# Meteorological Measurements, Units, and Conversions

**Welcome!** This page is useful to meteorologists who need help remembering units, constants, and abbreviations. Scroll down to examine or use the find function within your browser to search within the page.

## Fundamental Units

## Quantity |
## Name of unit |
## Abbreviation |
---|---|---|

Length | meter | m |

Mass | kilogram | kg |

Time | second | s |

Electrical Current | ampere | A |

Temperature | kelvin | K |

## Derived Units

## Quantity |
## Name of unit |
## Symbol |
## SI Units |
---|---|---|---|

Force | newton | N | kg m s^{-2} |

Pressure | pascal | Pa | N m-2 = kg m-1 s-2 |

Energy | joule | J | kg m^{2} s^{-2} |

Power | watt | W | J s^{-1} = kg m^{2} s^{-3} |

Electrical Potential Difference | volt | V | W A^{-1} = kg m^{2} s^{-3} A^{-1} |

Electrical Charge | coulomb | C | A s |

Electrical Resistance | ohm | W | V A^{-1} = kg m^{2} s^{-3} A^{-2} |

Electrical Capacitance | farad | F | A s V^{-1} = kg^{-1} m^{-2} s^{4} A^{2} |

Frequency | hertz | Hz | s^{-1} |

Sound Level | decibel | dB | 10 log (p_{1}/p_{2}) |

Celsius Temperature | degree | °C | K - 273.15 |

Temperature Interval | degree | deg or ° | either K or °C |

## Useful Unit Conversions

## Quantity |
## English |
## SI |
---|---|---|

Velocity | 1 mph; 1 knot | 0.45 m/s; 0.514 m/s |

Temperature | °F | (°F - 32)(5/9) = °C |

Length | 39.4 in | 1 m |

Pressure | 1 psi | 6895 Pa |

Mass | 1 lb | 0.45 kg |

Energy | 1 ft lb | 1.36 J |

Volume | 1 gal | 3.8 x 10^{-3} m^{3} |

## Standard Atmosphere

1 atm | 1013.25 mb; 760 mmHg; 29.921 inHg; 14.7 lb in-2 |

## Other Units

## Quantity |
## Name of unit |
## Symbol |
## Fundamental Units |
---|---|---|---|

Volume | liter | l | 10^{-3} m^{3} |

Pressure | millibar | mbar or mb | 10^{2} Pa |

## Decimal Multiples of Units

## Multiple |
## Prefix |
## Symbol |
---|---|---|

10-1 | deci | d |

10-2 | centi | c |

10-3 | milli | m |

10-6 | micro | m |

10-9 | nano | n |

10-12 | pico | p |

10-15 | femto | f |

10-18 | atto | a |

101 | deca; deka | da |

102 | hecto | h |

103 | kilo | k |

106 | mega | M |

109 | giga | G |

1012 | tera | T |

## Useful Physical Constants

Name of the Constant |
## Abbreviation |
Value and Units |
---|---|---|

Universal Gas Constant | R* | 8.3145 x 10^{3} J K^{-1} mol^{-1} |

Boltzmann's Constant | k | 1.381 x 10^{-23} J K^{-1} molecule^{-1} |

Avogadro's Number | N_{A} |
6.022 x 10^{23} mol^{-1} |

Stefan-Boltzmann Constant | s | 5.6696 x 10^{-8} W m^{-2} K^{-4} |

Planck's Constant | h | 6.6262 x 10^{-34} J s |

Velocity of Light | c | 2.998 x 10^{8} m s^{-1} |

Permittivity of Vacuum | e_{o} |
8.85 x 10^{-12} C^{2} N^{-1} m^{-2} |

Average Radius of the Earth | R_{E} |
6.37 x 10^{6} m |

Mean Gravity at Earth's Surface | g_{o} , g |
9.81 m s^{-2} |

Angular Velocity of Rotation of the Earth | W | 7.292 x 10^{-5} rad s^{-1} |

Average Distance from the Center of the Sun to the Center of the Earth | d , d_{o} |
1.50 x 10^{11} m |

Solar Irradiance on a Perpendicular Plane at the mean Earth-Sun Distance | S_{o} |
1.367 x 10^{3} W m^{-2} |

Average Molecular Weight of Dry Air | M_{d} |
28.97 |

Gas Constant of Dry Air | R_{d} |
287 J K^{-1} kg^{-1} |

Density of Dry Air at 0^{°}C and 1000mb |
r_{d} |
1.275 kg m^{-3} |

Specific Heat of Dry Air at Constant Pressure | c_{pd} |
1004 J K^{-1} kg^{-1} |

Specific Heat of Dry Air at Constant Volume | c_{vd} |
717 J K^{-1} kg^{-1} |

Thermal Conductivity of Dry Air at 0^{°}C |
k | 2.40^{-2} J m^{-1} s^{-1} K^{-1} |

Molecular Weight of Water | M_{w} |
18.016 |

Gas Constant for Water Vapor | R_{v} |
461 J K^{-1} kg^{-1} |

Density of Liquid Water at 0^{°}C |
r _{w} |
1.00 x 10^{3} kg m^{-3} |

Density of Ice at 0^{°} |
r _{i} |
0.917 x 10^{3} kg m^{-3} |

Specific Heat of Water Vapor at Constant Pressure | c_{pv} |
1952 J K^{-1} kg^{-1} |

Specific Heat of Water Vapor at Constant Volume | c_{vv} |
1463 J K^{-1} kg^{-1} |

Specific Heat of Water Vapor at 0^{°}C |
c_{w} |
4218 J K^{-1} kg^{-1} |

Specific Heat of Ice at 0^{°}C |
c_{i} |
2106 J K^{-1} kg^{-1} |

Enthalpy (Latent Heat) of Vaporization of Water at 0^{°}C |
l_{v} |
2.50 x 10^{6} J kg^{-1} |

Enthalpy (Latent Heat) of Vaporization of Water at 100^{°}C |
l_{v} |
2.25 x 10^{6} J kg^{-1} |

Enthalpy (Latent Heat) of Fusion of Water at 0^{°}C |
l_{f} |
3.34 x 10^{5} J kg^{-1} |

Enthalpy (Latent Heat) of Sublimation of Water at 0^{°}C |
l_{s} |
2.83 x 10^{6} J kg^{-1} |

## List of Other Abbreviations

An asterisk (*) denotes other abbreviations. Click on them to see other common abbreviations used.

Abbreviation(s) |
Meaning |
---|---|

a | Radius of the Earth; Acceleration |

b | Buoyancy |

c | Phase Speed of a Wave |

c_{pd} |
Specific Heat of Dry Air at Constant Pressure |

c_{pv} |
Specific Heat of Water Vapor at Constant Pressure |

c_{vd} |
Specific Heat of Dry Air at Constant Volume |

c_{w} |
Specific Heat of Liquid Water |

e | Internal Energy Per Unit Mass or Vapor Pressure |

e_{s} |
Saturation Vapor Pressure |

f | Coriolis Parameter (=2W sinf) |

g | Mangnitude of Gravity; Antenna Gain |

g (*) |
Gravity Vector |

g^{*} |
Effective Gravitational Acceleration |

h | Specific Enthalpy; Effective Pulse Length |

i | Square Root of Negative One |

i (*) |
Unit Vector Along the x-axis |

j (*) |
Unit Vector Along the y-axis |

k (*) |
Unit Vector Along the z-axis |

k | Zonal Wave Number |

l | Mixing Length; Meridional Wave Number |

m | Mass; Vertical Wave Number; Planetary Wave Number |

m_{v} |
Molecular Weight of Water |

n | Distance in Direction Normal to a Parcel Trajectory; Meridional Index for Equatorial Waves; Refractive Index |

n (*) |
Unit Vector Normal to a Surface |

p | Pressure |

p_{o}; p_{s} |
Standard Constant Pressure; Surface Pressure in s Coordinates |

p_{r} |
Received Power |

p_{t} |
Transmitted Power |

q | Specific Humidity; Quasi-geostrophic Potential Vorticity; Water Vapor Mixing Ratio |

q_{s}; w_{s} |
Saturation Mixing Ratio |

r | Radial Distance in Spherical Coordinates; Range to Target |

r (*) |
A Position Vector |

s | Generalized Vertical Coordinates; Distance Along a Parcel Trajectory; Specific Entropy; Dry Static Energy |

t | Time |

t (*) |
Unit Vector Parallel to a Parcel Trajectory |

u_{*} |
Friction Velocity |

u | x-component of Velocity (Eastward); Specific Internal Energy |

v | y-component of Velocity (Northward); Specific Volume (may also be written as a) |

w | z-component of Velocity (Upward) |

w_{*} |
Vertical Motion in Log-Pressure System |

x | Eastward Distance |

y | Northward Distance |

z | Upward Distance (Usually From Surface Of The Earth) |

z_{*} |
Vertical Coordinate in Log-Pressure System |

A | Area |

B | Magnetic Field; Convective Available Potential Energy (CAPE) |

C | Circulation |

C_{d} |
Surface Drag Coefficient |

D_{E} |
Depth of Ekman Layer |

D_{i} |
Drop Diameter |

E | Electric Field; Evaporation Rate |

F | Irradiance |

F (*) |
Friction |

G | Universal Gravitational Constant; Zonal Force |

H | Scale Height; Enthalpy |

J | Heating Rate Per Unit Volume |

K | Total Horizontal Wave Number; Kinetic Energy |

K_{m} |
Eddy Viscosity Coefficient |

L | Radiance; Angular Momentum |

M | Total Mass; Mass in Convergence in Ekman Layer; Absolute Zonal Momentum; Angular Momentum |

M_{v} |
Molecular Weight of Water |

N | Buoyancy Frequency; Number Density; Refractivity |

P | Available Potential Energy; Precipitation Rate; Ertel Potential Vorticity |

Q (*) |
Q Vector |

Q | Heating Rate |

R | Gas Constant for Dry Air; Distance From the Axis of Rotation of the Earth to a Point on the Surface of the Earth; Diabatic Energy Generation Rate |

R_{max} |
Maximum Unambiguous Range |

R (*) |
Vector in the Equatorial Plane Directed from the Axis of Rotation |

R* | Universal Gas Constant |

S | Entropy |

S_{o} |
Solar Irradiance |

S_{p} |
-T ¶ ln T / ¶ p, Stability Parameter in Pressure Coordinates |

T | Absolute Temperature |

U | Horizontal Velocity Scale; Internal Energy |

U (*) |
Three Dimensional Velocity Vector |

V | Speed in Natural Coordinates; Volume |

V_{r} |
Radial Velocity |

V_{max} |
Maximum Unambiguous Velocity |

V (*) |
Horizontal Velocity Vector |

W | Working Rate; Vertical Motion Scale |

X | Zonal Turbulent Drag Force |

Z | Geopotential Height; Radar Reflectivity |

a | Specific Volume (may also be written as v); Albedo |

b | Scattering Coefficient; df/dy, Variation of the Coriolis Parameter with Latitude; Angular Direction of the Wind |

e | Efficiency; Rate of Frictional Dissipation; Thermal Expansion Coefficient of Water; Emissivity; Ratio of Molecular Weights |

g | C_{p}/C_{v}, Ratio of Specific Heats; ¶T/ ¶z, Environmental Lapse Rate |

h | Vertical Component of Absolute Vorticity; Weight Function for Heating Profile |

j | Latitude; Vertical Beam Width |

k | Absorption Coefficient; R/C_{p}, Ratio of Gas Constant to Specific Heat at Constant Pressure; Rayleigh Friction Coefficient |

l | Wavelength; Longitude, Positive Eastward |

m | Dynamic Viscosity |

n | Frequency; Angular Frequency; Kinematic Viscosity |

q | Potential Temperature; Angle; Horizontal Beam Width |

q' | Potential Temperature Deviation (may also be written as Q) |

q_{e} |
Equivalent Potential Temperature |

r | Density |

s | -a ¶q/¶p, Stability Parameter In Isobaric Coordinates; -p/p_{s}, Vertical Coordinate System in s System; Density in Isentropic Coordinates; Standard Deviation; Backscattering Cross-section; Spectrum Width; Surface Tension |

s_{a} |
Absorption Cross-Section |

s_{s} |
Scattering Cross-Section |

t | Optical Depth; Optical Thickness; Optical Path Length; Pulse Duration |

t_{d} |
Diffusive Time Scale |

t_{E} |
Eddy Stress |

t_{o} |
Surface Stress |

w | Vertical Velocity (dp/dt) in Isobaric Coordinates; Angular Frequency |

w (*) |
Vorticity Vector |

y | Horizontal Streamfunction |

z | Vertical Component of Relative Vorticity |

z_{a} |
Vertical Component of Absolute Vorticity |

C | Geopotential Tendency; Meridional Streamfunction |

C_{i} |
Ozone Mixing Ratio |

G | -dT/dz, Lapse Rate of Temperature |

G_{d} |
g/C_{p} Dry Adiabatic Lapse Rate |

G_{s} |
Moist Adiabatic Lapse Rate |

F | Geopotential |

P | Exner Function |

Q | Potential Temperature Deviation (may also be written as q') |

W | Solid Angle; Angular Speed of Rotation of the Earth; Angular Speed of Rotation |

W_{rot} (*) |
Angular Velocity of the Earth |

*This page was created by Chris Ferry and Paul Dornsife.*