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Climatological diurnal variability in sea surface temperature characterized from drifting buoy data

Climatological diurnal variability in sea surface temperature characterized from drifting buoy data
Climatological diurnal variability in sea surface temperature characterized from drifting buoy data
Drifting buoy sea-surface temperature (SST) records have been used to characterize the diurnal variability of ocean temperature at a depth of order 20 cm. We use measurements covering the period 1986–2012 from the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) version 2.5, which is a collection of marine surface observations that includes individual SST records from drifting buoys. Appropriately transformed, this dataset is well suited for estimation of the diurnal cycle, since many drifting buoys have high temporal coverage (many reports per day), and are globally distributed. For each drifter for each day, we compute the local-time daily SST variation relative to the local-time daily mean SST. Climatological estimates of subdaily SST variability are found by averaging across various strata of the data: in 10° latitudinal bands as well as globally; and stratified with respect to season, wind speed and cloud cover. A parameterization of the diurnal variability is fitted as a function of the variables used to stratify the data, and the coefficients for this fit are also provided with the data. Results are consistent with expectations based on the previous work: the diurnal temperature cycle peaks in early afternoon (circa 2 pm local time); there is an increase in amplitude and a decrease in seasonality towards the equator. Generally, the ocean at this depth cools on windy days and warms on calm days, so that a component of subdaily variability is the SST tendency on slower timescales. By not ‘closing’ the diurnal cycle when stratified by environmental conditions, this dataset differs from previously published diurnal-cycle parameterizations. This thorough characterization of the SST diurnal cycle will assist in interpreting SST observations made at different local times of day for climatological purposes, and in testing and constraining models of the diurnal-cycle and air-sea interaction at high temporal resolution.
SST, diurnal variations, drifting
2049-6060
20-28
Morak-Bozzo, S.
16f66a3b-0ffc-4dbc-b643-23cf8bbf773b
Merchant, C.J.
834a7bd1-42dd-47e9-b21b-b4dd639646c6
Kent, E.C.
ea23f6f0-ccf6-4702-a5c9-184e9c5d4427
Berry, D.I.
55ffc590-f459-49c8-aecf-842d65aeb0fb
Carella, G.
3e1debcd-101d-46b3-99dc-eef476e0b262
Morak-Bozzo, S.
16f66a3b-0ffc-4dbc-b643-23cf8bbf773b
Merchant, C.J.
834a7bd1-42dd-47e9-b21b-b4dd639646c6
Kent, E.C.
ea23f6f0-ccf6-4702-a5c9-184e9c5d4427
Berry, D.I.
55ffc590-f459-49c8-aecf-842d65aeb0fb
Carella, G.
3e1debcd-101d-46b3-99dc-eef476e0b262

Morak-Bozzo, S., Merchant, C.J., Kent, E.C., Berry, D.I. and Carella, G. (2016) Climatological diurnal variability in sea surface temperature characterized from drifting buoy data. Geoscience Data Journal, 3 (1), 20-28. (doi:10.1002/gdj3.35).

Record type: Article

Abstract

Drifting buoy sea-surface temperature (SST) records have been used to characterize the diurnal variability of ocean temperature at a depth of order 20 cm. We use measurements covering the period 1986–2012 from the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) version 2.5, which is a collection of marine surface observations that includes individual SST records from drifting buoys. Appropriately transformed, this dataset is well suited for estimation of the diurnal cycle, since many drifting buoys have high temporal coverage (many reports per day), and are globally distributed. For each drifter for each day, we compute the local-time daily SST variation relative to the local-time daily mean SST. Climatological estimates of subdaily SST variability are found by averaging across various strata of the data: in 10° latitudinal bands as well as globally; and stratified with respect to season, wind speed and cloud cover. A parameterization of the diurnal variability is fitted as a function of the variables used to stratify the data, and the coefficients for this fit are also provided with the data. Results are consistent with expectations based on the previous work: the diurnal temperature cycle peaks in early afternoon (circa 2 pm local time); there is an increase in amplitude and a decrease in seasonality towards the equator. Generally, the ocean at this depth cools on windy days and warms on calm days, so that a component of subdaily variability is the SST tendency on slower timescales. By not ‘closing’ the diurnal cycle when stratified by environmental conditions, this dataset differs from previously published diurnal-cycle parameterizations. This thorough characterization of the SST diurnal cycle will assist in interpreting SST observations made at different local times of day for climatological purposes, and in testing and constraining models of the diurnal-cycle and air-sea interaction at high temporal resolution.

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Accepted/In Press date: 3 May 2016
e-pub ahead of print date: 25 June 2016
Published date: 25 June 2016
Keywords: SST, diurnal variations, drifting
Organisations: Marine Physics and Ocean Climate

Identifiers

Local EPrints ID: 397476
URI: http://eprints.soton.ac.uk/id/eprint/397476
ISSN: 2049-6060
PURE UUID: 30598587-8c26-485c-a8e3-a607a14e59b4

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Date deposited: 28 Jun 2016 12:44
Last modified: 15 Mar 2024 01:15

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Contributors

Author: S. Morak-Bozzo
Author: C.J. Merchant
Author: E.C. Kent
Author: D.I. Berry
Author: G. Carella

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