info reqd. precipitation information from salinity data

[deba]

Hi all,
i wish to know if theres a way to get precipitation information from salinity data.
any information in this regard is most welcome

[vinu]

Hi Deba,

Can you please explain , Why do you intended to find Precipitation from Salinity ?
I am sorry if this question seems unnecessary.

1. If you are intended to carry out a Precipitation analysis, you can depend
directly on Precipitation data. CMAP provides 2.5 degree (i think so) global
preicipitaion, by associating available rain gage observation
with satellite ones, as well as model results. Also, precipitation are available
from NCEP/NCAR, ECMWF ...(refer our Data Analysis section).

2. Now, if your intention is to estimate the precipitation as
salt flux (we may call it as fresh water flux) for any modeling purpose,
we can estimate this for the model from the climatological
salinity data. This is not so unrealistic, because, the climatology salinity (as we
observe in the ocean) include the effect of precipitation. Thus, inspite of
prescribing the precipitaiton itslef, we can relax the surface salinity of
the model to a pre-defined Salinity data. (i am not including any condition
of relaxation methods here).

3. Now, (though it is just opposite to your question), i am adding an information
here, there are algorithms to develop Salinity data from Satellite OLR
(Outgoing Longwave Radiation) observations. Dr. V.S.N. Murty (NIO, Goa) and his
team had worked over this and published in G.J.R.(oceans 2004/5).


Thanks

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[vinu]

Dear Mr. Vinu.
Thanks for the reply.

well the question u asked is quite logical. let me answer that in short. I am undertaking a R & D feasibility. study on the same. The question to be dealt with: is it possible to forecast ppt from change in the salinity, given salinity observations over a period. i.e. can we establish some sort of a trend out of the relation.

1. thats a very helpful info.

2. that gives me hope. is it possible to suggest some models and where can i get them (i am still a beginner in this field)

3. yeah i have gone thro the same, but as u said it is just opposite to what i am in need of

cheers,

deba

Hi Deba,

The proposed project in which you are involved in is an interesting theme and also a useful research component.

With the prescribed salinity observations, it might be possible to 'hindcaste' or 'nowcaste' the precipitation. The insitu salinity over the ocean is 'shaken', mainly by (1) Evaporation, (2) Precipitaition (3) Vertical Mixing and (4) the horizontal advection (that means the water visiting/departing into/from your area of consideration. Or, if we put these in a proper balance, it would be,

Evolution of Salinity + Advection + Mixing = Evap. - Precip.

This is the usual way of modeling the Salinity, provided the 'Forcing' is the R.H.S of the above equation. The first term in the L.H.S and the two terms in the R.H.S are the time-dependent and others are state dependent. Now, if we do an inversion of the above equation, (i.e. Evap-Pricip. is taken to the L.H.S and Evolution is Salinity is pushed to the R.H.S, ) and do a 'Back-ward' integration, certainly you should reach the Preicipitation, provided you are equipped with correct estimation of Advection, Mixing and Evaporation. You can not integrate this new set of equation Forward, because, the sate of the Atmosphere (the so called Precipitation in your excersice) is not determined by the insitue condition of the Ocean. This is my personnel opinion only. Im not sure, wheather this is a realistic method or a feasible model either. Also this is not a "Pricipitation forecast".

A a coupled ocean-atmosphere boundary layer model will be a more realistic approach. Also, you have to dig, wheather a "forecast is being done for preicipitation" in a coupled ocean-atmosphere model. In such a model, the sate of the atmospher is prescribing from the ocean and at the same time the state of the ocean is prescribing from the atmosphere.

You can seek better advice from Prof. Debasis Sengupta (IISc, Bangalore) (dsen#caos.iisc.ernet.in). Also, it woule be helpful, if you discuss with Bulusu Subrahmanyan, FSU, Florida, (sub#caops.fsu.edu).


-Thanks

The above contents are taken from a couple of discussion about the
topoic 'Precipitation from salinity data'. I hope, more insights on this
topic will be adding by others too.

Thanks

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