Tomita Hiroyuki

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Tomita
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Hiroyuki
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Now showing 1 - 3 of 3
  • Article
    Corrigendum to “Formation and erosion of the seasonal thermocline in the Kuroshio Extension Recirculation gyre” [Deep-Sea Res. II 85 (2013) 62–74]
    (Elsevier, 2016-08-08) Cronin, Meghan F. ; Bond, Nicholas A. ; Farrar, J. Thomas ; Ichikawa, Hiroshi ; Jayne, Steven R. ; Kawai, Yoshimi ; Konda, Masanori ; Qiu, Bo ; Rainville, Luc ; Tomita, Hiroyuki
  • Article
    Formation and erosion of the seasonal thermocline in the Kuroshio Extension Recirculation Gyre
    (Elsevier Ltd., 2012-07-21) Cronin, Meghan F. ; Bond, Nicholas A. ; Farrar, J. Thomas ; Ichikawa, Hiroshi ; Jayne, Steven R. ; Kawai, Yoshimi ; Konda, Masanori ; Qiu, Bo ; Rainville, Luc ; Tomita, Hiroyuki
    Data from the Kuroshio Extension Observatory (KEO) surface mooring are used to analyze the balance of processes affecting the upper ocean heat content and surface mixed layer temperature variations in the Recirculation Gyre (RG) south of the Kuroshio Extension (KE). Cold and dry air blowing across the KE and its warm RG during winter cause very large heat fluxes out of the ocean that result in the erosion of the seasonal thermocline in the RG. Some of this heat is replenished through horizontal heat advection, which may enable the seasonal thermocline to begin restratifying while the net surface heat flux is still acting to cool the upper ocean. Once the surface heat flux begins warming the ocean, restratification occurs rapidly due to the low thermal inertia of the shallow mixed layer depth. Enhanced diffusive mixing below the mixed layer tends to transfer some of the mixed layer heat downward, eroding and potentially modifying sequestered subtropical mode water and even the deeper waters of the main thermocline during winter. Diffusivity at the base of the mixed layer, estimated from the residual of the mixed layer temperature balance, is roughly 3×10−4 m2/s during the summer and up to two orders of magnitude larger during winter. The enhanced diffusivities appear to be due to large inertial shear generated by wind events associated with winter storms and summer tropical cyclones. The diffusivity's seasonality is likely due to seasonal variations in stratification just below the mixed layer depth, which is large during the summer when the seasonal thermocline is fully developed and low during the winter when the mixed layer extends to the top of the thermocline.
  • Article
    Air-sea fluxes with a focus on heat and momentum
    (Frontiers Media, 2019-07-31) Cronin, Meghan F. ; Gentemann, Chelle L. ; Edson, James B. ; Ueki, Iwao ; Bourassa, Mark A. ; Brown, Shannon ; Clayson, Carol A. ; Fairall, Christopher W. ; Farrar, J. Thomas ; Gille, Sarah T. ; Gulev, Sergey ; Josey, Simon A. ; Kato, Seiji ; Katsumata, Masaki ; Kent, Elizabeth ; Krug, Marjolaine ; Minnett, Peter J. ; Parfitt, Rhys ; Pinker, Rachel T. ; Stackhouse, Paul W., Jr. ; Swart, Sebastiaan ; Tomita, Hiroyuki ; Vandemark, Douglas ; Weller, Robert A. ; Yoneyama, Kunio ; Yu, Lisan ; Zhang, Dongxiao
    Turbulent and radiative exchanges of heat between the ocean and atmosphere (hereafter heat fluxes), ocean surface wind stress, and state variables used to estimate them, are Essential Ocean Variables (EOVs) and Essential Climate Variables (ECVs) influencing weather and climate. This paper describes an observational strategy for producing 3-hourly, 25-km (and an aspirational goal of hourly at 10-km) heat flux and wind stress fields over the global, ice-free ocean with breakthrough 1-day random uncertainty of 15 W m–2 and a bias of less than 5 W m–2. At present this accuracy target is met only for OceanSITES reference station moorings and research vessels (RVs) that follow best practices. To meet these targets globally, in the next decade, satellite-based observations must be optimized for boundary layer measurements of air temperature, humidity, sea surface temperature, and ocean wind stress. In order to tune and validate these satellite measurements, a complementary global in situ flux array, built around an expanded OceanSITES network of time series reference station moorings, is also needed. The array would include 500–1000 measurement platforms, including autonomous surface vehicles, moored and drifting buoys, RVs, the existing OceanSITES network of 22 flux sites, and new OceanSITES expanded in 19 key regions. This array would be globally distributed, with 1–3 measurement platforms in each nominal 10° by 10° box. These improved moisture and temperature profiles and surface data, if assimilated into Numerical Weather Prediction (NWP) models, would lead to better representation of cloud formation processes, improving state variables and surface radiative and turbulent fluxes from these models. The in situ flux array provides globally distributed measurements and metrics for satellite algorithm development, product validation, and for improving satellite-based, NWP and blended flux products. In addition, some of these flux platforms will also measure direct turbulent fluxes, which can be used to improve algorithms for computation of air-sea exchange of heat and momentum in flux products and models. With these improved air-sea fluxes, the ocean’s influence on the atmosphere will be better quantified and lead to improved long-term weather forecasts, seasonal-interannual-decadal climate predictions, and regional climate projections.