Effects of rainfall on the seasonal thermocline.

An oceanic planetary boundary layer model is used to determine the effects of fresh water flux on the seasonal pycnocline and mixed layer at Ocean Station "P" ( 50°N, 145°W). First sensitivity of the model was tested by constant forcing with a range of values of precipitation minus evaporation. Then realistic forcing with daily average evaporation, monthly average precipitation values, observed winds and heat fluxes were applied to the model for a simulation of the year 1967. The sensitivity study revealed that precipitation and evaporation have a significant impact on the seasonal evolution of mixed layer depth and temperature, even though the surface heat flux is not changed. The use of realistic forcing indicates the importance of having realistic initial salinity profiles in such models. This is especially true in the autumn and winter seasons when rainfall reduces seasonal mixed layer deepening by as much as 25 meters, representing a 20% change. For the simulation of the year 1967, the model predicted values of salinity very closely follow climatology for the first half of the year. During the late summer and fall, predicted salinity is greater than suggested by the climatology and may be due to unrealistically steady values of precipitation.http://archive.org/details/effectsofrainfal00garzLieutenant J.G., Ecuadorian NavyApproved for public release; distribution is unlimited