### Documentation

## ALCF output

The ALCF output is stored in NetCDF files. Below is a description of variables contained in the data files. Variable names follow the CMIP5 standard output. Time is stored as Julian date and can be converted to Unix time (the number of non-leap seconds since 1970-01-01 00:00 UTC) with the formula `(time - 2440587.5)*86400`.

### model

`alcf model` output is a 2-dimensional “curtain” of model data at a given location over a length of time or along a ship track.

Variable | Description | Dimensions | Units
--- | --- | --- | ---
cl | cloud area fraction in atmosphere layer | time, level | %
cli | mass fraction of cloud ice in air | time, level | 1
clw | mass fraction of cloud liquid water in air | time, level | 1
lat | latitude | time | degrees north
lon | longitude | time | degrees east
orog | surface altitude | time | m
pfull | air pressure | time, level | Pa
ps | surface air pressure | time | Pa
ta | air temperature | time, level | K
time | time | time | days since -4712-01-01 12:00
zfull | height above reference ellipsoid | time, level | m

### cosp

`alcf simulate` output is a 2-dimensional “curtain” of simulated backscatter at a given location over a length of time or along a ship track.

Variable | Description | Dimensions | Units
--- | --- | --- | ---
backscatter | total attenuated backscatter coefficient | time, level, column | m-1.sr-1
backscatter_mol | total attenuated molecular backscatter coefficient | time, level | m-1.sr-1
lat | latitude | time | degrees north
lon | longitude | time | degrees east
pfull | air pressure | time, level | Pa
time | time | time | days since -4712-01-01 12:00
zfull | height above reference ellipsoid | time, level | m

### lidar

`alcf lidar` output is a 2-dimensional “curtain” of observed or simulated backscatter at a given location over a length of time or along a ship track.

Variable | Description | Dimensions | Units
--- | --- | --- | ---
backscatter | total attenuated backscatter coefficient | time, range | m-1.sr-1
backscatter_sd | total attenuated backscatter coefficient standard deviation | time, range | m-1.sr-1
cbh | cloud base height | time | m
cloud_mask | cloud mask | time, range | 1
lr | lidar ratio | time | sr
time | time | time | days since -4712-01-01 12:00
zfull | height above reference ellipsoid | time, level | m

### stats

`alcf stats` output contains histograms and summary statistics calculated from a 2-dimensional “curtain” of observed or simulated backscatter.

Variable | Description | Dimensions | Units
--- | --- | --- | ---
backscatter_avg | total attenuated backscatter coefficient average | zfull | m-1.sr-1
backscatter_full | total attenuated backscatter coefficient | backscatter_full | m-1.sr-1
backscatter_hist | backscatter histogram | backscatter_full, zfull | %
backscatter_mol_avg | total attenuated molecular backscatter coefficient average | zfull | m-1.sr-1
backscatter_sd_full | total attenuated backscatter coefficient standard deviation | backscatter_sd_full | m-1.sr-1
backscatter_sd_hist | total attenuated backscatter coefficient standard deviation histogram | backscatter_sd_full | %
backscatter_sd_z | total attenuated backscatter coefficient standard deviation height above reference ellipsoid | m |
cl | cloud area fraction in atmosphere layer | zfull | %
clt | cloud area fraction |  | %
n | number of profiles |  | 1
zfull | height above reference ellipsoid | zfull | m