GENERAL PROPERTIES OF WEATHER & CLIMATE

The differences between weather and climate are substantial. Weather is a series of atmospheric phenomena that take place each day, such as rain, snow, humidity, temperature, etc. Weather is dynamic and changes from one location to the other. On the other hand, climate is the average weather conditions in one location over many years. The climate in the Amazon forest is different from the climate in the tundra. Although weather is dynamic and climate is static, we now know that scientific evidence shows that the climate is changing by human activity in many regions around the world. We call this phenomenon climate change.

Characteristics of Weather

Weather phenomena are basically driven by temperature differences in the atmosphere caused by the uneven heating of the earth’s surface by the sun as the earth rotates around it. Weather phenomena are complex, oscillatory and multi-dimensional. Weather is also chaotic, which means that it has a sensitive dependence on the initial conditions: small changes in one region may translate into large changes somewhere else.

Scientists since the 19th century have attempted to forecast the weather using mathematical equations that represent the bulk of physical interactions that take place in the atmosphere. These equations include the equation of motion, wave equation, condensation equation, and continuity equation, among many others. The combination of these equations can be considered a model of the atmosphere. To make a forecast, the equations in this model must be solved simultaneously and integrated forward in time from a set of initial observations of the atmosphere and the earth’s surface. With the advent of the computer in the 1950’s, it has been possible to solve these equations numerically through a set of approximate differential equations, leading to the field of numerical weather simulation. Also, recent improvements in our ability to observe the earth’s surface, its oceans, and the atmosphere have led to improved starting values for the forecast. It is through the combination of good observations of the current state of the atmosphere, accurate equations of how the atmosphere behaves and high speed computing that the weather and climate are, to varying degrees, predictable.