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Clouds and radiation in the GRAPES NWP model Qiying Chen National Meteorological Center China Meteorological Administration Exeter, Apr. 16 2013 4th WGNE.

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Presentation on theme: "Clouds and radiation in the GRAPES NWP model Qiying Chen National Meteorological Center China Meteorological Administration Exeter, Apr. 16 2013 4th WGNE."— Presentation transcript:

1 Clouds and radiation in the GRAPES NWP model Qiying Chen National Meteorological Center China Meteorological Administration Exeter, Apr. 16 2013 4th WGNE workshop on systematic errors in weather and climate models

2 1. Model and Verification Data 2. Cloud and Radiation in GRAPES 3. New Cloud and Radiation Parameterization 4. Improvements in radiation and weather forecast 5. Disscussion Outline

3 GRAPES_GFS global model SISL dynamical core with mass fixer Physics Radiation: RRTM longwave and GSFC shortwave radiation schemes Cumulus: new Kain-Fritsch (NKF) cumulus parameterization Microphysics: NCEP mixed-phase microphysics Cloud: binary cloud Land surface: NOAH land surface model PBL: YSU planetary boundary layer 1. Model and verification data

4 Satellite 、 Analysis 、 Gauge measurements ISCCP cloud cover 、 precipitable water content 、 cloud water path and radiation budget SOBS cloud cover GPCP precipitation SSMI precipitable water content 、 cloud water path 、 10m full wind speed CERES Aqua radiation budget NCEP FNL atmospheric circulation 、 surface element 400 monitoring stations in China Temperature 、 Wind and precipitation

5 Global mean surface radiation budget CERESISCCPGRAP ES Surface radiation balance (W m -2 ) Upwelling LW400405404 Downwelling LW353357334 Net LW-47-48-71 Upwelling LW CRF--20 Downwelling LW CRF--3016 Net LW CRF312815 Upwelling SW221725 Downwelling SW184177231 Net SW162160206 Upwelling SW CRF---5-3 Downwelling SW CRF---57-27 Net SW CRF-42-52-24 -19 24 4 3 47 44 2. Cloud and Radiation in GRAPES

6 TOA radiation balance (W m -2 ) OLR244240278 Net LW CRF27 3 Upwelling SW9610066 Net SW235231265 Net SW CRF-48-50-21 CERESISCCPGRAPES 34 Global mean TOA radiation budget weighted by area for July

7 TCCHCCMCCLCC ISCCP0.650.140.200.26 GRAPES0.490.340.130.21 Global mean cloud cover weighted by area Global mean cloud liquid water path weighted by area SSMIISCCPNCEP FNL GRAPE S cloud liquid water path (g/m2) Global 666324 Ocean 89636427 Insufficient cloud cover and liquid water amounts is the main reason for underestimation of CRF

8 Total Cloud Cover Cloud Liquid Water Path Substantial underprediction of cloud water content, especially in the ITCZ

9  New cloud cover parameterization  New cloud water path parameterization  Radiation effect of fractional cloud  Radiative effect of cloud inhomogeneity 3. New Cloud and Radiation Parameterization

10 Original scheme: binary cloud cloud=1, when QC+QI >1.0e-6 cloud=0, when QC+QI <1.0e-6 effective cloud drop radius: liquid 10µm 、 ice 80µm New scheme Liang and Wang （ 1995 ） Cloud cover: Combine Slingo and Slingo （ 1991 ） and Kiehl et al. （ 1994 ） ; 4 cloud genera : convective cloud, anvil cirrus, inversion stratus and stratiform cloud 。 Fractional cloud cover and vertical cloud overlapping are considered effective cloud drop radius: liquid cloud: Savijarvi 1997 ice cloud: Kiehl et al. 1996 Cloud cover parameterization

11 Cloud cover compared with ISCCP satellite data Zonal mean total (TCC), middle (MCC) and low (LCC) cloud cover (%) of the ISCCP data (dashed) and the 5th day forecast by GRAPES using the ORG (thin solid) and NEW (thick solid) cloud scheme. Using ISCCP Simulator

12 Zonal mean total (TCC) and low (LCC) cloud cover (%) of the SOBS data (dashed) and the 5th day forecast by GRAPES using the ORG (thin solid) and NEW (thick solid) cloud scheme Cloud cover compared with SOBS surface cloud climatology Direct output from model

13 Cloud water path parameterization cloud water content from convection can be included Based on CRM simulations and ARM observations

14 Sensitivity experiment (hl,clwc0) SSMI/ CERES CLWP0 (0.19) CLWP1 (0.5) CLWP2 (1.0) CLWP3 (0.9) Cloud water path （ g/m2 ） 894759119116 Surface net SW （ w/m2 ） 1618 17 Surface net LW （ w/m2 ） -47-54-53-52 Cloud water path Surface net SW Surface net LW

15 Radiation effect of fractional cloud A scale factor enable fractional cloud effect Much better RRTM LW treat only binary cloud: cldfrc>0, cldfrc is set to 1, so overestimate cloud effect FCLSCALE -maximum cloud cover in each grid column the grid mean fractional cloud input to the radiation scheme is extended into the full range of FCLSCALE, ( cloud cover *optical depth) conserving when the input cloud amount of a layer is less than FCLSCALE, the optical depth per unit area at that layer is attenuated FCLSCALE clear sky

16 Radiative effect of cloud inhomogeneity Assuming a homogeneous cloud property distribution overestimates total cloud albedo (Cahalan et al. 1994 ) Improve obviously Following Liang and Wu (2005), introduce a reduction factor to include the cloud inhomogeneity effect

17 CERESISCCPORGNEW Surface radiation balance (W m -2 ) Upwelling LW400405404408 Downwelling LW353357334365 Net LW-47-48-71-44 Upwelling LW CRF--201 Downwelling LW CRF--301632 Net LW CRF31281531 Upwelling SW22172521 Downwelling SW184177231182 Net SW162160206161 Upwelling SW CRF---5-3-7 Downwelling SW CRF---57-27-71 Net SW CRF-42-52-24-64 4. Comparison of surface radiation budget Errors reduce 14-471-8

18 TOA radiation balance (W m -2 ) OLR244240278233 Net LW CRF27 335 Upwelling SW9610066106 Net SW235231265225 Net SW CRF-48-50-21-62 CERESISCCPORGNEW Comparison of TOA radiation budget Errors reduce from 29-343-8

19 Comparison of CRF

20 Comparison of net flux

21 Comparison of surface 2m temperature errors

22 Statistical verification

23  To focus on improving CRF, the radiation and microphysics processes are temporarily decoupled.  Develop Macro cloud, when horizontal resolution is not high enough, grid saturation can not be achieved.  Consider cloud cover from convection 5. Discussion

24 Thank you ！

25 （ 1 ） Compare with satellite-retrieved cloud covers, cloud water contents, and radiative fluxes and identify the errors in GRAPES. （ 2 ） Analyze source of errors （ 3 ） Improve cloud-radiation interaction （ 4 ） Impacts on weather forecast skills 1. Aim of the Study

26 3. Cloud and Radiation in GRAPES 3 basic definition Net flux=dowelling flux-upward flux Cloud radiative forcing (CRF) =flux in all sky (cloudy)- flux in clear sky Cloud liquid water path =Vertically integrated cloud liquid water content

27 Cloud is calculated in terms of ：

28 Effective cloud drop radius liquid ice

29 Sensitivity experiment (hl,clwc0) SSMI/ CERES CLWP0 (0.19) CLWP1 (0.5) CLWP2 (1.0) CLWP3 (0.9) Cloud water path （ g/m2 ） 894759119116 Surface net SW （ w/m2 ） 1618 17 Surface net LW （ w/m2 ） -47-54-53-52 Cloud water path Surface net SW Surface net LW

30 Comparison of global mean precipitation

31 7 月 NEWNEW ORGORG July

32 Jan ORGORG NEWNEW

33 Total Cloud CoverCloud Liquid Water Path

34 JulySSMIORIGNEW Cloud water path(g/m2) 8927115 JanSSMIORIGNEW Cloud water path(g/m2) 8525119 5. Improvement in radiation and weather forecast July Jan

35 QV ≥QSW 或 QV≥QSI ， RH≥100% QV≤QSW 或 QV≤QSI ， RH 0 ≤RH<100% ?

36 BASIC EQUATIONS FOR CLOUD Here, S conv, is convective impact for grid-scale cloud S strat is grids-cale condensation and cloud microphysical source and sink items when f 0 ≤RH≤1 X ϵ c, r,i,s,g Cloud,rain,ice, snow graupel

37 Two_MomentTwo_Moment + Macro cloud 宏观 云改 进 Vertical distribution of total condensate

38 Total Cover Cover Diagnostic cloud schemePrognostic cloud scheme

39 Feedback of sudgrid cloud to grid cloud No feedback With feedback No feedback With feedback Cloudwater Gridscaleprecipitation

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