Adding Wet Deposition
The formulationn used in UKCA is described in Giannakopoulos (1999)[1]. This scheme uses the following formula to calculate the effective Henry's Law coefficient
where is the rate constant at 298K.
References
- Giannakopoulos, C., M. P. Chipperfield, K. S. Law, and J. A. Pyle (1999), Validation and intercomparison of wet and dry deposition schemes using 210Pb in a global three-dimensional off-line chemical transport model, J. Geophys. Res., 104(D19), 23761–23784, doi:10.1029/1999JD900392.
Henry's Law Specification Definition
Chemistry Scheme Specification
Within the UKCA code, whether a species is wet deposited or not is controlled in the ukca_chem_scheme.F90 file. In the chch_defs_scheme array there are lines like
chch_t( 10,'HONO2 ', 1,'TR ',' ', 1, 1, 0), & ! 10 DD: 7,WD: 4, chch_t( 11,'H2O2 ', 1,'TR ',' ', 1, 1, 0), & ! 11 DD: 8,WD: 5,
Where the 1 in the 7th column turns on wet deposition of that species (being 0 otherwise). You will need to change the 0 to a 1 for the species that you wish to now wet deposit.
Setting Henry's Law values
In the ukca_chem_scheme.F90 the parameters required to calculate are held in the henry_defs_scheme array, and has format
for the 1st dissociatation | for the 1st dissociatation | for the 2nd dissociatation | for the 2nd dissociatation |
Columns 3 and 4 are used if the species dissociates in the aqueous phase. In this case, is futher multiplied by a factor of
where
In this case, columns 3 and 4 contain the values of and used in the above formula. Similarly, if the dissasociates a second time then a further factor of , where is calculated from the values of and in columns 5 and 6.
'Note: As with the 2D dry deposition values in depvel_defs_scheme, the order of henry_defs_scheme also assumes that the values are in the same order as the species (that wet deposit) in the chch_defs_scheme array.
! The following formula is used to calculate the effective Henry's Law coef, ! which takes the affects of dissociation and complex formation on a species' ! solubility (see Giannakopoulos, 1998) ! ! H(eff) = K(298)exp{[-deltaH/R]x[(1/T)-(1/298)]} ! ! The data in columns 1 and 2 above give the data for this gas-aqueous transfer, ! Column 1 = K(298) [M/atm] ! Column 2 = -deltaH/R [K-1] ! ! If the species dissociates in the aqueous phase the above term is multiplied by ! another factor of 1+{K(aq)/[H+]}, where ! K(aq) = K(298)exp{[-deltaH/R]x[(1/T)-(1/298)]} ! The data in columns 3 and 4 give the data for this aqueous-phase dissociation, ! Column 3 = K(298) [M] ! Column 4 = -deltaH/R [K-1] ! The data in columns 5 and 6 give the data for a second dissociation, ! e.g for SO2, HSO3^{-}, and SO3^{2-} ! Column 5 = K(298) [M] ! Column 6 = -deltaH/R [K-1]
Written by Luke Abraham 2013