Large-scale atmospheric response to eastern Mediterranean summer-autumn SST anomalies and the associated regional impact

Since the Mediterranean Sea is halfway between subtropical and middle latitudes, and it represents a marginal oceanic region, research has tended to focus on how large-scale modes of atmospheric variability modulate its surface temperature. Conversely, the present study examines the potential influence of the Mediterranean Sea surface temperature (SST) anomalies on the Northern Hemisphere atmospheric circulation. In particular, this work explores the large-scale changes in the global circulation forced/influenced by the eastern Mediterranean summer-autumn SST pattern. To isolate the atmospheric response, AGCM sensitivity experiments with prescribed SST over the Mediterranean Sea and climatology elsewhere are analysed. Observational diagnostics upon the period used to define the boundary conditions (1979–2002) are also interpreted. Our results support the hypothesis of an atmospheric pattern initiated in the Mediterranean basin, pointing out both a local baroclinic response and a barotropic circumglobal anomaly. This atmospheric teleconnection pattern projects onto a hemispheric wave-like structure, reflecting the waveguide effect of the westerly jets. Results suggest, thereby, that the recurrent summer-autumn circumglobal teleconnection pattern can be excited locally by changes in the atmosphere over the Mediterranean region. A linear behaviour is found upon a regional impact over northeastern Africa. The remote impacts present however a nonlinear signature: anomalous warm conditions influencing on northern Europe and Euro–Asia, whereas anomalous cold conditions impacting more on the North Pacific basin. Limitations in our model setup are also discussed.     

Rainfall spatial organization and areal reduction factors in the metropolitan area of Barcelona (Spain)

The rainfall spatial organization in the metropolitan area of Barcelona (Spain) has been studied from records of an urban rain gauge network in the period 1994–2009. Using statistical and regional analysis techniques, correlation between data recorded by the different rain gauges has been calculated, and the effective number of independent stations (n _eq) equivalent to the used network has been determined. It has been found out that for durations longer than 20 min, the areal rainfall return period observed for a storm registered by the network approximately decreases by a factor of 1/n _eq in relation to the current point rainfall intensity–duration–frequency relationships for the metropolitan area of Barcelona. Using objective analysis techniques, continuous precipitation fields have been generated on a regular grid with a spatial resolution of 300?×?300 m for the storms registered by the rain gauges from 1994 to 2009, for durations from 10 min to 24 h. The precipitation fields obtained have been useful to estimate the characteristic areal reduction factors in the metropolitan area of Barcelona. A direct relationship has been found between the areal reduction factor for all the area corresponding to the urban rainfall network of Barcelona and the effective number of n _eq for every duration considered.     

Scientific management of Mediterranean coastal zone: a hybrid ocean forecasting system for oil spill and search and rescue operations

The oil spill from Prestige tanker showed the importance of scientifically based protocols to minimize the impacts on the environment. In this work, we describe a new forecasting system to predict oil spill trajectories and their potential impacts on the coastal zone. The system is formed of three main interconnected modules that address different capabilities: (1) an operational circulation sub-system that includes nested models at different scales, data collection with near-real time assimilation, new tools for initialization or assimilation based on genetic algorithms and feature-oriented strategic sampling; (2) an oil spill coastal sub-system that allows simulation of the trajectories and fate of spilled oil together with evaluation of coastal zone vulnerability using environmental sensitivity indexes; (3) a risk management sub-system for decision support based on GIS technology. The system is applied to the Mediterranean Sea where surface currents are highly variable in space and time, and interactions between local, sub-basin and basin scale increase the non-linear interactions effects which need to be adequately resolved at each one of the intervening scales. Besides the Mediterranean Sea is a complex reduced scale ocean representing a real scientific and technological challenge for operational oceanography and particularly for oil spill response and search and rescue operations.     

Morphotectonic study of the Greater Antilles

The first morphotectonic model of the Greater Antilles is presented. The model is adjusted to the current dynamics between the Caribbean and North American plates. It is mainly elaborated by Rantsman’s methodology. We determined 2 megablocks, 7 macroblocks, 42 mesoblocks, 653 microblocks and 1264 nanoblocks. They constitute a set of active blocks under rotation, uplifting and tilting movements. A total of 11 active knots of faults and 8 cells are the main articulation areas. The largest seismogenetic structures in the Northern Caribbean are an array of the active fault segments. The majority of them are in the Caribbean-North American Plate Boundary Zone, the Hispaniola has the most complex neotectonic structure–associated with the central axis of the morphotectonic deformations in the region.