Abstract
We computed the monthly average backscattered power over a five-year period for the Fleming 50 MHz wind profiler, which is proportional to CN2. We found that in addition to seasonal cycle in CN2 below the tropopause, there was a year-to-year variation as well. Above the tropopause, the seasonal variations were almost gone; however, there were significant changes with periods longer than one year. We examined a shorter back-scattered power record from the Stapleton wind profiler and found similar longer-term trends. These long-term trends will affect the performance of wind profilers.
