P45     Evaluation of a hierarchy of urban canopy parameterizations in the WRF model during the passage of a cold front in Houston.

Hendricks, Eric A., Jason C. Knievel, and Yi Wang, National Center for Atmospheric Research

A hierarchy of four different urban canopy models (UCMs) of increasing fidelity are evaluated in the Weather Research and Forecasting (WRF) model during a strong cold frontal passage in Houston, Texas, from January 21-24, 2017. The UCMs are: (i) simple bulk formulae, (ii) one-layer UCM, (iii) multiple layer building effects parameterization (BEP) that includes the three-dimensional effects of buildings, and (iv) multiple layer BEP combined with a building energy model (BEM) that includes the heat generated from the interior of buildings. The BEP and BEM models are newly added to the Yonsei University (YSU) planetary boundary layer (PBL) parameterization for this study. The WRF simulations are evaluated against near-surface air monitoring stations in the city of Houston from the Texas Commission on Environmental Quality (TCEQ). For the evaluation of the 10-m wind speed, the BEP and BEP-BEM simulations had the smallest mean biases, smallest root-mean-squared errors, and largest hit rates. These simulations most accurately simulated the urban region wind speed reductions, consistent with the observations, while the bulk and one-layer UCM simulations had wind speeds that were too high. The multi-layer UCMs also better reproduced the wind direction variability at the TCEQ monitors during light and variable inflow conditions. For the 2-m temperature, the bulk scheme performed the best overall while the one-layer and multi-layer UCMs had temperatures that were too cool during the nighttime and early morning hours. The added anthropogenic heat from BEM was shown to improve the temperature biases and errors for that simulation overall.