Climate determinants

Over historic time spans there are a number of static variables that determine climate, including: latitude, altitude, proportion of land to water,and proximity to oceans and mountains. Other climate determinants are more dynamic: The thermohaline circulation of the ocean distributes heat energy between the equatorial and polar regions; other ocean currents do the same between land and water on a more regional scale.

Degree of vegetation coverage affects solar heat absorption, water retention, and rainfall on a regional level. Alteration in the quantity of atmospheric greenhouse gases determines the amount of solar energy retained by the planet, leading to global warming or global cooling. The variables which determine climate are numerous and the interactions complex, but there is general agreement that the broad outlines are understood, at least in so far as the determinants of historical climate change are concerned.

Hail formation

Hail forms on condensation nuclei such as dust, bugs, or ice crystals, when super cooled water freezes on make contact with. In clouds contains large numbers of super cooled water droplets, these ice nuclei grow quickly at the expense of the liquid droplets because the saturation vapor pressure over ice is slightly less than the saturation vapor pressure over water. If the hail stones grow large enough, latent heat released by further freezing may melt the external shell of the hail stone. The development that follows, usually called wet growth, is more efficient because the liquid outer shell allows the stone to accrete other smaller hail stones in addition to super cooled droplets.

Once a hailstone become too heavy to be supported by the storm's updraft it falls out of the cloud. The reason rain can't fall, is typically because of the tough winds inside a thunderstorm cloud. These winds hold the rain and freeze it. As the process repeats, the hail grows gradually larger. When a hail stone is cut in half, a series of concentric rings, like that of an onion, are revealed. From these rings we can determine the total number of times the hail stone had traveled to the top of the storm before falling to the ground.

Climate versus weather

In the most succinct words, weather is the combination of events in the atmosphere and climate is the overall accumulated weather in a certain location.The exact boundaries of what is climate and what is weather are not well defined and depend on the application. For example, in some senses an individual El Niño event could be considered climate; in others, as weather.

When the original conception of climate as a long-term average came to be considered, perhaps towards the end of the 19th century, the idea of climate change was not current, and a 30 year average seemed reasonable.Given the current availability of data on long-term trends in the temperature record, it is harder to give a definition of climate to suit all purposes: over a 30 year period, averages may shift; over a shorter period, the statistics are less stable.