Single-Doppler Radar Analysis of a Mesocyclone in the Taiwan Strait          下载免费PDF全文

ZHAO Kun  JOU Ben Jongdao  PAN Yujie  GE Wenzhong 《Acta Meteorologica Sinica》2009,23(2):140-155

In this study, the kinematic and precipitation structures of a mesocyclone associated with a hook echo were analyzed using single Doppler radar data. The mesocyclone was embedded in a mesoscale convective rainband near northern Taiwan coastline on 10 September 2004. The synoptic environment was characterized by a moderate convective available potential energy (CAPE) and a moderate ambient vertical shear from surface to 5 km.In addition, a pronounced low-level mesoscale shear/convergence zone, which resulted from the interaction of two tropical depressions, was also identified in the northwest coast of Taiwan,providing a favorable dynamic condition for the development of the mesocyclone. Analyzing single Doppler dipole signature shows that this mesocyclone formed initially at low levels, then deepened and strengthened rapidly into mature stage with the vertical depth exceeding 8 km. The diameter of the mesocyclone decreased with the height at the time of vortexgenesis, and then evolved into columnar structure accompanied with the broader diameter in middle layer. The mesocyclone lasted for about 2 h. The Ground-Based Velocity Track Display (GBVTD) method was applied to retrieve the axisymmetric circulation of the mesocyclone. The GBVTD-derived primary circulation showed the radius of maximum wind (RMW) of the mesocyclone was about 5--6 km and varied from inward tilting to outward tilting with time. The axisymmetric radial wind field was initially characterized by a low-level inflow inside the RMW and outflow outside the RMW, respectively. The strongest reflectivity was associated with a stronger updraft near the RMW, and a weak downdraft was located at the center of the mesocyclone.Subsequently the downdraft and reflectivity near the mesocyclone center strengthened obviously, accompanied with the low-level outflow, strong updraft as well as high reflectivity extending outside the RMW. The relative tangential wind initially exhibited a wavenumber 1 asymmetric structure with the maximum wind region at the left portion of the meso cyclone and shifted counterclockwise with height. The axisymmetric tangential wind strengthened and reached its maximum intensity with a value about 20 m s-1 at z=1 km. After that the axisymmetric tangential wind decreased rapidly, meanwhile the wave-1 asymmetric structure redeveloped with the maximum wind at the left-front of motion. In summary, the evolution and structure of the mesocyclone is similar to that observed within a non-supercell mesocyclone. It is worth to mention that the axisymmetric circulation characteristics of the mesocyclone at its mature stage are very similar to those observed in a mature typhoon. However, there are significant differences, i.e., the size is much smaller, the lifetime is much shorter, and the downdraft in the center is produced by precipitation instead of compensating subsidence.  相似文献   

Spatial distribution characteristics of urban thermal conditions: application of GIS and remote sensing     

ZHOU Hong-mei  ZHOU Cheng-hu  GE Wei-qiang  DING Jin-cai 《地理学报(英文版)》2001,11(3):261-270

Due to the limitation of site number, manpower and material resources, it is hard to gain a deep understanding of the plane distribution and internal structure of the thermal conditions by routine methods to study the thermal landscape characteristics of the ground surface. Using remote sensing method to study and analyze heat island effect has many advantages, such as high resolution, wide coverage and dense samples. In order to study, in advance and synchronously, the thermal distribution ch…  相似文献   

Chronological and Geochemical Characterisitics of Volcanic Rocks of the Yingcheng Formation in the Southern Songliao Basin: Constraints on the Early Cretaceous Evolution of the Songliao Basin     

CHEN Jingsheng  WANG Liwu  ZHANG Yanlong  GE Wenchun  YANG Hao  JI Zheng  ZHANG Lidong  TIAN Dexin 《《地质学报》英文版》2020,94(4):1276-1300

The discoveries of oil and gas reservoirs in the volcanic rocks of the Songliao Basin(SB) have attracted the attention of many researchers. However, the lack of studies on the genesis of the volcanic rocks has led to different opinions being presented for the genesis of the SB. In order to solve this problem, this study selected the volcanic rocks of the Yingcheng Formation in the Southern Songliao Basin(SSB) as the research object, and determined the genesis and tectonic setting of the volcanic rocks by using LA-ICP-MS zircon U-Pb dating and a geochemical analysis method(major elements, trace elements, and Hf isotopes). The volcanic rocks of the Yingcheng Formation are mainly composed of rhyolites with minor dacites and pyroclastic rocks. Our new zircon U-Pb dating results show that these volcanic rocks were erupted in the Early Cretaceous(113–118 Ma). The primary zircons from the rhyolites have εHf(t) values of +4.70 to +12.46 and twostage model age(TDM2) of 876–374 Ma. The geochemical data presented in this study allow these rhyolites to be divided into I-type rhyolites and A-type rhyolites, both of which were formed by the partial melting of the crust. They have SiO2 contents of 71.62 wt.%–75.76 wt.% and Al2 O3 contentsof 10.88 wt.% to 12.92 wt.%. The rhyolites have distinctively higher REE contents than those of ordinary granites, with obvious negative Eu anomalies. The light to heavy REE fractionation is not obvious, and the LaN/YbN(average value = 9.78) is less than 10. The A-type rhyolites depleted in Ba, Sr, P, and Ti, with relatively low Nb/Ta, indicating that the rocks belong A2 subtype granites formed in an extensional environment. The adakitic dacites are characterized by high Sr contents(624 to 1,082 ppm), low Y contents(10.6 to 12.6 ppm), high Sr/Y and Sr/Yb ratios, and low Mg# values(14.77 to 36.46), indicating that they belong to "C" type adakites. The adakitic dacite with high Sr and low Yb were likely generated by partial melting of the lower crust under high pressure conditions at least 40 km depth. The I-type rhyolites with low Sr and high Yb, and the A-type rhyolites with very low Sr and high Yb, were formed in the middle and upper crust under low pressure conditions, respectively. In addition, the formation depths of the former were approximately 30 km, whereas those of the latter were less than 30 km. The geochemical characteristics reveal that the volcanic rocks of Yingcheng Formation were formed in an extensional environment which was related to the retreat of subducted Paleo-Pacific Plate. At the late Early Cretaceous Period, the upwelling of the asthenosphere mantle and the lithosphere delamination caused by the retreat of the subducted Paleo-Pacific Plate, had resulted in lithosheric extension in the eastern part of China. Subsequently, a large area of volcanic rocks had formed. The SB has also been confirmed to be a product of the tectonic stress field in that region.  相似文献   

基于有向窗的自适应SIGMA中值滤波算法   总被引：4，自引：0，他引：4  

许才军  王华  王江林  GE Linlin 《武汉大学学报(信息科学版)》2005,30(10):873-876

提出了一种能够有效消除InSAR DEM噪声的自适应中值滤波算法:基于有向窗的自适应SIGMA中值滤波。分别采用中值滤波、基于高程的自适应SIGMA中值滤波和基于有向窗的自适应SIGMA中值滤波算法,对InSAR Tandem DEM和模拟DEM进行了滤波处理。结果表明,基于有向窗的自适应SIGMA中值滤波算法不仅能够更有效地消除噪声,而且能够更好地保留图像的边界特征。  相似文献   

Earthquake damage and loss estimation with Geographic Information System   总被引：1，自引：0，他引：1  

YONG CHEN GE PING LI QI FU CHEN LING CHEN MIN FENG LI Center for Analysis  Prediction  China Seismological Bureau  Beijing  China 《地震学报(英文版)》1998,11(6):751-758

ＩｎｔｒｏｄｕｃｔｉｏｎＡｓｅｓｉｎｇｔｈｅｐｏｔｅｎｔｉａｌｅａｒｔｈｑｕａｋｅｄａｍａｇｅａｎｄｌｏｓｉｎａｒｅｇｉｏｎｉｓｉｍｐｏｒｔａｎｔｆｏｒｍａｎｙａｓｐｅｃｔｓ,ｓｕｃｈａｓｒｉｓｋｍｉｔｉｇａｔｉｏｎ,ｒｅｓｏｕｒｃｅｓａｌｏｃａｔ...  相似文献   

Long-term seismic network in South China Sea by floating MERMAIDs     

Yong YU  Yongshun John CHEN  Zhen GUO  Zengxi GE 《中国科学:地球科学(英文版)》2023,(9):1979-1993

Seismic data coverage in ocean regions is sparse, and it is highly challenging to build long-term continuous seismic networks in the oceans due to the restrictions related to the shortage of instruments and great costs. The lack of data coverage limits effective seismic imaging of deep mantle structures beneath the oceans, which cover 70% of the Earth’s surface. The newly developed Mobile Earthquake Recorder in Marine Areas by Independent Drivers(MERMAID) can drift with ocean currents at a speci...  相似文献   

Modulation of High-Latitude Tropical Cyclone Recurvature by Solar Radiation     

Jiawei LING  Xuyang GE  Melinda PENG  Qijun HUANG 《Journal of Meteorological Research》2023,(6):802-811

In this study, idealized simulations are conducted to investigate potential influences of solar radiation on the tropical cyclone(TC) recurvature at higher latitudes. Results indicate that TC track is sensitive to the seasonal variation of radiative forcing at higher latitudes. In the absence of a background flow, TCs at higher latitudes tend to recurve(remain northwestward) in the cold(warm) season. This feature is an additional aspect of the so-called intrinsic recurvature property of TC movem...  相似文献   

Spatial and temporal variation in seagrass coverage in Southwest Florida: assessing the relative effects of anthropogenic nutrient load reductions and rainfall in four contiguous estuaries     

Tomasko DA  Corbett CA  Greening HS  Raulerson GE 《Marine pollution bulletin》2005,50(8):797-805

The estuaries of Tampa Bay, Sarasota Bay, Lemon Bay, and Upper Charlotte Harbor are contiguous waterbodies located within the subtropical environment of Southwest Florida. Based on an examination of rainfall data over the period of record (1916-2001) within the watersheds of these estuaries, there is no evidence for spatial differences (at the watershed level) or monotonic trends in annual rainfall. During the 1980s, nitrogen loads into Tampa Bay and Sarasota Bay (generated primarily by domestic wastewater treatment facilities) were reduced by 57% and 46%, respectively. In response, both Tampa Bay and Sarasota Bay have lower phytoplankton concentrations, greater water clarity and more extensive seagrass coverage in 2002 than in the early 1980s. As there is no evidence of a concurrent trend in rainfall during the period of 1982-2001, it is unlikely that variation in rainfall can account for the observed increase in seagrass coverage in these two bays. In contrast, seagrass coverage has remained relatively constant since the mid 1980s in Lemon Bay and Charlotte Harbor. Domestic wastewater treatment facilities are minor sources of nitrogen to Lemon Bay, and water clarity in Charlotte Harbor varies mostly as a function of dissolved organic matter and non-chlorophyll associated turbidity, not phytoplankton levels. Even in estuaries that share boundaries and are within 100 km of each other, varied responses to anthropogenic changes and natural phenomena were observed in water quality and associated seagrass extent. Resource management strategies must take into account system-specific factors-not all strategies will result in similar results in different systems.  相似文献   

Effect of an acid mine drainage effluent on phytoplankton biomass and primary production at Britannia Beach, Howe Sound, British Columbia     

Levings CD  Varela DE  Mehlenbacher NM  Barry KL  Piercey GE  Guo M  Harrison PJ 《Marine pollution bulletin》2005,50(12):158-1594

We investigated the effect of acid mine drainage (AMD) from an abandoned copper mine at Britannia Beach (Howe Sound, BC, Canada) on primary productivity and chlorophyll a levels in the receiving waters of Howe Sound before, during, and after freshet from the Squamish River. Elevated concentrations of copper (integrated average through the water column >0.050 mg l⁻¹) in nearshore waters indicated that under some conditions a small gyre near the mouth of Britannia Creek may have retained the AMD from Britannia Creek and from a 30-m deep water outfall close to shore. Regression and correlation analyses indicated that copper negatively affected primary productivity during April (pre-freshet) and November (post-freshet). Negative effects of copper on primary productivity were not supported statistically for July (freshet), possibly because of additional effects such as turbidity from the Squamish River. Depth-integrated average and surface chlorophyll a were correlated to copper concentrations in April. During this short study we demonstrated that copper concentrations from the AMD discharge can negatively affect both primary productivity and the standing stock of primary producers in Howe Sound.  相似文献   

The Sedimentary Characteristics of Suning–Dawangzhuang Carbonate Bar in Ji Zhong Depression     

HUANG Jingxuan  LU Shuangfang  CHEN Fangwen GE Xiaobo  and WU Yihao 《《地质学报》英文版》2015,89(Z1):39-40

  相似文献