Luis Gimeno

Chapter 3 Relations between variability in the Mediterranean region and mid-latitude variability

Publisher Summary The Mediterranean climate is under the influence of both tropical and mid-latitude climate dynamics, being directly affected by continental and maritime air masses with significant origin differences. The peak of the winter season occurs between December and February, when the mid-latitude cyclone belt has usually reached its southernmost position. However, spring and autumn also contribute to a significant amount of precipitation. Being located at the southern limit of the North Atlantic storm tracks; the Mediterranean region is particularly sensitive to interannual shifts in the trajectories of mid-latitude cyclones that can lead to the remarkable anomalies of precipitation and, to a lesser extent, of temperature. Storm-track variability impacts primarily the western Mediterranean, but it hasa signature clearly detected in the eastern Mediterranean as well. The complex orography that characterizes most regions surrounding the Mediterranean basin can modulate and even distort climate anomaly patterns that otherwise would be geographically much more homogenous. Lack of water in winter and spring reflects in the crop yield. However, too much water in winter is harmful by drowning the seeds and retarding root development. The variability of precipitation plays a crucial role in the management of regional agriculture, in environment, in water resources and ecosystems, as well as social development and behavior.

Wave Energy Associated with the Variability of the Stratospheric Polar Vortex

Abstract A study is performed on the energetics of planetary wave forcing associated with the variability of the northern winter polar vortex. The analysis relies on a three-dimensional normal mode expansion of the atmospheric general circulation that allows partitioning the total (i.e., kinetic + available potential) atmospheric energy into the energy associated with Rossby and inertio-gravity modes with barotropic and baroclinic vertical structures. The analysis mainly departs from traditional ones in respect to the wave forcing, which is here assessed in terms of total energy amounts associated with the waves instead of heat and momentum fluxes. Such an approach provides a sounder framework than traditional ones based on Eliassen–Palm (EP) flux diagnostics of wave propagation and related concepts of refractive indices and critical lines, which are strictly valid only in the cases of small-amplitude waves and in the context of the Wentzel–Kramers–Brillouin–Jeffries (WKBJ) approximation. Positive (negati...

Dry and wet conditions in the Niger River Basin and its link with atmospheric moisture transport

In West Africa, is located the Niger River Basin (NRB). Dry and wet conditions were investigated in this basin during the rainy (May-October) and dry (November-April) seasons, from 1980 to 2014. To do this was, calculated the Standardized Precipitation-Evapotranspiration Index (SPEI) at the time scale of 6-months for the whole NRB. The Lagrangian model FLEXPART v9.0 has been used to compute over the main semi-annual climatological moisture sources of the NRB, the budget of evaporation minus precipitation (E-P) over 10-day backward trajectories from the NRB itself. Positive (negative) (E-P) values indicate moisture uptake (loss). This permit evaluating the role of continental and oceanic sources of moisture separately for composites of extremely and severely dry and wet conditions in the basin. The results show for the dry season the negative trend of the April-SPEI6 values and the (E-P)>0 values obtained over the tropical east-north Atlantic Ocean (NAtl), the western Sahel and the Mediterranean region. Over these sources, the anomalies of (E-P) for driest and wettest composites indicate their direct response. On the contrary, for the rainy season, the October-SPEI6 values trend is positive, as well it occurs for the moisture uptake over the South Sahel (SSah) and the NRB itself. The anomalies of the (E-P) values for driest and wettest rainy seasons composites suggest a direct relationship with those obtained mainly over SSah, SAtl and the NRB itself.

CLLJ and WHWP heat content as a constrain to North American Monsoon activation moisture supply

With a well defined long term basis analysis of moisture supply to the North American Monsoon (NAM) domain based upon FLEXPART Lagrangian trajectories, the role of the Caribbean Sea and the Gulf of Mexico as the primary moisture source for the monsoon onset is analyzed. Regardless the NAM area requires the input from other sources, it is the eastern source which provides the required supply to activate the land moisture processes. Here we study how the warm SSTs of the WHWP enclosed region increase the moisture content, modulate the depth of the boundary layer and to which extent the CLLJ is able to advect the moist air towards the eastern Sierra Madre region. The analysis focuses on how different these processes are for warm and cold ENSO events and the relevance of this variability mode as a control of the meridional rainfall distribution across tropical north America under ENSO forcing. For this analysis, a different approach for the WHWP characterization is implemented as a new volume heat content definition is used for the WHWP instead of the traditional area defined index.

Seasonal and annual daily precipitation risk maps for the Andean region of Peru

We develop for the first time maps of annual and seasonal extreme precipitation risk in the Andean region of Peru. For this purpose, we used the complete daily precipitation records existing in Peru. In each meteorological station, we obtained series of events of de-clustered daily intensity, total precipitation duration, total magnitude and dry-spell length. Using a peak-overthreshold approach we fitted the annual and seasonal series of these variables to a GeneralizedPareto distribution, obtained the distribution parameters and validated the performance of different thresholds to obtain reliable estimations of the precipitation probability. The parameters obtained in the different meteorological stations were mapped using a universal krigging approach using the elevation and the distance to the ocean as co-variables. Maps of parameters were validated using a jack-knife approach and maximum expected precipitation intensity, magnitude, duration and dryspell length estimated for a period of 25 and 50 years. The reliability of the spatial methodology was validated comparing observed precipitation and estimated by the spatial modelling in the different stations.

Trends and directions in climate research. Introduction.

The relevance of climate research has increased considerably in the last two decades as a result of awareness in the scientific community that our climate has been changing and is bound to change even further in the next century.1 The recent award of the Nobel peace prize to the International Panel for Climate Change (IPCC) has raised this awareness to the highest level, stressing the imperative need for our own generation to start solving this complex problem. But what triggers the widespread media coverage and the interest of the average person on the street is the possibility that these changes may be associated, at least partially, with increasing levels of anthropogenic economic activities (industry, transport, agriculture, and electricity production, to name a few), particularly since the industrial revolution.1 The anthropogenic role in recent climate trends is now becoming clearer. Nevertheless, it is worth stressing that there have always been changes in climate in previous epochs, and these changes have occurred at different temporal scales prior to and after the emergence of the hominids.2–4 The main objective of climate research is to improve our understanding of the nature of the various components of the climate system and the main causes that are responsible for climate variability and climate change.5 There-