Recent Heavy Precipitation in the Vicinity of the Great Salt Lake: Just How Unusual?

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Abstract

A long time series (1863–1984) of areal average precipitation in the vicinity of the Great Salt Lake is shown to be highly correlated with the Great Salt Lake levels. This time series is used to assess the unusual recent episode of heavy precipitation (1981 through 1984). The Palmer Drought Severity Index (PDSI) is used to identify wet spells of weather. The cumulative excess precipitation during each wet spell was analyzed using stochastic frequency analysis. The analysis indicates that there were two very important wet spells in the time series, the beginning and ending in the 1860s and the most recent wet spell which began in late 1981. The analysis suggests that the recent heavy precipitation is not unexpected. Furthermore, if the climate of the past 122 years is representative of the climate over the next 100 years, another wet spell can be anticipated to be at least as severe, in terms of excess precipitation, as the 1981–84 wet spell. Whether lake levels can recede to sufficiently low levels to prevent new record high levels during the next severe wet period is uncertain, but it must be considered in any long-term risk assessment strategies.

Abstract

A long time series (1863–1984) of areal average precipitation in the vicinity of the Great Salt Lake is shown to be highly correlated with the Great Salt Lake levels. This time series is used to assess the unusual recent episode of heavy precipitation (1981 through 1984). The Palmer Drought Severity Index (PDSI) is used to identify wet spells of weather. The cumulative excess precipitation during each wet spell was analyzed using stochastic frequency analysis. The analysis indicates that there were two very important wet spells in the time series, the beginning and ending in the 1860s and the most recent wet spell which began in late 1981. The analysis suggests that the recent heavy precipitation is not unexpected. Furthermore, if the climate of the past 122 years is representative of the climate over the next 100 years, another wet spell can be anticipated to be at least as severe, in terms of excess precipitation, as the 1981–84 wet spell. Whether lake levels can recede to sufficiently low levels to prevent new record high levels during the next severe wet period is uncertain, but it must be considered in any long-term risk assessment strategies.

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