Large-scale chaotically mixed sedimentary body within the Late Pliocene to Pleistocene Chikura Group, Central Japan

The late Pliocene phase of large-scale climatic deterioration about 3.2-2.4 Ma BP is well documented in a number of (benthic) δ 18 O records. To test the global implications of this event, we have mapped the distribution patterns of various sediment variables in the Pacific and Atlantic Oceans during two time slices, 3.4-3.18 and 2.43-2.33 Ma BP. The changes of bulk sedimentation and bulk sediment accumulation rates are largely explained by the variations of CaCO 3 -accumulation rates (and the accumulation rates of the complementary siliciclastic sediment fraction near continents in higher latitudes). During the late Pliocene, the CaCO 3 -accumulation rate increased along the equatorial Pacific and Atlantic and in the northeastern Atlantic, but decreased elsewhere. The accumulation rate of organic carbon (C org ) and net palaeoproductivity also increased below the high-productivity belts along the equator and the eastern continental margins. From these patterns we may conclude that (trade-) wind- induced upwelling zones and upwelling productivity were much enhanced during that time. This change led to an increased transfer of CO 2 from the surface ocean to the ocean deep water and to a reduction of evaporation, which resulted in an aridification of the Saharan desert belt as depicted in the dust sediments off northwest Africa.

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Large-Scale Circulation Anomalies Associated with Extreme Heat in South Korea and Southern–Central Japan

10.5194/egusphere-egu2020-8477 ◽

2020 ◽

Author(s):

Ke Xu

Keyword(s):

South Korea ◽

East Asia ◽

Large Scale ◽

Extreme Heat ◽

Central Japan ◽

Large Scale Circulation ◽

Westerly Jet ◽

Anomalous Anticyclone ◽

Wave Trains ◽

Circulation Anomalies

&#160;&#160;&#160; The large-scale circulation anomalies associated with extreme heat (EH) in South Korea and southern&#8211;central Japan are examined using data during the time period 1979&#8211;2016. Statistical analysis indicates that EH days in these two regions are concentrated in July and August and tend to occur simultaneously. These EH days are therefore combined to explore the physical mechanisms leading to their occurrence. The composite results indicate that the anomalous atmospheric warming during EH days is dominantly caused by a significant subsidence anomaly, which is associated with a deep anomalous anticyclone over East Asia. Further investigation of the evolution of circulation anomalies suggests that the anomalous anticyclone over East Asia related to EH is primarily initiated by wave trains originating from upstream regions, which propagate eastward along the Asian westerly jet in the upper troposphere. These wave trains can be categorized into two types that are characterized by the precursor anticyclonic and cyclonic anomalies, respectively, over central Asia. The distinction between these two types of wave train can be explained by the wavenumbers of the Rossby waves, which are modulated by both the intensity and the shape of the Asian westerly jet as the background basic flow.

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Large-scale landslides in Toyama Prefecture, central Japan, and their probable relationship with earthquakes

Environmental Earth Sciences ◽

10.1007/s12665-013-2654-y ◽

2013 ◽

Vol 71 (6) ◽

pp. 2753-2763 ◽

Cited By ~ 7

Author(s):

Satoru Kojima ◽

Tamotsu Nozaki ◽

Hidehisa Nagata ◽

Ryota Tanahashi ◽

Ryoich Kondo ◽

...

Keyword(s):

Large Scale ◽

Central Japan ◽

Probable Relationship

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Comparison of the Circulation Anomalies Associated with Wet and Dry Extreme Heat in South Korea and Southern–Central Japan

Journal of Climate ◽

10.1175/jcli-d-20-0260.1 ◽

2020 ◽

pp. 1-54

Author(s):

Ke Xu ◽

Riyu Lu ◽

Ying Na ◽

Baek-Jo Kim ◽

Jiangyu Mao ◽

...

Keyword(s):

South Korea ◽

Large Scale ◽

Type A ◽

Wave Pattern ◽

Extreme Heat ◽

Statistical Characteristics ◽

Formation Mechanisms ◽

Type B ◽

Central Japan ◽

Southern Central

AbstractThis study indicates a significant variation of humidity on extreme heat (EH) days over South Korea and southern–central Japan during the period 1979–2018. EH is therefore classified into three categories: type-A and type-B wet EH, and dry EH. Their statistical characteristics and formation mechanisms are investigated and compared. Our results suggest that the type-A wet EH is the most destructive, with the highest intensity, longest duration and broadest spatial scale covering most of mid-latitude East Asia. By contrast, type-B wet EH and dry EH are weaker, shorter and mostly confined to northeast Asia. Despite these differences in characteristics, both types of wet EH are caused by the poleward advance of tropical warm and humid air masses as a result of the northward displacement of the Asian westerly jet. By contrast, dry EH is primarily induced by an increase in adiabatic heating and solar radiation resulting from anomalous subsidence.The three types of EH are associated with distinct large-scale teleconnections over Eurasia. A stable and persistent tripole wave pattern is responsible for type-A wet EH. The activity of atmospheric blocking over northern Europe, where the pattern originates, plays a crucial role in maintaining this pattern. By contrast, type-B wet EH and dry EH are related to a quadruple pattern and a Silk Road pattern-like teleconnection, respectively, both lasting for a shorter time. These results highlight the diversity of EH, which suggests that multiple local and large-scale circulations should be considered to improve the forecast skills for EH.

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On the Baiu frontal-scale rainfall characteristics and atmospheric conditions in the extremely heavy rainfall event around western Japan during 5-7 July 2018 with attention to the synoptic climatological viewpoint

10.5194/egusphere-egu2020-3083 ◽

2020 ◽

Author(s):

Kuranoshin Kato ◽

Kengo Matsumoto ◽

Takato Yamatogi ◽

Chihiro Miyake

Keyword(s):

Heavy Rainfall ◽

Large Scale ◽

Rainfall Amount ◽

Heavy Rainfall Event ◽

Atmospheric Conditions ◽

Total Rainfall ◽

Central Japan ◽

Rainfall Characteristics ◽

Western Japan ◽

Eastern Japan

&#160;&#160; In East Asia, a significant subtropical front called the Baiu/Meiyu front appears just before midsummer and brings the huge rainfall there, greatly influenced by the Asian summer monsoon. However, large-scale atmospheric features and rainfall characteristics (such as convective or stratiform rain) as well as the total rainfall amount around the front show rather great differences between the western and eastern portions. For example, in the western part of the Japan Islands (especially around Kyushu District, the most western part) and the Changjiang River Basin in Central China, the more frequent appearance of the heavy rainfall events due to the organized deep convective clouds than in the eastern Japan results in the larger climatological precipitation amount there. This is greatly related to the larger moisture transport toward the western part of the Baiu front than toward the eastern part. On the other hand, the rainfall characteristics around the front in the eastern Japan tend to be largely influenced by the cool Okhotsk air mass with rather stable stratification. Furthermore, their year-to-year, intraseasonal and short-period variations including the diversity of the &#8220;heavy rainfall types&#8221; are also very large.The extreme events in association with the Baiu/Meiyu activity are greatly reflected by the above variability of the frontal activity. Inversely, it would be also important viewpoint that detailed examination of some extreme events could lead to the better understanding of the &#8220;dynamic climatological features&#8221; of the Baiu/Meiyu system itself.In such concept, the present study will examine the frontal-scale rainfall features and the atmospheric conditions for the extremely heavy rainfall event around the Baiu front in western to central Japan during 5-7 July 2018. Although it is the common feature for the Baiu frontal rainfall heavy in western Japan that the frequent appearance of the meso-scale intense rain bands results in the huge total rainfall amount there, it is noted that the extremely large total rainfall area was distributed much more widely up to the central Japan with also considerable contribution of the long-persistent &#8220;not-so-intense rain&#8221; there, as often found in the heavy rainfall in the eastern Japan. Our analyses of the atmospheric fields suggest that this extreme event seems to be characterized by the strong mixture both of the large-scale factors for activating the &#8220;western Japan Baiu&#8221; and the &#8220;eastern Japan Baiu&#8221;.As for the precipitation analyses, the 10-minute precipitation data at many meteorological stations in the Japan Islands area were used to discuss on the frontal-scale &#8220;rainfall characteristics&#8221; as well as the total rainfall amounts.

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