Abstract
A surface diurnal warm layer is diagnosed from Seaglider observations, and develops on half the days in the CINDY/DYNAMO Indian Ocean experiment. The diurnal warm layer occurs on days of high solar radiation flux (>80 W m-2) and low wind speed (<6 m s-1), and preferentially in the inactive stage of the Madden-Julian Oscillation. Its diurnal harmonic has an exponential vertical structure with a depth scale of 4-5 m (dependent on chlorophyll concentration), consistent with forcing by absorption of solar radiation. The effective sea surface temperature (SST) anomaly due to the diurnal warm layer often reaches 0.8°C in the afternoon, with a daily mean of 0.2°C, rectifying the diurnal cycle onto longer time scales. This SST anomaly drives an anomalous flux of 4 W m-2 that cools the ocean. Alternatively, in a climate model where this process is unresolved, this represents an erroneous flux that warms the ocean. A simple model predicts a diurnal warm layer to occur on 30-50% of days across the tropical warm pool. On the remaining days, with low solar radiation and high wind speeds, a residual diurnal cycle is observed by the Seaglider, with a diurnal harmonic of temperature that decreases linearly with depth. As wind speed increases, this already weak temperature gradient decreases further, tending towards isothermal conditions.
Original language | English |
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Pages (from-to) | 9101–9122 |
Number of pages | 22 |
Journal | Journal of Climate |
Volume | 27 |
Issue number | 24 |
DOIs | |
Publication status | Published - Dec 2014 |
Profiles
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Karen Heywood
- School of Environmental Sciences - Professor of Physical Oceanography
- Centre for Ocean and Atmospheric Sciences - Member
- ClimateUEA - Member
Person: Research Group Member, Academic, Teaching & Research
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Adrian Matthews
- School of Environmental Sciences - Professor of Meteorology
- Centre for Ocean and Atmospheric Sciences - Member
- Fluids & Structures - Member
- Numerical Simulation, Statistics & Data Science - Member
- ClimateUEA - Member
Person: Research Group Member, Academic, Teaching & Research