[MITgcm-support] MITgcm-support Digest, Vol 201, Issue 13

ESTANISLAO GAVILAN PASCUAL-AHU e.gavilan at hhu.edu.cn
Tue Mar 17 02:35:06 EDT 2020


Hi Mike,

I have just double checked the units in the documentation. Unless I am looking to the wrong parameter, the downward radiation is given in J m-2 see page.
https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-single-levels
Surface solar radiation downward:
	This parameter is the amount of solar radiation (also known as shortwave radiation)....The units are joules per square metre (J m-2 ). To convert to watts per square metre (W m-2 ), the accumulated values should be divided by the accumulation period expressed in seconds. ....
Surface thermal radiation downwards:
         Idem...

 Kind regards,

Estanislao
> Content-Type: text/plain; charset="gb2312"
> 
> Hi,
> 
> I am grateful to everyone for your reply, and here I will respond to your suggestions.
> 
> 1.for Dr. Stanislav Martyanov =========================================
> 
> Thank you for sharing the meteorological forcing variables used in the ERA5 dataset, which has benefited me a lot.
> 
> But I am a bit puzzled. The GLOBAL_REANALYSIS_PHY_001_030 you mentioned should be a product of the NEMO model. Is this the open boundary forcing data you use?
> 
> 
> 2.for Estanislao ===================================================
> 
> Thank you for your reminding. Before using the data, it is very important to know the unit of the variable, just like the unit of precipitation in ERA5 is kg ? m-2 s-1, and the unit of the corresponding variable in MITgcm-EXF is m ? s-1. In this case, you need to divide by the density of fresh water for conversion.
> 
> About the unit of long and short wave radiation flux in ERA5, I'm sure that it is W ? m-2, and there should be no problem in the unit of other variables.
> 
> 
> 3.for Raf =======================================================
> 
> Thank you for your experience. The package I use is EXF. I simply looked at the code of EXF and found that it is calling exf_bulkformulae.F for related calculations.
> 
> C     us  - mean wind speed (m/s)     at height hu (m)
> C     th  - mean air temperature (K)  at height ht (m)
> C     qh  - mean air humidity (kg/kg) at height hq (m)
> 
> As for the definition of various variables in height, exf_readparms. F has made relevant definitions, and I have checked that it is correct.
> 
>    zref           =       10.000  _d 0
>    hu             =       10.000  _d 0
>    ht             =        2.000  _d 0
> 
> 
> 4.for Hong =======================================================
> 
> Thank you for your checking. I'm sorry I didn't make it clear. I put net short-wave radiation flux (nswrs) in swfluxfile, since swdown will be ignored when using swdown and swflux at the same time, so I removed swdownfile.
> 
> (PID.TID 0000.0001) ** WARNING ** EXF_CHECK: "swdown" field is loaded from file but not used within pkg/exf
> 
> 
> Next ============================================================
> It seems that you don't have the same problem as me. Next, I plan to use ERA5 and NCEP data at the same time to find the reason for the difference between the results of model by the method of exclusion.
> 
> 
> 
> Best,
> -Mike
> ________________________________
> ???: MITgcm-support <mitgcm-support-bounces at mitgcm.org> ?? Raphael Dussin <raphael.dussin at gmail.com>
> ????: 2020?3?16? 20:24
> ???: mitgcm-support at mitgcm.org <mitgcm-support at mitgcm.org>
> ??: Re: [MITgcm-support] ??: ??: The obvious difference between ERA5 and NCEP-R1 forcing
> 
> Have you checked the heights for the atmospheric variables are correctly set?
> you should have something like this in data.blk
> 
> zref = 10.0
> zwd = 10.0
> zth = 2.0
> 
> I've seen a lot of runs going off the rails because of this kind of problem:
> If the height is not set right, the fluxes are not either and you end up with large biases.
> 
> hope it helps,
> Raf
> 
> 
> 
> 
> Raf
> 
> 
> 
> Le lun. 16 mars 2020 ? 04:49, Stanislav Martyanov <martyanov.sd at gmail.com<mailto:martyanov.sd at gmail.com>> a ?crit :
> Hello, Mike!
> 
> I have recently downloaded the ERA5 reanalysis data (daily fields,  GLOBAL_REANALYSIS_PHY_001_030 as labeled in Copernicus network) in order to construct the meteorological forcing for a regional ocean model (Kara Sea) based on the MITgcm. I chose the following fields:
> 
> %           10m u-component of wind
> %           10m v-component of wind
> %           2m dewpoint temperature
> %           2m temperature
> %           Mean total precipitation rate
> %           Mean sea level pressure
> %           Mean surface downward long-wave  radiation flux
> %           Mean surface downward short-wave radiation flux
> 
> In order to compute the specific humidity, as advised in the ERA5 documentation, I used formulas given in IFS Documentation CY46R1 - part-iv-physical-processes (2m dewpoint temperature and Mean sea level pressure are used there).
> 
> Regards,
> 
> Dr. Stanislav Martyanov,
> Shirshov Institute of Oceanology,
> Russia
> 
> 
> ??, 16 ???. 2020 ?. ? 09:27, Leming Van <ifanliming at outlook.com<mailto:ifanliming at outlook.com>>:
> Hi, Matt
> 
> Thank you for your advice. I'm sorry that I didn't provide enough information.
> 
> I downloaded the ERA5 dataset at https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-single-levels?tab=form
> Copernicus Climate Data Store | Copernicus Climate Data Store<https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-single-levels?tab=form>
> CDS Menu. Home; Search; Datasets; Applications; Toolbox; FAQ; Live; Copernicus Climate Data Store
> cds.climate.copernicus.eu<http://cds.climate.copernicus.eu>
> 
> And I selected precip[mean_total_precipitation_rate. kg m-2 s-1], atemp[2m_temperature. K], swdown[mean_surface_downward_short_wave_radiation_flux. W m-2], lwdown[mean_surface_downward_long_wave_radiation_flux. W m-2], uwind[10m_u_component_of_wind.  m s-1], vwind[10m_v_component_of_wind.  m s-1], because ERA5 does not provide aqh directly, I used air pressure[surface_pressure  Pa] and dewpoint temperature[2m_dewpoint_temperature  K] to calculate aqh.
> 
> Since the data is hourly, I only downloaded the area of interest(bigger than South China Sea), and besides, the data is zonally aligned from 35N to 5S, I flipped it to 5S-35N.
> 
> I compared the ERA5 with NCEP, and I don't think there is much difference except for the short-wave radiation. Please check the attachment.
> 
> I only have one question, do you choose the same ERA5 variables like me? If not, could you tell me which variables you choose?
> 
> Please let me know if any other files are needed for diagnosis. Thanks in advance.
> 
> 
> -Mike
> 
> 
> Here is the setting of my data.exf
> 
> # $Header: /u/gcmpack/MITgcm_contrib/eh3/llc/ecco-godae/input_50lev/data.exf,v 1.1 2007/03/06 19:13:51 heimbach Exp $
> #
> # *********************
> # External Forcing Data
> # *********************
>  &EXF_NML_01
>  useAtmWind        = .TRUE.,
> # rotateStressOnAgrid = .TRUE.,
>  exf_iprec         = 32,
>  exf_yftype        = 'RL',
>  useExfYearlyFields = .false.,
>  twoDigitYear      = .false.,
>  useExfCheckRange  =.false.,
>  &
> 
>  &EXF_NML_02
>  climsstfile        = 'woa13_sst_monthly_globe_relax.box',
>  climsssfile        = 'woa13_sss_monthly_globe_relax.box',
>  precipfile         = 'era5_prate_2002-2005_hourly.box',
>  atempfile          = 'era5_air_2002-2005_hourly.box',
>  aqhfile            = 'era5_shum_2002-2005_hourly.box',
>  swdownfile         = '',
>  swfluxfile         = 'era5_nswrs_2002-2005_hourly.box',
>  lwfluxfile         = '',
>  lwdownfile         = 'era5_dlwrf_2002-2005_hourly.box',
>  uwindfile          = 'era5_uwnd_2002-2005_hourly.box',
>  vwindfile          = 'era5_vwnd_2002-2005_hourly.box',
>  runofffile         = 'run-off.bin_1x1',
> #
>  climsststartdate1  = 20020101,
>  climsststartdate2  = 000000,
>  climsstperiod      = -12,
>  climsssstartdate1  = 20020101,
>  climsssstartdate2  = 000000,
>  climsssperiod      = -12,
>  runoffstartdate1   = 20020101,
>  runoffstartdate2   = 000000,
>  runoffperiod       = -12,
> #
>  precipstartdate1=20020101,
>  precipstartdate2=000000,
>  precipperiod=3600.0,
>  atempstartdate1=20020101,
>  atempstartdate2=000000,
>  atempperiod=3600.0,
>  aqhstartdate1=20020101,
>  aqhstartdate2=000000,
>  aqhperiod=3600.0,
>  swdownstartdate1=20020101,
>  swdownstartdate2=000000,
>  swdownperiod=3600.0,
>  lwfluxstartdate1=20020101,
>  lwfluxstartdate2=000000,
>  lwfluxperiod=3600.0,
>  swfluxstartdate1=20020101,
>  swfluxstartdate2=000000,
>  swfluxperiod=3600.0,
>  lwdownstartdate1=20020101,
>  lwdownstartdate2=000000,
>  lwdownperiod=3600.0,
>  uwindstartdate1=20020101,
>  uwindstartdate2=000000,
>  uwindperiod=3600.0,
>  vwindstartdate1=20020101,
>  vwindstartdate2=000000,
>  vwindperiod=3600.0,
>  hfluxstartdate1=20020101,
>  hfluxstartdate2=000000,
>  hfluxperiod=3600.0,
>  sfluxstartdate1=20020101,
>  sfluxstartdate2=000000,
>  sfluxperiod=3600.0,
>  ustressstartdate1=20020101,
>  ustressstartdate2=000000,
>  ustressperiod=3600.0,
>  vstressstartdate1=20020101,
>  vstressstartdate2=000000,
>  vstressperiod=3600.0,
>  &
> 
>  &EXF_NML_03
>  exf_inscal_precip=1.,
>  exf_offset_atemp=0.0,
>  exf_inscal_runoff  = 3.1710e-08,
>  &
> 
>  &EXF_NML_04
>  precip_lon0        = 95.0D0,
>  precip_lon_inc     = 0.25D0,
>  precip_lat0        = -5.0D0,
>  precip_lat_inc     = 160*0.25D0,
>  precip_nlon        = 160,
>  precip_nlat        = 160,
> #
>  atemp_lon0        = 95.0D0,
>  atemp_lon_inc     = 0.25D0,
>  atemp_lat0        = -5.0D0,
>  atemp_lat_inc     = 160*0.25D0,
>  atemp_nlon        = 160,
>  atemp_nlat        = 160,
> #
>  aqh_lon0        = 95.0D0,
>  aqh_lon_inc     = 0.25D0,
>  aqh_lat0        = -5.0D0,
>  aqh_lat_inc     = 160*0.25D0,
>  aqh_nlon        = 160,
>  aqh_nlat        = 160,
> #
>  swdown_lon0        = 95.0D0,
>  swdown_lon_inc     = 0.25D0,
>  swdown_lat0        = -5.0D0,
>  swdown_lat_inc     = 160*0.25D0,
>  swdown_nlon        = 160,
>  swdown_nlat        = 160,
> #
>  lwflux_lon0        = 95.0D0,
>  lwflux_lon_inc     = 0.25D0,
>  lwflux_lat0        = -5.0D0,
>  lwflux_lat_inc     = 160*0.25D0,
>  lwflux_nlon        = 160,
>  lwflux_nlat        = 160,
> #
>  swflux_lon0        = 95.0D0,
>  swflux_lon_inc     = 0.25D0,
>  swflux_lat0        = -5.0D0,
>  swflux_lat_inc     = 160*0.25D0,
>  swflux_nlon        = 160,
>  swflux_nlat        = 160,
> #
>  lwdown_lon0        = 95.0D0,
>  lwdown_lon_inc     = 0.25D0,
>  lwdown_lat0        = -5.0D0,
>  lwdown_lat_inc     = 160*0.25D0,
>  lwdown_nlon        = 160,
>  lwdown_nlat        = 160,
> #
>  uwind_lon0        = 95.0D0,
>  uwind_lon_inc     = 0.25D0,
>  uwind_lat0        = -5.0D0,
>  uwind_lat_inc     = 160*0.25D0,
>  uwind_nlon        = 160,
>  uwind_nlat        = 160,
> #
>  vwind_lon0        = 95.0D0,
>  vwind_lon_inc     = 0.25D0,
>  vwind_lat0        = -5.0D0,
>  vwind_lat_inc     = 160*0.25D0,
>  vwind_nlon        = 160,
>  vwind_nlat        = 160,
> #
>  ustress_lon0        = 95.0D0,
>  ustress_lon_inc     = 0.25D0,
>  ustress_lat0        = -5.0D0,
>  ustress_lat_inc     = 160*0.25D0,
>  ustress_nlon        = 160,
>  ustress_nlat        = 160,
> #
>  vstress_lon0        = 95.0D0,
>  vstress_lon_inc     = 0.25D0,
>  vstress_lat0        = -5.0D0,
>  vstress_lat_inc     = 160*0.25D0,
>  vstress_nlon        = 160,
>  vstress_nlat        = 160,
> #
>  hflux_lon0        = 95.0D0,
>  hflux_lon_inc     = 0.25D0,
>  hflux_lat0        = -5.0D0,
>  hflux_lat_inc     = 160*0.25D0,
>  hflux_nlon        = 160,
>  hflux_nlat        = 160,
> #
>  sflux_lon0        = 95.0D0,
>  sflux_lon_inc     = 0.25D0,
>  sflux_lat0        = -5.0D0,
>  sflux_lat_inc     = 160*0.25D0,
>  sflux_nlon        = 160,
>  sflux_nlat        = 160,
> #
>  runoff_lon0        = 0.50D0,
>  runoff_lon_inc     = 1.0D0,
>  runoff_lat0        = -79.5D0,
>  runoff_lat_inc     = 159*1.0D0,
>  runoff_nlon        = 360,
>  runoff_nlat        = 160,
> #
>  climsst_lon0    = -179.875D0,
>  climsst_lon_inc = 0.25D0,
>  climsst_lat0    = -89.875D0,
>  climsst_lat_inc = 719*0.25D0,
>  climsst_nlon    = 1440,
>  climsst_nlat    = 720,
> #
>  climsss_lon0    = -179.875D0,
>  climsss_lon_inc = 0.25D0,
>  climsss_lat0    = -89.875D0,
>  climsss_lat_inc = 719*0.25D0,
>  climsss_nlon    = 1440,
>  climsss_nlat    = 720,
> #
>  &
> 
>  &EXF_NML_OBCS
>  obcsNstartdate1   = 20020101,
>  obcsNstartdate2   = 000000,
>  obcsNperiod       = 2628000.0,
>  obcsEstartdate1   = 20020101,
>  obcsEstartdate2   = 000000,
>  obcsEperiod       = 2628000.0,
>  obcsSstartdate1   = 20020101,
>  obcsSstartdate2   = 000000,
>  obcsSperiod       = 2628000.,
>  &
> 
> ________________________________
> ???: MITgcm-support <mitgcm-support-bounces at mitgcm.org<mailto:mitgcm-support-bounces at mitgcm.org>> ?? Matthew Mazloff <mmazloff at ucsd.edu<mailto:mmazloff at ucsd.edu>>
> ????: 2020?3?16? 0:44
> ???: mitgcm-support at mitgcm.org<mailto:mitgcm-support at mitgcm.org> <mitgcm-support at mitgcm.org<mailto:mitgcm-support at mitgcm.org>>
> ??: Re: [MITgcm-support] ??: The obvious difference between ERA5 and NCEP-R1 forcing
> 
> Hi Mike
> 
> It is possible it could give worse results, but very unlikely. However its too hard for me to diagnose what is going on. There are many variables to your problem.
> 
> For ERA5 I have this in my data.exf:
>  &EXF_NML_03
>  exf_offset_atemp   = 273.15,
>  exf_inscal_swdown  = -1.0,
>  exf_inscal_lwdown  = -1.0,
> 
> Not sure how to help you,
> Matt
> 
> 
> 
> On Mar 15, 2020, at 5:41 AM, Leming Van <ifanliming at outlook.com<mailto:ifanliming at outlook.com>> wrote:
> 
> Hi, everyone
> 
> Recently I tried to change forcing dataset from NCEP-R1(6-hourly) to ERA5(hourly), but the results of them look so different. I compared the results of NCEP-R1 with the reanalysis data of HYCOM, and these two data look similar.
> 
> Did I pick the wrong variables from ERA5? Or does this mean that higher temporal and spatial resolution atmospheric forcing ERA5 results in worse simulation results than lower resolution NCEP-R1?
> 
> I put the results at here, https://1drv.ms/u/s!AoS5GLJhmvDtjB5Ovnz63FidKeMo?e=c2hS7z
> Suggestions are welcome.
> 
> 
> -Mike
> 
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