Level 2a Cloudnet product:

Stratocumulus drizzle (radar/lidar method)

Summary

Designation

drizzle

Level

2a

Algorithm design/Product maintainer

Institute

University of Reading

Description

Drizzle parameters such as drizzle flux and mean particle size, derived from combined radar and lidar beneath cloud base.

Documentation

See relevant publication

Relevant publication(s)

O'Connor, E. J., R. J. Hogan and A. J. Illingworth, 2005: Retrieving stratocumulus drizzle parameters using Doppler radar and lidar.J. Appl. Meteorol., 44(1), 14-27. PDF

Quicklooks

http://www.met.rdg.ac.uk/radar/cloudnet/quicklooks/

Suggested acknowledgement

We acknowledge the Cloudnet project (European Union contract EVK2-2000-00611) for providing the stratocumulus drizzle retrieval, which was produced by the University of Reading using measurements from [SITE].

Dataset contents

Sample NetCDF file: 20030701_chilbolton_drizzle.nc
Header of sample NetCDF file in ASCII: 20030701_chilbolton_drizzle.cdl

The following is a description of the variables in this product, produced automatically from the metadata in the sample file (using the nc2html unix utility):

Dataset title: Drizzle parameters from Chilbolton

Institution:Data processed at the Department of Meteorology, University of Reading.
Software version:1.2

Dimensions and coordinate variables

Units:hours since 2003-07-01 00:00:00 +0:00
Type:single-precision floating-point vector

Units:m
Type:single-precision floating-point vector

Variables

Units:degrees_north
Type:single-precision floating-point scalar

Units:degrees_east
Type:single-precision floating-point scalar

Units:m
Type:single-precision floating-point scalar

Units:GHz
Type:single-precision floating-point scalar

This variable was calculated from the 94-GHz radar reflectivity factor after correction for gaseous attenuation, the Doppler mean velocity, the Doppler spectral width after correction for turbulence using the 30-s standard deviation of the (approximately) 1-s mean radar Doppler velocities and the horizontal winds from a forecast model using the technique of Bouniol et al. (2003, Proc. 31st AMS Conf. on Radar Meteorology, Seattle), the lidar backscatter and temperature taken from a forecast model, using the technique of O'Connor et al. (2004)

Units:m
Type:single-precision floating-point array
Variable containing the random error in Do:Do_error
Variable containing the bias in Do:Do_bias

This variable was calculated from the 94-GHz radar reflectivity factor after correction for gaseous attenuation, the Doppler mean velocity, the Doppler spectral width after correction for turbulence using the 30-s standard deviation of the (approximately) 1-s mean radar Doppler velocities and the horizontal winds from a forecast model using the technique of Bouniol et al. (2003, Proc. 31st AMS Conf. on Radar Meteorology, Seattle), the lidar backscatter and temperature taken from a forecast model, using the technique of O'Connor et al. (2004)

Units:m^-4
Type:single-precision floating-point array
Variable containing the random error in N:N_error

This variable was calculated from the 94-GHz radar reflectivity factor after correction for gaseous attenuation, the Doppler mean velocity, the Doppler spectral width after correction for turbulence using the 30-s standard deviation of the (approximately) 1-s mean radar Doppler velocities and the horizontal winds from a forecast model using the technique of Bouniol et al. (2003, Proc. 31st AMS Conf. on Radar Meteorology, Seattle), the lidar backscatter and temperature taken from a forecast model, using the technique of O'Connor et al. (2004)

Units:
Type:single-precision floating-point array
Variable containing the random error in mu:mu_error

This variable was calculated from the 94-GHz radar reflectivity factor after correction for gaseous attenuation, the Doppler mean velocity, the Doppler spectral width after correction for turbulence using the 30-s standard deviation of the (approximately) 1-s mean radar Doppler velocities and the horizontal winds from a forecast model using the technique of Bouniol et al. (2003, Proc. 31st AMS Conf. on Radar Meteorology, Seattle), the lidar backscatter and temperature taken from a forecast model, using the technique of O'Connor et al. (2004)

Units:sr
Type:single-precision floating-point array
Variable containing the random error in S:S_error

This variable was calculated from the 94-GHz radar reflectivity factor after correction for gaseous attenuation, the Doppler mean velocity, the Doppler spectral width after correction for turbulence using the 30-s standard deviation of the (approximately) 1-s mean radar Doppler velocities and the horizontal winds from a forecast model using the technique of Bouniol et al. (2003, Proc. 31st AMS Conf. on Radar Meteorology, Seattle), the lidar backscatter and temperature taken from a forecast model, using the technique of O'Connor et al. (2004)

Units:kg m^-3
Type:single-precision floating-point array
Variable containing the random error in lwc:lwc_error
Variable containing the bias in lwc:lwc_bias

This variable was calculated from the 94-GHz radar reflectivity factor after correction for gaseous attenuation, the Doppler mean velocity, the Doppler spectral width after correction for turbulence using the 30-s standard deviation of the (approximately) 1-s mean radar Doppler velocities and the horizontal winds from a forecast model using the technique of Bouniol et al. (2003, Proc. 31st AMS Conf. on Radar Meteorology, Seattle), the lidar backscatter and temperature taken from a forecast model, using the technique of O'Connor et al. (2004)

Units:kg m^-2s^-1
Type:single-precision floating-point array
Variable containing the random error in lwf:lwf_error
Variable containing the bias in lwf:lwf_bias

This variable was calculated from the 94-GHz radar reflectivity factor after correction for gaseous attenuation, the Doppler mean velocity, the Doppler spectral width after correction for turbulence using the 30-s standard deviation of the (approximately) 1-s mean radar Doppler velocities and the horizontal winds from a forecast model using the technique of Bouniol et al. (2003, Proc. 31st AMS Conf. on Radar Meteorology, Seattle), the lidar backscatter and temperature taken from a forecast model, using the technique of O'Connor et al. (2004)

Units:m s^-1
Type:single-precision floating-point array
Variable containing the random error in droplet_fall_velocity:droplet_fall_velocity_error

This variable was calculated from the 94-GHz radar reflectivity factor after correction for gaseous attenuation, the Doppler mean velocity, the Doppler spectral width after correction for turbulence using the 30-s standard deviation of the (approximately) 1-s mean radar Doppler velocities and the horizontal winds from a forecast model using the technique of Bouniol et al. (2003, Proc. 31st AMS Conf. on Radar Meteorology, Seattle), the lidar backscatter and temperature taken from a forecast model, using the technique of O'Connor et al. (2004)

Units:m s^-1
Type:single-precision floating-point array
Variable containing the random error in w:w_error

This variable is an estimate of the possible systematic error (one-standard-deviation) in drizzle droplet median diameter due to the uncertainty in the calibration of the radar and lidar.

Units:dB
Type:single-precision floating-point scalar

This variable is an estimate of the one-standard-deviation random error in drizzle droplet median diameter due to the uncertainty of the retrieval, including the random error in the radar and lidar parameters.

Units:dB
Type:single-precision floating-point array

This variable is an estimate of the one-standard-deviation random error in drizzle shape parameter due to the uncertainty of the retrieval, including the random error in the radar and lidar parameters.

Units:dB
Type:single-precision floating-point scalar

This variable is an estimate of the one-standard-deviation random error in drizzle number concentration due to the uncertainty of the retrieval, including the random error in the radar and lidar parameters.

Units:dB
Type:single-precision floating-point array

This variable is an estimate of the one-standard-deviation random error in the lidar ratio due to the uncertainty of the retrieval, including the random error in the radar and lidar parameters.

Units:dB
Type:single-precision floating-point array

This variable provides the attenuation correction applied to the lidar backscatter values calculated using the lidar backscatter-to-extinction ratio, S.

Type:single-precision floating-point array

This variable is an estimate of the one-standard-deviation random error in drizzle liquid water content due to the uncertainty of the retrieval, including the random error in the radar and lidar parameters.

Units:dB
Type:single-precision floating-point array

This variable is an estimate of the one-standard-deviation random error in drizzle liquid water flux due to the uncertainty of the retrieval, including the random error in the radar and lidar parameters.

Units:dB
Type:single-precision floating-point array

This variable is an estimate of the one-standard-deviation random error in drizzle terminal fall velocity due to the uncertainty of the retrieval, including the random error in the radar and lidar parameters.

Units:dB
Type:single-precision floating-point array

This variable is an estimate of the one-standard-deviation random error in vertical air velocity due to the uncertainty of the retrieval, including the random error in the radar and lidar parameters.

Units:dB
Type:single-precision floating-point array

Converted to rainrate from raingauge c drop counts Original comment: Converted to rainrate from raingauge c drop counts

Units:mm h^-1
Type:single-precision floating-point vector

This variable describes whether a retrieval was performed for each pixel, and its associated quality, in the form of 6 different classes. The classes are defined in the definition and long_definition attributes. The retrieval method is only performed for precipitation below cloud base and is not possible in-cloud due to the severe attenuation of the lidar signal. The most reliable retrieval is for precipitation arising from the warm rain process (drizzle), indicated by the value 1, but can also be performed for light precipitation that may have originated from ice clouds, diagnosed by the presence of a melting layer and indicated by the value 2. The retrieval method is not applicable for precipitation within cloud, indicated by the value 3, while a value 4 indicates the presence of liquid water cloud with no precipitation. No attempt is made to retrieve drizzle parameters when rain reaches the ground; this is indicated by the value 5.

Type:byte array
Definition:
• 0: No liquid present
• 1: Reliable retrieval
• 2: Retrieval performed for precipitation that did not arise from the warm-rain process and may be inaccurate
• 3: Retrieval method is not applicable for precipitation within cloud
• 4: Warm liquid water clouds present but no precipitation
• 5: Rain present at the ground so no retrieval performed due to very uncertain attenuation in both radar and lidar