Separation

1. Along the aim of COSMO-SP to consider missing interactions: • Mass fraction and number concentration of • cloud constituents, • precipitation and • passive tracers (aerosols) • Optical properties: • optical thickness, • single scattering albedo, • asymmetry factor and • delta-transmission function Increased set of diagnostic or prognostic variables: modified by SGS-processes feed-back with SGS-processes PP T2(RC)2 Radiation transport Cloud-microphysics Local parameterizations: Parameterizations of source terms integrated in GS parameterizations: Parameterizations of SGS processes interaction STIC Turbulence Separation Circulations PT ConSAT Surface and Soil-processes

2. Testing & Tuning of Revised Cloud Radiation Coupling T2(RC)2PP: Status & Highlights since CGM in Israel Project leader: Harel Muskatel (IMS) Pavel Khain (IMS), Alon Shtivelman (IMS), Oliver Fuhrer (MCH),Xavier Lapillonne (MCH), Gdaly Rivin (RHM), Natalia Chubarova (RHM), Marina Shatunova (RHM), Alexey Poliukov (RHM), Alexander Krisanov (RHM) Ulrich Blahak (DWD), Daniel Rieger (DWD), Matthias Raschendorfer (DWD), Simon Gruber(KIT)

3. The highlights/news are: • Phase II accepted! • Intensive running on ECMWF computers (ongoing): • tuning the 30 new radiation scheme parameters (CALMO). • Fist set of runs is finished needs now to be analyzed. • Implementation of Monte-Carlo spectral integration into COSMO-radiation: • finished and sanity-tested • New optical properties for ice- and water-droplets implemented in ICON-RRTM: • same as what we did in COSMO. • The parametrizations were calculated by Uli. B and Harel M. • Implementation done by Simon Gruber • ICON-ART aerosols: • Implemented in COSMO radiation • Adaptation of INT2LM code for interpolation of ICON-ART fields

4. Implementation of CAMS aerosols into COSMO radiation scheme: • Optical properties adapted from ECMWF to COSMO 8-band radiation • INT2LM and COSMO prepared to use mixing ratios of 5 different aerosol-species taken from MACC • Coding, test-runs and documentation ready • Comparisons with different aerosol-data concluded (showed at CGM) • Inter-comparison with accurate measurements in cloudy conditions • -> phase 2 • Implementation of CAMS prognostic aerosols into COSMO microphysics: • Introducing the Segal&Khain-method to define cloud number concentration • -> to be continued in Phase II • Implementation into ice-nucleation scheme • -> starting in Phase II • Case studies, Inter-comparison and documentation • -> Phase II

5. Further tasks for Phase II: • Standard-Verification with new cloud-radiation coupling including different aerosol input • Updating official COSMO version with the recent T2(RC2)-development • New combined scheme for SGS clouds • Investigation, whether components of the shallow convection parameterization by Boeing can be used for cloud-cover parameterization • New development of shallow convection, if necessary • Implementation of a proper combination with turbulent saturation-adjustment (“statistical” cloud scheme) • Verification of revised combined scheme for SGC clouds against ground-base and satellite data

6. General and common WG3-Task “Consolidation of the Surface-to-Atmosphere (ConSAT): according to a dynamically adapted list of actions being the base of past and (maybe) future PTs Current topic: Reformulation of surface-processes with respect to roughness-effects and numerical stability in TERRA and TURBTRAN Current contributors: Matthias Raschendorfer (DWD) Günther Zängl (DWD), (Jan-Peter S., Jürgen H.) COSMO Matthias Raschendorfer Offenbach 2018

7. Main lessen from previous ConSAT tasks: • Background-diffusion (BD), introduced, e.g., by minimal diff.-coeff., is a substitute of missing STIC terms (acting due to non-turbulent heterogeneity). • If BD is applied in the BL even above a homogeneous surface, it partly destroys the stability reduction of SAT-velocity. • Modifications in the description of the turbulent Prandtl-layer can hardly correct the main sources of current model-errors of the diurnal cycle of near surface variables! • The process description of surface processes provides by far the largest potential for improvement!! COSMO Matthias Raschendorfer Offenbach 2018

8. Case study: 23.06.2016 COSMO-DE with lateral boundaries from ICON-EU • only for rather smooth surfaces; applied filter • almost saturated soil due to long standing rain period before • almost no clouds due to high pressure situation; + applied filter TD_2m T_2m still much too moist in the afternoon still much too cold during day-time nocturnal warm bias removed but perhaps a new nocturnal dry bias direct analysis of T_2m and TD_2m operational configuration revised TURBDIFF imported from ICON Geneve 2017 Matthias Raschendorfer

9. Case study: 23.06.2016 COSMO-DE with lateral boundaries from ICON-EU • only for rather smooth surfaces; applied filter • almost saturated soil due to long standing rain period before • almost no clouds due to high pressure situation; + applied filter TD_2m T_2m removed cold bias in the afternoon! almost perfect double wave! amplitude slightly overestimated still some problems during heating of the cover (stable stratification within the roughness layer) revised TURBDIFF imported from ICON + new decoupled surface cover: revised TURBDIFF imported from ICON direct analysis of T_2m and TD_2m Geneve 2017 Matthias Raschendorfer

10. Another lessen from previous ConSAT tasks: • Direct process-parameterization can be substituted by empirical (statistical) hyper-parameterizations, trying to derive missing relations by diagnostics and sensitivity-experiments (trial&error). • What Günther has rather successfully done in ICON, e.g., related to • Background-diffusion: to be substituted by STIC-terms • Roughness-effects for the snow-cover: to be substituted in the framework of a full R-layer description COSMO Matthias Raschendorfer Offenbach 2018

11. Illustration of a realistic surface concept: : indicator of the lowermost full atm. level may carry liquid or frozen interception water : area and indicator of total surface : area and indicator of the cover-surface (surface of all R-elements) R-layer : indicator of the snow-cover surface snow-cover : area and indicator of the bare-soil surface : indicator of the uppermost full soil level : indicator of the snow-cover surface • Critical properties: : indicator of all snow-free surfaces • R-elements are substantial, semi-transparent and thermally loosely coupled to B. • Their Temperature T_c may be different from T_b, which is distinctive from T_b1. • They may contain liquid and frozen interception water. • They can shade B from radiation. • Snow-free parts of S are mainly parts of C. • R-elements vanish within an increasing snow-cover. • Distribution of snow cover alters aerodynamic R-length (z0) and short-wave albedo. • Coexistence of liquid water and ice possible. • Smooth transition due to variance of T_sf or T_sn. Matthias Raschendorfer Offenbach 2018

12. Illustration of the current idealized surface concept: increasing with snow-water level : indicator of the lowermost full atm. level only liquid interception water : area and indicator of total surface : area and indicator of the cover-surface (surface of all R-elements) R-layer : indicator of the snow-cover surface : area and indicator of the bare-soil surface : indicator of the uppermost full soil level : indicator of the snow-cover surface • Current implementation: : indicator of all snow-free surfaces • Total land-use surface is a topographic enlargement of the horiz. ground by the factor SAI • thermally coupled with the soil like the bare-soil surface • with fractions of distinctive sf-evaporation: B, (wetted , transpirating or sealed) C • Only one sf surface temperature T_sf=T_c=T_b=T_b1. • R-elements carry only liquid interception water. • Mass (heat-capacity) of R-elements is neglected. • R-elements do not cover (shade) the bare-soil surface B, as they are rather a part of it. • R-layer is treated like a pure additional transport-resistance for sensible and latent heat. • Snow and rime are treated together and are concentrated in a single cover. • Snow follows surface-structure (no additional effect on z0). Matthias Raschendorfer Offenbach 2018

13. Current stat in operational ICON-TERRA: • “dirty” fixes related to snow at a rough surface implemented by Günther Z.: • Melting snow: f_sf represents mainly the surface C of sf R-elements: • Snow is artificially “pushed together”. • f_sn<1, although snow may totally cover the soil-surface B. • Mean surface temperature T_s may become > 0°C, what was missing before! • But: Artificial bare-soil evaporation with T_sf>0°C at the fraction f_sn*B needs to be restricted by potential snow-evaporation! • Dynamic sn and sf sub-tiles prevent from a too fast melting of snow. • Frosty snow: sf R-elements can’t be treated similarly: • T_sf would become too warm as C is thermally not yet decoupled from B. • Calculating a reduced albedo of “dirty” snow dependent on snow-age and z0. • f_snmay be as large as 1, although the surface C is sf. • “Dirty” snow (polluted by sf R-elements) gets only a bit warmer than pure snow. • But: Snow-evaporation is too strong and needs to be artificially restricted! • Rime: No longer treated as a contribution to snow: • Frozen R-elements can evaporate potentially even without a snow-cover • But:Enthalpy by freezing or melting of interception water not yet considered and interception of fresh snow not yet included! Offenbach 2018 Matthias Raschendorfer

14. Plant-evaporation: reduction during late afternoon: • Introduction of a evaporation hysteresis due to restricted water supply through the stems • New implementation needs to reduce these fixesas far as possiblebutnot more than still required!! • Our beleave: • Most of these indirect “tricks” can be substituted via the full R-layer implementation!! COSMO Matthias Raschendorfer Offenbach 2018

15. Main aims with respect to an improved process-description: • Better representation of effects caused by surface roughness also in combination with snow and interception-water • Semi-transparent and loosely coupled roughness cover: • Shading of the soil-surface B by the R-cover C (e.g. plants). • Different surface temperatures for pure soil (T_b) and R-elements (T_c). • Better adapted soil-evaporation and plant-transpiration. • Stronger thermal decoupling of C from B. • Improved diurnal cycle of near-surface variables. • Realistic treatment of snow and rime at a rough surface: • Allowing a sf roughness cover C above the snow-cover at B. • Allowing interception also of snow- or rime at C. • Modification of short-wave albedo dependent on snow-distribution. • Modification of roughness-structure by snow-cover. • Realization of a mean T_s > 0°C for a totally snow-covered soil • Revision of dynamic sn and sf sub-tiles. • Proper consideration of conversion-enthalpy of freezing or thawing of interception water. Matthias Raschendorfer Offenbach 2018

16. Main aims with respect to numerical represenatation: • Improvement of numerical stability • Removal of T_s-oscillation and artificial flux-limiter: • Implicit treatment of T_sf and T_sn in near-surface heat-budgets. • Linear combination of heat-budgets of soil-layers, the roughness cover and the snow-cover. • Considering the implicit dependency of transfer-velocity for heat on T_s. • Implicit and positive-definite formulation of water-levels with respect to evaporation (of snow and interception water). • Removal of various artificial limitations. • Avoiding of artificial numerical sources due to implicit treatment. • Implicit formulation of freezing and melting of snow-water and soil-water. • Towards a smooth transition between water-phases. Offenbach 2018 Matthias Raschendorfer

17. Current state of new implementation: • Revised TERRA and TURBDIFF in ICON-branch • Including all measures (green aims) with respect to implicit treatment of T_s • Contains also a separate equation for implicit T_sf • Various adaptions related to: • Calculation of snow-cover fraction f_sn • Formation of dynamic sub-tiles • Redistribution of variables for dynamic sub-tiles • A couple of consistency-checks performed: • removal of various bugs mainly related to incomplete or inconsistent sub-tile redistribution • Now only slight differences to previous solution • But rime as part of interception store so far deactivated! • Degree of vectorizations can be improved • Contains already a lot of a previous test-implementation with a full • semi-transparent, loosely coupled and substantial R-cover treatment in the non-blocked COSMO-version of TERRA, • but: without all snow-related conceptual and numerical adaptations. • Introduction of the missing extension towards the full R-cover treatment including all snow-related adaptations. Offenbach 2018 Matthias Raschendorfer

18. Ad I: Resulting matrix of the extended linear system: altered • All 2 + k_soil budgets are always present (even for f_sn=0 or f_sn=1) • They are linearly coupled in the temperatures: created isc fes ifb • Can easily be tri-diagonalized by matrix-operations and solved by the standard solver • Partly reducible by parameters: degree of corrected implicit coupling of T_sn to the soil- and atm. temperatures isc: degree of considered flux-equilibrium in diagnostics of T_sf fes: degree of implicitness for effective surface fluxes used in the heat budgets ifb: Default for test: isc=1; fes=1; ifb=1 (full implicit solution active) - modified for diagnostic points

19. Ad I: Test-grid-point Kenia (+33.71_+7.89) : • After-noon situation; tropical hot with strong radiation forcing • 3 hour ICON-global test-run (R2B6) with defaults of the new SAT/TERRA-scheme (dt=6 min) • Non-default settings only for the special grid-point: T_sf LHF_sf old-sx-cpl + Ifb=1 + itv=1 old-sx-cpl + Ifb=1 + itv=1 • Oscillations almost completely eliminated by ifb=1 + itv=1 • Similar result but a bit larger daily amplitudes ifb=1 + itv=1 + fes=1(not shown) itv=1: full consideration of implicit T_sx-dependency in atmospheric transfer velocity fes=1: full consideration of flux-equilibrium at the sf surface