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A Positive Low Cloud–Sea Surface Temperature Feedback in the East Asian Marginal Seas during El Niño Mature Winters and Their Following Spring

Journal Article · · Journal of Climate
 [1];  [2];  [1];  [3];  [4]
  1. Chinese Academy of Sciences (CAS), Beijing (China)
  2. Met Office, Exeter (United Kingdom)
  3. Univ. of Wisconsin, Madison, WI (United States); Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
  4. Nanjing Univ. of Information Science and Technology (China)
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During the winter and subsequent spring of an El Niño year, the East Asian marginal sea (EAMS) exhibits positive sea surface temperature anomalies (SSTAs) and fewer low clouds, while the western North Pacific experiences negative SSTAs. In this study, we suggest that the positive SSTAs in EAMS are maintained by a positive low cloud–SST feedback. In neutral winters and springs, the EAMS is covered by low clouds, which have a cooling effect on surface temperatures. During an El Niño year, a western North Pacific anomalous anticyclone is established, and along its northwestern flank, there are favorable conditions for convergence of moisture and weaker surface latent heat flux over the EAMS. Once a positive SSTA has been established, a further reduction of turbulent mixing results in less low cloud and enhanced solar heating of the ocean mixed layer; this reinforces and maintains both the positive SSTA and the lack of low cloud via a positive feedback mechanism. Further, the concurrent increase of low cloud–SST feedback and anticyclone circulation strengths is evident in the coupled-model simulations from phase 6 of the Coupled Model Intercomparison Project. Furthermore, sensitivity experiments, performed with the atmospheric components of Community Earth System Model (CESM2), reveal that a positive SSTA helps to maintain the western North Pacific anomalous anticyclone. Four pacemaker-coupled experiments by CESM2, with sea surface temperature in the equatorial Pacific restored to the observational anomalies plus the model climatology and altered low cloud feedback over EAMS, suggest that the low cloud–SST feedback results in more than the maintenance of a positive SSTA over the EAMS: the positive feedback is also a previously overlooked mechanism for the maintenance of the western North Pacific anomalous anticyclone.

Research Organization:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
Sponsoring Organization:
USDOE; National Key Research and Development Program of China; National Natural Science Foundation of China (NSFC)
Grant/Contract Number:
AC05-76RL01830
OSTI ID:
2328573
Report Number(s):
PNNL-SA--184765
Journal Information:
Journal of Climate, Journal Name: Journal of Climate Journal Issue: 24 Vol. 35; ISSN 0894-8755
Publisher:
American Meteorological SocietyCopyright Statement
Country of Publication:
United States
Language:
English

Figures / Tables (16)

FIG. 1(p. 3)figure FIG. 1
TABLE 1(p. 4)table TABLE 1
TABLE 2(p. 5)table TABLE 2
TABLE 3(p. 6)table TABLE 3
FIG. 2(p. 7)figure FIG. 2
FIG. 3(p. 8)figure FIG. 3
FIG. 4(p. 9)figure FIG. 4
FIG. 5(p. 10)figure FIG. 5
FIG. 6(p. 11)figure FIG. 6
FIG. 7(p. 11)figure FIG. 7
FIG. 8(p. 12)figure FIG. 8
FIG. 9(p. 13)figure FIG. 9
FIG. 10(p. 14)figure FIG. 10
FIG. 11(p. 15)figure FIG. 11
FIG. A1(p. 17)figure FIG. A1
FIG. C1(p. 17)figure FIG. C1

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Related Subjects

54 ENVIRONMENTAL SCIENCES
Asia
Atmosphere-ocean interaction
Climate models
Cloud cover
Clouds
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