Casebook 22 September 2003

CSU-CHILL Casebook: 22 September, 2003

RHI scan showing boundary layer

PPI volume scans conducted on 22 September 2003 detected widespread boundary layer echo with a "dumbell" $Z_{dr}$ pattern characterized by maximum positive values of nearly +9 dB that are separated by ~180 degrees in azimuth. (See the first VCHILL example image below.) This $Z_{dr}$ pattern is observed when insects are flying in a preferred direction. The positive $Z_{dr}$ peaks occur when the radar is observing a side view of the insects, giving the largest horizontal / vertical axis length ratio. When the radar is illuminating an end-view of the insects, $Z_{dr}$ values are minimized. The broadside view of the insects also gives a larger backscattering cross section, so reflectivity maxima coincide with the $Z_{dr}$ peaks. The second VCHILL example is an RHI scan that passes through the layered insect echo.

example in VCHILL

example in VCHILL

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