MSC Introductory Weather Radar Course

The pattern produced as random intensity fluctuations on an A-scope, usually caused by noise. It appears as closely spaced, sharp, time varying pulses.

Occurs independently of propagation conditions. It can be permanent and severe. Its occurance depends on radar location and on its scan strategy configuration. Minimization of ground clutter effects depends upon intelligent siting and signal processing.

Example Image

Description

Uses volumetric data to determine the probability of hail. These data consists of Vertically Integrated Liquid (VIL), the Melting Level, Zonal (East-West component) wind Velocity and average Relative Humidity (0 to 500 mb). The probability is determined for each column of bins within VIL in the area of surveillance and mapped in the Hail Probability Product.

Parameters

Upper limit: km
Lower limit: km
Humidity: %
Melting level: km
Zonal wind at 500 mb: m/s
Range: km

Notes

• Z/W relationships is used for VIL
• The upper and lower limits are the heights above and below which data in the data volume are not considered for the VIL calculation

Description

The Hail Signal product exploits the inherent differences in the radar signatures of rain and hail. Raindrops maintain predominately regular, oblate spheroid shapes as the fall to the earth. Hail stones, however, are irregular in shape and tumble as they fall to the earth. The Zdr for rain is generally positive but may range from 0 to 4 dB whereas the Zdr for hail is generally 0 dB.

Parameters

Upper limit: km
Lower limit: km
Range: km

Notes

• The upper and lower limits are the heights above and below which data in the data volume are not considered for the for the hail signal product

Description

2D-map containing the altitude of highest reflectivity value inside the vertical column over each surface point.

Parameters

Product data quantity: altitude
Image size: number of pixels per row (# of columns) and per column (# of rows)
Pixel size: horizontal and vertical extension of the pixel in km
Level slicing method: list of values in 0.1 km a.s.l. or formula parameters (see section 7 in WD21_99)
(Optional: Reflectivity threshold: value in 0.1 dBZ )

Notes

• In stratiform rain, the product can be used to determine the height of bright band (melting layer). However, if there is no melting layer, it will show a value inside of an ice cloud. To avoid such problems, an optional threshold could be used (show only product for pixels where maximum intensity is over a dBZ threshold.)
• Rapidly decreasing heights in convective storms may indicate the presence of a microburst.
• The quality of this product depends crucially on number of elevations in the polar volume, even more than in other products, as it is not possible to interpolate the maximum.

Description

Hydrometeor classification products are based on reflectivity and on the dual polarization variables differential reflectivity, specific differential phase, correlation coefficient and the linear depolarization ratio. Dual-channel measurements are used to deduce the types of scatterers present in the atmosphere, such as rain, hail, snow, graupel and even non-meteorological targets such as insects, chaff and clutter.

Parameters

• dBZh , dBZv, ρ hv, φDP, ZDR, LDR

Ratio of velocity of electromagnetic energy in a vacuum to that in a specified medium.

Problems caused to radar products

Insects disperse microwaves. Insect echoes cannot be removed by the Doppler filter because of their moving with wind. Insects can, however, be useful as they provide Doppler wind soundings from clear air boundary layer.

Example Image

A contour of constant Doppler radial velocity.

A radiator which transmits equal energy in all directions.