Shin’ichiro Kako

Sequential monitoring of beach litter using webcams

This study attempts to establish a system for the sequential monitoring of beach litter using webcams placed at the Ookushi beach, Goto Islands, Japan, to establish the temporal variability in the quantities of beach litter every 90 min over a one and a half year period. The time series of the quantities of beach litter, computed by counting pixels with a greater lightness than a threshold value in photographs, shows that litter does not increase monotonically on the beach, but fluctuates mainly on a monthly time scale or less. To investigate what factors influence this variability, the time derivative of the quantity of beach litter is compared with satellite-derived wind speeds. It is found that the beach litter quantities vary largely with winds, but there may be other influencing factors.

Using aerial photography and in situ measurements to estimate the quantity of macro-litter on beaches.

This study has demonstrated a reliable method of quantifying the total mass of litter on a beach. It was conducted on Ookushi beach, Goto-Islands, Japan, and uses a combination of balloon-assisted aerial photography and in situ mass measurements. The total mass of litter over the beach was calculated to be 716±259kg. This figure was derived by multiplying the litter-covered area (calculated using balloon-assisted aerial photography) by the mass of litter per unit area. Light plastics such as polyethylene made up 55% of all plastic litter on the beach, although more work is needed to determine whether lighter plastics are transported to beaches more readily by winds and ocean currents compared with heavier plastics, or whether lighter plastics comprise a greater percentage of marine litter. Finally, the above estimates were used to calculate the total mass of metals released into coastal ecosystems via plastic litter on beaches.

Establishment of numerical beach-litter hindcast/forecast models: An application to Goto Islands, Japan

This study attempts to establish a system for hindcasting/forecasting the quantity of litter reaching a beach using an ocean circulation model, a two-way particle tracking model (PTM) to find litter sources, and an inverse method to compute litter outflows at each source. Twelve actual beach survey results, and satellite and forecasted wind data were also used. The quantity of beach litter was hindcasted/forecasted using a forward in-time PTM with the surface currents computed in the ocean circulation model driven by satellite-derived/forecasted wind data. Outflows obtained using the inverse method was given for each source in the model. The time series of the hindcasted/forecasted quantity of beach litter were found consistent with the quantity of beach litter determined from sequential webcam images of the actual beach. The accuracy of the model, however, is reduced drastically by intense winds such as typhoons which disturb drifting litter motion.

Two-Way Particle-Tracking Model for Specifying Sources of Drifting Objects: Application to the East China Sea Shelf

Abstract The two-way Lagrangian particle-tracking model (PTM) is proposed for specifying sources of objects drifting with random-walk processes on the sea surface. First, to determine object source candidates, modeled particles are released from the point (hereafter, “receptor”) where an observer finds the objects using a backward-in-time PTM with modeled ocean currents of which directions are reversed in sign. Second, the modeled particles are released from these source candidates in a forward-in-time PTM using ocean currents originally computed in hydrographic models. Third, the source candidates are considered to be reliable at a 5% significance level if the observed receptor is located inside the ellipse whose center is the mean position of the modeled particles at the time when the observer found the objects and whose axis length is twice the standard deviation computed using all modeled particle positions. The two-way PTM experiments are carried out in a realistic hydrographic model over the East Ch...

Low altitude remote-sensing method to monitor marine and beach litter of various colors using a balloon equipped with a digital camera.

This study aims to establish a low-altitude remote sensing system for surveying litter on a beach or the ocean using a remote-controlled digital camera suspended from a balloon filled with helium gas. The resultant images are processed to identify the litter using projective transformation method and color difference in the CIELUV color space. Low-altitude remote sensing experimental observations were conducted on two locations in Japan. Although the sizes of the litter and the areas covered are distorted in the original photographs taken at various angles and heights, the proposed image process system is capable of identifying object positions with a high degree of accuracy (1-3 m). Furthermore, the color difference approach in the CIELUV color space used in this study is well capable of extracting pixels of litter objects of various colors allowing us to estimate the number of objects from the photographs.

A new technique for detecting colored macro plastic debris on beaches using webcam images and CIELUV

We have developed a technique for detecting the pixels of colored macro plastic debris (plastic pixels) using photographs taken by a webcam installed on Sodenohama beach, Tobishima Island, Japan. The technique involves generating color references using a uniform color space (CIELUV) to detect plastic pixels and removing misdetected pixels by applying a composite image method. This technique demonstrated superior performance in terms of detecting plastic pixels of various colors compared to the previous method which used the lightness values in the CIELUV color space. We also obtained a 10-month time series of the quantity of plastic debris by combining a projective transformation with this technique. By sequential monitoring of plastic debris quantity using webcams, it is possible to clean up beaches systematically, to clarify the transportation processes of plastic debris in oceans and coastal seas and to estimate accumulation rates on beaches.

A decadal prediction of the quantity of plastic marine debris littered on beaches of the East Asian marginal seas

Large quantities of plastic litter are expected to wash ashore along the beaches of the East Asian marginal seas in the coming decade. Litter quantities were predicted using three techniques: a particle tracking model (PTM) used in conjunction with two-way PTM experiments designed to reveal litter sources, an inverse method used to compute litter outflows at each source, and a sequential monitoring system designed to monitor existing beach litter using webcams. Modeled year-to-year variation in litter quantities indicated that the amount of litter would continue to increase in the East Asian marginal seas if the level of outflow remains constant in the coming decade. The study confirms that about 3% of all East Asian beaches may potentially experience a 250-fold increase in the amount of plastic beach litter washed ashore in the next 10 years.

Atmosphere–Ocean Coupled Process along Coastal Areas of the Yellow and East China Seas in Winter

AbstractA regional atmosphere–ocean coupled model is developed, based on the Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model in conjunction with the Princeton Ocean Model, to investigate atmosphere–ocean coupled processes that might occur over the Yellow and East China Sea shelves in winter. To examine how the coupled processes actually work in the ocean, sea surface temperatures (SSTs) computed in both coupled and uncoupled models are compared with SSTs synthesized from multiple satellite observations. The results indicate that the coupled model significantly improves the negative SST bias in shallow waters around the Chinese coast produced by the uncoupled model. Cool and dry northerly winds from the Asian landmass reduce SST in these shallow waters through intensive upward heat loss. Thereafter, the horizontal gradient of sea level pressure (SLP) around the Chinese coast moderates because the land–ocean heat contrast weakens owing to the reduced SST in the coastal...

Ensemble numerical forecasts of the sporadic Kuroshio water intrusion (kyucho) into shelf and coastal waters

The finite volume coastal ocean model downscaling ocean reanalysis and forecast data provided by the Japan Coastal Ocean Predictability Experiment (JCOPE2) are used to forecast sudden Kuroshio water intrusion events (kyucho) induced by frontal waves amplified south of the Bungo Channel in 2010. Two-month hindcast computations give initial conditions of the following 3-month forecasts computations which consist of ten ensemble members. The temperature time series computed by these ten members are averaged to compare with that actually observed in the Bungo Channel, where sudden temperature rises related to kyucho events are remarkable in February, August, and September. Overall, the intense kyucho events actually observed in these months are predicted successfully. However, intense kyucho events are forecasted frequently during the period of May through June even though intense kyucho events are absent during this period in the actual ocean. It is suggested that the present downscaling forecast model requires reliable lateral boundary conditions provided by JCOPE2 data to which numerous Argo data are assimilated to enhance the accuracy. In addition, it seems likely that the model accuracy is reduced by small eddies moving along the shelf break.

A Role of the Yellow and East China Seas in the Development of Extratropical Cyclones in Winter

AbstractTo investigate whether the relatively warm Yellow and East China Seas play an active role in the deepening of extratropical cyclones over East Asia during winter, surface wind vectors downloaded from the Quick Scatterometer (QuikSCAT) website are used to compute the standard deviation of surface vorticity at ¼° resolution. In addition, a regional numerical atmospheric model is adopted to find atmospheric and/or oceanic conditions favorable for development of extratropical cyclones over the study area. These satellite-derived and modeled vorticity fields demonstrate that, on average, extratropical cyclone activity is moderate over the warm Yellow and East China Seas. This is because enhanced lower-level baroclinicity over these ocean areas is transferred as far as the shelf break of the East China Sea by strong northwesterly surface winds. Based on the numerical model results, the weak northwesterly surface wind condition is required for enhancing lower-level baroclinicity over the Yellow and East ...