The Role of Melting Snow in the Ocean Surface Heat Budget

<p>Der Datensatz des <em>Surface Heat Budget of the Arctic Ocean (SHEBA) </em>Experimentes 1997/98 wird h&#228;ufig f&#252;r die Berechnung von universellen Funktionen f&#252;r stabile Schichtung herangezogen. F&#252;r eine nicht-iterative Modellierung (Louis-Ansatz) k&#246;nnen diese Funktionen neu berechnet werden. Allerdings haben diese Funktionen viele empirische Faktoren, die sich aus der Anpassung an den urspr&#252;nglichen Datensatz ergeben. Ein interessantes Ergebnis bei der Analyse der Daten des SHEBA-Experimentes ist, dass die Daten f&#252;r die oberen Messpunkte des Experiments einer lokalen Skalierung mit den klassischen universellen Funktionen folgen, w&#228;hrend die Daten der unteren Messpunkte eine gro&#223;e Streuung aufweisen. Somit k&#246;nnten f&#252;r den oberen Teil des Profils ein allgemein &#252;blicher Louis-Ansatz verwendet werden. Es ist davon auszugehen, dass unter besonderen Bedingungen der untere Teil des Profils vom oberen Teil entkoppelt ist, wie es bei anderen Experimenten bereits gezeigt werden konnte. Ein einfacher Test f&#252;r die Entkopplung durch Vergleich der experimentellen Daten mit einem hydrodynamischen Modellansatzes wird in der Pr&#228;sentation gezeigt. Es wird daher empfohlen, den SHEBA Datensatz auf Entkopplung zu testen und eine wahrscheinlich viel einfachere universelle Funktion zu erstellen. Allerdings ist der Umgang mit entkoppelten Situationen noch im Bereich der Forschung. Es ist allerdings f&#252;r die meisten F&#228;lle zu erwarten, dass bei Ber&#252;cksichtigung der Entkopplung kleinere Fl&#252;sse bestimmt w&#252;rden.</p>

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Surface Heat Budget over the North Sea in Climate Change Simulations

Atmosphere ◽

10.3390/atmos10050272 ◽

2019 ◽

Vol 10 (5) ◽

pp. 272 ◽

Cited By ~ 7

Author(s):

Christian Dieterich ◽

Shiyu Wang ◽

Semjon Schimanke ◽

Matthias Gröger ◽

Birgit Klein ◽

...

Keyword(s):

Climate Change ◽

Heat Flux ◽

North Sea ◽

Heat Budget ◽

Coupled Model ◽

Surface Heat ◽

The North ◽

The North Sea ◽

Rcp 8.5 ◽

Surface Heat Budget

An ensemble of regional climate change scenarios for the North Sea is validated and analyzed. Five Coupled Model Intercomparison Project Phase 5 (CMIP5) General Circulation Models (GCMs) using three different Representative Concentration Pathways (RCPs) have been downscaled with the coupled atmosphere–ice–ocean model RCA4-NEMO. Validation of sea surface temperature (SST) against different datasets suggests that the model results are well within the spread of observational datasets. The ensemble mean SST with a bias of less than 1 ∘ C is the solution that fits the observations best and underlines the importance of ensemble modeling. The exchange of momentum, heat, and freshwater between atmosphere and ocean in the regional, coupled model compares well with available datasets. The climatological seasonal cycles of these fluxes are within the 95% confidence limits of the datasets. Towards the end of the 21st century the projected North Sea SST increases by 1.5 ∘ C (RCP 2.6), 2 ∘ C (RCP 4.5), and 4 ∘ C (RCP 8.5), respectively. Under this change the North Sea develops a specific pattern of the climate change signal for the air–sea temperature difference and latent heat flux in the RCP 4.5 and 8.5 scenarios. In the RCP 8.5 scenario the amplitude of the spatial heat flux anomaly increases to 5 W/m 2 at the end of the century. Different hypotheses are discussed that could contribute to the spatially non-uniform change in air–sea interaction. The most likely cause for an increased latent heat loss in the central western North Sea is a drier atmosphere towards the end of the century. Drier air in the lee of the British Isles affects the balance of the surface heat budget of the North Sea. This effect is an example of how regional characteristics modulate global climate change. For climate change projections on regional scales it is important to resolve processes and feedbacks at regional scales.

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Evaluating the impact of atmospheric forcing and air–sea coupling on near-coastal regional ocean prediction

Ocean Science ◽

10.5194/os-15-761-2019 ◽

2019 ◽

Vol 15 (3) ◽

pp. 761-778 ◽

Cited By ~ 3

Author(s):

Huw W. Lewis ◽

John Siddorn ◽

Juan Manuel Castillo Sanchez ◽

Jon Petch ◽

John M. Edwards ◽

...

Keyword(s):

Heat Budget ◽

Global Scale ◽

Ocean Model ◽

Surface Heat ◽

Wind Forcing ◽

Sea Surface ◽

Atmospheric Forcing ◽

Convective Scale ◽

The Impact ◽

Surface Heat Budget

Abstract. Atmospheric forcing applied as ocean model boundary conditions can have a critical impact on the quality of ocean forecasts. This paper assesses the sensitivity of an eddy-resolving (1.5 km resolution) regional ocean model of the north-west European Shelf (NWS) to the choice of atmospheric forcing and atmosphere–ocean coupling. The analysis is focused on a month-long simulation experiment for July 2014 and evaluation of simulated sea surface temperature (SST) in a shallow near-coastal region to the south-west of the UK (Celtic Sea and western English Channel). Observations of the ocean and atmosphere are used to evaluate model results, with a particular focus on the L4 ocean buoy from the Western Channel Observatory as a rare example of co-located data above and below the sea surface. The impacts of differences in the atmospheric forcing are illustrated by comparing results from an ocean model run in forcing mode using operational global-scale numerical weather prediction (NWP) data with an ocean model run forced by a convective-scale regional atmosphere model. The value of dynamically representing feedbacks between the atmosphere and ocean state is assessed via the use of these model components within a fully coupled ocean–wave–atmosphere system. Simulated SSTs show considerable sensitivity to atmospheric forcing and to the impact of model coupling in near-coastal areas. A warm ocean bias relative to in situ observations in the simulation forced by global-scale NWP (0.7 K in the model domain) is shown to be reduced (to 0.4 K) via the use of the 1.5 km resolution regional atmospheric forcing. When simulated in coupled mode, this bias is further reduced (by 0.2 K). Results demonstrate much greater variability of both the surface heat budget terms and the near-surface winds in the convective-scale atmosphere model data, as might be expected. Assessment of the surface heat budget and wind forcing over the ocean is challenging due to a scarcity of observations. However, it can be demonstrated that the wind speed over the ocean simulated by the convective-scale atmosphere did not agree as well with the limited number of observations as the global-scale NWP data did. Further partially coupled experiments are discussed to better understand why the degraded wind forcing does not detrimentally impact on SST results.

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