CALCPI

Calibration of DOE CPI at University of Manchester

1 August 2009 - 31 August 2009

Lead Scientist: Greg McFarquhar

Observatory: AAF (ARM Aerial Facility)

The DOE Cloud Particle Imager (CPI) was used during two recent field campaigns, the Tropical Warm Pool International Cloud Experiment (TWP-ICE) where a comprehensive data set describing tropical cloud systems and their environmental setting and impacts was collected, and the Indirect and Semi-Direct Aerosol Campaign (ISDAC) where a comprehensive set of data describing arctic clouds and the associated aerosol fields was collected. The CPI was included in these campaigns to provide high-resolution ice crystal images and such images have been used in many studies based on the ISDAC and TWP-ICE data sets. Although the CPI was not originally intended to provide size distributions for ISDAC and TWP-ICE, a recent study (Connolly et al. 2007) suggests that the CPI may be able to accurately measure size distributions given sufficiently large averaging times. However, in order to determine size distributions from the CPI, a calibration to determine a scaling factor was performed for each version of the CPI. Thus, the scientific focus of this campaign was to derive a scaling factor for the DOE using the facility at the University of Manchester, and then to apply this scaling factor to the TWP-ICE and ISDAC CPI data so that size distributions could be generated and placed on the DOE archive.