A NEW RECEPTOR MODEL:A DIRECT TRILINEAR DECOMPOSITION FOLLOWED BY A MATRIX RECONSTRUCTION

In many cases,monitoring data for ambient airborne particles can be organized in the form of a three-way data table with one way for chemical species,one for sampling periods and one for sites.A directtrilinear decomposition followed by a matrix reconstruction(DTDMR)is developed to analyze such adata table as a whole.The three-way data set is composed into three two-way matrices by a direct trilineardecomposition(DTD).The column vectors of each of the matrices are called‘source profiles’,‘emissionpatterns’and‘site coefficients’respectively.Particulate sources are identified by examining both theirsource profiles and emission patterns.After the sources have been identified,emission patterns and sitecoefficients are used to produce a three-way matrix that gives estimates of mass contributions of sourcesto the samples collected at every site in every period.By simulation study,not only has the method beenverified,but a good indicator has been found that shows the number of factors(i.e.sources)in thesystem.Unlike other receptor models,DTDMR does not require source profile data and does not involvetrial-and-error procedures.Since DTDMR identifies sources based on variations in two dimensions,it hasa higher potential to distinguish two sources that have similar chemical compositions.The DTDMRmodel has provided excellent results with simulated data and has been applied in a real world three-waydata set.     

Trace fossils from proglacial lake sediments

Trace fossils have been discovered in Middle Pleistocene proglacial lake sediments from St. Albans, Hertfordshire, England. They indicate that this environment was capable of supporting a variety of benthonic animals. The fossils are described and tentatively assigned to several invertebrate groups.     

Fine structure of a Greenland reverse tip jet: a numerical simulation

Reverse tip jets are strong low-level winds with easterly component that form near the southern tip of Greenland. In the present study, a reverse tip jet case which occurred from 21 to 22 December 2000 was examined to clarify its fine structure using a numerical model with a horizontal resolution of 3 km. The reverse tip jet, showing the supergeostrophic wind speed with a maximum wind speed in excess of 45 m s⁻¹, extended from the east coast of Greenland to the west of Cape Farewell with anticyclonic curvature. A cloud free region coincided with the jet indicated that there was a mesoscale downdraft. Along the eastern edge of the jet, a banded cloud formed between the upstream easterly wind and the colder northerly wind that is a part of the jet and is located along the east coast. This cloud was associated with large gradients in surface wind speed, temperature, moisture, and heat flux. A maximum surface total heat flux of 300 W m⁻² coincided with the location of the jet. It is suggested that the orographic deflection by Greenland's large-scale topography as well as small-scale downslope winds behind mountains with fiords causes the reverse tip jet.     

Quaternary chronostratigraphy: the nomenclature of terrestrial sequences

There is a long-standing tradition of dividing Quaternary stratigraphical sequences on the basis of climate. This climatostratigraphical approach, begun on terrestrial sequences in the last century, led to the widespread adoption of glacial, interglacial, stadial and interstadial subdivisions as standard. However, the limitations of the approach resulted in its replacement by local sequences of chronostratigraphical stages from the 1950s. The subsequent establishment of the detail and complexity of ocean-core sequences has encouraged increasing use of the terminology developed for these records to the terrestrial and shallow marine succession. The view is expressed that it is advisable to separate and retain regional chronostratigraphies for each sequence-type, and that these should be correlated using event-based stratigraphy where possible. This should ensure both the highest precision and lack of ambiguity and a securely-based synthesis of the relations between the terrestrial and ocean isotope sequences, a synthesis which is fundamental to understanding the nature and detail of regional and global climate change.     

Binary interactions between polar lows

In this study, the movement of polar lows is addressed from a novel and perspicuous viewpoint. The usual assumption has been that these mesoscale systems are, to a first approximation, advected by the larger scale flow in which they are embedded. However, when there are two or more polar lows in the same vicinity, binary interactions between pairs of polar lows can cause a cyclonic co-rotation of the pair. In geographic coordinates these interactions can appear as unusual loops, twists and turns in the low tracks, due to the interplay between the cyclonic co-rotation and the translation of the binary pair by the ambient flow. However when the tracks are replotted in centroid relative coordinates, a mutual rotation is unmistakable. Satellite imagery from several case studies has been examined to accurately determine the polar low tracks, and thus the co-rotations. Using surface wind observations, a theoretical rotation rate can be estimated, based on barotropic vortex dynamics. There is a good correspondence between the observed and calculated rotation rates. Recognizing the existence of binary interactions between polar lows emphasises the connection between polar lows and tropical cyclones, where binary interactions have been described in several studies. Indeed, in the cases studied here, binary interactions are strongest during the secondary (convective) stage of polar low development where the lows are somewhat analogous to arctic hurricanes.