Project # 2005-135 RICO Rain In Cumulus over the Ocean Principal Investigator(s):  Bob Rauber, Harry Ochs, et al. NSF/NCAR C-130Q Hercules (N130AR)

C-130Q - Selected Instrument Uncertainties

Selected Instrument Uncertainties:

Uncertainties for selected C-130 RICO project data were compiled in response to a researchers request and are repeated here for future reference.

ATX: We recommend using ± 0.5 C for the temperature outside of cloud for the ATRR, the unheated fast response Rosemount sensor. In cloud the sensor may become wet and the unheated fast response sensor data should not be trusted in cloud. In that case the heated probe data should be used, but its accuracy is ± 1.0 C.

MRLA: I am quoting Dr. Stuart Beaton, the instrument designer. The accuracy of the UV hygrometer is hard to define because of the way the data is processed - drift and air density effects are removed by what we call a loose-coupling algorithm which forces the UV mixing ratio (and dew-point) to that of the reference chilled mirror hygrometers. So the UV hygrometer data is intended to be used for fast water vapor changes which cannot be tracked by the chilled mirror dew-pointers. Also, the uncertainty will depend on the absorption pathlength that is set at the beginning of the project. For Rico it was a short pathlength, appropriate for mixing ratios of about 2 - 15 g/kg near sea level, or roughly above -30 C dew-point. With this setup we have seen typical uncertainty of ± 2% (in mixing ratio) for a dew-point down to about -10 C. Below that the uncertainty will increase as the signal starts to be lost in the noise.

XGLWC: Channel 1, 5%; Channel 2: 5%; Channel 3: 10% (http://www.gerberscience.com/pvmaspecs.html)

PSXC: The reference sensor is Rosemount 1501. The sensor accuracy is +- 0.042% of full scale, or +-0.42 mbar (as described in http://www.eol.ucar.edu/raf/Bulletins/bulletin21.html). Flight data accuracy, which includes corrections for dynamic pressure, is +-1 mbar.

GGALTC: Generally the accuracy of the GPS altitude is quoted at 15 m. We have more than one altitude data source and for RICO, this also included a highly accurate differential GPS system. Using it as a reference, the one sigma of GGALTC - H-MSL is about 5m, giving a confidence band of 13.3 m at the 95% level during straight and level flight (this figure varies somewhat from flight segment to flight segment but remains in this general range and is consistent with the single band GPS at 15 m). If you were to use the actual H-MSL or H-CORR from the differential GPS data, the accuracy of that is +- 15-20 cm.