Shallow cumuli are ubiquitous over large areas of the globe, including both the interior of continents and the trade wind
regions over the oceans. Measurements made at the Atmospheric Radiation Measurement (ARM) Climate Research
Facility, located in central North America, provide a unique long-term data set that can be used to investigate the
influence that these clouds have on the shortwave surface energy budget at a continental location. Using data collected
for the summers of 2000 through 2007, inclusive, over 900 hours with fair-weather cumuli were identified using data
from a Total Sky Imager, cloud-radar and lidar. Data from a suite of surface radiometers was used to determine the
shortwave forcing. This analysis estimates the three-dimensional effects of shallow cumuli by examining the occurrences
of both positive and negative shortwave forcing. We show that the average surface shortwave forcing is approximately
-45.5 W m-2. When the data are adjusted to account for periods without shallow clouds, the shortwave forcing over the
entire summer (defined as May through August) are reduced in magnitude, with forcings of -2.1 W m-2.
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