Impact of improved Sea Surface Temperature representation on the forecast of small Mediterranean catchments hydrological response to heavy precipitation

Abstract. Operational meteo-hydrological forecasting chains are affected by many sources of uncertainty. In coastal areas characterized by complex topography, with several medium-to-small size catchments, quantitative precipitation forecast becomes even more challenging due to the interaction of intense air-sea exchanges with coastal orography. For such areas, quite common in the Mediterranean basin, improved representation of Sea Surface Temperature (SST) space-time patterns can be particularly important. The paper focuses on the relative impact of different accuracy levels of SST representation on regional operational forecasting chains (up to river discharge estimates) over coastal Mediterranean catchments, with respect to other two fundamental options while setting up the system, i.e., the choice of the forcing GCM and the possible use of a three-dimensional variational assimilation (3DVAR) scheme. Two different kinds of severe hydro-meteorological events affecting the Calabria Region (Southern Italy) on 2015 are analysed using the atmosphere-hydrology modelling system WRF-Hydro in its uncoupled version. Both the events are modelled using the 0.25° resolution Global Forecasting System (GFS) and the ECMWF's 16 km resolution Integrated Forecasting System (IFS) initial and lateral atmospheric boundary conditions. For the IFS-driven forecasts, also the effects of the 3DVAR scheme are analysed. Finally, native initial and lower boundary SST data are replaced with data from the Medspiration Project by IFREMER/CERSAT, having a 24 hour time resolution and 2.2 km spatial resolution. Precipitation estimates are compared with both ground-based and radar data, as well as discharge estimates with stream gauging stations data. Overall, the experiments highlight that the added value of improved SST representation can be hidden by other more relevant sources of uncertainty, especially the choice of the General Circulation Model providing boundary conditions. Nevertheless, high-resolution SST fields show in most cases a not negligible impact on the simulation of the atmospheric boundary layer processes, modifying flow dynamics and/or the amount of precipitated water, therefore emphasizing that uncertainty in SST representation should be duly taken into account in coastal areas operational forecasting.

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Impact of high-resolution sea surface temperature representation on the forecast of small Mediterranean catchments' hydrological responses to heavy precipitation

Hydrology and Earth System Sciences ◽

10.5194/hess-24-269-2020 ◽

2020 ◽

Vol 24 (1) ◽

pp. 269-291 ◽

Cited By ~ 5

Author(s):

Alfonso Senatore ◽

Luca Furnari ◽

Giuseppe Mendicino

Keyword(s):

High Resolution ◽

Boundary Conditions ◽

Surface Temperature ◽

Sea Surface Temperature ◽

General Circulation ◽

Circulation Model ◽

Sea Surface ◽

Sources Of Uncertainty ◽

Operational Forecasting ◽

Forecasting System

Abstract. Operational meteo-hydrological forecasting chains are affected by many sources of uncertainty. In coastal areas characterized by complex topography, with several medium-to-small size catchments, quantitative precipitation forecast becomes even more challenging due to the interaction of intense air–sea exchanges with coastal orography. For such areas, which are quite common in the Mediterranean Basin, improved representation of sea surface temperature (SST) space–time patterns can be particularly important. The paper focuses on the relative impact of different resolutions of SST representation on regional operational forecasting chains (up to river discharge estimates) over coastal Mediterranean catchments, with respect to two other fundamental options while setting up the system, i.e. the choice of the forcing general circulation model (GCM) and the possible use of a three-dimensional variational assimilation (3D-Var) scheme. Two different kinds of severe hydro-meteorological events that affected the Calabria region (southern Italy) in 2015 are analysed using the WRF-Hydro atmosphere–hydrology modelling system in its uncoupled version. Both of the events are modelled using the 0.25∘ resolution global forecasting system (GFS) and the 16 km resolution integrated forecasting system (IFS) initial and lateral atmospheric boundary conditions, which are from the European Centre for Medium-Range Weather Forecasts (ECMWF), applying the WRF mesoscale model for the dynamical downscaling. For the IFS-driven forecasts, the effects of the 3D-Var scheme are also analysed. Finally, native initial and lower boundary SST data are replaced with data from the Medspiration project by Institut Français de Recherche pour L'Exploitation de la Mer (IFREMER)/Centre European Remote Sensing d'Archivage et de Traitement (CERSAT), which have a 24 h time resolution and a 2.2 km spatial resolution. Precipitation estimates are compared with both ground-based and radar data, as well as discharge estimates with stream gauging stations' data. Overall, the experiments highlight that the added value of high-resolution SST representation can be hidden by other more relevant sources of uncertainty, especially the choice of the general circulation model providing the boundary conditions. Nevertheless, in most cases, high-resolution SST fields show a non-negligible impact on the simulation of the atmospheric boundary layer processes, modifying flow dynamics and/or the amount of precipitated water; thus, this emphasizes the fact that uncertainty in SST representation should be duly taken into account in operational forecasting in coastal areas.

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A spatiotemporal reconstruction of sea-surface temperatures in the North Atlantic during Dansgaard–Oeschger events 5–8

Climate of the Past ◽

10.5194/cp-14-901-2018 ◽

2018 ◽

Vol 14 (6) ◽

pp. 901-922 ◽

Cited By ~ 6

Author(s):

Mari F. Jensen ◽

Aleksi Nummelin ◽

Søren B. Nielsen ◽

Henrik Sadatzki ◽

Evangeline Sessford ◽

...

Keyword(s):

Surface Temperature ◽

Sea Surface Temperature ◽

North Atlantic ◽

General Circulation ◽

Sea Surface ◽

Reconstruction Method ◽

Sea Surface Temperatures ◽

Proxy Data ◽

Surface Temperatures ◽

Temperature Reconstructions

Abstract. Here, we establish a spatiotemporal evolution of the sea-surface temperatures in the North Atlantic over Dansgaard–Oeschger (DO) events 5–8 (approximately 30–40 kyr) using the proxy surrogate reconstruction method. Proxy data suggest a large variability in North Atlantic sea-surface temperatures during the DO events of the last glacial period. However, proxy data availability is limited and cannot provide a full spatial picture of the oceanic changes. Therefore, we combine fully coupled, general circulation model simulations with planktic foraminifera based sea-surface temperature reconstructions to obtain a broader spatial picture of the ocean state during DO events 5–8. The resulting spatial sea-surface temperature patterns agree over a number of different general circulation models and simulations. We find that sea-surface temperature variability over the DO events is characterized by colder conditions in the subpolar North Atlantic during stadials than during interstadials, and the variability is linked to changes in the Atlantic Meridional Overturning circulation and in the sea-ice cover. Forced simulations are needed to capture the strength of the temperature variability and to reconstruct the variability in other climatic records not directly linked to the sea-surface temperature reconstructions. This is the first time the proxy surrogate reconstruction method has been applied to oceanic variability during MIS3. Our results remain robust, even when age uncertainties of proxy data, the number of available temperature reconstructions, and different climate models are considered. However, we also highlight shortcomings of the methodology that should be addressed in future implementations.

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The U.K. Meteorological Office general circulation model and some results from experiments with sea-surface temperature anomalies

Deep Sea Research ◽

10.1016/0146-6291(77)90070-4 ◽

1977 ◽

Vol 24 (4) ◽

pp. 194

Keyword(s):

Surface Temperature ◽

Sea Surface Temperature ◽

General Circulation Model ◽

General Circulation ◽

Circulation Model ◽

Sea Surface ◽

Temperature Anomalies ◽

Sea Surface Temperature Anomalies

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On the relative influences of different ocean basin sea surface temperature anomalies on southern African rainfall in 20th and 21st century general circulation model simulations

International Journal of Climatology ◽

10.1002/joc.5691 ◽

2018 ◽

Vol 38 (13) ◽

pp. 5003-5009

Author(s):

Megan Lickley ◽

Susan Solomon

Keyword(s):

Surface Temperature ◽

Sea Surface Temperature ◽

21St Century ◽

General Circulation ◽

Circulation Model ◽

Ocean Basin ◽

Sea Surface ◽

Model Simulations ◽

African Rainfall ◽

Sea Surface Temperature Anomalies

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Assessing bias corrections of oceanic surface conditions for atmospheric models

Geoscientific Model Development ◽

10.5194/gmd-12-321-2019 ◽

2019 ◽

Vol 12 (1) ◽

pp. 321-342 ◽

Cited By ~ 2

Author(s):

Julien Beaumet ◽

Gerhard Krinner ◽

Michel Déqué ◽

Rein Haarsma ◽

Laurent Li

Keyword(s):

Sea Ice ◽

Surface Temperature ◽

Sea Surface Temperature ◽

General Circulation ◽

General Circulation Models ◽

Substantial Improvement ◽

Sea Surface ◽

Sea Ice Concentration ◽

Ice Concentration ◽

Analogue Method

Abstract. Future sea surface temperature and sea-ice concentration from coupled ocean–atmosphere general circulation models such as those from the CMIP5 experiment are often used as boundary forcings for the downscaling of future climate experiments. Yet, these models show some considerable biases when compared to the observations over present climate. In this paper, existing methods such as an absolute anomaly method and a quantile–quantile method for sea surface temperature (SST) as well as a look-up table and a relative anomaly method for sea-ice concentration (SIC) are presented. For SIC, we also propose a new analogue method. Each method is objectively evaluated with a perfect model test using CMIP5 model experiments and some real-case applications using observations. We find that with respect to other previously existing methods, the analogue method is a substantial improvement for the bias correction of future SIC. Consistency between the constructed SST and SIC fields is an important constraint to consider, as is consistency between the prescribed sea-ice concentration and thickness; we show that the latter can be ensured by using a simple parameterisation of sea-ice thickness as a function of instantaneous and annual minimum SIC.

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