GEOG 402

Regional Climates

Macroscale Climates

Mesoscale Climates

Microclimate

Slope – Aspect – Elevation Mountain Influences on Microclimate

•  Elevation –  temperature –  humidity –  cloud cover (radiation) –  fog –  Rainfall

•  Slope and aspect (azimuth) –  radiation balance –  water drainage

Direct beam radiation on a slope

( ) )cos()sin()sin()cos()cos(cos slopesun AAZsZsi −+= Eq. 6.2

I = incident direct beam radiation

S↓= normal incidence radiation

i = incidence angle

s = slope angle

Z = solar zenith angle

Asun = azimuth of the Sun

Aslope = azimuth of the slope

)cos(ZSI ↓= Eq. 6.1

On a horizontal surface:

On a sloping surface:

Direct beam radiation on a slope

Diffuse radiation on a slope

( )2cos1 s

sky+

=ψ

ψsky = fraction of hemisphere composed of sky

ψ terrain = fraction of hemisphere composed of sky

Eq. 6.4

Fraction of sky seen:

Fraction of hemisphere composed of terrain:

skyterrain ψψ −=1

Diffuse radiation on a slope

Diffuse radiation on a slope

Changing solar radiation in Hawaii