Abnormal Meridional Temperature Gradient and its Relation to the Okhotsk High

Tachibana, Yukio; Iwamoto, Takeshi; Ogi, Masayo; Watanabe, Yoshihisa

doi:10.2151/jmsj.2004.1399

Cited by 39 publications

(44 citation statements)

References 37 publications

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“…7a and 7b) suggest that the influences of other factors on the clear-sky ratio in this region are comparable to the influence of the frontal zone (e.g., the occurrence of the Okhotsk high, depressions without fronts in the high latitudes, and frequent sea fog and low level cloud around the Pacific coast of Hokkaido in summer). Of particular importance is the occurrence and development of the Okhotsk high and its influence on the summer climate variations of Hokkaido, as discussed in Nakamura and Fukamachi (2004) and Tachibana et al (2004). Regarding South Japan (clusters 8̶10; Figs.…”

Section: Relationship Of Interannual Variation Between Weather and Frmentioning

confidence: 98%

An Objective Frontal Data Set to Represent the Seasonal and Interannual Variations in the Frontal Zone around Japan

TAKAHASHI

2013

Journal of the Meteorological Society of Japan

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A long-term (1948̶2009) frontal data set was created with an objective method by using NCEP̶NCAR (National Centers for Environmental Prediction̶National Center for Atmospheric Research) reanalysis data. This method utilizes a gradient and a thermal front parameter (TFP) of a potential temperature and an equivalent potential temperature at 850 hPa (dθ, TFP(θ), and TFP(θe)). The TFP defined as the directional derivative of a gradient of a thermodynamic variable along its gradient is one of the measures of frontal intensity and is often used for objectively analyzing frontal positions on surface weather maps. On the basis of the frontal data set, the average seasonal behavior of the frontal zone around Japan, its influence on the weather in mid-summer, and the seasonal march of the frontal zone during El Niño/La Niña events were examined. The main results are summarized in the following points: 1) The frontal data set generated under the conditions of dθ > 0.04 K (100 km), and TFP(θe) > 0.69 K (100 km) −2 showed the strongest correlation to that compiled by counting the number of fronts on the surface weather maps around Japan. 2) Although the long-term frontal data set created in this study retained some differences in frequency, the seasonal march of the frontal zone was consistent with that created from fronts on the weather maps.3) The relationship of interannual mid-summer variations (July 20̶August 16) between the clear-sky ratio of Japan and the frontal zone and various mean characteristics of the Japanese climate during El Niño/La Niña events, most of which have been discussed in previous reports, were verified from the perspective of the variability in the frontal zone, which has not been clarified so far.These results of this work show that the frontal data set created herein has the advantage of being simple and objective and is useful for research on the detailed relationship in interannual variations between the regional climate around Japan and large-scale atmospheric conditions.

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Section: Relationship Of Interannual Variation Between Weather and Frmentioning

confidence: 98%

An Objective Frontal Data Set to Represent the Seasonal and Interannual Variations in the Frontal Zone around Japan

TAKAHASHI

2013

Journal of the Meteorological Society of Japan

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“…Two indices were analyzed using the monthly mean reanalysis data for 1958-2002: SW925, the southwest component of wind vector averaged over Hokkaido (408-458N, 1408-1458E; domain A in Fig. 9b) and the OH index (OHI; Tachibana et al 2004), defined as geopotential height at 850 hPa averaged over 558-57.58N and 147.58-157.58E. SW925 represents the northward fog-advection ability and the intensity of heat and moisture supply above the fog layer, both of which are important for stable stratification and a humid environment above the fog layer.…”

Section: Relationship Between Interannual Fog-frequency Variation Andmentioning

confidence: 99%

Effects of Synoptic-Scale Control on Long-Term Declining Trends of Summer Fog Frequency over the Pacific Side of Hokkaido Island

Sugimoto¹,

Sato²,

Nakamura³

2013

Journal of Applied Meteorology and Climatology

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In this study, long-term visibility data for the Pacific Ocean side of Hokkaido Island, northeast Japan, are investigated to clarify the relationship between interannual variation in summer fog frequency (FF) and largescale circulation patterns. At Kushiro, a significant FF decrease is found during 1931-2010 even without the influence of the observatory's relocation after 2000. In particular, since the late 1970s, a linear declining trend has accelerated, as evidenced by an increased number of years with very low FF in July and August. To clarify the climatological factor causing the summer FF declining trend at Kushiro, atmospheric vertical conditions in the planetary boundary layer and large-scale circulation are examined during 1989-2009 and 1958-2002, respectively, using available datasets. Composite analyses that are based on radiosonde observations reveal that the shallow fog layer is covered with a strong inversion layer during fog days whereas the inversion layer is absent during nonfog days. Composite circulation anomalies for the low-FF years at Kushiro show an intensified Okhotsk high (OH) pressure feature and southward shrinking of the North Pacific high (NPH) in July, in addition to the eastward displacement or shrinking of the NPH in August. These anomalous synoptic circulation patterns cause weakening in the southerly-southeasterly wind, which reduces sea-fog advection toward Kushiro and prevents the formation of stable stratification over the sea-fog layer. The authors suggest that the interannual variation in summer FF with the recent accelerated decline at Kushiro is primarily controlled by changes in the synoptic circulation associated with the OH and NPH development.

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“…Meanwhile, the strength and persistence of the easterly winds show large interannual variation in accordance with the activity of the Okhotsk high (e.g. Tachibana et al 2004), and such persistent easterly winds have caused record cool summers (e.g. Ninomiya & Mizuno 1985).…”

Section: Introductionmentioning

confidence: 95%

Summertime wave height variability along the Pacific and Okhotsk Sea coasts of northern Japan

Shimada¹

2014

Clim. Res.

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Wave height variability along the Pacific and Okhotsk Sea coasts of northern Japan in June-August is investigated using in situ measurements and reanalysis data. The coastal wave height is dominated by the persistent easterly winds induced by the developed Okhotsk high. These winds, which can induce cool summers in northern Japan, favor wave development toward the coast of northern Japan. The wave variability is enhanced along the coast of northern Tohoku by the strong local winds occurring in the lee of Cape Erimo. The results for variability of wave height along the Pacific and Okhotsk Sea coasts of northern Japan are supported by composite analysis of reanalysis wave data. When the Okhotsk high develops and the resulting easterly winds are dominant, the wave height increases near the coast of and to the east of northern Japan. Wave height also increases in the Japan Sea and along the southern coast of Japan, whereas wave height decreases in the Okhotsk Sea. These wave height variations reflect the distinct wind fields associated with the developed Okhotsk high. Trends in wave height are examined using the in situ measurements available for over 20 yr. Only the decreasing trends in the south of northern Japan in August are statistically significant.

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Abnormal Meridional Temperature Gradient and its Relation to the Okhotsk High

Cited by 39 publications

References 37 publications

An Objective Frontal Data Set to Represent the Seasonal and Interannual Variations in the Frontal Zone around Japan

An Objective Frontal Data Set to Represent the Seasonal and Interannual Variations in the Frontal Zone around Japan

Effects of Synoptic-Scale Control on Long-Term Declining Trends of Summer Fog Frequency over the Pacific Side of Hokkaido Island

Summertime wave height variability along the Pacific and Okhotsk Sea coasts of northern Japan

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