Development of Hourly Meteorological Values From Daily Data and Significance to Hydrological Modeling at H. J. Andrews Experimental Forest

Abstract

Hydrologic modeling depends on having quality meteorological input available at the simulation time step. Often two needs arise: disaggregation from daily to subdaily and extend an available subdaily record. Simple techniques were tested for generating hourly air temperature, precipitation, solar radiation, relative humidity, and wind speed from limited daily data at the H. J. Andrews Experimental Forest, Oregon. Skill of the daily to hourly methods ranged from poor to very good. The best method for each variable had mean error <4% and first-degree efficiency >0.5, with the exception of wind speed, which had a bias problem related to change in measurement height. Significance of the disaggregation assumptions for simulated hydrology was evaluated by driving the Distributed Hydrology Soil Vegetation Model (DHSVM) with alternative meteorological inputs. The largest differences in streamflow simulation efficiency were related to differences in precipitation phase, which followed from the air temperature method used. The largest differences in annual water balance were related to the humidity model used; the common fallback assumption that daily dewpoint temperature equals minimum air temperature led to sharply higher evapotranspiration. Hourly streamflow and annual water balance were less sensitive to the method of distributing precipitation throughout the day and parameterization of solar radiation.