The planetary-boundary-layer (PBL) flow and above is investigated for the central north coast of Brazil, an equatorial region spanning from 8° to 2°S. The daily PBL flow is controlled by vertical entrainment of horizontal momentum from a southerly large-scale flow associated with the Hadley cell, and by a mesoscale pressure gradient force (PGF) created by the differential heating between land and ocean. Near the coast, the flow is from the north-east quadrant comprising a small rotation, probably caused by a weak mesoscale PGF and a weak Coriolis force. Inland it is north-easterly in the morning, but deep mixing during the afternoon brings down momentum from above causing it to become south-easterly. The mesoscale PGF executes a daily 360° rotation at most of the stations. In the afternoon it points to land due to continuous heating of the land, and a sea breeze develops in the presence of the background flow. Once convection dies out, the transfer of horizontal momentum is reduced, and the marine-air layer can flow faster into the continent as a nocturnal jet. As the stable boundary layer grows thicker, this flow tends to be eliminated at the surface. By morning, the mesoscale PGF points north, forcing the inland flow to become south-easterly, while on the coast flow becomes almost easterly. This scenario repeats during dry and wet seasons and can be understood as a consequence of the south–north propagation of an atmospheric circulation resembling a helix with its rotation axis oriented parallel to the shoreline.

研究了巴西中部北海岸（赤道区域范围为8°至2°S）的行星边界层（PBL）及其以上的流动。每天的PBL流量是由与Hadley细胞相关的南风大尺度流的水平动量的垂直夹带以及陆地和海洋之间的差热产生的中尺度压力梯度力（PGF）来控制的。在海岸附近，流量来自东北象限，包括一个小的旋转，这可能是由中等尺度的PGF弱和科里奥利力弱引起的。内陆地区早上是东北偏北，但下午的强烈混合会使动量从上而下，从而变成东南偏东。中尺度PGF在大多数站都每天执行360°旋转。下午，由于土地不断加热，它指向土地，在背景气流的作用下，海风逐渐形成。一旦对流消逝，水平动量的传递就减少了，海洋空气层可以作为夜间喷气机更快地流入非洲大陆。随着稳定边界层变得越来越厚，这种流动趋于在表面被消除。到了早晨，中尺度的PGF指向北，迫使内陆流向东南方向移动，而在沿海，流向近东方向移动。这种情况在干旱和潮湿季节会重复出现，可以理解为大气循环向南向北传播的结果，类似于螺旋形，其旋转轴平行于海岸线。海洋空气层可以通过夜间喷气机更快地流入非洲大陆。随着稳定边界层变得越来越厚，这种流动趋于在表面被消除。到了早晨，中尺度的PGF指向北，迫使内陆流向东南方向移动，而在沿海，流向近东方向移动。这种情况在干燥和潮湿的季节重复出现，可以理解为大气循环向南向北传播的结果，类似于螺旋，其旋转轴平行于海岸线。海洋空气层可以通过夜间喷气机更快地流入非洲大陆。随着稳定边界层变得越来越厚，这种流动趋于在表面被消除。到了早晨，中尺度的PGF指向北，迫使内陆流向东南方向移动，而在沿海，流向近东方向移动。这种情况在干燥和潮湿的季节重复出现，可以理解为大气循环向南向北传播的结果，类似于螺旋，其旋转轴平行于海岸线。