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Ute Karstens

Researcher

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Toward assimilation of observation-derived mixing heights to improve atmospheric tracer transport models

Author

  • Roberto Kretschmer
  • Frank Thomas Koch
  • Dietrich G. Feist
  • Gionata Biavati
  • Ute Karstens
  • Christoph Gerbig

Summary, in English

Common transport models use the mixing height (MH) to determine turbulent coefficients and to obtain tracer concentrations in the planetary boundary layer (PBL). We conducted a pseudo data experiment to elucidate the impact of assimilating MHs to improve CO2 transport within the Stochastic Time-Inverted Lagrangian Transport model (STILT). Transport of CO2 was simulated for August 2006 with a receptor located at Bialystok, Poland. STILT was driven by meteorology obtained from the Weather Research and Forecasting (WRF) model, using the Yonsei University (YSU) and Mellor-Yamada-Janjic (MYJ) PBL parameterizations, which differ substantially in the produced MHs. To quantify model-data mismatch in CO2 to errors in vertical mixing, we defined the WRF-YSU simulation as known truth. Pseudo MH observations were sampled from WRF-YSU at locations of real radiosonde stations. These point observations were interpolated in space-time to the entire WRF domain using kriging with an external drift, which combines observed and modeled MHs to create a "best guess" MH field. We prescribed MHs in STILT driven by WRF-MYJ winds with the best guess to study the impact on CO 2 concentrations. Differences in CO2 between the STILT simulations were on the order of ̃0-1 and ̃1-10 ppm on average (i.e., bias), with standard deviations of ̃1-3 and ̃4-14 ppm (random error) during day (12 UTC) and nighttime (0 UTC), respectively. These were reduced when using STILT with the best guess (̃50%-80% of the bias, ̃10%-20% of the random error). Simulated CO2 concentrations and MHs were also compared to measurements made at the Bialystok tall tower.

Publishing year

2012

Language

English

Pages

185-205

Publication/Series

Geophysical Monograph Series

Volume

200

Document type

Book chapter

Publisher

American Geophysical Union (AGU)

Topic

  • Earth and Related Environmental Sciences

Status

Published