# 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

### Abbreviation

Length meter m
Mass kilogram kg
Time second s
Electrical Current ampere A
Temperature kelvin K

## Derived Units

### SI Units

Force newton N kg m s-2
Pressure pascal Pa N m-2 = kg m-1 s-2
Energy joule J kg m2 s-2
Power watt W J s-1 = kg m2 s-3
Electrical Potential Difference volt V W A-1 = kg m2 s-3 A-1
Electrical Charge coulomb C A s
Electrical Resistance ohm W V A-1 = kg m2 s-3 A-2
Electrical Capacitance farad F A s V-1 = kg-1 m-2 s4 A2
Frequency hertz Hz s-1
Sound Level decibel dB 10 log (p1/p2)
Celsius Temperature degree °C K - 273.15
Temperature Interval degree deg or ° either K or °C

## Useful Unit Conversions

### 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 m3

## Standard Atmosphere

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

## Other Units

### Fundamental Units

Volume liter l 10-3 m3
Pressure millibar mbar or mb 102 Pa

## Decimal Multiples of Units

### 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 103 J K-1 mol-1
Boltzmann's Constant k 1.381 x 10-23 J K-1 molecule-1
Avogadro's Number NA 6.022 x 1023 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 108 m s-1
Permittivity of Vacuum eo 8.85 x 10-12 C2 N-1 m-2
Average Radius of the Earth RE 6.37 x 106 m
Mean Gravity at Earth's Surface go , 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 , do 1.50 x 1011 m
Solar Irradiance on a Perpendicular Plane at the mean Earth-Sun Distance So 1.367 x 103 W m-2
Average Molecular Weight of Dry Air Md 28.97
Gas Constant of Dry Air Rd 287 J K-1 kg-1
Density of Dry Air at 0°C and 1000mb rd 1.275 kg m-3
Specific Heat of Dry Air at Constant Pressure cpd 1004 J K-1 kg-1
Specific Heat of Dry Air at Constant Volume cvd 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 Mw 18.016
Gas Constant for Water Vapor Rv 461 J K-1 kg-1
Density of Liquid Water at 0°C r w 1.00 x 103 kg m-3
Density of Ice at 0° r i 0.917 x 103 kg m-3
Specific Heat of Water Vapor at Constant Pressure cpv 1952 J K-1 kg-1
Specific Heat of Water Vapor at Constant Volume cvv 1463 J K-1 kg-1
Specific Heat of Water Vapor at 0°C cw 4218 J K-1 kg-1
Specific Heat of Ice at 0°C ci 2106 J K-1 kg-1
Enthalpy (Latent Heat) of Vaporization of Water at 0°C lv 2.50 x 106 J kg-1
Enthalpy (Latent Heat) of Vaporization of Water at 100°C lv 2.25 x 106 J kg-1
Enthalpy (Latent Heat) of Fusion of Water at 0°C lf 3.34 x 105 J kg-1
Enthalpy (Latent Heat) of Sublimation of Water at 0°C ls 2.83 x 106 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
cpd Specific Heat of Dry Air at Constant Pressure
cpv Specific Heat of Water Vapor at Constant Pressure
cvd Specific Heat of Dry Air at Constant Volume
cw Specific Heat of Liquid Water
e Internal Energy Per Unit Mass or Vapor Pressure
es 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
mv 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
po; ps Standard Constant Pressure; Surface Pressure in s Coordinates
pt Transmitted Power
q Specific Humidity; Quasi-geostrophic Potential Vorticity; Water Vapor Mixing Ratio
qs; ws 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
Cd Surface Drag Coefficient
DE Depth of Ekman Layer
Di Drop Diameter
E Electric Field; Evaporation Rate
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
Km Eddy Viscosity Coefficient
L Radiance; Angular Momentum
M Total Mass; Mass in Convergence in Ekman Layer; Absolute Zonal Momentum; Angular Momentum
Mv 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
Rmax Maximum Unambiguous Range
R (*) Vector in the Equatorial Plane Directed from the Axis of Rotation
R* Universal Gas Constant
S Entropy
Sp -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
Vmax 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 Cp/Cv, 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/Cp, 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)
qe Equivalent Potential Temperature
r Density
s -a ¶q/¶p, Stability Parameter In Isobaric Coordinates; -p/ps, Vertical Coordinate System in s System; Density in Isentropic Coordinates; Standard Deviation; Backscattering Cross-section; Spectrum Width; Surface Tension
sa Absorption Cross-Section
ss Scattering Cross-Section
t Optical Depth; Optical Thickness; Optical Path Length; Pulse Duration
td Diffusive Time Scale
tE Eddy Stress
to Surface Stress
w Vertical Velocity (dp/dt) in Isobaric Coordinates; Angular Frequency
w (*) Vorticity Vector
y Horizontal Streamfunction
z Vertical Component of Relative Vorticity
za Vertical Component of Absolute Vorticity
C Geopotential Tendency; Meridional Streamfunction
Ci Ozone Mixing Ratio
G -dT/dz, Lapse Rate of Temperature
Gd g/Cp Dry Adiabatic Lapse Rate
Gs 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
Wrot (*) Angular Velocity of the Earth

This page was created by Chris Ferry and Paul Dornsife.