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🌤 | The reason why there was no snow in central Tokyo


The reason why there was no snow in central Tokyo

If you write the contents roughly
The cold rain that is falling in western Japan is also rising from the west, and it seems that there will be sunny days in northern Japan.

In the Kanto Koshin region, snowfall of XNUMX cm is expected even in the XNUMX wards of Tokyo, and the Japan Meteorological Agency says that there is a risk of heavy snowfall mainly along the mountains and inland. → Continue reading

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Wikipedia related words

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Precipitation process

Precipitation processWhat is (precipitation process)?atmosphereから(I.e.The mechanism by which is generated until it falls.ocean-Lake-LandFromevaporation officialwater vaporIs contained in the atmosphere(I.e.And in the cloudsWater droplets,ice crystalsIs growing,(I.e.,snowIn the form ofprecipitationRefers to a series of processes untilAlso, during this process(I.e.It also includes those that appear in the weather on the ground.

The precipitation process is roughly divided into two stages.Also, the state of water during the precipitation process (phase.solidOrliquidThere are two types of causes, and three types of causes.

History of elucidation of precipitation process

It was in the early 20th century that the mechanism of the precipitation process, which is still valid, was elucidated.Belcheron Findesen's theory(Bergeron Findeisen process) orIce crystal theoryIt is called "cold rain"RaindropsThe formation mechanism of

ドイツ OfGeophysicist-MeteorologistAlfred WegenerIt is,WedDoes not freeze even if the temperature is below 0 ° CSupercoolingThe existence of the state (the supercooling phenomenon itself was also in Germany before thatGabriel FahrenheitThe theory is that the saturated water vapor pressure is higher around the water droplets than around the ice crystals, and that the ice crystals attract water vapor in the air.1911年Announced in.

I proved thisスウェーデンMeteorologistThor bercheronIs.He,(I.e.Wrapped inFir OfWoodsSo, I discovered that when the temperature is below 0 degrees Celsius, rime is formed on the trees and the fog clears only between the trees, and when the temperature is above 0 degrees Celsius, the fog also enters between the trees.This is because the fog that enters between the trees when the temperature is below 0 degrees Celsius is supercooled, and the fog evaporates due to the difference in saturated water vapor pressure and is used for the growth of hoarfrost, which clears the fog only in the forest. Think,1933年Water droplets and ice crystals in the cloudsCloud drop) Was published.And the German physicist Findesen (Findeisen) Revised this theory to explain the process of growth into raindrops.

After that, it was found that there were raindrops that grew without forming ice crystals, and the previous theory was distinguished as "cold rain" and rain that did not form ice crystals as "warm rain". The mechanism of "warm rain" was first published in a treatise.AmericaWoodcock (Woodcock).He is in the air at seaSea salt particlesWe thought that (aerosol with a large size) existed, observed this, and clarified the relationship with the growth of raindrops with the help of joint research with other researchers.

Precipitation process

Condensation process

The water vapor that is the source of the clouds condenses more and moreCloud dropThe process of becomingCondensation process(Condensation process) orDiffusion processIt's called (spreading process).Simply put, it is the process of cloud formation.

Clouds are generally cooled or supplied with water vapor,SupersaturatedReached (Saturated water vapor amountIt can be formed in air (containing the above water vapor).However, in order for clouds to form, in the airCloud nucleus(Condensation nucleus,Sublimation nucleus) Must be present.Without this, even if supersaturation is reached, water vapor willCondensationNo, no clouds.The atmosphere in many parts of the earth contains not a few cloud nuclei, and clouds form at a supersaturation degree of about 1%.

What is cloud nucleus?aerosolIt is a fine particle called.HygroscopicSome aerosols act as condensation nuclei, and water droplets condense on their surface.It also acts as a sublimation nucleus, with ice crystals on its surface.SublimationThere are aerosols that do, but hygroscopicity is not so relevant for this aerosol.These aerosols are widely suspended in the Earth's atmosphere, although their concentrations vary by region and altitude.

After the first water droplets condense or ice crystals sublimate on the cloud nucleus, other water droplets and ice crystals continue to condense and sublimate for a while.At this time, different growth is achieved depending on the temperature of the air and the state of cloud particles (when water droplets condense for the first time or when ice crystals sublimate, these are called cloud particles).

The temperature is 0 degrees (freezing point,Freezing point.(I.e.Above a certain level (constant regardless of change), all cloud particles are water droplets.At this time,Saturated water vapor pressureHowever, the growth rate of water droplets is very slow because there is almost no difference in any place.Therefore, in order for the water droplets to grow further, it is necessary to go through the following merging process.Clouds and fog are floating in the air without going through the merging process.

Even if the temperature is below 0 degrees, in the range of 0 to -40 degrees, water droplets will not meet if certain conditions are not met.SupercoolingRemains.Certain conditions are in air or supercooled water droplets.Ice nucleiIs to exist.There are four types of ice nuclei.Sublimation nuclei in which water vapor sublimates into ice crystals as they are, non-moisture-absorbing frozen nuclei that are taken into water droplets and frozen, condensed frozen nuclei that function as both condensation nuclei and frozen nuclei, and freeze by colliding with water droplets Non-moisture-absorbing collision condensation nuclei.

If there are even a few ice crystals, even if there is a large amount of supercooling around them, the ice crystals will grow rapidly by a certain mechanism.The mechanism is that there is a difference in saturated water vapor pressure around the ice crystals and around the supercooled water droplets (the pressure is higher around the supercooled water droplets), which makes it easier for the supercooled water droplets to evaporate and evaporate. The water vapor is sublimated around the ice crystals and grows steadily.thisRimingIt is called (riming).During this growth, the ice crystals form snow with unique shapes.

As a result, cloud particles that were very small grow rapidly and large, but as they grow, the supply of water vapor decreases, and the growth rate also slows down.However, by this time, cloud particles often have grown to a certain size, and move on to the next merger process.

Merge process

Cloud dropThe process of gathering and growingMerge processIt's called (coalescence process).

Growing to a sufficient size and floating itselfUpdraftThe cloud particles, which weigh more than the force of, gradually begin to fall.At this time, a large amount of cloud particles are present, but their sizes vary.Large grains fall quickly.For this reason, large cloud particles collide with smaller cloud particles when they fall, and if they are water droplets, they become one large water droplet, and if they are ice crystals, they evaporate the supercooled water droplets and sublimate the water vapor while growing larger. I will go.

On the other hand, for example熱 帯Consider the case of sea air.The amount of water vapor contained in the air is very large, there are many cloud particles formed by huge condensation nuclei, and the amount of saturated water vapor decreases at a large rate due to a strong updraft (= the amount of water vapor that becomes cloud particles is Much more).Therefore, the size of cloud particles that have undergone the condensation process becomes uniformly large, and the merging of water droplets proceeds efficiently.As a result, in the tropics, the time from cloud formation to rain is short, and the grains are large despite the warm rain.

In addition, the wind in the sky is not always constant and may become stronger, and the falling grains rise again.At this time, cloud particles that are initially ice crystals and melt into water droplets during the fall freeze again when they rise again.The same applies when air with a temperature of around 0 ° C is alternately distributed regardless of whether it rises or falls.When this is repeated, the grains become even larger as they condense and sublimate on the surface of the grains and other grains stick to each other.When this falls(I.e.,(I.e.become.

However, if the size of cloud particles is too large, they will lose their shape and split, making it difficult to produce extremely large particles.Water droplets tend to split when they exceed 3 mm.Of the ice crystals, if the snow crystals become too large, they tend to split.On the other hand, even with the same ice crystals, hail, hail,Freezing rainEtc. are hard and difficult to divide.

In this way, it finally falls on the ground.

Cause of precipitation

Warm rain

A liquid state from the beginning to the end that undergoes a precipitation process, and then a "warm cloud" to a "warm rain".Those that do not go through a solid state.

For example,熱 帯Consider the case of sea air.The amount of water vapor contained in the air is very large, there are many cloud particles formed by huge condensation nuclei, and the amount of saturated water vapor decreases at a large rate due to a strong updraft (= clouds among the water vapor in the air). The amount of particles separated is much larger).Then, even without rimming, the growth in the coagulation process becomes faster.

If it grows remarkably during the condensation process, large cloud particles are formed uniformly as described above.Then, the growth in the merger process is also large.This is due to the relationship between the distribution of cloud particles in the cloud by size and the collision rate.Radius is 5uM以下の小さな雲粒はほとんど併合せず、10μm以上の雲粒多数と20μm以上の雲粒少数であれば衝突率は10%、15μm以上の雲粒多数と30μm以上の雲粒少数であれば衝突率は50%、15μm以上の雲粒多数と30μmを大きく超える雲粒少数であれば衝突率はほぼ100%と考えられている。さらに他の研究により、30μm以上の雲粒ができなくても、20μm以上の雲粒同士の衝突により大きな雲粒ができるという報告もあるが、詳しく分かっていない部分もある。

Therefore, if such conditions are met, cloud particles will grow rapidly and become large raindrops.On the other hand, if the growth in the coagulation process is poor, it hardly grows.In other words, if the amount of water vapor in the atmosphere is large or the amount of air rise is large, it is likely to cause heavy rain, but vice versa.

When warm clouds form and stay near the surface of the earth, there is almost no growth in both the condensation process and the merging process, so the cloud particle size remains almost unchanged and becomes fog.If this happens in the sky, it will become hard-to-disappear clouds such as stratus and altostratus.Cumulus clouds in the early stages of growth are also "warm clouds", but they often appear in fine weather and easily re-evaporate, so they easily disappear.

cold rain

It may become liquid on the way, but mainly in the solid state, it goes through the precipitation process, and then it falls from "cold cloud" to "cold rain", ice particles, and snow.

In the case of cold clouds, it grows well during the condensation process and further during the merging process.However, the growth of ice crystals in the merge process is not so remarkable.

When cloud particles fall from cold rain without melting, it becomes snow.When this begins to melt and it falls with a mixture of snow and rain(I.e.When it melts completely(I.e..

If there are ice nuclei in the air and the temperature is below 0 degrees, it will not become a cloud.æ°· æ°·May fall.For thisWindWith or without(I.e.Etc. are also involved.

When the fog consisting of supercooled water droplets becomes cold below -30 degrees Celsius, freezing begins even if there are few ice nuclei.ice fogWill be.Also, the supercooled fog is on the ground.HoarfrostMay occur.

Warm rain of supercooling

After going through the precipitation process in a supercooled state from the beginning to the end,Supercooled water cloud From (supercooled water cloud)Supercooled rain (supercooled rain) falls.Supercooled warm rain.

Although it is a very rare case, even if there are condensation nuclei in the air, there are few ice nuclei, and when the temperature is 0 degrees or less, water vapor condenses as supercooled water droplets, which undergo the supercooling process and become excessive. It becomes a cooling mist,Supercooled rainThere is something that falls as.This is not the most common cause of supercooled fog and rain.It is intermediate between warm rain and cold rain, and since supercooling is a liquid, it is barely included in warm clouds and warm rain.


Related article

West Japan

West Japan(Ninin, Nichinon) isJapanIs a term used to roughly divideWestPoint to half. The antonym isEast Japan.

範 囲

Generally, it is a collective term for Kinki, Chugoku, Shikoku, and Kyushu.[Annotation 1][Annotation 2].

WidelyChubu regionIncluding[3]In addition, it may refer to the Chugoku region, Shikoku region, Kyushu/Okinawa region excluding the Kinki region. Also from KyushuSouth KyushuとNansei Islands[Annotation 3] TheSouthern JapanThere is an example.Eastern countryAgainstWestern country(Example:Nishinippon broadcasting), Kinki region (especiallyKinai) Kyushu region (especiallyNorthern Kyushu, Example:West Japan Railway)[5] AndKanto region(EspeciallySouth Kanto) To the Kinki region (especially Kinai) sometimes.

In the field of geology,Fossa MagnaFrom Itoigawa to Himekawa, Aoki Lake, Matsumoto Basin, Shiojiri, Kamanashi River, Hayakawa, and west of Fuji River to western Japan (Southwest JapanWith)[6][7][8] If there is a theory,Itoigawa Shizuoka Structural LineThere is also a theory that the west is western Japan.

In terms of various cultures, it refers to the west of Toyama, Gifu, and Aichi prefectures.[9][10].. In dialectologyWestern Japanese dialect(Western dialect)Hokuriku dialect-Kinki dialect-Shikoku dialect-Chinese dialect-Unhaku dialectTo point to (Tojo Misao)[11],Gifu/Aichi dialectIf is included in western Japan (Toshio Tsuchi)[12],Kyushu dialectIncluding Western Japan (Mitsuo Okumura)[13] and so on.

Japanese Meteorological AgencyIn Japan, the Japanese archipelago is divided into four regions: northern Japan, eastern Japan, western Japan and Amami, Okinawa. When saying “Western Japan” in the weather forecast, it means Kinki, Chugoku, Shikoku, and Kyushu excluding Mie Prefecture.[14].

BiotaThere are also things that are divided in east and west, for exampleRed mouseIs a group of chromosomesToyama-浜 松Divide into east and west at the line[15].

Names of major companies and organizations bearing Western Japan

There are two ways to read it: "Nishonhon" and "Nishikopin".

  • “Yomi” indicates the reading of “West Japan”.
  • In the “establishment date, etc.”, “(rename)” indicates the date when the name was changed to include the name “West Japan”.
Company/Group namereadingHead office locationDate of establishment, etc.Overview
West Japan Railway CompanyLtd.NishinihonOsakaOsaka1987/4/1Popular nameJR West Japan.. The business area is the Hokuriku region (Niigata TheHokuriku Shinkansenas well as the Oito lineOnly), Kinki region (Tokaido Shinkansenexcept for.Mie TheKansai Main LineShimagahara Station - Kameyama StationOnly), Chugoku region,NaganoPart ofFukuoka OfSanyo Shinkansen-Hakata Minami Line.
West Japan JR BusLtd.NishinihonOsaka-shi, Osaka1988/3/1JR West Group
West Nippon Telegraph and TelephoneLtd.NipponOsaka-shi, Osaka1999/7/1Popular nameNTT West.. The business area is Toyama (Tateyama(Excluding some areas), Gifu prefecture, west of Aichi prefecture andShizuoka(AtamiとSusono CityExcept for some areas).
West Japan ExpresswayLtd.NishinihonOsaka-shi, Osaka2005/10/1Popular nameNEXCO West Japan.. The business area is west of Kinki region (excluding Mie prefecture) and part of Fukui prefecture.
West Japan Construction Industry Guarantee Co., Ltd.NishinihonOsaka-shi, Osaka1952/11/6Public works advance payment guarantee businessRun. We can handle prepayment guarantees for public contractors nationwide, but the business storesKyoto,Shiga,Nara,WakayamaWest of eachPrefectural office location(However, due to competition measuresTokyoChuo-kuTokyo branch,Nagoya cityNakamura WardEstablished Nagoya branch, respectively).
Maxvalu West JapanLtd.NishinihonHiroshimaHiroshima cityMay 2000 (Renamed)AEON group.MaxvaluOperates stores in Kinki and Chushikoku area.
Nishinippon broadcastingLtd.NipponKagawaTakamatsuOctober 1956, 10 (Renamed)AbbreviationRNC.tv set-radioCombined bureau. As for the radio, Kagawa Prefecture broadcasts the area, TV (NTV series) Is with Kagawa PrefectureOkayamaIs the target area for broadcasting.
West Japan RailwayLtd.NipponFukuokaFukuoka CityOctober 1942, 9 (Renamed)Popular nameNishitetsu.Major private railwayCompany.
Ltd.TV West JapanNipponFukuoka Prefecture Fukuoka Prefecture1958/4/1AbbreviationTNC.. Fukuoka Prefecture is targeted for broadcastingTV station(Fuji TV series).
Ltd.West Japan City BankNipponFukuoka Prefecture Fukuoka Prefecture1944/12/1[Annotation 4]Fukuoka Prefecture (first)Local bank.
West Japan FoodLtd.NipponFukuoka Prefecture Fukuoka Prefecture2002/10Nippon HamGroup meat sales company.
West Japan Institute of TechnologyNipponFukuokaKanda Town1967å¹´ 
Ltd.West Japan ShimbunNipponFukuoka Prefecture Fukuoka Prefecture1942/8A newspaper company in Fukuoka Prefecture.West Japan Newspaper,West Japan SportsPublisher of (West Sports).
West Japan Junior CollegeNipponFukuoka Prefecture Fukuoka Prefecture1959/4 
West Japan Junior College High SchoolNipponFukuokaYame city1962å¹´ 
West Nippon Electric CableLtd.NipponOitaOita City1950/5/24Abbreviation isNishiden.
Western japan termiteNipponKagoshimaKagoshima1960/11/10[Annotation 5]Exterminator.
Companies/organizations that do not exist or have stopped using the term "West Japan"
West Japan Body IndustryLtd.NipponFukuokaKitakyushu1946/10/1Popular nameNishiko.. A bus body maker under the umbrella of West Japan Railway, which once existed. Dissolved on October 2010, 10.
West Japan PiratesNipponFukuoka Prefecture Fukuoka Prefecture1950å¹´Formerly under the umbrella of Nishinihon ShimbunProfessional baseballteam. The company name is "West Japan Baseball Co., Ltd."
West Japan System Construction Co., Ltd.NipponKumamotoKumamoto-shi1954/9/10construction company. Ltd. on October 2014, 10SYSKENRenamed to.

Names derived from western Japan or synonyms

Other Western Japan


[How to use footnotes]

注 釈

  1. ^ It is a "generic term for Kinki, Chugoku, Shikoku, and Kyushu."[1].
  2. ^ Usually four regions of Kinki, Chugoku, Shikoku and Kyushu[2].
  3. ^ Nansei IslandsIt is,Osumi Islands,Tokara Islands,Amami Islands,Okinawa Islands(Daito IslandsIncluding) andSakishima Islands(Miyako Islands,Yaeyama Islandsas well as the 尖 閣 諸島Generic name)[4].
  4. ^ Founded as West Japan.
  5. ^ Established as West Japan termite extermination preventive construction office.


  1. ^ "Concise Japanese Geographic Names Dictionary", December 1989, 12rd edition."West Japan" 1 item.
  2. ^ Takashi Akiba "Land Japonica, Encyclopedia of Japanese Places" December 1996."West Japan" item.
  3. ^ "Kojien 5th Edition" October 1999."West Japan" item.
  4. ^ "Concise Japanese Geographic Names Dictionary", December 1989, 12rd edition."Nansei Islands", "Ryukyu Islands" and "Sakishima Islands"
  5. ^ Daijirin, 1989. (1) of item (XNUMX) of western country
  6. ^ "Concise Japanese Geographic Names Dictionary", December 1989, 12rd edition."West Japan" ② item.
  7. ^ Junior high school course of study commentary society - Wayback machine(For archived July 2014, 7) Ministry of Education, Culture, Sports, Science and Technology. P12.
  8. ^ Tokyo Gakugei University FY2010 Priority Research Development Report of "Primary School Social Studies" Education Program in Teacher Training Course - Wayback machine(Archive for April 2014, 4) Tokyo Gakugei University. P24.
  9. ^ "Concise Japanese Geographic Names Dictionary", December 1989, 12rd edition.③ item in “West Japan”.
  10. ^ Takashi Akiba "Land Japonica, Encyclopedia of Japanese Places" December 1996."West Japan" section.
  11. ^ Misao Tojo "Japanese dialectology" 1954.
  12. ^ Takeshi Shibata "Iwanami Course 11 Japanese Dialects" November 1977, 11.
  13. ^ "Japanese Linguistics, Volume 6, Dialects" November 1977, 11.
  14. ^ JMA region name
  15. ^ Hamashima Shoten editorial department "New Stage Biology Chart New Edition" November 2002.Page 189
  16. ^ Posted the 23 University Entrance Examination Center Examination Notes - Wayback machine(For archived March 2012, 10)


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