Filename conventions

Each radar file follows the following naming convention:

<instrument_name>_<platform_name>_<date>-<time>_<scan_type>_<processing_level>_v<version>.nc,

where the platform name is set to cao, to denote Chilbolton Atmospheric Observatory, and the date is given in the format <YYYYmmdd>.

The scan_type is fix-ts, as all files relate to time series from fixed vertical pointing dwells.

There are three instruments:

ncas-radar-camra-1 is the 3 GHz Chilbolton Advanced Meteorological Radar (CAMRa), which uses the 25 m Chilbolton antenna.

ncas-radar-ka-band-1 is the 35 GHz Copernicus cloud radar, which has a 2.4 m fixed vertically pointing antenna.

ncas-radar-w-band-1 is the 94 GHz Galileo radar, which is a bistatic system with two 0.46 m antennae separated by 0.66 m.

File format description

Level 1 files are provided, and follow the description below. They have been derived by processing Level 0a (as-recorded) data, with the processing steps indicated in the history attribute. See Raw data conversion for a summary of processing software.

Level 1 files

These files are in NetCDF-4 format with the following content:

Common global attributes

The following global atrributes are present for all three radars:

Name	Example
product_version	v1.0
licence	This dataset is released for use under a Creative Commons Attribution 4.0 International (CC-BY 4.0) license (see https://creativecommons.org/licenses/by/4.0/ for terms and conditions)
acknowledgement	This dataset was developed as part of the activity “Doppler Wind Radar Science Performance Study (WIVERN-2)”, funded by the European Space Agency under Contract no. 4000130864/20/NL/CT. Users should acknowledge UK Research and Innovation as the data provider (in partnership with the National Centre for Atmospheric Science)
platform	Chilbolton Atmospheric Observatory
platform_type	stationary_platform.
creator_name	Chris Walden
creator_email	chris.walden@ncas.ac.uk
creator_url	https://orcid.org/0000-0002-5718-466X
institution	National Centre for Atmospheric Science (NCAS)
instrument_name	ncas-radar-camra-1
instrument_software	radar-camra-rec
instrument_software_version	1.4 Rev 58
references	https://doi.org/10.1049/ecej:19940205; http://purl.org/net/epubs/work/63318; https://doi.org/10.1109/IGARSS.2006.429; https://doi.org/10.3390/atmos10110714;
source	3GHz Chilbolton Advanced Meteorological Radar (CAMRa)
project	WIVERN-2 Doppler Wind Radar Science Performance Study
project_principal_investigator	Anthony Illingworth
project_principal_investigator_email	a.j.illingworth@reading.ac.uk
project_principal_investigator_url	https://orcid.org/0000-0002-5774-8410
processing_software_url	https://github.com/longlostjames/wivern_chilbolton_utils.git
processing_software_version	1.0
processing_level	1
scantype	vertical_pointing
time_coverage_start	2020-10-01T18:09:28Z
time_coverage_end	2020-10-01T18:21:22Z
geospatial_bounds	51.1450N -1.4384E
pulse_compression	false
ADC_bits_per_sample	12
ADC_channels	8
last_revised_date	2022-03-28T14:19:36Z
title	Calibrated time series from 3 GHz CAMRa radar collected for ESA WIVERN-2 campaign at Chilbolton Observatory
comment	Correction to account for inverse square power loss with range has not been applied
history	Mon Feb 28 17:20:39 2022 - user:cjwalden machine: host293.jc.rl.ac.uk program: wivern_chilbolton_utils.py convert_camra_ts_l0b2l1 version:1.0n Mon Feb 28 17:20:00 2022 - user:cjwalden machine: host293.jc.rl.ac.uk program: wivern_chilbolton_utils.py convert_camra_ts_l0a2l0b version:1.0n Mon Dec 6 16:58:37 2021: /home/users/cjwalden/anaconda3/envs/cao_3_8/bin/ncks -d time,6,37 –output=radar-camra_20201001180645_fix-ts.nc radar-camra_20201001180645_fix-ts_orig.ncn Thu Oct 01 18:07:00 2020 - /usr/local/bin/radar-camra-rec -fix 3600 115 90 -gates 5 201 -cellsize 1 -pulse_pairs 3050 -op rad -id 0 -file 8030 -scan 7827 -date 20201001180645 -tsdump -tssamples 200

Scalar variables

The following scalar variables are present for all three radars:

Name	Data type	Long name	Units
latitude	float32	latitude of the antenna	degree_north
longitude	float32	longitude of the antenna	degree_east
altitude	float32	altitude of the elevation axis above the geoid (WGS84)	m
altitude_agl	float32	altitude of the elevation axis above ground	m
frequency	float32	frequency of transmitted radiation	GHz
prf	float32	pulse repetition frequency	Hz
beamwidthH	float32	horizontal angular beamwidth	degree
beamwidthV	float32	vertical angular beamwidth	degree
antenna_diameter	float32	antenna diameter	m
antenna_focal_length	float32	focal length of antenna	m
antenna_focus_radial_location	float32	distance along boresight from elevation axis to focus	m
pulse_width	float32	pulse width	us
transmit_power	float32	peak transmitted power	W
clock	float32	clock input to timer card	Hz
clock_divide_factor	float32	clock divide factor	1
delay_clocks	float32	clock cycles before sampling is initiated	1
samples_per_pulse	float32	number of samples per pulse	1
pulses_per_daq_cycle	float32	number of pulses per data acquisition cycle	1
pulses_per_ray	float32	number of pulses per ray	1
radar_constant	float32	radar constant	dB
receiver_gain	float32	receiver gain	dB
cable_losses	float32	cable losses	dB
extra_attenuation	float32	extra attenuation	dB

Dimensions

The following dimensions are present for all three radars: time, pulse and range.

Coordinate variables

These have slightly different interpretation depending on the particular radar.

3GHz CAMRa radar

Name	Data type	Dimension	Long name	Units
time	float32	time	time at the end of each recorded ray	seconds since 2020-09-22 00:00:00 +00:00
range	float32	range	distance from the antenna to the middle of each range gate	m
elevation	float32	time	elevation angle of the antenna boresight above the horizon.	degree
azimuth	float32	time	azimuth angle of the antenna boresight clockwise from grid north.	degree

35GHz Copernicus radar

Name	Data type	Dimension	Long name	Units
time	float32	time	time at the end of each recorded ray	seconds since 2020-09-22 00:00:00 +00:00
range	float32	range	distance from the antenna to the middle of each range gate	m
elevation	float32	time	elevation angle of the antenna boresight above the horizon.	degree
azimuth	float32	time	azimuth angle of the antenna boresight clockwise from grid north.	degree

94GHz Galileo radar

Name	Data type	Dimension	Long name	Units
time	float32	time	time at the end of each recorded ray	seconds since 2020-09-22 00:00:00 +00:00
range	float32	range	distance from the antenna to the middle of each range gate	m
elevation	float32	time	elevation angle above the horizon of the plane containing the transmit and receive antenna boresights	degree
azimuth	float32	time	azimuth angle clockwise from grid north of the plane in which the antenna boresights are tilted away from zenith	degree

Field variables

Name	Date type	Dimensions	Long name	Units
I	float32	time, pulse, range	co-polar in-phase video signal	1
Q	float32	time, pulse, range	co-polar quadrature video signal	1
ZCX	float32	time, pulse, range	cross-polar radar equivalent reflectivity factor	dBZ

Quality control variables

Name	Date type	Dimensions	Long name	Units
qc_flag	uint8	time, pulse, range	quality control flag
dBZ_offsets_applied	float32	pulse	dBZ calibration offset applied for even and odd pulses	dB