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Kain-Fritsch convection scheme: an update

Kain-Fritsch convection scheme: an update. Marco Arpagaus MeteoS wiss. Outline. Good News and Bad News Some test-case results Improvements needed More sensitivity tests More output Conclusion and Outlook. Good News and Bad News.

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Kain-Fritsch convection scheme: an update

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  1. Kain-Fritsch convection scheme:an update Marco Arpagaus MeteoSwiss

  2. Outline • Good News and Bad News • Some test-case results • Improvements needed • More sensitivity tests • More output • Conclusion and Outlook Marco.Arpagaus@MeteoSwiss.ch COSMO General Meeting, 24-26 Sep 2003, Langen

  3. Good News and Bad News • Cleaned and reasonably well tested version available with LM version 3.6. • However, still a lot to be tested and improved (see below). • Poor performance on vector machines, but ok for MPPs; can not be optimized without substantial recoding. • Alternative implementations of Tiedtke and Kain-Fritsch schemes available (from Peter Bechtold, ECMWF); will be added to the LM as alternative CPSs as soon as possible. • Kain-Fritsch is already being experimentally used for the COSMO LEPS. Marco.Arpagaus@MeteoSwiss.ch COSMO General Meeting, 24-26 Sep 2003, Langen

  4. Some test-case results: 12.06.2003 00UTC • Synoptic situation: High-pressure system over large parts of central Europe; convection over Switzerland in second half of the day. • Poor forecast (complaints by forecasters) by aLMo: Can the Kain-Fritsch scheme provide a better forecast? Marco.Arpagaus@MeteoSwiss.ch COSMO General Meeting, 24-26 Sep 2003, Langen

  5. Some test-case results: 12.06.2003 00UTC Kain-Fritsch (nudging, GME) Tiedtke (nudging, GME) 09-12 UTC Kain-Fritsch (nudging, IFS) Marco.Arpagaus@MeteoSwiss.ch COSMO General Meeting, 24-26 Sep 2003, Langen

  6. Some test-case results: 12.06.2003 00UTC Kain-Fritsch (nudging, GME) Tiedtke (nudging, GME) 12-15 UTC Kain-Fritsch (nudging, IFS) Marco.Arpagaus@MeteoSwiss.ch COSMO General Meeting, 24-26 Sep 2003, Langen

  7. Some test-case results: 12.06.2003 00UTC Kain-Fritsch (nudging, GME) Tiedtke (nudging, GME) 15-18 UTC Kain-Fritsch (nudging, IFS) Marco.Arpagaus@MeteoSwiss.ch COSMO General Meeting, 24-26 Sep 2003, Langen

  8. Some test-case results: 12.06.2003 00UTC Kain-Fritsch (nudging, GME) Tiedtke (nudging, GME) 18-21 UTC Kain-Fritsch (nudging, IFS) Marco.Arpagaus@MeteoSwiss.ch COSMO General Meeting, 24-26 Sep 2003, Langen

  9. Some test-case results: 12.06.2003 00UTC Kain-Fritsch (nudging, GME) Tiedtke (nudging, GME) 21-24 UTC Kain-Fritsch (nudging, IFS) Marco.Arpagaus@MeteoSwiss.ch COSMO General Meeting, 24-26 Sep 2003, Langen

  10. Some test-case results: 24.07.2003 00UTC • Synoptic situation: Retreat of a high-pressure ridge over southern Europe and passage of an upper-level trough; short-wave disturbance with associated cold front crosses Germany in the evening; pre-frontal convection in the afternoon. • Poor forecast (complaints by forecasters) by LM at DWD: Can the Kain-Fritsch scheme provide a better forecast? Marco.Arpagaus@MeteoSwiss.ch COSMO General Meeting, 24-26 Sep 2003, Langen

  11. Some test-case results: 24.07.2003 00UTC Kain-Fritsch (nudging, GME) Tiedtke (nudging, GME) 12-18 UTC Kain-Fritsch (interpolation, GME) Marco.Arpagaus@MeteoSwiss.ch COSMO General Meeting, 24-26 Sep 2003, Langen

  12. Improvements needed • Stripes of low precipitation amounts in the grid-scale precipitation output fields: insufficient removal of vertical instabilities? Related question: what are reasonable vertical velocities at the grid-scale? • Did you observe any obvious shortcomings of the scheme? Marco.Arpagaus@MeteoSwiss.ch COSMO General Meeting, 24-26 Sep 2003, Langen

  13. More sensitivity tests • Feedbacks provided by the Kain-Fritsch scheme • temperature and water vapour only (same as Tiedtke scheme) • temperature and all hydrometeors the host model ‘knows’ • Trigger • amount of temperature perturbation at the LCL • dependence of temperature perturbation on vertical velocity and/or relative humidity • sensitivity to averaging (of vertical velocity, forcing fields) • Closure • time scale • Interplay of deep, shallow, and midlevel convection • Dependence of scheme on calling frequency Marco.Arpagaus@MeteoSwiss.ch COSMO General Meeting, 24-26 Sep 2003, Langen

  14. More output • cloud cover (for radiation scheme!) --- do it analogous to Tiedtke scheme? • cloud base & cloud top • CAPE, CIN • massflux at cloud base • … Marco.Arpagaus@MeteoSwiss.ch COSMO General Meeting, 24-26 Sep 2003, Langen

  15. Conclusion and Outlook • Code available for extensive testing; experimental usage encouraged (feedback, please!). • Missing output fields will be added within the next few weeks. • Detailed case and sensitivity studies pending; anyone willing to do parallel runs (on MPPs …)? • Implementation of alternative implementations of Tiedtke (IFS) and Kain-Fritsch (Meso-NH, Bechtold) schemes as soon as possible. Marco.Arpagaus@MeteoSwiss.ch COSMO General Meeting, 24-26 Sep 2003, Langen

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