This page provides an overview of some of the techniques that are commonly used to eliminate clutter and unwanted reflections within a weather radar system to allow a smoothed view of the objects of interest to be constructed. There are a wide range of methods (and algorithms) defined to allow for the different types of clutter to be discriminated and disregarded from the useful returns. These include:
- Clutter Map (processing)
A clutter map can be generated for a specific primary radar installation that identifies the expected levels of unwanted returns from non-fluctuating obstructions to the radar beam.
- Doppler processing
Doppler processing is commonly used to identify returns from moving objects and provide a figure for their radial velocity (or velocity relative to their distance towards or from the radar). Its weakness however is that it can only detect velocity of an object in one plane.
- Polarization (reduction)
Polarization techniques are used to detect the “direction” of the electric field (E) of the electromagnetic wave. There are linear and circular polarization techniques known. In weather radar, Polarimetric weather radar systems (although still Doppler radars) measure dual polarization in the horizontal and vertical planes and use this information against another set of recorded characteristics (e.g. look up table) as another indicator of the type of the weather.
- Linear Polarization (most suitable in clear weather conditions) and circular polarization (most suitable for use in precipitous weather conditions) are used primarily by PSR systems. Their use is optimised to remove weather clutter.
- Dual Polarization (horizontal and vertical) together provide the differential reflectivity of weather (which can be used to identify weather types). Polarization techniques are now becoming common in today's weather radar systems.
- Other Clutter Processing and Reduction Techniques
The above issues will be examined in more detail in the module “Radar Basics”. It is noted however that a considerable number of other techniques for the processing and reduction of clutter are also defined and used in some radar implementations (for example, statistical analysis techniques). These are not examined in detail in this module.