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🌤 | East Japan Pacific side In the afternoon, there are thunderstorms


East Japan Pacific side In the afternoon, there are also thunderstorms

If you write the contents roughly
The Baiu front, which extends from the south of Okinawa to the far east of Japan, moves slightly southward as a whole due to the overhanging high pressure that moves near western Japan.

On the 18th (Wednesday), the high pressure in the East China Sea will move to the vicinity of western Japan, so it will be mostly sunny in western and northern Japan.But a thousand ... → Continue reading

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    Far east

    rainy season

    rainy season(Tsuyu, Bai) isHokkaidoとOgasawara Islandsexcept forJapan,Korean PeninsulaSouth,ChugokuFrom the south ofYangtze RiverCoastal areas over the basin, andTaiwanSuch,East AsiaUnique to a wide range ofMeteorological phenomenonSo it's coming from May to July(I.e.,(I.e.It is a period with a lot of.(I.e.Is a type of[1].

    Rainy season in the four seasons of East Asia

    When comparing climatological seasonal changes with the world, in East AsiaSpring Summer Autumn WinterFive seasons with the rainy season added toJapanFurther limited toautumn rainThe changes of the six seasons with the addition of[1].

    In East AsiaSpring:,Fall:It is,Temperate lowとMobile high pressureAlternately pass and the weather changes periodically.On the other hand, in midsummerSubtropical high(Pacific high), And is covered with hot and humid air mass.Then, between spring and midsummer, and between midsummer and autumn, the rainy season occurs due to the stagnation of fronts from eastern mainland China to the eastern offshore of Japan.Of these, the rainy season between spring and midsummer is the rainy season, and the rainy season between midsummer and autumn is the autumn rain.The rainy season is clear throughout East Asia, while the autumn rain is weak in the direction of mainland China and clear in the direction of the Japanese archipelago.Also, as a breakdown of the rain in the rainy season between midsummer and autumn,typhoonThe rain caused by is also influential[1].

    That the rainy season is about to beginRainy season,Into plumIt ’s called (Nyubai),Social beliefUp·MeteorologyAbove isSpring:With the end ofSummer: It is said to be the beginning of (early summer).In addition, JapanMiscellaneousTo one ofInto plum(Around June 6th)calendarOn the top, this day is called Ume, but this requires water.rice plantingIt is used as a guide for the time of.Also, that the rainy season will endAfter the rainy season,PlumIt is called (shutsubai), and it is often the arrival of full-scale summer (midsummer).In most areasMeteorological authoritiesHas announced the start of the rainy season and the end of the rainy season.

    The period of the rainy season is usually about one to one and a half months.In addition, the amount of precipitation during the rainy season isKyusyuThen, about 500 mm is about a quarter of the year.Kanto,TokaiThen, it is about 300 mm, which is about one-fifth of the year.In western Japan, the rainy season has more rainfall than in autumn, but in eastern Japan, it has more rainfall (with the contribution of typhoons).The time of the rainy season and the amount of rainfall may fluctuate greatly depending on the year. For example, it may rain only about 5 mm, or the end of the rainy season may be delayed by two weeks from the normal year.Such a yearIntense heat-Light rainIsCold summer・ Summer weather is not good due to heavy rain.disasterIs easy to occur[1][2][3].

    East Asia is located at mid-latitudes.At the same latitudeMiddle EastSuch asSubtropical highIt is not strange that the climate will be dry under the influence of the above, but the eastern coast of the continent tends to be rainy because it becomes the margin of the subtropical high pressure that covers the ocean in summer.this isNorth AmericaThe same is true on the east coast, but in Kyushu, the annual rainfall is about 2,000 mm.Tropical convergence zoneThere is as much rainfall as there is.The contribution of the rainy season and autumn rain to this abundant rainfall is large.As a factor that the rainy season brings a large amount of rainfallIndiaからSoutheast AsiaHot and humid Asia that leads tomonsoonIt can be mentioned that it is influenced by[1][4].

    Occasionally, the rainy season is described as "raining slowly" and "rainy and cloudy weather continues".this isEast JapanThat's correct,West JapanThat's not very correct.This is because there are regional differences in the way the rainy season rains.Especially in western JapanCentral China(Yangtze RiverIn the middle and lower reaches (near the middle and lower reaches), cloud clusters with a horizontal scale of about 100 km, which are a collection of cumulonimbus clouds, often occur and move eastward, causing heavy rain.[1]..Looking at the rainfall in June-July, which is the rainy season in mainland Japan, on heavy rainy days with a daily rainfall of 6 mm or more, the rainfall increases toward the west and south, as well asKyusyu,ShikokuPacific Ocean sideSo more than half of the two-month rainfall is concentrated on days with daily rainfall of 2 mm or more for only 4-5 days.[5]..The total rainfall during the rainy season itself increases as it goes west and south in mainland Japan.[1].


    Kanji notation "rainy season"EtymologyAs for this timeplumThe theory is that the fruit is about to ripen, and the humidity is high at this time.MoldBecause it is easy to growrainy seasonThere is a theory that it turned into the same sound of "rainy season", and that it rains like "every" day, so the word "ume" was applied.It rains twice as much as usual, so "double rain" is awkward (Folk etymology).Besides this, "Plum blossom(Bairin) ",Old calendarで5"Around the time"Rainy season(Samidare) ",wheat"Barley rainThere are other names such as "(Bakuu)".

    In addition, the word "May rain" has changed, and it has come to be called "May rain ceremony" when things continue for a long time, like the rain during the rainy season.In addition, the rainy season is called "May clear(Satsukibare) ”, but these days it is often read as“ Gogatsubare ”and refers to the sunny weather in early May of the new calendar.Japanese Meteorological AgencyThen, it is agreed that the sunny weather in May is called "Satsuki sunny" and the sunny season during the rainy season is called "the sunny season between the rainy seasons".The darkness of the night when it rains in MayMay darkness(Yami Satsuki) ".

    The local name is "Nagashi" (KagoshimaAmami archipelago[6]), "Namissa" (Kikai IslandAlias ​​in[7]).OkinawaThen the rainy seasonXiaomanからMang speciesBecause it is the time to go toXiaoman Mangzhong(Suman Bosu, Shomanboshu) "and"Mangzhong rain(Boss Ami, Boshu Ame) ".

    ChugokuThen "rainy season(Mayu)[1],TaiwanThen "rainy season(Mayyu) ”and“ Mangzhong ”, South KoreaThen "The rainy season(Chamma)[1]That is.In China, in the old daysrainy seasonAnd the same sound as ""Rainy seasonIs applied, and it is still used today. "霉IsMoldIt has the same meaning as "rainy season" in Japan.In China, plums are ripe黄色"It means rain when it becomes rainy"Yellow rainy season(Fan Mayu) ”is also often used[8].

    Mechanism and progress

    air mass

    During the rainy season, the following fourair massExists in East Asia.

    North ChinaEur-lex.europa.eu eur-lex.europa.euからManchuriaExists in the area.Warm and dry continental air mass.It is composed of mobile high pressure.
    Sea of ​​OkhotskExists in.A cold, moist marine air mass.
    Indochina Peninsula-South China SeaからNansei IslandsExists in the area near the sea.A warm and very moist marine air mass.Indian OceanIt is strongly influenced by the oceanic air mass of.
    North PacificExists in the west.Hot, humid and marine air mass.

    Spring:As the seasons change from summer to summer, these air masses of different natures compete in East Asia.The air masses that compete with each other differ between the mainland China and the Japanese archipelago and the Korean Peninsula.

    • Mainland ChinaDirection: North■Yangtze River GangAnd the south■Tropical monsoon air massApproach and a stationary front is formed mainly due to the difference in humidity between the two.[Note 1].
    • Japanese archipelago-Korean PeninsulaDirection: North■Okhotsk Kaiki GroupAnd the south■Ogasawara KidanApproach and a stationary front is formed mainly due to the temperature difference between the two.[Note 1].

    No front is formed between the air masses on the north side and the air masses on the south side due to their similar properties and the fact that they are far apart and there is little interference.

    Thousands of kilometers east and west where the north and south air masses collidedRainy season front(Baiu Zensen) is formed, and it gradually moves northward over several months.It continues to rain near this front, but the duration of long rains can be as long as one to two months in each region.This is the rainy season.

    Terra MODIS Stationary front cloud over Japan 4.jpg
    Clouds on the Baiu front stagnating in South China (upper part of the image, May 2008, 5, PD NASA)
    Terra MODIS Stationary front cloud over Japan.jpg
    Clouds on the Baiu front stagnating in Honshu (center of the image. The dark green part below is from Kyushu to the Kii Peninsula. July 2006, 7, PD NASA)
    Terra MODIS Stationary front cloud over Japan 2.jpg
    Clouds on the Baiu front stagnating from China to the Korean Peninsula (near the center of the image. July 2008, 7, PD NASA)

    The beginning of the rainy season front

    During the winter, a wide area from Siberia to mainland China was cold and dry.Siberian air massIs covered.Siberian air masses often travel south to bring cold waves to JapanSea of ​​Japan sideIt snows heavily, butTibetan PlateauThen the high mountains interfere and the air mass cannot go further south.Over the south side of the Tibetan Plateau, India-PhilippinesSubtropical jet streamFlows.

    As winter ends and spring approaches, the Siberian air force becomes weaker and gradually moves northward.Instead, a warm and dry Yangtze River air mass began to form on the Chinese mainland, strengthening its power.In spring, the Yangtze River Kidan will move to the eastern Japanese archipelago and the Korean Peninsula.Mobile high pressureAnd this isWesterliesRiding east, created during the high pressure(I.e.At the same time, it creates a changing weather in spring.

    As spring approaches the endSouth China SeaThe nearby tropical monsoon air mass gains power and moves north.Then, the Yangtze River Air Mass and the Tropical Monsoon Air Mass begin to collide.Surface weather mapIt can be seen that the high pressure formed by the Yangtze River air mass and the high pressure formed by the tropical monsoon air mass compete with each other over the South China Sea, and a front is formed between them.This is the first Baiu front.

    Every year, in the vicinity of South China and the southern part of the Nansei Islands, a cloud zone (technically called a semi-steady cloud zone), which is the beginning of the Baiu front, occurs around the beginning of May.

    The rainy season front becomes clear

    In early May, the Nansei Islands will also begin to be affected by the Baiu front. Around mid-May, the Baiu front becomes clearly visible on the weather map and stagnates near South China and the Nansei Islands.

    On the other hand, around May in early summer, the subtropical jet stream also moves northward and reaches the Tibetan Plateau.However, since the Tibetan Plateau is even higher than the subtropical jet stream that flows over the sky, the subtropical jet stream is divided into two streams, north and south, with the Tibetan Plateau as the boundary.

    Of the divided subtropical jet streams, the northern branch isKarafutoIn the vicinityBoreal jet streamMeet with.Furthermore, this airflowKamchatka PeninsulaIt merges with the branch on the south side in the vicinity.When the atmosphere above the merging is stagnant, a downdraft is generated and an anticyclone is created above the Okhotsk Sea.This high pressureOkhotsk Sea HighThe cold and moist air mass that is the basis of this high pressureOkhotsk Kaiki GroupThat.

    Around the same time, high pressures gained power over the oceans of the central Pacific Ocean, expanding their range to the west.This high pressure covers the North Pacific Ocean in a bandPacific highAt the western end of the city, also known as the Ogasawara High Pressure, the warm and moist air mass that forms the basis of thisOgasawara KidanThat.

    From late May to early June, Kyushu and Shikoku begin to be affected by the Baiu front.From around this time, the color of the conflict between the Okhotsk High and the North Pacific High became darker in the eastern part of the Baiu front.On the other hand, in North China, the Korean Peninsula, and eastern Japan, spring-like weather continues, with alternating high and low pressure systems.

    The rainy season front going north

    The Baiu front, which continues northward, will enter China in mid-June.Nanling MountainsIt stagnates in the vicinity, and in Japan it expands to the vicinity of Honshu.

    Next, the Baiu front is from China (Yangtze RiverBasin ・HuaiheGo north to the basin). In late June, South China and the Nansei Islands will leave the sphere of influence of the Baiu front. In July, the Tohoku region will also begin to rain, and the mainland areas of Japan, excluding Hokkaido, will begin full-scale long rains.Around the same time, the southern part of the Korean Peninsula also enters a period of long rain.

    After mid-July, a subtropical jet streamTibetan PlateauIt will flow northward, and the Okhotsk High will weaken as it joins.On the other hand, the Pacific High continues to cover the southern seas of Japan, and the sunny weather continues, and the rainy season is ending in order from the south on the mainland of Japan and the Korean Peninsula.

    The Baiu front, which has moved north in this way, eventually reaches North China and northeastern China, such as Beijing.Every year, the power of the front is weakening around this time, and although it may be cloudy, it is unlikely that the front will continue to stay.In addition, long rains after mid-August and late August are so-calledautumn rainThe name of the front also changes to the autumn rain front, but the air masses that make up the north-south air of the front are the same.[8]..However, autumn rain is rarely seen in mainland China.Even in western Japan, there is autumn rain, but the amount of rainfall is not so large.On the other hand, in eastern Japan and northern Japan (excluding Hokkaido), there is a tendency for more rainfall in the autumn rainy season than in the rainy season (however, the amount of rainfall in the autumn rainy season is higher.typhoonIncluding heavy rain).

    Nature of the Baiu front

    Two airs with different properties (air massWhere it hits, the atmospheric condition becomes unstable and a front is generated.Since the air masses that make up the Baiu front are all competing with each other, they slowly move north and south in almost the same area.Stagnation frontBecomes

    The two air masses that make up the south side of the Baiu front are both ocean-based air masses (marine air masses), so they absorb a large amount of water vapor from the ocean and have moist air.However, since the temperature difference between the air mass on the north side and the air mass on the south side is small, most of them are usuallyStratus cloudsConsists of weak rain clouds.Therefore, it rains for a long time, which is not very strong.

    However, cold air and dry air in the sky, typhoons and warm and moist air near the surface of the earth (Warm and humid flow) Inflows, the activity of the front line becomes active,CumulonimbusIt becomes a strong rain cloud accompanied by, and sometimes heavy rain.

    When the two high pressures are in conflict and the forces are almost balanced, the Baiu front hardly moves.However, when the two high-pressure forces are out of balance,(I.e.When a front approaches or a low pressure system occurs near the front, it may temporarily become a warm front or a cold front.The Baiu front is considered to be over when the activity of the Baiu front is weakened by the expansion of the Pacific High or pushed up to the north of each region and it will not rain due to the influence of the front in the future.

    Unspecified year with rainy season

    Depending on the year, the time of the rainy season may not be specified or announced.East / West Japan (especiallyShikoku region-Kinki-Hokuriku region), This pattern occurs once every few years.This is a pattern in which the Baiu front moves northward from the Hokuriku region due to the strong power of the Pacific High, rushes into the summer sky as it is, becomes a high pressure in the south, and gradually moves south ().Small summerAfter the small heat, the rainy season will end as it is).Even in this case, in the Shikoku region, Kinki region, and Hokuriku region, although the temperature and sunny weather are slightly higher, the "summer", in which the sunny weather continues, is coming.From this, it is said that the (real) summer in the Kinki region is longer than that in the Hokuriku region in some years.

    Unspecified year after the rainy season

    Depending on the year, the time of the end of the rainy season may not be specified or announced.[Note 2][2].Tohoku region(Especially the three northeastern prefectures of Aomori, Iwate, and Akita),Kanto Koshin regionThen this pattern occurs once every few years.this is,Due to the strong power of the Okhotsk High, the Baiu front could not move north from the Tohoku region and entered autumn as it was.autumn rainMost of the patterns are that the front gradually moves southward, or even if the Baiu front completely disappears from Honshu, there are many cloudy and rainy days, and the atmospheric conditions are unexpectedly unstable.Is (beginning of autumnThe long rain after the fall is defined as autumn rain).Even in this case, although the temperature and cloudy weather in northern Hokkaido are slightly higher, the "summer", in which the sunny weather continues, is coming.From this, it is said that the (real) summer in the Tohoku region is shorter than that in Hokkaido in some years.[Note 3].

    Asian monsoon and rainy season

    The Baiu front is meteorologicallymonsoonIt is one of the fronts (monsoon fronts) that bring about.IndiaIncludingSouth Asia,Southeast AsiaThe monsoon is caused by hot and humid air currents originating in the Indian Ocean and the Western Pacific Ocean.The region with the highest annual rainfall in the world (India)Cherrapunjee) Is included, and the monsoons in this area are the largest on the earth, and since they occur in a wide range in conjunction with each other, they are collectively called.Asian monsoonIs called.The area affected by this is called Monsoon Asia.

    The influence of the Asian monsoon extends further to the east,South China SeaIt also affects the tropical monsoon air mass that covers the area.Specifically, most of the rainy season in the Southwest Islands and South China is brought about by the tropical monsoon air mass, and the airflow that blows clockwise around the edge of the Pacific High makes the air affected by this tropical monsoon air mass Japan.・ Bring it to the vicinity of the Korean Peninsula to increase the rain.Given this relevance, meteorology generally includes most of the coastal areas of China, the Korean Peninsula, and the Japanese archipelago, where the rainy season occurs, in monsoon Asia.

    Also, looking at the atmosphere above the Baiu front, it is the boundary between the winter air and the spring / autumn air.Polar front, The boundary between the spring / autumn air and the summer airSubtropical frontAre close to each other, and the rainy season has a strong "seasonal transition" nature.

    Rainy season in various places



    Average period and average precipitation of the rainy season[2]
    RegionRainy seasonAfter the rainy seasonNumber of daysRepresentative point
    Okinawa regionAround June 5Around June 643 daysNaha
    Amami regionAround June 5Around June 649 daysAmami
    Southern KyushuAround June 5Around June 748 daysKagoshima
    Northern Kyushu60Around 4thAround June 746 daysFukuoka City
    Shikoku region60Around 5thAround June 743 daysTakamatsu
    Chugoku60Around 6thAround June 744 daysHiroshima city
    Kinki60Around 6thAround June 7Osaka
    Tokai region60Around 6thAround June 7Nagoya city
    Kanto / Koshin region60Around 7thAround June 743 daysChiyoda
    Hokuriku regionAround June 6Around June 7Niigata
    Southern Tohoku regionAround June 6Around June 7Sendai city
    Northern Tohoku regionAround June 6Around June 744 daysAomori
    Yamaguchi Prefecture belongs to northern Kyushu.

    In JapanLocal weather station-Japanese Meteorological AgencyHowever, the rainy season and the end of the rainy season are announced every year for each region that summarizes several prefectures (excluding Hokkaido).First of all, the day when the rainy season started and the rainy season seems to have ended (in the case of a holiday, the first since thenWeekday)Preliminary value", And according to the announcement, it is reported that" it seems that the rainy season has started "and" it seems that the rainy season has ended. "After that, the weather progress from May to August is comprehensively examined, and the final rainy season is set every September.Fixed valueWill be announced.At that time, the date of the rainy season and the end of the rainy season may be corrected in the preliminary figures, or the expression "not specified" may be used in the end.In general, the rainy season arrives earlier in the southern regions, with the average being from mid-May to late June in Okinawa and from late June to late July in Tohoku and Hokuriku.

    Announcements of the rainy season and the end of the rainy season are usually made as follows.Each meteorological observatory mainly estimates the "border" from early summer, when there is relatively much sunny weather, to cloudy and rainy season, based on the medium-term forecast up to one week later and the changes in the weather up to that point. Announced as a day.In short, when it is estimated that cloudy weather and rain will continue for the next few days or more in the jurisdiction, the first day will be the rainy season.In the case of the end of the rainy season, on the contrary, it is when the sunny days continue for several days or more.The basis for the medium-term forecast is the flow of the atmosphere over the jet stream, which has relatively few errors (Subtropical jet streamAnd the positional relationship of the Baiu front is good).However, if this medium-term forecast itself deviates, it will not be as announced and it will clear up.The announcement of the rainy season and the end of the rainy season does not announce that it has been confirmed, but it may be missed because it "contains forecasting elements" according to the Japan Meteorological Agency.

    However, the Baiu front remains stagnantbeginning of autumnAfter that, the end of the rainy season will not be announced.The fall season is just around the time when the Baiu front reaches the northernmost point every year, and after that, it is rather the fall rain season.However, even in this case, the next year will be the "rainy season" as usual, but it does not mean that "the rainy season will occur again over the course of a year without the end of the rainy season."In other words, if there is no end of the rainy season, we think that "the rainy season will shift to autumn without a clear summer weather."

    The announcement of the end of the rainy season is popularDeclaration of the end of the rainy seasonThat is.Basically, the end of the rainy season comes in order from south to north as the Baiu front moves north, but this may not always be the case.If the front remains in some areas, the rainy season may end earlier in the northern regions.In the past, the rain started earlierChugokuIt started raining laterHokuriku regionBut after the rainy season,Kanto regionAfter the rainy seasonWest JapanThere are cases where it is significantly delayed.

    At the end of the rainy seasonPacific highThe "marginal flow" that goes around the edge of the high pressure is strengthened by increasing the power of theWarm and humid flowIt is easy to get in, so it is easy to get heavy rain[10]..On the contrary, from the end of the rainy season to the beginning of August, "XNUMX days after the rainy seasonThe weather is often stable,Intense heatMay be hit by.

    The period of the rainy season is not so different from 40 to 50 days in any region, but the amount of precipitation during the period varies greatly.On the mainland, the number increases toward the west and south, with more Kanto / Tokai / Kinki than Tohoku, northern Kyushu than Kanto / Tokai / Kinki, and southern Kyushu than northern Kyushu.On the other hand, in the Nansei Islands, Naze has more rainfall during the period than Ishigaki Island and Naha, and overall the rainfall during the rainy season near Japan is the highest in southern Kyushu.[10].


    As the actual weatherHokkaidoAlsoDonanAlthough the Baiu front may occur mainly in Hokkaido, it is said that there is no Baiu in Hokkaido as an average weather, that is, climatologically.[11]..This is because at the end of the Baiu season when the Baiu front reaches Hokkaido, the power is weakening and the speed of moving north is increasing. Because.but,21st centuryLaterGlobal warmingIn recent years, there have been remarkable cases of guerrilla rainstorms and the Baiu front stagnation in the vicinity of Hokkaido while maintaining their power without weakening, mainly in the southwestern part of Hokkaido, after the record-breaking heat of 2010. Appeared in, especially in 2018,2022/In, heavy rain caused by the stagnation of the Baiu front, which was pushed up by the high pressure and moved north, caused flooding of rivers.AsahikawaThen, it caused the damage of the flooding of the river.Japanese Meteorological AgencyI did.in this wayHokkaido = The fact that there is no rainy season is a story of the pastIs becoming.

    Southwestern Pacific side of Hokkaido (Oshima-Iburi-Hidaka), Heavy rain may occur at the end of the rainy season in Honshu.In addition, low temperatures and lack of sunshine are likely to occur during this period in a wide area of ​​Hokkaido.KushiroEtc. in the eastSea fogIt is also in Tohoku and Kanto that the number of days increasesKoshinetsuLike the rainy season, it is affected by the Okhotsk Sea high pressure.[11]..In particular, the temporary low temperature seen mainly from the end of May to the beginning of June is a lira in Hokkaido.ラ イ ラ ッ ク) Is the time when the flowers bloomLira coldAlso called[Note 4][12][13]..In addition, the chilly weather like this may continue for about two weeks depending on the year, at the same time as the rainy season in Honshu.EzoSometimes called "rainy season"[14].

    Ogasawara Islands

    Ogasawara IslandsHowever, in May, which is the transition period from spring to summer, the fronts are not formed because the centers of the air masses are separated, and the rain does not last long.And since it enters the Pacific High area from around June, which is the beginning of summer, and is covered all the time, there is no rainy season here either.[15].


    中国中部・南部でも梅雨がみられる。中国では各都市の気象台が、梅雨入りと梅雨明けの発表をしている。ある研究では、1971年 - 2000年の各都市の梅雨入り・梅雨明けの平均値で、長江下流域の梅雨入りは6月14日、梅雨明けは7月10日、淮河流域の梅雨入りは6月18日、梅雨明けは7月11日となっている[8].

    As a guide, long rains due to the Meiyu front begin around mid-May in South China and end around late June.Over time, the region of long rain gradually moves to the north, and from mid-June to early July, East China (the middle and lower reaches of the Yangtze River), and from late June to late July, part of North China becomes a period of long rain. ..Each long rain lasts for about a month.

    Korean Peninsula

    Average period and average precipitation of the rainy season in each region of Korea[16]
    RegionRainy seasonAfter the rainy seasonNumber of daysPeriodic precipitation
    Chubu regionDecember 6-23December 7-2332 days238 - 398 mm
    Southern regionDecember 6-22December 7-22199 - 443 mm
    Jeju6/19December 7-2033 days328 - 449 mm

    On the Korean Peninsula, there is a long rainy season from late June to late July, which lasts for about a month.The longer the rain goes north, the less clear it becomes.[17].

    Characteristics of the rainy season weather

    May-June before the rainy season, the weather similar to the rainy season may be seen.Running rainy season(Hashirizuyu),Rainy season running(Tsuyu no Hashiri), orPick-up rainy seasonCalled (Mukaezuyu).

    At the beginning of the rainy season, it often rains relatively lightly.In the middle of the rainy season, there may be a period when the weather recovers.About this periodHolidays during the rainy season(Yasumi in the soup).

    During the rainy season, especially during long rains, the sunshine hours are short, so the temperature fluctuations (difference between maximum and minimum temperatures, daily range) are small, and you may feel chilly.This cold and weatherRainy season(Tsuyuzamu) orRainy season coldCalled (Tsuyubie).On the other hand, during the rainy season during the sunny seasonRainy seasonIt is called (tsuyubare) or the rainy season, and the temperature is particularly high and the humidity is high.Therefore, on a sunny day in the rainy seasonDiscomfort indexIs expensive and difficult to spendheatstrokeTends to occur easily.

    Rainfall often increases at the end of the rainy season, and sometimesTorrential rainMay become.This tendency is stronger in the south and west, and especially in Kyushu, rainfall for one year may fall in just one week at a rate of about once every ten years (at this time).Kumamoto-Miyazaki-Kagoshima OfKyushu mountain areaA typical example is along the mountain).Conversely, in eastern Japan such as Kanto and Tohoku, rather than during the rainy seasonautumn rainThere is more rainfall during this period.

    The rain at the end of the rainy seasonRainy season(Arazuyu) orRampage rainy seasonAlso called (Abarezuyu).Also, at the end of the rainy season, it often rains with lightning.Sending rainy seasonCalled (Okurizuyu).In addition, even after the rainy season, it may continue to rain, or it may rain once it has cleared up.thisReturn rainy season(Also written as Kaerizuyu and the rainy season) orReturn rainy seasonCalled (Return Zuyu).These expressions have become less popular in recent years.

    In the year when the end of the rainy season was delayedCold summerIn many cases,Cold injuryTends to occur easily.

    The rainy season is a time when both high temperature and high humidity are prominent in the Japanese season.Mold,Food poisoningCause ofBacteria-ウ イ ル スIt is said that it is a season that requires attention to these because the breeding of[3].

    Sky rainy season

    There may be little rain during the rainy season.About such a rainy seasonSky rainy seasonIt's called (Karatsuyu).In the case of the rainy season, the water used in the summer (especiallyRice cultivationrequired forAgricultural water) Can no longer be secured, often causing drought, especiallyAomori,Iwate,Akita OfNorth tohokuIn rural areas, the probability of rainy season is quite high, and the amount of precipitation from autumn to winter is low.Northern Kyushu,Setouchi regionIn such cases, after the rainy season, if there is no heavy rain due to a typhoon, drought may continue for more than a year.

    Negative / positive

    A rainy season that is not very strong and lasts for a long timeNegative rainy seasonWhen it rains, it rains a lot in a short period of time, and when it doesn't rain, it rains like a clear rainy season.Positive rainy seasonIt may also be expressed as.Negative rainy seasonWoman rainy season(Onnazuyu), positive rainy seasonMan rainy seasonSometimes called (Otokozuyu), in haikuSeason wordsMay be used as.

    The tendency is that if it is negative,Okhotsk Sea HighIs often strong, and if positive,Pacific highIs often strong,WesterliesFlow path andArctic oscillation-Southern vibration(ENSO,エ ル ニ ー ニ ョ-La Niña) Etc. are also involved.

    Relationship with typhoons

    typhoon,Tropical cyclone[18]While sucking air from the surroundings near the ground, it is several thousand meters to 1 meters above the ground.TroposphereIn the upper layer, the sucked air is moistened and released in large quantities to the surroundings.Therefore, when a typhoon or tropical cyclone approaches or lands near the Baiu front, the Baiu front, which is supplied with more and more water vapor, becomes active and causes heavy rain.In addition, the Baiu front may move north along with a weakened typhoon and extratropical cyclone, and the Baiu may end at once.

    Heavy rain pattern of the rainy season

    Heavy rain and heavy rain during the rainy season[19]Looking at the case of, it is said that there are some patterns in the pressure distribution and weather conditions.Sea of ​​Japan sideIt is easy to get heavy rainSea of ​​JapanNear the Baiu front that stagnates in the south(I.e. to East MalaysiaIn the pattern of going to low pressureSouthwestMoist air flows in from, and that airMountainsIt is easy to hit and cause localized heavy rain.

    Pacific Ocean sideHeavy rains are likely to occur in the pattern of long-term stagnation of the Baiu front and the pattern of stagnation of the Baiu front near the Pacific Ocean side and the low pressure system on the west side.south - SoutheastMoist air flows in from the mountain range, and the air also tends to hit the mountains and cause localized heavy rainfall.

    In addition, along the Baiu front (creating an elliptical cloud group)Precipitation cellIt is known that heavy rains are likely to occur when the parent cloud of cumulonimbus clouds, which is called), moves eastward.It is formed in mainland China and the East China Sea where the atmosphere above is dry, and often comes to Japan.

    Relationship with ocean change

    Statistically, seawater temperature rises in the central-eastern part of the Pacific Ocean near the equator and falls in the western part.エ ル ニ ー ニ ョWhen the phenomenon occurs, both the rainy season and the end of the rainy season tend to be delayed in various parts of Japan, and the rainfall tends to be normal and the sunshine hours tend to be long.[20]..Also, when the seawater temperature drops in the central-eastern part and rises in the western part, the rainy season tends to be earlier in some parts of Japan, except that the rainy season is delayed in Okinawa. Yes, the amount of precipitation tends to be high except for some, and the sunshine hours tend to be slightly short.[21].

    Disaster caused by the Baiu front


    Disaster nameDeadlineDisaster area
    Great Hanshin flood1938/7/3 - 5 daysKobe City
    28 West Japan Flood1953/6/25 - 29 daysNorthern Kyushu
    Nanki heavy rain1953/7/16 - 25 daysWakayama
    Early torrential rain1957/August 7- 28 daysNagasaki,Saga,Kumamoto
    36 Rainy season front heavy rain1961/6/24 -December 7Tokai,Hokuriku,Shin-Etsu,Kinki,Kyusyu,ChugokuA part of
    39 7 Mt. Gassan Yin Hokuriku Heavy Rain1964/7/17 - 20 daysSan'in district,Ishikawa,Toyama
    Heavy rain in July 421967/7/8 - 9 daysNagasaki Prefecture,Seto Inland SeaAlong the coast
    Heavy rain in July 471972/August 7- 15 daysHokkaidoとTohoku,Shikoku regionNationwide except for some
    Heavy rain1974/7/7 - 8thTokai region, Seto Inland Sea coast
    Heavy rain in July 57 (Nagasaki flood)1982/7/23 - 25thNagasaki prefecture, Kumamoto prefecture,Yamaguchi ,Saga Prefecture,Oita
    Heavy rain in July 581983/7/20 - 29 daysShimane , Tohoku, Hokuriku region
    7.11 flood damage1995/7/11 - 12 daysNiigata,Nagano,Toyama
    6.29 Heavy rain disaster1999/6/23 -December 7Fukuoka CityFlooded in the center,HiroshimaSediment disaster
    2003/August 7- 17 daysKyushu region, Sanin region, Hokuriku region
    Heavy rain in late July 152003 late 7Kyushu region, Kumamoto prefectureMinamataでEarth and stone flow
    July 16 Heavy rainfall in Niigata and Fukushima2004/7/12 - 14 daysNiigata,Fukushima
    July 16 Heavy rain in FukuiOctober 2004, 7- 18 daysFukui,Gifu
    Heisei 18 year 7 month heavy rain2006/August 7- 24 daysKyushu region, Sanin region, Hokuriku region,Nagano
    July 21 Heavy rain in northern China and Kyushu2009/August 7- 26 daysNorthern Kyushu,ChugokuWestern part
    July 23 Heavy rainfall in Niigata and Fukushima2011/7/26 - 30 daysNiigata,Fukushima
    24 rainy season front heavy rain2012/February 7, 3, 12Oita,Fukuoka,Kumamoto
    July 24 Heavy rain in northern KyushuOctober 2012, 7- 14 daysNorthern part of Kyushu region (Kumamoto prefecture, Oita prefecture, Fukuoka prefecture)
    July 29 Heavy rain in northern Kyushu2017/6/30 - 7/10Northern Kyushu (Fukuoka and Oita prefectures)
    Heisei 30 year 7 month heavy rain2018/7/5 - 7 daysKyushu region, Chugoku region, Shikoku region, Kinki region, etc.
    July 2nd year of heavy rain2020/7/4 -Kyushu region, Chugoku region, Shikoku region, Kinki region, etc.
    [22]2022/6/27 - 7/1Tohoku region Sea of ​​Japan side (Yamagata,Akita,AomoriSea of ​​Japan side), Hokkaido

    Meteorological record of the rainy season

    • Up to 1 hour precipitation
    • Maximum annual rainfall
      • 8670.0mm- MiyazakiEbino(1993/, No. 1 in the history of observation of all observation points in Japan) --This year, the rainy season started on May 5, and the rainy season ended in the middle to the end of July in normal years, but the rainy season continued even in August. On the contrary, since the rainy season had not yet ended on August 17, after the basin, the end of the rainy season was "unspecified", 7 mm in May, 8 mm in June, and 8 in July during the rainy season. It rained mm, 31 mm in August (from the rainy season to the end of August, it rained more than the average annual rainfall. The average annual rainfall was 5 mm). The number of years in which the rainy season continued in August is extremely small in the history of observation.

    Purpose of the rainy season forecast

    The Japan Meteorological Agency started to provide information on the rainy season and the end of the rainy season.1955/I was about to contact the news media as a "notice"[23][24]..It was the one that started to announce as weather information1986/Since[23].

    By announcing the rainy season, we will raise awareness of disaster prevention by notifying "rainy season" as a time when weather that is likely to lead to floods and sediment-related disasters such as long rains and heavy rains occurs frequently.[23]By notifying the time of "rainy season" where heavy rain and high temperature and humidity continue for a long time, it is easy to take measures in terms of life and economy, and by notifying the start and end of a kind of season called "rainy season", the sense of season is clarified. To (First in spring,Dead tree,ChuxueThe same role as the announcement) is expected.

    Culture related to the rainy season


    • Commelina communis(Asiatic dayflower)
    • Tsuyuaoi(Aoi rainy season)
    • Hydrangea --A typical flower that blooms during the rainy season.It often appears when expressing the rainy season.


    俳 句

    • Collect the May rain and make it early Mogami River (Matsuo Basho)
    • Two houses in front of the May rain and the big river (Yosano Village)

    Similar meteorological phenomenon

    Rapeseed rainy season
    The cold rainfall that continues every day from the end of March to the beginning of April, mainlyRape blossomIt is called "rapeseed rainy season" because it falls when it blooms.It rarely rains for days like the rainy season, and it is rare to see torrential rains, but after all, there are many cloudy and rainy days, and unclear weather often continues for days.
    Also,"Long rain in spring"Or"Spring haze(Shunrin) ","Flower rain(Saikau) "[25].. "Kasumi" in "Spring Kasumi" is a Chinese character that stands for long rain.Spring:Represents a long rain[26].. "Flower rain" isCherry BlossomsIt means rain that holds (blooms) various flowers including[25].. "Harusame" is often referred to as the rain around this time.Moon-shaped half flatThe name "Spring rain, let's get wet" also sounds stylish because it is a soft spring rain that makes the buds of plants grow and flowers bloom.[25].
    Incidentally,NHKWhen I say "rapeseed rainy season", I always give an explanation.[25].
    Winter:The continent that dominated the vicinity of Honshu during the period(I.e.Overhangs and the path of mobile highs are biased north, while cold and humid northeasterly air currents along the southern edge of the northern highs overhang (Stop) Blows or the front tends to stagnate along the south coast of Honshu.[27]..At that time, it is also characteristic that it tends to occur frequently on the south bank.Therefore, it is often said to the Pacific coast of western and eastern Japan, and this phenomenon is not seen in northern Japan.In recent yearsWarm winterTrends andGlobal warmingDue to the influence of the rapeseed rainy season, there is a tendency for the rainy season to rise in winter, and there are concerns about climate change.
    In addition, the rapeseed rainy season does not last as long as the rainy season, and the period is usually all day or several days.[28].
    For example,1990/February was cloudy and rainy, mainly in the latter half of the month, and the monthly sunshine hours in Tokyo were only 2 hours, which seemed to symbolize a warm winter.again,1985/In March, cold rains continued throughout the month in the Pacific region west of Kanto, and in Tokyo in the same year.(I.e.0 days (first worst record except June and July during the rainy season),Japan Weather AssociationIn the published weather map diary, it was described as "dark March".In addition,1986/,1988/,1991/,1992/,1995/,1999/Because March was relatively long and cloudy and rainy weather continued, the monthly sunshine hours were quite short except in northern Japan.20st centuryIn March toward the end, "There is no sun on the rape blossoms", "Moon of holidays and demons", "Rain gear such as umbrellas are essential for cherry blossom viewing", "Graduation ceremony, closing ceremony, departure ceremony are always rainy" etc. There was also a disgraceful label.In addition,2002/,2006/From the end of February to the beginning of March, the south bank front stagnated, and the sky that was easy to rain in the morning and evening continued, and some weather casters said that it was a "rapeseed rainy season run?" bottom.
    Running rainy season
    It mainly refers to the state where it continues to rain from the end of May, like the rainy season.Just at that timeUnion flowerWhen it blooms, it rains like rotting the flowers of the bean curd refuse.Okara rotten(It's gone) ”. "Running" means "pioneer", and "running rainy season" may be interpreted as rain that continues to fall prior to the rainy season. Also known as the "rainy season run".OkinawaIt is in the rainy season of the Nansei Islands, and is near the Nansei Islands.Rainy season frontIs often seen when temporarily moving north along the southern coast of Honshu.Also,Okhotsk Sea HighAppears in the first half of MayNortheast airflowThe temperature and cloudy weather may continue for a long time on the Pacific side north of Kanto because it is easily affected by.In addition,MaystormDeveloped to pass through the Sea of ​​Japan and northern Japan(I.e.Extend to the backCold frontDominates the South Sea after passing through Honshu and reaching the Pacific Ocean side(I.e.Along the north side ofStagnation frontIn this case, the weather continues for a while on the Pacific side, mainly on the Pacific coast of eastern Japan.
    autumn rain[29]
    It mainly refers to the period of long rain that continues to fall from the latter half of August to around October (the time varies depending on the region). "autumn rain(Shurin) ","thin(Susuki)rainy seasonAlso called.
    Sasanqua rainy season[29]
    The continuous rainfall from late November to early December is called "Sasanqua rainy season".SasanquaIt has this name because it falls when it blooms.


    [How to use footnotes]

    注 釈

    1. ^ a b The source of the rainy season frontConvection((I.e.) Is of the atmosphereEquivalent temperatureThe larger the reduction rate of θe, the stronger it becomes.Atmospherictemperature,(I.e.The higher the value, the larger the θe. Therefore, the lapse rate of θe in the atmosphere increases due to the collision of air masses with dry and wet properties, or cold and warm properties, and clouds on the front are likely to occur.
    2. ^ In 2004, it was decided not to announce (specify) the end of the rainy season if the rainy season has not yet ended even after the second day of the fall.If the rainy season does not end as of August 2, there will be no end of the rainy season (the treatment is the same as without specifying the end of the rainy season).By the way, there are many times when the rainy season is not specified, but the rainy season is the only one at the moment in 8. In the record long rain of 31, the rainy season outside Okinawa and Hokkaido became the rainy season in August (the rainy season in August occurs frequently).Aomori-Iwate-Akita OfNorth tohokuExcept for 3 prefectures, it is extremely rare in the history of observation), and the rainy season continued for more than two and a half months, so the time after the rainy season was not specified.
    3. ^ However, in the year of this pattern, Hokkaido also tends to be cold, humid, and rainy, and even in August, not only the lowest temperature often falls below 8 degrees Celsius, but also the amount of precipitation in summer is higher than normal. It may increase, and depending on the year, it may be on the front line orWet and warm currentIt is not uncommon for long-term heavy rains and torrential rains to occur.
    4. ^ In addition, "Rila cold" is a word that has been known since the 1970s, and the one used by the poet Mieko Harutani for haiku for the first time is used.Tatsuichi TsujiiIntroduced in the book, it is even moreJunichi WatanabeIt is said that it became popular as a result of being quoted by the novel "Rila Cold Town" and being made into a TV drama.


    1. ^ a b c d e f g h i Keyword weather encyclopedia, Susumu Kato "Rainy season" pages 221-226
    2. ^ a b “Summer (June-August) weather” (PDF) (Press Release), Japanese Meteorological Agency, (March 2021, 9), https://www.data.jma.go.jp/obd/stats/data/stat/tenko2021jja_besshi.pdf 2021/9/2Browse. 
    3. ^ a b Yahoo! Encyclopedia "Baiu"
    4. ^ Ninomiya, pp. 81-84
    5. ^ Kozo Ninomiya, Heavy Rain and Precipitation System, pp. 121-122, Tokyodo Publishing, 2001 ISBN-4 490-20435-3
    6. ^ Totetsu Kinoe, edited by Mitsuru Maeda, "Classification Okinagarabejima Folklore", p258, 2011, Kagoshima, Nanpo Shinsha,ISBN 978-4-86124-209-0
    7. ^ Ichiro Iwakura, "Kikaijima Dialects" p192, 1941, Tokyo, Chuokoron-sha
    8. ^ a b c K.Iwata (June 2005, 6). “Chinese Pit 026 [Deume]". Chinese learning notes.As of August 2009, 8originalMore archives.2009/6/11Browse.
    9. ^ "Entering the rainy season and the end of the rainy season after 26 (confirmed value)". Weather statisticsJapan Meteorological Agency. 2021/9/2Browse.
    10. ^ a b Meteorological Forecaster Handbook, 2008, §1-3-2
    11. ^ a b Meteorological Forecaster Handbook, 2008, §1-3-5
    12. ^ "Mieko Harutani: A poet with the seasonal word "Rila cold", she slept at the age of 1 in January, and thought she entrusted her with fragrant flowers / HokkaidoMainichi Shimbun, May 2013, 5 Hokkaido Edition
    13. ^ Hideo Toyoshima "Words (Broadcasting Term)> Questions on Broadcasting Sites / Questions on Viewers> Is it the same as "Rila cold" in Hokkaido and "Flower cold" in Honshu?, NHK Broadcasting Culture Research Institute, May 1999, 5
    14. ^ "Ezo rainy season? Rain and cloudy weather in Hokkaido for 11 consecutive days in Sapporo". Hokkaido Shimbun (The Hokkaido Shimbun Press). (June 2014, 6). originalArchived as of October 2014, 7.. https://web.archive.org/web/20140714160247/http://www.hokkaido-np.co.jp/news/topic/545685.html 
    15. ^ Masamitsu Morita (October 1999, 8). “Is there a rainy season in Ogasawara?". Is it Morita's weather?. TBS TV.As of August 2009, 8originalMore archives.2009/8/16Browse.
    16. ^ “장마 의 시작과 끝 (평년값) (normal value at the start and end of the rainy season)” (html) (press release), Korea Meteorological Agency, (March 2009, 5), https://data.kma.go.kr/climate/rainySeason/selectRainySeasonList.do?pgmNo=120 2021/3/5Browse. 
    17. ^ (October 2006, 5). “Is there a "rainy season" in Korea?". Korean learned from the seasons. All About.As of August 2009, 8originalMore archives.2009/6/11Browse.
    18. ^ Let's listen to the voice of the earth "Let's predict the course of the typhoon!"
    19. ^ Let's listen to the voice of the earth "Protect yourself from torrential rain!"
    20. ^ "Characteristics of Japanese weather associated with the El Nino phenomenon". Data on the El Nino / La Nina phenomenonJapan Meteorological Agency. 2007/6/29Browse.
    21. ^ "Characteristics of Japanese weather associated with the La Nina phenomenon". Data on the El Nino / La Nina phenomenonJapan Meteorological Agency. 2007/6/29Browse.
    22. ^ [1]
    23. ^ a b c “What is the rainy season? (3) High interest in the“ rainy season ”that makes the best use of it”. asahi.com (Asahi Shimbun). (November 2005, 6). http://www.asahi.com/special/june2005/TKY200506130497.html 2017/6/7Browse. 
    24. ^ Kaoru Asano "Weather Uncle Uchiakewa" Ie no Hikari Association (Original, July 1981), p. 7.ASIN B000J7XODO. 
    25. ^ a b c d ""Spring long rain" and "rapeseed rainy season" have the same meaning? | Words (broadcasting terms) --Broadcasting site questions / viewer questions | NHK Broadcasting Culture Research Institute". www.nhk.or.jp. 2020/5/31Browse.
    26. ^ "What is the rapeseed rainy season? What is the meaning, origin, and difference from the rainy season? | Beyond”(Japanese). Beyond (September 2018, 11). 2020/5/31Browse.
    27. ^ Japanese Language Dictionary, Mention in the World Encyclopedia, Britannica International Encyclopedia Subitem Encyclopedia, Digital Daijisen, Tossa's Japanese Convenience Book, Daijirin XNUMXrd Edition, Japan Encyclopedia Complete Book (Nipponica), Selected Edition.What is rapeseed rainy season?”(Japanese). Koto bank. 2020/5/31Browse.
    28. ^ "What is the rapeseed rainy season? What is the meaning, origin, and difference from the rainy season? | Beyond”(Japanese). Beyond (September 2018, 11). 2020/5/31Browse.
    29. ^ a b "Various rainy seasons (rapeseed rainy season)". www5e.biglobe.ne.jp. 2020/5/31Browse.


    • Yasumasa Kodama, Hiroyuki Yamada "Rainy season in Asia / Rainy season in the world", "Weather" Vol. 54, No. 6,Japan Meteorological Society, 7-10 pages, June 2007 NOT 110006317416
    • Takashi Nitta, Tomoyuki Ito, Ryuji Kimura, Tadashi Sumi, Tetsuzo Anari (ed.) "Keyword Meteorological Encyclopedia", Asakura Shoten, 2002 ISBN-4 254-16115-8
    • Japan Weather Forecasters Association (ed.) "Weather Forecasters Handbook", Ohmsha, 2008 ISBN 978-4-274-20635-1
    • "Rainy season, Yahoo! Encyclopedia (Encyclopedia Nipponica), Shogakukan, viewed September 2013, 9[Broken link]

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