Changes between Version 2 and Version 3 of user/clem/Heat_Flux_air-ice-ocean_interface

Timestamp:

2016-04-15T16:31:48+02:00 (8 years ago)

Author:

omamce

Comment:

--

user/clem/Heat_Flux_air-ice-ocean_interface

@@ -8 +8 @@
 {{{Qns_tot = Qns + Qsnow + Qrain + Qevap}}}
 
-with Qns being the non-solar flux provided by the atmosphere.[[BR]]
+with {{{Qns}}} being the non-solar flux provided by the atmosphere.[[BR]]
 
 Therefore NEMO did a guess on Qsnow, Qrain and Qevap by considering the temperature of falling snow, rain and evaporated water = SST, and temperature of evaporated ice = 0°C. Then,[[BR]]
+(''O Marti'' : when it's snowing on sea ice, using the surface temperature (snow/ice) would be a better first guess. But the actual flux from ATM is still needed to be conservative)
 
 {{{Qsnow = sprecip * ice_frac * ( Cp * SST - Lfus ) [in W/m2]}}}
@@ -21 +22 @@
 
 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]]
-A Voldoire : Concerning {{{Qrain = lprecip * Cp * SST}}} It means that you consider that liquid precipitation temperature is zero and you calculate the energy given to the ocean by changing the temperature from zero to SST? Am I wrong?
+''A Voldoire'' : Concerning {{{Qrain = lprecip * Cp * SST}}} It means that you consider that liquid precipitation temperature is zero and you calculate the energy given to the ocean by changing the temperature from zero to SST? Am I wrong?
+''O Marti''. The temperature is not 0. But NEMO doesn't know at which temperature the precips are leaving the ATM realm to enter the OCE realm, and should make a guess.
+
 
 **In order to be really conservative, the atmosphere should provide those fluxes**, or am I completely wrong here?
+O Marti : OK with that. When its rains, some matter is leaving the ATM realm, and an energy is associated with it and given to the OCE realm. 
 
 == What is the solution? ==
@@ -30 +34 @@
 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.
+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]]
+''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 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).
@@ -38 +43 @@
 The most important flux here (by far) is Qsnow. When snow falls on ice, its heat content adds up with the pre-existing snow 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. 
+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]]
+
 
 == LIM3 physical constants ==
@@ -55 +61 @@
 
 Latent heat of sublimation at 0deg   = 2,834,500 J/kg
-