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O rganizers: Tom Hamill (NOAA, WGNE) Tim Palmer (Oxford U, ECMWF) Istvan Szunyogh (THORPEX/PDP)

WGNE-THORPEX/PDP-ECMWF workshop on Physically Based Stochastic Parameterisation June 11-14, ECMWF, Reading, England. O rganizers: Tom Hamill (NOAA, WGNE) Tim Palmer (Oxford U, ECMWF) Istvan Szunyogh (THORPEX/PDP). Reminder: we discussed at WGNE-25 whether to co-sponsor this….

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O rganizers: Tom Hamill (NOAA, WGNE) Tim Palmer (Oxford U, ECMWF) Istvan Szunyogh (THORPEX/PDP)

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  1. WGNE-THORPEX/PDP-ECMWFworkshop onPhysically Based Stochastic ParameterisationJune 11-14, ECMWF, Reading, England Organizers: Tom Hamill (NOAA, WGNE) Tim Palmer (Oxford U, ECMWF) Istvan Szunyogh (THORPEX/PDP)

  2. Reminder: we discussed at WGNE-25 whether to co-sponsor this…

  3. back to stochastic parameterisation workshop…

  4. Why a workshop? • My reason (there are others) : deterministic forecasts and (ensembles) contaminated by bias, (lack of spread). • One cause may be inappropriate deterministic assumptions built into parameterisations (next slide). • Stochastic parameterisation a hot topic, but progress could be faster. • A workshop and its recommendations could help • Share recent knowledge. • Educate grad students, post-docs. • Through recommendations, provide official WMO, THORPEX, WGNE blessing to proposal writers as to importance of subject matter. • Spur development of common data sets (e.g., CRM simulations) that could be used for training and validation. • Determine what sort of diagnostic techniques should become standardized.

  5. Plant & Craig Cloud-resolving model run to statistical equilibrium. Range of convective mass flux responses shown here and how they vary as a function of the size of the grid box. Lesson: as we move to finer resolutions, the deterministic assumptions built into the parameterizations becomes increasingly inappropriate.

  6. Why on “physically based”stochastic parameterisation? • There are techniques in operations that act to increase spread in ensembles, but they cannot be defended from first principles. • In iterative development of NWP systems, it’s important to get the right answer for the right reason, else future testing is complicated by building upon past ad-hoc work.

  7. Where WGNE can help • Are there missing topics in proposed workshop (next slides)? Missing key questions? • Help identify who to invite, both as speakers and as participants. • I have a preference for a moderately sized workshop, say 50 people, with many post-docs and grad students. They are the ones who will probably be doing the work and can benefit the most. THORPEX/PDP disagreed somewhat, wanted more emphasis on active researchers. • I want to identify speakers that are good communicators as much as more than those who have extensive research pedigree. • Feel free to e-mail me your thoughts, tom.hamill@noaa.gov

  8. Proposed organization of workshop,continued (3) Current developments in parameterising model uncertainty.  [this session would be a longer one, intending to give the major players doing research a chance to describe their recent work].   Examples of major subject areas include: (a) Stochastically perturbed physical tendencies. (b) Stochastic backscatter. (c) Stochastic convective parameterisation.(d) Perturbed-parameter approaches.(e) Multi-parameterisation approaches.(f) Integrating stochastic differential equations.

  9. Proposed organization of workshop, continued (4) Issues in stochastic parameterisations. (a) Balance and time/space covariances for stochastic noise, i.e., inappropriate column assumption - how to incorporate non-locality(b) Relative benefits of comprehensive approaches (stochastically perturbed physical tendencies) vs. process-by-process approaches (c) Methods of diagnosis and verification for stochastic techniques - how do we know if we're doing the right thing (d) Use of ensemble Kalman filters and other data assimilation techniques as a diagnostic tool

  10. Proposed organization of workshop (5) Breakout groups. Questions for breakout groups might include: (a) What data sets do we need to collate or build for training and validation, such as CRMs, prior relevant field experiment data...? (b) What underlying principles should be followed in order for a stochastic method to be considered “physically based?” (c) Are there general diagnostic techniques that can be applied across the suite of parameterisations? (d) What recommendations should be made to funding agencies and NWP centres regarding this topic? (6) Plenary.

  11. Workshop organizationcomments • Please e-mail me, tom.hamill@noaa.gov

  12. Proposed organization of workshop • Overview. Also: statements of interest from WGNE, THORPEX, other organizations about their scientific interest and role. Review of ensemble prediction, existing efforts to deal with model uncertainty via multi-model, multi-parameterisation ensembles, statistical post-processing. • Review of parameterisations(for each topic below, the invited speaker would describe the physical process, describe common parameterisation approaches, and describe where there are deterministic assumptions built into the parameterisation, what scales these deterministic assumptions are valid for).  This session is background.    (a) Land-surface     (b) Boundary layer     (c) Deep convection     (d) Stratocumulus     (d) Radiation     (e) Microphysics     (f) Turbulence, mountain drag     [etc.]

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