Monin-Obukhov Length and Windspeed Profile Calculator

Introduction : This calculator calculates the Monin-Obukhov length (L), defined as that height at which turbulence is generated more by buoyancy than by wind shear. In the daytime over land, L is typically between 1 to 50 meters. In this calculator, you have three input values:
  1. friction velocity u*, in meters per second (m/s)
  2. the absolute virtual temperature Tv in degrees Kelvin
  3. the kinematic surface heat flux, FHsfc, in units of degrees Kelvin meter per second (K m/s)

In addition, there are two constants in this calculation:

  1. the von Karman constant (k), a unitless constant with a value of 0.4
  2. the gravitational acceleration constant (g), 9.8 m/s2

Mathematical equation for Monin-Obukhov length

This calculator also determines the windspeed profile (M) at a given elevation in the stable surface layer. Inputs for this calculation are:

  1. Aerodynamic roughness length, z0, in meters
  2. Height in the stable surface layer, z, in meters

The algorithm for the windspeed profile (M) is:

Mathematical equation for Monin-Obukhov length

Monin-Obukhov/Windspeed Profile Calculator

NOTE: For your convenience, enter temperatures in degrees Celsius. The calculator will convert them to degrees Kelvin automatically!

Input Values:

Friction velocity (m/s)
Absolute virtual temperature Tv in degrees Celsius
Kinematic surface heat flux, FHsfc
Aerodynamic roughness length, z0, in meters
Height in the stable surface layer, z, in meters

Results:

Monin-Obukhov length (L), in meters
Windspeed profile, in m/s