Wind Wave Induced Sediment Resuspension In The Yellow River Mouth

Estuary and coastal regions are such regions that the interactions between land and sea are obvious and the sediment becomes big problem for human being. In the estuary and coastal environment, sediment resuspension is an import process, which makes influence on the sediment mass flux, secondary productivity, pollution dispersal and so on. The reasons that cause sediment resuspension are very complicated. Wave, which can enhance the bed turbulence and make the bottom shear stress increased, usually plays a key role in the sediment resuspension, especially in the shallow and micro-tidal area.Yellow River is famous for its high sediment concentration and it carries a huge amount of sediment into Bohai Sea. Recently, due to the global climate change and works on water conservancy facilities in the upstream of the river, the amount of sediment that Yellow River carried into Bohai Sea was reduced. Some deposition area near the estuary changed to be erosion area. It is very import to study the wind wave induced sediment resuspension in the Yellow River mouth.We applied a coupled model to the entire Bohai Sea with emphasis on the Yellow River month. This model couples with a regional ocean circulation model– ROMS (Regional Ocean Modeling System),? a third-generation wave model– SWAN (Simulation WAve Near shore), and a sediment transport model– CSTM (Comminute Sediment Transport Model). The model simulated the current, waves and sediment transport during winter season. Then the wind wave induced sediment resuspension in the area was analyzed.Seven stations around the Yellow River delta were selected. We compared the suspended sediment concentration affected by the wave induced resuspension effect and the suspended sediment concentration without the wave induced resuspension effect in these stations. Then we calculated the percentage of the wave induced resuspended sediment in that of the bottom layer of these stations. The percentage values of stations are various from 13.8% to 61.3%. In the three stations near the Yellow River mouth, wave resuspended more than 27% bottom sediment. The mean wind speed of the period that we analyzed is 6.3 ms^-1. The multi-year averaged wind speed in the Yellow River month is 5.3 ms^-1. Therefore, the wind wave induced resuspension is very import to the sediment transport in this area.Under the north wind condition, the highest concentration center of wave resuspended sediment occurred near the Gudong town. During the flood tide, the center is near the coastline. From Shenxiangou channel to the old Yellow River mouth, the concentrations of wave induced resuspended sediment are relatively high. During the ebb tide, the highest concentration center moves out of the coastline. From the old Yellow River mouth to the northeast of the Yellow River delta, the concentrations of wave induced resuspended sediment are relatively high. The global climate change has a strong tie with human being. The ocean plays a key role in the global climate change. Latent and sensible heat fluxes are import elements in the air-sea heat balance. The calculation of latent and sensible heat fluxes usually depends on the sea surface climate parameters such like wind speed, specific humidity and air temperature. In the past, it has been necessary to rely on in situ observations to get near surface specific humidity and air temperature. In situ observations are very sparse globally, even when many volunteer ship reports are included. However, with the advancement of remote sensing technology, various earth surface properties are observed by satellite, and the observations have high spatial and temporal resolution and cover most of the earth every few days. Because of the advances in satellite observations, the derivation of sea surface specific humidity and air temperature is made possible. The main objective of the present study is to retrieve sea surface specific humidity (Qa) and air temperature (Ta) from Advanced Microwave Scanning Radiometer for EOS (AMSR-E) measurements.A new multivariate regression formula for retrieving sea surface specific humidity from remote sensing data from AMSR-E is proposed. Daily and monthly specific humidity data from the National Center for Environmental Prediction (NCEP) reanalysis dataset and data of sea surface temperature, atmospheric total water vapor, and wind speed from AMSR-E oceanographic products were used to derive the regression coefficients of the formula and validate the formula. The root mean square (rms) error for daily retrieved Qa over the global oceans is 1.05 g kg^-1, and the rms error for monthly retrieved Qa is 0.61 g kg^-1.To overcome some disadvantage of multivariate regression method, a new method, Generalized Additive Models (GAMS), is proposed to derive instantaneous and monthly mean sea surface specific humidity. Instantaneous and monthly specific humidity data from the NCEP reanalysis dataset and AMSR-E oceanographic products are used for training the retrieval model and validating it. The rms error for instantaneous retrieved Qa over the global oceans is 1.41 g kg^-1, and the rms error for monthly retrieved Qa is 0.56 g kg^-1. Compared to the multivariate regression method, the rms of GAMs method retrieved Qa is smaller.The GAMs is also applied to retrieve the instantaneous and monthly mean sea surface air temperature. Instantaneous and monthly specific humidity data from the NCEP reanalysis dataset and AMSR-E oceanographic products are used to train the retrieval model and validate it. The rms error for instantaneous retrieved Ta over the global oceans is 1.20°C, and the rms error for monthly retrieved Ta is 0.66°C.