Project # 2007-506 PACDEX

PACific Dust EXperiment

Principal Investigator(s):  Jeffrey L. Stith, et al.

NSF/NCAR Gulfstream V (N677F)

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Data Quality Report

Prepared by:   Pavel Romashkin (NCAR/RAF)

The following report covers only the RAF supplied instrumentation and is organized into two sections.   Section I lists recurring problems, general limitations, and systematic biases in the standard RAF measurements.   Section II lists isolated problems occurring on a flight-by-flight basis.   A discussion of the performance of the SABL lidar, TDL hygrometer and RAF chemistry sensors will be provided separately, as will their respective data sets.

(Please note that the original report had three sections. The first two of them were made into separate web pages:

Aircraft Instrumentation (includes sensor discussion and recommendations)
Summary of Calibration Factors.

Section I:  General Discussion

  1. There are interruptions in the data system recording when the GV crosses the UTC midnight.  These interruptions may be as long as 5 minutes.

  2. DPRS, DPLS, DPRC, DPLC: dewpointers tend to overshoot and oscillate after rapid temperature increase on aircraft descents.  Using best judgment, these overshoots are removed from DPXC but are left in DPLC, which is the source variable for DPXC, for comparison.

  3. LONC, LATC deviate where there is the 5-minute interruption in data after midnight on all flights crossing UTC midnight.  It is recommended that direct GPS position is used in referencing the data (GGLAT, GGLON, GGALT).

  4. Vertical wind speed (WIC) can deviate on steep climbs and descents.   This is due to imperfections in the calculation algorithm.

  5. PLWC (King probe liquid water content) was part of the project but did not operate properly due to a hardware problem.  The instrument did not respond correctly to changing airflow and did not output proper background signal.  Although there is response from the instrument to the liquid water in clouds, it is not quantitative.  Use CDP liquid water instead (PLWCD_LWI).

  6. Exhaust line pressures (PDUMP*) and PCAB exhibit occasional narrow (1- to 3-second) spikes.  These spikes were removed from the final data set.

  7. UHSAS data sometimes are noisy and unusable during rapid descents.  Additionally, there are unrealistic gaps in size distributions where the four instrument gain stages overlap.  The total concentration produced by the instrument is believed to be correct.  The concentrations of particles in 0.17 µm and 0.2 µm size ranges is affected by gain stages overlap, which is manifested as a "gap" in the first case and a "hump" in the second, which corresponds to bins 20-22 and 45-50.  Depending on the research needs, users may wish to average across these sections or increase bin sizes to include adjacent bins.

Section II:  Flight-by-Flight Summary

Note:   All times listed below are Coordinated Universal Time (UTC).

RF01 RF02 RF03 RF04 RF05 RF06 RF07 RF08 RF09 RF10 RF11 RF12 RF13 RF14
Last update: Tue Apr 15 22:12:38 GMT 2008