Executive Summary
In November 2022, the Center for Multiscale Applied Sensing (CMAS) deployed 32 miniaturized Windsond radiosondes across downtown Houston to capture the three-dimensional structure of the city’s urban heat island (UHI). Unlike traditional weather balloons that require open fields and risk interference with air traffic, these lightweight sondes ride on small party balloons, reaching altitudes high enough to profile the layer of atmosphere most felt by residents. Data on temperature and humidity were streamed in real time to ground stations, enabling CMAS to build high-resolution maps of heat distribution above streets and buildings. This approach bridges critical data gaps for urban planners and public health officials, offering a scalable, rapid-deployment toolkit for monitoring UHI dynamics in complex cityscapes.
Key Learnings
- Urban heat islands trap daytime warmth, raising nighttime temperatures and impacting public health
- Conventional weather balloons are impractical in dense urban areas due to size and airspace constraints
- Miniature Windsond radiosondes can be launched from sidewalks using small party balloons
- Real-time temperature and humidity profiles enable detailed 3D mapping of urban microclimates
- CMAS leverages distributed sensing to improve predictive models around energy hotspots
- Rapid deployment of dozens of sondes provides a scalable method for city-wide UHI studies
Understanding Urban Heat Islands
Urban heat islands occur when concrete, asphalt, and buildings absorb solar energy by day and release it slowly at night. This effect creates temperature differences of several degrees Celsius between urban centers and surrounding rural areas, contributing to increased energy demand, air pollution, and heat-related health risks.
CMAS Initiative for Urban Sensing
The Center for Multiscale Applied Sensing (CMAS) is a multidisciplinary research center at Brookhaven National Laboratory that focuses on deploying networks of modern, distributed sensors in complex environments—urban centers, coastlines, and renewable energy sites. CMAS aims to acquire multi-parametric, multi-scale data to refine numerical models for weather and energy prediction around critical hotspots.
Deploying Windsond Radiosondes in Houston
In fall 2022, CMAS launched 32 Windsond sondes simultaneously across downtown Houston. Each sonde is a miniaturized weather instrument attached to a small, commercial helium balloon. Unlike giant weather balloons, these party-balloon platforms avoid navigable airspace and require minimal open ground:
“Typically, we launch giant weather balloons in open fields to measure temperature and humidity up to 24 miles in the sky. There isn’t sufficient space in cities for the giant balloons to rise without hitting obstacles, and they may rise through navigable airspace and disturb flight traffic. Instead, we tried to use miniaturized instruments that can be lifted by party balloons that don’t fly as high as weather balloons but fly high enough to capture data in the region of the atmosphere that impacts people the most.”
– Katia Lamer, Director of Operations and Assistant Scientist, CMAS
These sondes recorded vertical profiles of temperature and humidity up to several kilometers above street level and transmitted data back to mobile receivers for immediate analysis.
Data Integration and 3D Heat Mapping
By triangulating real-time sondes’ positions and environmental readings, CMAS constructed a three-dimensional heat-profile map of Houston’s urban canopy layer. This high-resolution dataset reveals temperature gradients above busy streets, parks, and water bodies, informing:
- Urban planning decisions for green spaces and reflective materials
- Localized energy-demand forecasting during heat waves
- Public health advisories for heat-vulnerable populations
Future Directions in Urban Microclimate Research
Building on Houston’s campaign, CMAS plans to replicate the mini-sonde network in other major cities. Integrating these airborne observations with ground sensors and satellite imagery will enhance predictive models for urban heat and pollution dispersion. Rapid, scalable deployments of Windsond sondes could become standard practice for real-time monitoring of city-wide microclimates.
Sources:
- BNL Center for Multiscale Applied Sensing, “Home,” Brookhaven National Laboratory. BNL | Center for Multiscale Applied Sensing
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