ARL’s Efforts in Urban Climate and Meteorology Monitoring
Dating back to the tragic events of September 11, 2001, there was a realization on the part of the homeland security community that chemical, biological agent, or radioactivity releases in a prime target location such as Washington, DC were a distinct possibility. UrbanNet, originally DCNet, grew from the recognition by dispersion scientists within the Air Resources Laboratory (ARL) that society now faces a critical question. How do we forecast dispersion in urban areas and in cities when the meteorological data used by the weather forecasting community are from locations outside the area of probable concern?
The UrbanNet system employs sensors to measure urban heat stress, atmospheric pressure, wind speed and direction, and precipitation, including precipitation gauges using both a tipping bucket and a higher precision weighing gauge employed by the U.S. Climate Reference Network. Improved measurements of urban precipitation trends are crucial for an array of planning activities. Other sensors measure air and surface temperature, reflected heat, and solar radiation, and employ a monitoring camera to assist with both the quality assurance of the data as well as to monitor any special weather conditions that may develop.
UrbanNet stations are currently located at at Howard University in Washington D.C. and the U.S. Department of Commerce Herbert C. Hoover Building in Washington D.C., which has two towers – one at the north and south ends of the building.
Potential UrbanNet Stations
Other sites being considered for stations include:
- Washington D.C. Emergency Management Agency in southeast Washington D.C.
- NOAA Center for Weather and Climate Prediction in College Park, MD
- C-SPAN towers in upper northwest Washington D.C.
Urban Emissions of Greenhouse Gases
Urban emissions of greenhouse gases represent a large portion of anthropogenic greenhouse gas contributions to the global carbon budget and UrbanNet will play a role here as well. As the global population increasingly lives in cities, the proportion of anthropogenic emissions in urban areas relative to rural regions is increasing. Systematic biases in urban emissions can significantly alter regional and global emissions and climate projections. As such, ARL has undertaken a project to identify biases and uncertainties in greenhouse gas emissions inventories in urban areas. While the majority of emissions inventories are created through a bottom-up approach, this project is evaluating and improving emissions inventories through a top-down approach utilizing observations of greenhouse gases and an inverse modeling system employing the HYSPLIT model. Improvements to greenhouse gas emissions inventories are first being performed for the Washington, DC – Baltimore, MD metropolitan area. After demonstrating the usefulness of this approach, this work will be expanded to other urban areas.
These new emissions estimates will be used to evaluate existing greenhouse gas emissions inventories, assess how greenhouse gas emissions are changing over time, and identify large emissions sources for possible emissions reduction strategies. This work can be used to assess if greenhouse gas emissions reduction plans are on pace to be met as well as to improve emission reduction strategies. The improved emissions inventories can also be used in the initialization of climate models. In addition, greenhouse gas emissions inventory improvements can be used to update emissions inventories used in air quality models by applying known emissions ratios between greenhouse gases and other trace gas emissions. This project demonstrates how an inversion modeling system performs in the Washington, DC-Baltimore, MD area and how it can be duplicated for other cities to systematically improve greenhouse gas emissions estimates for urban areas more widely. Outcomes include an improved (1) understanding of urban greenhouse gas emissions as well as their transport, dispersion and uncertainty that can be applied to ecological modeling, and (2) improved emissions inventories for climate models. Small aircraft, coupled with mobile ground measurements, will be used to make measurements of air pollutants (O3, NOx, CO, SO2, and aerosols) and greenhouse gases (CH4 and CO2). Observations will be taken over the Washington-Baltimore area to document changing level of GHG and pollutant emissions as compared to the COVID19 economic slowdown. Further analysis will work to pinpoint source emissions and variations. The results from this project will provide policy relevant science information to federal and state regulatory agencies to help mitigate greenhouse gas emissions and implement strategies to control air pollution, with ultimately an improved understanding of air pollutants (O3, NOx, CO, SO2, and aerosols) and sources of greenhouse gases (e.g., CH4 and CO2) in the Mid-Atlantic region.
