1. LT Tom Moneymaker Advisor: Prof Peter Guest
Comparison of Measured Evaporative Duct Height to the Bulk Model in Coastal Regions
LT Tom Moneymaker
Advisor: Prof Peter Guest

2. Outline Why? Background Procedures Data Analysis Conclusions
Background: Talk about the different Duct, the Evaporative Duct Height, and the Bulk model
Procedures: How we collected the data and what data was used.
Data Analysis: Compare the data to the model.

3. Why? It is related to my thesis EM background at MET San Diego
Significant operational applications
How available is METOC data
Modern tactical concern
Mandatory to do a brief for this class

4. Background (Ducting) Height (m) M 300 200 100 Elevated Duct
Surface-based
Duct
Height (m)
Radar propagation in the atmosphere is dependent on the vertical gradient of the modified index of refraction, M (or modified refractivity).
M is a function of pressure (p), temperature (T), and the partial pressure of water vapor (e).
There are 3 Ducts that the Navy focuses on.
The Elevated Duct, Surface Based Duct, Evaporation Duct.
While I was stationed on the MET in San Diego about the USS SHILOH find these Duct’s were a big part of my day.
But the think down there was that If you had a SURFACE BASED DUCT THAT YOU WOULDN’T need to worry about the EVAPORTION DUCT b b/c the Surface based duct was so storg but it turns out that the Evap Duct actually helps fill holes of coverage from the SURFACE BASED DUCT
Evaporation Duct M

5. Propagation Loss for Radar Within Evaporation Duct
Duct Ht = 65 ft, 55 ft
Evaporation ducting greatly increases radar frequency propagation distances in relation to standard atmosphere propagation distance.
Greatly Increased Detection Ranges Possible
Duct

6. Background (Evaporation Duct)15 10 5 Z*
Height (m)
Evap
Duct
The level at which dM/dz = 0 is the evaporation duct height.
M is a function of pressure, air temperature and vapor pressure (the latter derived from relative humidity and air temperature)
Most operational situations do not allow for direct profile measurements of e, T and p, and therefore M.
In these cases the use of bulk methods are used to estimate the profiles M
RH (%)

7. Model: Monin Obukhov Scaling
profiles with bulk model:
Monin-Obukhov scaling parameters are determined by measurements at two levels, the surface and an arbitrary reference height (z) within 20 meters of the surface.
Specific parameters are the sea surface temperature (SST), an assumed sea surface humidity of 98% and reference height temperature (Tair), humidity and wind speed.

8. Background (Rel Humidity –vs- True Winds)
the predicted EDH is influenced primarily by air–surface humidity (RH) and wind speed for an unstable atmosphere
Tair- SST value and wind speed for stable conditions.

9. Procedures Collect kite data and boat data
Massaged the data so as to get rid of the dirty data.
Run the data to get M profile
Compare kite data to bulk method

10. Kite-borne Radiosonde
R/V Point Sur’s UDAS system
17 meters from the sea surface
Three independent systems measured the atmospheric parameters needed to calculate M in-situ and to derive M profiles using bulk methods. R/V Point Sur’s UDAS was used to obtain air temperature, wind speed, relative humidity, pressure and sea surface temperature.
All of the instruments (except the sea surface boom probe) were mounted 17 meters from the sea surface.
The NPS designed a kite-borne radiosonde system, aimed at measuring the atmospheric surface layer, from near surface (1 meter) up to approximately 100 meters.
The sonde can be attached to the kite and measures vertical profiles of pressure, temperature and vapor pressure, the determining parameters for EM propagation, in two-second intervals.

11. Prof P. Guest A.F. NAVY Program assumes height based on press
Negative heights not possible
Modify based on in-situ height and time recordings (purple line)
Purple line indicates where One meter above the sea surface would be.
The Blue down ward spikes indicate where the kite sonde got down to.
So the purple line was based off of the measured heights that we took that day and then added onto the end of the blue spike to give the purple line.

12. Method and Manipulation
Bad data
Select bad data (purple)
Ship influence
Readings prior to launch
Kite dipping
Green is ship data
Difference in press, temp and RH

13. Bad Data Edited
Averaging periods determined by subjective temp and RH values

14. Method and Manipulation
Select interval average based on similar airmass characteristics
Fairall’s Bulk Method derived Pot Temp, RH and M profile
(black line)
Mean kite data over interval (lavender circles)

15. Method and Manipulation
Select interval average based on similar airmass characteristics
Fairall’s Bulk Method derived Pot Temp, RH and M profile
(black line)
Mean kite data over interval (lavender circles)