Evaporation Duct Height Measurements in the Mid-Atlantic

• Main Authors: Fairall,C W, Davidson,K L, Schacher,G E, Houlihan,T M
• Other Authors: NAVAL OCEANOGRAPHIC OFFICE NSTL STATION MS
• Format: Text
• Language: English
• Published: 1978
• Subjects: Meteorology; Radiofrequency Wave Propagation; *DUCTS; MEASUREMENT; ATMOSPHERIC TEMPERATURE; BOUNDARY LAYER; TURBULENCE; VARIATIONS; MEASURING INSTRUMENTS; WIND VELOCITY; EVAPORATION; PACIFIC OCEAN; SURFACE TEMPERATURE; RADIO TRANSMISSION; NORTH ATLANTIC OCEAN; HEIGHT; HUMIDITY; RESEARCH SHIPS; Evaporation ducts; Fluctuation; Kane; Pacific; North Atlantic
• Online Access: http://www.dtic.mil/docs/citations/ADA091851; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA091851

Atmospheric boundary layer measurements were made in the Mid-Atlantic aboard USNS KANE during February and March 1978. The results were analyzed to obtain Monin-Obukhov similarity parameters and EM wave train propagation characteristics within the evaporation ducts that overlay the sea surface. Evaporation duct heights (Z*) varied between 2 and 25 meters during the cruise; the mean Z* value was 15 meters. In one instance, Z* changed from 3 meters to 20 meters in about 4 hours following a frontal passage. A comparison of the results obtained using a simplified 'bulk method' with those yielded by the established (but technically taxing) 'profile method' did not convincingly establish that the bulk method could consistently predict accurate values of Z*. Two factors predominate in controlling the duct height Z*: they are relative humidity and the air-sea temperature difference. Barring the development of radical new measurement techniques, the results of this work indicate that a program for routinely measuring Z* is most likely to be obstructed by shortfalls in the quality of air-sea temperature difference data. (Author)