Integration of the WUDAPT, WRF, and ENVI-Met Models to Simulate Urban Heat Island Mitigation Strategies in Downtown San Jose, California

Development of site-specific solutions to address UHI impacts has been hindered by the lack of data exchanges between existing research platforms that, when combined, have the capacity to characterize significant variabilities within the urban environment. Herein we investigate the downscaling of urban scale model outputs used as inputs to neighborhood scale models. This is achieved by coupling WUDAPT (Level 0) LCZ land cover data as input to an urbanized WRF model to generate meteorological parameters that can be used in ENVI-met to generate building scale temperature fields. The study focused on a portion of San Jose, with the primary interest on 1 September 2017, the hottest day in California history with a heat-wave high temperature of 42C (108F) in San Jose.

Three types of ENVI-met simulations were carried out to evaluate three sources of input background meteorological data: (i) “Urban-WRF” with the SLUCM urbanization parameterization and with WUDAPT Level-0 urban land-cover data, (ii) “Default-Urban” with WRF’s default configuration, which uses a simpler urban “roughness length” parameterization with only look-up table urban land-cover information, and (iii) “San Jose Airport, ”the most commonly used ENVI-met method, with only observed data from the nearest meteorological surface site. The models were then used for three mitigation strategies: 1) multi-tiered vegetation-tree cover and green facades, 2) high albedo rooftops, 3) extensive built shade structures. Each mitigation strategies was simulated independently, followed by a combined simulation.

The study found that the LCZ Level-0 driven Urban-WRF model performed best at reproducing observed nighttime 1-m air temperature values. The results from the mitigation strategy evaluation showed that vegetation is the most effective methods, which confirms the findings of previous studies that used less sophisticated approaches. Results also show synergistic effects from the combined strategy,

This investigation aimed to create a method to bridge the information flow between multiple research methods (WUDAPT, WRF, and ENVI-met) to create a useful tool for development of site-specific meteorology to inform mitigation strategies and urban planning efforts. Professional fields (i.e., landscape architecture, architecture, and city planning, urban design) are becoming more reliant on data derived from computer modeling to guide their decision-making process. Use of this combined model suite is a step in the right direction.