Temperature Inversions Forecasts

This dataset contains predictions of whether temperature inversions will occur at locations in Allegheny County. 

**This dataset is still under active development and should be considered to be in "beta".**

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## Motivation ##
Temperature inversions occur when there is a warmer layer of air above the air at or near ground level. This represents a reversal of the normal flow of heat near the earth and results in the cooler air being trapped near the ground. Temperature inversions can lead to the formation of fog or dew. Pollution or smoke from fires, which would rise and dissipate in the atmosphere under normal conditions, become trapped near the ground in a temperature inversion, potentially leading to hazardous concentrations of pollutants in the air. 

This dataset was extracted from NASA's [Goddard Earth Observing System Forward-Processing (GEOS-FP)](https://gmao.gsfc.nasa.gov/GMAO_products/NRT_products.php) system as a collaboration between NASA's Goddard Space Flight Center and the Western Pennsylvania Regional Data Center, to provide access to 1-day, 3-day, and 5-day predictions of temperature inversions in Allegheny County.

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## Preprocessing/Formatting/Methodology ##
This dataset is generated using data-processing scripts written by partners at NASA Goddard Space Flight Center. The scripts extract from the GEOS-FP model the predicted air temperature as a function of latitude/longitude/date/height, and then, starting near surface level, search upward for the height of the local maximum in air temperature. This determines whether a temperature inversion is expected.

Each record is a prediction of whether there will be a temperature inversion, for a particular day at 12pm UTC (7am EST) within five days after the prediction, and for a particular cell in a coarse grid overlaying Allegheny County. If an inversion is predicted, the height of top of the inversion above the ground and the temperature difference between the ground and the top of the inversion are given, as well as an estimate of the inversion strength on a scale of 0 to 4 (where the strength of the inversion is calculated based on the value of the temperature difference). For some locations, we've also added the name of a place (e.g., "Pittsburgh" or "Monroeville") within that cell, to make look-ups easier.

Additionally, we've created forecast maps for the region and 5-day timeline forecasts (for particular locations) of both inversion strength and PM2.5 concentration.

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## Known Uses ##
If you are using this dataset, please write to the data steward (listed below) and let us know! Your stories support the development of future datasets like this.

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## Recommended Uses ##
This data could provide an early-warning system for certain kinds of unhealthy air-quality events, such as dangerously high PM<sub>2.5</sub> levels from wildfire-induced smog or pollution, trapped near the ground.

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## Known Limitations/Biases ##

The spatial resolution of the forecast is pretty coarse.

To validate the forecast, a comparison was made of its predictions with actual temperature-inversion measurements made by weather balloon (or sodar/RASS acoustic upper air profiler) by the Allegheny County Health Department Air Quality Office. The results are shown in [this table](https://data.wprdc.org/dataset/temperature-inversions/resource/5ac4467e-a6de-4055-9111-9d83fb6584b4), which is accompanied by some additional analysis. When the 1-day forecast predicted a strong or moderate inversion, there was about a 90% chance that it was historically correct, and when the 3-day or 5-day forecast confirmed this forecast for the same date, the accuracy increased, with more than 96% historical accuracy when confirmed by the 5-day forecast.

Also, sometimes the model results can not be computed on the expected schedule. (These delays are reported on the ["geos5-fp-users" mailing list](https://gmao.gsfc.nasa.gov/gmao-products/geos-near-real-time-data-products/).) In these instances, the WPRDC's automated processes fall back to the previous day's forecasts; the `forecast_version` field provides the date and hour that the forecast simulation was started.

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## Related Datasets ##

The Allegheny County Health Department's measurement of pollutant concentrations (and other parameters) at several measurements stations are published in [the Allegheny County Air Quality dataset](https://data.wprdc.org/dataset/allegheny-county-air-quality).

The WPRDC is also publishing [a dataset that forecasts concentrations of three air quality parameters](https://data.wprdc.org/dataset/air-quality-forecast
): carbon monoxide (CO), nitrogen dioxide (NO2), and fine particulate matter (PM2.5).

Allegheny County is now publishing [a dataset with the measured temperature inversions](https://data.wprdc.org/dataset/air-temperature-inversions), which allows new forecasts in this dataset to be checked against real data.

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## Credits ##
This work is the result of a collaboration between the WPRDC and NASA's Goddard Space Flight Center. This dataset would not have been possible without the efforts of NASA Goddard Space Flight Center personnel to apply NASA's atmospheric models and domain expertise to the problem of forecasting temperature inversions, yielding this prototype forecast, tailored to Allegheny County. Thanks also to Jason Maranche and Angela Wilson of the Allegheny County Health Department's Air Quality Program for providing us with, and helping us understand, their historical temperature-inversion measurement data (used to validate the predictions).

Tags: NASA, _etl, air quality, forecast, inversions, prediction, temperature inversions, weather
Organization: Western Pennsylvania Regional Data Center