Changes between Version 4 and Version 5 of DevelopmentActivities/CMIP6/DevelopmentsCMIP6/zo_evaporation
- Timestamp:
- 2015-10-26T11:27:11+01:00 (9 years ago)
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DevelopmentActivities/CMIP6/DevelopmentsCMIP6/zo_evaporation
v4 v5 118 118 Within the Earth2Observe project a paper on the Tier 1 simulations has been submitted by Schellekens et al.. it include the following table : 119 119 120 [[Image(Table3.png, 80%)]]120 [[Image(Table3.png, 60%)]] 121 121 122 122 For this dataset it was the Trunk of July 2014 which was run but with the new driver. This meant a more accurate calculation of ETP from the WFDEI_CRU forcing. One immediately notes that evaporation is too high in ORCHIDEE and thus sets us apart from the other models. In order to test how much this is the result of years of accepting too high turbulence in order to compensate for too low ETPs produced the old driver, I re-ran the same code but dividing z0 by 10. The simulation is not yet finished so only the 90s are analysed. … … 124 124 The change in z0 is pictured below : 125 125 126 [[Image(Z0_Diff.png, 80%)]]126 [[Image(Z0_Diff.png, 60%)]] 127 127 128 128 This modification leads to a weak but significant reduction of evaporation as pictures below : 129 129 130 [[Image(Evap_Diff.png, 80%)]]130 [[Image(Evap_Diff.png, 60%)]] 131 131 132 Globally this translate into a reduction of evaporation of about 4%.132 Globally this translate into a reduction of evaporation of about 3.9%. 133 133 134 If we consider that the 90's are a representative sample in the 34 WFDEI_CRU forcing, then we can apply this reduction to the mean ORCHIDEE number of 609 kg/m²/y and obtain 585kg/m²/y. With this reduction, ORCHIDEE is still in the higher evaporating models but very close to HTESSEL and SURFEX.134 The analysis is performed over 34 WFDEI_CRU forcing years (1979-2012). We can apply this reduction to the mean ORCHIDEE number of 598 kg/m²/y and obtain 574 kg/m²/y. With this reduction, ORCHIDEE is still in the higher evaporating models but very close to HTESSEL and SURFEX. 135 135 136 136 This suggests to me that indeed we have been using Z0h=Z0m for years as a compensation for errors in the forcing. This is corroborated by analysis of the water cycle of the Mediterranean basin where ORCHIDEE systematically shows too much water in the rivers and thus too little evaporation. Choosing lower Z0h values in ORCHIDEE will allow to differentiate Z0m and Z0h in LMDZ, lowers evaporation and probably prepare us for a more complete parametrisation for estimating Z0h, like the one proposed by Su et al.