Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/15/1998
Publication Date: N/A
Interpretive Summary: A new national network (NEXRAD) of weather radars can detect the amount of precipitation and storm movement. The doppler weather radars can also detect insects, birds, and bats, but cannot yet discriminate them from precipitation. A study was conducted in south-central Texas to determine the effect of flying insects on doppler weather radar reflectivity and velocity during episodes of peak insect migration. Higher concentrations of flying insects in clear air were associated with increased radar reflectivity. Clear-air radar reflectivity during peak insect migrations often falsely indicated light to moderate precipitation. Radar-estimated wind speeds deviated from measured wind speeds within a range that could be attributed to insect flight speed. These results suggest that the NEXRAD network of radars has good potential for providing agriculturally-useful information about pest insect migratory flights over large areas.
Technical Abstract: Targets such as flying insects, birds, and bats obscure the measurement of radar reflectivity and doppler velocity by weather radars. This study was conducted to determine the relationship of the concentration and velocity of adult bollworms, Helicoverpa zea (Boddie), and other similar-size targets with the base reflectivity and doppler velocity measured by the NEXRAD network of WSR-88D doppler weather radars. Relationships between entomological radar data, pilot balloon wind profile data, and WSR-88D reflectivity and doppler velocity data were investigated in the Lower Rio Grande Valley near the WSR-88D at Brownsville, Texas, and near the WSR-88D at New Braunfels, Texas, in the spring and summer of 1995 and 1996. Clear- air radar reflectivity often exceeded 4 dBZ, the lower reflectivity threshold on the WSR-88D radar display for precipitation-tracking mode. WSR-88D reflectivity was significantly correlated with the aerial concentration of adult bollworm-size targets. Doppler velocity was significantly correlated with the radial component of wind velocity, but the target velocity contributed to a mean bias of as much as 2.7 m/s. These results indicate that information about the local population dynamics and identity of migratory nocturnal insects can increase the accuracy of reflectivity and velocity measurements by WSR-88D radars, and lead to the development of algorithms which estimate the migratory flux of bollworms and other nocturnal insects.