A study of tropospheric ozone column enhancements over North America using satellite data and a global chemical transport model

Abstract. Accurate and temporally resolved fields of free-troposphere ozone are of major importance to quantify the intercontinental transport of pollution and the ozone radiative forcing. In this study we examine the impact of assimilating ozone observations from the Microwave Limb Sounder (MLS) and the Infrared Atmospheric Sounding Interferometer (IASI) in a global chemical transport model (MOdèle de Chimie Atmosphérique à Grande Échelle, MOCAGE). The assimilation of the two instruments is performed by means of a variational algorithm (4-D-VAR) and allows to constrain stratospheric and tropospheric ozone simultaneously. The analysis is first computed for the months of August and November 2008 and validated against ozone-sondes measurements to verify the presence of observations and model biases. It is found that the IASI Tropospheric Ozone Column (TOC, 1000–225 hPa) should be bias-corrected prior to assimilation and MLS lowermost level (215 hPa) excluded from the analysis. Furthermore, a longer analysis of 6 months (July–August 2008) showed that the combined assimilation of MLS and IASI is able to globally reduce the uncertainty (Root Mean Square Error, RMSE) of the modeled ozone columns from 30% to 15% in the Upper-Troposphere/Lower-Stratosphere (UTLS, 70–225 hPa) and from 25% to 20% in the free troposphere. The positive effect of assimilating IASI tropospheric observations is very significant at low latitudes (30° S–30° N), whereas it is not demonstrated at higher latitudes. Results are confirmed by a comparison with additional ozone datasets like the Measurements of OZone and wAter vapour by aIrbus in-service airCraft (MOZAIC) data, the Ozone Monitoring Instrument (OMI) total ozone columns and several high-altitude surface measurements. Finally, the analysis is found to be little sensitive to the assimilation parameters and the model chemical scheme, due to the high frequency of satellite observations compared to the average life-time of free-troposphere/low-stratosphere ozone.

Download Full-text

Characteristics of intercontinental transport of tropospheric ozone from Africa to Asia

10.5194/acp-2017-728 ◽

2017 ◽

Author(s):

Han Han ◽

Jane Liu ◽

Huiling Yuan ◽

Ye Zhu ◽

Yue Wu ◽

...

Keyword(s):

Tropospheric Ozone ◽

Transport Model ◽

Chemical Transport ◽

Early Spring ◽

Boreal Summer ◽

Boreal Winter ◽

Chemical Transport Model ◽

Upper Troposphere ◽

Intercontinental Transport ◽

Global Chemical Transport Model

Abstract. Based on 20-year simulations using a global chemical transport model, GEOS-Chem, and a trajectory model, HYSPLIT, the transport of ozone produced in the African troposphere to Asia is investigated. The study shows that the influence of African ozone on Asia varies largely in time and space. In the middle and upper troposphere, the inflow of African ozone to Asia peaks around 25° N, being the largest in boreal winter and early spring (> 10 ppbv) and the lowest in boreal summer (

Download Full-text

Combined assimilation of IASI and MLS observations to constrain tropospheric and stratospheric ozone in a global chemical transport model

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-177-2014 ◽

2014 ◽

Vol 14 (1) ◽

pp. 177-198 ◽

Cited By ~ 18

Author(s):

E. Emili ◽

B. Barret ◽

S. Massart ◽

E. Le Flochmoen ◽

A. Piacentini ◽

...

Keyword(s):

Tropospheric Ozone ◽

Radiative Forcing ◽

Transport Model ◽

Stratospheric Ozone ◽

Chemical Transport ◽

Chemical Transport Model ◽

Ozone Monitoring Instrument ◽

Intercontinental Transport ◽

Global Chemical Transport Model ◽

The Impact

Abstract. Accurate and temporally resolved fields of free-troposphere ozone are of major importance to quantify the intercontinental transport of pollution and the ozone radiative forcing. We consider a global chemical transport model (MOdèle de Chimie Atmosphérique à Grande Échelle, MOCAGE) in combination with a linear ozone chemistry scheme to examine the impact of assimilating observations from the Microwave Limb Sounder (MLS) and the Infrared Atmospheric Sounding Interferometer (IASI). The assimilation of the two instruments is performed by means of a variational algorithm (4D-VAR) and allows to constrain stratospheric and tropospheric ozone simultaneously. The analysis is first computed for the months of August and November 2008 and validated against ozonesonde measurements to verify the presence of observations and model biases. Furthermore, a longer analysis of 6 months (July–December 2008) showed that the combined assimilation of MLS and IASI is able to globally reduce the uncertainty (root mean square error, RMSE) of the modeled ozone columns from 30 to 15% in the upper troposphere/lower stratosphere (UTLS, 70–225 hPa). The assimilation of IASI tropospheric ozone observations (1000–225 hPa columns, TOC – tropospheric O3 column) decreases the RMSE of the model from 40 to 20% in the tropics (30° S–30° N), whereas it is not effective at higher latitudes. Results are confirmed by a comparison with additional ozone data sets like the Measurements of OZone and wAter vapour by aIrbus in-service airCraft (MOZAIC) data, the Ozone Monitoring Instrument (OMI) total ozone columns and several high-altitude surface measurements. Finally, the analysis is found to be insensitive to the assimilation parameters. We conclude that the combination of a simplified ozone chemistry scheme with frequent satellite observations is a valuable tool for the long-term analysis of stratospheric and free-tropospheric ozone.

Download Full-text

Optimized regional and interannual variability of lightning in a global chemical transport model constrained by LIS/OTD satellite data

Journal of Geophysical Research Atmospheres ◽

10.1029/2012jd017934 ◽

2012 ◽

Vol 117 (D20) ◽

Cited By ~ 190

Author(s):

Lee T. Murray ◽

Daniel J. Jacob ◽

Jennifer A. Logan ◽

Rynda C. Hudman ◽

William J. Koshak

Keyword(s):

Interannual Variability ◽

Satellite Data ◽

Transport Model ◽

Chemical Transport ◽

Chemical Transport Model ◽

Global Chemical Transport Model

Download Full-text

A new diagnostic for tropospheric ozone production

10.5194/acp-2017-378 ◽

2017 ◽

Author(s):

Peter M. Edwards ◽

Mathew J. Evans

Keyword(s):

Air Quality ◽

Tropospheric Ozone ◽

Transport Model ◽

Chemical Transport ◽

Ozone Production ◽

Chemical Transport Model ◽

Organic Species ◽

Earth’S Climate ◽

Oxidation Of Organics

Abstract. Tropospheric ozone is important for the Earth’s climate and air quality. It is produced during the oxidation of organics in the presence of nitrogen oxides. Due to the range of organic species emitted and the chain like nature of their oxidation, this chemistry is complex and understanding the role of different processes (emission, deposition, chemistry) is difficult. We demonstrate a new methodology for diagnosing ozone production based on the processing of bonds contained within emitted molecules, the fate of which is determined by the conservation of spin of the bonding electrons. Using this methodology to diagnose ozone production in the GEOS-Chem chemical transport model, we demonstrate its advantages over the standard diagnostic. We show that the number of bonds emitted, their chemistry and lifetime, and feedbacks on OH are all important in determining the ozone production within the model and its sensitivity to changes. This insight may allow future model-model comparisons to better identify the root causes of model differences.

Download Full-text

Sensitivity of the recent methane budget to LMDz sub-grid scale physical parameterizations

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-11853-2015 ◽

2015 ◽

Vol 15 (8) ◽

pp. 11853-11888

Author(s):

R. Locatelli ◽

P. Bousquet ◽

M. Saunois ◽

F. Chevallier ◽

C. Cressot

Keyword(s):

Satellite Data ◽

Transport Model ◽

Deep Convection ◽

Chemical Transport ◽

Global Scale ◽

Methane Emissions ◽

Inverse Modelling ◽

Chemical Transport Model ◽

Methane Budget ◽

Physical Parameterizations

Abstract. With the densification of surface observing networks and the development of remote sensing of greenhouse gases from space, estimations of methane (CH4) sources and sinks by inverse modelling face new challenges. Indeed, the chemical transport model used to link the flux space with the mixing ratio space must be able to represent these different types of constraints for providing consistent flux estimations. Here we quantify the impact of sub-grid scale physical parameterization errors on the global methane budget inferred by inverse modelling using the same inversion set-up but different physical parameterizations within one chemical-transport model. Two different schemes for vertical diffusion, two others for deep convection, and one additional for thermals in the planetary boundary layer are tested. Different atmospheric methane datasets are used as constraints (surface observations or satellite retrievals). At the global scale, methane emissions differ, on average, from 4.1 Tg CH4 per year due to the use of different sub-grid scale parameterizations. Inversions using satellite total-column retrieved by GOSAT satellite are less impacted, at the global scale, by errors in physical parameterizations. Focusing on large-scale atmospheric transport, we show that inversions using the deep convection scheme of Emanuel (1991) derive smaller interhemispheric gradient in methane emissions. At regional scale, the use of different sub-grid scale parameterizations induces uncertainties ranging from 1.2 (2.7%) to 9.4% (14.2%) of methane emissions in Africa and Eurasia Boreal respectively when using only surface measurements from the background (extended) surface network. When using only satellite data, we show that the small biases found in inversions using GOSAT-CH4 data and a coarser version of the transport model were actually masking a poor representation of the stratosphere–troposphere gradient in the model. Improving the stratosphere–troposphere gradient reveals a larger bias in GOSAT-CH4 satellite data, which largely amplifies inconsistencies between surface and satellite inversions. A simple bias correction is proposed. The results of this work provide the level of confidence one can have for recent methane inversions relatively to physical parameterizations included in chemical-transport models.

Download Full-text