青藏高原那曲地区冰冰雹天气系统中的大气电场   总被引：12，自引：9，他引：3  

周筠 Kajik.  M 《高原气象》2000,19(3):339-347

利用１９９８年４～９月间进行的ＧＡＭＥ－ＴＩＢＥＴ青堪稿原云和降水的多普勒雷达及大气平均电场加强期观测实验资料,对青藏高原那曲地区的冰雹天气系统中的大民电场作了定量观测和研究。结果表明：在降雹过程中大气电场强度基本上系统中的大气电场强度基本上均为负值,其峰值也均强于－２２ｋＶｍ＾－１;在降雹过程中随着降雹时间的临近,大民场强度基本不断增强,但降雹开始时大气电场强度并不达到其峰值,峰值出现的时刻比开  相似文献   

青藏高原那曲地区冰雹天气系统中的大气电场     

周筠珺  陈成品  刘黎平  楚荣忠  冯锦明  张彤  宋新民  M. Kajikawa  H. Fujii  Y. Aoi  T. Koike  S. Shimizu  K. Ueno 《高原气象》2000,19(3)

利用1998年4～9月间进行的GAME-TIBET青藏高原云和降水的多普勒雷达及大气平均电场加强期观测实验资料, 对青藏高原那曲地区的冰雹天气系统中的大气电场作了定量观测和研究.结果表明: 在降雹过程中大气电场强度基本上均为负值, 其峰值也均强于-22 kVm-1; 在降雹过程中随着降雹时间的临近, 大气电场强度不断增强, 但降雹开始时大气电场强度并未达到其峰值, 峰值出现的时刻比开始降雹的时刻略有滞后; 在各降雹日中, 较强的大气电场强度基本上对应着各冰雹谱分布段较多的冰雹数目, 而这种较好的相关在各谱分布段上都表现出来; 随着降雹时间的临近, 每5 min闪电频数不断增强.在开始降雹时每5 min闪电频数平均达到43, 峰值的出现时刻略滞后于开始降雹的时刻, 这一滞后时间一般平均在3 min左右; 在降雹过程中, 单位面积中的冰雹数目与对应时段内总闪电数有着较好的对数关系, 相关系数R为0.954 0.在降雹过程的时间序列上, 冰雹云成熟期过后, 总闪电次数与冰雹降雹率成反相关.  相似文献   

祁连山七一冰川物质平衡的最新观测结果   总被引：36，自引：16，他引：20  

蒲健辰  姚檀栋  段克勤  坂井亚规子  藤田耕史  松田好弘 《冰川冻土》2005,27(2):199-204

祁连山七一冰川观测结果表明, 2001/2002年度和 2002/2003 年度冰川物质平衡分别为-810mm和-316 mm水当量, 冰面出现显著的减薄状态. 和过去的观测结果相比较, 20 世纪 70 年代为较大的正平衡, 年平均为360 mm水当量; 80年代年平均为4 mm水当量, 基本接近零平衡状态. 到近两年亏损强烈, 为所有观测资料中负平衡值最大的年份, 零平衡线也达到最高位置. 物质平衡出现较大的负值和零平衡线位置升高的状况, 强烈反映了祁连山冰川对气候变暖过程的响应. 如果气候变暖趋势继续, 冰川物质平衡负值将增大、冰面减薄和雪线的升高, 冰川将继续呈现萎缩状态.  相似文献   

Rediscovering wood-laden debris flow studies: A perspective from Japan     

Kenta Koyanagi  Taku Yamada  Koji Ishida 《地球表面变化过程与地形》2023,48(1):104-118

Debris flow is one of the dominant processes distributing large wood (LW) within mountainous catchments. However, little has been reviewed on wood-laden debris flow (WLDF), presumably owing to limited reviewable works. This article, therefore, navigates the international readers through 40 years of WLDF studies, most of which have been published only in Japanese. Firstly, we reviewed the historical development of Japanese WLDF particularly focusing on the 1980s and the 1990s. A series of post-disaster fieldworks from the July 1982 Nagasaki flood to the July 1990 Kumamoto flood provided 32 catchment-scale wood budgeting data; empirical relationships among drainage area, dominant tree species, sediment yield, and wood loads associated with single debris flow disasters were illustrated. Secondly, the characteristics of WLDF were summarized based on relevant previous studies on the recruitment, transport, and deposition processes of LW during debris flows. Thirdly, we discussed the connectivity between those Japanese WLDF studies and international LW studies by relating/contrasting their research approaches and spatiotemporal scales. In contrast to global LW research trends, Japanese WLDF studies have almost exclusively regarded LW as hazardous materials (i.e., “driftwood” or “woody debris”) that need to be retained upstream of the inhabited areas. Those practice-oriented WLDF studies were concentrated on drainage areas of 10⁻² to 10⁰ km², representing 1–6 orders of magnitude smaller spatial scales than those generally covered by existing international LW studies. Strongly motivated by engineering requirements, “dynamic” interactions between debris flows and LW during floods have also been physically presented, mainly based on unique laboratory experiments involving steep flume (> 0.05) and mobile bed conditions. Finally, some future works for WLDF were briefly stated from practical and scientific perspectives. By “rediscovering” those WLDF studies domestically developed in Japanese debris flow channels since the 1980s, a more comprehensive understanding of LW dynamics in the river system may be achieved.  相似文献   

Ocean Tide Models Developed by Assimilating TOPEX/POSEIDON Altimeter Data into Hydrodynamical Model: A Global Model and a Regional Model around Japan   总被引：36，自引：0，他引：36  

Koji Matsumoto  Takashi Takanezawa  Masatsugu Ooe 《Journal of Oceanography》2000,56(5):567-581

A global ocean tide model (NAO.99b model) representing major 16 constituents with a spatial resolution of 0.5° has been estimated by assimilating about 5 years of TOPEX/POSEIDON altimeter data into barotropic hydrodynamical model. The new solution is characterized by reduced errors in shallow waters compared to the other two models recently developed; CSR4.0 model (improved version of Eanes and Bettadpur, 1994) and GOT99.2b model (Ray, 1999), which are demonstrated in comparison with tide gauge data and collinear residual reduction test. This property mainly benefits from fine-scale along-track tidal analysis of TOPEX/POSEIDON data. A high-resolution (1/12°) regional ocean tide model around Japan (NAO.99Jb model) by assimilating both TOPEX/POSEIDON data and 219 coastal tide gauge data is also developed. A comparison with 80 independent coastal tide gauge data shows the better performance of NAO.99Jb model in the coastal region compared with the other global models. Tidal dissipation around Japan has been investigated for M₂ and K₁ constituents by using NAO.99Jb model. The result suggests that the tidal energy is mainly dissipated by bottom friction in localized area in shallow seas; the M₂ ocean tidal energy is mainly dissipated in the Yellow Sea and the East China Sea at the mean rate of 155 GW, while the K₁ energy is mainly dissipated in the Sea of Okhotsk at the mean rate of 89 GW. TOPEX/POSEIDON data, however, detects broadly distributed surface manifestation of M₂ internal tide, which observationally suggests that the tidal energy is also dissipated by the energy conversion into baroclinic tide.  相似文献   

The optical/near-infrared broad-line emission and hard X-ray continuum of active galactic nuclei and ultraluminous infrared galaxies     

Masatoshi Imanishi †  Shiro Ueno 《Monthly notices of the Royal Astronomical Society》1999,305(4):829-833

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A derivation of the scaling law, the power law and the scaling relation for fetch-limited wind waves using the renormalization group theory     

Koji Ueno 《Journal of Oceanography》1998,54(6):641-649

A state of wind waves at a fetch is assumed to be transformed into another state of wind waves at a different fetch by the renormalization group transformation. The scaling laws for the covariance of water surface displacement and for the one-dimensional and two-dimensional spectrum and the power law for the growth relation are derived from the fact that the renormalization group transformation constitutes a semigroup. The scaling relation or the relation among the exponents of the power law is also derived, using the two assumptions that the renormalization group transformation is applicable to fetch-limited wind waves and that the saturated range exists, which implies that the directional distribution function of energy in the wave number region much larger than the peak wave number does not depend on wave number.  相似文献   

Determination of the freshwater origin of Coastal Oyashio Water using humic-like fluorescence in dissolved organic matter     

Yu Mizuno  Jun Nishioka  Takahiro Tanaka  Yuya Tada  Koji Suzuki  Yuta Tsuzuki  Atsuko Sugimoto  Youhei Yamashita 《Journal of Oceanography》2018,74(5):509-521

Coastal Oyashio Water (COW), defined as a water mass with a temperature lower than 2 °C and a salinity lower than 33.0, is distributed in the North Pacific Ocean off southeastern Hokkaido, Japan, from winter to spring. COW is rich in macronutrients and dissolved iron and is thus considered to affect the spring phytoplankton blooms in the Oyashio region. Although river water and sea-ice melt water have been considered freshwater end-members of COW, the contributions of these freshwater sources to COW have not been well described. In this study, the humic-like components in dissolved organic matter were first applied as a parameter to evaluate the freshwater end-members of COW in March 2015. Linear regressions with negative slopes were determined between the humic-like components and the salinity of COW. The intercepts of the regressions against the humic-like components were within the ranges of those observed for the local rivers of Hokkaido but were very different from those of sea ice. These findings suggest that river water contributed to the COW observed here as a freshwater end-member, although the contribution of sea-ice melt water to COW could not be evaluated. This novel approach also highlighted two different less-saline water masses in COW. The first was characterized by a lower temperature and relatively high levels of humic-like components, while the second was higher in temperature and had higher levels of humic-like components. It is suggested that these different characteristics are due to the contributions of water from different rivers and/or different effects of sea-ice melt water.  相似文献   

Estimation of heat flux through the eastern Bering Strait     

Kohei Mizobata  Koji Shimada  Rebecca Woodgate  Sei-Ichi Saitoh  Jia Wang 《Journal of Oceanography》2010,66(3):405-424

We estimated the northward heat flux through the eastern channel of the Bering Strait during the ice-free seasons between 1999 and 2008. This is likely about half of the total heat flux through the strait. The net volume transport and heat flux through the eastern channel of the strait were estimated from multiple linear regression models with in-situ/satellite remotely sensed datasets and NCEP reanalysis 10 m wind. The net volume transport was well explained by the west-east slope of sea level anomaly and NNW wind component at the strait. On the heat flux, the contributions of both barotropic and baroclinic components were taken into account. Estimated volume transport and vertical profile of temperature were used to calculate northward heat flux through the eastern channel of the strait. The magnitude of the estimated heat flux is comparable to estimates from in-situ measurements. Averaged heat flux in the eastern Bering Strait between 2004 and 2007 was about 1.9 times larger than that between 2000 and 2003. Maximum heat flux occurred in 2004, and same magnitude of heat flux was estimated from 2005 to 2007. This resulted not only from the increase in northward volume transport but also anomalous warm water intrusion from the Bering Sea. Our results suggest a candidate among the important parameters controlling heat budget, which contributes to the Arctic sea ice reduction, whereas more studies are required to confirm that this mechanism is actually responsible for the interannual and longer timescale variability.  相似文献   

Observations and modeling of the ice-ocean conditions in the coastal Chukchi and Beaufort Seas     

JIN Meibing  WANG Ji  MIZOBATA Kohei  HU Haoguo  SHIMADA Koji 《海洋学报(英文版)》2008,27(3):79-87

The Chukchi and Beaufort Seas include several important hydrological features： inflow of the Pacific water, Alaska coast current （ ACC ）, the seasonal to perennial sea ice cover, and landfast ice ＇along the Alaskan coast. The dynamics of this coupled ice-ocean system is important for both regional scale oceanography and large-scale global climate change research. A mumber of moorings were deployed in the area by JAMSTEC since 1992, and the data revealed highly variable characteristics of the hydrological environment. A regional high-resolution coupled ice-ocean model of the Chukchi and Beaufort Seas was established to simulate the ice-ocean environment and unique seasonal landfast ice in the coastal Beaufort Sea. The model results reproduced the Beaufort gyre and the ACC. The depthaveraged annual mean ocean currents along the Beaufort Sea coast and shelf hreak compared well with data from four moored ADCPs, but the simulated velocity had smaller standard deviations, which indicate small-scale eddies were frequent in the region. The model resuits captured the sea,real variations of sea ice area as compared with remote sensing data, and the simulated sea ice velocity showed an ahnost stationary area along the Beaufort Sea coast that was similar to the observed landfast ice extent. It is the combined effects of the weak oceanic current near the coast, a prevailing wind with an onshore component, the opposite direction of the ocean current, and the blocking hy the coastline that make the Beaufort Sea coastal areas prone to the formation of landfast ice.  相似文献