The map here shows the average amount of water vapor in a column of atmosphere during one month in 2015,
Based on the data in the map, where is most of Earth's water vapor?

1. aspect is nothing really because the answer is right in front of your face

Gravitational force i believe

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.