DSpace collection: 期刊論文

Yangtze River floods enhance coastal ocean phytoplankton biomass and potential fish production

title: Yangtze River floods enhance coastal ocean phytoplankton biomass and potential fish production abstract: The occurrence of extreme weather conditions appears on the rise under current climate change conditions, resulting in more frequent and severe floods. The devastating floods in southern China in 2010 and eastern Australia 2010-2011, serve as a solemn testimony to that notion. Accompanying the excess runoffs, elevated amount of terrigenous materials, including nutrients for microalgae, are discharged to the coastal ocean. However, how these floods and the materials they carry affect the coastal ocean ecosystem is still poorly understood. Yangtze River (aka Changjiang), which is the largest river in the Eurasian continent, flows eastward and empties into the East China Sea. Since the early twentieth century, serious overflows of the Changjiang have occurred four times. During the two most recent ones in July 1998 and 2010, we found total primary production in the East China Sea reaching 147 x 10(3) tons carbon per day, which may support fisheries catch as high as 410 x 10(3) tons per month, about triple the amount during non-flooding periods based on direct field oceanographic observations. As the frequencies of floods increase world wide as a result of climate change, the flood-induced biological production could be a silver lining to the hydrological hazards and human and property losses inflicted by excessive precipitations. Citation: Gong, G.-C., et al. (2011), Yangtze River floods enhance coastal ocean phytoplankton biomass and potential fish production, Geophys. Res. Lett., 38, L13603, doi:10.1029/2011GL047519.

Tropical Cyclone-like Vortices Detection in the NCEP 16-Day Ensemble System over the Western North Pacific in 2008: Application and Forecast Evaluation

title: Tropical Cyclone-like Vortices Detection in the NCEP 16-Day Ensemble System over the Western North Pacific in 2008: Application and Forecast Evaluation abstract: An automated technique has been developed for the detection and tracking of tropical cyclone like vortices (TCLVs) in numerical weather prediction models, and especially for ensemble-based models. A TCLV is detected in the model grid when selected dynamic and thermodynamic fields meet specified criteria. A backward-and-forward extension from the mature stage of the track is utilized to complete the track. In addition, a fuzzy logic approach is utilized to calculate the TCLV fuzzy combined-likelihood value (TFCV) for representing the TCLV characteristics in the ensemble forecast outputs. The primary objective of the TCLV tracking and TFCV maps is for use as an evaluation tool for the operational forecasters. It is demonstrated that this algorithm efficiently extracts western North Pacific TCLV information from the vast amount of ensemble data from the NCEP Global Ensemble Forecast System (GEFS). The predictability of typhoon formation and activity during June December 2008 is also evaluated. The TCLV track numbers and TFCV averages around the formation locations during the 0-96-h period are more skillful than for the 102-384-h forecasts. Compared to weak tropical cyclones (TCs; maximum intensity <= 50 kt), the storms that eventually become stronger TCs do have larger TFCVs. Depending on the specified domain size and the ensemble track numbers to define a forecast event, some skill is indicated in predicting the named TC activity. Although this evaluation with the 2008 typhoon season indicates some potential, an evaluation with a larger sample is necessary to statistically verify the reliability of the GEFS forecasts.

Trace metal cycling in the deep water of the South China Sea: The composition, sources, and fluxes of sinking particles

title: Trace metal cycling in the deep water of the South China Sea: The composition, sources, and fluxes of sinking particles abstract: Moored sediment traps were deployed for 1 yr at depths of 120, 600, and 3500 m in the water column to investigate the trace metal (M) (Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) composition, sources, and fluxes of deep-water sinking particles. Vertical transport for most of the metals at 120 m was strongly associated with organic matter production, and the major part of many of the metals in the sinking particles was of anthropogenic origin. Although the lithogenic fraction in deeper waters greatly increased with depth, significant proportions of the nonlithogenic and nonintracellular fractions were still observed when using M: Al or M: P ratios as indicators, particularly for Zn, Cu, Ni, Co, and Mn. Because particles from horizontal transport and sediment resuspension are known to be lithogenic in the deep basin, the trace metals in sinking particles in the twilight zone and deep water, which feature significantly elevated M: Al ratios, originate from the downward transport of anthropogenic or authigenic origins. With increasing inputs from anthropogenic aerosols over large oceanic regions globally, the coupling and transport of some trace metals originating from anthropogenic aerosols, such as Zn, Cu, Co, and Ni, with sinking organic particles has become an important pathway for trace metal cycling not only in the euphotic zone, but also in the twilight zone and deeper waters.

The formation and breaching of a short-lived landslide dam at Hsiaolin Village, Taiwan - Part II: Simulation of debris flow with landslide dam breach

title: The formation and breaching of a short-lived landslide dam at Hsiaolin Village, Taiwan - Part II: Simulation of debris flow with landslide dam breach abstract: Typhoon Morakot (2009) caused serious damage in southern Taiwan due to intensive rainfall with long duration. The issue of greatest concern arising from the disasters brought about by this extreme event was the burying of the entire village of Hsiaolin by a massive debris flow and landslide. Based on seismological and near-surface magnetic data, this tragic scenario arose due to a combination of events, a massive landslide, the formation of a landslide dam, and the consequent debris flow when this dam was breached. The objective of this part of the study is to investigate the spatial and temporal characteristics of the debris flow induced by the landslide breach. The US National Weather Service BREACH model and the Federal Emergency Management Agency approved FLO-2D model are integrated to facilitate the investigation of this catastrophe. A series of simulations including a 2D rainfall-runoff simulation over the Cishan River basin, landslide dam breach routing, and 2D debris flow simulation around the Hsiaolin Village were conducted. Hydraulic calculations were performed to determine the equivalent top elevation of the landslide dam based on inflows computed from the 2D rainfall-runoff simulation in association with the Digital Terrain Model (DIM) and upstream constraint of the backwater inundation areas. The hydrograph of the upstream inflow which induced overtopping failure was provided by a 2D rainfall-runoff simulation using the FLO-2D model calibrated by comparison with the downstream discharge record. The longevity of the landslide dam was less than 1 h, and it took only about 8 minutes to completely breach. The peak discharge rate of this massive landslide dam breach was 70,649 m(3)/s. The dam break hydrograph was then used for upstream inflow to drive the FLO-2D debris flow simulation. The average sediment concentration by volume was 0.362. The simulated deposited sediment depth showed a reasonable match to the differences of DTMs before and after the disaster. (C) 2011 Elsevier B.V. All rights reserved.