THE AMAZON RIVER BREEZE AND THE LOCAL BOUNDARY-LAYER .2. LINEAR-ANALYSIS AND MODELING

Observed boundary-layer circulations close to the confluence of the Ne gro and Solimoes rivers near Manaus in the Brazilian equatorial Amazon forest were presented in Part 1. These are shown through linear analy sis and second-order turbulence modelling to be aspects of a river bre eze superimposed on the basic flow. Linear analysis is presented to es timate the spatial structure and intensity of a breeze induced by a ri ver with width and thermal contrast similar to that observed in the ce ntral Amazon. It is found that observed thermal contrasts are sufficie nt to produce a river breeze that can be perceived more than 20 km inl and daily. A one-dimensional second-order closure model is used to sho w that observed nocturnal low-level wind maxima and diurnal surface wi nd rotation are aspects of a river breeze interacting with the seasona lly-varying mean flow. At night, partial decoupling of the surface fro m the lower atmosphere allows the land breeze to be expressed as a low -level wind maximum. During the day, convective mixing communicates up per level winds to the surface during rapid morning boundary-layer gro wth. Rotation of the surface wind follows as the river breeze circulat ion is then superimposed.