1,721,876 research outputs found
The role of systematic errors
Full text linkA short commentary on the role of systematic errors in climate simulations
On the coupling between vegetation and rainfall inter-annual anomalies: Possible contributions to seasonal rainfall predictability over land areas
No full textVegetation, rainfall, climateIt's well known that rainfall affects vegetation through its effect on soil moisture content, but the extent to which vegetation could in turn impact precipitation occurrence is poorly understood. Here we focus on the assessment, from observations, of the reciprocal forcing of seasonal-mean vegetation and rainfall interannual anomalies over land areas using the coupled manifold technique. Considering global lands, we estimate at the 1% significance level that 19% (12%) of the vegetation (precipitation) variance is forced by precipitation (vegetation). Our analysis reveals that the dominant component of the vegetation-forced rainfall variability is a delayed response to ENSO cycles. Vegetation appears to provide a biophysical memory of ENSO and is supposed to act through delayed feedbacks on rainfall. As ENSO cycles are currently well predicted by dynamical seasonal forecasting systems, this result displays the potential for a reliable soil moisture-vegetation initialization to improve rainfall prediction over lands
The coupled manifold
No full textA new method is presented to detect the portion of variability connected between two climatic fields. The method is a realization of the Procrustes problem, and it is a generalization of methods for analysis of variance such as the singular value decomposition (SVD) or canonical correlation analysis (CCA). The Procrustes formulation offers a general framework to link together variance analysis methods. and regression methods, including as special cases SVD and CCA. Using this approach two fields can be divided into a subspace where variations of one field are connected to variations of the other field, the coupled manifold, and a subspace where variations are independent, the free manifold. The unified approach can be applied to prescribed SST experiments, in which case it recovers consistent results with other methods designed to identify the forced portion of variance, but it can now be extended also to the coupled case or to observations. Some examples from prescribed SST simulation experiments and observations are discussed
A Guide to Empirical Orthogonal Functions for Climate Data Analysis
No full textClimatology and meteorology have basically been a descriptive science until it became possible to use numerical models, but it is crucial to the success of the strategy that the model must be a good representation of the real climate system of the Earth. Models are required to reproduce not only the mean properties of climate, but also its variability and the strong spatial relations between climate variability in geographically diverse regions. Quantitative techniques were developed to explore the climate variability and its relations between different geographical locations. Methods were borrowed from descriptive statistics, where they were developed to analyze variance of related observations-variable pairs, or to identify unknown relations between variables.
A Guide to Empirical Orthogonal Functions for Climate Data Analysis uses a different approach, trying to introduce the reader to a practical application of the methods, including data sets from climate simulations and MATLAB codes for the algorithms. All pictures and examples used in the book may be reproduced by using the data sets and the routines available in the book .
Though the main thrust of the book is for climatological examples, the treatment is sufficiently general that the discussion is also useful for students and practitioners in other fields
The Climate Dilemma
No full textClimate has become one of the most topical issues over the last two to three decades. It has graduated from the status of obscure scientific debate to that of a global geopolitical issue. Climate itself is a sophisticated concept that is somewhat different to that used or discussed in everyday life. The basic nature of the globe's climate is regulated by the global energy balance, as are the principal climate mechanisms. These in turn are modulated via the complex nonlinear interactions between the components that comprise the global climate system. These non-linear interactions generate an intense variability in climate that makes detection of small, secular trends in climate very difficult. The increase of carbon dioxide and surface temperatures is now being established as a fact, but the attribution of the temperature increase to carbon dioxide increases is a complex challenge. Due to constraints imposed by the current level of climate modeling technology we cannot perform crucial experiments in climate science. Accordingly we have to rely on a combination of numerical experiments, often with a considerable degree of parameterization of key climate processes and consensus among experts to reach provisional explanations concerning the causes, magnitude and intensity of climate change. Although the scientific research procedure is incremental in nature, the process of data collection, experimentation and verification of modeling outcomes, results in the steady accumulation of knowledge. It is this knowledge on which we rely for drawing conclusions about the state of the globe's climate and that policy makers use in drawing up recommendations related to mitigation of and adaptation to climatic variability and change
Wireless ATM layouts for chain networks
Full text linkIn this paper we consider the problem of constructing ATM layouts for wireless networks in which mobile users can move along a chain of base stations. We first show that deciding the existence of a layout with maximum hop count h, load l and channel distance d is NP-complete for every fixed value of d greater or equal to 1. We then provide optimal layout constructions for the case d less than or equal to 2. Finally, optimal layout constructions are obtained also for any d within the class of the so-called canonic layouts, that so far have always been shown to be the optimal ones
Regional Assessment of Climate Change in the Mediterranean, Volume 2: Agriculture,forests, ecosystems services and people
No full textThe CIRCE project started on 1 April 2007 and ended on 30 June 2011, coordinated by the Istituto Nazionale di Geofisca e Vulcanologia, Italy. The work of the CIRCE project was split into 13 research lines plus one for coordination and communication. Research lines were subdivided into several work packages activities.
The main objectives of CIRCE were to predict and to quantify the physical impacts of climate change in the Mediterranean, and to assess the most influential consequences for the population of the region. The knowledge yielded by the different specialized investigations were linked in an integrated interdisciplinary approach designed to study the total effect of climate change. CIRCE integrated cutting-edge scientific research with the needs of end-users and communities. Thus, CIRCE was able to quantify the impact of global warming on Mediterranean climate variables, while also taking into account the regional, social, economic and policy aspects of the process. That allowed to overcome the imbalance faced by a number of research projects on climate impacts between physical and natural science and social sciences so as to build a new vision of the interactions between climate factors and socioeconomic evolutions
Sensitivity of the Asian summer monsoon to the horizontal resolution: Differences between AMIP-type and coupled model experiments
No full textA set of experiments forced with observed
SST has been performed with the Echam4 atmospheric
GCM at three different horizontal resolutions (T30,
T42 and T106). These experiments have been used to
study the sensitivity of the simulated Asian summer
monsoon (ASM) to the horizontal resolution. The
ASM is reasonably well simulated by the Echam4
model at all resolutions. In particular, the low-level
westerly flow, that is the dominant manifestation of the
Asian summer monsoon, is well captured by the model,
and the precipitation is reasonably simulated in intensity
and space appearance. The main improvements
due to an higher resolution model are associated to
regional aspects of the precipitation, for example the
Western Ghats precipitation is better reproduced. The
interannual variability of precipitation and wind fields
in the Asian monsoon region appears to be less affected
by an increase in the horizontal resolution than
the mean climatology is. A possible reason is that the
former is mainly SST-forced. Besides, the availability
of experiments at different horizontal resolution realized
with the Echam4 model coupled to a global oceanic
model allows the possibility to compare these
simulations with the experiments previously described.
This analysis showed that the coupled model is able to
reproduce a realistic monsoon, as the basic dynamics of
the phenomenon is captured. The increase of the horizontal
resolution of the atmospheric component
influences the simulated monsoon with the same
characteristics of the forced experiments. Some basic
features of the Asian summer monsoon, as the interannual
variability and the connection with ENSO, are
further investigated.Published273-290JCR Journalreserve
- …
