Surface Energy Fluxes over the Eastern North Pacific Measured during the MAGIC Field Campaign

Description

Surface energy fluxes (shortwave and longwave upwelling and downwelling radiation, surface and latent heat, and precipitation) are key quantities that describe the interactions between the atmosphere and the surface. These fluxes provide the energy and moisture (i.e., the latent heat flux) that drive convection and cloud formation. They contain information on processes that occur affecting atmosphere-surface interactions and are boundary conditions for climate and weather models. The MAGIC field campaign, which occurred between September 2012 and October, 2013, deployed the Second ARM Mobile Facility (AMF2) on the Horizon Spirit as it ran its regular route between Los Angeles and Honolulu. AMF2 contained radars and other instruments to measure properties of clouds and precipitation, instruments to measure aerosol properties, instruments to measure radiation properties, including a Precision Spectral Pyranometer, a Sunshine Pyranometer, a Precision Infrared Radiometer, and a Fast-Rotating Shadowband Radiometer, and instruments to measure meteorological quantities and sea surface temperature. Two technicians accompanied the AMF2, and scientists rode the ship as observers. Radiosondes were routinely launched four times daily, and during one round trip in July, 2013, eight radiosondes were launched each day. In total, more than 550 soundings were made. MAGIC made nearly 20 round trips between Los Angeles and Honolulu (and thus nearly 40 excursions through the stratocumulus-to-cumulus transition) and spent 200 days at sea, collecting an unprecedented data set. During MAGIC, continuous measurements were made of downwelling shortwave and longwave radiation fluxes, and of meteorological and environmental conditions such as wind speed, temperature, relative humidity, and sea surface temperature. Upwelling shortwave and longwave radiation fluxes were calculated based on tabulated values of the sea surface albedo and on the sea surface temperature and emissivity of seawater, respectively. The COARE bulk aerodynamic method was used to calculate fluxes of surface and latent heat. The contribution to energy fluxes from precipitation was also calculated based on measured precipitation, although this quantity was negligible in most instances. These energy fluxes are presented and their temporal variability at a variety of scales is examined.