将“upper layer"翻译成中文

At the upper layers, these studies are required to characterize the baseline environmental conditions.

在海洋上层也需要进行这些研究,以便确定基线环境状况的特征。

The upper layer of the permafrost is estimated to contain more organic carbon than is currently contained in the atmosphere

估计永久冻结带上层部分含有比目前大气中更多的有机碳。