Validating Diurnal Climatology Logic of the MT‐CLIM Model Across a Climatic Gradient in Oregon: Fid-Bau Portal

Validating Diurnal Climatology Logic of the MT‐CLIM Model Across a Climatic Gradient in Oregon

Glassy, Joseph M. / Running, Steven W.

This study tests diurnal climatology assumptions made in the MT—CLIM model by examining two microclimate variables driven by diurnal atmospheric dynamics: incident solar radiation (in kilojoules per square metre), and humidity, expressed as vapor pressure deficit, VPD (in kilopascals). The relative VPD humidity comparison was used to test our hypothesis that night minimum temperatures can function as a surrogate for dew—point temperatures. VPD was chosen as the humidity measure for these tests since plants are more directly sensitive of this measure than relative humidity. For the observed vs. examined vapor pressure deficit models, we obtained coefficients of determination (R²) ranging from 0.66 to 0.84. Incident solar radiation is calculated in the model using an algorithm that relates diurnal temperature amplitude to atmospheric transmissivity, coupled with a potential radiation model to compute diffuse and direct radiation. Correlations for incident solar radiation models indicate generally good agreement, with coefficients of determination ranging from R² = 0.82 to 0.89. These results suggest that MT—CLIM may be a useful way to provide the climatology that many ecological/hydrological models require, particularly for larger scale spatial modeling applications where precise meteorology may not be as important as a good general characterization of the regional climatology.