my_code_base.ocean.bgc

Module Contents

my_code_base.ocean.bgc.fugacity(pCO2, p_equ, SST, xCO2=None)[source]

Calculate the fugacity of CO2. Can be done either before or after a temperature_correction(). The formulas follow Dickson et al. [2007], mainly SOP 5, Chapter 8. “Calculation and expression of results”.

\[(fCO_2)^\text{wet}_\text{SST} = (pCO_2)^\text{wet}_\text{SST} \cdot \exp{\Big(p_\text{equ}\cdot\frac{\left[ B(CO_2,SST) + 2\,\left(1-(xCO_2)^\text{wet}_{SST}\right)^2 \, \delta(CO_2,SST)\right]}{R\cdot SST}\Big)}\]

where \(SST\) is the sea surface temperature in K, \(R\) the gas constant and \(B(CO_2,SST)\) and \(\delta(CO_2,SST)\) are the virial coefficients for \(CO_2\) (both in \(\text{cm}^3\,\text{mol}^{-1}\)), which are given as

\[B(CO_2,T) = -1636.75 + 12.0408\,T - 0.0327957\,T^2 + 0.0000316528\,T^3\]

and

\[\delta(CO_2,T) = 57.7 - 0.188\,T\]
Parameters:

  • pCO2 (float or pandas.Series) – The partial pressure of CO2 (in µatm). Make sure you have converted xCO2 concentration (mole fraction in ppm) into partial pressure (in µatm).

  • p_equ (float or pandas.Series) – The measured pressure (in hPa, Pa or atm) at the equilibrator (hint: you might want to smoothen your time series)

  • SST (float or pandas.Series) – The in-situ measurement temperature (in °C or Kelvin)

  • xCO2 (float or pandas.Series (optional)) – CO2 concentration (mole fraction in ppm). If given, the δ_CO2 virial coefficient in the numerator in the exponential expression is multiplied by (1 - xCO2*1e-6). Else, this term is 1.

my_code_base.ocean.bgc.temperature_correction(CO2, T_out=None, T_in=None, method='Takahashi2009', **kwargs)[source]

Apply a temperature correction. This might be necessary when the in-situ temperatures (at the water intake, often outside the ship) differ from where the CO2 measurement is done (often in a ferry-box onboard the ship). The correction used here follows Takahashi et al. [2009]:

\[{(xCO_2)}_{SST} = {(xCO_2)}_{T_\text{equ}} \cdot \exp{\Big(0.0433\cdot(SST - T_\text{equ}) - 4.35\times 10^{-5}\cdot(SST^2 - T_\text{equ}^2)\Big)}\]

for correcting the temperature at the equilibrator \(T_\text{equ}\) to the SST.

CO2 can be one out of [xCO2 (mole fraction), pCO2 (partial pressure), fCO2 (fugacity)].

Parameters:

  • CO2 (float | pandas.Series) – The CO2 variable, which shall be corrected for temperature differences. Can be one out of the following: - xCO2 (mole fraction in ppm) - pCO2 (partial pressure in hPa, Pa, atm or µatm) - fCO2 (fugacity() in hPa, Pa, atm or µatm)

  • T_out (float | pandas.Series) – The temperature towards which the data shall be corrected. Typically, the in-situ temperature (°C or K), at which the water was sampled.

  • T_in (float | pandas.Series) – The temperature from which the data shall be corrected. Typically, the temperature (°C or K) at the equilibrator, at which the water was measured.

  • method (str) – Either “Takahashi2009” [Takahashi et al., 2009] or “Takahashi1993” [Takahashi et al., 1993], describing the method of the respectively published paper.