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This page outlines the some of the work that has been done or is in progress in the Radar Group.Note: the information on this page is rather old, and needs updating.
The main interest in clouds stems from their strong effect on the earth's radiation budget and hence their role in the climate system. Standard cloud observing instruments such as satellite-borne radiometers suffer from poor vertical resolution, but in recent years there has been growing interest in the use of millimetre-wave radar to make high vertical resolution measurements of clouds. A single radar can be used to determine the macroscopic properties of clouds (such as cloud cover and inhomogeneity), while combinations of active instruments can be used to derive microphysical properties (such as water content and particle size). These can be used to directly validate atmospheric models or to test algorithms that could be used by the proposed spaceborne cloud radar and lidar. The work is funded under the Cloud Characteristics project.
Deriving cloud overlap statistics from radar.
Quantifying the effect of cirrus inhomogeneity on emissivity.
Cirrus particle sizing using a spaceborne radar and lidar.
Dual-wavelength measurement of liquid water content in stratocumulus.
Dual-wavelength measurement of ice water content in cirrus.
Weather radarThe polarisation and Doppler capability of the Chilbolton 3-GHz radar, coupled with its very narrow beamwidth, make it an ideal tool with which to study the characteristics of precipitation. Much of the work is focussed towards improving the algorithms used by radars to measure rain rate for the purposes of flood forecasting. Radar also offers the possibility to distinguish between heavy rain and hail. Recent work has included:
Development of attenuation correction algirithms at C-band using ZDR.
Deriving raindrop shape versus size from the consistency of the various polarimetric variables - fundamental to many rain retrieval algorithms.
Distinguishing between convective and stratiform rain using vertical profiles of reflectivity - improves rainrate measurements made by non-polarised radars.
A case study in which oblate hail was observed with a preferred fall mode - could have profound implications for existing hail-detection algorithms.
Mesoscale dynamicsWhen cloud or rain is present, the radars at Chilbolton can measure the velocity component along a line towards the antenna, which enables the wind field associated with mesoscale weather systems to be mapped out. The unique 1/4 degree beamwidth of the 3-GHz radar enables structure on much smaller scales to be resolved which is essential for measuring waves and convection.
Here we present images and preliminary analysis from experiments and new data acquisition systems.
Doppler spectra in stratocumulus on 26 August 1998: bimodal spectra
CWVC 1: 3D visualisation; velocity structure; model comparison
Negative KDP as an indicator of strong electric fields in thunderstorms