Abstract
Abstract. The characteristics of winter season persistent deep stable layers (PDSLs) over Utah's Salt Lake Valley are examined using 30-year twice daily rawinsonde soundings. The results highlight the basic climatological characteristics of the PDSLs, including the strengths of the inversion, the frequency of the occurrence, and the duration of the events. The data analyses also reveal linear trend, interannual variability, as well as the relationship between the interannual variability of PDSLs and the variability of large-scale circulations. Finally, the study investigates the large-scale atmosphere conditions accompanying the formation and destruction of the PDSL episodes.
Highlights
Persistent deep stable layers (PDSL) are frequent wintertime phenomena in basins and valleys of the Intermountain West of the United States (Wolyn and Mckee, 1989; Reeve and Stensrud, 2009)
Weak PDSLs are much more frequent than the stronger events except for four winters when the frequency of moderate PDSLs slightly exceeds that of weak ones
How long do PDSL events last? As shown in Fig. 4, a PDSL may last from 1.5 day (3 consecutive 12 h soundings) to a little over 3 weeks (42 consecutive 12 h soundings)
Summary
Persistent deep stable layers (PDSL) are frequent wintertime phenomena in basins and valleys of the Intermountain West of the United States (Wolyn and Mckee, 1989; Reeve and Stensrud, 2009). The strong static stability decouples the air within the basin/valley from layers aloft, which often leads to stagnation and limits atmospheric dispersion (Vosper and Brown, 2008; Smith et al, 2010). We perform climatological analyses of winter season PDSLs over the Salt Lake Valley (SLV) in Utah, USA. The analysis employed winter-season (defined here as the beginning of November through the end of February), twicedaily rawinsonde soundings launched from the Salt Lake. 0.0033 ◦C m−1 (Z1 and Z2 are 850-hPa and 700-hPa geopotential heights) is satisfied by at least three consecutive soundings This is equivalent to the condition that the temperature lapse rate between 850 and 700 hPa is less than the moist adiabatic lapse rate; in other words, the atmosphere is absolutely stable.
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