City Creek Nature Notes – Salt Lake City

March 2, 2017

February 28th

Filed under: Weather — canopus56 @ 5:52 pm

End of Meteorological Winter

External Link to Image

Temperature and Snow at Salt Lake Airport. Source: Weather Warehouse (2017) (data).

6:00 p.m. Another day of snow showers in the morning followed by warm sunlight in the afternoon. A local university climate scientist recently termed December, January, and February, Utah’s “meteorological winter”, and that informal season ends today.

During January, I spent time marshaling and analyzing weather data from stations in and around the canyon with the idea of determining whether the signal of global climate change could be seen. There are only three weather stations with a sufficiently long record beginning in the 1940s in order to compare pre-1990 weather to weather from 1990 to the present: Alta, the Mountain Dell Reservoir Station, and the Salt Lake International Airport. Of these Alta showed no statistically significant difference in temperature, snowfall or precipitation from before as compared to after 1990. Mountain Dell readings had to be discarded because the station was not recording from 1994 to 1996 and during a key extreme wet weather event. That left Salt Lake International Airport weather data, which for both before and after 1989 are normally distributed for annual temperature and snowfall. Annual and monthly precipitation at the airport showed no statistically significant difference. Annual temperature showed a significant increase in temperature and decline in snowfall. But neither of those, or similar trends at Mountain Dell, can be attributed to global climate change. In the case of the airport, its size and location in a valley that has undergone major growth since 1940 mean that the rise in temperature and decline in snowfall might be attributed to the urban heat island effect. Mountain Dell is similarly located next to a major freeway whose annual automobile traffic has increased to 22 million trips per year. The heat from cars are an alternative explanation for the rise in temperature at the reservoir. Both may be explained by the drought cycle associated with the Pacific Quasi-Decadal Oscillation (Feb. 7th). Relative to California, which has severed severe droughts in the last few years, the PDQO has kept Utah total precipitation relatively higher (IWWA Project). But the trends at these local stations near City Creek Canyon are consistent with the larger Intermountain West snowpack and temperature picture: temperatures are rising, the snowpack is declining, and snow packs are melting earlier in the year (IWWA Project (analysis of weather stations); Harpold et al (analysis of 202 SNOTEL stations)).

What I learned from this exercise in analysis is that if global warming is detectable, weather data must come from a network of weather stations located at a far distance from any urban area so the effect of nearby anthropomorphic noise does not confound the information. Changes in snow fall will be best seen at mid-elevations, but not at the highest peaks. Locally, stations in the Unitas, but outside the canyon, may be the best candidates.

In Thoreau’s “Journal” on February 28th, 1855, he notes how runoff has created a new ravine. On February 28th, 1860, he hears dried seeds rattling within a pod. On February 28th, 1861, he observes the roots of grass extending down two feet below the surface where erosion has washed a bank away.

On February 28th, 1901, the Red Bird Mine reported finding a view of good grade lead ore (Deseret News).


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