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Effects of the diurnal cycle in solar radiation on the tropical Indian Ocean mixed layer variability during wintertime Madden-Julian Oscillations

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Title Effects of the diurnal cycle in solar radiation on the tropical Indian Ocean mixed layer variability during wintertime Madden-Julian Oscillations
Names Li, Yuanlong (creator)
Han, Weiqing (creator)
Shinoda, Toshiaki (creator)
Wang, Chunzai (creator)
Lien, Ren-Chieh (creator)
Moum, James N. (creator)
Wang, Jih-Wang (creator)
Date Issued 2013-10-03 (iso8601)
Note To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)2169-9291.
Abstract The effects of solar radiation diurnal cycle on intraseasonal mixed layer variability in
the tropical Indian Ocean during boreal wintertime Madden-Julian Oscillation (MJO) events
are examined using the HYbrid Coordinate Ocean Model. Two parallel experiments, the
main run and the experimental run, are performed for the period of 2005–2011 with daily
atmospheric forcing except that an idealized hourly shortwave radiation diurnal cycle is
included in the main run. The results show that the diurnal cycle of solar radiation generally
warms the Indian Ocean sea surface temperature (SST) north of 10 °S, particularly during
the calm phase of the MJO when sea surface wind is weak, mixed layer is thin, and the SST
diurnal cycle amplitude (dSST) is large. The diurnal cycle enhances the MJO-forced
intraseasonal SST variability by about 20% in key regions like the Seychelles-Chagos
Thermocline Ridge (SCTR; 55° –70° E, 12° –4 °S) and the central equatorial Indian Ocean
(CEIO; 65° –95° E, 3° S–3° N) primarily through nonlinear rectification. The model also well
reproduced the upper-ocean variations monitored by the CINDY/DYNAMO field campaign
between September-November 2011. During this period, dSST reaches 0.7° C in the CEIO
region, and intraseasonal SST variability is significantly amplified. In the SCTR region
where mean easterly winds are strong during this period, diurnal SST variation and its
impact on intraseasonal ocean variability are much weaker. In both regions, the diurnal
cycle also has a large impact on the upward surface turbulent heat flux Q[Subscript T] and induces
diurnal variation of Q[subscript T] with a peak-to-peak difference of O(10 W m⁻ ²).
Genre Article
Topic Diurnal cycle
Identifier Li, Y., Han, W., Shinoda, T., Wang, C., Lien, R. C., Moum, J. N., & Wang, J. W. (2013). Effects of the diurnal cycle in solar radiation on the tropical Indian Ocean mixed layer variability during wintertime Madden‐Julian Oscillations. Journal of Geophysical Research: Oceans, 118(10), 4945-4964. doi:10.1002/jgrc.20395

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