH4 and CO2 using a zoomed version of the global chemistry transport model LMDzINCA during the period 2006–2013. The zoomed version has a fine horizontal resolution of ~ 0.66° in longitude and ~0.51° in latitude over SEA and a coarser resolution elsewhere. The concentrations of CH4 and CO2 simulated from the zoomed model (abbreviated as ‘ZASIA’) are compared to those from the same model but with a uniform regular grid of 2.50° in longitude and 1.27° in latitude (abbreviated as ‘REG’), both having the same vertical 19 sigma pressure levels and prescribed with the same biogenic and anthropogenic fluxes. Model performance is evaluated for annual gradients between sites, seasonal, synoptic and diurnal variations, against a new dataset including 30 surface stations over SEA and adjacent regions. Our results show that, when prescribed with identical surface fluxes, compared to REG, the ZASIA version moderately improves the representation of CH4 mean annual gradients between stations as well as the seasonal and synoptic variations of this trace gas within the zoomed region. This moderate improvement probably results from reduction of representation errors and a better description of the CH4 concentration gradients related to the skewed spatial distribution of surface CH4 emissions, suggesting that the zoom transport model will be better suited for inversions of CH4 fluxes in SEA. With the relatively coarse vertical resolution and low-frequency (monthly) prescribed fluxes, the model generally does not capture the diurnal cycle of CH4 at most stations even with its zoomed configuration, emphasizing the need to increase the vertical resolution, and to improve parameterizations of turbulent diffusion in the planetary boundary layer and deep convection during the monsoon period. The model performance for CH4 is better than that for CO2 at any temporal scale, likely due to inaccuracies in the CO2 fluxes prescribed in this study.

scholarly journals Dynamically controlled ozone decline in the tropical mid-stratosphere observed by SCIAMACHY

2018 ◽  
Author(s):  
Evgenia Galytska ◽  
Alexey Rozanov ◽  
Martyn P. Chipperfield ◽  
Sandip S. Dhomse ◽  
Mark Weber ◽  
...  
Keyword(s):  
Residence Time ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Satellite Measurements ◽  
Chemistry Transport Model ◽  
Deep Branch ◽  
Negative Change ◽  
Time Period ◽  
Scanning Imaging ◽  
Odd Nitrogen

Abstract. Despite the recently reported beginning of a recovery in global stratospheric ozone (O3), an unexpected O3 decline in the tropical mid-stratosphere (around 30–35 km altitude) was observed in satellite measurements during the first decade of the 21st century. We use SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) measurements for the period 2004–2012 to confirm the significant O3 decline. The SCIAMACHY observations also show that the decrease in O3 is accompanied by an increase in NO2. To reveal the causes of these observed O3 and NO2 changes, we performed simulations with the TOMCAT 3D Chemistry-Transport Model (CTM) using different chemical and dynamical forcings. For the 2004–2012 time period, the TOMCAT simulations reproduce the SCIAMACHY-observed O3 decrease and NO2 increase in the tropical mid-stratosphere. The simulations suggest that the positive changes in NO2 (around 7 % per decade) are due to similar positive changes in reactive odd nitrogen (NOy), which are a result of a longer residence time of the source gas N2O and increased production via N2O + O(1D). The model simulations show a negative change of 10 % per decade in N2O that is most likely due to variations in the deep branch of the Brewer-Dobson Circulation (BDC). Interestingly, modelled annual mean age-of-air (AoA) does not show any significant changes in the transport in the tropical mid-stratosphere during 2004–2012. However, further analysis of model results demonstrate significant seasonal variations. During the autumn months (September–October) there are positive AoA changes, that imply transport slowdown and a longer residence time of N2O allowing larger conversion to NOy which enhances O3 loss. During winter months (January–February) there are negative AoA changes, indicating faster N2O transport and less NOy production. Although the changes in AoA cancel out when averaging over the year, non-linearities in the chemistry-transport interactions mean that the net negative N2O change remains.

scholarly journals Representing the effects of stratosphere-troposphere exchange on 3D O<sub>3</sub> distributions in chemistry transport models using a potential vorticity based parameterization

2016 ◽  
Author(s):  
Jia Xing ◽  
Rohit Mathur ◽  
Jonathan Pleim ◽  
Christian Hogrefe ◽  
Jiandong Wang ◽  
...  
Keyword(s):  
Potential Vorticity ◽  
Transport Model ◽  
Model Performance ◽  
Surface Concentration ◽  
Weather Research And Forecasting ◽  
Regional Models ◽  
Transport Models ◽  
Reference Case ◽  
Chemistry Transport Model ◽  
Spatially Varying

Abstract. Downward transport of ozone (O3) from the stratosphere can be a significant contributor to tropospheric O3 background levels. However, this process often is not well represented in current regional models. In this study, we develop a seasonally and spatially varying potential vorticity (PV)-based function to numerically assimilate upper tropospheric / lower stratospheric (UTLS) O3 in a chemistry transport model. This dynamic O3-PV function is parametrized based on 21-year ozonesonde records from World Ozone and Ultraviolet Radiation Data Centre (WOUDC) with corresponding PV values from a 21-year Weather Research and Forecasting (WRF) simulation across the northern hemisphere from 1990 to 2010. The result suggests strong spatial and seasonal variations of O3/PV ratios which exhibits large values in the upper layers and in high latitude regions, with highest values in spring and the lowest values in autumn over an annual cycle. The newly-developed O3/PV function was then applied in the Community Multiscale Air Quality (CMAQ) model for an annual simulation of the year 2006. The simulated UTLS O3 agrees much better with observations in both magnitude and seasonality after the implementation of the new function. Considerable impacts on surface O3 model performance were found in the comparison with observations from three observational networks, i.e., EMEP, CASTNET and WDCGG. With the new function, the negative bias in spring is reduced from −20 to −15 % in the reference case to −9 to −1 %, while the positive bias in autumn is increased from 1 to 15 % in the reference case to 5 to 22 %. Therefore, the downward transport of O3 from upper layers has large impacts on surface concentration and needs to be properly represented in regional models.

scholarly journals Stratospheric age of air computed with trajectories based on various 3D-Var and 4D-Var data sets

2005 ◽  
Vol 5 (1) ◽  
pp. 1-7 ◽  
Author(s):  
M. P. Scheele ◽  
P. C. Siegmund ◽  
P. F. J. Velthoven
Keyword(s):  
Time Series ◽  
Lower Stratosphere ◽  
Transport Model ◽  
Segment Length ◽  
Data Sets ◽  
Wind Fields ◽  
Chemistry Transport Model ◽  
Backward Trajectories ◽  
Forecast Data ◽  
The Difference

Abstract. The age of stratospheric air is computed with a trajectory model, using ECMWF ERA-40 3D-Var and operational 4D-Var winds. Analysis as well as forecast data are used. In the latter case successive forecast segments are put together to get a time series of the wind fields. This is done for different forecast segment lengths. The sensitivity of the computed age to the forecast segment length and assimilation method are studied, and the results are compared with observations and with results from a chemistry transport model that uses the same data sets. A large number of backward trajectories are started in the stratosphere, and from the fraction of these trajectories that has passed the tropopause the age of air is computed. First, for ten different data sets 50-day backward trajectories starting in the tropical lower stratosphere are computed. The results show that in this region the computed cross-tropopause transport decreases with increasing forecast segment length. Next, for three selected data sets (3D-Var 24-h and 4D-Var 72-h forecast segments, and 4D-Var analyses) 5-year backward trajectories are computed that start all over the globe at an altitude of 20km. For all data sets the computed ages of air in the extratropics are smaller than the observation-based age. For 4D-Var forecast series they are closest to the observation-based values, but still 0.5-1.5 year too small. Compared to the difference in age between the results for the different data sets, the difference in age between the trajectory and the chemistry transport model results is small.

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