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.
Revised: February 21, 2011 |
Published: September 30, 2009
Citation
Berg L.K., E.I. Kassianov, C.N. Long, and D. Mills, Jr. 2009.Three-dimensional Effects and Shortwave Cloud Radiative Forcing Associated with Shallow Cumuli Over Central North America. In Remote Sensing of Clouds and the Atmosphere XIV: Proceedings of the SPIE, edited by RH Picard, K Schafer, A Comeron, EI Kassianov and CJ Mertens, 7475, Article No. 747504. Bellingham, Washington:SPIE.PNNL-SA-73335.doi:10.1117/12.832327