Indexing solar radiation by clouds for snowmelt modeling

Abstract

Regression equations were developed relating global, direct, and diffuse solar radiation to: (1) potential solar radiation, (2) solar elevation, and (3) the proportion of sky covered by specific cloud genera or by opaque and transparent clouds, on both an hourly and a daily basis. The equations were synthesized from source data collected at two sites in the ponderosa pine forests of Arizona. A subroutine was developed from the derived equations to be used in conjunction with a computer model that simulates snowmelt processes. The subroutine predicts the amount of solar radiation impinging upon a snowpack from cloud cover, when actual measurements are unavailable. Sources of cloud cover information for input to the subroutine are also discussed.