Decreasing Trend of Western North Pacific Tropical Cyclone Inner-Core Size over the Past Decades     

Hanrui SHOU  Tim LI  Yuan SUN  Lu WANG  Jia LIU 《Journal of Meteorological Research》2021,35(4):635-645

Studies on tropical cyclone(TC) inner-core size have become increasingly active in recent years. However, few studies have investigated the trend of TC inner-core size. Here, we introduce a new index to measure TC inner-core size and calculate the observed trend. This index can greatly reduce the influence of data heterogeneity and uncertainty. It also considers public concern because the new index is mainly determined by the inner-core size of strong TCs, which attract more public attention than weak TCs. The results show that in the past decades, TC inner-core size has a significant downtrend that is significant above the 99% confidence level when the new index is used. We also show that this trend is probably related to the increase in TC intensity and relatively small inner-core size of strong TCs. Moreover, relative sea surface temperature(SST) is assumed to make contributions to the downtrend of TC inner-core size, which has a significant negative correlation with the new index.  相似文献   

A detailed isotopic and petrological study of a single garnet from the Gassetts Schist,Vermont   总被引：13，自引：1，他引：12  

Derek Vance  Tim Holland 《Contributions to Mineralogy and Petrology》1993,114(1):101-118

Garnets, up to 1.2 cm across, from a metapelite in the Acadian metamorphic terrain of eastern Vermont have been analysed for major elements and segregated into different fractions for isotopic analysis. The garnets preserve abundant inclusions of minerals present during garnet growth which allow a nearly complete reaction history to be established. The Sm-Nd and U-Pb isotopic analyses yield concordant ages of 380 Ma for the rim of one garnet and this is interpreted as the formation age. The changing mineral assemblages through garnet growth, their evolving compositions and the thermodynamic dataset of Holland and Powell (1990) are used to put constraints on the P-T evolution during growth. These imply growth during heating from 540 to 635° C and decompression from 9.7 to 7.2 kbar, representing a temperature increase of 95° C and an uplift of 7 km during growth of the garnet. While growth during heating and decompression is consistent with both field evidence and analysis of garnet microstructures and is predicted by theoretical models of regional metamorphism, the extent of the temperature increase requires either very slow uplift (0.15 mm a^-1) or an additional magmatic heat input. Slow uplift is precluded by existing constraints on both the duration of the uplift event and that of garnet growth and it is concluded that an external magmatic heat input is required. Comparison with published data on the timing of metamorphism in other parts of the terrain suggests that the peak occurred earlier in lower grade regions, a conclusion that is again supported by theoretical studies. Following the peak, cooling and uplift occurred at a modest rate consistent with simple isostatic recovery.  相似文献   

Isograds in internally buffered systems without solid solutions: principles and examples     

Judy Baker  Tim Holland  Roger Powell 《Contributions to Mineralogy and Petrology》1991,106(2):170-182

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A Case Study of Carbon Pools Under Three Different Land-Uses in Panamá     

Catherine Potvin  Edward Whidden  Tim Moore 《Climatic change》2004,67(2-3):291-307

This paper examines changes in carbon (C) pools associated with land-use, synthesizing data from two experiments dealing with different aspects of tree plantation establishment in Central Panamá. First, we analysed soil profiles in a grazed pasture and an adjacent 5-year-old teak (Tectona grandis) plantation. There were small differences in soil C mass in the top 10 cm of the pasture and the plantation, though analysis of paired profiles suggested larger differences at greater depth. Analysis of the ¹³C signatures in the pasture soils and litter showed that 90% to 95% of the organic matter in the surface 5 cm was derived from C₄ pasture plants, over the 45 years since the pasture was converted from forest. Comparison of the ¹³C signatures in the pasture and teak plantation profiles indicated substantial replacement of C₄—derived organic matter with the dominantly C₃—derived plantation tissues. Organic matter turnover times in the upper 10 cm of the soils ranged from 8 to 34 years and from 11 to 58 years in the upper 30 cm, depending on topographic location. We also present preliminary results, and technical challenges, for an eddy covariance experiment set up to provide a direct comparison between a grazed pasture and a native tree plantation. The two ecosystems studied are estimated to be small CO₂ sinks, 92 g,C,m^–2 yr^–1 for the pasture, and 57 g,C,m^–2 yr^–1 for native species plantation in the first year after establishment. The pastures response to seasonal change was more pronounced, both in term of CO₂ fluxes and in term of herbaceous productivity, than the plantations response. The storage below ground systems contained up 40% of the total sapling biomass.  相似文献   

Mass flow sedimentology within the HYC Zn–Pb–Ag deposit,Northern Territory,Australia: evidence for syn-sedimentary ore genesis     

Tim?IrelandEmail author  Stuart?W.?Bull  Ross?R.?Large 《Mineralium Deposita》2004,39(2):143-158

Laterally continuous mass-flow deposits are an important feature of the HYC stratiform sediment-hosted Zn–Pb–Ag deposit, which reveal more about the HYC mineralising system than has been previously recognised. Mass flow deposits are interbedded with sheet-like mineralised lenses in a carbonaceous dolomitic siltstone host rock. Sedimentological processes of mass-flow deposit emplacement are proposed that constrain stratiform mineralisation to the top metre of the sediment pile, based on mass-flow geometry and detailed clast petrology. Four distinct sedimentary facies are identified within the mass-flow units: framework-supported polymictic boulder breccia; matrix-supported pebble breccia; and gravel-rich and sand-rich graded turbidite beds. The boulder breccias are weakly reverse graded and show rapid lateral transition into the other facies, all of which are distal manifestations of the same sedimentary events. The flow geometry and relationships between these facies are interpreted to reflect mass-flow initiation as clast-rich debris flows, with transformation via the elutriation of fines into a subsequent turbulent flow from which the turbidite and matrix-supported breccia facies were deposited. All the mass-flow facies contain clasts of the common and minor components of the in-situ laminated base-metal mineralised siltstone. Texturally these are identical to their in-situ counterparts, and are clearly distinct from other sulphidic clasts that are of unequivocal replacement origin. In the boulder breccias, intraclasts may be the dominant clast type and the matrix may contain abundant fine-grained sphalerite and pyrite. Dark coloured sphaleritic and pyritic breccia matrices are distinct from pale carbonate-siliclastic matrices, are associated with high abundance of sulphidic clasts, and systematically occupy the lower part of breccia units. Consequently, clasts that resemble in-situ ore facies are confirmed as genuine intraclasts that were incorporated into erosive mass flows prior to complete consolidation. Disaggregation and assimilation of sulphidic sediment in the flow contributed to the sulphide component of the dark breccia matrices. The presence of laminated sulphidic intraclasts in the mass-flow facies constrains mineralisation at HYC to the uppermost part of the seafloor sediment pile, where this material was susceptible to erosion by incoming clast-rich mass flows.Editorial handling: N. White  相似文献   

Diseases of gadoid fish in cultivation: a review   总被引：1，自引：1，他引：1  

Bricknell  Ian R.; Bron  James E.; Bowden  Tim J. 《ICES Journal of Marine Science》2006,63(2):253-266

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Environmental stewardship as a new form of fisheries governance     

Gray  Tim S.; Hatchard  Jenny 《ICES Journal of Marine Science》2007,64(4):786-792

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Lack of significant change in epiphyte biomass with increasing extent of measurement within seagrass meadows     

Tim N. Moore  Peter G. Fairweather 《Estuarine, Coastal and Shelf Science》2006,68(3-4):413

A significant consideration in defining patterns of ecological interest is determining at what spatial scales these patterns are apparent. We performed a mensurative experiment to determine the effect of how changing the extent of sampling, using a fixed grain (panning up), changed our measurements of seagrass epiphyte biomass at a variety of hierarchical spatial scales, ranging from approximately 0.1 m to 2.5 × 10⁵ m. The experiment was performed twice at two sets of nested locations, also capturing an element of seasonality within the spatial extents. While the two regions and their nested locations differed in terms of epiphyte biomass, and values did change over time, mean epiphyte values were invariant at the local scale. This indicates that at the local scale (≤100 m extent), we expect seagrass epiphyte biomass to be relatively homogenous. Contrary to theoretical predictions, we did not detect predictable changes in mean values of epiphyte biomass as sampling extent increased. The results of this study highlight the importance of recognizing the spatial dependence of patterns in heterogeneous environments.  相似文献   

Effect of PDOP on performance of Kalman Filters for GNSS-based space vehicle position estimation     

Biswas  Sanat K.  Qiao  Li  Dempster  Andrew G. 《GPS Solutions》2017,21(3):1379-1387

GPS Solutions - A theoretical performance analysis of Kalman Filters for Global Navigation Satellite System GNSS-based space vehicle position estimation in varying Position Dilution of Precision...  相似文献   

A special MJO event with a double Kelvin wave structure          下载免费PDF全文

Lili Zhu  Tim Li 《Acta Meteorologica Sinica》2017,31(2):295-308

The second Madden–Julian Oscillation (MJO) event during the field campaign of the Dynamics of the MJO/Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 (DYNAMO/CINDY2011) exhibi ted an unusual double rainband structure. Using a wavenumber-frequency spectral filtering method, we unveil that this double rainband structure arises primarily from the Kelvin wave component. The zonal phase speed of the double rainbands is about 7.9 degree per day in the equatorial Indian Ocean, being in the range of convectively coupled Kelvin wave phase speeds. The convection and circulation anomalies associated with the Kelvin wave component are characterized by two anomalous convective cells, with low-level westerly (easterly) and high (low) pressure anomalies to the west (east) of the convective centers, and opposite wind and pressure anomalies in the upper troposphere. Such a zonal wind–pressure phase relationship is consistent with the equatorial free-wave dynamics. While the free-atmospheric circulation was dominated by the first baroclinic mode vertical structure, moisture and vertical motion in the boundary layer led the convection.The convection and circulation structures derived based on the conventional MJO filter show a different characteristic. For example, the phase speed is slower (about 5.9 degree per day), and there were no double convective branches. This suggests that MJO generally involves multi-scales and it is incomplete to extract its signals by using the conventional filtering technique.  相似文献