### Command line interface

## alcf calibrate

alcf calibrate - calibrate ALC backscatter

Calibration based the O’Connor et al. (2004) method of lidar ratio (LR) in fully opaque stratocumulus clouds.

Usage: `alcf calibrate <type> <time_periods> <input> <output> [<options>]`

- `type`: lidar type (see Types below)
- `time_periods`: file containing calibration time periods of stratocumulus clouds in the backscatter profiles (see Time periods below)
- `input`: input directory containing NetCDF files (the output of `alcf lidar`)
- `output`: output calibration file
- `options`: see Options below.

Types:

- `chm15k`: Lufft CHM 15k
- `cl31`: Vaisala CL31
- `cl51`: Vaisala CL51
- `minimpl`: Sigma Space MiniMPL
- `mpl`: Sigma Space MPL

Time periods file:

A text file containting start and end time (see Time format below) of a time period separated by whitespace, one time period per line:

    <start> <end>
    <start> <end>
    ...

where `start` is the start time and `end` is the end time.

Time format:

“YYYY-MM-DD[THH:MM[:SS]]”, where YYYY is year, MM is month, DD is day, HH is hour, MM is minute, SS is second. Example: 2000-01-01T00:00:00.

Examples:

`alcf calibrate time_periods.txt lidar calibration.txt`

Read time periods from `time_periods.txt`, lidar profiles from the directory `lidar` and write the calibration coefficient to `calibration.txt`.