understanding of solar_source, diurnal_srflx,atm_press etc.

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mashinde
Posts: 135
Joined: Mon Jun 22, 2009 3:46 pm
Location: Indian Institute of Tropical Meteorology, Pune, INDIA

understanding of solar_source, diurnal_srflx,atm_press etc.

#1 Unread post by mashinde »

Hi all,

I am confused with following keys in cppdefs.h and it's physical role in ROMS. Also the possible good combination of them.
solar_source, diurnal_srflx and atm_press. And what will be right choice of it for 6 hourly forcings.

currently, i am using for 6 hrly forcings.

#define BULK_FLUXES
#if defined BULK_FLUXES
#define LONGWAVE_OUT
#define EMINUSP
#define SOLAR_SOURCE
#endif

#undef DIURNAL_SRFLUX

can anybody tell about this and also what keys are good option.

thanks

carlosag
Posts: 20
Joined: Thu Sep 30, 2021 12:08 pm
Location: University of Iceland

Re: understanding of solar_source, diurnal_srflx,atm_press etc.

#2 Unread post by carlosag »

Hi there Mashinde,
I am also confused about this. Did you manage to solve it? Can you please suggest me some place to read up?
Thank you

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wilkin
Posts: 755
Joined: Mon Apr 28, 2003 5:44 pm
Location: Rutgers University
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Re: understanding of solar_source, diurnal_srflx,atm_press etc.

#3 Unread post by wilkin »

#define BULK_FLUXES uses the COARE3.0 algorithm of Fairall et al. (references are in the code bulk_flux.F) to compute air-sea heat and momentum flux (stress) on the basis of input marine atmospheric boundary layer conditions (air temp, wind etc.)

#define LONGWAVE_OUT computes the outgoing longwave radiation on the basis of ROMS SST. ROMS needs to read the downward longwave radiation from the atmosphere as an input (variable lwrad_down). If this is not defined then ROMS needs to reads net longwave radiation from variable lwrad.

#define EMINUSP computes evaporation from the latent heat flux and subtracts the user provided precipitation to get E-P. This is converted to an equivalent salt flux and imposed as a boundary conditions on vertical mixing of salinity.

#define SOLAR_SOURCE causes the net solar shortwave radiation (variable swrad) to penetrate into several vertical layers according to the water clarity specified with a Jerlov Water type (roms.in input variable WTYPE). If this is not defined, the solar radiation is all absorbed in the top most cell of the model.

#define DIURNAL_SRFLUX can be used if you don't have very well time resolved shortwave radiation. For example, 6-hourly instantaneous swrad very poorly resolves the diurnal cycle, but if those data are converted to daily averages, then DIURNAL_SRFLUX will read the daily value and distribute this over an idealized diurnal cycle (appropriate to latitude, longtide and day-of-year) so that peak heating occurs at the true solar noon, and there is no heating overnight. The user must pre-process the data to daily or longer time scale averages for this to work. DO NOT use this option with swrad given more frequently than once per day - that causes overestimation of the true heating.
John Wilkin: DMCS Rutgers University
71 Dudley Rd, New Brunswick, NJ 08901-8521, USA. ph: 609-630-0559 jwilkin@rutgers.edu

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