Calculate nitrogen concentration from a SUNA on a Sea-Bird Navis BGCi

This readme is a github friendly version of calculate_Navis_Nitrogen_Worksheet.m

Load data from SUNA on a Sea-Bird Navis BGCi and calculate nitrogen

This script imports SUNA data files (.isus) and SUNA calibration files (.cal) and calculates nitrogen concentration.

The data from SUNAs are telemetered via satellite from the BGCi float as ASCII files with the .isus file extension. The SUNA is operating in APF mode such that the data format is in the APF frame.

The calibration data is provided to the customer by Sea-Bird upon initial delivery as ASCII files with .cal file extension. When the reference spectrum is updated by the customer upon delivery of the insttrument, the a new .cal file will be produced and should be used to process the data.

Nitrogen concentrations are calculated following Johnson et al. (2016).

Each cell in the worksheet can be executed using the run section button or by typing ctrl-enter into the command line

KiM MARTiNi 03.2018 [email protected]

DISCLAIMER: Software is provided as is.

REFERENCES:

Johnson, Ken, Orens Pasqueron De Fommervault, Romain Serra, Fabrizio D'Ortenzio, Catherine Schmechtig, Hervé Claustre, and Antoine Poteau. "Processing Bio-Argo nitrate concentration at the DAC Level." (2016).

Load the most recent calibration file.

This should be the calibration associated with the reference spectrum update performed by the customer

% define calibration file, with the full path 
cal_target_dir = 'C:\SUNAcals\SNA1099C.cal'; 

% use the provided script to load the calibration data
% outputs a structure with all the data in the calibration file
[cal] = readSUNAcal( cal_target ); 

Load the data file from the Navis float

this is an ASCII text file with extension .isus

% define the data file to import, with the full path
data_target = 'I:\SUNAdata\0883.002.isus'; 

% use the provided script to load the calibration data
% outputs a structure with all the data in the data file
[dat] = readNavisSUNA( data_target ); 

calculate nitrogen concentrations

% define some auxillary data
% define the vertical distance between the CTD pressure port and the
% SUNA window (default is zero)
aux.deltaP = -0.87; % [m]
% define the optical wavelength offset, which is constant
aux.OPTICAL_WAVELENGTH_OFFSET = 208.5; % [nm]

% Calculate nitrogen concentrations. MolarNitrate and Nitrate fields will
% be added to the .dat structure and contain concentrations in units of 
micromol/L and micromole/kg, respectively.
[dat] = APF2NO( dat, cal, aux );