This software package processes raw Iridium output from the CSIR / STS CO2 instrument into a readable table format. The instrument uses an equilibrator approach to measure CO2 with a LICOR-820.
Basic instructions
- Go to the
IMPORT
page and browse your computer for the raw input files.
- Click
Process data
to reformat the data. The button also calculates pCO2 and fCO2.
- The data can then be saved as `CSV` or an excel spreadsheet.
- Plot the data with the www.plot.ly interface under
MAP
and TIME SERIES
About WaveGliDA
Authors: Luke Gregor and Clinton Hagan
Feedback: lukegre@gmail.com
Version: 0.3.1 (16 May 2017)
This application is built in Python using the `Flask` backend framework. Calculations are done using `Pandas`.
CO2 calculations
The CSIR/STS CO2 instrument returns the mole fraction of carbon dioxide (xCO2) as given by the LICOR-820 instrument. xCO2 is used to calculate parital pressure of CO2 and fugacity CO2 with the equations shown below. The methods presented below are in the ./backend/calculations.py
file.
$$ p\mbox{CO}_2^{sst} = x\mbox{CO}_2 \times P_c \times \exp(0.0423 \cdot \Delta T) $$
where $\Delta T$ is the difference between the equilibrator and sea surface temperatures. This empirical exponential relationship is as defined by Takahashi et al. (1993). Note that $\Delta T$ is considered 0 K for Wave Glider installations of the instrument, i.e. the equilibrator and sea surface temperatures are exactly the same. $P_{atm}$ is measured atmospheric pressure corrected for the partial pressure of H2O.
$$P_c = (P_{atm} - P_{H_2O})$$
where $P_{H_2O}$ is calculated from salinity and temperature according to Weiss and Price (1980). This is done for both marine and atmospheric measurements of CO2.
The fugacity of CO2 is a correction for the non-ideal behaviour of CO2. This is done by calculating the vireal expansion as shown below:
$$ f\mbox{CO}_2^{sst} = p\mbox{CO}_2 \times \frac{P_{atm}}{k_B T} $$
where $k_B$ is the Boltzmann constant and $T$ is the absolute temperature. This expression is equivalent to the expansion
$$ \rho + B_2(T)\rho^2 + B_3(T)\rho^3 + ... , $$
where $\rho$ is the density of CO2
For more information see the code below used to calculate these functions.