Probability Distribution Function of the Upper Equatorial Pacific Current Speeds

[1] The probability distribution function (PDF) of the upper (0–50 m) tropical Pacific current speeds (w), constructed from hourly ADCP data (1990–2007) at six stations for the Tropical Atmosphere Ocean project, satisfies the twoparameter Weibull distribution reasonably well with different characteristics between El Nino and La Nina events: In the western Pacific, the PDF of w has a larger peakedness during the La Nina events than during the El Nino events; and vice versa in the eastern Pacific. However, the PDF of w for the lower layer (100–200 m) does not fit theWeibull distribution so well as the upper layer. This is due to the different stochastic differential equations between upper and lower layers in the tropical Pacific. For the upper layer, the stochastic differential equations, established on the base of the Ekman dynamics, have analytical solution, i.e., the Rayleigh distribution (simplest form of the Weibull distribution), for constant eddy viscosity K. Knowledge on PDF ofw during the El Nino and LaNina events will improve the ensemble horizontal flux calculation, which contributes to the climate studies. Citation: Chu, P. C. (2008), Probability distribution function of the upper equatorial Pacific current speeds, Geophys. Res. Lett., 35, L12606, doi:10.1029/2008GL033669.