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[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] The description is given of a cooling tower protected against projectiles carried by storms, which can be used, inter alia, for the cooling facilities of nuclear power stations. It is characterized by its being composed of several closed cooling cells arranged around the periphery of a central opening. Each cell has a cold air intake on the outside, several blowers located inside and a hot air outlet along the inside
[fr]On decrit une tour de refrigeration protegee contre les projectiles entraines par les tempetes qui peut etre utilisee, notamment pour les installations de refroidissement des centrales nucleaires. Elle est caracterisee par sa constitution en plusieurs cellules de refrigeration fermees disposees autour de la peripherie d'une ouverture centrale. Chacune de ces cellules comporte une entree d'air froid sur son cote exterieur, plusieurs ventilateurs situes a l'interieur et une sortie d'air chaud le long de son cote interieur
[en] Sea surface temperature (SST) is not the only oceanic parameter that can play a key role in the interannual variability of Northeast Pacific hurricane activity. Using several observational data sets and the statistical technique of multiple linear regression analysis, we show that, along with SST, the thermocline depth (TD) plays an important role in hurricane activity at interannual timescales in this basin. Based on the parameter that dominates, the ocean basin can be divided into two sub-regions. In the Southern sub-region, which includes the hurricane main development area, interannual variability of the upper-ocean heat content (OHC) is primarily controlled by TD variations. Consequently, the interannual variability in the hurricane power dissipation index (PDI), which is a measure of the intensity of hurricane activity, is driven by that of the TD. On the other hand, in the Northern sub-region, SST exerts the major control over the OHC variability and, in turn, the PDI. Our study suggests that both SST and TD have a significant influence on the Northeast Pacific hurricane activity at interannual timescales and that their respective roles are more clearly delineated when sub-regions along an approximate north–south demarcation are considered rather than the basin as a whole. (letter)
[en] An elementary derivation is given for the shape of the wake pattern of a boat traveling at constant velocity in deep water. We find essentially the same results as those found in standard treatments, but our mathematics is easier. All results follow from the fact that the group velocity is half the phase velocity
[en] A critical prerequisite of risk prevention measures for natural hazards is from the results of forensic disaster investigations (FDIs). The current studies of the FDIs are limited by data issues including data availability and data reliability. The applications of crowdsourcing method in natural disasters indicate the potential to provide data support for the FDIs. However, there is very limited existing research on the use of crowdsourcing data for the FDIs. Following the requirements published by the Integrated Research on Disaster Risk program for FDIs, this paper establishes the process map for conducting the FDIs by scenario analysis approach with the crowdsourcing and crowdsensor data. Hurricane Harvey is used as the case study to implement the process map. The results show that the use of crowdsourcing data for the FDIs is feasible. Though this paper takes practical measures for improving the reliability of crowdsourcing data (i.e., little data size) in the case study, future research can focus on the development of advanced algorithm for the crowdsourcing data quality validation.
[en] A case of deep and rapid cyclo genesis over the Gulf of Genoa and its impact on a limited area energy budget are examined in this paper. Energy components, including boundary and generation terms, are calculated for the period 18-21 November 1999 over a limited region in which this disturbance is the major synoptic-scale feature. The energy contents and their changes through the studied atmospheric volume are discussed in the course of the cyclone's development. The combined boundary pressure work and dissipation terms of the zonal and eddy kinetic energies, as well as generation terms of zonal and eddy available energies, are computed as residuals. Data of ALADIN/LACE model are used as input fields for calculations. Formation of the cyclone under study initiated in the upper atmospheric levels. At the initial stage of its development, energy conversion C(KZ,KE) was intense. Thus, zonal flow acted as a source of eddy kinetic energy. The disturbance was induced by a very strong wind shear and the progress of the vortex toward the lower atmospheric layers was associated with downward eddy kinetic energy transport (from the jet stream level toward the surface). Simultaneously, the upward transport of both zonal and eddy available energies (from the lower and middle troposphere toward the upper levels) was present. The disturbance was a consequence of very strong wind shear and it was evident how it progressed toward the lower atmospheric layers. As the vortex reached the ground, energy conditions allowed its possible further growth there. In spite of that, the surface cyclone lifetime was very short due to dynamical conditions that attenuated cyclone development