Using CPlot to compare various concentrations measured by different instrumentation for the Saudi Spring09 flight data (as shown in Fig. 1), it was noted that there were similar patterns in spikes from the instrumentation. From this observation, it was concluded that due to the design of the CPC there is a time lag to data collection compared to the other instruments (PCASP and FSSP). Using CPlot to compare the spikes from the CPC, FSSP, and PCASP; the time lag was determined to be on average 4 seconds.

Fig. 1 Time series from the April 2, 2009 flight during aircraft circling flight below cloud base while burning hygroscopic flares. Ambient concentration measurements shown are total CPC (black), total PCASP (red), super-micrometer PCASP (dark red), total CCNC (green), and total FSSP (blue).

To take this time lag into consideration, revisions were made for process_raw in the following:

• create_cpc_header.pro
• cpc.pro
• constants.pro
• N825ST_constants.pro

Fig. 2 Time series from the April 2, 2009 flight including the CPC time lag adjustment. CPC Conc (Black) PCASP Totals(Red)