NHF from NCEP Reanalysis data

[deba]

hi all.
I need to compute net heat flux (NHF) using NCEP reanalysis data.
I am using net longwave radiation flux (NLWRF), net shortwave radiation flux (NSWRF), net sensible heat flux (NSHF) and net latent heat flux (NHLF) and the following formula NHF = NSWRF - (NLWF + NSHF + NHLF).
Is this formula correct?
There is some problem with the sign convention of NCEP data too.
Should i first multiply all the paras. by (-1) and the use NHF = NSWRF + NLWF + NSHF + NHLF, directly as obtained from NCEP, else how do i proceed with this.
Can anyone familiar with NCEP data help me out.

regards,
deba

[yaswant]

hi all.
I need to compute net heat flux (NHF) using NCEP reanalysis data.
I am using net longwave radiation flux (NLWRF), net shortwave radiation flux (NSWRF), net sensible heat flux (NSHF) and net latent heat flux (NHLF) and the following formula NHF = NSWRF - (NLWF + NSHF + NHLF).
Is this formula correct?
There is some problem with the sign convention of NCEP data too.
Should i first multiply all the paras. by (-1) and the use NHF = NSWRF + NLWF + NSHF + NHLF, directly as obtained from NCEP, else how do i proceed with this.
Can anyone familiar with NCEP data help me out.

regards,
debaDeba, Sometimes back I enquired why NCEP nswrf are negative! I did not get any reply from NCEP support. There is not enough information on the CDC web regarding how each variables were estimated... If you presume the sign (+/-) is the only issue, better cross-check with mean climatology (check IRI website for other products) for your area of interest.

[deba]

Thank You Mr. Yashwant.

I will try that and hope the problem will be solved.
Thanks once again.

cheers,
deba

[vinu]

Hi Deba

I think, the algorithm NH = SW - (LW + LH + SH) will give
the net heat flux, provided, the SW is directed 'downward' and
all others are 'upward'. Now, if the SW data has already been
applied a negative index (as NCEP provides),
it virtually implies that the direction is taken
into account, and the negative sign in the above algorithm is not
needed anymore. In this case, if NH results a negative value, that implies
Ocean gains the heat. Likewise a positive NH implies Ocean lose
the heat.

For oceanographic purpose, NH is refereed as positive when ocean
gains the heat. So if necessary, it is only a matter of changing the
sign of NH.

As Yaswant pointed out, the Columbia
http://ingrid.ldeo.columbia.edu/SOURCES/
data server provides other heat flux data's. Example,
Southampton Oceanography Centre data are given with
specified sign. So, please cross check the NCEP calculations with
this.



-Thanks
-

[deba]

thanks a lot Vinu,

i will look into what u have suggested.
hopefully that would solve the problem.

cheers
deba