Advected Air Mass Reservoirs in the Downwind of Mountains and Their Roles in Overrunning Boundary Layer Depths Over the Plains

Pal, Sandip; Lee, Temple R.

doi:10.1029/2019gl083988

Cited by 7 publications

(6 citation statements)

References 42 publications

(63 reference statements)

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“…Among the USCRN sites used in this study, the mean wilting point and field capacity was 11.7% ± 3.3% and 26.4% ± 6.1%, respectively. While making the selection of these sites, we ensured that the IGRA sites were (1) far enough from the coast so that the impact of the marine boundary layer was negligible (Pal & Lee, 2019a) and ( 2) not influenced by the elevated mixed-layer off mountains (Pal & Lee, 2019b). The distance between the IGRA and USCRN sites varies from 58-258 km (Table S1).…”

Section: Methodsmentioning

confidence: 99%

The 2019 Mississippi and Missouri River Flooding and Its Impact on Atmospheric Boundary Layer Dynamics

Pal

Lee

Clark

2020

Geophysical Research Letters

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In spring 2019, a catastrophic flood occurred along the Missouri and Mississippi River basins in the United States, which was characterized as the longest lasting flood since the Great Flood of 1927. The 2019 flooding resulted in extremely wet soils for 3–4 months over the Great Plains. Using rawinsonde‐derived atmospheric boundary layer depths (BLDs) and in situ soil moisture (SM) data sets at 10 sites located meridionally across the two river‐valleys, we investigated the SM controls on regional‐scale BLDs during spring 2019. The impact of spring flooding on atmospheric boundary layer dynamics is reported via regression analyses between daily SM and BLDs yielding statistically significant negative r (p < 0.0012) with substantial spatial variability (r: −0.25 to −0.70). Results suggest (1) the strengthening of the negative SM‐BLD relationship in the wake of extreme flooding and (2) positive SM anomalies of 0.05–0.12 m3 m−3 resulted in negative BLD anomalies (−100 to −400 m) compared to 8‐year means, confirming the impact of perturbed land atmosphere feedback processes (LAFP). These results offer a test bed for developing better numerical models with advanced representations of LAFP.

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Section: Methodsmentioning

confidence: 99%

The 2019 Mississippi and Missouri River Flooding and Its Impact on Atmospheric Boundary Layer Dynamics

Pal

Lee

Clark

2020

Geophysical Research Letters

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“…As mentioned, we typically observed deeper zi in the pre-frontal sector compared to the post-frontal sector. However, for two sites in winter (i.e., Topeka, KS in 2014 and Rapid City, SD in 2016), contrasting results were found (i.e., deeper zi in the post-frontal sector), likely related to the impact of advection from the mountainous regions, which has been discussed in previous studies (e.g., Stensrud 1993;Pal and Lee 2019b). In general, complex terrain often significantly impact the representation of the ABL, even in the absence of frontal boundaries (e.g., Pal et al 2016;Rotach et al 2022).…”

Section: A Zi Variability In Pre-and Post-frontal Sectors In Summer A...mentioning

confidence: 68%

“…We also note that Dodge City (791 m MSL) is located closer to the Rocky Mountains than Topeka (268 m MSL), and thus some impact of advection on the zi measurements by the adjacent complex terrain during the frontal passages at Dodge City cannot be ruled out (e.g., Stensrud 1993;Pal and Lee 2019b).…”

Section: A Zi Variability In Pre-and Post-frontal Sectors In Summer A...mentioning

confidence: 93%

Empirical Evidence for the Frontal Modification of Atmospheric Boundary Layer Depth Variability over Land

Clark

Pal

Lee

2022

Journal of Applied Meteorology and Climatology

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Despite many observational studies on the atmospheric boundary layer (ABL) depth (zi) variability across time scales (e.g., diurnal, seasonal, annual, and decadal), zi variability before, during, and after frontal passages over land, or simply zi variability as a function of weather patterns, has remained relatively unexplored. In this study, we provide an empirical framework using 5-years (2014-2018) of daytime rawinsonde observations and surface analyses over 18 central and southeast US sites to report zi variability across frontal boundaries. By providing systematic observations of front-relative contrasts in zi (i.e., zi differences between warm and cold sectors, Δzi = zWarmi − zColdi) and boundary-layer moisture (i.e., ABL-q) regimes in summer and winter, we propose a new paradigm to study zi changes across cold front boundaries. For most cases, we found deeper zi over the warm sector than the cold sector in both summer and winter, though with significant site-to-site variability in Δzi. Additionally, our results show a positive ΔqABL (i.e., frontal contrasts in ABL-q) in summer and winter, supporting what is typically observed in mid-latitude cyclones. We found that a front-relative ΔqABL of 1 g kg−1 often yielded at least a 100 m Δzi across the frontal boundary in both summer and winter. This work provides a synoptic-scale basis for zi variability and establishes a foundation for model verification to examine the impact of airmass exchange associated with advection on zi. This work will advance our understanding of ABL processes in synoptic environments and help unravel sources of front-relative zi variability.

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“…It represents the displacement of an external boundary layer that can be shallower (h adv < 0 m s −1 ) or deeper (h adv > 0 m s −1 ) than the ABL of the point of interest. Several studies discuss mass advection as an important term in complex terrains such as urban areas and mountainous regions without quantifying it (e.g, Pal et al 2021;Pal and Lee 2019;Angevine et al 2003;Pal and Haeffelin 2015;De Wekker and Kossmann 2015). Only a few studies quantify the ABL mass advection tendency.…”

Section: Introductionmentioning

confidence: 99%

Midday Boundary-Layer Collapse in the Altiplano Desert: The Combined Effect of Advection and Subsidence

Correa

Arellano

Ronda

et al. 2023

Boundary-Layer Meteorol

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Observations in the Altiplano region of the Atacama Desert show that the atmospheric boundary layer (ABL) suddenly collapses at noon. This rapid decrease occurs simultaneously to the entrance of a thermally driven, regional flow that causes a rise in wind speed and a marked temperature decrease. We identify the main drivers that cause the observed ABL collapse by using a land–atmosphere model. The free atmosphere lapse rate and regional forcings, such as advection of mass and cold air as well as subsidence, are first estimated by combining observations from a comprehensive field campaign and a regional model. Then, to disentangle the ABL collapse, we perform a suite of numerical experiments with increasing level of complexity: from only considering local land–atmosphere interactions, to systematically including the regional contributions of mass advection, cold air advection, and subsidence. Our results show that non-local processes related to the arrival of the regional flow are the main factors explaining the boundary-layer collapse. The advection of a shallower boundary layer ($$\approx -250$$ ≈ - 250 m h$$^{-1}$$ - 1 at noon) causes an immediate decrease in the ABL height (h) at midday. This occurs simultaneously with the arrival of a cold air mass, which reaches a strength of $$\approx -4$$ ≈ - 4 K h$$^{-1}$$ - 1 at 1400 LT. These two external forcings become dominant over entrainment and surface processes that warm the atmosphere and increase h. As a consequence, the ABL growth is capped during the afternoon. Finally, a wind divergence of $$\approx 8 \times 10^{-5}$$ ≈ 8 × 10 - 5 s$$^{-1}$$ - 1 contributes to the collapse by causing subsidence motions over the ABL from 1200 LT onward. Our findings show the relevance of treating large and small-scale processes as a continuum to be able to understand the ABL dynamics.

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Advected Air Mass Reservoirs in the Downwind of Mountains and Their Roles in Overrunning Boundary Layer Depths Over the Plains

Cited by 7 publications

References 42 publications

The 2019 Mississippi and Missouri River Flooding and Its Impact on Atmospheric Boundary Layer Dynamics

The 2019 Mississippi and Missouri River Flooding and Its Impact on Atmospheric Boundary Layer Dynamics

Empirical Evidence for the Frontal Modification of Atmospheric Boundary Layer Depth Variability over Land

Midday Boundary-Layer Collapse in the Altiplano Desert: The Combined Effect of Advection and Subsidence

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