Overview of the Unified Radiation Package for NCEP models

Transcription

1 Overview of the Unified Radiation Package for NCEP models Yu-Tai Hou Jul 2011 DTC/EMC Workshop Development Objectives:: State of the art technology, Standardized component modules, General plug-in compatibility, Simple for implementation, Easy for update/upgrade, Computational efficient, and Flexible for future expansion. Acknowledgement: S.Moorthi, B.Ferrier, F.Yang, H.Wei, H.Lin, S.Lu, H.Vandendool, X.Wu, V.Krasnopolsky, G.Gayno, V.Wong, R.Yang, K.Campana, and many EMC personnel contributed to the development. 1

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3 Atmospheric Radiative Energy Spectral Distributions 3

4 Earth-Atmosphere Energy Budget 4

5 NCEP MODELS Cloud-Radiation Evolution Timeline GFDL LW, GFDL (L-H) SW ( ) - Prescribed cloud scheme, fixed CO2 LW transmission table. - Three-layer, latitudinal varying cloud distribution. - Pre-assigned bulk cloud optical properties. (Note: Meso model still uses the old radiations in operation but with an upgraded cloud microphysics) GFDL LW, NCEP/Chou SW (1992,1995) - Interactive (diagnostic) clouds scheme. - Layered clouds diagnosed from p, t, rh, etc - Simple empirical cloud optical properties. - No aerosol effect. 5

6 RRTM LW, NCEP/Chou SW (2003) - Prognostic cloud condensate, diagnosed cloud amount (2001). - Cloud optical properties based on parameterizations from obs. - Maximum-Random vertical cloud overlapping for LW. Random Overlapping for SW. - Monthly aerosol climatology in 5 degree horizontal resolution. Advanced radiation package (2007,,2010, ) - RRTM-LW, RRTM-SW, RRTM-LW_McICA, RRTM-SW_McICA. (** GFS starts to use RRTM-SW in 2010) - Improved cloud radiative properties and microphysics. - Maximum-Random cloud overlapping for LW and SW with optional sub-grid cloud approximation. - Upgraded aerosol scheme, surface albedo/emissivity scheme, green house gases, solar constant, etc.) - Modular structure in source codes. (Note: In NMMb, Carlos Perez put the 2007 version package, and Hsin-Mu Lin upgraded it with the 2010 version.) 6

7 GFS vs. CDAS 500mb AC Day 5 Day 6 Day 5 Day 6 Courtesy by Pete Caplan and Glenn White (September 2010) 7

8 AC Day 5 NH, by model - Aug 2010 vs Aug 2009 Courtesy by Pete Caplan and Glenn White (September 2010) 8

9 Forecast Skill of WH-MJO index Courtesy by Pete Caplan and Glenn White (September 2010) 9 Courtesy Qin Zhang NCEP/CPC

10 TOA OLR CFSR vs. R1 Radiation Global Annual Means TOA CSOLR TOA RSW TOA CSRSW SFC SW DN SFC SW UP SFC LW DN SFC LW UP Jul00- Jun05 CFSR CERES (EBAF/SARB) Diff Spatial Correlatn Jan85 - Dec86 R ERBE Dif Courtesy by S-K Yang et al. (April 2010 presentation) 10

11 Description of Module Components: - Driver Module - prepares atmospheric profiles incl. aerosols, gases, clouds, and surface conditions, etc. - SW radiation module - computes SW fluxes and heating rates (contains three separated parts: parameters, data tables, and main programs) - LW radiation module - computes LW fluxes and heating rates (contains three separated parts: parameters, data tables, and main programs) - Astronomy Module- obtains solar constant, solar zenith angles - Aerosol Module - establishes aerosol profiles and optical properties - Gas Module - sets up absorbing gases profiles (O3, CO2, rare gases, etc.) - Cloud module - prepares cloud profiles incl. fraction, ice/water pathes, and effective size parameters, etc. - Surface module - sets up surface albedo and emissivity 11

12 Highlights of the Main Characteristics of RRTM Radiation Scheme 1. Incorporates advanced technologies and is updated/upgraded frequently by AER Inc. (supported by the DOE/ARM program). - wide acceptance by many operational and research centers. 2. Uses precomputed linear-in-tau lookup table method in radiative transfer calculations. - achieving both of high accuracy and fast computation. 3. Uses optimized set of g-points and band distributions, and unifies the standard treatment for all atmospheric components. - ideally fits to the McICA sub-grid cloud application. 4. Contains wide range of green-house gaseous selections. - suits for both NWP and climate models. 12

13 GFDL0 GFDL1 NASA RRTM RRTMG RRTMG-McICA (1989) (2000) (2001) (2002) (2003) (2009) Param Sch: tran-tables Kdis/tran --- Corr-k --- No. Bands: 15* 48* No. Terms: 163* 300* Maj Gases: Same for all schemes include O 3, H 2 O, CO 2 Min Gases: - CH 4,N 2 O CH 4,N 2 O --- CH 4,N 2 O,O 2,CO CFCs 3 CFCs 4 CFCs Aerosols: no --- Capable to include aerosol effect --- Cld OVLP: Random Random 3-domain Random/Max-Ran/other Max-Ran* Cld Opt: Bulk --- CLW/CIW based in polynomial forms --- Speed: Fast Slow Very-Slow Slow Fast Fast Factor(L64) ~0.8* ~5 ~7 ~ Note: no aerosols prescribed multi-ang 1-ang McICA fixed sfc emiss 3-domain fixed co 2 tran-tb * not comparable to other schemes 13

14 GFDL0 GFDL1 NASA NCEP RRTM RRTMG RRTMG-McICA (1988) (2000) (1999) (1995) (2002) (2004) (2009) Param Sch: Kdis ESF Kdis/tran Kdis/tran --- Corr k --- No.Bands: No.Terms: Maj Gases: Same for all the schemes ( O 3,H 2 O ) Min Gases: -- CO 2, O 2 -- CO 2, O 2 CO 2, O 2 -- CO 2,CH 4,N 2 O,O 2 -- Aerosols: no --- Capable to include aerosol effect --- Cld OVLP: -- Random -- 3-domain Random Random/Max-Ran/other Max-Ran* Cld Opt: Bulk --- CLW/CIW based in polynomial forms --- Speed: Fast Very-Slow Slow Fast Very-Slow Slow Slow Factor(L64) ~0.7 ~11 ~5 1 ~8 ~4 ~5 Note: no aerosols prescribed McICA 3-domain 14

15 Driver Module Schematic Radiation Module Structure Astronomy Module Gases Module Cloud Module initialization main driver initialization solar params mean coszen initialization ozone co2 rare gases initialization prog cld1 prog cld2 diag cld Aerosol Module SW Param Module LW Param Module initialization clim aerosols Derived Type : aerosol_type GOCART aerosols Surface Module initialization SW albedo LW emissivity Derived Type : sfcalb_type SW Data Table Module SW Main Module initialization sw radiation Outputs : total sky heating rates surface fluxes (up/down) toa atms fluxes (up/down) Optional outputs: clear sky heating rates spectral band heating rates fluxes profiles (up/down) surface flux components LW Data Table Module LW Main Module initialization lw radiation Outputs : total sky heating rates surface fluxes (up/down) toa atms fluxes (up/down) Optional outputs: clear sky heating rates spectral band heating rates fluxes profiles (up/down) 15

16 Radiation_Astronomy Module Solar constant value : (Control parameter - ISOL) ISOL=0: prescribed solar constant (for NWP models) most recent cited value = 1366 w/m2 (2002); 1361 w/m2 (2011) ISOL=1: prescribed solar constant with 11-year cycle (for climate models) variation range: w/m2 obsv data range: **tabulated by H. Vandendool Sample_flx.ctl 16

17 Radiation_Gases Module CO2 Distribution : (Control parameter - ICO2) ICO2=0: use prescribed global annual mean value (currently set as 380ppmv) ICO2=1: use observed global annual mean value ICO2=2: use observed monthly 2-d data table in 15 horizontal resolution O3 Distribution : interactive or climatology Rare Gases : (currently use global mean climatology values) CH x 10-6 N2O x 10-6 O CO x 10-8 CF x CF x CF x CF x CCL x ** all units are in ppmv 17

18 Radiation_Clouds Module Cloud prediction scheme: Prognostic 1: based on Zhao/Moorthi microphysics Prognostic 2: based on Ferrier/Moorthi microphysics Diagnostic : legacy diagnostic scheme based on RH-table lookups Cloud overlapping method: (Control parameter - IOVR) IOVR = 0: randomly overlapping vertical cloud layers IOVR = 1: maximum-random overlapping vertical cloud layers Sub-grid cloud approximation: (Control parameter - ISUBC) ISUBC=0: without sub-grid cloud approximation ISUBC=1: with McICA sub-grid approximation (test mode with prescribed permutation seeds) ISUBC=2: with McICA sub-grid approximation (random permutation seeds) 18

19 Radiation_aerosols Module Aerosol distribution: (Control parameter - IAER) Troposphere: monthly global aerosol climatology in 15 horizontal resolution GOCART interactive aerosol scheme under development Stratosphere: historical recorded volcanic forcing in four zonal mean bands ( ) IAER 3-digit integer flag for volcanic, lw, sw, respectively IAER = 000: no aerosol effect in radiation calculations IAER = 001: sw tropospheric aerosols + background stratospheric IAER = 010: lw tropospheric aerosols + background stratospheric IAER = 011: sw+lw tropospheric aerosols + background stratospheric IAER = 100: sw+lw stratospheric volcanic aerosols only IAER = 101: sw tropospheric aerosol + stratospheric volcanic forcing IAER = 110: lw tropospheric aerosol + stratospheric volcanic forcing IAER = 111: sw+lw tropospheric aerosol + stratospheric volcanic forcing 19

20 Radiation_surface Module SW surface albedo: (Control parameter - IALB) IALB = 0: vegetation type based climatology scheme (monthly data in 1 horizontal resolution) IALB = 1: MODIS retrievals based monthly mean climatology (under development) LW surface emissivity: (Control parameter - IEMS) IEMS = 0: black-body emissivity (=1.0) IEMS = 1: monthly climatology in 1 horizontal resolution 20

21 Summary The unified radiation package suits for a wide range of modern NWP/climate model applications: - consists state of the art physical parameterization schemes for radiative transfer, cloud optical property, aerosol property, greenhouse gases, surface property, etc. - suitable for various model environments (only requires a simple modification of the driver module). - easy to update/upgrade/expand physical schemes in individual component modules without involving significant change to other parts of the model. - ongoing research and development includes: improve computation efficiency; and RT accuracy (mainly by AER); improve cloud/aerosol schemes and optical property treatments; enhance surface albedo/emissivity schemes; expand CO2 database and other greenhouse gases; update solar constant and its natural cycle database; develop hybrid Neural-Net radiation approximation; etc. 21