Atmospheric circulation is a very large scale movement of air in which thermal energy is distributed on the surface of the earth. The atmospheric circulation changes from year to year because of several factors. Some of the factors are mid-latitude depression, tropical cells and other random pressure systems.

There are two reasons why tropical weather is different from that at higher latitudes. The sun shines more directly on the tropics than on higher latitudes (at least in the average over a year), which makes the tropics warm (Stevens 2011). And, the vertical direction (up, as one stands on the Earth's surface) is perpendicular to the Earth's axis of rotation at the equator, while the axis of rotation and the vertical are the same at the pole; this causes the Earth's rotation to influence the atmospheric circulation more strongly at high latitudes than low (Sobel 2012). Because of these two factors, clouds and rain storms in the tropics can occur more spontaneously compared to those at higher latitudes, where they are more tightly controlled by larger-scale forces in the atmosphere. Because of these differences, clouds and rain are more difficult to forecast in the tropics than at higher latitudes. On the other hand, temperature is easily forecast in the tropics, because it doesn't change much (Sobel 2012).
When the temperature is high it tends to make the water disappear in the air minus condensing. The rays form the sun shines brighter in the tropics, especially in warmer climaxes which has a large sum of water that evaporate in the air to lap over that makes the humid. (Sobel, 2012). Temperature and pressure both drop quickly with altitude, in the tropics as elsewhere on Earth. If air rises as it can, for example, if it is a little warmer and thus lighter than the air around it will expand and cool, eventually causing some of the water vapor in it to