ENERGY-BALANCE MODEL FOR IMAGERY AND ELECTROMAGNETIC PROPAGATION

The character of temperature and moisture gradients in the atmospheric surface layer is shown to be related to the intensity of visual disto rtions or ''blurring'' of images routinely detected by electo-optical systems and sensors. The authors are able to make quantitative approxi mations of the optical turbulence effect as represented by the refract ive-index structure parameter C(n)2. Through the application of Monin- Obukhov similarity, the magnitudes of potential temperature and specif ic humidity gradients are determined using values of sensible and late nt heat fluxes estimated from a semiempirical radiation and energy bal ance model. The model is constrained to require a minimum number of co nventional meteorological inputs at a specific reference level (i.e., 2 m). These measurements include temperature, pressure, relative humid ity, and wind speed. The model also requires a judgment of soil type a nd moisture (dry, moist, or saturated), cloud characteristics (tenths of cloud cover, opacity, and an estimate of cloud height), day of the year, time of day, and longitude and latitude of the site of interest. Model concepts and equations are presented and several sample results are illustrated. Model estimates of net radiation; sensible, ground, and latent heat fluxes; and C(n)2 are compared with measured values or values derived from measurements.