Fog is a visible aerosol consisting of tiny water droplets or ice crystals suspended in the air at or near the Earth’s surface. Fog can be considered a type of low-lying cloud usually resembling stratus, and is heavily influenced by nearby bodies of water, topography, and wind conditions
Drizzle
Drizzle is a light liquid precipitation consisting of liquid water drops smaller than those of rain – generally smaller than 0.5 mm (0.02 in) in diameter.^[1] Drizzle is normally produced by low stratiform clouds and stratocumulus clouds. Precipitation rates from drizzle are on the order of a millimetre (0.04 in) per day or less at the ground. Owing to the small size of drizzle drops, under many circumstances drizzle largely evaporates before reaching the surface and so may be undetected by observers on the ground.

MIST
Cloud cover is often referred to as “mist” when encountered on surfaces of mountains, whereas moisture suspended above a body of water, cleared or marsh area is usually called “fog”. One main difference between mist and fog is visibility.^[1] The phenomenon is called fog if the visibility is 1 km (1,100 yd) or less. In the United Kingdom, the definition of fog is visibility less than 100 m (330 ft) on the surface for driving purposes, UK Highway Code rule 226,^[2] while for pilots the distance is 1 km at cruising height. Otherwise, it is known as mist.

The solar irradiance is the output of light energy from the entire disk of the Sun, measured at the Earth. It is looking at the Sun as we would a star rather than as a image.

The solar spectral irradiance is a measure of the brightness of the entire Sun at a wavelength of light. Important spectral irradiance variations are seen in many wavelengths, from the visible and IR, through the UV, to EUV and X-ray. As we look at the solar irradiance we should remember that space weather is related to ionization, while climate is related to absorption of heat.

Measuring the spectral irradiance is important because different wavelengths (or colors) of sunlight are absorbed in different parts of our atmosphere. We feel warm because of the visible and infrared radiation that reaches the surface. Ultraviolet light creates the ozone layer and is then absorbed by that ozone. Higher still ultraviolet light creates the thermosphere, which is ionized by light at the short wavelengths of the extreme ultraviolet (EUV). Because radio communications are affected by the created ions, changes in the solar EUV output are a primary Space Weather concern.

Energy from other sources also enters our atmosphere. A table of some of them is shown below. Note that the energy input from Joule heating, a coupling of the ionosphere to the magnetosphere, can be about the same as from solar EUV!

ab Content

Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions, both in the atmosphere or with one on the ground, temporarily neutralize themselves, causing the instantaneous release of an average of one gigajoule of energy.^[1][2][3] This discharge may produce a wide range of electromagnetic radiation, from heat created by the rapid movement of electrons, to brilliant flashes of visible light in the form of black-body radiation. Lightning causes thunder, a sound from the shock wave which develops as gases in the vicinity of the discharge experience a sudden increase in pressure. Lightning occurs commonly during thunderstorms as well as other types of energetic weather systems, but volcanic lightning can also occur during volcanic eruptions.

The three main kinds of lightning are distinguished by where they occur: either inside a single thundercloud, between two different clouds, or between a cloud and the ground. Many other observational variants are recognized, including “heat lightning”, which can be seen from a great distance but not heard; dry lightning, which can cause forest fires; and ball lightning, which is rarely observed scientifically.

Humans have deified lightning for millennia. Idiomatic expressions derived from lightning, such as the English expression “bolt from the blue”, are common across languages. At all times people have been fascinated by the sight and difference of lightning. The fear of lightning is called astraphobia.

In meteorology, precipitation  is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds.^[2] The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor (reaching 100% relative humidity), so that the water condenses and “precipitates” or falls. Thus, fog and mist are not precipitation but colloids, because the water vapor does not condense sufficiently to precipitate. Two processes, possibly acting together, can lead to air becoming saturated: cooling the air or adding water vapor to the air. Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called showers.^[3]

Moisture that is lifted or otherwise forced to rise over a layer of sub-freezing air at the surface may be condensed into clouds and rain. This process is typically active when freezing rain occurs. A stationary front is often present near the area of freezing rain and serves as the focus for forcing and rising air. Provided there is necessary and sufficient atmospheric moisture content, the moisture within the rising air will condense into clouds, namely nimbostratus and cumulonimbus if significant precipitation is involved. Eventually, the cloud droplets will grow large enough to form raindrops and descend toward the Earth where they will freeze on contact with exposed objects. Where relatively warm water bodies are present, for example due to water evaporation from lakes, lake-effect snowfall becomes a concern downwind of the warm lakes within the cold cyclonic flow around the backside of extratropical cyclones. Lake-effect snowfall can be locally heavy. Thundersnow is possible within a cyclone’s comma head and within lake effect precipitation bands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation. On the leeward side of mountains, desert climates can exist due to the dry air caused by compressional heating. Most precipitation occurs within the tropics^[4] and is caused by convection. The movement of the monsoon trough, or intertropical convergence zone, brings rainy seasons to savannah regions.

Rain is liquid water in the form of droplets that have condensed from atmospheric water vapor and then become heavy enough to fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides suitable conditions for many types of ecosystems, as well as water for hydroelectric power plants and crop irrigation.

Temperature  is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy, present in all matter, which is the source of the occurrence of heat, a flow of energy, when a body is in contact with another that is colder or hotter.

Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have used various reference points and thermometric substances for definition. The most common scales are the Celsius scale (formerly called centigrade, denoted as °C), the Fahrenheit scale (denoted as °F), and the Kelvin scale (denoted as K), the last of which is predominantly used for scientific purposes by conventions of the International System of Units (SI).

The lowest theoretical temperature is absolute zero, at which no more thermal energy can be extracted from a body. Experimentally, it can only be approached very closely (100 pK), but not reached, which is recognized in the third law of thermodynamics.

Wind is the natural movement of air or other gases relative to a planet’s surface. Wind occurs on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hours, to global winds resulting from the difference in absorption of solar energy between the climate zones on Earth. The two main causes of large-scale atmospheric circulation are the differential heating between the equator and the poles, and the rotation of the planet (Coriolis effect). Within the tropics and subtropics, thermal low circulations over terrain and high plateaus can drive monsoon circulations. In coastal areas the sea breeze/land breeze cycle can define local winds; in areas that have variable terrain, mountain and valley breezes can prevail.

A measurement of how much wind has passed a given point in a period of time. A wind blowing at three miles per hour for an entire hour would give a wind run of three miles.

Cumulus calculates wind run by noting the average wind speed every minute (assuming the software remains running). Wind run is calculated by adding in a minute’s worth of ‘distance’ corresponding to that speed. So the wind run for a particular period is effectively an indication of the average wind speed over that period. There are 1,440 minutes in a day. A wind speed measured in distance units divided by minutes, would give a wind run numerically equal to the speed each minute. A wind speed measured in distance units divided by hours, would give a wind run numerically equal to the speed when calculated for a period of an hour.

A wind run of 240 miles over the course of a day, for example, means that the average (of typically 1,440 measurements of) wind speed over the 24 hour day was 10 mph. Cumulus stores the wind run for each day in dayfile.txt.