prior to surface appearance of sunspot flux tubes and magneto-thermal pulsation of the Sun     

H. Yoshimura 《Astronomische Nachrichten》1994,315(5):371-390

We found an evidence that the luminosity of the Sun systematically decreased about 20 days before sunspot surface appearance by analysing time-lag correlation of time derivatives of running mean time profiles of the data of the Active Cavity Radiometer Irradiance Monitor (ACRIM) I experiment on board of Solar Maximum Mission (SMM) and of the data of the daily sunspot number. This indicates that sunspot flux tube cooling and heat transport blocking by the flux tubes start to take place in the interior of the solar convection zone well before the sunspot surface appearance. From this finding and our previous finding that the luminosity of the Sun systematically increased and the blocked heat appeared on the surface about 50 days after the sunspot surface appearance, a new view of sunspot formation and dynamics and a new view of the luminosity modulation emerged. (i) Sunspots of a solar cycle are formed from clusters of flux tubes which can be seen in the running mean time profile of the sunspot number as a peak with duration on the order of 100 to 200 days. (ii) Heat flow is blocked by the cluster of sunspot flux tubes inside the convection zone to decrease the luminosity about 20 days before the surface emergence of the sunspot cluster. (iii) The blocked heat appears on the surface about 50 days after the surface emergence of the cluster of sunspot flux tubes to heat up the surface. This appears as a thermal pulse in the running mean time profile of the ACRIM dat in between the peaks of the sunspot running mean time profile. This process of heating the surface makes the temperature gradient less steep and weakens the buoyancy of sunspot flux tubes below the surface. (vi) The radiative cooling of the surface layer by the excess heat release steepens the temperature gradient so that the buoyancy of the sub-surface magnetic flux tubes becomes stronger to cause the next surge of emergence of a cluster of sunspots and other magnetic activities, which creates a peak in the time profile of the sunspot number. We call this peak a magnetic pulse of the Sun and the coupled process of alternating pulsed appearance of heat and sunspots the magneto-thermal pulsation of the Sun.  相似文献   

Carbon Mineralization Associated with Soil Aggregates as Affected by Short-term Tillage     

GUO Linlin  NISHIMURA Taku  IMOTO Hiromi  SUN Zhigang 《资源与生态学报(英文版)》2016,7(2):101-106

Tillage practice has received much attention due to its effects on greenhouse gas emissions from agricultural fields. The understanding of carbon mineralization associated with soil aggregates helps to explore the influence mechanisms of tillage practice on soil carbon dynamics. Total carbon and carbon mineralization rates associated with various sizes of soil aggregates under no-tillage and tillage treatments were studied with a volcanic ash soil. Total carbon content in microaggregates (<0.25 mm) was higher than that in macroaggregates (>0.25 mm) for both the no-tillage and tillage treatments, since microaggregates of the volcanic ash soil include more fine silts and clay particles absorbing more organic agents. The carbon mineralization rate and total carbon were highly correlated (R² = 0.6552, P = 0.002) for both treatments, suggesting that soil aggregate size is an important factor to influence the carbon mineralization rate. The no-tillage system showed the advantage of improving soil structure for volcanic ash soil. A larger proportion of microaggregates with relatively high carbon mineralization might contribute to the greater carbon loss from tilled soils. Unlike aggregate size, short-term tillage showed no significant effects on carbon mineralization rates associated with aggregates in a specific size class.  相似文献   

Processes influencing iron distribution in the coastal waters of the Tsugaru Strait,Japan     

Yukiyo Saitoh  Kenshi Kuma  Yutaka Isoda  Hiroshi Kuroda  Hiromi Matsuura  Taku Wagawa  Hyoe Takata  Naoto Kobayashi  Seiya Nagao  Takeshi Nakatsuka 《Journal of Oceanography》2008,64(6):815-830

We report measurements of iron, nutrients, dissolved oxygen, humic-type fluorescence intensity and chlorophyll a concentrations in the coastal waters at the inflow (western) and outflow (eastern) ends of Tsugaru Strait (Japan) in June 2003 and 2004. Two different water masses (intensive eastward flow “subtropical Tsugaru Warm Current Water (TWCw)” and weak westward flow “subarctic Oyashio Water (OW)”) were observed at the eastern end of the strait. TWCw at the southern part of the eastern strait was vertically homogeneous with a uniform concentrations of iron (0.7–1.1 nM for labile dissolved Fe and 14–20 nM for total dissolvable Fe in 2003) as well as other chemical, biological and physical components throughout the water column of 200 m due to strong vertical mixing in the strait. The degree of mixing in the Tsugaru Warm Current (TWC) is predominantly affected by diurnal tidal current, which is strong during the period of tropical tides and weak during the period of equinoctial ones. The especially strong vertical water mixing in 2003 is caused by large dissipation energy input due to the bottom friction of passage-flow through the strait and tidal current. At the northern part of the eastern strait, the fresh surface layer overlying the OW and the deep-bottom waters in 2003 contained large concentrations of dissolved iron, resulting from iron supplied from river runoff and shelf sediments, respectively. These results suggest that the most important mechanism for transporting iron in the strait is the strong vertical water mixing due to the tidal current, and that the iron sources in the coastal waters are the organic-associated, iron-rich freshwater input into the surface water.  相似文献   

20th century seasonal moisture balance in Southeast Asian montane forests from tree cellulose δ18O     

Mengfan Zhu  Lowell Stott  Brendan Buckley  Kei Yoshimura 《Climatic change》2012,115(3-4):505-517

The seasonally varying moisture balance in a montane forest of Southeast Asia is reconstructed for the 20th century from the oxygen isotopic composition (δ¹⁸O) of subannual tree cellulose samples of Pinus kesiya growing at 1,500?m elevation on Doi Chiang Dao in northern Thailand. The cellulose δ¹⁸O values exhibit a distinctive annual cycle with amplitude of up to 12?‰, which we interpret to represent primarily the seasonal cycle of precipitation δ¹⁸O. The annual mean δ¹⁸O values correlate significantly with the amount of summer monsoon precipitation, and suggest a temporal weakening relationship between the South Asian monsoon and El Ni?o-Southern Oscillation over the late 20th century. The cellulose δ¹⁸O annual maxima values, which reflect the dry season moisture status, have declined progressively over the 20th century by about 3.5?‰. We interpret this to indicate a change in the contribution of the isotopically distinct fog water to the dry season soil moisture in response to rising temperature as well as deforestation.  相似文献   

Lost primordial continents   总被引：7，自引：2，他引：5  

Kenji Kawai  Taku Tsuchiya  Jun Tsuchiya  Shigenori Maruyama 《Gondwana Research》2009,16(3-4):581-586

We investigate the bulk density variations of some representative compositions for the lower mantle based on the pressure–volume–temperature equation of state of the constituent mineral phases. The density variations of pyrolite, harzburgite, mid-ocean ridge basalt (MORB), tonalite–trondhjemite–granodiorite (TTG), and anorthosite are studied at a temperature of 300 K and at lower mantle pressures. The density of MORB is greater than that of pyrolite throughout the lower mantle, while the density of harzburgite is slightly lower than that of pyrolite. The density of anorthosite is comparable to that of pyrolite in the lower mantle in general, and greater in the lowermost mantle, while the density of TTG is lower than pyrolite throughout the lower mantle. The above results have important implications for the fate of primordial continents, TTG and anorthosite crust. While subducted TTG might be stagnant in the mantle transition zone, dense subducted anorthositic crust could be expected to sink to the core–mantle boundary (CMB) and thus might be a major component of the D" layer immediately above the CMB. Thus, we propose that significant bodies of continental material could be present in the mantle in the transition zone and immediately above the CMB, in addition to the continents on the Earth's surface.  相似文献   

Winter precipitation isotope slopes of the contiguous USA and their relationship to the Pacific/North American (PNA) pattern   总被引：1，自引：0，他引：1  

Zhongfang Liu  Gabriel J. Bowen  Jeffrey M. Welker  Kei Yoshimura 《Climate Dynamics》2013,41(2):403-420

This study compares the synoptic-dynamic relationship between two phases of the Pacific/North American (PNA) pattern and winter precipitation isotopes at 73 sites across the contiguous USA. We use the spatial pattern of isotope slope—the rate of changes in precipitation isotope ratios with distance—to identify features in the seasonal precipitation isotope fields related to climatic patterns, PNA positive and PNA negative. Our results show relationships between zones of high isotope slopes and the spatial position of the polar jet stream and juxtaposition of air masses associated with the PNA pattern. During a positive PNA winter, zones of high isotope slope in the eastern USA shift southward. This change is coincident with a southward displacement of the polar jet stream in this region, which leads to a greater frequency of polar air masses and ¹⁸O-depleted isotope values of precipitation in the region. In the western USA, zones of high slope shift eastward during the positive PNA winter, associated with more frequent penetration of tropical air masses that bring ¹⁸O-enriched precipitation to the region. Differences in δ¹⁸O/temperature relationships between the PNA-positive and -negative winters and contrasting δ¹⁸O/temperature behaviors in the eastern and western USA provide support for the role of variation in moisture source and transport as a control on the isotopic patterns. These findings highlight the importance of synoptic climate driven by PNA pattern in determining the spatial patterns of precipitation isotopes and provide constraints on paleo-water isotope interpretation and modern isotope hydrological processes.  相似文献   

Energy flow in shallow depth based on vertical array records during recent strong earthquakes     

Takaji Kokusho  Taku Suzuki 《Soil Dynamics and Earthquake Engineering》2011

Wave energy flow in shallow ground depth is calculated based on main shock records obtained at 30 vertical array sites throughout Japan during nine recent strong earthquakes (M_J=6.4–8.0) by assuming vertical propagation of SH waves. It is generally found that upward energy tends to decrease considerably as it goes up from the base (about 100 m deep) to the ground surface. Large energy is reflected at layer boundaries with clear impedance contrast and returns to deeper ground, so that only less than 10–30% of the upward energy at the base level arrives at the ground surface in most sites. Energy dissipation calculated from the upward and downward energies tends to increase with the increase of damping ratio of the ground back-calculated from the seismic records. It is also found that the upward energy at the base may roughly be estimated for engineering purposes using spherical energy radiation of the body wave despite strong effects of fault rupture/path mechanisms.  相似文献   

Evidence for a seismic attenuation anomaly beneath the Hida Mountain Range, Central Honshu, Japan   总被引：2，自引：0，他引：2  

Kei Katsumata  Taku Urabe  Megumi Mizoue 《Geophysical Journal International》1995,120(2):237-246

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Two timescales in beach erosion due to decrease in sediment sources with special reference to the formation and reduction of the delta of the Kurobe River flowing into the Japan sea     

Yoshito Tsuchiya  Teruo Shibano  Hiroshi Suyama  Toshiaki Yoshimura 《Natural Hazards》1988,1(1):45-65

Beach erosion has advanced in many countries of the world, especially in Japan, because of a decrease in sediment sources from rivers and a lack of longshore sediment transport from the adjacent coasts due to coastal structures. The former cause concerns the reduction of river deltas due to a decrease in sediment input from the river. Two timescales important in beach erosion, a longer timescale which concerns a change in the location of the river mouth, and a shorter one which is due to a decrease in longshore sediment transport, are discussed in the formation and reduction of the delta of the Kurobe River. Based on these timescales, beach erosion control is considered.  相似文献   

Anomalous behavior of cristobalite in helium under high pressure     

Tomoko Sato  Hiroto Takada  Takehiko Yagi  Hirotada Gotou  Taku Okada  Daisuke Wakabayashi  Nobumasa Funamori 《Physics and Chemistry of Minerals》2013,40(1):3-10

We have investigated the high-pressure behavior of cristobalite in helium by powder X-ray diffraction. Cristobalite transformed to a new phase at about 8 GPa. This phase is supposed to have a molar volume of about 30 % larger than cristobalite, suggesting the dissolution of helium atoms in its interstitial voids. On further compression, the new phase transformed to a different phase which showed an X-ray diffraction pattern similar to cristobalite X-I at about 21 GPa. On the other hand, when the new phase was decompressed, it transformed to another new phase at about 7 GPa, which is also supposed to have a molar volume of about 25 % larger than cristobalite. On further decompression, the second new phase transformed to cristobalite II at about 2 GPa. In contrast to cristobalite, quartz did not show anomalous behavior in helium. The behavior of cristobalite in helium was also consistent with that in other mediums up to about 8 GPa, where the volume of cristobalite became close to that of quartz. These results suggest that dissolution of helium may be controlled not only by the density (amount of voids) but also by the network structure of SiO₄ tetrahedra (topology of voids).  相似文献