Observations and operational considerations of the 4 June 2013 chaff event in northern Alabama

Abstract

On 4 June 2013, a military chaff release occurred near Huntsville, Alabama, within the University of Alabama in Huntsville (UAH) mesoscale network. This event was unusual because the chaff remained in the atmosphere-maintaining a radar echo on nearby weather radars-for nearly 10 h after the initial release. This paper examines the radar evolution of the chaff event, supplemented by environmental observations using the UAH profiling equipment. Additionally, unique operational considerations faced by the National Weather Service Weather Forecast Office in Huntsville are addressed.

The WSR-88D Inanimate Hydrometeor Class

“…It is acknowledged that human truthing is a subjective process. While there are relatively few confirmations of chaff releases, for example, subject matter experts were able to discern different target types at maximum likelihood based on previous observations in the literature (e.g., Kurdzo et al 2018;Murphy et al 2016). The same is true for sea clutter.…”

“…IN is most comparable to the DS class in the Z field, with membership values ranging from 3 to 45 dBZ. This is not all inclusive of the IN class, as cases of chaff have been observed at over 60 dBZ (Murphy et al 2016), but it does cover the vast majority of cases. The r hv membership function extends lower than the BI class, but also extends to the top of the range of values.…”

Polarimetric Observations of Chaff Using the WSR-88D Network

“…C HAFF, a military radar countermeasure that consists of metallic fibers cut to specific resonant frequencies, is used to mask aircraft, ships, and missiles from enemy detection [1]. While typically used operationally in the battlefield, chaff releases are common in United States airspace, likely for testing and training purposes (e.g., [2]). Given observations of chaff lengths ranging from 1-20 cm on the ground following releases [2], these metallic dipoles resonate at frequencies easily detectable by the 10-cm wavelength Weather Surveillance Radar -1988 Doppler (WSR-88D) network across the United States [3], [4].…”

“…While typically used operationally in the battlefield, chaff releases are common in United States airspace, likely for testing and training purposes (e.g., [2]). Given observations of chaff lengths ranging from 1-20 cm on the ground following releases [2], these metallic dipoles resonate at frequencies easily detectable by the 10-cm wavelength Weather Surveillance Radar -1988 Doppler (WSR-88D) network across the United States [3], [4]. An example of chaff fibers and clumps is shown in Fig.…”