LAUSR

Abstract Heat waves are of serious health concern in highly populated urban areas due to combined heat stress and poor air quality impacts. In this study, we present an observation-based study of the heat-wave impacts on the planetary-boundary-layer (PBL) and air quality in summer 2017 in New York City (NYC). Synergy of remote sensing, in-situ observations with model forecast is applied to quantify and characterize the diurnal variation of PBL height (PBLH), ozone (O3) and PM2.5 during the heat wave period of June 11–13, 2017. The ground O3 concentration attains a maximum of 110 ppb largely exceeding the U.S. National Ambient Air Quality Standard (NAAQS) while the organic carbon (OC) and sulfate aerosols show a coincident increase. The higher O3 in the downwind suburb than those in the urban area are likely associated with the urban pollution transport and local meteorological condition. We observe a dramatic and consistent PBLH growth from 0.5- to 2.5-km at 11:00–13:00 local time from the turbulence-based and aerosol-based PBLH estimate by co-located ceilometer, wind lidar, and aerosol lidar measurement. Regional and high residual layers of aerosols at night are observed from the NASA space-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Cloud and Aerosol Transport System (CATS) lidars. Furthermore, we evaluate the NOAA National Air Quality Forecasting Capability (NAQFC) products of PBLH, temperature, O3, PM2.5 and NOx (NO2+NO) with the observations. Under the strong convective PBL condition, all the products above show good agreement between the NAQFC predictions and observations. However, in the early morning and night, the model shows dramatic discrepancies with an underestimate of temperature, PBLH and O3 but an overestimate of PM2.5 and NOx. Such bias may be associated with the improper representations of vertical mixing, complex chemical processes and emissions in the model.