Universität zu Köln

Acquistapace, C., Meroni, A. N., Labbri, G., Lange, D., Spath, F., Abbas, S. and Bellenger, H. (2022). Fast Atmospheric Response to a Cold Oceanic Mesoscale Patch in the North-western Tropical Atlantic. J. Geophys. Res.-Atmos., 127 (21). WASHINGTON: AMER GEOPHYSICAL UNION. ISSN 2169-8996

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Abstract

Low-level clouds over the tropical and sub-tropical oceans play a crucial role in the planetary radiative energy budget. However, they are challenging to model in climate simulations because they are affected by local processes that are still partially unknown. The control that mesoscale sea surface temperature (SST) structures have on the dynamics of the lower atmosphere on daily scales is emerging to be non-negligible and calls for more effort to be understood. During the EUREC(4)A field campaign, two of the research vessels (R/Vs) involved in the experiment sampled the edge of a cold mesoscale SST patch in the north-western tropical Atlantic, crossing a gradient of roughly 0.75 degrees C/100 km. The comprehensive set of instruments carried by the R/Vs allows an unprecedented characterization of the atmospheric response to the cold water forcing. The cold ocean patch weakens the vertical atmospheric mixing, reducing the boundary layer depth of roughly 200 m and the horizontal wind intensity of approximately 3 m s(-1). At the same time, the humidity content in the sub-cloud layer increases and these conditions decrease the latent heat flux (by roughly 80 W m(-2)) and reduce vertical velocity fluctuations, making it less likely that moisture exceeds the lifting condensation level. As a consequence, fewer and thinner low-level clouds form over cold water. Independent satellite measurements are found to agree with the in situ observations. The observed link between sea temperature and low-level clouds highlights its importance in the puzzle of modeling the sea-air-cloud interactions. Plain Language Summary Puffy clouds typically visible at sea strongly challenge climate models that struggle to represent their interaction with the sea surface and solar radiation. And as a consequence, these climate models cannot precisely estimate how much the Earth's temperature will increase 100 years from now and its uncertainty. We went into the western Atlantic ocean for a month in January-February 2020 to measure sea surface temperature and cloud properties and observe how these changes occur. We saw clouds grow deeper over the warm water patches, holding more water and eventually raining. Weaker winds and more humid air occur on cold patches. Satellite observations seem to record the same behavior over a larger area in the same region. We detected a clear difference in cloud properties and amounts over warm and cold patches from all sensors, recording essential evidence of a feature that is hard to predict. We hope these observations will help to properly simulate the intensity and signs of low-cloud feedback over warm and cold oceanic patches of water to improve climate models.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Acquistapace, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Meroni, A. N. UNSPECIFIED UNSPECIFIED UNSPECIFIED Labbri, G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Lange, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Spath, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Abbas, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bellenger, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-683836
DOI:	10.1029/2022JD036799
Journal or Publication Title:	J. Geophys. Res.-Atmos.
Volume:	127
Number:	21
Date:	2022
Publisher:	AMER GEOPHYSICAL UNION
Place of Publication:	WASHINGTON
ISSN:	2169-8996
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SEA-SURFACE TEMPERATURE; EASTERN EQUATORIAL PACIFIC; LOW-LEVEL WINDS; CLOUD; MODEL; VARIABILITY; EUREC(4)A; FRONTS; HEIGHT; SYSTEM Multiple languages Meteorology & Atmospheric Sciences Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/68383