简短的回答是“水循环”我想。更长的答案是,水可以存在在许多州和地面:至少雪,冰以及液态水和下表面和水蒸气(气)和气溶胶的液体水或冰(云)在大气中。另一方面美元\ mathrm{二氧化碳}$只能存在于一个:天然气。这意味着美元\ mathrm{二氧化碳}$一样混合其他长寿大气的气体组成部分随着时间的推移,这是“很好”。组件的氛围,如美元\ mathrm{二氧化硫}$,不长寿不混得很好,因为他们没有时间。水情况更加复杂,因为有复杂的相变发生在大气中,因为水的分布是非常依赖于地形,特别是它可以移动大距离它从何而来。大气中的水的相变是由温度和压力条件在大气中,从而改变这些条件,和整个系统当然是混乱的。其中一些相变的结果是水离开大气降水。多少水*到*大气取决于表面条件和大气中,也在水* *从表面上看,这是极其不均匀(见上图)。所有这些转换是由来自太阳的能量变化在地球。 So the end result of all that is that - water vapour is not long-lived in the atmosphere as a result of all this, so it doesn't have time to become well-mixed; - water is not evenly-distributed on and below the surface because it's mostly liquid (and because snow & ice is only stable in some parts of the surface); - the behaviour of water entering, moving within, and leaving the atmosphere is extremely complex and chaotic (or 'there is weather'), resulting in large variations over a range of scales in distribution of the various states of water which can live in the atmosphere, and large variations in how much water leaves the atmosphere over various scales.