Changes between Version 13 and Version 14 of DevelopmentActivities/MergeOCN/Vuichard


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Timestamp:
2014-02-04T15:52:04+01:00 (10 years ago)
Author:
nvuilsce
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  • DevelopmentActivities/MergeOCN/Vuichard

    v13 v14  
    2626 We keep here the original formulation of Li et al., 2000 
    2727 
    28 * '''Calculation of the oxygen partial pressure'''. For both the calculation of the gradient of oxygen partial pressure (d(pO2)/dz) and the change in oxygen partial pressure (d(pO2)/dt), we need dz, the depth over which one makes the calculation. It is not clear to me which depth one should use. For information, OCN used z_decomp ([[source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_soilcarbon.f90@19#L705, see here]) 
     28* '''Calculation of the oxygen partial pressure'''. For both the calculation of the gradient of oxygen partial pressure (d(pO2)/dz) and the change in oxygen partial pressure (d(pO2)/dt), we need dz, the depth over which one makes the calculation. It is not clear to me which depth one should use. For information, OCN used z_decomp (see [source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_soilcarbon.f90@19#L705, here]) 
    2929 
    30 * '''Calculation of the oxygen partial pressure'''. Still in the calculation of the change in oxygen partial pressure (d(pO2)/dt) in OCN, it seems that "dz" term (z_decomp) is missing in the following equation ([source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_soilcarbon.f90@19#L705, here], see here]) when we compare with the reference formulation (Li et al., 2000, Eq. 4 of Table 2) 
     30* '''Calculation of the oxygen partial pressure''' (2). Still in the calculation of the change in oxygen partial pressure (d(pO2)/dt) in OCN, it seems that "dz" term (z_decomp) is missing in the following equation (see [source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_soilcarbon.f90@19#L705, here]) when we compare with the reference formulation (Li et al., 2000, Eq. 4 of Table 2) 
    3131 
    3232* '''Conversion Respiration to O2 pressure'''. The conversion factor [source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_soilcarbon.f90@19#L699, here] used for converting the respiration term in O2 pressure accounts for the air-filled porosity (see Li et al., 2000 eq. 3 table 2). In OCN, afps_max is used instead of afps. We keep the original formulation 
    … …  
    3434* '''Calculation of the anaerobic balloon - anvf'''. The two constants a and b are not specified in Li et al., 2000. OCN uses a=0.85 and b=1 without mention to any publication (see [source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_soilcarbon.f90@19#L711, here]). As mention in the code of OCN these parameters have been estimated temporarily and need to be tuned. Might be good to find the values used in DNDC... 
    3535 
    36 * '''Ammonium adsorption'''. It is based on Li et al. 1992, JGR, Table 4 using NH4 defined as the NH4+ concentration in the soil liquid, gN kg-1 soil (p. 9774) but Zhang et al. (2000) use also the same equation but in this paper NH4+ is defined as the [NH4+] in a soil layer in kgN ha-1. In OCN, NH4 seems defined as molNH4 m-3 of water ([source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_soilcarbon.f90@19#L742, see here]). It would be good to clarify this by checking what looks like the equation depending of the units we use. 
     36* '''Ammonium adsorption'''. It is based on Li et al. 1992, JGR, Table 4 using NH4 defined as the NH4+ concentration in the soil liquid, gN kg-1 soil (p. 9774) but Zhang et al. (2000) use also the same equation but in this paper NH4+ is defined as the [NH4+] in a soil layer in kgN ha-1. In OCN, NH4 seems defined as molNH4 m-3 of water (see, [source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_soilcarbon.f90@19#L742, here]). It would be good to clarify this by checking what looks like the equation depending of the units we use. 
    3737 
    38 * '''Ammonium adsorption''' (2). Li et al. (1992) defines FIXNH4 as the proportion of adsorbed NH4+. One may assume that consequently the NH4+ that is not adsorbed is NH4+ x FIXNH4 and that we want to consider this quantity for possible nitrification, transformation to ammonia, .... But in OCN, we do not multiply the state variable (SV) representing NH4+ by FixNH4 but by FixNH4/(1+FixNH4) ([source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_soilcarbon.f90@19#L746, see here]). This tends to assume that SV represents only the non adsorped NH4+ because  
     38* '''Ammonium adsorption''' (2). Li et al. (1992) defines FIXNH4 as the proportion of adsorbed NH4+. One may assume that consequently the NH4+ that is not adsorbed is NH4+ x (1-FIXNH4) and that we want to consider this quantity for possible nitrification, transformation to ammonia, .... But in OCN, we do not multiply the state variable (SV) representing NH4+ by (1-FixNH4) but by (1-FixNH4/(1+FixNH4)) (see, [source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_soilcarbon.f90@19#L746, here]). This tends to assume that FixNH4 represents the ratio adsorped NH4+ to non-adsorped because FixNH4/(1+FixNH4) = (NH4adsorp/NH4non_adsorp)/((NH4non_adsorp+NH4adsorp)/NH4_non_adsorp) = NH4adsorp / NH4tot. This needs to be clarified ...