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Frontier Research Center for Global Change

A Next-Generation Atmospheric General Circulation Modeling. Frontier Research Center for Global Change Hirofumi TOMITA Masaki SATOH Tomoe NASUNO Shi-ichi IGA Hiroaki MIURA. Contents. Motivation of our new modeling Global cloud resolving model

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Frontier Research Center for Global Change

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  1. A Next-Generation Atmospheric GeneralCirculation Modeling Frontier Research Center for Global Change Hirofumi TOMITA Masaki SATOH Tomoe NASUNO Shi-ichi IGA Hiroaki MIURA

  2. Contents • Motivation of our new modeling • Global cloud resolving model • To avoid the ambiguity of cumulus parameterization • Model description • Quasi-uniform grid in the horizontal direction • Icosahedral grid • Nonhydrostatic framework • Suitable for climate simulation • Aqua Planet Experiment • The first attempt of global cloud resolving in a long term • Summary and Future plan

  3. Motivation (1) • General problem for current AGCMs • Cumulus parameterization • One of ambiguous factors • Statistical closure of cumulus convections • Future AGCM • Explicit treatment of each cloud • Cumulus parameterization Large scale condensation scheme : not used! • Cloud microphysics : used! • Explicit treatment of multi-scale interactions • Each cloud scale  meso-scale  planetary scale  Global Cloud Resolving Model

  4. Motivation (2) • Target resolutions • 5 km or less in the horizontal direction • Several 100 m in the vertical • Strategy of dycore development • Quasi-uniform grid • Spectral method : not efficient in high resolution simulations. • Legendre transformation • Massive data transfer between computer nodes • Latitude-longitude grid : the pole problem. • Severe limitation of time interval by the CFL condition. • The icosahedral grid:homogeneous grid over the sphere • To avoid the pole problem. • Non-hydrostatic equations system • Very high resolution in horizontal direction.

  5. Current Status of Our Model Model name : NICAM(Nonhydrostatic Icosahedral Atmospheric Model)

  6. Grid generation Start from the spherical icosahedron. (glevel-0) Connection of the mid-points of the geodesic arc 4 sub-triangle (glevel-1) Iteration of this process A finer grid structure (glevel-n) # of gridpoints 11 interations are requried to obtain the 3.5km grid interval. Grid Generation Method (0) grid division level 0 (1) grid division level 1 (2) grid division level 2 (3) grid division level 3

  7. Aqua-Planet Experiment • Past reseaches • Hayashi & Sumi (1986), Swinbank et al.(1988) • Behaivior of MJO etc. • Gotswami et al.(1984), Numaguchi(1995) • Formation and intensity of Hadley circulation • APE as a standard test case • Neale & Hoskins(2001) • AMIP-like model intercomparison • experimental setup • Fixed zonal-symetric SST • Prescribed Ozone distribution • Equinoctial solar radiation • investigate the dependency of cumulus param. on the results Our approach:to perform theAPE by a cloud resolving model resolution （15km～3.5km） ONE REFERENCE RESULTS against other parameterization models

  8. Series of experiment by NICAM Analized term Spin-up time NICAM 60 day 90 day 30days Interpolation 30days Interpolation 10days Initial condition： appropriate climatology of a conventional ＧＣＭ ( CCSR/NIES/FRCGC AGCM ver 5.7) 0 day 14km gridmodel 7km gridmodel 3.5km gridmodel

  9. OLR(1S-1S平均) Super cloud cluster Mid-latitude cyclone Precipitation rate [mm/day] at day 85 : log-scaleby NICAM-3.5km model

  10. OLR (7km-model) during 60-90 day

  11. A typical Super Cloud Cluster Super cloud cluster : ~1000km Westerly wind burst Cloud cluster :~100km Low pressure High pressure Convectively-Coupled Kelvin Wave

  12. Hovmoller diagrams of OLR ( 2S-2N ) NICAM-7km NICAM-14km • Westward moving of CC  Lifetime of 2days • Eastward propagation of SCC • NICAM-14km: • 20~25 days •  fast propagation • NICAM-7km, 3.5km : • 25-40 days •  corresponding to MJO •  also well organized rather than NICAM-14km. NICAM-3.5km

  13. Histograms of diurnal cycle for precipitation Peak : midnight Peak : early morning  Consistent with the obs. in open ocean LT [hr] LT [hr]

  14. Summary • We have developed a global CRM in order to avoid the ambiguity on the cumulus parameterization. • Nonhydrostatic system • Icosahedral grid • As the first attempt of GCRM, we performed an Aqua-Planet-Experiment. • Hierarchical structure of cloud convections • MJO-like signal with realistic phase speed • Diurnal cycle of precipitation • We confirm that the GCRM approach becomes the one of major approach in the climate research field in the near future. The Global Cloud Resolving Climate Simulation is not a dream!

  15. Example of stretched grid • Stretched grid • After the transformation • Grid interval : • 120km  12km • Default grid : glevel-6 • 120km grid intv. • Homogenious Reduction of earth radius : 1/10 1.2km grid interval

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