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How hot is it, really? ASU undergrad applies publication impact scale to weather patterns

Phoenix downtown skyline at night from 7th Street and 202.

A view of the downtown Phoenix skyline at night. Photo copyright by Arizona Board of Regents

July 15, 2019

There are a few things in life upon which we can rely, and one of those things is that Phoenix is hot in the summer. But how hot? It’s a more complicated question than you might think. Certainly we can calculate average temperatures and record the highs and lows, but adding another element may show a more complete picture.

Christopher Ramirez, a biophysics major at Arizona State University, has introduced an interesting new way to measure ongoing weather conditions in specific areas not simply based on how hot it gets, but how often.

This new model is based on the “h-index," a metric used to represent the impact of a scientist or scholar over the course of their career.

Analyzing the individual’s (or group’s) overall body of work, the h-index counts both the number of publications and also how many times each work has been cited by other researchers. The magic is in where those numbers match. The final score is calculated by determining the highest number of publications which have been cited at least that same number of times.

So, for example, an h-index of 15 would mean that a scientist published 15 papers that have been cited at least 15 times each.

Working with ASU professors Michael Treacy, of the Department of Physics, and Michael O’Keeffe, of the School of Molecular Sciences, Ramirez tackled the challenge of applying this same analysis to city weather patterns to form a heat index, or H-index.

Using the National Oceanic and Atmospheric Administration (NOAA) database, Ramirez discovered that in Phoenix during the year 2018, there were 102 days where the highest temperature was at least 102 degrees, giving it an H-index of 102.

Yuma’s H-index read in at 103, Tucson at 97, and Flagstaff at 79. Death Valley, California, came out on top, so to speak, with an H-index of 109.

One of the most crucial components of producing a relevant and meaningful H-index is a continuous record of day-to-day maximum temperatures. Interestingly enough, in the NOAA database, airports seemed to have the most reliable and complete data, allowing Ramirez to expand his research to international cities, tracing back to 1950.

After exploring the higher end of the thermometer, a similar index can be constructed to measure lowest temperatures for a coldness index — the C-index. Analyzing the number of days in which the lowest temperature reaches below the freezing point of water, or 32 degrees Fahrenheit.

Perhaps unsurprisingly, daily temperatures recorded at the Phoenix airport give a typical C-index of zero, as it very rarely freezes there. However, farther into the suburbs can have a C-index of about 2 – meaning that at least two days in the year had dropped to 30 degrees Fahrenheit or lower.

For a closer look at where cities across the world fall on the H and C index, visit the full research article, which appears in EOS Earth & Space Science News.

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