UrbanNet – The Next Generation of DCNet

ARL’s Efforts in Urban Climate and Meteorology Monitoring

Dating back to the tragic terrorist 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 terrorist target location as Washington, DC were a distinct possibility. DCNet grew out of a recognition by dispersion scientists within the Air Resources Laboratory (ARL) of NOAA 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? 

As such, DCNet was a meteorology research program established by NOAA for the DC/National Capital Region as a response to potential threats following the September 11, 2001 attacks on the U.S. Initial goals of DCNet were to explore variations in model inputs for both numerical weather prediction (NWP) as well as atmospheric transport and dispersion models (AT&D), to assimilate urban observations into both numerical weather prediction and atmospheric transport models, and the provision of real-time meteorological observations over the greater NCR to support current numerical weather prediction models as well as provide the driving meteorological observations for atmospheric transport and dispersion models.

The current station locations for DCNet are as follows:

  • U.S. Depar of Commerce – Herbert C. Hoover Building  Washington DC – a dual system;
  • Washington DC’s Emergency Management Agency in SE Washington DC;
  • The headquarters of the National Education Association in Washington DC;
  • The Washington DC Government’s Frank Reeves Municipal Center;
  • Howard University in Washington DC; and
  • C-SPAN towers in upper northwest Washington, DC;

DCNet Becomes UrbanNet

Beginning in 2023, DCNet has begun undergoing a revitalization to better assess the changed urban landscape in the DC metro area in recent years, and has been re-named UrbanNet to reflect its changing mission and dependent on resources its ability to be portable to other urban settings. In the near future, the UrbanNet system will add new and upgraded sensors to better measure meteorology in the urban environment. New sensors will be employed to better measure urban heat stress, atmospheric pressure, wind speed and direction, 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 will also measure air and surface temperature, reflected heat, and solar radiation, and will also 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.

Potential UrbanNet Stations

The Silver Spring Metro Center 3 (SSMC-3) building on the Silver Spring, MD campus at one time hosted a DCNet site, and the building was visited to determine its suitability as a future UrbanNet site and things look quite promising on that front. Additionally, a test system may be installed on the roof of the NOAA Center for Weather and Climate Prediction to allow for more effective testing of new and revised sensors and firmware as appropriate, given its proximity to the ARL division in College Park, MD. Some other sites may also be evaluated and are as yet still to be determined. 

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.

Assembly of the tower atop the Department of Commerce HCHB rooftop.
Dr. Ariel Stein talks with Myah Rather and Drs. Sen Chiao and Ricardo Sakai of Howard University.
NOAA and NIST installed a Doppler lidar instrument on top of the Department of Commerce’s Herbert Clark Hoover Building in Washington, D.C. on April 16, 2021, for a research project studying urban greenhouse gas emissions. Image Credit: NOAA's Scott Sandberg and NIST's Tyler Boyle.