Aeronautical Terms beginning with N

Nimbostratus

A principal cloud type, gray colored, often dark, the appearance of which is rendered diffuse by more or less continuously falling rain or snow, which in most cases reaches the ground. It is thick enough throughout to blot out the sun.

Noctilucent clouds

Clouds of unknown composition which occur at great heights, probably around 75 to 90 kilometers. They resemble thin cirrus, but usually with a bluish or silverish color, although sometimes orange to red, standing out against a dark night sky. Rarely observed.

Normal

In meteorology, the value of an element averaged for a given location over a period of years and recognized as a standard.

Numerical forecasting

Forecasting by digital computers solving mathematical equations; used extensively in weather services throughout the world.

Numerical weather prediction

Forecasting by digital computers solving mathematical equations; used extensively in weather services throughout the world.

Normal refraction

Refraction of the radar beam under normal atmospheric conditions; normal radius of curvature of the beam is about 4 times the radius of curvature of the Earth.