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Parameterization of Convective Transport in a Lagrangian Particle Dispersion Model and Its Evaluation

Forster, Caroline and Stohl, Andreas and Seibert, Petra (2007) Parameterization of Convective Transport in a Lagrangian Particle Dispersion Model and Its Evaluation. Journal of Applied Meteorology and Climatology, 46, pp. 403-422. DOI: 10.1175/JAM2470.1.

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Abstract

This paper presents the revision and evaluation of the interface between the convective parameterization by Emanuel and Živkovic´-Rothman and the Lagrangian particle dispersion model “FLEXPART” based on meteorological data from the European Centre for Medium-Range Weather Forecasts (ECMWF). The convection scheme relies on the ECMWF grid-scale temperature and humidity and provides a matrix necessary for the vertical convective particle displacement. The benefits of the revised interface relative to its previous version are presented. It is shown that, apart from minor fluctuations caused by the stochastic convective redistribution of the particles, the well-mixed criterion is fulfilled in simulations that include convection. Although for technical reasons the calculation of the displacement matrix differs somewhat between the forward and the backward simulations in time, the mean relative difference between the convective mass fluxes in forward and backward simulations is below 3% and can therefore be tolerated. A comparison of the convective mass fluxes and precipitation rates with those archived in the 40-yr ECMWF Reanalysis (ERA-40) data reveals that the convection scheme in FLEXPART produces upward mass fluxes and precipitation rates that are generally smaller by about 25% than those from ERA-40. This result is interpreted as positive, because precipitation is known to be overestimated by the ECMWF model. Tracer transport simulations with and without convection are compared with surface and aircraft measurements from two tracer experiments and to <sup>222</sup>Rn measurements from two aircraft campaigns. At the surface no substantial differences between the model runs with and without convection are found, but at higher altitudes the model runs with convection produced better agreement with the measurements in most of the cases and indifferent results in the others. However, for the tracer experiments only few measurements at higher altitudes are available, and for the aircraft campaigns the <sup>222</sup>Rn emissions are highly uncertain. Other datasets better suitable for the validation of convective transport in models are not available. Thus, there is a clear need for reliable datasets suitable to validate vertical transport in models.

Document Type:Article
Title:Parameterization of Convective Transport in a Lagrangian Particle Dispersion Model and Its Evaluation
Authors:
AuthorsInstitution or Email of Authors
Forster, CarolineUNSPECIFIED
Stohl, AndreasNILU, Kjeller, N
Seibert, PetraUniv. of Natural Resources and Applied Life Sciences (BOKU), Vienna, A
Date:2007
Journal or Publication Title:Journal of Applied Meteorology and Climatology
Volume:46
DOI:10.1175/JAM2470.1
Page Range:pp. 403-422
Status:Published
Keywords:dispersion modelling, convection, convective parameterization, air pollution transport
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:L VU - Air Traffic and Environment (old)
DLR - Research area:Aeronautics
DLR - Program:L VU - Air Traffic and Environment
DLR - Research theme (Project):L - Air Traffic and Weather (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Cloud Physics and Traffic Meteorology
Deposited By: Jana Freund
Deposited On:14 Jun 2007
Last Modified:12 Dec 2013 20:24

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