you forgot to mention the source
http://study.com/academy/lesson/what...s-effects.html
Atmospheric Pressure
Atmospheric pressure is the force per unit area exerted by the weight of the air. In general it is the pressure differences in space and time that we are interested in. The spatial differences that we measure along the surface of the Earth give useful information about the local wind. The day to day changes at one location tell us what kind of weather to expect. Usually, rising pressure brings fair weather and falling pressure brings poor weather. We show the pressure corrected to sea level. The units of pressure are hectopascals (hPa).
Humidity
Humidity is a measure of the amount of moisture (water vapour) in the air. We are measuring the relative humidity. Relative humidity tells you how water vapour is present as a fraction of the maximum amount of water vapour that could be present in a parcel of air at the current temperature and pressure. If the temperature goes down and the amount of water vapour does not change then the humidity will go up. Relative humidity is expressed in percent (%).
http://www.islandweather.ca/information.php
2. General Circulation
The circulation of the atmosphere is dictated, as a first approximation, by the difference in heating between the tropics and the poles. The difference in surface heating leads differences in pressure above the surface. This in tern leads to air movement from the warmer cell to cooler. The corresponding change in surface pressure resulting from the redistribution of molecules leads to a pressure differential in the opposite direction at the surface. The direct thermal circulation thus created exchanges air between warm and cold regions.
This differential heating leads to the development of a direct thermal circulation known as the Hadley Cell between the tropics and higher latitudes. This circulation cannot extend all the way from the tropics to the poles however as the poleward moving air is turned right (left) in the Northern (Southern) Hemisphere by the Coriolis Force.
http://www.globalchange.umich.edu/gl...ther_patterns/