Eur. Phys. J. Plus (2012) 127: 93
https://doi.org/10.1140/epjp/i2012-12093-y

Regular Article

Ground-truthing a satellite-based night-time cloud identification technique at the Pierre Auger Observatory

¹ Michigan Technological University, Houghton, MI, USA
² Observatorio Pierre Auger, Av. San Martín Norte 304, 5613, Malargüe, Argentina

^* e-mail: jmchirin@mtu.edu

Received: 27 July 2012
Accepted: 27 July 2012
Published online: 28 August 2012

Abstract

Atmospheric conditions are important factors for the cosmic rays detected at the Pierre Auger Observatory. Therefore, we have been accumulating different type of atmospheric data during the last 8 years. This can also be a very interesting source for research for atmospheric scientists. As an illustration of interdisciplinary science, we have used satellite data to identify clouds at night. We developed a method using infrared data from the imager instrument on the GOES-12 satellite. The Pierre Auger Observatory has already installed ground-based instruments, like the Central Laser Facility (CLF), for identifying clouds at night. The Fluorescence Detector (FD) of the Pierre Auger Observatory sees the CLF laser profile and thereby senses the presence of clouds directly above the CLF. For the satellite image pixel encompassing the CLF, we compared cloud identifications with the satellite-based method to those made with the FD observations of CLF laser events. The results of both methods agree. We generate cloud probability maps covering the region of the observatory for all periods of FD operation since 2007. We summarize the cloud cover history of the observatory site as well.