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[en] The daily rainfall data collected in the second half of the last century at 31 climatic stations in Lazio, Italy, have been subjected to statistical analysis in order to describe the pluviometric regime of the whole area on a multi-decadal time scale. The stations, for their geographical distribution within the region under study, are apt to represent different climatic zones, namely, a coastal, a rural, a suburban and an urban zone. The data have been treated both as time series and as geographical statistical variates with the double aim, first, to verify if in the area under study any changes in the yearly precipitation rate, frequency and its distribution over different classes of rain intensity, have occurred in the last 50 years; second, to evidence a possible correlation between the intensity of precipitation and any of some environmental variables such as altitude, distance from the coastline and distance from the urban site. As for the first issue, it can be concluded that the precipitations over the Roman area in the period 1951-2000 show no significant trend; in particular, no trend is visible in any of the single classes of rain intensity, both absolute and percentile-based, considering either their frequency or their percent contribution to the total. As for the second issue, significant correlations have been found in the spatial distribution of rainfall with any of the relevant environmental variables mentioned above. The results of the analysis also show that in the urban area a less amount of rain seem to fall than in the surroundings zones, a result that seems rather anomalous in consideration of the several known factors that favour the intensification of the rainfall in the city with respect to its surroundings. A detailed statistical characterization of all the single 31 stations over the whole period is also given via a separate study of the durations of droughts and of the statistics of rainy days, using best fits based on the Weibull probability distribution
[en] The Tibetan Plateau (TP), with an average elevation of over 4000 m asl and an area of approximately 2.5 x 106 km2, is the highest and most extensive highland in the world and has been called the 'Third Pole'. The TP exerts a huge influence on regional and global climate through thermal and mechanical forcing mechanisms. Because the TP has the largest cryospheric extent outside the polar region and is the source region of all the large rivers in Asia, it is widely recognized to be the driving force for both regional environmental change and amplification of environmental changes on a global scale. Within China it is recognized as the 'Asian water tower'. In this letter, we summarize the recent changes observed in climate elements and cryospheric indicators on the plateau before discussing current unresolved issues concerning climate change in the TP, including the temporal and spatial components of this change, and the consistency of change as represented by different data sources. Based on meteorological station data, reanalyses and remote sensing, the TP has shown significant warming during the last decades and will continue to warm in the future. While the warming is predominantly caused by increased greenhouse gas emissions, changes in cloud amount, snow-albedo feedback, the Asian brown clouds and land use changes also partly contribute. The cryosphere in the TP is undergoing rapid change, including glacier retreat, inconsistent snow cover change, increasing permafrost temperatures and degradation, and thickening of the active layer. Hydrological processes impacted by glacial retreat have received much attention in recent years. Future attention should be paid to additional perspectives on climate change in the TP, such as the variations of climate extremes, the reliability of reanalyses and more detailed comparisons of reanalyses with surface observations. Spatial issues include the identification of whether an elevational dependency and weekend effect exist, and the identification of spatial contrasts in temperature change, along with their causes. These issues are uncertain because of a lack of reliable data above 5000 m asl.
[en] The aim of Imfrex was to evaluate the impact of a climatic change on the frequency of extreme phenomena of wind and rainfall in France. The study is based on an hypothesis proposed by the GIEC and called scenario A2. A first simulation, low resolution 300 km, using a coupled model ocean-atmosphere allowed to provide an evolution scenario for the temperature of the sea surface and the ice field area. A second simulation, high resolution 50 km, provided a daily evolution of the climate during 140 years. Imfrex was organized in five work-packages: the constitution of the data base, the validation of the models, the direct approach the statistical approach and the dynamical approach. (A.L.B.)
[en] Extreme value analysis of meteorological parameters and rainfall have been presented in this paper. The variables examined for extreme value analysis are maximum and minimum air temperature, maximum one-day rainfall, maximum monthly rainfall and annual rainfall. For rainfall statistics, the data for rainfall, collected during 1959 to 2007 were used whereas for other meteorological parameters, the data collected during 1985-2007 were used. The extreme value analysis reveal that the variable such as maximum temperature and annual rainfall obey Fisher-Tippett Type-I extreme value distribution where as minimum air temperature, one-day maximum rainfall and monthly rainfall obey Fisher-Tippett Type-II extreme value distribution function. Various distribution function parameters for each variable are determined. Extreme values corresponding to return periods of 100 years are worked out. These derived extreme values are particularly useful for arriving at suitable design value to ensure the safety of civil structure in and around Trombay with respect to stress due to weather condition. (author)
[en] Using rain gauge and satellite-based rainfall climatologies and the NOAA Storm Prediction Center tornado database (1952-2007), this study found a statistically significant tendency for fall-winter drought conditions to be correlated with below-normal tornado days the following spring in north Georgia (i.e. 93% of the years) and other regions of the Southeast. Non-drought years had nearly twice as many tornado days in the study area as drought years and were also five to six times more likely to have multiple tornado days. Individual tornadic events are largely a function of the convective-mesoscale thermodynamic and dynamic environments, thus the study does not attempt to overstate predictability. Yet, the results may provide seasonal guidance in an analogous manner to the well known Sahelian rainfall and Cape Verde hurricane activity relationships.
[en] We revisit the multifractal analysis of high resolution temporal rainfall using the wavelet transform modulus maxima (WTMM) method. Specifically, we employ a cumulant analysis of the logarithm of the WTMM coefficients to estimate the scaling exponent spectrum τ(q) and the spectrum of singularities D(h). We document that rainfall intensity fluctuations exhibit multifractality from scales of the order of 4-5 minutes up to the storm-pulse duration of 1-2 hours. We also establish long-range dependence consistent with that of a multiplicative cascade
[en] This abstract presents research from two studies investigating urban flood perceptions and mitigative behaviours of private individuals in Canada. The first study, completed in July, 2006, investigated perceptions of overland flooding and sewer backup resulting from extreme rainfall events in Peterborough, Ontario. The second, completed in November, 2007, investigated sewer backup perceptions of homeowners in Edmonton, Alberta and Toronto, Ontario. The research studies sought to explore: Hazard and risk perceptions of individuals affected by overland flooding and sewer backup; Knowledge of mitigative options, and mitigative actions taken by individual residents to reduce the risk of basement flood damage; Attributions of responsibility for urban flood damages; Awareness of municipal actions designed to reduce urban flood risk; Satisfaction with the cost sharing tools of insurance and government relief.