Changes between Version 11 and Version 12 of DevelopmentActivities/CMIP6/DevelopmentsCMIP6/zo_evaporation


Ignore:
Timestamp:
2016-02-23T12:16:54+01:00 (8 years ago)
Author:
nvuilsce
Comment:

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  • DevelopmentActivities/CMIP6/DevelopmentsCMIP6/zo_evaporation

    v11 v12  
    158158== Summary of the tests performed on z0 formula for reducing bare soil evaporation  (N. Vuichard) ==  
    159159 
     160 
     161=== Context === 
    160162Since the update of the 11-layer hydrological scheme into the trunk of ORCHIDEE in 2012, a strong positive bias on latent heat flux has been diagnosed with the 11-layer scheme at winter time for deciduous species compared to observations and compared to the 2-layer scheme. The figure below shows how the seasonal variations of the latent heat flux simulated with the 2-layer scheme and the 11-layer scheme compare to observations for different PFTs: 
    161163 
    … …  
    166168This overestimation of the latent flux when there is no contribution of transpiration but only bare soil evaporation is not observed over the cropland sites when the soil is bare. 
    167169 
     170=== The Su formulation === 
     171 
    168172Consequently, one searched for a process/formula embedded into ORCHIDEE parametrized differently for trees and herbaceous PFTs and that may impact on the latent heat flux Analysis of the code. This is the case of the formulation of the roughness length (z0 parameter). In ORCHIDEE, one assumes that the roughness length of the herbaceous PFTs varies with the LAI, while the roughness length of Trees PFT does not. See the block of code here in condveg: 
    169173https://forge.ipsl.jussieu.fr/orchidee/browser/trunk/ORCHIDEE/src_sechiba/condveg.f90?rev=2425#L1526 
    170174 
    171 Some authors have proposed formulations of z0 which vary with the LAI as it is roughly done for herbaceous PFTs into ORCHIDEE. For instance, [attachment:su_2001.pdf Su et al. (2001)] developed such formulation which has been used and tested recently at fluxnet sites by [attachment:ershadi_2015.pdf Ershadi et al. (2015)]. The formulation of Su et al., 2001 has be implemented into ORCHIDEE. Inclusion the Su formula for z0 leads to reduce/cancel the bias on latent heat flux at winter for deciduous forest (TeDBF pfts). Results obtained with this formulation are shown below: 
     175Some authors have proposed formulations of z0 which vary with the LAI as it is roughly done for herbaceous PFTs into ORCHIDEE. For instance, [attachment:su_2001.pdf Su et al. (2001)] developed such formulation which has been used and tested recently at fluxnet sites by [attachment:ershadietal2015.pdf Ershadi et al. (2015)]. The formulation of Su et al., 2001 has been implemented into ORCHIDEE. Inclusion the Su formula for z0 leads to reduce/cancel the bias on latent heat flux at winter for deciduous forest (TeDBF pfts). Results obtained with this formulation are shown below: 
     176 
     177||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_BoENF/lh_month_9874/lh_month.gif,100%)]]||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_CROc3/lh_month_22172/lh_month.gif,100%)]]||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_CROc4/lh_month_21877/lh_month.gif,100%)]]||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_GRAc3/lh_month_7894/lh_month.gif,100%)]]||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_TeDBF/lh_month_3593/lh_month.gif,100%)]]||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_TeEBF/lh_month_15717/lh_month.gif,100%)]]||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_TeENF/lh_month_20645/lh_month.gif,100%)]]||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_TrEBF/lh_month_21204/lh_month.gif,100%)]]|| 
     178 
     179=== The "z0h=z0m/10" formulation === 
     180In the formulation of Su and many others, one distinguishes for the roughness length for heat (z0h) and for momentum (z0m). Fuxing has studied in coupled mode how accounting for both z0m and z0h in the formulation of the drag coefficient impacts on the surface fluxes and properties (temperature). Here we look at the impact on force in-situ simulations of accounting for the formula where z0h=z0m/10. 
     181 
     182||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_BoENF/lh_month_9874/lh_month.gif,100%)]]||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_CROc3/lh_month_22172/lh_month.gif,100%)]]||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_CROc4/lh_month_21877/lh_month.gif,100%)]]||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_GRAc3/lh_month_7894/lh_month.gif,100%)]]||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_TeDBF/lh_month_3593/lh_month.gif,100%)]]||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_TeEBF/lh_month_15717/lh_month.gif,100%)]]||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_TeENF/lh_month_20645/lh_month.gif,100%)]]||[[Image(http://dods.extra.cea.fr/work/p86ghatt/OL2/PROD/ref2425/FL1.CWRR.2425/fluxnet_taylor_diff_FL1.CWRR.2425_FL1.Choi.2425_TrEBF/lh_month_21204/lh_month.gif,100%)]]||