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Publications (10 of 20) Show all publications
Thomas, M., Devasthale, A., Koenigk, T., Wyser, K., Roberts, M., Roberts, C. & Lohmann, K. (2019). A statistical and process-oriented evaluation of cloud radiative effects in high-resolution global models. Geoscientific Model Development, 12(4), 1679-1702
Open this publication in new window or tab >>A statistical and process-oriented evaluation of cloud radiative effects in high-resolution global models
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2019 (English)In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 12, no 4, p. 1679-1702Article in journal (Refereed) Published
National Category
Climate Research
Research subject
Climate
Identifiers
urn:nbn:se:smhi:diva-5201 (URN)10.5194/gmd-12-1679-2019 (DOI)000466174100001 ()
Available from: 2019-05-07 Created: 2019-05-07 Last updated: 2019-05-07Bibliographically approved
Thomas, M., Devasthale, A., L'Ecuyer, T., Wang, S., Koenigk, T. & Wyser, K. (2019). Snowfall distribution and its response to the Arctic Oscillation: an evaluation of HighResMIP models in the Arctic using CPR/CloudSat observations. Geoscientific Model Development, 12(8), 3759-3772
Open this publication in new window or tab >>Snowfall distribution and its response to the Arctic Oscillation: an evaluation of HighResMIP models in the Arctic using CPR/CloudSat observations
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2019 (English)In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 12, no 8, p. 3759-3772Article in journal (Refereed) Published
National Category
Climate Research
Research subject
Climate
Identifiers
urn:nbn:se:smhi:diva-5414 (URN)10.5194/gmd-12-3759-2019 (DOI)000483069400001 ()
Available from: 2019-09-18 Created: 2019-09-18 Last updated: 2019-09-18Bibliographically approved
Thomas, M., Devasthale, A., Tjernstrom, M. & Ekman, A. M. L. (2019). The Relation Between Aerosol Vertical Distribution and Temperature Inversions in the Arctic in Winter and Spring. Geophysical Research Letters, 46(5), 2836-2845
Open this publication in new window or tab >>The Relation Between Aerosol Vertical Distribution and Temperature Inversions in the Arctic in Winter and Spring
2019 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 5, p. 2836-2845Article in journal (Refereed) Published
National Category
Climate Research
Research subject
Climate
Identifiers
urn:nbn:se:smhi:diva-5180 (URN)10.1029/2018GL081624 (DOI)000462612900056 ()
Available from: 2019-04-09 Created: 2019-04-09 Last updated: 2019-04-09
Thomas, M., Brannstrom, N., Persson, C., Grahn, H., von Schoenberg, P. & Robertson, L. (2017). Surface air quality implications of volcanic injection heights. Atmospheric Environment, 166, 510-518
Open this publication in new window or tab >>Surface air quality implications of volcanic injection heights
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2017 (English)In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 166, p. 510-518Article in journal (Refereed) Published
National Category
Environmental Sciences
Research subject
Environment
Identifiers
urn:nbn:se:smhi:diva-4316 (URN)10.1016/j.atmosenv.2017.07.045 (DOI)000411298800046 ()
Available from: 2017-11-13 Created: 2017-11-13 Last updated: 2017-11-13Bibliographically approved
Thomas, M. & Devasthale, A. (2017). Typical meteorological conditions associated with extreme nitrogen dioxide (NO2) pollution events over Scandinavia. Atmospheric Chemistry And Physics, 17(19), 12071-12080
Open this publication in new window or tab >>Typical meteorological conditions associated with extreme nitrogen dioxide (NO2) pollution events over Scandinavia
2017 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 17, no 19, p. 12071-12080Article in journal (Refereed) Published
National Category
Environmental Sciences
Research subject
Environment
Identifiers
urn:nbn:se:smhi:diva-4307 (URN)10.5194/acp-17-12071-2017 (DOI)000412824300001 ()
Available from: 2017-11-13 Created: 2017-11-13 Last updated: 2017-11-13Bibliographically approved
Marecal, V., Peuch, V.-H. -., Andersson, C., Andersson, S., Arteta, J., Beekmann, M., . . . Ung, A. (2015). A regional air quality forecasting system over Europe: the MACC-II daily ensemble production. Geoscientific Model Development, 8(9), 2777-2813
Open this publication in new window or tab >>A regional air quality forecasting system over Europe: the MACC-II daily ensemble production
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2015 (English)In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 8, no 9, p. 2777-2813Article in journal (Refereed) Published
Abstract [en]

This paper describes the pre-operational analysis and forecasting system developed during MACC (Monitoring Atmospheric Composition and Climate) and continued in the MACC-II (Monitoring Atmospheric Composition and Climate: Interim Implementation) European projects to provide air quality services for the European continent. This system is based on seven state-of-the art models developed and run in Europe (CHIMERE, EMEP, EURAD-IM, LOTOS-EUROS, MATCH, MOCAGE and SILAM). These models are used to calculate multi-model ensemble products. The paper gives an overall picture of its status at the end of MACCII (summer 2014) and analyses the performance of the multi-model ensemble. The MACC-II system provides daily 96 h forecasts with hourly outputs of 10 chemical species/aerosols (O-3, NO2, SO2, CO, PM10, PM2.5, NO, NH3, total NMVOCs (non-methane volatile organic compounds) and PAN + PAN precursors) over eight vertical levels from the surface to 5 km height. The hourly analysis at the surface is done a posteriori for the past day using a selection of representative air quality data from European monitoring stations. The performance of the system is assessed daily, weekly and every 3 months (seasonally) through statistical indicators calculated using the available representative air quality data from European monitoring stations. Results for a case study show the ability of the ensemble median to forecast regional ozone pollution events. The seasonal performances of the individual models and of the multi-model ensemble have been monitored since September 2009 for ozone, NO2 and PM10. The statistical indicators for ozone in summer 2014 show that the ensemble median gives on average the best performances compared to the seven models. There is very little degradation of the scores with the forecast day but there is a marked diurnal cycle, similarly to the individual models, that can be related partly to the prescribed diurnal variations of anthropogenic emissions in the models. During summer 2014, the diurnal ozone maximum is underestimated by the ensemble median by about 4 mu g m(-3) on average. Locally, during the studied ozone episodes, the maxima from the ensemble median are often lower than observations by 30-50 mu g m(-3). Overall, ozone scores are generally good with average values for the normalised indicators of 0.14 for the modified normalised mean bias and of 0.30 for the fractional gross error. Tests have also shown that the ensemble median is robust to reduction of ensemble size by one, that is, if predictions are unavailable from one model. Scores are also discussed for PM10 for winter 2013-1014. There is an underestimation of most models leading the ensemble median to a mean bias of 4.5 mu g m(-3). The ensemble median fractional gross error is larger for PM10 (similar to 0.52) than for ozone and the correlation is lower (similar to 0.35 for PM10 and similar to 0.54 for ozone). This is related to a larger spread of the seven model scores for PM10 than for ozone linked to different levels of complexity of aerosol representation in the individual models. In parallel, a scientific analysis of the results of the seven models and of the ensemble is also done over the Mediterranean area because of the specificity of its meteorology and emissions. The system is robust in terms of the production availability. Major efforts have been done in MACC-II towards the operationalisation of all its components. Foreseen developments and research for improving its performances are discussed in the conclusion.

National Category
Environmental Sciences
Research subject
Environment
Identifiers
urn:nbn:se:smhi:diva-1943 (URN)10.5194/gmd-8-2777-2015 (DOI)000364325700005 ()
Available from: 2016-04-29 Created: 2016-03-03 Last updated: 2017-11-30Bibliographically approved
Thomas, M. A., Kahnert, M., Andersson, C., Kokkola, H., Hansson, U., Jones, C., . . . Devasthale, A. (2015). Integration of prognostic aerosol-cloud interactions in a chemistry transport model coupled offline to a regional climate model. Geoscientific Model Development, 8(6), 1885-1898
Open this publication in new window or tab >>Integration of prognostic aerosol-cloud interactions in a chemistry transport model coupled offline to a regional climate model
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2015 (English)In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 8, no 6, p. 1885-1898Article in journal (Refereed) Published
Abstract [en]

To reduce uncertainties and hence to obtain a better estimate of aerosol (direct and indirect) radiative forcing, next generation climate models aim for a tighter coupling between chemistry transport models and regional climate models and a better representation of aerosol-cloud interactions. In this study, this coupling is done by first forcing the Rossby Center regional climate model (RCA4) with ERA-Interim lateral boundaries and sea surface temperature (SST) using the standard cloud droplet number concentration (CDNC) formulation (hereafter, referred to as the 'stand-alone RCA4 version' or 'CTRL' simulation). In the stand-alone RCA4 version, CDNCs are constants distinguishing only between land and ocean surface. The meteorology from this simulation is then used to drive the chemistry transport model, Multiple-scale Atmospheric Transport and Chemistry (MATCH), which is coupled online with the aerosol dynamics model, Sectional Aerosol module for Large Scale Applications (SALSA). CDNC fields obtained from MATCH-SALSA are then fed back into a new RCA4 simulation. In this new simulation (referred to as 'MOD' simulation), all parameters remain the same as in the first run except for the CDNCs provided by MATCH-SALSA. Simulations are carried out with this model setup for the period 2005-2012 over Europe, and the differences in cloud microphysical properties and radiative fluxes as a result of local CDNC changes and possible model responses are analysed. Our study shows substantial improvements in cloud microphysical properties with the input of the MATCH-SALSA derived 3-D CDNCs compared to the stand-alone RCA4 version. This model setup improves the spatial, seasonal and vertical distribution of CDNCs with a higher concentration observed over central Europe during boreal summer (JJA) and over eastern Europe and Russia during winter (DJF). Realistic cloud droplet radii (CD radii) values have been simulated with the maxima reaching 13 mu m, whereas in the stand-alone version the values reached only 5 mu m. A substantial improvement in the distribution of the cloud liquid-water paths (CLWP) was observed when compared to the satellite retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) for the boreal summer months. The median and standard deviation values from the 'MOD' simulation are closer to observations than those obtained using the stand-alone RCA4 version. These changes resulted in a significant decrease in the total annual mean net fluxes at the top of the atmosphere (TOA) by -5 W m(-2) over the domain selected in the study. The TOA net fluxes from the 'MOD' simulation show a better agreement with the retrievals from the Clouds and the Earth's Radiant Energy System (CERES) instrument. The aerosol indirect effects are estimated in the 'MOD' simulation in comparison to the pre-industrial aerosol emissions (1900). Our simulations estimated the domain averaged annual mean total radiative forcing of -0.64 W m(-2) with a larger contribution from the first indirect aerosol effect (-0.57 W m(-2)) than from the second indirect aerosol effect (-0.14 W m(-2)).

National Category
Climate Research
Research subject
Climate
Identifiers
urn:nbn:se:smhi:diva-1972 (URN)10.5194/gmd-8-1885-2015 (DOI)000357125000019 ()
Available from: 2016-04-26 Created: 2016-03-03 Last updated: 2017-11-30Bibliographically approved
Andersson, C., Bergström, R., Bennet, C., Robertson, L., Thomas, M., Korhonen, H., . . . Kokkola, H. (2015). MATCH-SALSA - Multi-scale Atmospheric Transport and CHemistry model coupled to the SALSA aerosol microphysics model - Part 1: Model description and evaluation. Geoscientific Model Development, 8(2), 171-189
Open this publication in new window or tab >>MATCH-SALSA - Multi-scale Atmospheric Transport and CHemistry model coupled to the SALSA aerosol microphysics model - Part 1: Model description and evaluation
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2015 (English)In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 8, no 2, p. 171-189Article in journal (Refereed) Published
Abstract [en]

We have implemented the sectional aerosol dynamics model SALSA (Sectional Aerosol module for Large Scale Applications) in the European-scale chemistry-transport model MATCH (Multi-scale Atmospheric Transport and Chemistry). The new model is called MATCH-SALSA. It includes aerosol microphysics, with several formulations for nucleation, wet scavenging and condensation. The model reproduces observed higher particle number concentration (PNC) in central Europe and lower concentrations in remote regions. The modeled PNC size distribution peak occurs at the same or smaller particle size as the observed peak at four measurement sites spread across Europe. Total PNC is underestimated at northern and central European sites and accumulation-mode PNC is underestimated at all investigated sites. The low nucleation rate coefficient used in this study is an important reason for the underestimation. On the other hand, the model performs well for particle mass (including secondary inorganic aerosol components), while elemental and organic carbon concentrations are underestimated at many of the sites. Further development is needed, primarily for treatment of secondary organic aerosol, in terms of biogenic emissions and chemical transformation. Updating the biogenic secondary organic aerosol (SOA) scheme will likely have a large impact on modeled PM2.5 and also affect the model performance for PNC through impacts on nucleation and condensation.

National Category
Environmental Sciences
Research subject
Environment
Identifiers
urn:nbn:se:smhi:diva-2010 (URN)10.5194/gmd-8-171-2015 (DOI)000350557800003 ()
Available from: 2016-04-06 Created: 2016-03-03 Last updated: 2017-11-30Bibliographically approved
Mahajan, A. S., Fadnavis, S., Thomas, M. A., Pozzoli, L., Gupta, S., Royer, S.-J., . . . Simo, R. (2015). Quantifying the impacts of an updated global dimethyl sulfide climatology on cloud microphysics and aerosol radiative forcing. Journal of Geophysical Research - Atmospheres, 120(6), 2524-2536
Open this publication in new window or tab >>Quantifying the impacts of an updated global dimethyl sulfide climatology on cloud microphysics and aerosol radiative forcing
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2015 (English)In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 120, no 6, p. 2524-2536Article in journal (Refereed) Published
Abstract [en]

One of the critical parameters in assessing the global impacts of dimethyl sulfide (DMS) on cloud properties and the radiation budget is the estimation of phytoplankton-induced ocean emissions, which are derived from prescribed, climatological surface seawater DMS concentrations. The most widely used global ocean DMS climatology was published 15 years ago and has recently been updated using a much larger database of observations. The updated climatology displays significant differences in terms of the global distribution and regional monthly averages of sea surface DMS. In this study, we use the ECHAM5-HAMMOZ aerosol-chemistry-climate general circulation model to quantify the influence of the updated DMS climatology in computed atmospheric properties, namely, the spatial and temporal distributions of atmospheric DMS concentration, sulfuric acid concentration, sulfate aerosols, number of activated aerosols, cloud droplet number concentration, and the aerosol radiative forcing at the top of the atmosphere. Significant differences are observed for all the modeled variables. Comparison with observations of atmospheric DMS and total sulfate also shows that in places with large DMS emissions, the updated climatology shows a better match with the observations. This highlights the importance of using the updated climatology for projecting future impacts of oceanic DMS emissions, especially considering that the relative importance of the natural sulfur fluxes is likely to increase due to legislation to clean up anthropogenic emissions. The largest estimated differences are in the Southern Ocean, Indian Ocean, and parts of the Pacific Ocean, where the climatologies differ in seasonal concentrations over large geographical areas. The model results also indicate that the former DMS climatology underestimated the effect of DMS on the globally averaged annual aerosol radiative forcing at the top of the atmosphere by about 20%.

National Category
Environmental Sciences
Research subject
Environment
Identifiers
urn:nbn:se:smhi:diva-1991 (URN)10.1002/2014JD022687 (DOI)000353061800023 ()
Available from: 2016-04-25 Created: 2016-03-03 Last updated: 2017-11-30Bibliographically approved
Thomas, M. A. & Devasthale, A. (2014). Sensitivity of free tropospheric carbon monoxide to atmospheric weather states and their persistency: an observational assessment over the Nordic countries. Atmospheric Chemistry And Physics, 14(21), 11545-11555
Open this publication in new window or tab >>Sensitivity of free tropospheric carbon monoxide to atmospheric weather states and their persistency: an observational assessment over the Nordic countries
2014 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 14, no 21, p. 11545-11555Article in journal (Refereed) Published
Abstract [en]

Among various factors that influence the long-range transport of pollutants in the free troposphere (FT), the prevailing atmospheric weather states probably play the most important role in governing characteristics and efficacy of such transport. The weather states, such as a particular wind pattern, cyclonic or anticyclonic conditions, and their degree of persistency determine the spatio-temporal distribution and the final fate of the pollutants. This is especially true in the case of Nordic countries, where baroclinic disturbances and associated weather fronts primarily regulate local meteorology, in contrast to the lower latitudes where a convective paradigm plays a similarly important role. Furthermore, the long-range transport of pollutants in the FT has significant contribution to the total column burden over the Nordic countries. However, there is insufficient knowledge on the large-scale co-variability of pollutants in the FT and atmospheric weather states based solely on observational data over this region. The present study attempts to quantify and understand this statistical co-variability while providing relevant meteorological background. To that end, we select eight weather states that predominantly occur over the Nordic countries and three periods of their persistency (3 days, 5 days, and 7 days), thus providing in total 24 cases to investigate sensitivity of free tropospheric carbon monoxide, an ideal tracer for studying pollutant transport, to these selected weather states. The eight states include four dominant wind directions (namely, NW, NE, SE and SW), cyclonic and anticyclonic conditions, and the enhanced positive and negative phases of the North Atlantic Oscillation (NAO). For our sensitivity analysis, we use recently released Version 6 retrievals of CO at 500 hPa from the Atmospheric Infrared Sounder (AIRS) onboard Aqua satellite covering the 11-year period from September 2002 through August 2013 and winds from the ECMWF's ERA-Interim project to classify weather states for the same 11-year period. We show that, among the various weather states studied here, southeasterly winds lead to highest observed CO anomalies (up to +8%) over the Nordic countries while transporting pollution from the central and eastern parts of Europe. The second (up to +4%) and third highest (up to +2.5%) CO anomalies are observed when winds are northwesterly (facilitating inter-continental transport from polluted North American regions) and during the enhanced positive phase of the NAO respectively. Higher than normal CO anomalies are observed during anticyclonic conditions (up to +1%) compared to cyclonic conditions. The cleanest conditions are observed when winds are northeasterly and during the enhanced negative phases of the NAO, when relatively clean Arctic air masses are transported over the Nordic regions in the both cases. In the case of nearly all weather states, the CO anomalies consistently continue to increase or decrease as the degree of persistency of a weather state is increased. The results of this sensitivity study further provide an observational basis for the process-oriented evaluation of chemistry transport models, especially with regard to the representation of large-scale coupling of chemistry and local weather states and its role in the long-range transport of pollutants in such models.

National Category
Meteorology and Atmospheric Sciences
Research subject
Environment
Identifiers
urn:nbn:se:smhi:diva-136 (URN)10.5194/acp-14-11545-2014 (DOI)000344985700001 ()
Available from: 2015-04-09 Created: 2015-03-26 Last updated: 2017-12-04Bibliographically approved
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