## Solar Radiation Units and Conversion |
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## 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

## Conversion factors

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

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 |

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 / m^{2}) |
Joule per square centimeter (J / cm^{2}) |
0.36 |

Joule per square centimeter (J / cm^{2}) |
Watt hour per square meter (Wh / m^{2}) |
2.778 |

Joule per square meter (J / m^{2}) |
Watt hour per square meter (Wh / m^{2}) |
0.2778 E-03 |

Langley (Ly) | Wh / m^{2} |
11.6 |

Langley (Ly) | J / m^{2} |
41.84 E+03 |

kLy / year | W / m^{2} |
1.33 |

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 |

**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