本短文给出了欧洲空间局发射的Sentinel-1卫星合成孔径雷达(SAR)于2014年10月4日在西北太平洋获取的第一幅台风图像. 高质量SAR图像显示了台风巴蓬(Phanfone)风眼形状和海洋表面风场. 我们同时给出了海洋表面风场的提取方法. 由于欧洲空间局尚没有发布计算风场所需要的、定标的雷达散射截面系数, 实际风场计算暂时无法完成. 本研究显示了Sentinel-1卫星SAR图像在研究台风引起的海洋表面小尺度现象的优势. 本文呼吁读者充分利用Sentinel-1卫星SAR图像, 因为这是民用SAR卫星有史以来, 第一次可以免费、公开地获取SAR图像.

Oceanic noise is the background interference in sonar performance prediction and evaluation at high sea states. Statistics of underwater ambient noise during Typhoons Soulik and Nida were analyzed on the basis of experimental measurements conducted in a deep area of the Philippine Sea and the South China Sea. Generated linear regression, frequency correlation matrix (FCM), Burr distribution and Gumbel distribution were described for the analysis of correlation with environmental parameters including wind speed (WS), significant wave height (SWH), and the inter-frequency relationship and probability density function of noise levels (NLs). When the typhoons were quite close to the receivers, the increment of NLs exceeded 10 dB. Whilst ambient noise was completely dominated by wind agitation, NLs were proportional to the cubic and quintic functions of WS and SWH, respectively. The fitted results between NLs and oceanic parameters were different for “before typhoon” and “after typhoon”. The fitted slopes of linear regression showed a linear relationship with the logarithm of frequency. The average observed typhoon-generated NLs were 5 dB lower than the Wenz curve at the same wind force due to the insufficiently developed sea state or the delay between NLs and WS. The cross-correlation coefficient of FCM, which can be utilized in the identification of noise sources in different bands, exceeded 0.8 at frequencies higher than 250 Hz. Furthermore, standard deviation increased with frequency. The kurtosis was equal to 3 at >400 Hz approximately. The characteristics of NLs showed good agreement with the results of FCM.

Many typhoons pass through the East China Sea (ECS) and the oceanic responses to typhoons on the ECS shelf are very energetic. However, these responses are not well studied because of the complicated background oceanic environment. The sea surface temperature (SST) response to a severe Typhoon Rananim in August 2004 on the ECS shelf was observed by the merged cloud-penetrating microwave and infrared SST data. The observed SST response shows an extensive SST cooling with a maximum cooling of 3°C on the ECS shelf and the SST cooling lags the typhoon by about one day. A numerical model is designed to simulate the oceanic responses to Rananim. The numerical model reasonably simulates the observed SST response and thereby provides a more comprehensive investigation on the oceanic temperature and current responses. The simulation shows that Rananim deepens the ocean mix layer by more than 10 m on the ECS shelf and causes a cooling in the whole mixed layer. Both upwelling and entrainment are responsible for the cooling. Rananim significantly deforms the background Taiwan Warm Current on the ECS shelf and generates strong Ekman current at the surface. After the typhoon disappears, the surface current rotates clockwise and vertically, the current is featured by near inertial oscillation with upward propagating phase.

The accuracy of typhoon forecasts plays an important role in the prediction of storm surges. The uncertainty of a typhoon’s intensity and track means it is necessary to use an ensemble model to predict typhoon storm surges. A hydrodynamic model, which is operational at the National Marine Environmental Forecasting Center, is applied to conduct surge simulations for South China coastal areas using the best track data with parametric wind and pressure models. The results agree well with tidal gauge observations. To improve the calculation efficiency, the hydrodynamic model is modified using CUDA Fortran. The calculation results are almost the same as those from the original model, but the calculation time is reduced by more than 99%. A total of 150 typhoon cases are generated by combining 50 typhoon tracks from the European Centre for Medium-Range Weather Forecasts with three possible typhoon intensity forecasts. The surge ensembles are computed by the improved hydrodynamic model. Based on the simulated storm surges for the different typhoon cases, ensemble and probability forecast products can be provided. The mean ensemble results and probability forecast products are shown to agree well with the observed storm surge caused by Typhoon Mangkhut. The improved model is highly suitable for ensemble numerical forecasts, providing better forecast products for decision-making, and can be easily implemented to run on regular workstations.

Water quality parameters such as pH,DO,COD,PO₄-P,SiO₃-Si,NO₂-N,NO₃-N in the Haikou Bay were monitored respectively before and after Typhoon 9618 occurring on Sep.18,1996.Based on the statistics of typhoon in the Haikou Bay and numerical calculation of stormy current,the mechanism of water quality variation caused by typhoon is discussed.The typhoon impact on the Haikou Bay usually appears between July and November,most usually between August and October.The monitoring results before a typhoon were different from that.The stormy wave and windstorm cur rent stir up the sediment in near-shore bottom and make the bottom water mix with the surface water strongly,specially windstorm current with strong velocity at the head of the bay stirs up higher pollu tants sediment near sea area of sewage outfall,and heavy rain with typhoon carries the pollutants from land through the Nandu River to the Haikou Bay,so the contents of COD,PO₄-P,NO₂-N,NO₃-N,SiO₃ after a typhoon are higher than those before.Windstorm current is violent,which makes offshore high DO water exchange more frequently with inner bay water and oxygen in the air dissolves in sea water faster,so DO content after typhoon is higher than that before typhoon.This strong action of water exchange also causes lower pH change before and after the typhoon.

By using the equations describing typhoons in the atmosphere,the steady three-dimensional stream field and the corresponding pressure and temperature fields are obtained. The three-dimensional velocity fields construct a nonlinear autonanous system in the physical space.It is shown that the center of typhoon is a local minimum pressure with positive vertical vorticity and horizontal convergence in lower levels and a local marumum pressure with negative vertical vorticity and horizontal divergence in the upper levels. Because there exist two saddle-focus points in the autonornous system,there exist the spiral patterns,in which the winds blow spinally in and out of the center in the lower and upper levels in the Northern Hanisphere and cause the ascending rrotion near the center and descending motion and the edge,respectively.All these are in fair oonfoxmity with the observations.It impVes that the rotation of earth and the visooaity of air play an important role in the spiral structure of typtxbns.

A typhoon leading is an important natural disaster to many disasters to China. A giant wave caused by it has brought large threat for an offshore project. Based on the maximum entropy principle, one new model which has 4 undetermined parameters is constructed, which is called the discrete maximum entropy probabilistic model. In practical applications, the design wave height is considered as soon as possible in a typhoon affected sea areas, the result fits the observed data well. Further more this model does not have the priority compared with other distributions as Poisson distribution. The model provides a theoretical basis for the engineering design more reasonable when considering typhoon factors comprehensively.

The MASNUM wave-tide-circulation coupled model, with 21 layers in the vertical and (1/8)°horizontal resolution, was employed to investigate the oceanic responses to Typhoon Mstsa which traversed the East China Sea (ECS) during the period of 4~6 August, 2005. Numerical experiment results are analyzed and compared with observation. The responses of the sea surface temperature (SST), in a focused area of (27°~29°N, 121°~124°E), include heating and cooling stages. The heating is mainly due to warm Kuroshio water transportation and downwelling due to the water accumulation. In the cooling stage, the amplitude of the simulated cold wake (~3℃), located on the right side of this typhoon track, is compared quite well with that of the satellite observed SST data. The wave-induced mixing(Bv) plays a key role for the SST cooling. Bv still plays a leading role, which accounts for 36%, for the ocean temperature drop in the upper ocean of 0~40 m, while the upwelling is responsible for 84% of the cooling for the lower layer of 40~70 m. The mixed layer depth (MLD) increased quickly from 28 to 50 m in the typhoon period. However, the simulated MLD without the wave-induced vertical mixing, evolution from 13 to 32 m, was seriously underestimated. The surface wave is too important to be ignored for the ocean responses to a typhoon.

通过对台风“米雷”登陆前后山东半岛东部8个滨海沙滩地形地貌的现场调查以及一年后的重复调查对比分析了沙滩地貌形态的变化,并依据台风期间的风要素计算和评估了台风期间沙滩的沿岸输沙和横向输沙趋势,探讨了在热带风暴发生频次较低的地区沙滩的风暴响应模式和海岸恢复规律。研究结果表明,台风造成横向和纵向输沙量的增加和输沙方向的逆转是造成沙滩形态改变的主要因素,而在米雷登陆前的阶段横向和纵向输沙作用最为强烈。研究区内沙滩的风暴响应模式主要表现为侵蚀陡坎的形成和滩肩或滩面的侵蚀后退。与其他台风频发的区域不同,在研究区台风是一个偶然的强动力事件,因此台风特征对沙滩的风暴响应的作用更加明显。而沙滩剖面形态的作用,仅仅在耗散型沙滩上有所体现。此外,沙滩的走向是控制风暴作用强度的主要因素,并且与沙滩风后恢复密切相关。

The role of wave breaking (WB) in the ocean dynamics in the Bohai Sea, China under typhoon condition is systematically investigated utilizing a coupled wave-current model. The influences of WB on ocean dynamics and processes (mixing coefficient, temperature, mixed layer depth, and current) during the entire typhoon period (including the pre-typhoon, during-typhoon and after-typhoon stages) are comprehensively detected and discussed. Experimental results show that WB greatly enhances the turbulent mixing at about top 10 m depth under typhoon condition, the increase can be up to 10 times that of the normal weather. At the same time, WB generally strengthens the sea surface cooling by ~1.2°C at the during-typhoon stage, about 3 times that in normal weather. The mixed layer depth, is rapidly increased by ~1.6–3.6 m during typhoon due to WB, particularly, the deepening is stronger in the region from 120.5°E to 121.0°E on account of close to the typhoon eye. In addition, WB renders the current speed more uniformly within the entire depth in the Bohai Sea, the change in speed is ~0.2 m/s, whereas the alternation in current vector is generally opposite to the wind direction except for the typhoon eye region, reflecting that WB has an inhibitory effect on the typhoon-forced current change. The effects of WB on vertical mixing coefficient response to the typhoon rapidly, while the impacts of WB on temperature, and mixed layer depth present hysteretic responses to typhoon. Finally, the mechanisms and distribution characteristics of WB-induced mixing and tidal mixing are compared under typhoon condition.