scholarly journals Transport model diagnosis of the mean age of air derived from stratospheric samples in the tropics

2020 ◽  
Author(s):  
Hanh T. Nguyen ◽  
Kentaro Ishijima ◽  
Satoshi Sugawara ◽  
Fumio Hasebe
Keyword(s):  
Atmospheric Chemistry ◽  
Transport Model ◽  
Lagrangian Method ◽  
Single Model ◽  
Chemistry Transport Model ◽  
Air Samples ◽  
The Mean ◽  
The Tropics ◽  
Model Diagnosis ◽  
Diffusive Processes

Abstract. Stratospheric profiles of the mean age of air estimated from cryogenic air samples acquired during the CUBE/Biak field campaign over Indonesia are investigated with the aid of an atmospheric chemistry transport model nudged to ERA-Interim meteorological fields. Application of the boundary impulse response (BIR) method and Lagrangian backward trajectories to the transport field simulated by a single model prove useful in interpreting the observational results, which include discrepancies between CO2- and SF6-derived mean ages. This may be because the BIR method takes unresolved diffusive processes into account while the Lagrangian method distinguishes the pathways the air parcels have taken before reaching the sample site. The capability to estimate the vertical profiles of the clock tracer concentrations and the water vapor “tape recorder” is another advantage of the Lagrangian method, confirming the reality of the trajectory calculations. The profile of CO2-mean age is reproduced reasonably well by trajectory-derived mean age, while BIR-derived mean age is much greater than CO2 age at 28 and 29 km, possibly due to high diffusivity in the transport model. On the other hand, SF6 age is reproducible only in the lower stratosphere, but far exceeds the trajectory-derived mean age above 25 km. As air parcels of mesospheric origin are missing in the Lagrangian age estimation, this discrepancy, together with the fact that the observed SF6 concentrations are much lower than the trajectory-derived values in this height region, is consistent with the idea that the stratospheric air samples are mixed with SF6-depleted mesospheric air, leading to overestimation of the mean age.

scholarly journals Impact of the new HNO<sub>3</sub>-forming channel of the HO<sub>2</sub>+NO reaction on tropospheric HNO<sub>3</sub>, NO<sub>x</sub>, HO<sub>x</sub> and ozone

2008 ◽  
Vol 8 (14) ◽  
pp. 4061-4068 ◽  
Author(s):  
D. Cariolle ◽  
M. J. Evans ◽  
M. P. Chipperfield ◽  
N. Butkovskaya ◽  
A. Kukui ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Transport Model ◽  
Chemical Transport Model ◽  
Temperature Dependent ◽  
Upper Troposphere ◽  
The Mean ◽  
The Tropics ◽  
The Impact

Abstract. We have studied the impact of the recently observed reaction NO+HO2→HNO3 on atmospheric chemistry. A pressure and temperature-dependent parameterisation of this minor channel of the NO+HO2→NO2+OH reaction has been included in both a 2-D stratosphere-troposphere model and a 3-D tropospheric chemical transport model (CTM). Significant effects on the nitrogen species and hydroxyl radical concentrations are found throughout the troposphere, with the largest percentage changes occurring in the tropical upper troposphere (UT). Including the reaction leads to a reduction in NOx everywhere in the troposphere, with the largest decrease of 25% in the tropical and Southern Hemisphere UT. The tropical UT also has a corresponding large increase in HNO3 of 25%. OH decreases throughout the troposphere with the largest reduction of over 20% in the tropical UT. The mean global decrease in OH is around 13%, which is very large compared to the impact that typical photochemical revisions have on this modelled quantity. This OH decrease leads to an increase in CH4 lifetime of 5%. Due to the impact of decreased NOx on the OH:HO2 partitioning, modelled HO2 actually increases in the tropical UT on including the new reaction. The impact on tropospheric ozone is a decrease in the range 5 to 12%, with the largest impact in the tropics and Southern Hemisphere. Comparison with observations shows that in the region of largest changes, i.e. the tropical UT, the inclusion of the new reaction tends to degrade the model agreement. Elsewhere the model comparisons are not able to critically assess the impact of including this reaction. Only small changes are calculated in the minor species distributions in the stratosphere.

scholarly journals Quantifying pollution transport from the Asian monsoon anticyclone into the lower stratosphere

2017 ◽  
Vol 17 (11) ◽  
pp. 7055-7066 ◽  
Author(s):  
Felix Ploeger ◽  
Paul Konopka ◽  
Kaley Walker ◽  
Martin Riese
Keyword(s):  
Asian Monsoon ◽  
Lower Stratosphere ◽  
Transport Model ◽  
Monsoon Circulation ◽  
Pollution Transport ◽  
Chemistry Transport Model ◽  
Transport Pathways ◽  
Air Mass ◽  
Mass Fractions ◽  
The Tropics

Abstract. Pollution transport from the surface to the stratosphere within the Asian monsoon circulation may cause harmful effects on stratospheric chemistry and climate. Here, we investigate air mass transport from the monsoon anticyclone into the stratosphere using a Lagrangian chemistry transport model. We show how two main transport pathways from the anticyclone emerge: (i) into the tropical stratosphere (tropical pipe), and (ii) into the Northern Hemisphere (NH) extratropical lower stratosphere. Maximum anticyclone air mass fractions reach around 5 % in the tropical pipe and 15 % in the extratropical lowermost stratosphere over the course of a year. The anticyclone air mass fraction correlates well with satellite hydrogen cyanide (HCN) and carbon monoxide (CO) observations, confirming that pollution is transported deep into the tropical stratosphere from the Asian monsoon anticyclone. Cross-tropopause transport occurs in a vertical chimney, but with the pollutants transported quasi-horizontally along isentropes above the tropopause into the tropics and NH.

scholarly journals Quantifying pollution transport from the Asian monsoon anticyclone into the lower stratosphere

2017 ◽  
Author(s):  
Felix Ploeger ◽  
Paul Konopka ◽  
Kaley Walker ◽  
Martin Riese
Keyword(s):  
Asian Monsoon ◽  
Lower Stratosphere ◽  
Transport Model ◽  
Monsoon Circulation ◽  
Pollution Transport ◽  
Chemistry Transport Model ◽  
Transport Pathways ◽  
Air Mass ◽  
Mass Fractions ◽  
The Tropics

Abstract. Pollution transport from the surface to the stratosphere within the Asian monsoon circulation may cause harmful effects on stratospheric chemistry and climate. Here, we investigate air mass transport from the monsoon anticyclone into the stratosphere using a Lagrangian chemistry transport model. We show how two main transport pathways from the anticyclone emerge: (i) into the tropical stratosphere (tropical pipe), and (ii) into the Northern hemisphere (NH) extra-tropical lower stratosphere. Maximum anticyclone air mass fractions reach around 5 % in the tropical pipe and 15 % in the extra-tropical lowermost stratosphere over the course of a year. The anticyclone air mass fraction correlates well with satellite hydrogen cyanide (HCN) and carbon monoxide (CO) observations, corroborating that pollution is transported deep into the tropical stratosphere from the Asian monsoon anticyclone. Cross-tropopause transport occurs in a vertical chimney, but with the emissions transported quasi-horizontally along isentropes above the tropopause into the tropics and NH.

scholarly journals Modelling atmospheric OH-reactivity in a boreal forest ecosystem

2011 ◽  
Vol 11 (18) ◽  
pp. 9709-9719 ◽  
Author(s):  
D. Mogensen ◽  
S. Smolander ◽  
A. Sogachev ◽  
L. Zhou ◽  
V. Sinha ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Transport Model ◽  
Inorganic Compounds ◽  
Chemistry Transport Model ◽  
One Dimensional ◽  
Inorganic Species ◽  
Individual Contributions ◽  
The Individual

Abstract. We have modelled the total atmospheric OH-reactivity in a boreal forest and investigated the individual contributions from gas phase inorganic species, isoprene, monoterpenes, and methane along with other important VOCs. Daily and seasonal variation in OH-reactivity for the year 2008 was examined as well as the vertical OH-reactivity profile. We have used SOSA; a one dimensional vertical chemistry-transport model (Boy et al., 2011a) together with measurements from Hyytiälä, SMEAR II station, Southern Finland, conducted in August 2008. Model simulations only account for ~30–50% of the total measured OH sink, and in our opinion, the reason for missing OH-reactivity is due to unmeasured unknown BVOCs, and limitations in our knowledge of atmospheric chemistry including uncertainties in rate constants. Furthermore, we found that the OH-reactivity correlates with both organic and inorganic compounds and increases during summer. The summertime canopy level OH-reactivity peaks during night and the vertical OH-reactivity decreases with height.

scholarly journals Operational total and tropospheric NO<sub>2</sub> column retrieval for GOME-2

2011 ◽  
Vol 4 (7) ◽  
pp. 1491-1514 ◽  
Author(s):  
P. Valks ◽  
G. Pinardi ◽  
A. Richter ◽  
J.-C. Lambert ◽  
N. Hao ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Transport Model ◽  
Optical Absorption Spectroscopy ◽  
Chemistry Transport Model ◽  
Air Mass ◽  
Cloud Properties ◽  
The Pacific ◽  
Tropospheric No2 ◽  
Data Processor ◽  
Radiance Data

Abstract. This paper presents the algorithm for the operational near real time retrieval of total and tropospheric NO2 columns from the Global Ozone Monitoring Experiment (GOME-2). The retrieval is performed with the GOME Data Processor (GDP) version 4.4 as used by the EUMETSAT Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M-SAF). The differential optical absorption spectroscopy (DOAS) method is used to determine NO2 slant columns from GOME-2 (ir)radiance data in the 425–450 nm range. Initial total NO2 columns are computed using stratospheric air mass factors, and GOME-2 derived cloud properties are used to calculate the air mass factors for scenarios in the presence of clouds. To obtain the stratospheric NO2 component, a spatial filtering approach is used, which is shown to be an improvement on the Pacific reference sector method. Tropospheric air mass factors are computed using monthly averaged NO2 profiles from the MOZART-2 chemistry transport model. An error analysis shows that the random error in the GOME-2 NO2 slant columns is approximately 0.45 × 1015 molec cm−2. As a result of the improved quartz diffuser plate used in the GOME-2 instrument, the systematic error in the slant columns is strongly reduced compared to GOME/ERS-2. The estimated uncertainty in the GOME-2 tropospheric NO2 column for polluted conditions ranges from 40 to 80 %. An end-to-end ground-based validation approach for the GOME-2 NO2 columns is illustrated based on multi-axis MAXDOAS measurements at the Observatoire de Haute Provence (OHP). The GOME-2 stratospheric NO2 columns are found to be in good overall agreement with coincident ground-based measurements at OHP. A time series of the MAXDOAS and the GOME-2 tropospheric NO2 columns shows that pollution episodes at OHP are well captured by GOME-2. Monthly mean tropospheric columns are in very good agreement, with differences generally within 0.5 × 1015 molec cm−2.

scholarly journals Global stratospheric fluorine inventory for 2004–2009 from Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) measurements and SLIMCAT model simulations

2014 ◽  
Vol 14 (1) ◽  
pp. 267-282 ◽  
Author(s):  
A. T. Brown ◽  
M. P. Chipperfield ◽  
N. A. D. Richards ◽  
C. Boone ◽  
P. F. Bernath
Keyword(s):  
Atmospheric Chemistry ◽  
Radiative Forcing ◽  
Transport Model ◽  
Similar Rate ◽  
Montreal Protocol ◽  
Negative Slope ◽  
Mixing Ratios ◽  
Inorganic Species ◽  
The Tropics ◽  
The Impact

Abstract. Fluorine-containing species can be extremely effective atmospheric greenhouse gases. We present fluorine budgets using organic and inorganic species retrieved by the ACE-FTS satellite instrument supplemented with output from the SLIMCAT 3-D chemical transport model. The budgets are calculated between 2004 and 2009 for a number of latitude bands: 70–30° N, 30–00° N, 00° N–30° S, and 30–70° S. At lower altitudes total fluorine profiles are dominated by the contribution from CFC-12, up to an altitude of 20 km in the extra-tropics and 29 km in the tropics; above these altitudes the profiles are dominated by hydrogen fluoride (HF). Our data show that total fluorine profiles at all locations have a negative slope with altitude, providing evidence that overall fluorine emissions (measured by their F content) have been increasing with time. Total stratospheric fluorine is increasing at a similar rate in the tropics: 32.5 ± 4.9 ppt yr−1 (1.31 ± 0.20% per year) in the Northern Hemisphere (NH) and 29.8 ± 5.3 ppt yr−1 (1.21 ± 0.22% per year) in the Southern Hemisphere (SH). Extra-tropical total stratospheric fluorine is also increasing at a similar rate in both the NH and SH: 28.3 ± 2.7 ppt per year (1.12 ± 0.11% per year) in the NH and 24.3 ± 3.1 ppt per year (0.96 ± 0.12% per year) in the SH. The calculation of radiative efficiency-weighted total fluorine allows the changes in radiative forcing between 2004 and 2009 to be calculated. These results show an increase in radiative forcing of between 0.23 ± 0.11% per year and 0.45 ± 0.11% per year, due to the increase in fluorine-containing species during this time. The decreasing trends in the mixing ratios of halons and chlorofluorocarbons (CFCs), due to their prohibition under the Montreal Protocol, have suppressed an increase in total fluorine caused by increasing mixing ratios of hydrofluorocarbons (HFCs). This has reduced the impact of fluorine-containing species on global warming.

scholarly journals Improving the prediction of an atmospheric chemistry transport model using gradient-boosted regression trees

2020 ◽  
Vol 20 (13) ◽  
pp. 8063-8082 ◽  
Author(s):  
Peter D. Ivatt ◽  
Mathew J. Evans
Keyword(s):  
Root Mean Square Error ◽  
Mean Square Error ◽  
Root Mean Square ◽  
Atmospheric Chemistry ◽  
Transport Model ◽  
Mean Square ◽  
Model Bias ◽  
Chemistry Transport Model ◽  
Pearson's R ◽  
Process Based Models

Abstract. Predictions from process-based models of environmental systems are biased, due to uncertainties in their inputs and parameterizations, reducing their utility. We develop a predictor for the bias in tropospheric ozone (O3, a key pollutant) calculated by an atmospheric chemistry transport model (GEOS-Chem), based on outputs from the model and observations of ozone from both the surface (EPA, EMEP, and GAW) and the ozone-sonde networks. We train a gradient-boosted decision tree algorithm (XGBoost) to predict model bias (model divided by observation), with model and observational data for 2010–2015, and then we test the approach using the years 2016–2017. We show that the bias-corrected model performs considerably better than the uncorrected model. The root-mean-square error is reduced from 16.2 to 7.5 ppb, the normalized mean bias is reduced from 0.28 to −0.04, and Pearson's R is increased from 0.48 to 0.84. Comparisons with observations from the NASA ATom flights (which were not included in the training) also show improvements but to a smaller extent, reducing the root-mean-square error (RMSE) from 12.1 to 10.5 ppb, reducing the normalized mean bias (NMB) from 0.08 to 0.06, and increasing Pearson's R from 0.76 to 0.79. We attribute the smaller improvements to the lack of routine observational constraints for much of the remote troposphere. We show that the method is robust to variations in the volume of training data, with approximately a year of data needed to produce useful performance. Data denial experiments (removing observational sites from the algorithm training) show that information from one location (for example Europe) can reduce the model bias over other locations (for example North America) which might provide insights into the processes controlling the model bias. We explore the choice of predictor (bias prediction versus direct prediction) and conclude both may have utility. We conclude that combining machine learning approaches with process-based models may provide a useful tool for improving these models.

scholarly journals Satellite observations of stratospheric carbonyl fluoride

2014 ◽  
Vol 14 (12) ◽  
pp. 18127-18180 ◽  
Author(s):  
J. J. Harrison ◽  
M. P. Chipperfield ◽  
A. Dudhia ◽  
S. Cai ◽  
S. Dhomse ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Thermal Emission ◽  
Transport Model ◽  
Michelson Interferometer ◽  
Three Dimensional ◽  
Chemical Transport Model ◽  
Northern Latitudes ◽  
Stratospheric Dynamics ◽  
The Tropics ◽  
Carbonyl Fluoride

Abstract. The vast majority of emissions of fluorine-containing molecules are anthropogenic in nature, e.g. chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). These molecules slowly degrade in the atmosphere leading to the formation of HF, COF2, and COClF, which are the main fluorine-containing species in the stratosphere. Ultimately both COF2 and COClF further degrade to form HF, an almost permanent reservoir of stratospheric fluorine due to its extreme stability. Carbonyl fluoride (COF2) is the second most abundant stratospheric "inorganic" fluorine reservoir with main sources being the atmospheric degradation of CFC-12 (CCl2F2), HCFC-22 (CHF2Cl), and CFC-113 (CF2ClCFCl2). This work reports the first global distributions of carbonyl fluoride in the Earth's atmosphere using infrared satellite remote-sensing measurements by the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS), which has been recording atmospheric spectra since 2004, and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument, which has recorded thermal emission atmospheric spectra between 2002 and 2012. The observations reveal a high degree of seasonal and latitudinal variability over the course of a year. These have been compared with the output of SLIMCAT, a state-of-the-art three-dimensional chemical transport model. In general the observations agree well with each other and compare well with SLIMCAT, although MIPAS is biased high by as much as ~30%. Between January 2004 and September 2010 COF2 grew most rapidly at altitudes above ~25 km in the southern latitudes and at altitudes below ~25 km in the northern latitudes, whereas it declined most rapidly in the tropics. These variations are attributed to changes in stratospheric dynamics over the observation period. The overall COF2 global trend over this period is calculated as 0.85 ± 0.34 % year−1 (MIPAS), 0.30 ± 0.44% year−1 (ACE), and 0.88% year−1 (SLIMCAT).

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