Changes between Version 100 and Version 101 of Documentation/Forcings


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Timestamp:
2020-02-28T12:15:50+01:00 (4 years ago)
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cottle
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  • Documentation/Forcings

    v100 v101  
    3232 
    3333[[PageOutline(1-3,,pullout)]] 
    34 ORCHIDEE needs several forcing data in order to run correctly. The number of requested data is dependant of the configuration used.  
    35  
    36 In On-Line mode, the data needed are related to soil texture and color. If the vegetation is prescribed, ORCHIDEE needs in addition a vegetation information defining the fraction of each PFT per gridcell. Vegetation types gathered in these vegetation maps can be either PFT or Holson categories.  
    37  
    38 In Off-Line mode, ORCHIDEE is forced by weather data based on observations or climate model reanalysis. 
    39 Last, depending of the options activated within a run of ORCHIDEE, additional maps might be used for irrigation, slope for routing scheme, ... 
     34ORCHIDEE needs several forcing data in order to run correctly. The number of requested data depends on the configuration used.  
     35 
     36In On-Line mode (coupled with LMDZ), the data needed are related to soil texture and albedo. If the vegetation is prescribed, ORCHIDEE needs in addition the definition of the fraction of each PFT per gridcell. Vegetation types gathered in these vegetation maps can be either PFT or Holson categories.  
     37 
     38In Off-Line mode, ORCHIDEE is forced by weather data based on observations or climate model reanalysis and these data need to be added. 
     39Last, depending on the options activated within a run of ORCHIDEE, additional maps might be used for irrigation, slope for routing scheme, ... 
    4040 
    4141==  0. General information == 
    … …  
    4747It is the role of the driver to inter/extrapolate timeseries of the forcing meteorological variables at the time step of ORCHIDEE (usually 30 min) based on the forcing dataset. 
    4848 
    49 (b) '''Two versions of the driver are available''' to do do both the reading and the inter/extrapolation of the forcing datasets. They differ in the way they interpret the time at which the diffrent variables are read in the forcing dataset (further called the timestamp, while the interval refers to the period between two succesive timestamps): 
     49(b) '''Two versions of the driver are available''' to do both the reading and the inter/extrapolation of the forcing datasets. They differ in the way they interpret the time at which the different variables are read in the forcing dataset (further called the timestamp, while the interval refers to the period between two successive timestamps): 
    5050* '''the old driver (src_driver/dim2driver)''', which assumes that scalar variables (Tair,Qair,Psurf,Wind) are instantaneous values at the timestamp, while flux variables (Rainf,Snowf, SWdown, LWdown) are mean values over the interval ending at the timestamp. This driver also requires that the first value of the annual files corresponds to 00UTC+dt_forcing (for instance 03UTC for a 3hourly forcing), and that the last value is for Dec 31st at 24UTC = 00UTC on Jan 1st of the following year. 
    51 * '''the new driver (src_driver/orchideedriver.f90) is more flexible''' and can normally deal with any temporal structure of the forcing datasets, provided the required attributes are inserted in the forcing files. Yet, orchideedriver is not yet compatible with libIGCM. This document [attachment:Description_Forcing_Files.pdf] provides details of how forcing files need to be prepared. It addresses in particular the issues one may face when the fluxes are averaged and scalar variables instantaneous. The driver needs to take this into account else the diurnal cycle can be misplaced. Some data providers have different convention for representing averaged fluxes and this type of details matter.  
     51* '''the new driver (src_driver/orchideedriver.f90) is more flexible''' and can normally deal with any temporal structure of the forcing datasets, provided the required attributes are inserted in the forcing files. Yet, orchideedriver is not yet compatible with libIGCM. This document [attachment:Description_Forcing_Files.pdf] provides details of how forcing files need to be prepared. It addresses in particular the issues one may face when the fluxes are averaged and scalar variables are instantaneous. The driver needs to take this into account else the diurnal cycle can be misplaced. Some data providers have different conventions for representing averaged fluxes and this type of details matters.  
    5252 
    5353A longer discussion on the differences between the two drivers (dated in 2016) can be found on https://forge.ipsl.jussieu.fr/orchidee/wiki/Branches/Driver_Improvements. 
    … …  
    5555(c) '''Adding the cell_methods attribute to files'''. 
    5656It is a good practice to add the cell_methods attribute to each of the forcing variable in order to document how they relate to the time axis and their representativity in time. This attribute will say if the variable represents a point in time (instantaneous) or averages  over an interval (mean). Furthermore it can inform how the time interval over which the variable is valid relates to the discrete points in time the axis provides. 
    57 The general form of the attribute follows the CF convention and is "cell_methods = axname : method(position)" where the folowing values can be inserted : 
     57The general form of the attribute follows the CF convention and is "cell_methods = axname : method(position)" where the following values can be inserted : 
    5858 * '''axname : ''' The name of the time axis within the file that is valid for the current variable 
    5959 * '''method :''' instantaneous, mean 
    … …  
    6262More details and examples are provided in this document : https://forge.ipsl.jussieu.fr/orchidee/wiki/Branches/Driver_Improvements. 
    6363 
    64 (d) '''Usually, the forcing files are stored in the shared accounts''' in IGCM/SRF/METEO directory.  
    65  
    66 The path to the shared accounts is defined for the various computing centers in ​https://forge.ipsl.jussieu.fr/igcmg_doc/wiki/Doc/ComputingCenters/SharedFiles 
     64(d) '''Usually, the forcing files are stored in the shared accounts''' in IGCM/SRF/METEO directory. The shared accounts are found: 
     65 * At TGCC: /ccc/work/cont003/dsm/p86ipsl/IGCM  
     66 * At IDRIS: 
     67   * On the ada machine: /workgpfs/rech/psl/rpsl035/IGCM 
     68   * On the ergon machine: /u/rech/psl/rpsl035/IGCM   
     69 * LSCE, obelix : /home/orchideeshare/igcmg/IGCM 
     70 * IPSL Ciclad : /prodigfs/ipslfs/igcmg/IGCM 
     71 * At the web by DODS : ​http://dods.ipsl.jussieu.fr/igcmg/IGCM  
    6772 
    6873The datasets available from the shared accounts are noted with a *. 
    69 Some additional forcings not yet on the shared acount can be found at climserv/ciclad here /bdd/ORCHIDEE_Forcing/BC/OOL/OL2 
     74Some additional forcings not yet on the shared accounts can be found at climserv/ciclad here /bdd/ORCHIDEE_Forcing/BC/OOL/OL2 
    7075 
    7176Read more about the shared accounts and IGCM repository here [http://forge.ipsl.jussieu.fr/igcmg_doc/wiki/DocBenvEcommonfiles] 
    … …  
    7883   - FORTRAN 90 script to create a land points only forcing file (use of the compress attribute) [attachment:mk_grid.f90] 
    7984* '''SPRED_PREC''' for forcings at 3 and 6 hourly time step:  
    80    - This externalizable keyword defines the nb of orchidee time steps on which the precipitation total of the forcing time step is spread. It can induce significant chnages on the model's behavior (interception and interception loss, infiltration, runoff and ET), although this hasn't been assessed in a systematic way.  
     85   - This externalizable keyword defines the nb of orchidee time steps on which the total precipitation is spread over the time step. It can induce significant changes on the model's behavior (interception and interception loss, infiltration, runoff and ET), although this hasn't been assessed in a systematic way.  
    8186   - By default, we spread the precipitation over half the forcing time step (1.5h and 3h respectively for 3-hourly and 6-hourly files).  
    8287* '''New driver''': you need to add a time attribute to each variable, e.g. "time: instantaneous" our "time: mean(end)", further details in [attachment:Description_Forcing_Files.pdf].    
    … …  
    150155Where ? Not in IGCM repository or IGCM_ARCHIVE.  
    151156 
    152 This data corresponds to the one described in the publication Weedon et al. 2014 (http://onlinelibrary.wiley.com/doi/10.1002/2014WR015638/abstract). Compared to WFD, WFDEI offers values in the 21st century owing the ERA-Intermin reanalysis. 
     157This data corresponds to the one described in the publication Weedon et al. 2014 (http://onlinelibrary.wiley.com/doi/10.1002/2014WR015638/abstract). Compared to WFD, WFDEI offers values in the 21st century owing the ERA-Interim reanalysis. 
    153158|| Name || || Spatial information || ||Temporal information || || || || Web documentation || || || Size || 
    154159|| Abbreviation || Full name || Coverage || Resolution || First year || Last year || Number of years || Resolution || Informations || Data download || References || GB || 
    155160|| WFDEI_CRU_yyyy.nc || WFDEI_CRU || -180:180; -90:90 || 720x360 || 1979 || 2016 || 34 || 3H || || November 2017 || || 314 GB || 
    156161 
    157 As this data is based on the ERA-I re-analysis the fluxes are cumulated over the 3h period preceding the time-stamp. All other variables are instantaneous at the given date. This is now properly described by the cell_method data in the netCDF file.  
     162As this data is based on the ERA-I re-analysis the fluxes are cumulated over the 3h period preceeding the time-stamp. All other variables are instantaneous. This is now properly described by the cell_method data in the netCDF file.  
    158163 
    159164=== 1.4 WFDEI_GPCC === 
    … …  
    164169 
    165170This is the same atmospheric forcing as the one described above (1.6 WFDEI_CRU) except that rainfall is now corrected with the GPCC data : http://www.dwd.de/bvbw/appmanager/bvbw/dwdwwwDesktop?_nfpb=true&_windowLabel=T12404818261141645314319&_urlType=action&switchLang=en&_pageLabel=_dwdwww_klima_umwelt_datenzentren_wzn 
    166 As this rainfall series is shorter, WFDEI_GPCC has fewer years than WFDEI_CRU. 
     171As this rainfall series is shorter, WFDEI_GPCC has less years than WFDEI_CRU. 
    167172 
    168173==== WFDEI_GPCC/v1/noleap ==== 
    … …  
    173178|| WFDEI_GPCC_yyyy.nc || || -180:180; -90:90 || 720x300 || 1979 || 2009 || 31 || 3H || || 3 juin 2013|| || 182 GB || 
    174179 
    175 The old driver (dim2driver) needs a forcing that has its first record at 0 UTC, in addition to instanteaneous "scalars" and fluxes as mean(end), to work correctly. The original WFDEI starts at 3UTC, and to make it compatible with with dim2driver, a lag of 3 hours has been introduced by Ben Poulter and Fabienne Maignan. 
     180The old driver (dim2driver) needs a forcing that has its first record at 0 UTC, in addition to instanteaneous "scalars" and fluxes as mean(end), to work correctly. The original WFDEI starts at 3UTC, and to make it compatible with dim2driver, a lag of 3 hours has been introduced by Ben Poulter and Fabienne Maignan. 
    176181 
    177182==== WFDEI_GPCC/v2/leap  ==== 
    … …  
    201206 
    202207General information on GSWP3 data from personal communication between Hyunjun Kim and Agnes Ducharne: 
    203 - All variable treated in the same way in terms of time averaging. First time record should corresponds to 00UTC, but please note values represents "backward averaging" which means 00UTC is mean of -03 ~ 00UTC. 
    204 - Wind should be assumed to represent speed at 10 m. Downscaled reanalysis wind speed is at 10m, but CRU CL2.0 data which is used to correct long-term mean has not been corrected for any measurement height related issue. New et al. (2002) says "Wind speed is measured at heights above the surface of between 2 and 20 m. Measurement height varies both within and between countries, and in many cases the heights were not specified. Consequently, no corrections were made to wind data. The large majority of known heights were 10 m, and the interpolated wind field should be assumed to represent speed at this height." 
     208- All variables are treated in the same way in terms of time averaging. First time record should correspond to 00UTC, but please note that some variables represent "backward averaging" which means  that the value at 00UTC is an averaged over the -03 ~ 00UTC time period. 
     209- Wind should be assumed to represent speed at 10 m. Downscaled reanalysis wind speed is at 10m, but CRU CL2.0 data (which is used to correct long-term mean) has not been corrected for any measurement height related issue. New et al. (2002) says "Wind speed is measured at heights above the surface between 2 and 20 m. Measurement height varies both within and between countries, and in many cases the heights are not specified. Consequently, no corrections were made to wind data. The large majority of known heights were 10 m, and the interpolated wind field should be assumed to represent speed at this height." 
    205210 
    206211==== GSWP3/v1_halfdeg ==== 
    … …  
    212217A detailed analysis of the formatted dataset was done by Salma Tafasca (PhD student at METIS) using the old driver, see [attachment:Preparing_GSWP3_V1_Official.pdf]. A comparison of the interpretation of this forcing by the two drivers was done by Vlad: https://orchidas.lsce.ipsl.fr/mapper/meteo_inter.php 
    213218The results show a lag of 1h30 for the scalars and the interpolation by the new driver is a priori better. 
    214 For the fluxes, SW results are identical with the two drivers, LW results are different but would probably be identical if this flux was not interpolated linearly but uniformly (recommended to conserve the fluxes), and the differences in precipitation comme from different spred_prec parameters.  
     219For the fluxes, SWdown results are identical with the two drivers, LWdown results are different but would probably be identical if this flux was not interpolated linearly but uniformly (recommended to conserve the fluxes), and the differences in precipitation come from different spred_prec parameters.  
    215220 
    216221|| Name || || Spatial information || ||Temporal information || || || || Web documentation || || || Size || 
    … …  
    282287This data set is available at ciclad here: /bdd/ORCHIDEE_Forcing/BC/OOL/OL2/ERAI_05 . 
    283288 
    284 This meteorological data set has been prepared by ECMWF in the framework of the Earth2Observe project : http://www.earth2observe.eu/ 
    285  
    286 Using a simple bi-linear interpolation the data of the ERA-I re-analysis on the Gaussian grid (N128) output was projected to a regular lat/lon grid at 0.5deg resolution, without special consideration for the land/sea mask. It was thus considered, in consultation with Emanuel Dutra of ECMWF, that it was not unreasonable to use the same land/sea mask as WFDEI and hope that the atmospheric forcing on coastal points will not be too badly affected by the methodology. 
     289This meteorological dataset has been prepared by ECMWF in the framework of the Earth2Observe project : http://www.earth2observe.eu/ 
     290 
     291Using a simple bi-linear interpolation the data of the ERA-I re-analysis on the Gaussian grid (N128) output was projected to a regular lat/lon grid at 0.5deg resolution, without special consideration for the land/sea mask. It was thus considered, in consultation with Emmanuel Dutra of ECMWF, that it was not unreasonable to use the same land/sea mask as WFDEI and hope that the atmospheric forcing on coastal points will not be too badly affected by the methodology. 
    287292 
    288293The value of this forcing lies in its close relation to the ERA-I re-analysis and its extension to December 2014.