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COAMPS®Refractivity and EM Propagation
Analysis and Prediction

Project Description

The goals of this research are to provide accurate mesoscale analyses and forecasts of microwave refractivity (M), and to quantify the impacts of refractive effects upon Naval communications and weapons systems. Such refractive effects are of particular importance to strike warfare, ship self-defense, special operations, and potentially to directed energy capabilities. The objectives of this research are to enhance numerical weather prediction approaches to analyzing (nowcasting) and forecasting microwave refractivity and the concomitant refractive effects upon Naval combat systems and communications. The approach used is multifaceted and multi-disciplined. The Navy�s Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS ®)[1] is applied with high horizontal and vertical resolution to analyze and forecast refractivity structure. Further, COAMPS provides background fields for implementing data fusion techniques to improve refractivity analyses and for inversion techniques such as used in extracting Refractivity-From-Clutter (RFC). To refine and validate this approach, datasets from several field experiments, some including special electromagnetic (EM) propagation data, have been exploited.

Figure 1. Schematic of a modified refractivity (M) profile
labeled with key parameters that affect EM propagation.

Figure 1 displays a schematic that defines the terminology and key parameters associated with a profile of modified refractivity for a typical marine boundary layer. Modified refractivity increases with height except in trapping layers for which the gradient in M is negative. The difference between M at the top (Mmin) and bottom (Mmax) of the trapping layer yields the duct strength. The duct thickness and duct base height are determined by sampling the M profile below the top of the trapping layer to find the height where M equals Mmin. The evaporation duct height is a surface-based duct that typically forms over water and is given by the height where M first begins to increase. �

The above graphic is an example of the 9-km horizontal resolution COAMPS forecast of boundary layer structure near Wallops Island, VA (red asterisk) on the afternoon of 25 April 2000.� The horizontal plane is color shading of ground temperature overlaid with near-surface wind arrows.� White �clouds� indicate the 3D spatial distribution of the EM trapping residing primarily over inland waterways and the colder coastal sea surface temperatures. �The cross-section extending perpendicular to the coast shows the vertical gradient of M (dM/dz) in color and potential temperature contours. �EM trapping layers occur as the vertical gradient of water vapor is sharpened due to subsidence.� In the cross-section, these layers are represented by blue colors while red colors indicate subrefractive regions for which EM energy is lost to the free atmosphere, creating �radar holes�. �

Contact Information

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Technical Lead

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Naval Research Laboratory
Marine Meteorology Division
7 Grace Hopper Ave, Stop #2
Monterey, CA 93943-5502

 

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Research and Results

Regional Studies

Field Programs

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Publications

 


Burk, S.D., T. Haack, L.T. Rogers, and L.J. Wagner, 2003: Island wake dynamics and wake influence on the evaporation duct and radar propagation. J. Appl. Meteor., 42, 349-367.
 
Burk, S.D. and T. Haack, 2003: Refractivity in the coastal atmospheric boundary layer.� Fifth Conf. Coastal Atmos. & Oceanic Pred. & Proc., Seattle, WA, 147-150.
 
Burk, S.D. and T. Haack, 2003: Refractivity in the coastal atmospheric boundary layer. BACIMO, Monterey, CA, online.
 
Burk, S. D. and T. Haack, 2004: A mesoscale modeling study of Wallops 2000 EM refractivity conditions. Proceedings, National Radio Science Meeting, 20-25 June, Monterey, CA.
 
Burk, S, T. Haack, R. Marshall, E. Burgess, R. Rottier, K. Davidson, and P. Fredrickson, 2005: Coastal EM refractivity conditions: an observational and mesoscale modeling study. NRL Review, 2005.
 
Burk, S.D. and T. Haack, 2005: Coastal atmospheric boundary layer impacts on refractivity and EM propagation. 6th Coastal Conf., San Diego, CDRom
 
Haack, T. and S.D. Burk, 2001: Summertime marine refractivity conditions along coastal California.� J. Appl. Meteor., 40, 673-687.
 
Haack, T. and S.D. Burk, 2003: Seasonal variability of refractivity conditions along the U.S. West Coast: A comparison of monthly averaged ducting properties. BACIMO, Monterey, CA, online.
 
Haack, T. and S. D. Burk, 2004: Coastal and seasonal variability of marine layer electromagnetic trapping conditions. Proceedings, National Radio Science Meeting, 20-25 June, Monterey, CA.
 
Haack, T. and S. D. Burk, 2005: Ducting and electromagnetic propagation around the Korean Peninsula. �Proceedings, BACIMO 2005, 12-14 October, Monterey, CA.
 
Haack, T. and S. D. Burk, 2005: Synoptic, mesoscale, and diurnal impacts on EM trapping conditions. Proceedings, National Radio Science Meeting, 5-8 January, Boulder, CO
 
Thompson, W. T., S. D. Burk, M. C. Jablecki, and L. T. Rogers, 2005: Evaluation of a new approach to microwave refractivity analysis. Proceedings, BACIMO 2005, 12-14 October, Monterey, CA.
 

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Last revised: 6 October 2005

 


[1] COAMPS® is a registered trademark of the Naval Research Laboratory.�

 

  Approved for public release by Superintendent. NRL Address: Naval Research Laboratory Marine Meteorology Division 7 Grace Hopper Avenue, Stop 2 Monterey, CA 93943-5502 831-656-4721/4758

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