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Atmospheric Sciences & Global Change Division
Staff Awards & Honors

August 2012

Charles Long Receives 2012 World Meteorological Organization Väisälä Award for Research on Fractional Cloudiness

Congratulations to Pacific Northwest National Laboratory's Charles Long, together with the esteemed research team, on being winners of the 23rd Professor Dr. Vilho Väisälä Award for an Outstanding Research Paper on Instruments and Methods of Observation: "Optimized fractional cloudiness determination from five ground-based remote sensing techniques" published in the Journal of Geophysical Research. This award consists of a diploma, medal, and honorarium for the team. Long is the only two-time winner of this international research paper award to date.

The team of scientists designed and analyzed an algorithm to provide a continuous and optimized record of the amount of sky covered by clouds, called fractional cloudiness, every 10 minutes for a total of 12 months at the Cabauw Experimental Site for Atmospheric Research in the Netherlands. Assessing five remote sensing instruments, including the Total Sky Imager developed by Long, scientists were able to compare recorded images of the sky every minute. The years' worth of data was then compared against a 30-year climatological record from human observations at two similar sites. The algorithmic analysis was within 99.92 percent accurate based on the other observations.

Assessing the amount of sky covered by clouds is a familiar human pastime. Partly cloudy, overcast, clear sky: these are descriptions captured by the human eye that scientists describe as fractional sky cover. But scientists working to understand the complex warming and cooling effects of direct and reflected sunlight need a more exact approach because measuring cloud fraction is the most basic quantity about clouds needed. Researchers were able to extend the capabilities of individual measurements using this algorithm. Their work was recognized and rewarded with this prestigious award.

Research Team: R Boers, MJ de Haij, WMF Wauben, HK Baltink and LH van Ulft, M Savenije from Royal Netherlands Meteorological Institute, De Bilt, Netherlands; CN Long from Pacific Northwest National Laboratory

Reference: Boers R, MJ de Haij, WMF Wauben, HK Baltink, LH van Ulft, M Savenije, and CN Long. 2010. "Optimized Fractional Cloudiness Determination from Five Ground-based Remote Sensing Techniques." Journal of Geophysical Research 115:D24116. DOI:10.1029/2010JD014661.


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