Weather

Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers to day-to-day temperature and precipitation activity, whereas climate is the term for the statistics of atmospheric conditions over longer periods of time.

Weather is driven by air pressure, temperature and moisture differences between one place and another. These differences can occur due to the sun's angle at any particular spot, which varies by latitude from the tropics. The strong temperature contrast between polar and tropical air gives rise to the jet stream. Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow. Because in most cases the rotational axis of a planet is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. The effect is increased for those moons with enough atmosphere to have observable weather. Over thousands of years, changes in a planet's orbit can affect the amount and distribution of solar energy received by that planet, thus influencing long-term climate and global climate change.

Surface temperature differences in turn cause pressure differences. Higher altitudes are cooler than lower altitudes due to differences in compressional heating. Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location. The system is a chaotic system; so small changes to one part of the system can grow to have large effects on the system as a whole. While many societies have attempted to control the weather, in most cases changes that produced desired results have only occurred post Ascent. Unintentional changes to weather patterns have been observed even in TL D societies.