GEMS: An Airborne System for Urban Environmental Monitoring

Three-dimensional meteorological and air quality data collected over an urban environment would be valuable for air pollution or homeland defense applications. This paper describes a revolutionary, new observing system designed for environmental monitoring that will integrate MicroElectroMechanicalSystems or MEMS and nanoscale technologies. MEMS combine electrical functions with sensors and other mechanical devices embedded in semiconductor chips.

The concept, known as Global Environmental Micro Sensors (GEMS), features an integrated system of airborne probes that will remain suspended in the atmosphere for hours to days and take measurements of pressure, temperature, humidity, and wind velocity as they are carried by atmospheric currents. In addition to gathering meteorological data, the probes could be used for monitoring and predicting the dispersion of particulate emissions, organic and inorganic pollutants, ozone, carbon dioxide, and chemical, biological, or nuclear contaminants.

The current project, funded by the Universities Space Research Association’s NASA Institute for Advanced Concepts, focuses on studying the major feasibility issues associated with system design and development in the decadal time frame for a global GEMS measuring system. One phase of the project is to simulate GEMS with a mesoscale model on regional and local scales. The Advanced Regional Prediction System (ARPS) model is coupled with an inline Lagrangian particle model to examine deployment and dispersion of probes released into a small-scale urban-like environment at a grid spacing of 1 km. Simulated probes are released in the model and tracked as passive tracers using the ARPS three-dimensional wind components, as well as adjustments for the turbulent velocity fluctuations, settling effects, and precipitation scavenging.

Simulated observations from each probe location and time step are extracted from the ARPS model to provide an example of the type of data the probes would gather in an actual deployment. These data are analyzed to study possible deployment and dispersion patterns and to determine the utility of the probe meteorological data.

The paper will describe GEMS and present results of the mesoscale modeling study and probe deployment in the fine grid environment. The work is in progress and results will show the feasibility of using such a system at the urban scale for collecting meteorological data along with data on air pollutants and possible chemical, biological, or nuclear contaminants. While these initial simulation are not yet at the scale to model an actual urban landscape, it is a step in that direction. Our goal is to reduce the grid spacing of the mesoscale model below 1 km and to include high-resolution terrain and building profile data in future simulations.