Have you ever wondered how rainfall is actually measured? Technical instruments, called rain gauges, are designed to collect and accurately measure rainfall during wet weather events. However, a rain gauge can only provide a specific rainfall measurement for the limited geographic area where the gauge is located.
On the flip side, radar systems, often used in weather reports, do not measure rainfall directly, but rather they detect the intensity of microwave energy reflected by raindrops, called reflectivity. Through the use of a mathematical formula, the reflectivity of the raindrops can be converted by the radar system into rainfall estimates for a particular defined area.
Neither measurement technique is perfect, but when the two are combined—when radar estimates are calibrated with actual rain gauge data—a highly accurate and valuable source of rainfall data can be calculated over large geographic areas.
Because engineers and planners addressing the wet weather issue need this level of accuracy, 3 Rivers Wet Weather created the calibrated radar rainfall system in 2001. Communities throughout Allegheny County use this data—provided in both real-time and historical formats—to design more cost-effective solutions to reduce or eliminate sewage overflows and improve stormwater management.
The NEXRAD radar (located in Moon Township) data is calibrated with the rain gauge measurements collected during the same time period and rain event for every square kilometer in Allegheny County. The resulting rainfall data is equivalent in accuracy to having 2,276 rain gauges placed across the County.
Currently, this site offers search, download, and mapping capability for rainfall data in three buckets:
- Real-time Rainfall data: provisional rainfall data for both rain gauges and radar pixels. Real-time gauge data is sourced from Datawise,and pixels are sourced from Vieux Associates. This data is updated every 15 minutes.
- Historical Rain Gauge data: QA/QC'd rain gauge data, usually available within 30-60 days. QA/QC is performed by ALCOSAN and 3RWW.
- Calibrated Radar Rainfall data: QA/QC'd, gauge-adjusted radar rainfall observations, typically available within 30-60 days. Calibration is performed by Vieux Associates.
The rainfall data is served up from 3RWW's Data API. Currently a few low-level API functions are documented and accessible through https://trwwapi.herokuapp.com/rainfall/.
This project is a work-in-progress. We're currently looking to replicate the workflows of the original rainfall downloads site. In the future and with feedback, we'll build out new ways to explore and view the rainfall data. We'll also provide resources for helping you integrate this data into your workflows and use it in your tools.
This project was bootstrapped with Create React App.
Use Node NPM, Yarn, or PNPM to install dependencies. While we use PNPM, the commands shown the sections below are the same with any of those tools.
NOTE: dependencies as spec'd are currently only building with Node V16.
Run git clone https://github.com/3rww/rainfall.git to clone this codebase.
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