From the AMS Glossary of Meteorology:

bright sunshine—Solar radiation intense enough to cast distinct shadows.  See insolation.

insolation—1. (Contracted from incoming solar radiation.) In general, solar radiation received at the earth’s surface.

See terrestrial radiation, direct solar radiation, global radiation, diffuse sky radiation, atmospheric radiation. 2. The amount of direct solar radiation incident upon a unit horizontal surface at a specific level on or above the surface of the earth.  Compare solar constant, total solar irradiance.

solar radiation—The total electromagnetic radiation emitted by the sun.

To a first approximation, the sun radiates as a blackbody at a temperature of about 5700 K; hence, about 99.9% of its energy output falls within the wavelength interval from 0.15 to 4.0 μm, with peak intensity near 0.5 μm. About one-half of the total energy in the solar beam is contained within the visible spectrum from 0.4 to 0.7 μm, and most of the other half lies in the near-infrared, a small additional portion lying in the ultraviolet. See insolation, direct solar radiation, diffuse sky radiation, global radiation, extraterrestrial radiation, solar constant, total solar irradiance.
Fritz, S., 1951: Compendium of Meteorology, 17–19.

We non-scientifically polled our friends on what their favorite weather words were.  Sunshine was in the top three.  Cumulonimbus and thunderstorm were the other two.  Incidentally, you usually can’t have a good thunderstorm without at least a little bit of strong sunshine.

The definition of sunshine is simple enough until you look a little farther into what makes up solar radiation, which is why our weather word is, well, more than one word.  It is more like a drill-down definition, which might get a little too technical for the layman’s needs.  Since the point of this feature is to simplify the term, we won’t go too far into technical details here.  Feel free to use the link above to surf the Glossary for more information.

Sunshine is solar radiation.  Bright sunshine can cast shadows.  Solar radiation is “the total electromagnetic radiation emitted by the sun.”  In other words, it is the full spectrum from the smallest to the longest wavelengths.  Not all of these wavelengths are visible to the human eye, but all of them can affect our world in one way or another.  For example, bright visible sunlight makes us squint, and ultraviolet light can cause skin damage. 

Meteorologists will use the term “insolation” when considering a measure of solar radiation in a specific space.  The idea is useful in the mathematical side of the weather world where equations are used to develop models for forecasting both short- and long-term weather patterns and the effects thereof.

So, the next time you hear someone singing “You Are My Sunshine,” stop and think about how much light they’re referring to and how bright it might be.  I wonder of Johnny Cash was singing to someone whose brightness could cast distinct shadows…

From the AMS Glossary of Meteorology:

cumulonimbus—(Abbreviated Cb.) A principal cloud type (cloud genus), exceptionally dense and vertically developed, occurring either as isolated clouds or as a line or wall of clouds with separated upper portions.

These clouds appear as mountains or huge towers, at least a part of the upper portions of which is usually smooth, fibrous, or striated, and almost flattened as it approaches the tropopause. This part often spreads out in the form of an anvil (incus) or vast plume. Under the base of cumulonimbus, which is often very dark, there frequently exist virga, precipitation (praecipitatio), and low, ragged clouds (pannus), either merged with it or not. Its precipitation is often heavy and always of a showery nature. The usual occurrence of lightning and thunder within or from this cloud leads to its popular appellations: thundercloud, thunderhead (the latter usually refers only to the upper portion of the cloud), and thunderstorm. Cumulonimbus is composed of water droplets and ice crystals, the latter almost entirely in its upper portions. It also contains large water drops, snowflakes, snow pellets, and sometimes hail. The liquid water forms may be notably supercooled. Within a cold air mass in polar regions, the fibrous ice crystal structure may extend virtually throughout the cloud mass. Cumulonimbus always evolves from the further development of cumulus congestus, which, in turn, usually has resulted from the growth of cumulus (Cb cumulogenitus). This complete development may initiate also from stratocumulus castellanus (Cb stratocumulogenitus) or from altocumulus castellanus (Cb altocumulogenitus). In the latter case the cumulonimbus base is particularly high. It may also, but infrequently, develop from a portion of altostratus or nimbostratus (Cb altostratogenitus or Cb nimbostratogenitus). The formative process of cumulonimbus starts as a result of convection from the earth’s surface or instability in the upper air, or both simultaneously. It therefore has a predominant diurnal cycle similar to that of cumulus. Cumulonimbus is rare over the polar regions, and becomes increasingly frequent with decreasing latitude, and is, in fact, an almost regular climax of the diurnal cloud cycle in the humid areas of the tropical regions and in humid and unstable air masses penetrating the temperate latitudes. Because of its great vertical size and of the magnitude and variety of forces that act within and upon it, cumulonimbus is a vertical cloud factory. In addition to the complex of accessory features it may possess, which includes tornadoes (tuba), it may also be responsible for the formation of nearly all of the other cloud genera. Cumulus congestus always preexists, and therefore is often easily confused with, cumulonimbus. A cloud is called cumulus congestus until its upper portion begins to show the diffuseness or fibrous quality indicative of ice crystal predominance. Only cumulonimbus is accompanied by lightning, thunder, or hail; only cumulus congestus can rival the intensity of its shower-type precipitation. See cloud classification, thunderstorm.

Yes, it is a very long definition/description, but this is many a meteorologist’s favorite cloud type.  The basic meteorology-to-English definition is that a cumulonimbus cloud is a thunderstorm cloud.  The cumulonimbus cloud carries with it the amazing power and energy needed to thrust an air particle up from the ground surface through the tropopause (as evidenced by an overshooting top) and to send it back down again to the surface in the form of a 60+ mile per hour straight line wind.  Not to mention that if the cloud is rotating, it could form a tornado.  Plus, there is always the excitement of the lightning and thunder elements of the storm, the possibility of hail, the threat of heavy downpours, and the beautiful color variations it can take on (think green tinted dark blues).  There are so many reasons a weather geek loves a good thunderstorm.

Many people, children and adults alike, fear thunderstorms.  While they should absolutely be respected and watched for signs of danger, and the warnings of danger should be heeded immediately, in most thunderstorms, there is nothing really to fear.  I’ve taught my nephews to throw their hands in the air and scream “whoohoo!” when they hear thunder, to count the seconds between the lightning and the thunder, and to think about the basic process of what makes a storm.  Understanding even the basics can help take away the fear.  In most cases, once the fear is gone, there is nothing left but enjoyment of the rolling thunder and the sound of rain on the roof.

A rotating wall cloud in St. Paul, MN, in the Spring of 2008

Cumulonimbus cloud in St. Paul, MN, on Aug. 8, 2009

Definition from the AMS Glossary of Meteorology:

aerosol—A colloidal system in which the dispersed phase is composed of either solid or liquid particles, and in which the dispersion medium is some gas, usually air.  There is no clear-cut upper limit to the size of particles composing the dispersed phase in an aerosol, but as in all other colloidal systems, it is rather commonly set at 1 μm. Haze, most smokes, and some fogs and clouds may thus be regarded as aerosols. However, it is not good usage to apply the term to ordinary clouds with drops so large as to rule out the usual concept of colloidal stability. It is also poor usage to apply the term to the dispersed particles alone; an aerosol is a system of dispersed phase and dispersing medium taken together.

Often when we hear the term “aerosol” those of us who lived through the 80’s recall Aquanet hairspray and wonder if our usage of it caused the hole in the ozone layer.  All kidding aside, an aerosol is actually a system, not a particle.  This fact may be a surprise to many lay people.  The solid or liquid particles within the gas, which all together make up the system, are usually microscopic, which is why ordinary clouds and fog do not count as aerosols even though, by strict definition, we could use the term for them, too.

The term aerosol is most often associated with air quality issues.

From the AMS Glossary of Meteorology:

atmospheric optics—The study of the optical characteristics of the atmosphere or products of atmospheric processes.

The term is usually confined to visible and near visible radiation. But, unlike meteorological optics, it routinely includes temporal and spatial resolutions beyond those discernible with the naked eye.

In everyday terms, when we discuss optics as related to weather, we are usually talking about rainbows, halos around the sun or moon, sun dogs, mirages (such as water appearing to be on a dry road on a hot day), and sun pillars.  These effects are typically caused by the refraction of visible sunlight through water droplets in the atmosphere.  Because the conditions aren’t right to see them all the time, weather lovers tend to celebrate when we do see them and share when we’re lucky enough to capture them on camera.

Two other most common optical products are sunrises and sunsets, which obviously occur every day and are as unique as snowflakes.

A Sunset in Minnesota

Sunset at Fort Fisher, North Carolina

Sun halo in Raleigh, NC

Please feel free to go to our facebook page and share your favorite photos of meteorological optics!