次表层的 meaning in Chinese

subsurface

For a time , surface and subsurface current are in opposite directions ; flow is seaward at the surface and landward near the bottom
在一个时期，表层和次表层的水流方向相反；表层水流向外海方向流动，靠近底层的水流则向陆地方向流动。
For a time , surface and subsurface currents are in opposite directions ; flow is seaward at the surface and landward nearthe bottom
译为:有一个时期,表层和次表层的水流方向相反,表层水流向外海方向流动,靠近底层的水流则向陆地方向流动。