On the Forward Modeling of Radar Doppler Spectrum Width From LES: Implications for Model Evaluation

Y. S. Chen, J. Verlinde, E. E. Clothiaux, A. S. Ackerman, A. M. Fridlind, M. Chamecki, P. Kollias, M. P. Kirkpatrick, B. C. Chen, G. Yu, A. Avramov

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Abstract

Large-eddy simulations of an observed single-layer Arctic mixed-phase cloud are analyzed to study the value of forward modeling of profiling millimeter wave cloud radar Doppler spectral width for model evaluation. Individual broadening terms and their uncertainties are quantified for the observed spectral width and compared to modeled broadening terms. Modeled turbulent broadening is narrower than the observed values when the turbulent kinetic energy dissipation rate from the subgrid scale model is used in the forward model. The total dissipation rates, estimated with the subgrid scale dissipation rates and the numerical dissipation rates, agree much better with both the retrieved dissipation rates and those inferred from the power spectra of the simulated vertical air velocity. The comparison of the microphysical broadening provides another evaluative measure of the ice properties in the simulation. To accurately retrieve dissipation rates as well as each broadening term from the observations, we suggest a few modifications to previously presented techniques. First, we show that the inertial subrange spectrum filtered with the radar sampling volume is a better underlying model than the unfiltered −5/3 law for the retrieval of the dissipation rate from the power spectra of the mean Doppler velocity. Second, we demonstrate that it is important to filter out turbulence and remove the layer-mean reflectivity-weighted mean fall speed from the observed mean Doppler velocity to avoid overestimation of shear broadening. Finally, we provide a method to quantify the uncertainty in the retrieved dissipation rates, which eventually propagates to the uncertainty in the microphysical broadening.

Original languageEnglish (US)
Pages (from-to)7444-7461
Number of pages18
JournalJournal of Geophysical Research: Atmospheres
Volume123
Issue number14
DOIs
StatePublished - Jul 27 2018

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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    Chen, Y. S., Verlinde, J., Clothiaux, E. E., Ackerman, A. S., Fridlind, A. M., Chamecki, M., Kollias, P., Kirkpatrick, M. P., Chen, B. C., Yu, G., & Avramov, A. (2018). On the Forward Modeling of Radar Doppler Spectrum Width From LES: Implications for Model Evaluation. Journal of Geophysical Research: Atmospheres, 123(14), 7444-7461. https://doi.org/10.1029/2017JD028104