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Potential Instability (potential + instability)
Selected AbstractsStatistical downscaling model based on canonical correlation analysis for winter extreme precipitation events in the Emilia-Romagna regionINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2008A. Busuioc Abstract Optimum statistical downscaling models for three winter precipitation indices in the Emilia-Romagna region, especially related to extreme events, were investigated. For this purpose, the indices referring to the number of events exceeding the long-term 90 percentile of rainy days, simple daily intensity and maximum number of consecutive dry days were calculated as spatial averages over homogeneous sub-regions identified by the cluster analysis. The statistical downscaling model (SDM) based on the canonical correlation analysis (CCA) was used as downscaling procedure. The CCA was also used to understand the large-/regional-scale mechanisms controlling precipitation variability across the analysed area, especially with respect to extreme events. The dynamic (mean sea-level pressure-SLP) and thermodynamic (potential instability-,Q and specific humidity-SH) variables were considered as predictors (either individually or together). The large-scale SLP can be considered a good predictor for all sub-regions in the dry index case and for two sub-regions in the case of the other two indices, showing the importance of dynamical forcing in these cases. Potential instability is the best predictor for the highest mountain region in the case of heavy rainfall frequency, when it can be considered as a single predictor. The combination of dynamic and thermodynamic predictors improves the SDM's skill for all sub-regions in the dry index case and for some sub-regions in the simple daily intensity index case. The selected SDMs are stable in time only in terms of correlation coefficient for all sub-regions for which they are skilful and only for some sub-regions in terms of explained variance. The reasons are linked to the changes in the atmospheric circulation patterns influencing the local rainfall variability in Emilia-Romagna as well as the differences in temporal variability over some sub-regions and sub-intervals. It was concluded that the average skill over an ensemble of the most skilful and stable SDMs for each region/sub-interval gives more consistent results. Copyright © 2007 Royal Meteorological Society [source] Disaggregate Wealth and Aggregate Consumption: an Investigation of Empirical Relationships for the G7*OXFORD BULLETIN OF ECONOMICS & STATISTICS, Issue 2 2003Joseph P. Byrne To date, studies of wealth effects on consumption have mainly used aggregate wealth definitions on a single-country basis. This study seeks to break new ground by analysing disaggregated financial wealth in consumption functions for G7 countries. Contrary to earlier empirical work, we find that illiquid financial wealth (i.e. securities, pensions and mortgage debt) tends to be a more important long-run determinant of consumption than liquid financial wealth. These results imply potential instability in consumption functions employing aggregate wealth. Our results are robust using SURE; when testing with a nested specification; and when using a linear model. [source] Extension of potential predictability of Indian summer monsoon dry and wet spells in recent decadesTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 648 2010J. M. Neena Abstract An understanding of the limit on potential predictability is crucial for developing appropriate tools for extended-range prediction of active/break spells of the Indian summer monsoon (ISM). The global low-frequency changes in climate modulate the annual cycle of the ISM and can influence the intrinsic predictability limit of the ISM intraseasonal oscillations (ISOs). Using 104-year (1901,2004) long daily rainfall data, the change in potential predictability of active and break spells are estimated by an empirical method. It is found that the potential predictability of both active and break spells have undergone a rapid increase during the recent three decades. The potential predictability of active spells has shown an increase from one week to two weeks while that for break spells increased from two weeks to three weeks. This result is interesting and intriguing in the backdrop of recent finding that the potential predictability of monsoon weather has decreased substantially over the same period compared to earlier decades due to increased potential instability of the atmosphere. The possible role of internal dynamics and external forcing in producing this change has been explored. The changes in energy exchange between the synoptic and ISO scale and the different ISO modes as evidenced by energetics computations in frequency domain also support the increased potential predictability of ISO. Our finding provides optimism for improved and useful extended-range prediction of monsoon active and break spells. Copyright © 2010 Royal Meteorological Society [source] A review of the initiation of precipitating convection in the United KingdomTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 617 2006Lindsay J. Bennett Abstract Recent severe weather events have prompted the European scientific community to assess the current understanding of convective processes with a view to more detailed and accurate forecasting. The initial development of convective cells remains one of the least understood aspects and one in which limited research has taken place. The important processes can be split into three main areas: boundary-layer forcing, upper-level forcing and secondary generation. This paper is a review of the mechanisms responsible for the initiation of precipitating convection in the United Kingdom; i.e. why convective clouds form and develop into precipitating clouds in a particular location. The topography of the United Kingdom has a large influence on the initiation of convection. Boundary-layer forcings determine the specific location where convection is triggered within larger regions of potential instability. These latter regions are created by mesoscale or synoptic-scale features at a higher level such as dry intrusions and mesoscale vortices. Second-generation cells are those formed by the interaction of outflow from convective clouds with the surrounding environmental air. Large, long-lived thunderstorm complexes can develop when new cells are repeatedly triggered on one side of the system. Current and future field campaigns along with the development of high-resolution modelling will enable these processes to be investigated in more detail than has previously been achieved. © Royal Meteorological Society, 2006. Contributions by P. A. Clark and M. E. B. Gray are Crown Copyright. [source] Convective mixing in a tropopause foldTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 599 2004H. J. Reid Abstract We present a case study of the passage of a tropopause fold over the UK behind a cold front, with emphasis on the mixing caused by convection extending into the fold. The event took place on 15,16 January 1999, and was the subject of intensive observations using the Met Office C130 aircraft and the mesosphere,stratosphere,troposphere (MST) radar at Aberystwyth. Here we concentrate on radar and satellite observations during the afternoon of 16 January, when the surface cold front had passed over the UK. A tongue of moist air moved north-eastwards over Wales at 700 hPa at this time, which, because of the very dry air in the fold above, resulted in potential instability. The resulting convection was clearly observed in NOAA satellite images. The MST radar depicted the passage of the cold front and tropopause fold as a layer of high-echo power and vertical wind shear ascending with time. Spectral widths showed the fold to be free of turbulence until 1200 UTC on 16 January, when convection was observed reaching into the frontal zone and generating turbulence. Eddy dissipation and diffusivity rates of 8.6 mW kg,1 and 8.5 m2s,1, respectively, were derived for this event. To place these figures in context, they are compared with corresponding rates derived for sixteen other passages of tropopause folds over the radar, each resulting from shear rather than convective instability. The convective event is found to be comparable to the strongest shear events, and to correspond to moderate turbulence as experienced by an aircraft. This process is of potential importance for atmospheric chemistry because it mixes boundary layer air directly with stratospheric air over a timescale of 1,2 hours. Copyright © 2004 Royal Meteorological Society [source] LIMITS TO COMPETITION AND REGULATION IN PRIVATIZED ELECTRICITY MARKETSANNALS OF PUBLIC AND COOPERATIVE ECONOMICS, Issue 4 2009Hulya Dagdeviren ABSTRACT,:,Privatization of electricity has been extensive both in the developed and the developing world. Failures in various areas have led to the emergence of a new consensus which regards competitive pressures and regulation as crucial for utility privatizations to work. This review paper presents a critical evaluation of this newly found wisdom with reference to the developing economies. The experience in the developed world, especially in the USA and the UK, has been used to draw conclusions for the developing economies. Overall, the paper highlights the problems associated with the ,competitive model' both in the developed and developing world and points to the potential instability in private competitive power supply systems. It also examines the degree to which regulation can be a panacea for market failures and structural problems under private provision. [source] | |||||||||||||