Aerosols - Tiny liquid or solid particles that become suspended in the atmosphere. Some sources for aerosols are volcanoes, wild fires, desert wind storms, and the burning of fossil fuels.

Rayleigh Scattering - Rayleigh scattering is the scientific term that describes the selective scattering of the various wavelengths of visible light that are emitted by the sun. When sunlight passes through air molecules, the shorter wavelengths of blue and violet light are scattered more than the longer wavelengths of red and orange during the day. Because our eyes are more sensitive to blue light, we see the sky as blue during the day. At sunrise and sunset, the longer path light must take through the atmosphere to reach us results in the blue light scattering away before it reaches us. This is why we see the orange and red hues during these times.

isodrosotherm - A line of equal dew point temperature. Isodrosotherms are typically drawn for surface dew points. They can give meteorologists a good read on where surface fronts are located since tightly packed isodrosotherms indicate a dew point gradient.

Tropical Cyclone - It's the generic term for a non-frontal large scale low-pressure system over tropical or sub-tropical waters. These systems have organized convection (i.e. thunderstorm activity) as well as a definite cyclonic surface wind circulation. When the cyclonic winds become sustained at 40 mph they are called tropical storms. They become hurricanes when sustained winds reach 74 mph or greater.

Psychrometer - An instrument used to measure the water vapor content of the air. The first pantented instrument that was coined a "psychrometer" was invented in 1818 by a German inventor named Ernst Ferdinand August.

Derecho - A widespread and usually fast-moving complex of thunderstorms that produce damaging straight-line winds. These systems are long lived, as the swath of wind damage associated with them extends for hundreds of miles. Wind gusts can range from 60 to over 100 mph in a derecho.

GFS (Global Forecast System) - One of the American operational forecast models run at the National Centers for Environmental Prediction. GFS stands for Global Forecast System. The GFS model is run 4 times a day and it covers the entire globe. GFS forecast output can extend up to 384 hours from when it is run.