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Protrait Alex Vermeulen

Alex Vermeulen

Chef

Protrait Alex Vermeulen

Impact of optimized mixing heights on simulated regional atmospheric transport of CO2

Författare

  • R. Kretschmer
  • C. Gerbig
  • Ute Karstens
  • Gionata Biavati
  • Alex Vermeulen
  • F. Vogel
  • S. Hammer
  • K. U. Totsche

Summary, in English

The mixing height (MH) is a crucial parameter in commonly used transport models that proportionally affects air concentrations of trace gases with sources/sinks near the ground and on diurnal scales. Past synthetic data experiments indicated the possibility to improve tracer transport by minimizing errors of simulated MHs. In this paper we evaluate a method to constrain the Lagrangian particle dispersion model STILT (Stochastic Time-Inverted Lagrangian Transport) with MH diagnosed from radiosonde profiles using a bulk Richardson method. The same method was used to obtain hourly MHs for the period September/October 2009 from the Weather Research and Forecasting (WRF) model, which covers the European continent at 10 km horizontal resolution. Kriging with external drift (KED) was applied to estimate optimized MHs from observed and modelled MHs, which were used as input for STILT to assess the impact on CO2 transport. Special care has been taken to account for uncertainty in MH retrieval in this estimation process. MHs and CO2 concentrations were compared to vertical profiles from aircraft in situ data. We put an emphasis on testing the consistency of estimated MHs to observed vertical mixing of CO2. Modelled CO2 was also compared with continuous measurements made at Cabauw and Heidelberg stations. WRF MHs were significantly biased by similar to 10-20% during day and similar to 40-60% during night. Optimized MHs reduced this bias to similar to 5% with additional slight improvements in random errors. The KED MHs were generally more consistent with observed CO2 mixing. The use of optimized MHs had in general a favourable impact on CO2 transport, with bias reductions of 5-45% (day) and 60-90% (night). This indicates that a large part of the found CO2 model-data mismatch was indeed due to MH errors. Other causes for CO2 mismatch are discussed. Applicability of our method is discussed in the context of CO2 inversions at regional scales.

Publiceringsår

2014-07-16

Språk

Engelska

Sidor

7149-7172

Publikation/Tidskrift/Serie

Atmospheric Chemistry and Physics

Volym

14

Issue

14

Dokumenttyp

Artikel i tidskrift

Förlag

Copernicus GmbH

Ämne

  • Physical Geography

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1680-7324