Abstract
Abstract. We provide a comprehensive description of the high-resolution version of the TM5-MP global chemistry transport model, which is to be employed for deriving highly resolved vertical profiles of nitrogen dioxide (NO2), formaldehyde (CH2O), and sulfur dioxide (SO2) for use in satellite retrievals from platforms such as the Ozone Monitoring Instrument (OMI) and the Sentinel-5 Precursor, and the TROPOspheric Monitoring Instrument (tropOMI). Comparing simulations conducted at horizontal resolutions of 3° × 2° and 1° × 1° reveals differences of ±20 % exist in the global seasonal distribution of 222Rn, being larger near specific coastal locations and tropical oceans. For tropospheric ozone (O3), analysis of the chemical budget terms shows that the impact on globally integrated photolysis rates is rather low, in spite of the higher spatial variability of meteorological data fields from ERA-Interim at 1° × 1°. Surface concentrations of O3 in high-NOx regions decrease between 5 and 10 % at 1° × 1° due to a reduction in NOx recycling terms and an increase in the associated titration term of O3 by NO. At 1° × 1°, the net global stratosphere–troposphere exchange of O3 decreases by ∼ 7 %, with an associated shift in the hemispheric gradient. By comparing NO, NO2, HNO3 and peroxy-acetyl-nitrate (PAN) profiles against measurement composites, we show that TM5-MP captures the vertical distribution of NOx and long-lived NOx reservoirs at background locations, again with modest changes at 1° × 1°. Comparing monthly mean distributions in lightning NOx and applying ERA-Interim convective mass fluxes, we show that the vertical re-distribution of lightning NOx changes with enhanced release of NOx in the upper troposphere. We show that surface mixing ratios in both NO and NO2 are generally underestimated in both low- and high-NOx scenarios. For Europe, a negative bias exists for [NO] at the surface across the whole domain, with lower biases at 1° × 1° at only ∼ 20 % of sites. For NO2, biases are more variable, with lower (higher) biases at 1° × 1° occurring at ∼ 35 % ( ∼ 20 %) of sites, with the remainder showing little change. For CH2O, the impact of higher resolution on the chemical budget terms is rather modest, with changes of less than 5 %. The simulated vertical distribution of CH2O agrees reasonably well with measurements in pristine locations, although column-integrated values are generally underestimated relative to satellite measurements in polluted regions. For SO2, the performance at 1° × 1° is principally governed by the quality of the emission inventory, with limited improvements in the site-specific biases, with most showing no significant improvement. For the vertical column, improvements near strong source regions occur which reduce the biases in the integrated column. For remote regions missing biogenic source terms are inferred.
Highlights
One application of chemistry transport models (CTMs) is to provide accurate vertical and horizontal global distributions of trace gases such as ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2) and formaldehyde (CH2O) that are used as a priori best guesses in the retrievals of tropospheric abundances from instruments mounted on Earth-orbiting satellites such as the Tropospheric Emission Sounder (TES; Worden et al, 2007) Global Ozone Monitoring Experiment (GOME), Published by Copernicus Publications on behalf of the European Geosciences Union
A more regional fine structure can be seen at 1◦ × 1◦, these seasonal averages show that the small perturbations in JNO2 shown in Fig. S6 extend to the global scale, leading to only modest changes in the tropospheric lifetime of NO2
In this paper we have provided a comprehensive description of the high-resolution 1◦ × 1◦ version of TM5, which is to be used for the purpose of providing a priori columns for the satellite retrieval of trace gas columns of NO2, CH2O and SO2
Summary
One application of chemistry transport models (CTMs) is to provide accurate vertical and horizontal global distributions of trace gases such as ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2) and formaldehyde (CH2O) that are used as a priori best guesses in the retrievals of tropospheric abundances from instruments mounted on Earth-orbiting satellites such as the Tropospheric Emission Sounder (TES; Worden et al, 2007) Global Ozone Monitoring Experiment (GOME), Published by Copernicus Publications on behalf of the European Geosciences Union. Russell et al, 2011; Zhou et al, 2012; Vinken et al, 2014), at the global scale the CTM resolutions employed are still rather coarse (between 1.1 and 4.0◦ in latitude and between 1.1 and 6◦ in longitude), resulting in “footprints” which aggregate hundreds of kilometres in area This has limitations as the resulting total columns are sensitive to topography, surface albedo and the shape of the a priori vertical profiles themselves. Boersma et al, 2008; Heckel et al, 2011; Russell et al, 2011) and imposes limitations on capturing the regional-scale variability in short-lived trace gas abundances observed from high-resolution satellite instruments such as the OMI This lack of spatial detail is relevant for situations where strong spatio-temporal variability in the vertical distribution of NO2, SO2, and CH2O can be expected.
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