Network Common Data Form (netCDF) is a set of software libraries and self-describing, machine-independent data formats that support the creation, access, and sharing of array oriented scientific data.
The netCDF file name format is <cl.sender.fileprefix><reporting.livefile.nameprefix>_YYYYMMDD_HHmmss.nc, where:
- You can define 2 different types of prefixes to write in the netCDF filename.
- The last part is the timestamp when the file was created.
NetCDF is a set of interfaces for array-oriented data access and a freely distributed collection of data access libraries for C, Fortran, C++, Java, and other languages.
The netCDF format used in CL61 is built on netCDF‑4 which is built on Hadoop Distributed File System (HDFS). You can open and read CL61 netCDF files with any HDFS or netCDF‑4 reader, for example, Panoply.
NetCDF file format allows the grouping of data types into a single file. A netCDF file is made of one or several variables. Each variable consists of:
- Data: a multidimensional table or value
- Metadata: data that characterizes the data
CL61 netCDF files are sent using SFTP protocol to a customer server. The ceilometer is defined as a secure client using a key-based scheme. The files contain the following data:
- Time series of atmospheric backscatter and polarization profiles
- Time series of cloud heights and vertical visibility
- Time series of total cloud cover (sky condition)
- Time series of cloud layer specific covers and heights (sky condition)
- Metadata, including:
- Interface version
- Device identity and location
- Device status and monitoring data
| Attribute | Description | ||
|---|---|---|---|
| Title | Type of the device | ||
| Institution | User configurable with CL61 configuration parameters | ||
| Source | Blank | ||
| Conventions | NetCDF convention version | ||
| History |
Device firmware version, the version of the netCDF schema
|
||
| Comment | User configurable with CL61 configuration parameters | ||
| Unit | m | ||
| Temporal span of this file in minutes | Default 1 min | ||
| Time between consecutive profiles in seconds | Default 5 s |
| Variable name | Type | Dimension | Description | Unit |
|---|---|---|---|---|
| cloud_base_heights | int | time, layer | Heights (range) of the detected cloud bases | meters |
| vertical_visibility | int | time | Visibility in the direction of the instrument beam | meters |
| p_pol | float | time, range | Parallel-polarized component of the backscattered light (PPOL) |
m-1sr-1 |
| x_pol | float | time, range | Cross-polarized component of the backscattered light (XPOL) |
m-1sr-1 |
| beta_att | float | time, range | Attenuated volume backscatter coefficient (ABS) |
m-1sr-1 |
| linear_depol_ratio | float | time, range | Linear depolarization ratio of the backscatter volume (LDR) | - |
| time | double | time | Seconds since 1970-01-01 00:00:00.000 | seconds |
| range | double | range | Distance in the direction of the instrument beam | meters |
| layer | int | layer | Number of the observed cloud layer (1, 2, 3, 4, 5) | - |
| longitude | double | time | Longitude | degrees east |
| latitude | double | time | Latitude | degrees north |
| elevation | int | time | Measurement site height above or below a fixed reference point, most commonly a reference geoid | meters |
| beta_att_sum | double | time | Scaled integral of the attenuated volume backscatter coefficient | 10-4sr-1 |
| beta_att_noise_level | double | time | A unitless number describing the noise level of the attenuated volume backscatter coefficient | - |
| tilt_correction | short | time | Use of tilt correction | |
| tilt_angle | float | time | Instrument tilt angle from the vertical | |
| height_offset | short | time |
Instrument height offset to reference level Positive if the instrument is placed, for example, on the roof of a building. Negative if the instrument is placed below the ground level altitude, for example, in a pit. This value will be added to the cloud base height results. |
meters |
| sky_condition_total_cloud_cover | short | time | Total amount of cloud cover | oktas |
| sky_condition_cloud_layer_covers | short | time, layer | Amount of cloud cover in different cloud layers | oktas |
| sky_condition_cloud_layer_heights | int | time, layer | Height of different cloud layers | meters |
| Dimension | Description | Value |
|---|---|---|
| Time | Number of profiles in file | Depends on file length |
| Range | Length of single profile | 3276 |
| Layer | Number of reported cloud base heights | 5 |