[MITgcm-support] unrealistic model results in a regional model

[Martin Losch]

Hi Fanglou,

please share you data.exf. 

Martin

> On 10. Dec 2025, at 15:56, Fanglou Liao <fanglou.liao at unswalumni.com> wrote:
> 
> 
> Dear MITgcm support
> 
> I have a new problem in the temperature simulation, which I guess is associated with my external heat flux forcing. When I used hfluxfile, the temperature value is within the normal range, but a few ℃ lower than it should be. When I used sw, lw, atemp and aqh, then temperature in the coastal area can go down to -20℃ (but the velocity is generally ok, as attached)，which is clearly wrong. My external forcing was downloaded from 3-hrs ERA5 data.
> 
> I checked the diagnostics, found that the latent heat flux is a few times larger than it should be; 
> 
> Any help will be greatly appreciated.
> 
> FL
> 
> # m/s
>  precipfile  = '/mnt/disk_B/user/liaof/MITgcm/verification/NSCS_case_5/input/InputFiles/ERA5_tp_3hrs_1993.bin',
> # W/m2, downward positive
>  swdownfile  =  '/mnt/disk_B/user/liaof/MITgcm/verification/NSCS_case_5/input/InputFiles/ERA5_sw_3hrs_1993.bin',
> # W/m2, downward positive
>  lwdownfile  = '/mnt/disk_B/user/liaof/MITgcm/verification/NSCS_case_5/input/InputFiles/ERA5_lw_3hrs_1993.bin',
> # K
>  atempfile   = '/mnt/disk_B/user/liaof/MITgcm/verification/NSCS_case_5/input/InputFiles/ERA5_t2m_3hrs_1993.bin',
> # kg/kg
>  aqhfile    =   '/mnt/disk_B/user/liaof/MITgcm/verification/NSCS_case_5/input/InputFiles/ERA5_spehum_3hrs_1993.bin',
> # m/s
>  uwindfile  = '/mnt/disk_B/user/liaof/MITgcm/verification/NSCS_case_5/input/InputFiles/ERA5_U10_3hrs_1993.bin',
> # m/s
>  vwindfile   = '/mnt/disk_B/user/liaof/MITgcm/verification/NSCS_case_5/input/InputFiles/ERA5_V10_3hrs_1993.bin',
> 
> 
> From: Fanglou Liao <fanglou.liao at unswalumni.com <mailto:fanglou.liao at unswalumni.com>>
> Sent: Wednesday, December 10, 2025 10:53 PM
> To: MITgcm Support <mitgcm-support at mitgcm.org <mailto:mitgcm-support at mitgcm.org>>
> Subject: Re: [MITgcm-support] unrealistic model results in a regional model
>  
> Dear MITgcm support
> 
> I have a new problem in the temperature simulation, which I guess is associated with my external heat flux forcing. When I used hfluxfile, the temperature value is within the normal range, but a few ℃ lower than it should be. When I used sw, lw, atemp and aqh, then temperature in the coastal area can go down to -20℃ (but the velocity is generally ok, as attached)，which is clearly wrong. My external forcing was downloaded from 3-hrs ERA5 data.
> 
> I checked the diagnostics, found that the latent heat flux is a few times larger than it should be; 
> 
> Any help will be greatly appreciated.
> 
> FL
> 
> # m/s
>  precipfile  = '/mnt/disk_B/user/liaof/MITgcm/verification/NSCS_case_5/input/InputFiles/ERA5_tp_3hrs_1993.bin',
> # W/m2, downward positive
>  swdownfile  =  '/mnt/disk_B/user/liaof/MITgcm/verification/NSCS_case_5/input/InputFiles/ERA5_sw_3hrs_1993.bin',
> # W/m2, downward positive
>  lwdownfile  = '/mnt/disk_B/user/liaof/MITgcm/verification/NSCS_case_5/input/InputFiles/ERA5_lw_3hrs_1993.bin',
> # K
>  atempfile   = '/mnt/disk_B/user/liaof/MITgcm/verification/NSCS_case_5/input/InputFiles/ERA5_t2m_3hrs_1993.bin',
> # kg/kg
>  aqhfile    =   '/mnt/disk_B/user/liaof/MITgcm/verification/NSCS_case_5/input/InputFiles/ERA5_spehum_3hrs_1993.bin',
> # m/s
>  uwindfile  = '/mnt/disk_B/user/liaof/MITgcm/verification/NSCS_case_5/input/InputFiles/ERA5_U10_3hrs_1993.bin',
> # m/s
>  vwindfile   = '/mnt/disk_B/user/liaof/MITgcm/verification/NSCS_case_5/input/InputFiles/ERA5_V10_3hrs_1993.bin',
> From: Matthew Mazloff <mmazloff at ucsd.edu <mailto:mmazloff at ucsd.edu>>
> Sent: Tuesday, December 2, 2025 5:46 AM
> To: Fanglou Liao <fanglou.liao at unswalumni.com <mailto:fanglou.liao at unswalumni.com>>
> Subject: Re: [MITgcm-support] unrealistic model results in a regional model
>  
> Very glad you figured it out
> 
> Matt
> 
> 
>> On Nov 29, 2025, at 4:30 PM, Fanglou Liao <fanglou.liao at unswalumni.com <mailto:fanglou.liao at unswalumni.com>> wrote:
>> 
>> Hi Matt
>> 
>> I've solved the unphysical noisy problem. Thank you very much,
>> 
>> FL 
>>  
>> From: MITgcm-support <mitgcm-support-bounces at mitgcm.org <mailto:mitgcm-support-bounces at mitgcm.org>> on behalf of Fanglou Liao <fanglou.liao at unswalumni.com <mailto:fanglou.liao at unswalumni.com>>
>> Sent: Wednesday, November 26, 2025 5:10 PM
>> To: mitgcm-support at mitgcm.org <mailto:mitgcm-support at mitgcm.org> <mitgcm-support at mitgcm.org <mailto:mitgcm-support at mitgcm.org>>
>> Subject: Re: [MITgcm-support] unrealistic model results in a regional model
>>  
>> Hi Matt
>> 
>> Thank you so much for your response. I've tried your advices, and found that  U, V boundary conditions caused the noisy patterns and leading to unphysical results. Keeping only normal velocity (i.e., v=0 along the east boundary and u=0 along the south one; T, S were kept) at the open boundaries does not solve the problem. I've also tried to "make the bathymetry flat in the normal direction for several (6) grid cells", but the noisy patterns still occured.
>> 
>> restoring sponge time was also tried as suggested.
>> 
>> Best,
>> 
>> FL
>>  
>> From: MITgcm-support <mitgcm-support-bounces at mitgcm.org <mailto:mitgcm-support-bounces at mitgcm.org>> on behalf of Fanglou Liao <fanglou.liao at unswalumni.com <mailto:fanglou.liao at unswalumni.com>>
>> Sent: Tuesday, November 25, 2025 9:38 PM
>> To: MITgcm Support <mitgcm-support at mitgcm.org <mailto:mitgcm-support at mitgcm.org>>
>> Subject: [MITgcm-support] unrealistic model results in a regional model
>>  
>> Dear MITgcm support
>> 
>> I am a new MITgcm user. I am building a regional ocean model with mitgcm, and have some problems with the model results, which I guess are associated with the open boundaries (East and South).  This model is of 0.03 deg, with initial (T, S, U, V) and open boundary conditions are interpolated from CMEMS reanalysis (0.083 deg). The external forcing are from ERA5. The Δt = 45 seconds. The model results are unrealistic, with small-scale patterns appear (attached), and the SST even dropped below 0 after a few days. When I closed the east and south boundaries, these problems disappeard.  Could you please kindly help me check my files attached and give me some advices? 
>> 
>> Thank you very much
>> 
>> FL
>> _______________________________________________
>> MITgcm-support mailing list
>> MITgcm-support at mitgcm.org <mailto:MITgcm-support at mitgcm.org>
>> https://urldefense.com/v3/__http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support__;!!Mih3wA!BRZw72iafAboimuRazxocs1SHCpxcjA1zxc36O9CQuxGphodoc6_TrRRsD-LdnUNNCTpezdlRVSsGVWvk_fTgxK1HoE$
> 
> <T.png><UV.png>_______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org <mailto:MITgcm-support at mitgcm.org>
> http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.mitgcm.org/pipermail/mitgcm-support/attachments/20251210/c97ecee8/attachment-0001.html>