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Solar Radiation Units and Conversion

A problem of units ?
of terminology ?
Consult the Education service.

International system of units

The International System of Units, abbreviated SI (from the French Système International), is the internationally-agreed system of measurement.

Angles: Plane angles are expressed in radian (rad), or degrees, or sexagesimal degrees (degrees, minutes, seconds). Convert from one unit to another
Energy: Energy, work, quantity of heat are expressed in Joule (J). It can be expressed by unit of surface: J/m2, J/cm2. Irradiation is the energy received per area. Other units are Wh (Watt hour), calorie, therm, Langley. Convert from unit to another
Power: Power, radiant flux are expressed in Watt (W). Irradiance is defined as a power received per area; it is expressed in W m-2 (watt per square meter). Convert from unit to another
Pressure :Pressure is expressed in Pascal (Pa). In meteorology, the unit hPa (hecto-Pascal) is commonly used; it is 100 times a Pascal. It replaces the millibar unit and they are equivalent. Another unit is the "atmosphere". Convert from unit to another

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Conversion factors

The following tables give conversion factors to convert units into others. See an example

Angles

To convert from Into Multiply by
degrees (°) radians (rad) 1.745329 E-02
radians (rad) degrees (°) 57.29578
minutes (’) degrees (°) 0.0167
seconds (") degrees (°) 1.6667 E-04
degrees, minutes, seconds degrees with decimals degrees + minutes/60 + seconds/3600

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Energy / Power

To convert from Into Multiply by
calorie (cal) Joule (J) 4.1868
Watt second (W s) Joule (J) 1
Watt hour (Wh) Joule (J) 3.6 E+03
Joule (J) calorie (cal) 0.2388
Joule (J) Watt hour (Wh) 0.2778 E-03
therm (Europe) Joule (J) 1.05506 E+08
Watt hour per square meter (Wh / m2) Joule per square centimeter (J / cm2) 0.36
Joule per square centimeter (J / cm2) Watt hour per square meter (Wh / m2) 2.778
Joule per square meter (J / m2) Watt hour per square meter (Wh / m2) 0.2778 E-03
Langley (Ly) Wh / m2 11.6
Langley (Ly) J / m2 41.84 E+03
kLy / year W / m2 1.33

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Pressure

To convert from Into Multiply by
atmosphere standard (atm) Pascal (Pa) 1.01325 E+05
atmosphere standard (atm) hecto-Pascal (hPa) 1.01325 E+03
Pascal (Pa) atmosphere standard 0.98692 E-05

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How to Use the Conversion Factors: Each entry of the above tables is to be interpreted as follows.

To convert from Into Multiply by
Watt hour (Wh) Joule (J) 3.6 E+03

means 1 Wh = 3600 J. Thus to express, for example, the energy E = 6.5 Wh in J, write
E = 6.5 Wh x 3600 J/(Wh) = 23400 J = 23.4 kJ

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