[MITgcm-support] 回复: 回复: 转发: The obvious difference between ERA5 and NCEP-R1 forcing
Stanislav Martyanov
martyanov.sd at gmail.com
Tue Mar 17 03:59:47 EDT 2020
Hello, Mike!
>>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?
Oh, yes, it was a misprint - I looked in the another file... Of course, the
ERA5 meteorological forcing was taken from
https://cds.climate.copernicus.eu/, while the open boundary conditions for
the ocean model - from the GLOBAL_REANALYSIS_PHY_001_030.
By the way, concerning ERA5 units, some care should be taken. I'm sure you
know all of this, as you have already posted, but for the users new to ERA5
reanalysis dataset some details might be useful:
The ERA5's field 'Mean total precipitation rate' is in [kg m-2 s-1], and
dividing it by 1000 kg m-3 makes the field suitable for the MITgcm's EXF
package, while ERA5's 'Total precipitation' is in [m]. Also, 'Mean surface
downward long-wave and short-wave radiation fluxes' are in [W m-2], while
'Surface solar and thermal radiation downwards' is in [J m-2]. The
difference is the multiplier related to the time period between
adjacent model records. So, information presented in the Overview table at
the ERA5 page should be carefully read. It is not only about units, but
also about the ERA5's convention for vertical fluxes' direction.
I hope you will figure out the couse of difference in your results. Please,
let us know when you succeed, the topic is interesting and important indeed.
Regards,
Stanislav
вт, 17 мар. 2020 г. в 08:58, Leming Van <ifanliming at outlook.com>:
> 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
> ------------------------------
> *发件人:* MITgcm-support <mitgcm-support-bounces at mitgcm.org> 代表 Raphael
> Dussin <raphael.dussin at gmail.com>
> *发送时间:* 2020年3月16日 20:24
> *收件人:* mitgcm-support at mitgcm.org <mitgcm-support at mitgcm.org>
> *主题:* Re: [MITgcm-support] 回复: 转发: 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 à 04:49, Stanislav Martyanov <martyanov.sd at gmail.com>
> a écrit :
>
> 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
>
>
> пн, 16 мар. 2020 г. в 09:27, Leming Van <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
>
> 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.,
> &
>
> ------------------------------
> *发件人:* MITgcm-support <mitgcm-support-bounces at mitgcm.org> 代表 Matthew
> Mazloff <mmazloff at ucsd.edu>
> *发送时间:* 2020年3月16日 0:44
> *收件人:* mitgcm-support at mitgcm.org <mitgcm-support at mitgcm.org>
> *主题:* Re: [MITgcm-support] 转发: 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> 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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