Details:

Journal Title:
Journal of Geophysical Research: Oceans
Personal Author:
Thompson, Elizabeth J. ; Moum, James N. ; Fairall, Christopher W. ; Rutledge, Steven A.
Thompson, Elizabeth J. ; Moum, James N. ; Fairall, Christopher W. ; Rutledge, Steven A. Less -
NOAA Program & Office:
CIRES (Cooperative Institute for Research in Environmental Sciences) ; OAR (Oceanic and Atmospheric Research) ; ESRL (Earth System Research Laboratory)
CIRES (Cooperative Institute for Research in Environmental Sciences) ; OAR (Oceanic and Atmospheric Research) ; ESRL (Earth System Research Laboratory) Less -
Description:
Stratification of the upper few meters of the ocean limits the penetration depth of wind mixing and the vertical distribution of atmospheric fluxes. Significant density stratification at depths ≤ 5 m was observed in 38% of a 2‐month data set from the central Indian Ocean collected during the DYNAMO experiment (Dynamics of the MJO, Madden‐Julian Oscillation). Diurnal warm layers (DWLs) formed by solar heating populated 30% of the data set and rain layers (RLs) populated 16%. Combined contributions from rain and insolation formed RL‐DWLs in 9% of the data set. RLs were detected at values of U 10 up to 9.8 m s−1, while DWLs were only detected at U 10 < 7.6 m s−1 (99th percentile values), symptomatic of the greater buoyancy flux provided by moderate to high rain rate compared to insolation. From the ocean friction velocity, u *w , and surface buoyancy flux, B , we derived estimates of urn:x-wiley:21699275:media:jgrc23188:jgrc23188-math-0001, stable layer depth, and urn:x-wiley:21699275:media:jgrc23188:jgrc23188-math-0002, the maximum U 10 for which stratification should persist at urn:x-wiley:21699275:media:jgrc23188:jgrc23188-math-0003 for fixed B . These estimates predicted (1) 36 out of 44 observed stratification events (88% success rate) and (2) the wind limits of these events, which are considered to be the 99th percentile values of U10). This suggests a means to determine the presence of ocean stable layers at depths ≤ 5 m from U 10 and B . Near‐surface stratification varied throughout two Madden‐Julian Oscillation (MJO) cycles. In suppressed MJO periods, (U 10 ≤ 8 m s−1 with strong insolation), RLs and RL‐DWLs were rare while DWLs occurred daily. During disturbed and active MJO periods, (U 10 ≤ 8 m s−1 with increased rain and cloudiness), multiple RLs and RL‐DWLs formed per day and DWLs became less common. When westerly wind bursts occurred, (U 10 = 7–17 m s−1 with steady rain), RLs formed infrequently and DWLs were not detected.
Keywords:
[+]
Boundary Layer
Precipitation

Source:
Journal of Geophysical Research: Oceans, ; 124, 897–924 ;
DOI:
https://doi.org/10.1029/2018JC014130
Document Type:
Journal Article
Rights Information:
Other
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Submitted
Main Document Checksum:
[+]
urn:sha256:621ec560c402aa2faa7a44199b9eaa98bd963f3d2710804b3acbf64cd39bc120
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