An extensive data set is used to examine the dynamics of diurnal warming in the upper ocean. The data set comprises more than 4700 days of measurements at five sites in the tropics and subtropics, obtained from surface moorings equipped to make comprehensive meteorological, incoming solar and infrared radiation, and high-resolution subsurface temperature (and, in some cases, velocity) measurements. The observations, which include surface warmings of up to 3.4°C, are compared with a selection of existing models of the diurnal warm layer (DWL). A simple one-layer physical model is shown to give a reasonable estimate of both the magnitude of diurnal surface warming (model-observation correlation 0.88) and the structure and temporal evolution of the DWL. Novel observations of velocity shear obtained during 346 days at one site, incorporating high-resolution (1 m) upper ocean (5-15 m) acoustic Doppler current profile measurements, are also shown to be in reasonable agreement with estimates from the physical model (daily maximum shear model-observation correlation 0.77). Physics-based improvements to the one-layer model (incorporation of rotation and freshwater terms) are discussed, though they do not provide significant improvements against the observations reported here. The simplicity and limitations of the physical model are used to discuss DWL dynamics. The physical model is shown to give better model performance under the range of forcing conditions experienced across the five sites than the more empirical models. ©2013. American Geophysical Union. All Rights Reserved.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): USA00001, USA00002, KSA00011
Acknowledgements: We thank the members of the WHOI Upper Ocean Processes Group and the ships crews who deployed the surface moorings and recovered the data described in this paper. J.P. was supported for part of this work by a graduate exchange studentship from the Graduate School of the National Oceanography Centre, Southampton. J.T.F. was supported by NSF OCE Award 0745508, the Charles D. Hollister Fund for Assistant Scientist Support, and the John E. and Anne W. Sawyer Endowed Fund in Special Support of Scientific Staff. R.A.W. was supported by the Office of Naval Research for the deployment of the Arabian Sea surface mooring, and by the NOAA Climate Program and Climate Observation Division for the deployment of the PACS and Stratus surface moorings. J.T.F. was supported under a cooperative program between WHOI and King Abdullah University of Science and Technology (KAUST; Awards USA00001, USA00002, and KSA00011) of the Kingdom of Saudi Arabia for the deployment of the KAUST surface moorings.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.