The New York State Mesonet (NYSM) is a network of 126 standard environmental monitoring stations deployed statewide with an average spacing of 27 km. The primary goal of the NYSM is to provide high quality weather data at high spatial and temporal scales to improve atmospheric monitoring and prediction, especially for extreme weather events. Compared with other statewide networks, the NYSM faced considerable deployment obstacles with New York’s complex terrain, forests, and very rural and urban areas; its wide range of weather extremes; and its harsh winter conditions. To overcome these challenges, the NYSM adopted a number of innovations unique among statewide monitoring systems, including: (1) Strict adherence to international siting standards and metadata documentation; (2) A hardened system design to facilitate continued operations during extreme, high-impact weather; (3) A station design optimized to monitor winter weather conditions; and (4) a camera installed at every site to aid situational awareness. Completed in spring 2018, the network provides data and products to a variety of sectors including weather monitoring and forecasting, emergency management, agriculture, transportation, utilities, and education. This paper focuses on the standard network of the NYSM and reviews the network siting, site configuration, sensors, site communications and power, network operations and maintenance, data quality control, and dissemination. A few example analyses are shown which highlight the benefits of the NYSM.

The Long Island Sound Tropospheric Ozone Study (LISTOS) was organized to investigate ozone formation and transport in the New York City metropolitan area and locations downwind. During LISTOS, the University at Albany Atmospheric Sciences Research Center (ASRC) mobile laboratory was used for measuring surface O3, NO2, and aerosol number and mass concentration. Sharp O3 concentration gradients, with ΔO3 Δy−1 over 15 ppb km−1, were measured both at and near the land‐water interface and on the highway on days characterized by high regional O3 concentrations. These large O3 gradients at or near the land‐water interface, and in air masses relatively low in NO2, are shown to be influenced in part by the transport of highly oxidized air masses via sea breeze circulation and convergence with gradient flow. On the highway under regionally high O3 concentrations, strong anticorrelation (R2 = 0.78, p < 0.05) between O3 and NO2 and an absolute slope less than 1 suggested that Ox concentrations (O3 + NO2) increased with increasing NO2. Overall, the on‐road measurements made during LISTOS help to better characterize the interaction between the emitted pollution and the meteorological conditions on Long Island, thereby having potential policy implications.

Strict emission control policies implemented in two megacities of New York City (NYC) and Beijing show impacts on the non-linear relationship of their ozone (O3) and fine particulate matter (PM2.5) during summertime. Here we show these non-linear O3-PM2.5 relationships including a positive linear part reflecting the O3/PM2.5 co-occurrence and a negative power function part reflecting the O3 formation suppression by PM2.5 based on the multiyear surface observations. The control policies targeting sulfur dioxide and PM2.5, then volatile organic compounds and nitrogen oxides, changed the PM2.5 chemical composition which resulted in an increased linear slope that indicates a weaker O3 control effect than occurred for PM2.5. These policies also enhanced the relative PM2.5 suppression effect as shown by an increase in the power function coefficient. Model simulations suggest that regional equal percentage emission reductions for Beijing and other Chinese megacities will be necessary to avoid further increase in the O3/PM2.5 linear slope and continuing occurrences of high levels of ozone.