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The algorithm used to detect PSCs in POAM II measurements is based on retrieved aerosol extinction profiles at 1060 nm. PSCs affect the extinction profiles in one of two ways.
1. The cloud is manifested as a layer of enhanced extinction, relative to
expected background atmospheric conditions.
2. The cloud may be sufficiently opaque that POAM cannot scan
through it, which means that the cloud top effectively represents the earth's
horizon from POAM's point of view. This cloud is manifested in the POAM
profile as an abnormally high minimum retrieval altitude.
The POAM PSC detection algorithm uses a threshold technique to determine if there is sufficiently enhanced extinction or high minimum profile altitude exists to identify a PSC. The northern hemisphere winter seasons of 1994/1995 and 1995/1996 and the southern hemisphere winters of 1994-1996 are in the POAM PSC data set. These data are very useful for studying PSC occurrence in temporal, horizontal, and vertical extent. Some of these characteristics are illustrated in the images shown below.
Figure 1. Polar map of POAM II northern hemisphere measurement locations and PSCs.
A. 1994/1995
B. 1995/1996
Figure 2. Polar map of POAM II southern hemisphere measurement locations and PSCs.
A. 1994
B. 1995
C. 1996
Figure 3. Histogram of percent frequency occurrence of Arctic POAM II PSCs by month during the PSC seasons of 1994/1995 and 1995/1996. The parenthetical numbers next to each month label is the mid-month latitude of POAM II observations for that particular month.
Figure 4. Histogram of percent frequency occurrence of Antarctic POAM II PSCs by month during the PSC seasons of 1994 - 1996. The parenthetical numbers next to each month label is the mid-month latitude of POAM II observations for that particular month.
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