Data quality and data availability - DA10

DA10 User Guide

Document code
M212895EN
Revision
D
ft:locale
en-US
Product
DA10
Document type
User guide

To ensure eye-safe operation, the transmitted laser power is limited, which results in backscattered signal levels below the noise of the ambient daylight. To counteract this, a large number of laser pulses are sent, and the returns are summed. During this process, the random noise partially cancels itself. The water vapor measurement requires much longer averaging times and more vertical averaging compared to the attenuated backscatter measurement, and signal analysis to filter out any outliers from solid targets such as insects or birds.

The water vapor data quality and data availability depend mostly on the atmospheric scatterer concentration and the height of the boundary layer, as well as cloud conditions. Vaisala software analyzes the backscatter signal levels and selects the maximum valid measurement range depending on the atmospheric conditions. Occasionally, moderate precipitation from high clouds, or aerosol layers above the boundary layer, can extend the observed profile.

The output files always report water vapor profiles up to 4000 m (13 000 ft). The netCDF file variable water_vapor_max_range indicates the maximum acceptable measurement range for each water vapor profile, as determined by Vaisala software. Values above this range must be discarded and/or clearly indicated in visualizations.

The default averaging time of 20 min can be adjusted (available later) if local conditions require, for example, if the boundary layer is very clean with very few scatterers. The vertically increasing smoothing maintains a more consistent measurement quality as the signal levels decrease with height. Due to the characteristics of the retrieval process, low signal levels do not show as random noise in the water vapor profile - rather, the profile shape may have small oscillations.

Additional information on data quality can be obtained from the measurement uncertainty estimate.

For details about the data quality reporting, see information about the netCDF format.