地闪回击的微秒级辐射场特征及近地面连接过程分析

利用１μｓ时间分辨率的慢天线电场变化仪在甘肃中川地区雷暴过程中测量得到的大量地闪辐射波形地地闪回击辐射场特征及回击的慢前沿过程进行分析,发现１８次正地闪和８５次负地闪产在周前沿过程上升时间为１９．２μｓ和９．４μｓ,８４次负地闪继后回击的前沿过程为４．３ μｓ。ＹＹ ＵＤＡ Ｏ ３．１μ;     

Year-to-Year and interdecadal variability in the activity of intraseasonal fluctuations in the Northern Hemisphere wintertime circulation

Summary Interannual variability in the activity of fluctuations with subseasonal time scales is investigated based upon observed data of the extratropical Northern Hemisphere circulation over the recent 38 winters. Their activity is represented in the root mean square (RMS) field of filtered geopotential height in which the fluctuations with time scales between 10 days and a season are retained. The singular value decomposition (SVD) was applied to the covariance matrix between the seasonal mean and RMS fields for the 500-hPa height.The leading SVD mode for the north Pacific represents the strong relationship between the polarity of the Pacific/North American (PNA) pattern in the seasonal-mean anomalies and the amplitude of a meridionally-oriented dipole-like oscillation within the season. It tends to be more active when the seasonal-mean jet stream is strongly diffluent over the central Pacific than when the jet is extended zonally across the Pacific. The leading SVD mode for the north Atlantic is indicative of stronger intraseasonal fluctuations near Greenland in the presence of anticyclonic seasonal-mean anomalies associated with the North Atlantic Oscillation (NAO).The intraseasonal variability in the extratropics is strongly correlated with the underlying sea surface temperature (SST) anomalies, and that in the north Pacific also exhibits significant but rather weak correlation with SST anomalies in the equatorial Pacific. The activity of the atmospheric intraseasonal fluctuations is found to be modulated in accordance with interdecadal variability in the seasonal-mean circulation and SST.On leave from Department of Earth & Planetary Physics, University of Tokyo.With 12 Figures     

The effect of back pressure on the contact evolution of a close binary system

The contact condition which includes the effect of pressure in common envelope is derived and employed in the evolutionary calculation of a close binary system in contact phase. The result indicates that the effect is negligibly small and the equality of surface potentials of both components is a sufficiently good approximation for the contact condition.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

Ore mineralogy and sulfur isotope study of the massive sulfide deposit of Filon Norte,Tharsis Mine,Spain

The volcanogenic massive sulfide deposit of Filon Norte at Tharsis is hosted by carbonaceous black slate and connected only partly with stockwork veins. The massive ores are usually composed of fine-grained pyrite with subordinate amounts of sphalerite, chalcopyrite, galena and arsenopyrite. Monoclinic pyrrhotite sometimes occurs in massive pyritic ores in the apparently middle and upper horizons of the orebody, and siderite-rich ores are interstratified with compact pyritic ores in the apparently lower horizons. From the occurrence of monoclinic pyrrhotite, together with the FeS contents of sphalerite mostly ranging from 11 to 16 mol %, it is inferred that the sulfide minerals of the massive orebody were precipitated in euxinic muds on the sea-floor at temperatures below 250°C. The negatively shifted, highly variable ³⁴S values of the massive ores and their close similarity to those of the underlying black slates strongly suggest that the sulfide sulfur of the massive orebody and the slates is cognate and biogenic.     

Boron cycling by subducted lithosphere; insights from diamondiferous tourmaline from the Kokchetav ultrahigh-pressure metamorphic belt

Subduction of lithosphere, involving surficial materials, into the deep mantle is fundamental to the chemical evolution of the Earth. However, the chemical evolution of the lithosphere during subduction to depth remains equivocal. In order to identify materials subjected to geological processes near the surface and at depths in subduction zones, we examined B and Li isotopes behavior in a unique diamondiferous, K-rich tourmaline (K-tourmaline) from the Kokchetav ultrahigh-pressure metamorphic belt. The K-tourmaline, which includes microdiamonds in its core, is enriched in ¹¹B relative to ¹⁰B (δ¹¹B = −1.2 to +7.7) and ⁷Li relative to ⁶Li (δ⁷Li = −1.1 to +3.1). It is suggested that the K-tourmaline crystallized at high-pressure in the diamond stability field from a silicate melt generated at high-pressure and temperature conditions of the Kokchetav peak metamorphism. The heavy isotope signature of this K-tourmaline differs from that of ordinary Na-tourmalines in crustal rocks, enriched in the light B isotope (δ¹¹B = −16.6 to −2.3), which experienced isotope fractionation through metamorphic dehydration reactions. A possible source of the heavy B-isotope signature is serpentine in the subducted lithospheric mantle. Serpentinization of the lithospheric mantle, with enrichment of heavy B-isotope, can be produced by normal faulting at trench-outer rise or trench slope regions, followed by penetration of seawater into the lithospheric mantle. Serpentine breakdown in the lithospheric mantle subducted in subarc regions likely provided fluids with the heavy B-isotope signature, which was acquired during the serpentinization prior to subduction. The fluids could ascend and cause partial melting of the overlying crustal layer, and the resultant silicate melt could inherit the heavy B-isotope signature. The subducting lithospheric mantle is a key repository for modeling the flux of fluids and associated elements acquired at a near the surface into the deep mantle.     

Influences of channelization on discharge of suspended sediment and wetland vegetation in Kushiro Marsh, northern Japan

The effects of wetlands on hydrology, water quality, and wildlife habitat are internationally recognized. Protecting the remaining wetlands is one of the most important environmental issues in many countries. However wetlands in Japan have been gradually shrinking due to agricultural development and urbanization, which generally lowers the groundwater level and introduces suspended sediment and sediment-associated nutrients into wetlands. We examined the influences of channelization on discharge of suspended sediment and wetland vegetation in Hokkaido, northern Japan. The impact of river channelization was confirmed not only by the sediment budgets but also by river aggradation or degradation after the channelization and by the resultant vegetational changes. The budgets of suspended sediment demonstrated that wash load was the predominant component accounting for 95% of the total suspended load delivered into the wetland. This suspended sediment was primarily transported into the wetland by flooding associated with heavy rainfall. Twenty-three percent of the wash load and 63% of the suspended bed material load were deposited in the channelized reach, which produced aggradation of about 2 m at the end of the reach. A shorting of the length of the channel, due to channelization of a meandering river, steepened the slope and enhanced the stream power to transport sediment. This steepening shifted the depositional zones of fine sediment 5 km downstream and aggraded the riverbed. Development of the watershed may increase not only the water discharge but also the amount of suspended sediments. The aggradation reduced the carrying capacity of the channel and caused sediment ladened water to flood over the wetlands. The fine sediment accumulated on the wetlands gradually altered the edaphic conditions and wetland vegetation. A low percentage (10 to 15%) of organic contents of wetlands' soil is more evidence indicating that the present condition is far different from normal. Original vegetation such as sedges and Alnus japonica were disappearing from the adjacent areas of the river channel and were being replaced by willow trees (Salix spp.).     

Suppression of Matrix Effects in ICP-MS by High Power Operation of ICP: Application to Precise Determination of Rb, Sr, Y, Cs, Ba, REE, Pb, Th and U at ng g-1 Levels in Milligram Silicate Samples

We found that the suppression of signals for ⁸⁸Sr, ¹⁴⁰Ce and ²³⁸U in rock solution caused by rock matrix in ICP-MS (matrix effects) was reduced at high power operation (1.7 kW) of the ICP. To make the signal suppression by the matrix negligible, minimum dilution factors (DF) of the rock solution for Sr, Ce and U were 600, 400 and 113 at 1.1, 1.4 and 1.7 kW, respectively. Based on these findings, a rapid and precise determination method for Rb, Sr, Y, Cs, Ba, REE, Pb, Th and U using FI (flow injection)-ICP-MS was developed. The amount of the sample solution required for FI-ICP-MS was 0.2 ml, so that 1.8 mg sample was sufficient for analysis with a detection limit of several ng g^-1. Using this method, we determined the trace element concentrations in the USGS rock reference materials, DTS-1, PCC-1, BCR-1 and AGV-1, and the GSJ rock reference materials, JP-1, JB-1, -2, -3, JA-1, -2 and -3. The reproducibilities (RSD %) in replicate analyses (n=5) of BCR-1, AGV-1, JB-1, -2, -3, JA-1, -2, and -3 were < 6 %, and typically 2.5%. The difference between the average concentrations of this study for BCR-1 and those of the reference values were < 2%. Therefore, it was concluded that the method can give reliable data for trace elements in silicate rocks.     

Seasonal variability in carbon demand and flux by mesozooplankton communities at subarctic and subtropical sites in the western North Pacific Ocean

We investigated seasonal changes in carbon demand and flux by mesozooplankton communities at subtropical (S1) and subarctic sites (K2) in the western North Pacific Ocean to compare the impact of mesozooplankton communities on the carbon budget in surface and mesopelagic layers. Fecal pellet fluxes were one order higher at K2 than at S1, and seemed to be enhanced by copepod and euphausiid egestion under high chlorophyll a concentrations. The decrease in pellet volume and the lack of any substantial change in shape composition during sink suggest a decline in fecal pellet flux due to coprorhexy and coprophagy. While respiratory and excretory carbon by diel migrants at depth (i.e., active carbon flux) was similar between the two sites, the actively transported carbon exceeded sinking fecal pellets at S1. Mesozooplankton carbon demand in surface and mesopelagic layers was higher at K2 than S1, and an excess of demand to primary production and sinking POC flux was found during some seasons at K2. We propose that this demand was met by supplementary carbon sources such as feeding on protozoans and fecal pellets at the surface and carnivory of migrants at mesopelagic depths.