Distance Learning Operations Course, Topic 3 Lesson 1 -- Section 6-6: Pulse Repetition Interval Characteristics

Table of Contents

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Introduction and
Objectives

1. Radar Fundamentals

2. Radar Equation and
Reflectivity

3. PRF, Rmax, and Vmax

4. Range Issues

5. Radar Beam
Characteristics

6. WSR-88D Data
Collection

Long Pulse Mode
Resolutions

Clear Air Returns

Data Collection
Operations

Sampling Techniques

VCP Characteristics

Pulse Repetition
Intervals

VCP Comparison

Practice Exercise #6

References

VCP Comparison

As with many characteristics of radar data, individual VCPs have strengths and limitations. Stemming from the strengths and limitions are meteorological situations when tha applicatoin of a certain VCP would be warranted. Use this to review each VCP, or as a handy reference guide at your local office. This comparison table is available in PDF format, and contains more detailed information on each VCP than presented in the table below.

Tilts / Time	VCP	Description	Usage	Limitations
14 in ~5 mins	11	Legacy	Severe and non-severe convective events. Local 11 has Rmax=80nm. Remote 11 has Rmax=94nm.	Fewer low elevation angles make this VCP less effective for long-range detection of storm features when compared to VCPs 12 and 212
14 in ~5 mins	211	SZ-2	Widespread precipitation events with embedded, severe convective activity (e.g. MCS, hurricane). Significantly reduces range-obscured V/SW data when compared to VCP 11.	All Bins clutter suppression is NOT recommended. PRFs are not editable for SZ-2 (Split Cut) tilts.
14 in ~4 ½ mins	12	Faster Updates, better vertical converage	Severe convective events. Extra low elevation angles increase low-level vertical resolution when compared to VCP 11.	High antenna rotation rates slightly accuracy of the base data estimates.
14 in ~4 ½ mins	212	SZ-2	Rapidly evolving, widespread severe convective events (e.g. squall line, MCS). Increased low-level vertical resolution compared to VCP 11. Significantly reduces range-obscured V/SW data when compared to VCP 12.	All Bins clutter suppression is NOT recommended. PRFs are not editable for SZ-2 (Split Cut) tilts. High antenna rotation rates slightly decrease accuracy of the base data estimates.
9 in ~6 mins	21	Legacy	Non-severe convective precipitation events. Local 21 has Rmax=80nm. Remote 21 has Rmax=94nm.	Gaps in coverage above 5°, 6 min updates.
	121	SZ-2, MPDA	VCP of choice for hurricanes. Widespread stratiform precipitation events. Significantly reduces range-obscured V/SW data when compared to other VCPs.	All Bins clutter supression isNOT recommended. High antenna rotation rates slightly decrease accuracy of the base data estimates. PRFs are not editable. Gaps in coverage above 5°.
	221	SZ-2	Widespread precipitation events with embedded, possibly severe convective activity (e.g. MCS, hurricane). Further reduces range-obscured V/SW data when compared to VCP 121.	All Bins clutter suppression is NOT recommended. PRFs are not editable for SZ-2 (Split Cut) tilts. Gaps in coverage above 5°.
5 in ~10 mins	31	Long Pulse	Clear-air, snow, and light stratiform precipitation. Best sensitivity. Detailed boundary layer structure often evident.	Susceptible to velocity dealiasing failures. No coverage above 5°. Rapidly developing convective echoes aloft might be missed.
5 in ~10 mins	32	Short Pulse	Clear-air, snow, and light stratiform precipitation.	No coverage above 5°. Rapidly developing convective echoes aloft might be missed.

Next Page: Practice Exercise #6
or look at: References