Turnipseed NOx profile Data Instructions

Investigator: Andrew Turnipseed, NCAR/ACD
turnip@ucar.edu
Date: 9/20/2012

Filename:  TurnipseedROMBAS_NOx.csv (comma delimited)

Data Interval:  5 min. averages
Initial Start time of file:  July 1, 2011, 0:00:00  (MST)
Missing data = -9999

Columns:
Start_sec:	Beginning of 5 min. period  (seconds since July 1, 2011, 0:00:00 MST)
End_sec: 	End of 5 min. period  (seconds since July 1, 2011, 0:00:00 MST)
Mid_sec:	Midpoint of 5 min. period  (seconds since July 1, 2011, 0:00:00 MST)
Date:		MM/dd/YY, 
Time:		hh:mm:ss, Beginning of 5 min. period (MST)
Day of Year:	decimal day, Beginning of 5 min. period (MST)
NO:		nitric oxide mixing ratio, ppbv
NO2:		nitrogen dioxide mixing ratio, ppbv
NOx:		NO + NO2 mixing ratio, ppbv
z:		Inlet height, m
S flag:		Profiling system = 0,  Separate line = 1.(see explanation below)*

Instrumentation:
NO monitor:  Ecophysics CLD88Y
NO2 Photolysis:  Droplet Technology Blue light converter (modified).
NO2 converson efficiency = 0.42 (measured during exp.)	

Sampling methods: 
Typically, measurements were made from 6 inlets at different heights.
Measurements were made from each inlet for 5 min., cycling through all 6 inlets over a 30 min. period.  These are denoted in the column labeled "z".  
Heights are:  1.5 m, 5.0 m, 8.5 m, 12.0 m, 17.7 m and 25.1 m.
During each 5 min. period the single channel analyzer cycled between measuring NO directly (first 2 minutes),  NO + NO2 (thru the photolysis cell, 2nd 2 minutes) and through a Molybdenum converter (last minute).  

*Due to inadequate cooling - the analyzer periodically shut down during ROMBAS which caused data loss on all instruments connected to the profiling system.  To minimize overall data loss, the NOx instrument was often run separate from the profiling manifold on its own inlet line.  The height for this was separate inlet was at 2.5 m.  The final column (S flag) is given to give a quick indication of when the NOx instrument was running on this separate inlet line.  One consequence of 
this separate inlet was that its proximity to trees/branches resulted in less air flow surrounding this actual intake.  So the NOx concentrations appeared much more variable when sampling from this inlet due to the wind intermittency. 

Calibrations:  The NO instrument was automatically calibrated every 6 hours.  Offsets were measured by diverting the sample flow through a pre-reaction chamber where it reacts with a large excess of ozone.  The instrument was then calibrated via standard addition of a small flow of NO standard (~ 3 sccm, 10 ppmv in Nitrogen, Scott-Marrin) to the main sample flow (~ 3 sLpm).