affect by Uwind and Vwind

[wjlee]

Hello! everyone.!

I think ROMS is affected by Uwind and Vwind alot in shallow depth of water.
How about your think ?
and
I'd like to know methods to reduce effects of those valuables.

sincerely thank you.!!

[kate]

You think the effect of winds is too strong? How are you obtaining wind stress from wind? It is known that the BULK_FLUXES stress algorithm is too strong in the case of high winds, also it doesn't account for the currents (it is a function of winds only, not of winds-currents).

This is your 2-D case? You might try out a stronger bottom drag where it gets shallow.

[wjlee]

Hello! Thank you for your reply

I run 3-D ROMS. I calculate wind stress by using the BULK_FLUXES in the ROMS.
I set 2 models. One of the models is Pair, Uwind, Vwind and tides(TPXO6) as input. and the other is tides(TPXO6) only as input.
There is no diffrence between 2 models except for the inputs.
I run the 2 models respectively and substract zeta of one model from zeta of the oher model. so I got the differences. Its values were reasonalbe in the most of regions but values in shallow depth of water were very big.
so I just doubt the inputs. but I don't know what to do now.

How about your think ?

Please let me know.
thank you.

[LuoZhengpu]

You think the effect of winds is too strong? How are you obtaining wind stress from wind? It is known that the BULK_FLUXES stress algorithm is too strong in the case of high winds, also it doesn't account for the currents (it is a function of winds only, not of winds-currents).

This is your 2-D case? You might try out a stronger bottom drag where it gets shallow.

Hello Kate,
Could you please give me some more detailed information about performance of BULK_FLUXS at high wind speeds?
Nowadays I'm making 17 years hindcast with ROMS with time step of 60s and resolution of 8km. However, it blows up in the third model year which may have been due to extreme winds. So I wanna ask if there is a maximum acceptable wind speed for ROMS when BULK_FLUXS is defined? And How should I modify the high winds?
Thanks!
Zhengpu Luo

[kate]

What winds are you using? I have heard that ERA5 can get unphysically large.

Since I wrote that prior message I switched to a Large and Yeager bulk flux scheme, then I changed ocean models.

[wilkin]

Note that there was a code update 6 weeks ago to introduce COARE3.5 bulk fluxes:
https://www.myroms.org/projects/src/ticket/970
The changes from 3.0 to 3.5 make the algorithm more appropriate at higher wind speeds.

If your issue is arising in shallow water you might need to limit the bottom stress #define LIMIT_BSTRESS
https://www.myroms.org/projects/src/ticket/569
See the post by John Warner about this
https://www.myroms.org/forum/viewtopic. ... ress#p9477

[LuoZhengpu]

What winds are you using? I have heard that ERA5 can get unphysically large.

Since I wrote that prior message I switched to a Large and Yeager bulk flux scheme, then I changed ocean models.

Hi Kate!
I use CFSR as bulk forcing and HYCOM as boundary condition, which were all downloaded from HYCOM website. That's because HYCOM reanalysis data can simulate the inter-annual variations I focus on between 2004~2020 well. It can't be stable with hourly or 12 hourly winds in extrreme events. Now daily winds are used to drive model, and it works.

[LuoZhengpu]

Note that there was a code update 6 weeks ago to introduce COARE3.5 bulk fluxes:
https://www.myroms.org/projects/src/ticket/970
The changes from 3.0 to 3.5 make the algorithm more appropriate at higher wind speeds.

If your issue is arising in shallow water you might need to limit the bottom stress #define LIMIT_BSTRESS
https://www.myroms.org/projects/src/ticket/569
See the post by John Warner about this
https://www.myroms.org/forum/viewtopic. ... ress#p9477

Hi Wilkin,
Thank you for the information!
I have updated the bulk_flux.F and now I'm testing the hourly winds.
Hope it useful!