Damaging Weather Conditions in the United States: A Selection of Data Quality and Monitoring Issues

The limitations of observational data available for the study of damaging weather conditions (e.g., storms and extreme temperature events) are discussed. Crop and property insurance loss records are advocated as a potential supplement to traditional weather observations, as they integrate specific information about the spatial dimension of damaging weather conditions and the cost of damage they cause. Insurance loss data may also be analyzed in combination with meteorological data sets to derive indicator variables for the detection of damaging weather events.Two sets of insurance data are described. One record provides adjusted property losses associated with "catastrophic" weather events since 1949, and the other is an index of the amount of crop-hail losses per year since 1948. Additionally, an example of the benefits of the combination of insurance and meteorological data is presented through a selection of results from a recent study of freezing temperatures in the southeastern United States and associated insurance claims related to pipe bursting.If insurance data are to be applied in the future in similar studies of damaging weather conditions, it is essential that the insurance industry continues to collect and adjust loss data and periodically confirm that adjustment factors are temporally consistent.     

Structural identification in the frequency domain from earthquake records

A method has been developed to identify the parameters of the lower modes of a linear, time-invariant model of a structure from its recorded earthquake response. The identification is performed by selecting the parameters to obtain a least squares fit over a specified frequency band between the unsmoothed, complex-valued finite Fourier transform of the recorded acceleration response and the corresponding transform calculated from the response of the model. By including the effects of the initial and final conditions in the analysis, only a portion of the recorded excitation and response acceleration histories need be considered. The method is demonstrated first by an application to generated test data, and then to measured earthquake response.     

Pore water testing and analysis: the good,the bad,and the ugly

The increasingly common practice of collecting and assessing sediment pore water as a primary measure of sediment quality is reviewed. Good features of this practice include: pore water is a key exposure route for some organisms associated with sediments; pore water testing eliminates particle size effects; pore water analyses and tests can provide useful information regarding contamination and pollution. Bad features include: pore water is not the only exposure route; pore water tests lack chemical or biological realism: their "sensitivity" relative to other tests may be meaningless due to manipulation and laboratory artifacts; many sediment and surface dwelling organisms are not directly influenced by pore water. Bad features can become ugly if: other exposure pathways are not considered (for toxicity or bioaccumulation); manipulation techniques are not appropriate; pore water tests are inappropriately linked to population-level effects. Pore water testing and analyses can be effective tools provided their limitations are well understood by researchers and managers.     

Holocene climatic change in Morocco: a quantitative reconstruction from pollen data

 Annual precipitation, July and January temperatures were reconstructed from a continuous Holocene pollen sequence from the Middle Atlas, Morocco, using the best modern analogues method. The reconstructions show a clear difference between the early and late Holocene: from ∼10 ka to ∼6.5 ka the climate was drier and warmer than during the period since 6.5 ka. The average value of annual precipitation was ∼870 mm until 6.5 ka, then rose to ∼940 mm. Between 10 ka and 6.5 ka January and July temperatures were about 4 °C higher than the present. Both temperatures show a marked decrease between 7 ka and 6 ka. After 6.5 ka July and January temperatures fluctuated between 21 and 23 °C, and 2.5 and 5 °C respectively. January temperatures show a period of intermediate values (∼3.5 °C) between 4 ka and 5.5 ka. The reconstructed climate values generally match palaeolimnological data from the same core, which show five intervals of low lake level during the Holocene. They are also consistent with regional-scale COHMAP simulated palaeoclimate that shows contrasting patterns of rainfall variation between the northwesternmost part of Africa and the intertropical band. Received: 7 July 1997 / Accepted: 28 May 1998     

A model for tectonic rotations about a vertical axis

The rotation of a rigid ellipsoidal inclusion within a highly viscous fluid, orientated so that two of the principal axes remain horizontal, is used as a model for the rotation of crustal inclusions in wide zones of continental deformation. This model is also applicable to other geological problems involving the rotation of inclusions in a matrix. The pattern of behaviour in such a model is shown to be complex. In general the rotation rate of the inclusion is a function of all components of the velocity field of the deforming medium and the horizontal aspect ratio of the inclusion. However, for a given velocity field, this aspect ratio must exceed a critical value before the inclusion can rotate continuously. Inclusions with lower aspect ratios will rotate, for a certain range of orientations, in an opposite direction to the sense of shear in the deforming zone. The possibility of the inclusion changing shape during rotation adds to the complexity of behaviour.     

Phase relations in the CH4-H2O-NaCl system at 2 kbar, 300 to 600°C as determined using synthetic fluid inclusions

Synthesis of fluid inclusions in the CH₄-H₂O-NaCl system was accomplished by subjecting fractured quartz or fluorite, along with known quantities of CH₄, H₂O, and NaCl, to a pressure of 2 kbar and temperatures of 300, 400, 500, or 600°C, in sealed Au capsules. Under the elevated P-T conditions, some of the fractures healed, trapping fluids as inclusions. Microthermometric measurements conducted on the fluid inclusions show that at 2 kbar and 400 to 600°C, there are very broad regions of fluid unmixing in the CH₄-H₂O-NaCl system. For those bulk fluid compositions that lie in the two-phase (i.e., immiscible fluids) field, the high-density phase is enriched in NaCl, whereas the low-density phase is enriched in CH₄. For any given bulk composition, the degree of NaCl enrichment in the high-density phase increases, whereas the degree of CH₄ enrichment in the low-density phase decreases, as temperature increases from 400 to 600°C. Our experimental constraints on the size of the two-phase field are generally consistent with results generated using the equation-of-state GEOFLUIDS (available at http://geotherm.ucsd.edu/geofluids/). However, when comparing the compositions of coexisting immiscible fluids, as determined experimentally vs. calculated using GEOFLUIDS, we find that some relatively small but probably significant differences exist between our experiments and this equation of state.