1. A Futile Comparison of the Refractive Conditions in the Monterey Bay

2. Purpose
Compare refractive profiles from Rawinsonde Data, Helvey Predictions and ETA Upper Air Data.
Determine if model data can provide similar predictions capabilities as rawinsonde data.

3. Why is this any issue? COST !!!
New sondes less reliable.
GPS costs 2X the amount of old sondes
Old sondes (omega) do not provide upper level winds
Mesoscale model availability and quality (Theory, Correct or just Bunk)

4. Rawinsonde Data 21 Profiles (Normal and up/down launches were used)
6 up/down (both profiles showed same results, only kept one profile)
15 Cases remained.
Data considered to be truth.
7/15 profiles showed ducting conditions

5. Method of Collection
% Time AscRate Hgt9MSL Pressure Temp RH Dewp Dir Speed WndStat
min s m9s m hPa degC % degC deg m9s

6. Helvey Predictions
Algorithms used to predict the formation of a duct based on many meteorological conditions:
MSL pressure, curvature of nearest isobar, distance to closest High, distance to closest front, location(Atlantic and Pacific), wind direction, evidence of inversion, surface air temperature, sea surface temperature, proximity to land, seabreeze regime, presence of low level moisture, presence of stratus, cloud types, base heights and coverage.
Web based

7. Helvey Predictions (cont.)
4 Possible Categories:
UNLIKELY
POSSIBLE
PROBABLE
VERY LIKELY
For cases where ducting is expected a level for the base of the duct is provided.
If there is a duct, expect the base at
0. meters ( 0. feet).
No Duct
Duct

8. ETA Model 39 Vertical levels Analysis every 6 hours
Used analysis from time period closest to launch time at lat/long of launch location.

9. ETA Data
LEVEL HGHT TEMP DWPT WDIR WSPD OMEG

10. Presence of Duct

11. Duct Level

12. Duct Present Duct Not Present
Predictions
Duct Present Duct Not Present
(Rawinsonde)
0/7
0/5
Duct Not Present Duct Present
(Models)
7/0
8/3
Blue = ETA
RED = Helvey

13. Conclusions Radiosondes and ETA
Radiosondes are still the best method for retrieving refractive conditions
Model output does not have the required vertical resolution and many models are smoothed for customers.
Model does not always contain surface effects (model started at 100 m above surface).
few observations are found so meso or microscale features are not resolved.

14. Conclusions Helvey
Helvey predictions are well suited for very stable or very unstable conditions.
Results questionable when conditions are neutral or slightly stable/unstable.
Duct height predictions are unreliable at any time.

15. Questions
Questions
GO SONDES !!