Measurement of Optical Refraction across the Chesapeake Bay

摘要

Over a thousand measurements of optical refraction across the Chesapeake Bay were made between November 1999 and June 2001. A survey station was placed on the western side of the bay south of Chesapeake Beach MD and used to view lights on Tilghman Island MD on the eastern side at a range of 16.2 km. In addition, the survey station viewed buoys at ranges of 690, 1420, 2050, 2790, 3440, and 4180 m. The heights for the survey station measurements were 2.3, 3.5, 5.4, 12.7, 27.7, and 37 m above the mean water level and the lights were located at 4.7, 9.5, 13.7, 27.0 m above the water level. When weather and work schedules permitted, observations were made twice a day (just after sunrise and at noon). Survey station measurements of the closest buoy are used to estimate the water level. Observations of air-sea temperature differences measured by the mid-bay buoy in the Chesapeake Bay Observing System (CBOS) are compared with the elevation angles. The elevation angles and air-sea temperature differences (ASTD) are analyzed over an annual cycle. The elevation angles and the non-dimensional curvature of the refractive rays are compared with the ASTD.