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Subgrid-scale Microphysics in UCLA-LaRC SCM with IP-HOC

Subgrid-scale Microphysics in UCLA-LaRC SCM with IP-HOC. Anning Cheng 1 and Kuan-Man Xu 2 AS&M, Inc. Science Directorate, NASA Langley Research Center. Outline. Intermediately prognostic (IP) higher-order closure (HOC) model

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Subgrid-scale Microphysics in UCLA-LaRC SCM with IP-HOC

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  1. Subgrid-scale Microphysics in UCLA-LaRC SCM with IP-HOC Anning Cheng1 and Kuan-Man Xu 2 AS&M, Inc. Science Directorate, NASA Langley Research Center

  2. Outline • Intermediately prognostic (IP) higher-order closure (HOC) model • Results form UCLA-LaRC SCM, 3D-SAM LES and 2D-SAM LES with IP-HOC • Subgrid-scale (SGS) microphysics scheme in UCLA-LaRC SCM • Effects of the SGS microphysics scheme

  3. 2D-SAM LES (with IP-HOC) Configuration • Domain size is 250 km • Horizontal grid size is 200 m • The 2D LES is aligned in either x direction (Exp. U) or y direction (Exp. V) • The rest of configuration is the same as in the 3D LES

  4. Subgrid-scale Autoconversion • The original Kessler’s autoconversion rate is simply proportional to the grid-mean cloud water mixing ratio, subject to a threshold value • An integration of the Kessler’s formula multiplied by the subgrid-scale Double-Gaussian pdf found that subgrid-scale autoconversion is a function of mean, variance, and skewness of liquid water potential temperature and total water mixing ratio • What is the effect of including the new subgrid-scale autoconversion formulation?

  5. Rain Water Collection Rate and Skewness of W

  6. Summary and Discussion • UCLA-LaRC SCM produces reasonable results for the RICO case although improvement is still needed • Subgrid-scale microphysics is essential for the IP-HOC model to produce precipitation • The cloud amount and cloud top height decreased drastically when subgrid-scale autoconversion rate was used • Compared to 3D LES, the autoconversion rate is too high, but the collection rate is reasonable in the SCM simulation athough their formula are very simple

  7. Thank You!

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