Sensitivity of inland decay of North Atlantic tropical cyclones to soil parameters

Using the HURDAT best track analysis of track and intensity of tropical cyclones that made landfall over the continental United States during the satellite era (1980?C2005), we analyze the role of land surface variables on the cyclone decay process. The land surface variables considered in the present study included soil parameters (soil heat capacity and its surrogate soil bulk density), roughness, topography and local gradients of topography. The sensitivity analysis was carried out using a data-adaptive genetic algorithm approach that automatically selects the most suitable variables by fitting optimum empirical functions that estimates cyclone intensity decay in terms of given observed variables. Analysis indicates that soil bulk density (soil heat capacity) has a dominant influence on cyclone decay process. The decayed inland cyclone intensities were found to be positively correlated with the cube of the soil bulk density (heat capacity). The impact of the changes in soil bulk density (heat capacity) on the decayed cyclone intensity is higher for higher intensity cyclones. Since soil bulk density is closely related to the soil heat capacity and inversely proportional to the thermal diffusivity, the observed relationship can also be viewed as the influence of cooling rate of the land surface, as well as the transfer of heat and moisture underneath a land-falling storm. The optimized prediction function obtained by statistical model processes in the present study that predicts inland intensity changes during 6-h interval showed high fitness index and small errors. The performance of the prediction function was tested on inland tracks of eighteen hurricanes and tropical storms that made landfall over the United States between 2001 and 2010. The mean error of intensity prediction for these cyclones varied from 1.3 to 15.8 knots (0.67?C8.12?m?s^?1). Results from the data-driven analysis thus indicate that soil heat flux feedback should be an important consideration for the inland decay of tropical cyclones. Experiments were also undertaken using Weather Research Forecasting (WRF) Advanced Research Version (ARW ver 3.3) to assess the sensitivity of the soil parameters (roughness, heat capacity and bulk density) on the post-landfall structure of select storms. The model was run with 1-km grid spacing, limited area single domain with boundary conditions from the North American Regional Reanalysis. Of different experiments, only the surface roughness change and soil bulk density (heat capacity) change experiments showed some sensitivity to the intensity change. The WRF results thus have a low sensitivity to the land parameters (with only the roughness length showing some impact). This calls for reassessing the land surface response on post-landfall characteristics with more detailed land surface representation within the mesoscale and hurricane modeling systems.     

Multidecadal variability of summer temperature over Romania and its relation with Atlantic Multidecadal Oscillation

We investigate the multidecadal variability of summer temperature over Romania as measured at 14 meteorological stations with long-term observational records. The dominant pattern of summer temperature variability has a monopolar structure and shows pronounced multidecadal variations. A correlation analysis reveals that these multidecadal variations are related with multidecadal variations in the frequency of four daily atmospheric circulation patterns from the North Atlantic region. It is found that on multidecadal time scales, negative summer mean temperature (TT) anomalies are associated with positive sea level pressure (SLP) anomalies centered over the northern part of the Atlantic Ocean and Scandinavia and negative SLP anomalies centered over the northern part of Africa. It is speculated that a possible cause of multidecadal fluctuations in the frequency of these four patterns are the sea surface temperature (SST) anomalies associated to the Atlantic Multidecadal Oscillation (AMO). These results have implications for predicting the evolution of summer temperature over Romania on multidecadal time scales.     

Public understanding of climate change terminology

Climatic Change - The UK, like other countries, has seen a proliferation of declarations of local climate emergencies. While these declarations have been interpreted as a demonstration of ambition,...     

Variational elastic solution for axially loaded piles in multilayered soil

Most analytical or semi‐analytical solutions of the problem of load‐settlement response of axially loaded piles are based on the assumption of zero radial displacement. These solutions also are only applicable to piles embedded in either a homogeneous or a Gibson soil deposit. In reality, soil deposits consist of multiple soil layers with different properties, and displacements in the radial direction within the soil deposit are not zero when the pile is loaded axially. In this paper, we present a load‐settlement analysis applicable to a pile with circular cross section installed in multilayered elastic soil that accounts for both vertical and radial soil displacements. The analysis follows from the solution of the differential equations governing the displacements of the pile–soil system obtained using variational principles. The input parameters needed for the analysis are the pile geometry and the elastic constants of the soil and pile. We compare the results from the present analysis with those of an analytical solution that considers only vertical soil displacements. The analysis presented in this paper also provides useful insights into the displacement and strain fields around axially loaded piles. Copyright © 2011 John Wiley & Sons, Ltd.     

Interaction of Ribbed-Metal-Strip Reinforcement with Tire Shred–Sand Mixtures

There is a pressing need of finding innovative and beneficial ways of using scrap tires in the construction of various geotechnical structures because a large number of waste tires are generated and discarded every year throughout the world. One example of such geotechnical application is the use of tire shreds mixed with soil as a backfill material for mechanically stabilized earth (MSE) walls. In this paper, we report the results of laboratory pullout tests performed to study the interaction between ribbed-metal-strip reinforcement and tire shred–sand mixtures prepared with various tire shred sizes (9.5 mm in nominal size, 50–100 mm in length, and 100–200 mm in length) and tire shred-to-sand mixing ratios (tire shred contents of 0, 12, 25, 100% by weight). The pullout capacities of ribbed metal strips embedded in tire shred–sand mixtures were obtained for three confining pressures (40, 65, and 90 kPa). The test results showed that the pullout capacity of ribbed metal strips embedded in tire shred–sand mixtures is much higher than that of ribbed metal strips embedded in samples prepared with only tire shreds. Based on the laboratory pullout test results, an equation was developed that can be used to estimate the pullout capacity of ribbed metal strips embedded in tire shred–sand mixtures if the tire shred size, compacted unit weight of the mixture, mean particle size of sand, and vertical effective stress acting at the interface are known.     

Quantification of displacement and particle crushing around a penetrometer tip

Particle crushing occurs near the tip of a penetrometer and influences the development of the tip resistance.To study particle crushing near a penetrometer tip,a cone penetrometer was monotonically jacked and then load-tested in medium dense and dense silica sand samples prepared in a halfcylindrical calibration chamber with viewing windows.During the tests,images of the advancing penetrometer and the surrounding soil were taken using digital cameras and analyzed to obtain the displacement and strain fields around the penetrometer using the Digital Image Correlation(DIC)technique.Subsequently,soil samples were collected near the tip of the penetrometer using a novel agarimpregnation technique and digitized using an X-ray microscope.The digitized samples were analyzed to reconstruct the three-dimensional models of individual particles,generating the gradation and relative breakage parameters of the sand around the cone penetrometer.     

A conceptual and numerical model for groundwater management: a case study on a coastal aquifer in southern Tuscany, Italy

Ongoing hydrogeological research aims to develop a correct management model for the Plio-Pleistocene multi-aquifer system of the Albegna River coastal plain (southern Tuscany, Italy); overexploitation of this aquifer for irrigation and tourism has caused seawater intrusion. The conceptual model is based on field and laboratory data collected during the 1995–2003 period. Meteoric infiltration and flows from the adjoining carbonate aquifer recharge the aquifer. Natural outflow occurs through a diffuse flow into the sea and river; artificial outflow occurs through intensive extraction of groundwater from wells. Water exchanges in the aquifer occur naturally (leakage, closing of aquitard) and artificially (multiscreened wells). The aquifer was represented by a three-dimensional finite element model using the FEFLOW numerical code. The model was calibrated for steady-state and transient conditions by matching computed and measured piezometric levels (February 1995–February 1996). The model helped establish that seawater intrusion is essentially due to withdrawals near the coast during the irrigation season and that it occurs above all in the Osa-Albegna sector, as well as along the river that at times feeds the aquifer. The effects of hypothetical aquifer exploitation were assessed in terms of water budget and hydraulic head evolution.