nais-processor 0.0.23

Code to process ion spectrometer data files

NAIS Processor

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

Installation

pip install nais-processor

Documentation

See here

Processor

The nais.processor module can be used to process the data to netcdf files and allows options for the following operations:

• Inlet loss correction (Gromley and Kennedy, 1948)
• Ion mode correction (Wagner et al. 2016)
• Conversion to standard conditions (273.15 K, 101325 Pa)
• Remove charger ion band from total particle data
• Use fill values in case of missing environmental sensor data

Example usage

Use the make_config_template()method to create a configuration file template and fill it with necessary information. The configuration file is used at processing the data files.

For example:

>>> from nais.processor import make_config_template
>>> make_config_template("/home/user/viikki.yml")

This will create a configuration file template called /home/user/viikki.yml. After filling in the information for our example measurement the file may look like this:

measurement_location: Viikki, Helsinki, Finland
longitude: 25.02
latitude: 60.23
data_folder:
- /home/user/data/2021
- /home/user/data/2022
processed_folder: /home/user/viikki
database_file: /home/user/viikki.json 
start_date: 2022-09-28
end_date: 2022-09-30
inlet_length: 1.0
do_inlet_loss_correction: true
convert_to_standard_conditions: true
do_wagner_ion_mode_correction: true
remove_corona_ions: true
allow_reprocess: false
use_fill_values: true
fill_temperature: 273.15
fill_pressure: 101325.0
fill_flowrate: 54.0

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

In our example case:

>>> from nais.processor import nais_processor
>>> nais_processor("/home/user/viikki.yml")
Building database...
Processing 20220928 (Viikki, Helsinki, Finland)
Processing 20220929 (Viikki, Helsinki, Finland)
Processing 20220930 (Viikki, Helsinki, Finland)
Done!

The code produces daily processed data files NAIS_yyyymmdd.nc (netCDF format). These files are saved in the destination given in the configuration file.

The locations of raw and processed files for each day are written in the JSON formatted database_file.

netCDF files

Fields	Dimensions	Data type	Units	Comments
Coordinates
time	time	datetime64[ns]		timezone: utc
diameter	diameter	float	m	particle diameter
flag	flag	string
Data variables
neg_ions	time,diameter	float	cm-3	dN/dlogDp
pos_ions	time,diameter	float	cm-3	dN/dlogDp
neg_particles	time,diameter	float	cm-3	dN/dlogDp
pos_particles	time,diameter	float	cm-3	dN/dlogDp
neg_ion_flags	time,flag	int		flag=1, no flag=0
pos_ion_flags	time,flag	int		flag=1, no flag=0
neg_particle_flags	time,flag	int		flag=1, no flag=0
pos_particle_flags	time,flag	int		flag=1, no flag=0
Attributes
Measurement info		dictionary

Utils

The nais.utils module contains functions that allow one to do operations on the NAIS data files.

For example combine the previously created files into a single continuous dataset with two hour time resolution and only raise a flag if at least 90% of the data points inside the two hour window contain the flag. Then save it at as a netcdf file.

from nais.utils import combine_data
import pandas as pd

data_source = "/home/user/viikki"
date_range = pd.date_range("2022-09-28","2022-09-30")

combine_data(data_source, date_range, "2H",
    flag_sensitivity=0.9).to_netcdf("combined_nais_dataset.nc")

Checker

With the nais.checker module one can visually inspect the nais ion/aerosol size distributions along with the flags and identify bad data by drawing a bounding box around it and saving the coordinates.

>>> from nais.checker import startNaisChecker
>>> startNaisChecker("combined_nais_dataset.nc","bad_data_bounds.nc")

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.