1 / 14

Evaluation of a new trigger function for shallow cumulus convection

Evaluation of a new trigger function for shallow cumulus convection. Marijn de Haij A. Pier Siebesma Henk Klein Baltink Fred Bosveld KNMI, De Bilt The Netherlands. cloud base. Mean profiles T, q. Surface fluxes. Courtesy Manfred Wendisch, IfT. The problem.

cameo
Download Presentation

Evaluation of a new trigger function for shallow cumulus convection

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Evaluation of a new trigger function for shallow cumulus convection Marijn de Haij A. Pier Siebesma Henk Klein Baltink Fred Bosveld KNMI, De Bilt The Netherlands

  2. cloud base Mean profiles T, q Surface fluxes Courtesy Manfred Wendisch, IfT The problem • Estimate cloud convective properties on the basis of observations in sub-cloud layer • Properties: • Presence of BL clouds • Cloud base(/top) height • In-cloud properties • (LWC, vertical velocity)

  3. Used data • BBC2 near Cabauw, 3-24 May 2003 - mast: surface fluxes and profiles T, q - IPT v1: profiles of T, q and LWC validation - CT75K lidar: cloud base validation - Merlin/Partenavia/MAPSY: cloud validation • Cabauw, September 2003 - sonic anemometers: thermal structure characteristics

  4. Clouds arise from thermals that form in the surface layer. Employ updraft equations also in the sub-cloud layer! New formulation(Siebesma and Teixeira 2000, AMS proceedings)C. Jakob and A.P. Siebesma, Month. Weath. Rev. , 131 ,2765-2778 , 2003 • At present: undiluted parcel ascent, cloud base found for saturated parcels with ΔTv>-0.5K (ECMWF)

  5. Mixing CLTP Vertical velocity LZB Release excesses LFC LCL LNB parcel 1D Single Parcel Ascent ModelAn offline entraining single parcel model Mean • Reference run REF • zr = 10m, cε = 0.6, ε = cε(1/z) • b = 1.0, c1 = 0.71 & 2.0, c2 = 1.43 & 1/3 • dt = 600 s, dz = 10m, H = 4000m

  6. Initialization profiles15 May Combination of T,q profiles from Cabauw mast and IPT (Löhnert et al., 2004)

  7. Typical result15 May Cloud boundaries: model vs. observations

  8. Results REF run15 May Updraft θv excess, vertical velocity and LWC

  9. Examples of BBC2 validationMAPSY and Partenavia check on LWC and w, 15 May Observations only cover part of modeled vertical profiles 9UTC 11UTC 9UTC

  10. General results (1)Sensitivity to dilution and to entrainment factor, 11,15 and 21 May REF run tends to pull modeled cloud base towards observed cloud base

  11. General results (2)Sensitivity to release height, 21 May Dilution causes independency for parcel release height

  12. Problems on fitting mast-IPT Mast observations fixed, IPT translated IPT mast 11 May 10:20UTC

  13. Characterizing thermals Wavelet analysis on time series • Excess factor b for θl and qt (range 1.0 – 2.5) • Mean thermal anomalies as f(t,z) • Contribution of thermals to fluxes Parameters to be derived

  14. To be included • Testing derived excess factors • Sensitivity to other entrainment parameterizations • More BBC2 validation events • Initialization with IPT v2.0 • (Testing formulation in SCM)

More Related