NSA/CEIL/C1 - Degraded window

The ceilometer continuously gave warnings for window contamination because the window had 
deteriorated. Cloud base height detection did not appear to be significantly affected. 
The window conditioner was replaced on 8/11/09 but this did not clear the warning. The 
instrument was replaced.

• window_contamination
• first_cbh
• alt_highest_signal
• background_light
• status_flag
• second_cbh
• backscatter
• status_string
• vertical_visibility
• sum_backscatter
• third_cbh