Model Name

Technology Approach

Model Type

Welker, et al. (1969)

Gaussian

Model assumes vapour cloud is neutrally buoyant. Release source is subdivided into a number of

Ref: AGA (1973)

point sources.

Drake, et al. (1969)

Gaussian

Model assumes vapour cloud is neutrally buoyant. Release source is converted to a line source

Ref: AGA (1973)

and then a virtual point source.

Germeles-Drake (1973)

Gravity Dispersion followed

Model initially assumes vapour cloud is heavier than air and spreads due to the density differences

Ref: Germeles and Drake (1975)

by Gaussian

between the cloud and the surrounding air. At a selected cloud density or lateral velocity, gravity dispersion is terminated and Gaussian initiated.

SIGMET (SAI) (1975)

Transport

Models cloud dispersion using mass and momentum transport equations. A total of six partial

Ref: Havens (1979)

differential equations must be solved. There are a number of constants that must be selected.

Eidsvik (1979)

Gravity Dispersion followed

Eidsvik is similar to Germeles-Drake but improves the air / cloud transport mixing portion of the

Ref: Eidsvik (1980)

by Gaussian

model during gravity dispersion.

HEGADAS (1980)

Gravity Dispersion

Similar to Eidsvik and Germeles-Drake. Primary difference is that during gravity spread phase,

Ref: Colenbrander (1980)

cloud cross section profile is better modeled.

ZEPHER (1981)

Transport

Same as SIGMET except for mathematical solution procedures.

Ref: Woodward, et al. (1981)

MARIAH (1981)

Transport

Same as SIGMET except for mathematical solution procedures.

Ref: Woodward, et al. (1981)

Safeti (1986)

Combination

A "standard box" model with numerous enhancements to the initial cloud development.

Robinson, et al. (1988)

Transport and Gaussian

Estimates pollutant concentrations downwind from the source, taking into account the

Ref: NOAA (1988)

Dispersion

toxicological and physical characteristics of the spilled material.