Changeset 7712

Timestamp:

2017-02-22T12:26:36+01:00 (7 years ago)

Author:

dford

Message:

Update comment relating to pCO2 to fCO2 conversion.

File:

• branches/UKMO/dev_r4650_general_vert_coord_obsoper_surf_bgc/NEMOGCM/NEMO/OPA_SRC/OBS/diaobs.F90 (modified) (1 diff)

branches/UKMO/dev_r4650_general_vert_coord_obsoper_surf_bgc/NEMOGCM/NEMO/OPA_SRC/OBS/diaobs.F90

@@ -1681 +1681 @@
          pco2_3d(:,:,:) = fabm_get_bulk_diagnostic_data(model, jp_fabm_o3pc)
          pco2(:,:) = pco2_3d(:,:,1)
-         ! Now, convert pCO2 to fCO2, based on SST in K
-         ! This follows the method used by SOCAT to convert pCO2 to fCO2, see:
-         ! http://www.socat.info/Uniform_format_surface_fCO2_database.pdf
+         ! Now, convert pCO2 to fCO2, based on SST in K. This follows the standard methodology of:
+         ! Pierrot et al. (2009), Recommendations for autonomous underway pCO2 measuring systems
+         ! and data reduction routines, Deep-Sea Research II, 56: 512-522.
+         ! and
+         ! Weiss (1974), Carbon dioxide in water and seawater: the solubility of a non-ideal gas,
+         ! Marine Chemistry, 2: 203-215.
+         ! In the implementation below, atmospheric pressure has been assumed to be 1 atm and so
+         ! not explicitly included - atmospheric pressure is not necessarily available so this is
+         ! the best assumption.
+         ! Further, the (1-xCO2)^2 term has been neglected. This is common practice
+         ! (see e.g. Zeebe and Wolf-Gladrow (2001), CO2 in Seawater: Equilibrium, Kinetics, Isotopes)
+         ! because xCO2 in atm is ~0, and so this term will only affect the result to the 3rd decimal
+         ! place for typical values, and xCO2 would need to be approximated from pCO2 anyway.
          fco2(:,:) = pco2(:,:) * EXP((-1636.75                                                                               + &
             &                         12.0408      * (tsn(:,:,1,jp_tem)+rt0)                                                 - &