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Sun Strobes

Sun strobes occur when a radar antenna points directly at the sun. The antenna receives a massive dose of electromagnetic radiation, read by radar as high density and shown as high reflectivity for one or two radials. The NEXRAD data collected at CUROL represent scans of the lowest elevation angle (0.5 degrees) for the radar, so sun strobes appear only when the sun is rising and setting. In reflectivity images sun strobes are apparent as bright colored spikes, while in velocity images they are apparent as purple spikes (range folding). The position of sun strobes on a radar image changes daily through the year as the path of the sun changes.

NEXRAD reflectivity scan showing large precipitation event

dBZ Precip
(mm/hr)

ND

05

10

15

20 0

25 1

30 2

35 5

40 12

45 28

50 63

55 144

60 328

65 747

70 1701

75 3871

national mosaic showing sun strobe

NEXRAD Mosaic 2 km
Elev=0.5 deg
1 km²/pixel
MidWest U.S,
~41N:103W - 32N:93W
03/27/00 00:50 UTC
Precip Mode
VCP -----
Max: 74 dBz

The appearance of the sunset strobe can indicate that migration is about to begin.
Initiation of exodus at Greer, SC

dBZ Birds
/km³

ND

-28

-24

-20

-16

-12

-8

-4

0

4 58

8 65

12 81

16 123

20 227

24 489

28 1148

NEXRAD bird exodus
(C) 1999 weatherTAP.com

Radial Vel 124nm
Elev=0.5 deg1 pixel=1 km²
Greer SC
34.88N 82.22W
09/12/99 23:34
to
09/13/99 00:52
Clear Mode
VCP 32
Max: 55 dBz

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