scholarly journals Integrating multiple satellite observations into a coherent dataset to monitor the full water cycle – Application to the Mediterranean region

2018 ◽  
Author(s):  
Victor Pellet ◽  
Filipe Aires ◽  
Simon Munier ◽  
Gabriel Jordá ◽  
Diego Fernández Prieto ◽  
...  
Keyword(s):  
Mediterranean Region ◽  
Spatial Information ◽  
Water Cycle ◽  
Hot Spot ◽  
Mean Value ◽  
Basin Scale ◽  
Integration Techniques ◽  
The Mediterranean ◽  
Annual Means ◽  
Closure Constraint

Abstract. Integration techniques are used to combine Earth Observation (EO) datasets to study the Water Cycle (WC). By merging several datasets, they reduce uncertainty and introduce coherency among them. Several EO integration methods are presented and compared: The Optimal Selection (OS) simply choses the best individual datasets. Simple Weighting (SW) is a weighted sum of the datasets to reduce uncertainties. Three other techniques introduce a closure-constraint on the WC budget: (1) The SW plus Post-Filtering (PF) is very efficient but it is applied at the basin-scale only, and lacks in spatial information. (2) By using a spatial interpolation scheme, the INTegration (INT) solution allows obtaining a pixel-scale database, but only for the common period of the all the water components. (3) A simple CALibration (CAL) of the EO datasets is therefore introduced to reproduce the INT results over the longer temporal extent of the EO datasets, but its closure constraint is relaxed. Results are presented over the Mediterranean region, one of the more complex environnements and a hot-spot for climate change. We extended previous techniques to close simultaneously the terrestrial, oceanic and atmospheric WC budgets. We also introduce temporal and spatial multi-scaling constraints. The evaluation is performed for precipitation and evapotranspiration: in addition to better close the WC budget, the integrated database is also closer to in situ measurements. The resulting integrated database provides new estimates for the WC components: stock and flux annual-means are re-evaluated, and we now estimate the Bosporus net-flow mean value at 129 ± 60 mm.yr−1 for the 2004–2009 period. This new EO-based database describing the terrestrial, oceanic and atmospheric WC over the Mediterranean is now proposed to the scientific community.

scholarly journals Integrating multiple satellite observations into a coherent dataset to monitor the full water cycle – application to the Mediterranean region

2019 ◽  
Vol 23 (1) ◽  
pp. 465-491 ◽  
Author(s):  
Victor Pellet ◽  
Filipe Aires ◽  
Simon Munier ◽  
Diego Fernández Prieto ◽  
Gabriel Jordá ◽  
...  
Keyword(s):  
Mediterranean Region ◽  
Water Cycle ◽  
Climate Change Impacts ◽  
Mountainous Regions ◽  
Multi Scale ◽  
Earth Observations ◽  
Integration Techniques ◽  
Gibraltar Strait ◽  
The Mediterranean ◽  
First Time

Abstract. The Mediterranean region is one of the climate hotspots where the climate change impacts are both pronounced and documented. The HyMeX (Hydrometeorological Mediterranean eXperiment) aims to improve our understanding of the water cycle from the meteorological to climate scales. However, monitoring the water cycle with Earth observations (EO) is still a challenge: EO products are multiple, and their utility is degraded by large uncertainties and incoherences among the products. Over the Mediterranean region, these difficulties are exacerbated by the coastal/mountainous regions and the small size of the hydrological basins. Therefore, merging/integration techniques have been developed to reduce these issues. We introduce here an improved methodology that closes not only the terrestrial but also the atmospheric and ocean budgets. The new scheme allows us to impose a spatial and temporal multi-scale budget closure constraint. A new approach is also proposed to downscale the results from the basin to pixel scales (at the resolution of 0.25∘). The provided Mediterranean WC budget is, for the first time, based mostly on observations such as the GRACE water storage or the netflow at the Gibraltar Strait. The integrated dataset is in better agreement with in situ measurements, and we are now able to estimate the Bosporus Strait annual mean netflow.

scholarly journals Modeling the Pathways and Accumulation Patterns of Micro- and Macro-Plastics in the Mediterranean

2021 ◽  
Vol 8 ◽  
Author(s):  
Kostas Tsiaras ◽  
Yannis Hatzonikolakis ◽  
Sofia Kalaroni ◽  
Annika Pollani ◽  
George Triantafyllou
Keyword(s):  
Water Column ◽  
Wind Wave ◽  
Hot Spot ◽  
Sea Surface ◽  
Biogeochemical Model ◽  
Near Surface ◽  
Size Classes ◽  
Basin Scale ◽  
The Mediterranean ◽  
The Impact

The Mediterranean is considered a hot-spot for plastic pollution, due to its semi-enclosed nature and heavily populated coastal areas. In the present study, a basin-scale coupled hydrodynamic/particle drift model was used to track the pathways and fate of plastics from major land-based sources (coastal cities and rivers), taking into account of the most important processes (advection, stokes drift, vertical and horizontal mixing, sinking, wind drag, and beaching). A hybrid ensemble Kalman filter algorithm was implemented to correct the near- surface circulation, assimilating satellite data (sea surface height, temperature) in the hydrodynamic model. Different size classes and/or types of both micro- and macroplastics were considered in the model. Biofouling induced sinking was explicitly described, as a possible mechanism of microplastics removal from the surface. A simplified parameterization of size-dependent biofilm growth has been adopted, as a function of bacterial biomass (obtained from a biogeochemical model simulation), being considered a proxy for the biofouling community. The simulated distributions for micro- and macroplastics were validated against available observations, showing reasonable agreement, both in terms of magnitude and horizontal variability. An 8-year simulation was used to identify micro- and macroplastics accumulation patterns in the surface layer, water column, seafloor and beaches. The impact of different processes (vertical mixing, biofouling, and wind/wave drift) was identified through a series of sensitivity experiments. For both micro- and macroplastics, distributions at sea surface were closely related to the adopted sources. The microplastics concentration was drastically reduced away from source areas, due to biofouling induced sinking, with their size distribution dominated by larger (>1 mm) size classes in open sea areas, in agreement with observations. High concentration patches of floating plastics were simulated in convergence areas, characterized by anticyclonic circulation. The distribution of macroplastics on beaches followed the predominant southeastward wind/wave direction. In the water column, a sub-surface maximum in microplastics abundance was simulated, with increasing contribution of smaller particles in deeper layers. Accumulation of microplastics on the seafloor was limited in relatively shallow areas (<500 m), with bottom depth below their relaxation depth due to defouling. The simulated total amount of floating plastics (∼3,760 tonnes) is comparable with estimates from observations.

scholarly journals Biogeochemical response of the Mediterranean Sea to the transient SRES–A2 climate change scenario

2018 ◽  
Author(s):  
Camille Richon ◽  
Jean-Claude Dutay ◽  
Laurent Bopp ◽  
Briac Le Vu ◽  
James C. Orr ◽  
...  
Keyword(s):  
Climate Change ◽  
Mediterranean Sea ◽  
Nutrient Limitation ◽  
Mediterranean Region ◽  
Hot Spot ◽  
Nutrient Concentrations ◽  
Change Scenario ◽  
Nutrient Inputs ◽  
The Mediterranean ◽  
Ipcc Sres

Abstract. The Mediterranean region is a climate change hot-spot. Increasing greenhouse gas emissions are projected to lead to a significant warming of Mediterranean Sea waters, as well as major changes in its circulation, but the subsequent effects of such changes on marine biogeochemistry are still poorly understood. Our aim is to investigate the changes in nutrient concentrations and biological productivity in response to climate change in the Mediterranean region. To do so, we perform transient simulations with the coupled high resolution model NEMOMED8/PISCES using the pessimistic IPCC SRES-A2 socio-economic scenario and corresponding Atlantic, Black Sea, and coastal nutrient inputs. Our results indicate that nitrate is accumulating in the Mediterranean Sea over the 21st century, whereas no tendency is found for phosphorus. These contrasted variations result from an unbalanced nitrogen-to-phosphorus input from external sources and lead to changes in phytoplankton nutrient limitation factors. In addition, phytoplankton net primary productivity is reduced by 10 % in the 2090s in comparison to the present state, with reductions of up to 50 % in some regions such as the Aegean Sea as a result of nutrient limitation and vertical stratification. We also perform sensitivity tests in order to study separately the effects of climate and biogeochemical input changes on the Mediterranean future state. This article is a first step in the study of transient climate change effects on the Mediterranean biogeochemistry, but calls for coordinated multi-model efforts to explore the various uncertainty sources of such a future projection.

scholarly journals Geo-Hydrological Events and Temporal Trends in CAPE and TCWV over the Main Cities Facing the Mediterranean Sea in the Period 1979–2018

Atmosphere ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 89
Author(s):  
Guido Paliaga ◽  
Antonio Parodi
Keyword(s):  
Mediterranean Sea ◽  
Mediterranean Region ◽  
Hot Spot ◽  
Convective Available Potential Energy ◽  
Temporal Trends ◽  
Meteorological Variables ◽  
Trend Test ◽  
Increasing Trend ◽  
The Mediterranean ◽  
Precipitation Events

The Mediterranean region is regarded as the meeting point between Europe, Africa and the Middle East. Due to favourable climatic conditions, many civilizations have flourished here. Approximately, about half a billion people live in the Mediterranean region, which provides a key passage for trading between Europe and Asia. Belonging to the middle latitude zone, this region experiences high meteorological variability that is mostly induced by contrasting hot and cold air masses that generally come from the west. Due to such phenomenon, this region is subject to frequent intensive precipitation events. Besides, in this complex physiographic and orographic region, human activities have contributed to enhance the geo-hydrologic risk. Further, in terms of climate change, the Mediterranean is a hot spot, probably exposing it to future damaging events. In this framework, this research focuses on the analysis of precipitation related events recorded in the EM–DAT disasters database for the period 1979–2018. An increasing trend emerges in both event records and related deaths. Then a possible linkage with two meteorological variables was investigated. Significant trends were studied for CAPE (Convective Available Potential Energy) and TCWV (Total Column Water Vapor) data, as monthly means in 100 km2 cells for 18 major cities facing the Mediterranean Sea. The Mann–Kendall trend test, Sen’s slope estimation and the Hurst exponent estimation for the investigation of persistency in time series were applied. The research provides new evidence and quantification for the increasing trend of climate related disasters at the Mediterranean scale: recorded events in 1999–2018 are about four times the ones in 1979–1998. Besides, it relates this rise with the trend of two meteorological variables associated with high intensity precipitation events, which shows a statistically significative increasing trend in many of the analysed cities facing the Mediterranean Sea.

Factors driving the Mediterranean water cycle from a cold and wet glacial past to a warm and dry future

2020 ◽  
Author(s):  
Piero Lionello ◽  
Roberta D'Agostino
Keyword(s):  
Mediterranean Region ◽  
Hydrological Cycle ◽  
Water Cycle ◽  
Cmip5 Models ◽  
Climate Conditions ◽  
Atmospheric Thermodynamics ◽  
The Mediterranean ◽  
The Last Glacial Maximum ◽  
Latitudinal Range ◽  
The Last Glacial

<p>Model simulations of the last glacial maximum (LGM) and RCP8.5 projections suggest that factors responsible for past and future changes in the Mediterranean region are different.  The wet LGM conditions were determined mainly by low evaporation, with some increase of precipitation in the western areas, while dry rcp8.5 conditions will be driven by a reduction of precipitation over the whole region. These changes were caused by atmospheric dynamics (changes of mean atmospheric circulation ) in LGM and it will be caused by the atmospheric thermodynamics (reduction of mean moisture content ) in the future rcp8.5. In both cases, the Mediterranean region appears to be more sensitive to climate change than the rest of areas within the same latitudinal range, particularly considering the hydrological cycle, whose characteristics in winter exhibit large changes between these two different climates. These conclusions emerge from the substantial consensus among six PMIP3 and CMIP5 models, simulating LGM, pre-Industrial and rcp8.5 climate conditions.</p>

Mediterranean Marine heatwaves: On the comparison of the physical drivers behind the 2003 and 2015 events

2020 ◽  
Author(s):  
Sofia Darmaraki ◽  
Samuel Somot ◽  
Robin Waldman ◽  
Florence Sevault ◽  
Pierre Nabat ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Large Scale ◽  
Climate Model ◽  
Heat Budget ◽  
Hot Spot ◽  
Regional Climate ◽  
Detection Algorithm ◽  
Heat Fluxes ◽  
Basin Scale ◽  
The Mediterranean

<p>Over the last decade, an intensification of extreme warm temperature events, termed as marine heatwaves (MHWs), has been reported in the Mediterranean Sea, itself a “Hot Spot” region for climate change. In the summer of 2003, a major MHW occurred in the Mediterranean with abnormal surface temperature anomalies of 2-3 Cº persisting for over a month. In 2015, an undocumented but more intense summer MHW affected almost the entire Mediterranean Sea with regional temperatures anomalies reaching 4-5 Cº. Here, we apply a MHW detection algorithm for long-lasting and large-scale summer events, on the hindcast output of a fully-coupled regional climate model (RCSM). We first examine the spatial variability and temporal evolution of both the 2003 and 2015 events. Then a basin-scale analysis of the mixed layer heat budget during each MHW is performed. The ocean and atmospheric components’ contribution is investigated separately during the onset, peak, and decay phases of both events, in order to disentangle the dominant physical processes behind each event. On the large-scale, our results indicate a key role of the wind forcing and the air-sea heat fluxes, while advection processes become more important at local scales. This study provides a comparison of the underlying mechanisms behind the two most intense MHW detected in the Mediterranean Sea during the last decade, constituting key information for the marine ecosystems of the region.</p>

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