The spinning of the earth causes day to turn to night, while the rotation of our planet around the sun once a year causes summer to become winter. These two planetary movements combine to influence our daily weather and global climate. They affect wind direction, global temperature patterns, ocean currents and precipitation.
Weather and Climate
The immediate conditions of the atmosphere at a given place and time, including temperature, pressure, humidity, precipitation, cloud cover and wind, are what we call local weather. Climate, on the other hand, is the long-term change of the atmosphere based on observations over a period of several years. The two factors that most strongly affect climate and weather are temperature and precipitation.
Earth's axis is tilted from perpendicular to the plane of the elliptic by 23 degrees, and it rotates on this axis every 24 hours. Since the axis is tilted, different parts of the globe are tipped towards, or away from, the sun at different times of the year. This tilting causes the four seasons, which are at opposite times of the year in the Northern and Southern Hemispheres.
The Earth's seasons aren't as much a product of the planet's distance from the sun as they are of the tilt of the Earth's axis. Summer is warmer than winter because the sun's is closer and its rays shine more directly than during winter; in summer, the days are longer than the nights. During the winter, the sun's rays hit the Earth at a steeper angle, and the days are shorter. The equinoxes are days in which day and night are of equal duration, while the solstices are the days when the sun reaches its farthest northern and southern declinations, creating both the shortest and longest day of the year.
When the Earth rotates on its axis, it prevents air currents from moving in a straight line north and south from the equator. Instead, this rotation deflects winds eastward in both the Northern and Southern Hemispheres. At 30 and at 50 to 60 degrees north/south latitudes, the three main air circulation cells in the atmosphere interface to form the jet streams, which blow from west to east. Also known as the prevailing westerlies, these winds are largely responsible for the weather patterns at these latitudes.
Global air circulation, driven in an east-west pattern by Coriolis forces, transfers warm air from lower latitudes to higher ones and cold air from higher latitudes, creating patterns of lower and higher pressure that create global wind patterns. These global wind and pressure belts are important to Earth's climate, and they influence the local geographical pattern of precipitation and temperature. The winds that produce local weather systems, such as thunderstorms, are the result of local pressure variations and, because they aren't as much affected by Coriolis forces as global winds, they can move in any direction.
- storm image by Boguslaw Florjan from Fotolia.com