City Creek Nature Notes – Salt Lake City

February 7, 2017

February 7th

Filed under: Owl, Weather — canopus56 @ 8:44 pm

Distant Precipitation Causes

Corrected February 10th, 2017

External Link to Image

Pacific Quasi-Decadal Oscillation. Source: ENSO Blog Team, NOAA and National Climate Data Center. (2014).

5:30 p.m. It has rained for part of the morning and the canyon is full of earthy smells. Temperatures nearly reached sixty degrees Fahrenheit in the valley, and into the forties in the canyon. The top layer of the canyon bottom snow has disappeared by half and the hard rock of the bottom ice layer deposited in January is beginning to melt. As I exit the canyon in twilight, an unseen lone owl calls.

With respect to the heavy snowfall of January (Feb. 1st), variable annual precipitation in the canyon and northern Utah is related to remote, distant ocean temperature patterns. In 1997, Hare, Mantua and colleagues identified an ocean surface temperature pattern in the northern Pacific ocean denoted the “Pacific Quasi-Decadal Oscillation” (PQDO). Although less known than the El Nino and La Nina events in the south western Pacific, the PQDO has more significant and longer term implications for Utah and canyon snowfalls and stream flows. In the “warm” phase of the PQDO temperature pattern, ocean waters in eastern Pacific off Japan cool and waters off the western Pacific near the coast of the United States warm. Conversely, in the “cool” phase, ocean waters in eastern Pacific off of Japan warm and waters off the western Pacific near the coast of the United States cool. Both phases forces the jet stream into a new configuration, and cycles between phases occur in approximately 12 year intervals. Utah has its highest precipitation when the oscillation pattern changes from its warm to the cool phase and its greatest droughts when the oscillation changes from the cool phase to the warm phase. Those transitions are lagged about three years after the peak or troughs of the proceeding warm or cool phase. Previous transitions from the warm to cool phase occurred in 1925, 1947, 1977, and 1997. Since 1997, the oscillation has been stuck in an extended cool, or drought phase (ENSO Team, PDO Chart), and in 2016, meteorologists disagree on whether the cool phase is again transitioning back into the warm, and hence for Utah, a higher precipitation phase and rising Great Salt Lake levels.

In 2010, Wang and colleagues at the Utah State University associated the Pacific Quasi-Decadal Oscillation with a northern Utah three-year leading precipitation and a six year leading level of the Great Salt Lake (Wang, Fig. 4 at 2166). In the association with the level of the Great Salt Lake, PQDO warm phase peaks are associated with the lowest lake levels and PQDO cool phase troughs are associated with the highest lake levels. In 2013, DeRose, Wang and colleagues used tree rings to reconstruct the level of the Great Salt Lake back to 1429, and they associated the lake’s level to the pacific oscillation back to 1700. The PQDO’s connection to Utah precipitation and the Great Salt Lake is an association, not a cause, and the PQDO itself is an effect without a fully understood mechanism of action. In recent years, the PQDO has been good for Utah. While California has suffered severe drought, the PQDO has kept annual precipitation relatively higher in Utah (IWWA Project). But the Pacific Quasi-Decadal Oscillation illustrates that long-term changes in weather in the canyon, including annual precipitation, snowfall and stream flow, are related to, if not controlled by, distant events in the eastern Pacific Ocean 6,000 miles away. These distant events affect the abundance of plants and animals that I see during daily visits to the canyon.

In Thoreau’s “Journal” on February 7th, 1859, he observes lichens. On February 8th, 1841, Thoreau states that in keeping a nature journal, he writes for the purpose of appreciating nature and not for the sake of writing itself.

On February 7th, 1918, the City authorized $1,000 requested by Commissioner Clarence C. Nelson to plant trees in City Creek Canyon (Salt Lake Herald). On February 7th, 1900, the mayor and the City laws committee was authorized to seek through the U.S. Congress cession to the City of all federal lands in City Creek, Emigration and Parley’s Canyons (Deseret Evening News). City Engineer Kesley obtained approval to replace the City Creek water main with a larger 32-inch pipe. The City Public Grounds committee declined to lease land in City Creek for a gravel pit (id).


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