Interpreting Measurements of Visibility, Relative Humidity, and Solar Irradiance in Coastal Environments for Development of Operational Products

In January 2010, NOAA's Center for Operational Oceanographic Products and Services (CO-OPS) established its first two real-time visibility measurement systems at locations on the western coast of Mobile Bay, AL. These stations employ forward scattering infrared sensors to derive an estimate of Meteorological Optical Range (MOR). Due to significant interest throughout the maritime community, CO-OPS has plans to establish several additional real-time visibility systems at various ports and harbors throughout the United States. Although CO-OPS' primary interest for establishing a network of visibility observatories is enhancing navigational safety, an additional goal will be to identify potential use of in situ surface visibility measurements in meteorological research applications. This includes but is not limited to, the development and validation of operational fog forecasting models.

CO-OPS has previously participated in extensive visibility sensor testing to understand related instrumentation. However, measuring and interpreting visibility conditions along U.S. coasts is a new area for CO-OPS. In order to better understand processes of fog formation in coastal environments and to determine how relative humidity (RH) and solar irradiance measurements can be used to enhance visibility assessments and analysis products, a nine month field experiment was conducted at a United States Army Corp of Engineers (USACE) facility in Chesapeake City, Maryland. A test system consisting of visibility, RH, and solar irradiance sensors was deployed at the USACE facility alongside an existing NOAA water level station where wind speed, direction and air and water temperatures are measured. The purpose of this test is to quantify correlations between visibility, RH, solar irradiance, the impact of wind and air/sea temperature gradients while further developing operational products that are useful to both the mariner and research scientist. Observations from the field experiment will be presented along with preliminary interpretation of results.