The diagnosis, exploitation, and prediction of electro-magnetic (EM) radiation scatter and refraction in the troposphere impact the success of US Navy and Marine Corps missions that utilize tactical radars and weather radars, which both operate at wavelengths ranging from centimeters to millimeters. For tactical radar systems, the probability of detection as a function of range (including over-the-horizon) of point targets depends on the geometric scattering properties of the target, forward Bragg Scatter from turbulence-induced refractivity fluctuations, attenuation, forward Rayleigh and Mie scattering from clouds, and mean refractivity variations of the troposphere along the EM radiation’s propagation path. Often, strong gradients in humidity and temperature inversions in the marine atmospheric boundary layer trap the EM radiation in ducts, bending it down to graze or reflect-forward, repeatedly, from the surface, carrying it further in range along the surface than in normal propagation conditions. There are research opportunities at NRL to develop and employ inverse methods to derive the refractivity profiles associated with evaporation and surface-based ducts from the sea clutter returns that they cause to appear in Navy shipboard radar surveillance scans, and also to develop methods to assimilate these profiles into the Navy's numerical weather prediction (NWP) models.

The interpretation, geolocation, and exploitation of backscattered and forward scattered radar echoes detected from distributed weather targets (precipitation, cloud, clear-air turbulence) also depend on propagation conditions as well as the underlying assumptions of the scattering processes involved. NRL is engaged in both theoretical and applied research to better understand and optimally assimilate radar-derived weather variables into its diagnostic and predictive systems utilized by the US Armed forces. There are research opportunities to improve our predictions of troposcatter and also develop radar reflectivity-to-water-content parameterizations utilized by the Navy's NWP models, both of which lead to improved tropospheric weather and refractivity awareness and tactical decision aids for the warfighter. In addition, there are research opportunities in process studies to improve our understanding of cloud dynamics and microphysics through the integration of analyses of instrumentation observations with data obtained from the US Navy's unique radar systems, including the Cloud and Precipitation Radar with Discrete Hydrometeor Detection (CPR-HD: 3 MW power; 0.5 m range resolution; aircraft tracking) located at Cape Canaveral, Florida, and a Ka-Band Cloud Doppler radar located at the NRL Coastal Environmental Observation Station (NRL-CEOBS), situated near the Monterey Bay in Watsonville, California.  NRL-CEOBS also has a scanning Doppler Lidar and several other advanced surface sensors and instrumentation for obtaining vertical profiles of clouds and environmental conditions to support research projects. 

 References

Gapp N, et al: "Comparison of concurrent radar and aircraft measurements in Florida Thunderstorm cirrus anvils", Journal of the Atmospheric Sciences, 82 (1): 159-176, 2025.

Harasti PR: "An expanded VVP technique to resolve primary and environmental circulations in hurricanes". Journal of Atmospheric and Oceanic Technology 31 (2): 249-271, 2014.

Schmidt JM, et al: "Radar detection of individual raindrops". Bulletin of the American Meteorological Society 100 (12): 2433-2450, 2019.

key words

Atmospheric refractivity; EM Scattering from clear air and hydrometeors; Radio frequency propagation; Numerical weather prediction; EM propagation modeling; Microwave and mm- wave radar applications; Reflectivity-hydrometeor parameterizations; NWP physics parameterizations; Refractivity retrievals from observations;

Citizenship:  Open to U.S. citizens and permanent residents

Level:  Open to Postdoctoral applicants

Additional Benefits

Relocation

Awardees who reside more than 50 miles from their host laboratory and remain on tenure for at least six months are eligible for paid relocation to within the vicinity of their host laboratory.

Health insurance

A group health insurance program is available to awardees and their qualifying dependents in the United States.