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# Understanding Scientific Units

 Earth science data parameters have very specific definitions and units. The links below will access some definitions for science parameter units by the topic of interest.
 Temperature | Pressure | Radiation | Aerosols | Air Quality | Clouds | Surface All Unit Definitions | Full Science Glossary | The Metric System

 K kilometer: A metric unit of distance equivalent to 1,000 meters. One kilometer is a little more than one half of a mile.  The Metric System
 L latitude: a measure which identifies the north – south location of a point on the Earth. It is the angle between the line connecting a point on the Earth and the Earth’s center, and the equatorial plane of the Earth. There are three ways to express latitude. You may be most familiar with 0-90 North and 0-90 South. In the computer era this became -90 to +90, where -45 equivalent to 45 South. The third method is less familiar and is called the colatitude. Colatitude is 0 at the north pole, 90 at the equator, and 180 at the south pole. So, 45 South is equivalent to a colatitude of 135.     Related MY NASA DATA Activity:  Latitude and longitude tool.
 L longitude: a measure which identifies the east – west location of a point on the Earth. It is the angular distance along a line of latitude from the Greenwich Meridian – a reference longitude set to be zero degrees. There are three equivalent ways to express longitude, and scientists tend to use them interchangeably. You may be most familiar with longitude as 0-180 East, and 0-180 West. It can also be expressed as 0-360 East, or just 0-360. In that case, 270 East is equivalent to 90 West. The third system arose in the computer era, when carrying both a number (0-180) and a character (East or West) was inconvenient. The new convention of -180 to +180 was then developed. In this case,-90 is equivalent to 90 West.     Related MY NASA DATA Activity:  Latitude and longitude tool.