nais-processor 0.0.3

Code to process ion spectrometer data files

NAIS processor

Use this code package to process NAIS (Neutral cluster and Air Ion Spectrometer, Airel Ltd.) data files.

The code corrects for diffusion losses in the inlet line (Gromley and Kennedy, 1948) and applies an ion mode calibration (Wagner et al. 2016). Optionally the data can be corrected to standard conditions (273.15 K, 101325 Pa), which can be useful when comparing aerosol particle and ion data from various locations at different altitudes.

Installation

pip install nais-processor

Documentation

Example usage

Open the python prompt and load methods from the nais_processor module. Then use the make_config() method to create a configuration file that is used at processing the data files.

$ python
>>> from nais_processor import *
>>> make_config()

Enter name of configuration file.
E.g. ./configs/campaign.yml
> ./nais-5-33.yml  

Give path(s) to raw data. If multiple paths give them as comma separated list.
E.g. /data/nais/2021,/data/nais/2022
> ./nais-5-33

Path to where processed data is saved.
E.g. ./data/campaign/processed
> ./nais-5-33

Path to where figures are saved. Leave empty if no figures.
E.g. ./data/campaign/figures
> ./nais-5-33   

Start of measurement (YYYY-MM-DD)
> 2022-09-28

End of measurement (YYYY-MM-DD)
If empty processor assumes current day, use for continuous measurements.
> 2022-09-30

Enter name of database file
E.g. ./logs/campaign.json
> ./nais-5-33.json  

Allow reprocessing (True/False)
Overwrites already processed datafiles in the database when running the processor again.
> True

Measurement location
E.g. Helsinki, Kumpula
> Helsinki, Lab 

Apply corrections to data? (True/False)
Requires a NAIS with temperature and pressure sensors.
> True 

Length of the inlet in meters
> 0.0 

Correct concentrations to sealevel conditions? (True/False)
> False

Configuration saved to: ./nais-5-33.yml

The resulting configuration file nais-5-33.yml looks like this:

allow_reprocess: true
apply_corrections: true
data_folder:
- ./nais-5-33
database_file: ./nais-5-33.json
end_date: '2022-09-30'
figure_folder: ./nais-5-33
inlet_length: 0.0
location: Helsinki, Lab
processed_folder: ./nais-5-33
sealevel_correction: false
start_date: '2022-09-28'

Then process the data files by running nais_processor() method with the config file as the input argument.

>>> nais_processor("./nais-5-33.yml")
Configuration file: ./nais-5-33.yml
processing 20220928
processing 20220929
processing 20220930
Done!

Run do_daily_figs() with the config file in order to create plots of the processed data if needed.

>>> do_daily_figs("./nais-5-33.yml")
plotting 20220928
plotting 20220929
plotting 20220930
Done!

The code produces daily processed data files and optionally figures for ion and particle data. These files are saved in the destinations given in the configuration file.

The data files are named

NAIS[n|p][yyyymmdd][np|nds].sum

where n and p refer to negative and positive polarity respectively. yyyymmdd tells the date in the year-month-day format. np and nds refer to particle and ion data respectively.

The data files have the following structure:

[0,0]  = UTC offset in hours
[1:,0] = Time (MATLAB datenum) 
[0,2:] = Geometric mean diameter of size-channel (m)
[1:,1] = Integrated total number concentration (cm-3)
[1:,2:] = Normalized number concentrations, dN/dlogDp (cm-3)

The locations of raw files, processed files and possible figures are written in the database_file, which is in JSON format.

Combining sumfiles

Once you have processed your NAIS data you can combine multiple daily sumfiles into a single multi-day sumfile using the combine_spectra() function. You can also extract data from within one day like this.

Example:

import nais_processor as nais

start_time="2020-07-04 20:00:00"
end_time="2020-07-08 12:00:00"

combined_data = nais.combine_spectra(
    config_file,start_time,end_time,spectra_type="negion")

The spectra types are: negion (default), posion, negpar and pospar.

You can also plot data using plot_sumfile().

License

This project is licensed under the terms of the GNU GPLv3.

References

Gormley P. G. and Kennedy M., Diffusion from a Stream Flowing through a Cylindrical Tube, Proceedings of the Royal Irish Academy. Section A: Mathematical and Physical Sciences, 52, (1948-1950), pp. 163-169.

Wagner R., Manninen H.E., Franchin A., Lehtipalo K., Mirme S., Steiner G., Petäjä T. and Kulmala M., On the accuracy of ion measurements using a Neutral cluster and Air Ion Spectrometer, Boreal Environment Research, 21, (2016), pp. 230–241.