Inquiry Regarding HYCOM Data for Yellow Sea Research

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Jan 4, 2024, 7:32:50 AMJan 4
Dear HYCOM operation Team,

I hope this message finds you well. My name is Ji-uk Hwang, and I am currently engaged in research on the 'Yellow Sea' utilizing HYCOM data at the Department of Oceanography, Pusan National University, South Korea.

I am reaching out to you regarding the input forcing (surface forcing) data of HYCOM. Specifically, I am interested in obtaining net heat flux data to analyze the water temperature behavior of the Yellow Sea as indicated in the HYCOM output data. As a newcomer to working with HEAT FLUX data in HYCOM, I am uncertain about which specific data to utilize and would greatly appreciate your assistance.

According to the information available on the website, the description of GOFS 3.1: 41-layer HYCOM + NCODA Global 1/12° Reanalysis mentions that "Surface forcing is from 1-hourly National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) and Climate Forecast System Version 2 (CFSv2)."

Among the data related to heat flux, I have identified the following variables:
1. surface_net_downward_radiative_flux
2. surface_net_downward_shortwave_flux
3. surface_downwelling_longwave_flux
4. surface_downwelling_shortwave_flux

However, I am uncertain about the specifics of each of these data. Therefore, I kindly request your guidance on which data I should prioritize for downloading.

Additionally, my research requires data spanning a 30-year period, and I have encountered challenges due to the substantial size of each dataset. I am interested to know if there is a provision to set a spatiotemporal range before initiating the data download process.

I appreciate your time and consideration in addressing these inquiries. Thank you for your assistance.

Wishing you a wonderful day ahead.


Ji-uk Hwang

Alan Wallcraft

Jan 4, 2024, 10:51:04 AMJan 4
to Forum, 2103
For the latest GOFS 3.1 Analysis from Dec-04-2018 to Present we have the net heat flux "qtot" in the "sur" dataset:

However, we don't have this for the GOFS 3.1 Reanalysis.

If monthly means are enough, net heat flux is one of the fields in native grid monthly mean archives at  You would have to extract this with the HYCOM-tools archv2ncdf2d program (say).

HYCOM uses a bulk parameterization, based on model SST and input atmospheric fields, to calculate the latent and sensible heat flux.  So it isn't practical to calculate the GOFS Reanalysis net heat flux from the CFSR and CFSv2 datasets.  The short and long wave are from the "downwelling" CFSR fields, with albedo giving the net shortwave and upwelling longwave from model SST.

We don't have a way to subset CFSR for download, but it isn't going to be much use to you in any case.

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