Monday, 12 January 2009: 1:30 PM
Surface Meteorology and Air-Sea Fluxes under the Stratus Clouds off Northern Chile
Room 128AB (Phoenix Convention Center)
Temporal variability of the surface meteorology and air-sea fluxes of heat, freshwater, and momentum is explored at two sites under the Stratus Clouds off Northern Chile. One site is located 1500 km offshore northern Chile at 20°S, 85°W and has been occupied since October 2000. A second site closer to shore at 20°S, 75°W has been occupied since October 2006. An additional context for these time series is provided by shipboard observations made while transiting the region. This is a region characterized by directionally steady Southeast Trade Winds averaging ~ 6 m s-1, with occasional periods of several days when the wind speed fall and diurnal warming of sea surface temperature is evident. Both sea and air temperature have an annual cycle; mean air temperature is ~ 1°C cooler than the ocean. Incoming shortwave and longwave radiation vary over the year, with some of the annual cycle in shortwave and that in longwave linked to the change in cloud cover. Relative humidity and wind speed do not have well-defined annual cycles. Annual mean net heat flux has been between 20 and 60 W m-2 of heat gain by the ocean over the years, with a well-defined annual cycle peaking at ~150 W m-2 of gain in the southern summer and showing the largest heat loss of ~ -120 W m-2 in the winter. The annual cycle in net heat stems largely from the annual cycle in shortwave radiation.