DA10 measures water vapor profiles from 50 m (164 ft) to the top of the boundary layer (max. 4000 m (13 000 ft) or cloud base height – whichever is lower. Profiles are reported at 9.6 m (31 ft 6 in) height intervals. The quality-controlled, maximum valid measurement range is reported with each profile.
The measurement is based on the differential absorption observed between the attenuated backscatter profiles at online and offline wavelengths of water vapor absorption. The unit for the reported water vapor mixing ratio is gram of water vapor per kilogram of dry air (g kg-1).
The measurement data is processed in real time and a water vapor profile is generated every minute based on the data collected during the previous 20 minutes (default). Averaging time can be adjusted to 10–60 minutes (available later). The profile timestamp indicates the end of the data collection period.
The online and offline profiles are vertically averaged before water vapor retrieval using Gaussian-like weighting functions, starting from the fine resolution near the ground and from the coarser resolution at higher altitudes. The resulting vertical resolution of the water vapor profiles is 100 m at 200 m height above ground level (AGL) (328 ft at 656 ft), 220 m at 1000 m AGL (722 ft at 3280 ft), and 500 m at 3000 m AGL (1640 ft at 9840 ft) (full width at half-maximum of weighting functions).
The reported profiles are combinations of the measured profiles from the near-range measurement unit and the far-range measurement unit. The measurement algorithm adjusts the transition from the near-range to the far-range adaptively based on the signal-to-noise ratio to optimize the result. The transition region is typically between 427 m and 477 m (1401 ft and 1565 ft).
The following figure shows an example of the water vapor profile. The 1-dimensional profile is taken from within a 20-minute period contained in the 2-dimensional data displayed in Figure 1. The horizontal dashed line shows the maximum valid measurement range. The dotted lines show the lower and upper limits of uncertainty, computed as the difference and the sum of the water vapor profile and the uncertainty profile.