柱密度在天文学是中指单位面积为底面的整个柱状区域中物质的数量：

而在大气科学中通常指的是物质的质量：

The area density (also known as areal density, surface density, or superficial density) of a two-dimensional object is calculated as the mass per unit area. The SI derived unit is: kilogram per square metre (kg·m).