Design considerations for a dual-frequency radar for sea spray measurement in hurricanes

Abstract

Over the last few years, researchers have determined that sea spray from breaking waves can have a large effect on the magnitude and distribution of the air-sea energy flux at hurricane-force wind speeds. Characterizing the fluxes requires estimates of the height-dependent droplet size distribution (DSD). Currently, the few available measurements have been acquired with spectrometer probes, which can provide only flight-level measurements. As such, in-situ measurement of near-surface droplet fluxes in hurricanes with these instruments is, at best, extremely challenging, if at all possible. This paper describes an airborne dual-wavelength radar profiler concept to retrieve the DSD of sea spray.

A Motion-Stabilized W-Band Radar for Shipboard Observations of Marine Boundary-Layer Clouds

“…The measured backscattered reflectivity profiles are coupled with the drop size distribution estimates in a manner similar to Esteban-Fernandez et al (2010). Larger particles have relatively high concentrations near the surface that decrease with altitude.…”

“…where λ is the radar wavelength (m), L SY S is the system losses including matched filter loss (see Doviak and Zrnic 1993), P T is the peak transmitted power (milliwatts), G is the antenna one way gain-includes radome loss, φ = beamwidth (radians), θ = beamwidth (radians), R = range cell depth (m), K is the complex index of refraction for water, k is the Boltzman's constant, T O P is the radar receiver's operating temperature in K, B N E is the noise equivalent bandwidth of the of the receiver in Hz, SNR min is the threshold of signal-to-noise ratio for detectable signals and MDS is in units of milliwatts.…”

An observation of sea‐spray microphysics by airborne Doppler radar

“…Lidar have some potential [Toffoli et al, 2011], but rely on a clear-air line of sight to the surface and may be too sensitive to more abundant small aerosols. Airborne millimeter-wavelength radar offers an attractive option for such measurements [Esteban-Fernandez et al, 2010;Yurovsky and Malinovsky, 2012]. Compared to conventional centimeter-wavelength radars, they offer advantages in greater sensitivity to sea-spray droplet sizes, finer vertical resolution, and faster sample rates.…”

Radar backscattering from sea foam and spray

“…Recent remote sensing experiments [1, 2,3,4,5] show that breaking waves can significantly change radar backscattering from the sea surface due to contributions of water droplets (spray) and air bubbles (foam/whitecap). It is assumed that volume scattering from the near-surface seawater particles plays an important role in the radar backscattering from the sea surface at high wind speeds.…”