The Fraser River is the source of most particulate matter in the Strait of Georgia, and its dispersal is modulated by the Fraser’s plume. Here we examine the plume’s shape, location, and area, and the variation of these parameters with changes in wind and river forcing by examining a 13-year time series of Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery for the concentration of suspended particulate matter (SPM). Plume shape and its variations are quantified by dividing the 904 images in this time series into subsets showing conditions under specified wind and river flow conditions and forming a composite image for each subset. Quantitative analysis of scalar quantities like plume area and mean plume SPM are based on calculated values for all individual images. The plume area increases linearly with river flow, changing by a factor of 10 between lowest and highest flows. Mean plume SPM also changes with flow but only by a factor of two. The surface area of the plume is almost completely unaffected by wind conditions. Plume location, however, is very sensitive to both wind speed and direction. It can reach across the Strait at highest river flows and is advected either northwest or southeast along the Strait in the same direction as winds on daily time scales. We also estimate the residence time of sediment in the plume to be only a few days, allowing the plume itself to reshape rapidly over short time scales in response to weather conditions. 相似文献
This study investigated the changes of high temperature events during important growing period of rice (graining filling to maturity) of 2021-2050 due to climate change. Future climate scenarios were HadGEM2-ES simulation with RCP2.6 and RCP8.5 emission pathways. Relationship between high temperature and yield change was established from historical weather and field observations during 1981-2009 period. The impacts of high temperatures on China’s rice production up to 2050 were assessed by applying deduced regression models to climate scenarios. Key messages drawn from this exercise include: ①High temperature event exhibited gradual increase from 2021 to 2050 under both RCP2.6 and RCP8.5 scenarios, characterized by increased number of high temperature days (HSD), rising accumulated temperature with Tmax greater than 35 ℃ (HDD), and increased lasting days of high temperature (CHD). The HSD and HDD increased substantially in double rice cropping system of South China, single rice cropping system of Yangtze River Basin and rice area of Northeast China. ②High temperature hotspot was located near the border between Hunan and Hubei during 1961-2000, and might move towards northeast in the period of 2021-2050. ③Except the Northeast, China’s rice production suffered most from increased HDD during grain filling to maturity, indicated by significant negative and linear relationship between yield and HDD, whereas rice in Northeast China was subject to the increase of SDD during grain filling to maturity, with a significant and quadratic relationship between the yield and SDD. ④Compared to the high temperature risks during 1961-1990, climate change would increase the risks in majority of the rice area, especially in Hubei and Anhui-the central portion of Yangtze River Basin rice area, Guangdong, Guangxi and Hainan-south China double rice area, and south part of Northeast China single rice area. 相似文献
In order to unravel the tectonic evolution of the north-central sector of the Sicily Channel (Central Mediterranean), a seismo-stratigraphic analysis of single- and multi-channel seismic reflection profiles has been carried out. This allowed to identify, between 20 and 50 km offshore the central-southern coast of Sicily, a ~80-km-long deformation belt, characterized by a set of WNW–ESE to NW–SE fault segments showing a poly-phasic activity. Within this belt, we observed: i) Miocene normal faults reactivated during Zanclean–Piacenzian time by dextral strike-slip motion, as a consequence of the Africa–Europe convergence; ii) releasing and restraining bend geometries forming well-developed pull-apart basins and compressive structures. In the central and western sectors of the belt, we identified local transpressional reactivations of Piacenzian time, attested by well-defined compressive features like push-up structures and fault-bend anticlines. The reconstruction of timing and style of tectonic deformation suggest a strike-slip reactivation of inherited normal faults and the local subsequent positive tectonic inversion, often documented along oblique thrust ramps. This pattern represents a key for an improved knowledge of the structural style of foreland fold-and-thrust belts propagating in a preexisting extensional domain. With regard to active tectonics and seismic hazards, recent GPS data and local seismicity events suggest that this deformation process could be still active and accomplished through deep-buried structures; moreover, several normal faults showing moderate displacements have been identified on top of the Madrepore Bank and Malta High, offsetting the Late Quaternary deposits. Finally, inside the northern part of the Gela Basin, multiple slope failures, originated during Pleistocene by the further advancing of the Gela Nappe, reveal tectonically induced potential instability processes.
