Format:
Online-Ressource
ISSN:
2698-4016
Content:
Abstract 4 A (Elucidate the Couplings Between Clouds, Convection and Circulation) from 16 January to 20 February 2020, using a combination of Eulerian and Lagrangian diagnostics. Based on observations and ERA5 reanalyses, we identify the relevant processes and characterize the formation pathways of two moist anomalies above the Barbados Cloud Observatory (BCO), one in the lower troposphere (∼ hPa) and one in the middle troposphere (∼ hPa). These moist anomalies are associated with strongly negative CRE values and with contrasting long-range transport processes from the extratropics and the tropics, respectively. The first case study about the low-level moist anomaly is characterized by an unusually thick cloud layer, high precipitation totals, and a strongly negative CRE. The formation of the low-level moist anomaly is connected to an extratropical dry intrusion (EDI) that interacts with a trailing cold front. A quasi-climatological (2010-2020) analysis reveals that EDIs lead to different conditions at the BCO depending on how they interact with the associated trailing cold front. Based on this climatology, we discuss the relevance of the strong large-scale forcing by EDIs for the low-cloud patterns near the BCO and the related CRE. The second case study about the mid-tropospheric moist anomaly is associated with an extended and persistent mixed-phase shelf cloud and the lowest daily CRE value observed during the campaign. The formation of the mid-level moist anomaly is linked to “tropical mid-level detrainment” (TMD), which refers to detrainment from tropical deep convection near the melting layer. The quasi-climatological analysis shows that TMDs consistently lead to mid-tropospheric moist anomalies over the BCO and that the detrainment height controls the magnitude of the anomaly. However, no systematic relationship was found between the amplitude of this mid-tropospheric moist anomaly and the CRE at the BCO. This is most likely due to the modulation of the CRE by above and below lying clouds and the fact that we used daily mean CREs, thereby ignoring the impact of the timing of the synoptic anomaly with respect to the daily cycle. Overall, this study reveals the important impact of the long-range moisture transport, driven by dynamical processes either in the extratropics or the tropics, on the variability of the vertical structure of moisture and clouds, and on the resulting CRE in the North Atlantic winter trades.
In:
volume:3
In:
number:1
In:
year:2022
In:
pages:59-88
In:
extent:30
In:
Weather and climate dynamics, Göttingen : Copernicus Publications, [2020]-, 3, Heft 1 (2022), 59-88 (gesamt 30), 2698-4016
Language:
English
DOI:
10.5194/wcd-3-59-2022
URN:
urn:nbn:de:101:1-2022012004150496462551
URL:
https://doi.org/10.5194/wcd-3-59-2022
URL:
https://nbn-resolving.org/urn:nbn:de:101:1-2022012004150496462551
URL:
https://d-nb.info/1249925592/34
URL:
https://wcd.copernicus.org/articles/3/59/2022/wcd-3-59-2022.pdf
URL:
https://wcd.copernicus.org/articles/3/59/2022/
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