When and where horizontal advection is critical to alter atmospheric boundary layer dynamics over land: The need for a conceptual framework

Pal, Sandip; Clark, Nicholas E.; Lee, Temple R.; Conder, Mark R.; Buban, Michael

doi:10.1016/j.atmosres.2021.105825

Cited by 6 publications

(4 citation statements)

References 67 publications

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“…However, a comprehensive detail on the impact of cold front on the day of frontal passage remained inconclusive here because it was not possible to obtain cases when the time of the frontal passage and the radiosonde launches (i.e., 0000 UTC) were identical. Nevertheless, this work is a starting point for investigating the impact of mid-latitude cyclones on z i variability over land and could be extended in future via using both ground-based and airborne lidar observations in a frontal environment (Pal et al 2021).…”

Section: Dependence Of Boundary-layer Depths On Frontal Strengthsmentioning

confidence: 99%

“…Thus, understanding how z i changes under the impact of advection is important because neglecting these changes can result in forecasting errors in z i tendencies (i.e., z i growth rate). In synoptically active environments, these errors in ABL parametrizations increase since an interaction of two different air masses leads to significant inhomogeneities in both the horizontal and vertical ABL structures (Pal et al 2021). When spatial inhomogeneity in the ABL persists during the afternoon hours, model simulations using several ABL parametrizations (e.g., mixed-layer model, eddy diffusivity or K-closure) yield different values of z i compared to observations (Lac et al 2013;Anurose and Subrahamanyam 2015).…”

Section: Introductionmentioning

confidence: 99%

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Exploring Atmospheric Boundary Layer Depth Variability in Frontal Environments Over an Arid Region

Anand

Pal

2023

Boundary-Layer Meteorol

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Details about atmospheric boundary layer (ABL) dynamics under advection over arid regions remain unexplored. Most numerical weather prediction (NWP) models strictly rely on ABL parametrization schemes under steady-state assumptions while observation-based research also considers horizontally homogeneous atmospheric conditions for estimating ABL depth (zi) growth rates. However, how different frontal systems modify ABL thermodynamic features, including zi, remains sparse in the literature. This work investigates how synoptic events impact daytime zi variability in different seasons and provides new insights on front-relative zi variability over two sites located in an arid region. Radiosonde-derived thermodynamic profiles obtained during more than 40 synoptic events in 2020 from two sites (Amarillo and Midland, Texas) have been used. Individual soundings are divided into a three-day period: prefrontal, frontal, and postfrontal. The ABL regimes and associated soundings are further classified into four categories: (1) Type-I with elevated mixed layer (EML) only, (2) Type-II with dryline only, (3) Type-III with both EML and dryline, and (4) Type-IV without dryline or EML. Results suggest that zi decreases substantially during frontal passages and is shallower in the cold sector than the warm sector. We also find that the zi variability in the postfrontal airmass is more uniform throughout the year compared to the zi in the prefrontal airmass indicating complexities associated with airmass advection. Regression analyses comparing frontal strength and observed Δzi (i.e., frontal contrasts in zi estimated via zi in warm sector minus zi in cold sector) do not yield any correlations, which suggests that advection from frontal passages has considerable influence in governing zi variability unlike in the conditions when zi is mainly dependent on surface forcings. By explaining how airmass exchange associated with frontal environments impacts overall ABL dynamics, new parametrizations for ABL modelling can be developed with an emphasis on zi advection.

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Section: Dependence Of Boundary-layer Depths On Frontal Strengthsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Exploring Atmospheric Boundary Layer Depth Variability in Frontal Environments Over an Arid Region

Anand

Pal

2023

Boundary-Layer Meteorol

Self Cite

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“…Bhowmick and Parker, 2018). We also neglect the impact of horizontal circulation on ABL growth and convection, which may be an important factor for many urban areas around the world (Pal et al, 2021). In these regards, we present additional analyses in the discussion section and the SI to account for lateral advection of moisture and heat, and assess their impact on ABL-LCL dynamics.…”

Section: Model Developmentmentioning

confidence: 99%

An analytical approximation of urban heat and dry islands and their impact on convection triggering

et al. 2022

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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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When and where horizontal advection is critical to alter atmospheric boundary layer dynamics over land: The need for a conceptual framework

Cited by 6 publications

References 67 publications

Exploring Atmospheric Boundary Layer Depth Variability in Frontal Environments Over an Arid Region

Exploring Atmospheric Boundary Layer Depth Variability in Frontal Environments Over an Arid Region

An analytical approximation of urban heat and dry islands and their impact on convection triggering

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

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