Long term measurement of turbulent fluxes at sea

From May through December of 1999, the NOAA Environmental Technology Laboratory deployed a semi-unattended turbulent flux measurement system on board the NOAA Ship Ronald H. Brown. Motion-corrected direct covariance measurements of turbulent fluxes were made continuously over the 7-month expedition, in which the Brown traveled in various regions of the oceans, including the Bay of Bengal, the vicinity of the islands of Nauru and Kwajalein, the Gulf of Alaska, the California coast, and the Equatorial Pacific west of Galapagos. These areas represent widely disparate meteorological regimes, and therefore represent a unique opportunity to test and improve bulk parameterizations which are routinely used in numerical models. For example, wind speeds over the course of the long deployment ranged from 0-18 m/s, air and sea temperatures varied from 4-29 C and 8-32 C, respectively, and humidity ranged from 4-20 g/kg. Additional systems such as a ceilometer, lidar, C-, S-, and Ka-band radars, wind profiler, various radiometers, etc., were deployed during various legs of the excursion, and these remote sensors provide detailed descriptions of the structure of the atmospheric boundary layer. In this paper, we will provide an overview of this large data set and the measurement system, present comparisons of the different regimes in which data were collected, demonstrate the application of the revised Coare 2.6 Bulk Flux Algorithm over all regimes, and describe the future for the deployment of shipboard automated turbulence measurement systems.