[Ncep.list.emc.monsoondesk] Regarding the Snow-Rain conversion in CFS

[Shrinivas Moorthi]

On 10/20/2014 08:16 AM, Prajeesh A.G. wrote:
> Yes sir,
>
> I got your point.
>
> However, my concern is again about the heat flux. Because, as I 
> mentioned, the snw_cc goes to Ocean model and there it takes heat from 
> the ocean surface to melt this amount of snow. So, if there is snow 
> fall over the ocean, the ocean looses heat (cools the ocean) and in 
> reality this heat lost by the ocean should have been gained by the 
> atmosphere in terms of latent heat release. But this release of latent 
> heat is missing.
Again, the latent heating related to condensation is done in either 
microphysics or convection.  there is no need to double count. However, 
as I wrote before, the approach to identify snow fall in CFS is 
simplistic; could have been done in a better
way.  It would have been better if moist physics had identified what is 
snow and what is rain; in the next version of the model we will try to 
do better.
Moorthi
>
> (From a quick look of the Noah land model, I guess similar process is 
> also been done in the land surface too.)
>
> *Regards..*
>
> Prajeesh A G
>
>
>
> ------------------------------------------------------------------------
> Prajeesh,
>     Admittedly, it is a simple scheme to identify whether the rainfall 
> is snow or water based on T850.
> However, this is not a conversion; it is just an identification.  
> Latent heat is considered in the microphysics.
> More advanced microphysics will provide rain and snow rates directly.
> I hope this helps.
> Regards,
> Moorthi
> On 10/20/2014 05:45 AM, Prajeesh A.G. wrote:
>
>
>     I have a doubt regarding the snow-rain conversion in CFS.
>     In the model, the total precipitation is considered as snow fall
>     if the temperature at 850hpa is below 0C.
>
>     See the below code from gbphys_v.f
>
>     !  --- ...  lu: snow-rain detection is performed in land/sice module
>     !           factor=weighted mean tep.
>
>            do i = 1, im
>              tprcp(i) = rain(i)               ! clu: rain -> tprcp
>              srflag(i) = 0.0                  ! clu: default srflag as 'rain'
>              if ( t850(i) <= 273.16 ) then
>                srflag(i) = 1.0                ! clu: set srflag to 'snow'
>
>         ...................
>
>            do i = 1, im
>     !       if ( t850(i)<=273.16 .and. slmsk(i)/=0.0 ) then
>              if ( t850(i) <= 273.16 ) then
>                lprec_cc(i) = 0.0
>                snw_cc(i) = rain(i)
>              else
>                lprec_cc(i) = rain(i)
>                snw_cc(i) = 0.0
>              endif
>            enddo
>
>
>     Here the 'srflag' is used in the sfc_drv (Land model) to detect
>     whether the falling precipitation is snow or not. Similarly snw_cc
>     goes to ocean model.
>
>     My doubt is, where is the latent heat of fusion released during
>     this conversion?
>
>     *Regards..*
>
>     Prajeesh A G
>
>
>
> -- 
> Dr. Shrinivas Moorthi
> Research Meteorologist
> Global Climate and Weather Modeling Branch
> Environmental Modeling Center / National Centers for Environmental Prediction
> 5830 University Research Court - (W/NP23), College Park MD 20740 USA
> Tel:(301)683-3718


-- 
Dr. Shrinivas Moorthi
Research Meteorologist
Global Climate and Weather Modeling Branch
Environmental Modeling Center / National Centers for Environmental Prediction
5830 University Research Court - (W/NP23), College Park MD 20740 USA
Tel:(301)683-3718

-------------- next part --------------
An HTML attachment was scrubbed...
URL: https://lstsrv.ncep.noaa.gov/pipermail/ncep.list.emc.monsoondesk/attachments/20141020/1d7c432a/attachment-0001.html