Birds at Sunrise
Another aspect of the sensitivity of the WSR-88D Doppler radar is its ability to detect non weather related objects. One of those objects is birds. While detecting birds as individuals is not a problem, large flocks of birds can be detected. This is especially true on quiet mornings when atmospheric conditions deflect the radar beam to slightly lower elevations and large flocks of birds begin to disperse from nighttime nesting areas.
One of these areas is apparently is in eastern Grundy county just south and east of the town of Morris. As series of small lakes and a wildlife refuge attracts birds for their nighttime lodging. The two images in this sequence were taken with different detection schemes but show the same thing.
About 640AM on February 19, 1998 this bird dispersion was seen as a circular return southwest of the radar site. The circle expands and fades as the individual birds fan away from the nesting site.
On December 13, 1998 at 7AM another occurrence was captured. This time the radar mode was more sensitive which is reflected in added detail and color scheme. Both images reveal the same phenomena from the same location. The type of bird involved here is unknown.
Bird returns also pose a serious contamination problem when we use the radar to estimate winds aloft. The radar sees the birds as a target and factors in their movement into the wind calculation. The main migration of birds occurs at night so during the spring and autumn this problem makes nocturnal use of Doppler winds highly questionable.