On the Genesis and Evolution of the Summer 2013 Heat Wave Event In New York City: Observations and Modeling

Heat waves are becoming increasingly frequent and more intense a function of a changing and warming climate. These extreme weather events represent considerable high risks to human health and lives and to the energy infrastructure and merits reseach. This paper focuses on the detail analysis of a recent heat wave event that lasted from July 17th to July 20th, 2013 in the New York City Metropolitan region. Surface temperatures and wind conditions data from a dense network (over Manhattan and its surroundings) comprised of surface weather stations, wind profilers, and a Lidar. (from NYCMEtNet) were observed and analyzed. The observations indicate a maximum temperature during the event of 41.7degC (107degF) taking place in Queens, Borough, with daily heat indexes above 48degC (120degF). The thermal surface gradient observed at the time of maximum temperatures was 12degC (20degF) spatially extending for more than 100kms from midtown Manhattan. To further our understanding of the event, the Weather Research and Forecasting (WRF) mesoscale model coupled to a multi-layer urban canopy model was used to evaluate evolution of the heat wave. This urban parameterization considers thermal and mechanical effects of the urban environment including a building scale energy model to account for anthropogenic heat contributions. High resolution urban canopy parameters (UCPs) from the National Urban Database and Access Portal Tool (NUDAPT) were employed to initialized the model. Simulated results (with an inner horizontal grid-resolution of 1 km) were evaluated against the above observations. The thermal and drag effects of buildings, represented in the WRF multilayer urban canopy model, better estimated surface temperatures over NYC than the simplified versions. Simulations indicate that anthropogenic heat from the buildings is a major driver of the maximum temperatures. Sensible heat fluxes in excess of 200 W/m2 were estimated from the buildings contributing close to 3degC to the maximum temperatures. The paper will further discuss evolution of the thermal and boundary layers during the event.