MODELING DIURNAL PATTERNS OF AIR-TEMPERATURE, RADIATION WIND-SPEED AND RELATIVE-HUMIDITY BY EQUATIONS FROM DAILY CHARACTERISTICS

Calculated data on diurnal patterns from daily averages can be useful as inputs for models simulating plant processes such as photosynthesis and transpiration. A method was developed for the calculation of diur nal patterns of air temperature, wind speed, global radiation and rela tive humidity from available daily data. Calculated data were validate d with measured data collected in Israel, California and The Netherlan ds. A simple sine-exponential method for describing diurnal air temper ature was not sufficient in most cases, and the addition of parameters which specified the time lag of maximum temperature and the effect of buoyancy improved the data accuracy. Diurnal course of wind speed cou ld be described using two sine curves scaled by the measured daily tot al wind run. Time base of each of the sine curves and the minimum wind speed had to be defined for each location. An accurate description of the diurnal global radiation was obtained, based on the measured dail y total global radiation, and the calculated sine of the solar elevati on corrected for atmospheric transmissivity. Relative humidity was cal culated from the dew point temperature computed as the minimum value o f a characteristic seasonal value or the actual air temperature. When the site-specific parameters were known or correctly estimated these m ethods gave good estimations of the diurnal weather patterns. Copyrigh t (C) 1996 Elsevier Science Ltd