atmospheric-lidar 0.2.7

Package for reading raw atmospheric lidar data.

Overview

This package provides utilities to handle raw (atmospheric) lidar input data. The main format supported are Licel binary files (including the Raymetrics modified format).

The package provides a single command line tool, called licel2scc that can convert Licel binary files to the EARLINET’s Single Calculus Chain NetCDF format.

Using it as a Licel to SCC converter

Parameter file

Before converting Licel binary to SCC format, you need to create a file linking Licel channels to SCC channels.

As an example, you can start by changing the file “cf_netcdf_parameters.py” that describe such parameters for the Clermont Ferrand lidar.

Command line interface

The usage of the licel2scc program is described bellow:

usage: licel2scc [-h] [-i] [-m MEASUREMENT_ID] [-n MEASUREMENT_NUMBER]
                 [-t TEMPERATURE] [-p PRESSURE] [-d] [-s]
                 parameter_file [directory] [search_string]

A program to convert LICEL binary files to the SCC NetCDF format.

positional arguments:
  parameter_file        The path to a parameter file linking licel and SCC
                        channels.
  directory             Directory containing licel files (default '.')
  search_string         Search string for files in directory (default '*.*')

optional arguments:
  -h, --help            show this help message and exit
  -i, --id_as_name      Use transient digitizer ids as channel names, instead
                        of descriptive names
  -m MEASUREMENT_ID, --measurement_id MEASUREMENT_ID
                        The new measurement id
  -n MEASUREMENT_NUMBER, --measurement_number MEASUREMENT_NUMBER
                        The measurement number for the date from 00 to 99.
                        Used if no id is provided
  -t TEMPERATURE, --temperature TEMPERATURE
                        The temperature (in C) at lidar level, required if
                        using US Standard atmosphere
  -p PRESSURE, --pressure PRESSURE
                        The pressure (in hPa) at lidar level, required if
                        using US Standard atmosphere
  -d, --debug           Print dubuging information.
  -s, --silent          Show only warning and error messages.

Usage in python code

System class

To read data from a system, you need create a class that describes you system. This is very simple if your lidar data are in the Licel format, as you only need to specify the external file with the extra SCC parameters. You can use as an example the file cf_netcdf_parameters.py:

from licel import LicelLidarMeasurement
import cf_netcdf_parameters

class CfLidarMeasurement(LicelLidarMeasurement):
    extra_netcdf_parameters = cf_netcdf_parameters

This code assumes that the cf_netcdf_parameters.py is in your python path.

Using the class

Once you have made the above setup you can start using it. The best way to understand how it works is through an interactive shell (I suggest [ipython](http://ipython.org/)). In the following example I use the cf_raymetrics setup:

import glob  # This is needed to read a list of filenames
import cf_lidar

# Go to the folder where you files are stored
cd /path/to/lidar/files

# Read the filenames
files  = glob.glob("*") # The * reads all the files in the folder.

# Read the files
my_measurement = cf_lidar.CfLidarMeasurement(files)

# Now the data have been read, and you have a measurement object to work with:
# See what channels are present
print(my_measurement.channels)

# Quicklooks of all the channels
my_measurements.plot()

Converting to SCC format

There are some extra info you need to put in before converting to SCC format, “Measurement_ID”, “Temperature”, “Pressure”:

my_measurement.info["Measurement_ID"] = "20101229op00"
my_measurement.info["Temperature"] = "14"
my_measurement.info["Pressure"] = "1010"

You can use standard values of temperature and pressure by just calling:

my_measurement.get_PT()

You can specify the standard values by overriding your system’s get_PT method:

from licel import LicelLidarMeasurement
import cf_netcdf_parameters

class CfLidarMeasurement(LicelLidarMeasurement):
    extra_netcdf_parameters = cf_netcdf_parameters

    def get_PT():
        self.info['Temperature'] = 25.0
        self.info['Pressure'] = 1020.0

If you have an external source of temperature and pressure information (a meteorological station) you can automate this by reading the appropriate code in the get_PT method .

After you have used this extra input, you save the file using this command:

my_measurement.save_as_netcdf("filename")

where you change the output filename to the filename you want to use.