Atmospheric radiative profiles during EUREC&amp;lt;sup&amp;gt;4&amp;lt;/sup&amp;gt;A

Albright, Anna Lea; Fildier, Benjamin; Pincus, Robert; Vial, Jessica; Müller, Caroline

doi:10.5194/essd-2020-269

Cited by 2 publications

(4 citation statements)

References 35 publications

(47 reference statements)

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“…The Flowers pattern in particular is associated with less stable conditions during the night, owing to a large decrease in

θ_{700}

. From these results, we hypothesize that, while more stable conditions can be more favourable to stratiform cloudiness at night, once the Flowers stratiform cloud layer are present they might produce locally less stable conditions, presumably through enhanced radiative cooling at cloud‐top (e.g., figure 6 of Albright et al ., 2021). Case‐studies of the field campaign EUREC

^{4}

A (Stevens et al ., 2021) which took place windward of Barbados in January–February 2020 could provide new opportunities to further investigate how the cloud patterns impact the local environment.…”

Section: The Role Of Environmental Factorsmentioning

confidence: 91%

On the daily cycle of mesoscale cloud organization in the winter trades

Vial¹,

Vogel²,

Schulz

2021

Quart J Royal Meteoro Soc

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How spatial organization of clouds at the mesoscale contributes to the daily cycle of shallow cumulus clouds and precipitation is here explored, for the first time, using three years of high-frequency satellite-and ground-based observations. We focus on the four prominent patterns of cloud organization -Sugar, Gravel, Flowers and Fish -which were found recently to characterize well the variability of the North Atlantic winter trades. Our analysis is based on a simple framework to disentangle the parts of the daily cycle of trade-wind cloudiness that are due to changes in (a) the occurrence frequency of patterns, and (b) cloud cover for a given pattern. Our investigation reveals that the contribution of mesoscale organization to the daily cycle in cloudiness is largely mediated by the frequency of pattern occurrence. All forms of mesoscale organization exhibit a pronounced daily cycle in their frequency of occurrence, with distinct 24-hr phasing. The patterns Fish and Sugar can be viewed as daytime patterns, with a frequency peak around noon for Fish and towards sunset for Sugar. The patterns Gravel and Flowers appear instead as night-time patterns, with a peak occurrence around midnight for Gravel and before sunrise for Flowers. The cloud cover for a given pattern, however, always maximizes at night-time (between 0000 and 0300 hr), regardless of the specific pattern. Analyses of the role of large-scale environmental conditions shows that the near-surface wind speed can explain a large part of the diurnal variability in pattern frequency and cloudiness. K E Y W O R D Sdaily cycle, mesoscale organization, observations, trade-wind cumuli INTRODUCTIONAs one of the most fundamental modes of tropical climate variability, the daily cycle has been thoroughly studied for many cloud types except, surprisingly, for shallow cumuli in the trade-wind regime. Indeed, the daily cycle of trade-wind cumuli has only been recently described in some detail by Vial et al., (2019), 40 years after it was first documented (Nitta and Esbensen, 1974;Brill and Albrecht, 1982). In typical conditions of the North Atlantic winter trades, cloudiness overall maximizes at the end of the night and is minimum in the afternoon. This dailyThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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“…The Flowers pattern in particular is associated with less stable conditions during the night, owing to a large decrease in

θ_{700}

^{4}

Section: The Role Of Environmental Factorsmentioning

confidence: 91%

On the daily cycle of mesoscale cloud organization in the winter trades

Vial¹,

Vogel²,

Schulz

2021

Quart J Royal Meteoro Soc

Self Cite

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“…Variability in u is smaller in magnitude (Fig. 3c) and appears to be largely diurnal, potentially driven by variability in shortwave radiative heating (Albright et al 2021).…”

Section: Moisture Variability Is the Primary Mode Of Subcloud-layer T...mentioning

confidence: 93%

“…The reduced skill could result from multiple reasons: the smaller magnitude of variability in u itself compared to q (see Fig. 3), the smaller magnitude of the terms in the heat budget, and the presence of an additional term of radiative heating in the heat budget, wherein this radiative heating is here only calculated as clear-sky following Albright et al (2021). At times, there may be a substantial contribution from clouds, which is not accounted for in our analysis.…”

Section: B Predictive Skill Of Mixed-layer Theorymentioning

confidence: 99%

“…( 9) are calculated from observations, except for entrainment, which is the focus of section 4c. Clear-sky, aerosol-free radiative heating profiles for EUREC 4 A dropsondes and radiosonde profiles are calculated in Albright et al (2021). Large-scale horizontal moisture advection, u • =q, and potential temperature advection, u • =u, are calculated in George et al (2021) using the regression method from Bony and Stevens (2019).…”

Section: ) Budget Equations For Subcloud-layer Moisture and Heat Bala...mentioning

confidence: 99%

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Observed Subcloud-Layer Moisture and Heat Budgets in the Trades

Albright

Bony

Stevens

et al. 2022

Journal of the Atmospheric Sciences

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The trade-wind subcloud layer is an important structural component of the atmosphere. Its thermodynamic variability has long been characterized using simple frameworks, of which mixed layer theory is the simplest kind. Past studies qualitatively support such a description, yet the adequacy of mixed layer theory as a quantitative description has not been tested. Here we use observations collected during the EUREC4A (Elucidating the role of clouds–circulation coupling in climate) field campaign to test this framework and evaluate our understanding of the trade-wind subcloud layer. We find evidence for a transition layer separating the mixed layer and subcloud layer tops. The presence of such a finitely-thick transition layer with vertical gradients complicates the application of mixed layer theory, which assumes an abrupt gradient, or ‘jump’ at the subcloud layer top. This ambiguity introduces effective parameters and motivates their estimation through a Bayesian methodology. Results from this Bayesian inversion further reflect a finite-depth entrainment zone. We find that subcloud layer moisture and heat budgets close for synoptic variability and a monthly campaign-mean, yielding a campaign-mean residual of 3.6 Wm−2 for moisture and 2.9 Wm−2 for heat. Surface wind speed variability influences the subcloud layer depth and fluxes, yet thermodynamic variability above the subcloud layer top emerges as the primary control on subcloud layer moisture and heat variability. Given that this simple theoretical framework can explain observed variability, it offers an appealing framework for evaluating larger-scale models that must parameterize the processes regulating this fundamental part of the atmosphere.

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Atmospheric radiative profiles during EUREC<sup>4</sup>A

Cited by 2 publications

References 35 publications

On the daily cycle of mesoscale cloud organization in the winter trades

On the daily cycle of mesoscale cloud organization in the winter trades

Observed Subcloud-Layer Moisture and Heat Budgets in the Trades

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