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Estimating trajectory uncertainties due to flow dependent errors in the atmospheric analysis
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
2009 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 9, no 22, 8857-8867 p.Article in journal (Refereed) Published
Abstract [en]

The uncertainty of a calculated trajectory is dependent on the uncertainty in the atmospheric analysis. Using the Ensemble Transform method (originally adapted for ensemble forecasting) we sample the analysis uncertainty in order to create an ensemble of analyses where a trajectory is started from each perturbed analysis. This method, called the Ensemble analysis method (EA), is compared to the Initial spread method (IS), where the trajectory receptor point is perturbed in the horizontal and vertical direction to create a set of trajectories used to estimate the trajectory uncertainty. The deviation growth is examined for one summer and one winter month and for 15 different geographical locations. We find up to a 40% increase in trajectory deviation in the mid-latitudes using the EA method. A simple model for trajectory deviation growth speed is set up and validated. It is shown that the EA method result in a faster error growth compared to the IS method. In addition, two case studies are examined to qualitatively illustrate how the flow dependent analysis uncertainty can impact the trajectory calculations. We find a more irregular behavior for the EA trajectories compared to the IS trajectories and a significantly increased uncertainty in the trajectory origin. We conclude that by perturbing the analysis in agreement with the analysis uncertainties the error in backward trajectory calculations can be more consistently estimated.

Place, publisher, year, edition, pages
2009. Vol. 9, no 22, 8857-8867 p.
National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences and Oceanography
Identifiers
URN: urn:nbn:se:su:diva-31855DOI: 10.5194/acp-9-8857-2009ISI: 000272232500016OAI: oai:DiVA.org:su-31855DiVA: diva2:278797
Available from: 2009-11-30 Created: 2009-11-30 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Aerosol-cloud interaction from an observational and modeling perspective
Open this publication in new window or tab >>Aerosol-cloud interaction from an observational and modeling perspective
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Clouds may respond strongly to changes in the atmospheric aerosol population, and the response of clouds to an increased global aerosol burden could to some extent mask the warming caused by enhanced greenhouse gas concentrations. However, estimates of the impact of aerosols on cloud properties are associated with large uncertainties, both because of difficulties representing the aerosol-cloud interaction within models, and because of problems of unequivocally isolating the effect of aerosols on cloud properties in observational data. This thesis focuses in part on underlying meteorological factors that significantly correlate with both aerosol and cloud properties, and on how sensitive clouds are to small variations in meteorological conditions. It was found that meteorological covariations must be taken into account when estimating the strength of the relationship between aerosols and cloud properties. By studying the response of shallow convective clouds to perturbations in meteorological conditions and aerosol concentration, it was further concluded that variations in meteorological conditions can enhance or mask the relationship between aerosols and cloud properties, making it difficult to isolate the aerosol signature from small meteorological differences. Additionally, the impact of deep convective clouds on the redistribution of aerosols within a cloud life cycle is examined. It was found that mid-tropospheric aerosols can have a substantial source in evaporating cloud droplets within deep convection. Lastly, this thesis focuses on the implications of meteorological analysis uncertainties, in part related to the difficulties of constraining meteorological variability in observational data of clouds and aerosols, but mainly the impact of analysis errors on atmospheric trajectory calculations. A method is presented to consistently estimate the uncertainty in trajectory calculations. It was concluded that the spatial and temporal trajectory error can be substantially underestimated if the analysis error is not taken into account.

Place, publisher, year, edition, pages
Stockholm: Department of Meteorology, Stockholm University, 2011. 49 p.
National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences and Oceanography
Identifiers
urn:nbn:se:su:diva-62322 (URN)978-91-7447-355-1 (ISBN)
Public defence
2011-11-25, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript. Available from: 2011-11-02 Created: 2011-09-14 Last updated: 2011-10-21Bibliographically approved

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