Abstract
One of the key measurements from the Clouds and the Earth’s Radiant
Energy System (CERES) satellite is Earth emitted or longwave (LW)
radiation. The CERES Ocean Validation Experiment (COVE), located at
Chesapeake Light Station, approximately 25 kilometers east of Virginia
Beach, Virginia (coordinates: 36.90N, 75.71W) had provided surface
validation for the CERES satellite measurements for many years.
Upwelling LW radiation was one of the measurements made at COVE but was
complicated due to the Light Station tower being in the upwelling LW
instruments field of view. According to our estimates, the Light Station
tower alters 15% of the upwelling LW radiation. An unwanted consequence
of the tower being in the field of view was the tower radiating effect,
particularly noticeable on clear, sunny days. During these days, the
tower would radiate extra heat energy by as much as 3% (15 W/m^2)
that was measured by the upwelling LW instrument. COVE follows the
Baseline Surface Radiation Network requirements and their target
uncertainty is 2%. To resolve this issue, we obtain a different
upwelling longwave value using data from an infrared radiation
thermometer (IRT) and a pyrgeometer that retrieves sea surface
temperature (SST) and downwelling longwave respectively. Using an IRT
allows conversion from SST to a water emission value and the pyrgeometer
provides the reflected flux of the downward longwave radiation. By
determining the extent of the undesirable obstruction in the field of
view of the upwelling longwave instrument and determining its emissivity
could allow others with similar issues to obtain the proper values of
upwelling longwave measurements.