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Bats

   Bats emerging from roost sites show up on NEXRAD near dusk as crescents or rings of reflectors with high dBZ values. Because bats can sustain powered flight for long periods of time, their radial velocity will usually be different than that of insects or particulates in the atmosphere. The following images from the evening of 23 October, 1999 at DLF Laughlin, TX show bats departing from roost sites. There may be as many as 7 roosts of bats, visible as crescents to the north, south and east of the radar. Notice in the velocity image that to the north of the station, bats are moving north into a northerly wind - a clear indication of powered flight. The presence of expanding rings or crescents and above-windspeed flight at or near dusk are characteristics of bat emergence.

Bats detected by NEXRADBats flying in spirals against the wind
dBZ
ND
05
10
15
20
25
30
35
40
45
50
55
60
65
70
75
 base reflectivity image of bats base velocity image of bats
kts.
ND
-64
-50
-36
-26
-20
-10
-1
0
10
20
26
36
50
64
RF
DLF: Laughlin TX (29.27N 100.3W):
Base Ref 124nm / Elev=0.5 deg / 1 km²/pixel
Precip Mode / VCP 21
10/23/99 01:16 UTC - Max: 58 dBZ 		DLF: Laughlin TX (29.27N 100.3W):
Radial Vel 124nm / Elev=0.5 deg / 1 km²/pixel
Precip Mode / VCP 21
10/23/99 01:16 UTC - Max: -59 kts +54 kts

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