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Showing papers by "Quanan Zheng published in 2010"


Journal ArticleDOI
TL;DR: In this article, the impacts of preexisting mesoscale cyclonic eddies (PCEs) on successive enhanced sea surface cooling in response to the passage of Super Typhoon Hai-Tang in the western North Pacific in 2005, using numerical simulation methods.
Abstract: [1] This study examines the impacts of preexisting mesoscale cyclonic eddies (PCEs) on successive enhanced sea surface cooling in response to the passage of Super Typhoon Hai-Tang in the western North Pacific in 2005, using numerical simulation methods. We have done two numerical experiments: one with the presence of these PCEs resolved by the Hybrid Coordinate Ocean Model/Navy Coupled Ocean Data Assimilation system (EXPHYC) and another with World Ocean Atlas 2001 climatology as initial conditions (EXPWOA). The results show that the cooling response simulated by EXPWOA is only half of that simulated by EXPHYC, which is close to satellite observations. This suggests that an accurate representation of the upper dynamic conditions is required to estimate the sea surface cooling to a typhoon accurately. Subsequently, the effects of the PCEs on successive cooling response to most major typhoons are evaluated by conducting a systematical analysis with a focus on Category 5 typhoons occurring in the region from 2003 to 2008. Satellite altimeter sea surface height anomaly data and merged Tropical Rainfall Measuring Mission Microwave Imager/Advanced Microwave Scanning Radiometer for EOS microwave sea surface temperatures (SST) are used to characterize PCEs and cooling responses to those typhoons. The results identify the relationship between PCEs and successive enhanced SST cooling for most strong typhoons in the western North Pacific.

58 citations


Journal ArticleDOI
TL;DR: The Indonesian Throughflow (ITF) as discussed by the authors is a key component of global ocean circulation, and its magnitude and variability play an important role in determining heat and nutrient exchange to other ocean basins.
Abstract: Global ocean circulation is a primary mechanism for transporting energy and nutrients around the planet. At its most basic level, this circulation transports water from the Pacific Ocean through the Indonesian archipelago into the Indian Ocean; these waters join the Agulhas Current, which loops around Africa and in turn joins the Gulf Stream in the Atlantic Ocean. Upon reaching the North Atlantic, waters sink, creep south along the ocean floor as deep water, trace around Antarctica as bottom water, and move to the Pacific Ocean where they upwell, only to seep back into the Indian Ocean through the straits and channels surrounding Indonesia. The seepage of warm equatorial waters from the western Pacific Ocean into the Indian Ocean is called the Indonesian Throughflow (ITF). Long recognized as a key component of global ocean circulation, the ITF's magnitude and variability play an important role in determining heat and nutrient exchange to other ocean basins. Scientists' ability to estimate ITF behavior is therefore essential for understanding the global climate system.

39 citations


Journal ArticleDOI
TL;DR: An analytical model based on radar backscatter theory was utilized to retrieve sea surface wind speeds from C-band satellite synthetic aperture radar (SAR) data at either vertical (VV) or horizontal (HH) polarization in transmission and reception as mentioned in this paper.
Abstract: An analytical model based on radar backscatter theory was utilized to retrieve sea surface wind speeds from C-band satellite synthetic aperture radar (SAR) data at either vertical (VV) or horizontal (HH) polarization in transmission and reception. The wind speeds were estimated from several ENVISAT Advanced SAR (ASAR) images in Hong Kong coastal waters and from Radarsat-1 SAR images along the west coast of North America. To evaluate the accuracy of the analytical model, the estimated wind speeds were compared to coincident buoy measurements, as well as winds retrieved by C-band empirical algorithms (CMOD4, CMOD_IRF2 and CMOD5). The comparison shows that the accuracy of the analytical model is comparable to that of the C-band empirical algorithms. The results indicate the capability of the analytical model for sea surface wind speed retrieval from SAR images at both VV and HH polarization.

36 citations


Journal ArticleDOI
TL;DR: Li et al. as discussed by the authors analyzed the requirements for the generation and upward propagation of the disturbance induced by the current-bathymetry interaction in a 3-layer ocean using representative ocean density profile data and the GS current data.
Abstract: current (2 ms −1 ) and favorable ocean stratification. SAR image analysis shows the basic characteristics of these bathymetric features. A coincident sea surface temperature image shows that the bathymetric feature is only “visible” by SAR within the GS pathway. The dominant wavelength of the wave‐like feature is about 2.3 km and their crests are perpendicular to the GS axis. Shipboard sounding measurements confirm the SAR observation. A theoretical consideration of the ocean current and corrugated bathymetry interaction in a 3‐layer ocean is presented. Using representative ocean density profile data and the GS current data, we analyze the requirements for the generation and upward propagation of the disturbance induced by the current‐bathymetry interaction. Citation: Li, X., X. Yang, Q. Zheng, L. J. Pietrafesa, W. G. Pichel, Z. Li, and X. Li (2010), Deep‐water bathymetric features imaged by spaceborne SAR in the Gulf Stream region, Geophys. Res. Lett., 37, L19603,

32 citations


Journal ArticleDOI
31 Jul 2010
TL;DR: In this article, the physical and biological responses to Typhoon Nakri during a period from 1 to 8 June 2008 in the western North Pacific were examined using multi-satellite remote sensing data and Regional Ocean Model System (ROMS).
Abstract: In this paper, we use multi-satellite remote sensing data and Regional Ocean Model System (ROMS) to examine the physical and biological responses to Typhoon Nakri during a period from 1 to 8 June 2008 in the western North Pacific. From satellite observations, we find remarkable surface cooling (∼5 °C) and distinct phytoplankton enhancement after Nakri passage. It is interesting to note that in contrast to the well-documented rightward bias of the surface cooling response, the maximum biological response to Nakri occurred on the left of the Nakri’s track rather than the right side, where the most distinct cooling response occurred. To reveal the dynamic mechanism for this unusual phenomenon, we have done numerical experiments with and without the influence of preexisting cyclonic circulation and previous typhoon. The results from simulations show that both the physical and biological responses to Nakri are greatly affected by the preexisting cyclonic circulations. The discrepancy between the locations of maximum physical and biological responses mainly results from the advanced uplift and current advection of nutrient fields by previous typhoon Rammasun, which passed through the area about two weeks before Nakri.

29 citations


Journal ArticleDOI
TL;DR: The Deepwater Horizon explosion and fire in the Gulf of Mexico has caused an estimated 35,000 to 60,000 barrels of oil to leak into the waters off the coast of Louisiana, USA as discussed by the authors.
Abstract: Drilling rig Deepwater Horizon in the Gulf of Mexico, leased by BP PLC from Transocean Ltd., exploded and caught on fire on April 20, 2010. The drilling location is at some 50 miles (80 kilometers) off the coast of Louisiana, USA. The rig sank on April 22. Since then, oil has been pouring into the Gulf from the blown-out undersea well. As reported by US Today and Calgary Herald on July 3, an estimated 35 000 to 60 000 barrels of oil per day has been gushing out of the ruptured well into the Gulf. That means amounts to a total of 1.9 to 3.6 million barrels of oil so far have gushed into the Gulf. Using the high end of that estimate, the spill has now surpassed the 1979 Ixtoc blowout, which took nine months to cap and dumped estimated 3.3 million barrels (140 000 million gallons) into the Gulf of Mexico. It is topped only by the deliberate release of six to eight million barrels of crude oil by Iraqi troops who destroyed tankers and oil terminals and set wells ablaze in Kuwait during the 1991 Gulf War.

15 citations


Journal ArticleDOI
TL;DR: In this paper, the authors observed sea surface imprints of wave-like patterns with an average wavelength of 3.8 km in satellite synthetic aperture radar (SAR) images of the Bohai Sea and Huanghai Sea.
Abstract: In the satellite synthetic aperture radar (SAR) images of the Bohai Sea and Huanghai Sea, the authors observe sea surface imprints of wave-like patterns with an average wavelength of 3.8 km. Comparing SAR observations with sea surface wind fields and surface weather maps, the authors find that the occurrence of the wave-like phenomena is associated with the passing of atmospheric front. The authors define the waves as atmospheric frontal gravity waves. The dynamical parameters of the wave packets are derived from statistics of 9 satellite SAR images obtained from 2002 to 2008. A two-dimensional linear physical wave model is used to analyze the generation mechanism of the waves. The atmospheric frontal wave induced wind variation across the frontal wave packet is compared with wind retrievals from the SAR images. The CMOD-5 (C-band scatterometer ocean geophysical model function) is used for SAR wind retrievals VV (transmitted vertical and received vertical) for ENVISAT and HH (transmitted horizontally and received horizontally) for RADARSAT-1. A reasonable agreement between the analytical solution and the SAR observation is reached. This new SAR frontal wave observation adds to the school of SAR observations of sea surface imprints of AGWs including island lee waves, coastal lee waves, and upstream Atmospheric Gravity Waves (AGW).

9 citations


Journal ArticleDOI
TL;DR: The water masses of Kuroshio and SCS can be distinguished correctly with a high success rate and the result of water mass classification agrees well with the temperature-salinity characteristics derived from a cruise in May and June of 2006.
Abstract: An objective classification method is developed to distinguish the water masses of Kuroshio and South China Sea (SCS) by using an artificial neural network (ANN). Sea surface temperature (SST) and ocean-color data obtained from the Moderate Resolution Imaging Spectroradiometer in two specified areas to the east and west of Luzon, representing the Kuroshio and SCS waters, respectively, are used to train, validate, and test the ANN model. The water masses of Kuroshio and SCS can be distinguished correctly with a high success rate of over 99%. The model is then applied to the Luzon Strait, and the result of water mass classification agrees well with the temperature-salinity characteristics derived from a cruise in May and June of 2006. The performance is good in summertime when the SST or ocean color has a rather uniform spatial distribution and the traditional method of front detection by using a threshold value is inappropriate.

5 citations