Changes between Version 8 and Version 9 of user/clem/Heat_Flux_air-ice-ocean_interface

Timestamp:

2016-05-19T13:10:42+02:00 (8 years ago)

Author:

clem

Comment:

--

user/clem/Heat_Flux_air-ice-ocean_interface

@@ -4 +4 @@
 It is time to approach the matter from a different angle. I describe below what we are doing in NEMO and what we think the solution should be, and you can comment on that.[[BR]]
 
-So far, the total non-solar flux (Qns) is imposed by the atmosphere but it excludes (from what I understand) the heat contents of snow precipitation (Qsnow) and rain (Qrain). It also does not take into account the heat content (if any) of evaporated ice and water (Qevap, already in vapor form) that the atmosphere should receive. The total non-solar (conservative) flux should thus be written:[[BR]]
+So far, the total non-solar flux (Qns) is imposed by the atmosphere but it excludes (from what I understand) the heat contents of snow precipitation (Qsnow) and rain (Qrain). It also does not take into account the heat content (if any) of evaporated ice and water (Qevap, already in vapor form) that the atmosphere should receive. The total non-solar (conservative) flux should thus be written (including the snow melting when it reaches the ocean):[[BR]]
 
-{{{Qns_tot = Qns + Qsnow + Qrain + Qevap}}}
+{{{Qns_tot = Qns + Qsnow + Qrain + Qevap + "Snow-melt-in-ocean"}}}
 
 
@@ -13 +13 @@
 >>''C Rousset'': I agree but I do not think we have access to ice surface temperature at this stage (not sure though)?
 
-{{{Qsnow = sprecip * ice_frac * ( Cp * SST - Lfus ) [in W/m2]}}}
+{{{Qsnow = sprecip * ( Cp * SST ) [in W/m2]}}}
 
 {{{Qrain = lprecip * Cp * SST}}}
@@ -20 +20 @@
 
 {{{Qevap (ice)   = 0}}}
+
+{{{"Snow-melt-in-ocean" = sprecip * ice_frac * ( - Lfus )}}}
 
 with sprecip = snow precip, lprecip = liquid precip, ice_frac = ice fraction, Cp = specific heat of sea water, Lfus = Latent heat of fusion of pure ice at 0deg, SST = sea surface temperature.[[BR]]
@@ -35 +37 @@
 1) The atmosphere considers all these fluxes to be 0, that’s ok but
 NEMO needs to know
-and we will have to trick the calculation of snow temperature in LIM3 since it is recalculated from Qsnow (see nota bene). You can see that as NEMO business but it is important you know it has consequences on sea ice thermodynamics.[[BR]]
+and we will have to trick the calculation of snow temperature in LIM3 since it is recalculated from Qsnow and Lfus (see nota bene). You can see that as NEMO business but it is important you know it has consequences on sea ice thermodynamics.[[BR]]
 >''O Marti'': Not exactly. The flux from atmosphere is not 0. But atmosphere doesn't need to compute it. You could diagnose the actual flux by computing the total ATM enthalpy before and after the rains leaves ATM.
 
-2) The atmosphere (you, from your atmospheric models) provides non-zero fluxes and then it is better if NEMO knows how Qsnow is calculated in the atmosphere, which Cp, temperature and Lfus is used (see why below).
+2) The atmosphere (you, from your atmospheric models) provides non-zero fluxes and then it is better if NEMO knows how Qsnow is calculated in the atmosphere, which Cp, temperature and also Lfus is used (see why below).
 
 
 **Nota bene**[[BR]]
-The most important flux here (by far) is Qsnow. When snow falls on ice, its heat content adds up with the pre-existing snow to give a total heat content equal to q and snow temperature is recalculated with this expression:[[BR]]
+The most important flux here (by far) is Qsnow. When snow falls on ice, its enthalpy adds up with the pre-existing snow to give a total enthalpy equal to q and snow temperature is recalculated with this expression:[[BR]]
 {{{q =  rho(snow) * ( Cp(snow) * T(snow) - Lfus ) [in J/m3]}}}[[BR]]
-Therefore a large difference between the expressions of Qsnow and q would lead to erroneous snow temperatures. One consequence could be a snow that always melts because its temperature is always positive. The largest difference between Qsnow and q is certainly Lfus which may differ greatly between the atmospheric model and LIM3. [[BR]]
+Therefore a large difference between the expressions of (Qsnow - sprecip*Lfus) and q would lead to erroneous snow temperatures. One consequence could be a snow that always melts because its temperature is always positive. The largest difference is certainly Lfus which may differ greatly between the atmospheric model and LIM3. [[BR]]
 
-At this point I expect to receive from you the Qsnow, Qevap and Qrain (whether you think it should be zero or a value defined by your atmospheric model calculations). If you do not think this is needed please send me comments based on the above equations so that we can move on in a constructive way.
+At this point I expect to receive from you the Qsnow, Qevap(ocean & ice) and Qrain (whether you think it should be zero or a value defined by your atmospheric model calculations). If you do not think this is needed please send me comments based on the above equations so that we can move on in a constructive way.
 
 == LIM3 physical constants ==
 Heat capacity (ice/snow) = 2067
 
-Heat capacity (sea water) = 3991.867957
+Heat capacity (sea water) = 3991.86795711963
 
 Latent heat of fusion at 0deg (Lfus) = 334,000 J/kg