Two Parameter Launch Rule

1. Two Parameter Launch Rule Douglas Mach May 12, 2003

2. Why Use a Two Parameter Rule? • A single parameter rule may not cover all possible cases of electrification • A single parameter rule may cover all possible cases of electrification, but may require significantly lower thresholds • Two parameters may better model electrification • Ice/liquid water + updrafts + ? = electrification • Fields @ aircraft  electrification @ aircraft + bigger electrification near aircraft • Each of the two parameters may be set at higher thresholds than when used individually • Current rules are a “multi-parameter” set

3. Two Parameter Rule Idea

4. Example Rule from ABFM-1 • Do not launch if the VSR0C along and 0.5 nm either side of the flight path is greater than 20 or if there is VIL0C greater than 30 within 10 nm of the flight path • Takes care of 2 problems: • Electrification along path • Electrification near path

5. Limited set of radar parameters dBZ at aircraft Column Sum @ 1x1x(0°C - up) Count in 11x11x(0°C - up) Average dBZ in 11x11x(0°C - up) Sdev dBZ in 11x11x(0°C - up) Skew dBZ in 11x11x(0°C - up) Maximum dBZ in 11x11x(0°C - up) Count in 21x21x(0°C - up) Average dBZ in 21x21x(0°C - up) Sdev dBZ in 21x21x(0°C - up) Skew dBZ in 21x21x(0°C - up) Maximum dBZ in 21x21x(0°C - up) Average dBZ in Cube 3x3x3 Sdev dBZ in Cube 3x3 Parameters Derived from Current ABFM Merged Data

6. Study Data Set • Choose a limited set of data • Filtered for ‘problems’ (will discuss later) • WSR88D data only • Minimize attenuation problems • Minimize scan gap problems • Will use both pre-defined and derived parameters

7. Unfiltered Filtered Example Data(Avg21x21)

8. ‘New’ Parameter • Wanted to create a parameter as close toVSR0C as possible using data available on website • Wanted a parameter that was easy to detect ‘no data’ • Parameter start at 0 [arbitrary units] • Wanted a parameter that indicated the TOTAL amount of cloud material (not just the average over a volume)

9. Offset Total dBZ • Start with average dBZ • Avg21x21 • Avg11x11 • Multiply by # of bins used in the average • num21x21 • num11x11 • Offset each bin value by 10 dBZ (minimum value of -10 dBZ) • + 10*num21x21 • + 10*num11x11 • Measures total reflectivity in the 11x11 or 21x21 volume • OTdBZ21x21 = (Avg21x21 + 10)*num21x21 • OTdBZ11x11 = (Avg11x11 + 10)*num11x11

10. OTdBZ11x11 OTdBZ21x21 Example OTdBZ

11. Results Presentation Table

12. Example Single Parameter(Avg21x21, threshold = 5)

13. Single Parameter Example 2OTdBZ11x11, threshold = 0.4x104

14. Two Parameter ExampleOTdBZ11x11, threshold 0.54x104OTdBZ21x21, threshold 2.05x104

15. Counter Example(single parameter)OTdBZ21x21, threshold 2.0x104

16. Conclusions • Two parameter rule improves on some of the single parameter rule examples • ‘Best’ rule using filtered data and data derived from web available parameters (OTdBZ21x21) does better than any examined combination • Web available parameters are all very close to each other • OTdBZ21x21 is a ‘summary’ of all other parameters

17. Bonus Presentation Filtering Merged Data

18. Problems with Some Merged Data • When looking at radar parameters vs. electric field, most days had very intuitive patterns…

19. Problems with Some Merged Data • Other days had odd patterns…

20. Problems with Some Merged Data • Examination of the data shows…

21. Problems with Some Merged Data • Other examples:

22. Conclusions • Simply plotting E vs. any radar parameter using the merged data will often show periods when the radar parameter is artificially low • This will result in ‘overly’ conservative rule suggestions • For example: OTdBZ21x21 is very sensitive to radar scan gaps • What to do about it?