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Cloud Climatology for Land Stations Worldwide, 1971-2009 (NDP-026D)

PDF Original Documentation File (2003) PDF Documentation Update (2012) data Data (NDP-026D)

(Original date of publication, March 2003, as "Cloud Climatology for Land Stations Worldwide, 1971-1996")

Most recent update made August, 2012, extending the climatology through 2009.


C. J. Hahn
Dept. of Atmospheric Sciences,
University of Arizona

S. G. Warren
Dept. of Atmospheric Sciences,
University of Washington

R. Eastman
Dept. of Atmospheric Sciences,
University of Washington




Surface synoptic weather reports for 39 years have been processed to provide a climatology of clouds for each of over 5000 land-based weather stations with long periods of record both day and night. For each station, this digital archive includes: multi-year annual, seasonal and monthly averages for day and night separately; seasonal and monthly averages by year; averages for eight times per day; and analyses of the first harmonic for the annual and diurnal cycles. Averages are given for total cloud cover, clear-sky frequency, and 9 cloud types: 5 in the low level (fog, St, Sc, Cu, Cb), 3 in the middle level (Ns, As, Ac) and one in the high level (all cirriform clouds combined). Cloud amounts and frequencies of occurrence are given for all types. In addition, non-overlapped amounts are given for middle and high cloud types, and average base heights are given for low cloud types. Nighttime averages were obtained by using only those reports that met an "illuminance criterion" (i.e., made under adequate moonlight or twilight), thus making possible the determination of diurnal cycles and nighttime trends for cloud types.

The authors have also produced an online, gridded atlas of the cloud observations contained in NDP-026D. The Online Cloud Atlas containing NDP-026D data is available via the University of Washington.

Also available is NDP-026E, A Gridded Climatology of Clouds over Land (1971-96) and Ocean (1954-97) from Surface Observations Worldwide.

Last updated August, 2012