title: Hyperinflation

text: In the "monetary model", hyperinflation is a positive feedback cycle of rapid monetary expansion. It has the same cause as all other inflation: money-issuing bodies, central or otherwise, produce currency to pay spiraling costs, often from lax fiscal policy, or the mounting costs of warfare. When business people perceive that the issuer is committed to a policy of rapid currency expansion, they mark up prices to cover the expected decay in the currency's value. The issuer must then accelerate its expansion to cover these prices, which pushes the currency value down even faster than before. According to this model the issuer cannot "win" and the only solution is to abruptly stop expanding the currency. Unfortunately, the end of expansion can cause a severe financial shock to those using the currency as expectations are suddenly adjusted. This policy, combined with reductions of pensions, wages, and government outlays, formed part of the Washington consensus of the 1990s.


title: Hyperinflation

text: Whatever the cause, hyperinflation involves both the supply and velocity of money. Which comes first is a matter of debate, and there may be no universal story that applies to all cases. But once the hyperinflation is established, the pattern of increasing the money stock, by whichever agencies are allowed to do so, is universal. Because this practice increases the supply of currency without any matching increase in demand for it, the price of the currency, that is the exchange rate, naturally falls relative to other currencies. Inflation becomes hyperinflation when the increase in money supply turns specific areas of pricing power into a general frenzy of spending quickly before money becomes worthless. The purchasing power of the currency drops so rapidly that holding cash for even a day is an unacceptable loss of purchasing power. As a result, no one holds currency, which increases the velocity of money, and worsens the crisis.


title: Hyperinflation

text: Because rapidly rising prices undermine the role of money as a store of value, people try to spend it on real goods or services as quickly as possible. Thus, the monetary model predicts that the velocity of money will increase as a result of an excessive increase in the money supply. At the point when money velocity and prices rapidly accelerate in a vicious circle, hyperinflation is out of control, because ordinary policy mechanisms, such as increasing reserve requirements, raising interest rates, or cutting government spending will be ineffective and be responded to by shifting away from the rapidly devalued money and towards other means of exchange.


title: Hyperinflation

text: During a period of hyperinflation, bank runs, loans for 24-hour periods, switching to alternate currencies, the return to use of gold or silver or even barter become common. Many of the people who hoard gold today expect hyperinflation, and are hedging against it by holding specie. There may also be extensive capital flight or flight to a "hard" currency such as the US dollar. This is sometimes met with capital controls, an idea that has swung from standard, to anathema, and back into semi-respectability. All of this constitutes an economy that is operating in an "abnormal" way, which may lead to decreases in real production. If so, that intensifies the hyperinflation, since it means that the amount of goods in "too much money chasing too few goods" formulation is also reduced. This is also part of the vicious circle of hyperinflation.


title: Hyperinflation

text: Once the vicious circle of hyperinflation has been ignited, dramatic policy means are almost always required. Simply raising interest rates is insufficient. Bolivia, for example, underwent a period of hyperinflation in 1985, where prices increased 12,000% in the space of less than a year. The government raised the price of gasoline, which it had been selling at a huge loss to quiet popular discontent, and the hyperinflation came to a halt almost immediately, since it was able to bring in hard currency by selling its oil abroad. The crisis of confidence ended, and people returned deposits to banks. The German hyperinflation (1919 – November 1923) was ended by producing a currency based on assets loaned against by banks, called the Rentenmark. Hyperinflation often ends when a civil conflict ends with one side winning.


title: Hyperinflation

text: Although wage and price controls are sometimes used to control or prevent inflation, no episode of hyperinflation has been ended by the use of price controls alone, because price controls that force merchants to sell at prices far below their restocking costs result in shortages that cause prices to rise still further.


title: Hyperinflation

text: Nobel prize winner Milton Friedman said "We economists don't know much, but we do know how to create a shortage. If you want to create a shortage of tomatoes, for example, just pass a law that retailers can't sell tomatoes for more than two cents per pound. Instantly you'll have a tomato shortage. It's the same with oil or gas."


title: Hyperinflation

text: Hyperinflation increases stock market prices, wipes out the purchasing power of private and public savings, distorts the economy in favor of the hoarding of real assets, causes the monetary base (whether specie or hard currency) to flee the country, and makes the afflicted area anathema to investment.


title: Hyperinflation

text: One of the most important characteristics of hyperinflation is the accelerating substitution of the inflating money by stable money—gold and silver in former times, then relatively stable foreign currencies after the breakdown of the gold or silver standards (Thiers' Law). If inflation is high enough, government regulations like heavy penalties and fines, often combined with exchange controls, cannot prevent this currency substitution. As a consequence, the inflating currency is usually heavily undervalued compared to stable foreign money in terms of purchasing power parity. So foreigners can live cheaply and buy at low prices in the countries hit by high inflation. It follows that governments that do not succeed in engineering a successful currency reform in time must finally legalize the stable foreign currencies (or, formerly, gold and silver) that threaten to fully substitute the inflating money. Otherwise, their tax revenues, including the inflation tax, will approach zero. The last episode of hyperinflation in which this process could be observed was in Zimbabwe in the first decade of the 21st century. In this case, the local money was mainly driven out by the US dollar and the South African rand.


title: Hyperinflation

text: Enactment of price controls to prevent discounting the value of paper money relative to gold, silver, hard currency, or other commodities fail to force acceptance of a paper money that lacks intrinsic value. If the entity responsible for printing a currency promotes excessive money printing, with other factors contributing a reinforcing effect, hyperinflation usually continues. Hyperinflation is generally associated with paper money, which can easily be used to increase the money supply: add more zeros to the plates and print, or even stamp old notes with new numbers. Historically, there have been numerous episodes of hyperinflation in various countries followed by a return to "hard money". Older economies would revert to hard currency and barter when the circulating medium became excessively devalued, generally following a "run" on the store of value.


title: Hyperinflation

text: Much attention on hyperinflation centers on the effect on savers whose investments become worthless. Interest rate changes often cannot keep up with hyperinflation or even high inflation, certainly with contractually fixed interest rates. For example, in the 1970s in the United Kingdom inflation reached 25% per annum, yet interest rates did not rise above 15%—and then only briefly—and many fixed interest rate loans existed. Contractually, there is often no bar to a debtor clearing his long term debt with "hyperinflated cash", nor could a lender simply somehow suspend the loan. Contractual "early redemption penalties" were (and still are) often based on a penalty of "n" months of interest/payment; again no real bar to paying off what had been a large loan. In interwar Germany, for example, much private and corporate debt was effectively wiped out—certainly for those holding fixed interest rate loans.


title: Hyperinflation

text: Ludwig von Mises used the term "crack-up boom" (German: Katastrophenhausse) to describe the economic consequences of an unmitigated increasing in the base-money supply. As more and more money is provided, interest rates decline towards zero. Realizing that fiat money is losing value, investors will try to place money in assets such as real estate, stocks, even art; as these appear to represent "real" value. Asset prices are thus becoming inflated. This potentially spiraling process will ultimately lead to the collapse of the monetary system. The Cantillon effect says that those institutions that receive the new money first are the beneficiaries of the policy.


title: Hyperinflation

text: Hyperinflation is ended by drastic remedies, such as imposing the shock therapy of slashing government expenditures or altering the currency basis. One form this may take is dollarization, the use of a foreign currency (not necessarily the U.S. dollar) as a national unit of currency. An example was dollarization in Ecuador, initiated in September 2000 in response to a 75% loss of value of the Ecuadorian sucre in early 2000. Usually the "dollarization" takes place in spite of all efforts of the government to prevent it by exchange controls, heavy fines and penalties. The government has thus to try to engineer a successful currency reform stabilizing the value of the money. If it does not succeed with this reform the substitution of the inflating by stable money goes on. Thus it is not surprising that there have been at least seven historical cases in which the good (foreign) money did fully drive out the use of the inflating currency. In the end, the government had to legalize the former, for otherwise its revenues would have fallen to zero.


title: Hyperinflation

text: Hyperinflation has always been a traumatic experience for the people who suffer it, and the next political regime almost always enacts policies to try to prevent its recurrence. Often this means making the central bank very aggressive about maintaining price stability, as was the case with the German Bundesbank, or moving to some hard basis of currency, such as a currency board. Many governments have enacted extremely stiff wage and price controls in the wake of hyperinflation, but this does not prevent further inflation of the money supply by the central bank, and always leads to widespread shortages of consumer goods if the controls are rigidly enforced.


title: Hyperinflation

text: In countries experiencing hyperinflation, the central bank often prints money in larger and larger denominations as the smaller denomination notes become worthless. This can result in the production of unusually large denominations of banknotes, including those denominated in amounts of 1,000,000,000 or more.


title: Hyperinflation

text: One way to avoid the use of large numbers is by declaring a new unit of currency. (As an example, instead of 10,000,000,000 dollars, a central bank might set 1 new dollar = 1,000,000,000 old dollars, so the new note would read "10 new dollars".) One example of this is Turkey's revaluation of the Lira on 1 January 2005, when the old Turkish lira (TRL) was converted to the New Turkish lira (TRY) at a rate of 1,000,000 old to 1 new Turkish Lira. While this does not lessen the actual value of a currency, it is called redenomination or revaluation and also occasionally happens in countries with lower inflation rates. During hyperinflation, currency inflation happens so quickly that bills reach large numbers before revaluation.


title: Hyperinflation

text: Some banknotes were stamped to indicate changes of denomination, as it would have taken too long to print new notes. By the time new notes were printed, they would be obsolete (that is, they would be of too low a denomination to be useful).


title: Hyperinflation

text: Metallic coins were rapid casualties of hyperinflation, as the scrap value of metal enormously exceeded its face value. Massive amounts of coinage were melted down, usually illicitly, and exported for hard currency.


title: Hyperinflation

text: Governments will often try to disguise the true rate of inflation through a variety of techniques. None of these actions addresses the root causes of inflation; and if discovered, they tend to further undermine trust in the currency, causing further increases in inflation. Price controls will generally result in shortages and hoarding and extremely high demand for the controlled goods, causing disruptions of supply chains. Products available to consumers may diminish or disappear as businesses no longer find it economic to continue producing and/or distributing such goods at the legal prices, further exacerbating the shortages.


title: Hyperinflation

text: There are also issues with computerized money-handling systems. In Zimbabwe, during the hyperinflation of the Zimbabwe dollar, many automated teller machines and payment card machines struggled with arithmetic overflow errors as customers required many billions and trillions of dollars at one time.


title: Hyperinflation

text: In 1922, inflation in Austria reached 1,426%, and from 1914 to January 1923, the consumer price index rose by a factor of 11,836, with the highest banknote in denominations of 500,000 Kronen. After World War I, essentially all State enterprises ran at a loss, and the number of state employees in the capital, Vienna, was greater than in the earlier monarchy, even though the new republic was nearly one-eighth of the size.


title: Hyperinflation

text: Observing the Austrian response to developing hyperinflation, which included the hoarding of food and the speculation in foreign currencies, Owen S. Phillpotts, the Commercial Secretary at the British Legation in Vienna wrote: "The Austrians are like men on a ship who cannot manage it, and are continually signalling for help. While waiting, however, most of them begin to cut rafts, each for himself, out of the sides and decks. The ship has not yet sunk despite the leaks so caused, and those who have acquired stores of wood in this way may use them to cook their food, while the more seamanlike look on cold and hungry. The population lack courage and energy as well as patriotism."


title: Hyperinflation

text: Increasing hyperinflation in Bolivia has plagued, and at times crippled, its economy and currency since the 1970s. At one time in 1985, the country experienced an annual inflation rate of more than 20,000%. Fiscal and monetary reform reduced the inflation rate to single digits by the 1990s, and in 2004 Bolivia experienced a manageable 4.9% rate of inflation.


title: Hyperinflation

text: In 1987, the Bolivian peso was replaced by the new boliviano at a rate of one million to one (when 1 US dollar was worth 1.8–1.9 million pesos). At that time, 1 new boliviano was roughly equivalent to 1 U.S. dollar.


title: Hyperinflation

text: Brazilian hyperinflation lasted from 1985 (the year when the military dictatorship ended) to 1994, with prices rising by 184,901,570,954.39% (or percent; equivalent to a tenfold increase on average a year) in that time due to the uncontrolled printing of money. There were many economic plans that tried to contain hyperinflation including zeroes cuts, price freezes and even confiscation of bank accounts.


title: Hyperinflation

text: The highest value was in March 1990, when the government inflation index reached 82.39%. Hyperinflation ended in July 1994 with the Real Plan during the government of Itamar Franco. During the period of inflation Brazil adopted a total of six different currencies, as the government constantly changed due to rapid devaluation and increase in the number of zeros.


title: Hyperinflation

text: From 1948 to 1949, near the end of the Chinese Civil War, the Republic of China went through a period of hyperinflation. In 1947, the highest denomination bill was 50,000 yuan. By mid-1948, the highest denomination was 180,000,000 yuan. The 1948 currency reform replaced the yuan by the gold yuan at an exchange rate of 1 gold yuan = 3,000,000 yuan. In less than a year, the highest denomination was 10,000,000 gold yuan. In the final days of the civil war, the silver yuan was briefly introduced at the rate of 500,000,000 gold yuan. Meanwhile, the highest denomination issued by a regional bank was 6,000,000,000 yuan (issued by Xinjiang Provincial Bank in 1949). After renminbi was instituted by the new communist government, hyperinflation ceased, with a revaluation of 1:10,000 old yuan in 1955.


title: Hyperinflation

text: During the French Revolution and first Republic, the National Assembly issued bonds, some backed by seized church property, called assignats. Napoleon replaced them with the franc in 1803, at which time the assignats were basically worthless. Stephen D. Dillaye pointed out that one of the reasons for the failure was massive counterfeiting of the paper currency, largely through London. According to Dillaye: "Seventeen manufacturing establishments were in full operation in London, with a force of four hundred men devoted to the production of false and forged Assignats."


title: Hyperinflation

text: By November 1922, the value in gold of money in circulation had fallen from £300 million stg before World War I to £20 million. The Reichsbank responded by the unlimited printing of notes, thereby accelerating the devaluation of the mark. In his report to London, Lord D'Abernon wrote: "In the whole course of history, no dog has ever run after its own tail with the speed of the Reichsbank." Germany went through its worst inflation in 1923. In 1922, the highest denomination was 50,000ℳ. By 1923, the highest denomination was 100,000,000,000,000ℳ (10 marks). In December 1923 the exchange rate was 4,200,000,000,000ℳ (4.2 × 10 marks) to 1 US dollar. In 1923, the rate of inflation hit 3.25 × 10 percent per month (prices double every two days). Beginning on 20 November 1923, 1,000,000,000,000ℳ were exchanged for 1 Rentenmark, so that RM 4.2 was worth 1 US dollar, exactly the same rate the mark had in 1914.


title: Hyperinflation

text: With the German invasion in April 1941, there was an abrupt increase in prices. This was due to psychological factors related to the fear of shortages and to the hoarding of goods. During the German and Italian Axis occupation of Greece (1941–1944), the agricultural, mineral, industrial etc. production of Greece were used to sustain the occupation forces, but also to secure provisions for the Afrika Korps. One part of these "sales" of provisions was settled with bilateral clearing through the German DEGRIGES and the Italian Sagic companies at very low prices. As the value of Greek exports in drachmas fell, the demand for drachmas followed suit and so did its forex rate. While shortages started due to naval blockades and hoarding, the prices of commodities soared. The other part of the "purchases" was settled with drachmas secured from the Bank of Greece and printed for this purpose by private printing presses. As prices soared, the Germans and Italians started requesting more and more drachmas from the Bank of Greece to offset price increases; each time prices increased, the note circulation followed suit soon afterwards. For the year starting November 1943, the inflation rate was 2.5 × 10%, the circulation was 6.28 × 10 drachmae and one gold sovereign cost 43,167 billion drachmas. The hyperinflation started subsiding immediately after the departure of the German occupation forces, but inflation rates took several years to fall below 50%.


title: Hyperinflation

text: The Treaty of Trianon and political instability between 1919 and 1924 led to a major inflation of Hungary's currency. In 1921, in an attempt to stop this inflation, the national assembly of Hungary passed the Hegedüs reforms, including a 20% levy on bank deposits, but this precipitated a mistrust of banks by the public, especially the peasants, and resulted in a reduction in savings, and thus an increase in the amount of currency in circulation. Due to the reduced tax base, the government resorted to printing money, and in 1923 inflation in Hungary reached 98% per month.


title: Hyperinflation

text: Between the end of 1945 and July 1946, Hungary went through the highest inflation ever recorded. In 1944, the highest banknote value was 1,000 P. By the end of 1945, it was 10,000,000 P, and the highest value in mid-1946 was 100,000,000,000,000,000,000 P (10 pengő). A special currency, the adópengő (or "tax pengő") was created for tax and postal payments. The inflation was such that the value of the adópengő was adjusted each day by radio announcement. On 1 January 1946, one adópengő equaled one pengő, but by late July, one adópengő equaled 2,000,000,000,000,000,000,000 P or 2×10 P (2 sextillion pengő).


title: Hyperinflation

text: When the pengő was replaced in August 1946 by the forint, the total value of all Hungarian banknotes in circulation amounted to of one US cent. Inflation had peaked at 1.3 × 10% per month (i.e. prices doubled every 15.6 hours). On 18 August 1946, 400,000,000,000,000,000,000,000,000,000 P (4 pengő, four hundred quadrilliard on the long scale used in Hungary, or four hundred octillion on short scale) became 1 Ft.


title: Hyperinflation

text: Malaya and Singapore were under Japanese occupation from 1942 until 1945. The Japanese issued "banana notes" as the official currency to replace the Straits currency issued by the British. During that time, the cost of basic necessities increased drastically. As the occupation proceeded, the Japanese authorities printed more money to fund their wartime activities, which resulted in hyperinflation and a severe depreciation in value of the banana note.


title: Hyperinflation

text: From February to December 1942, $100 of Straits currency was worth $100 in Japanese scrip, after which the value of Japanese scrip began to erode, reaching $385 on December 1943 and $1,850 one year later. By 1 August 1945, this had inflated to $10,500, and 11 days later it had reached $95,000. After 13 August 1945, Japanese scrip had become valueless.


title: Hyperinflation

text: North Korea has most likely experienced hyperinflation from December 2009 to mid-January 2011. Based on the price of rice, North Korea's hyperinflation peaked in mid-January 2010, but according to black market exchange-rate data, and calculations based on purchasing power parity, North Korea experienced its peak month of inflation in early March 2010. These data points are unofficial, however, and therefore must be treated with a degree of caution.


title: Hyperinflation

text: In modern history, Peru underwent a period of hyperinflation in the 1980s to the early 1990s starting with President Fernando Belaúnde's second administration, heightened during Alan García's first administration, to the beginning of Alberto Fujimori's term. 1 US dollar was worth over S/3,210,000,000. Garcia's term introduced the inti, which worsened inflation into hyperinflation. Peru's currency and economy were stabilized under Fujimori's Nuevo Sol program, which has remained Peru's currency since 1991.


title: Hyperinflation

text: Poland has gone through two episodes of hyperinflation since the country regained independence following the end of World War I, the first in 1923, the second in 1989–1990. Both events resulted in the introduction of new currencies. In 1924, the "złoty" replaced the original currency of post-war Poland, the mark. This currency was subsequently replaced by another of the same name in 1950. As a result of the second hyperinflation crisis, the current "new złoty" was introduced in 1995 (ISO code: PLN). See the article on Polish złoty for more information about the currency's history.


title: Hyperinflation

text: The newly independent Poland had been struggling with a large budget deficit since its inception in 1918 but it was in 1923 when inflation reached its peak. The exchange rate of the Polish mark (Mp) to the US dollar dropped from Mp 9.- per dollar in 1918 to Mp 6,375,000.- per dollar at the end of 1923. A new personal 'inflation tax' was introduced. The resolution of the crisis is attributed to Władysław Grabski, who became prime minister of Poland in December 1923. Having nominated an all-new government and being granted extraordinary lawmaking powers by the Sejm for a period of six months, he introduced a new currency, the "złoty" ("florin" in Polish), established a new national bank and scrapped the inflation tax, which took place throughout 1924.


title: Hyperinflation

text: The economic crisis in Poland in the 1980s was accompanied by rising inflation when new money was printed to cover a budget deficit. Although inflation was not as acute as in 1920s, it is estimated that its annual rate reached around 600% in a period of over a year spanning parts of 1989 and 1990. The economy was stabilised by the adoption of the Balcerowicz Plan in 1989, named after the main author of the reforms, minister of finance Leszek Balcerowicz. The plan was largely inspired by the previous Grabski's reforms.


title: Hyperinflation

text: The Japanese government occupying the Philippines during World War II issued fiat currencies for general circulation. The Japanese-sponsored Second Philippine Republic government led by Jose P. Laurel at the same time outlawed possession of other currencies, most especially "guerrilla money". The fiat money's lack of value earned it the derisive nickname "Mickey Mouse money". Survivors of the war often tell tales of bringing suitcases or "bayong" (native bags made of woven coconut or buri leaf strips) overflowing with Japanese-issued notes. Early on, 75 JIM pesos could buy one duck egg. In 1944, a box of matches cost more than 100 JIM pesos.


title: Hyperinflation

text: In 1942, the highest denomination available was ₱10. Before the end of the war, because of inflation, the Japanese government was forced to issue ₱100, ₱500, and ₱1,000 notes.


title: Hyperinflation

text: A seven-year period of uncontrollable spiralling inflation occurred in the early Soviet Union, running from the earliest days of the Bolshevik Revolution in November 1917 to the reestablishment of the gold standard with the introduction of the chervonets as part of the New Economic Policy. The inflationary crisis effectively ended in March 1924 with the introduction of the so-called "gold ruble" as the country's standard currency.


title: Hyperinflation

text: The early Soviet hyperinflationary period was marked by three successive redenominations of its currency, in which "new rubles" replaced old at the rates of 10,000:1 (1 January 1922), 100:1 (1 January 1923), and 50,000:1 (7 March 1924), respectively.


title: Hyperinflation

text: Since the end of 2017 Turkey has high inflation rates. It is speculated that the new elections took place frustrated because of the impending crisis to forestall. In October 2017, inflation was at 11.9%, the highest rate since July 2008. The lira fell from TL 1.503 = US$1 in 2010 to TL 18.0664 = US$1 in August 2022.


title: Hyperinflation

text: Venezuela's hyperinflation began in November 2016. Inflation of Venezuela's bolivar fuerte (VEF) in 2014 reached 69% and was the highest in the world. In 2015, inflation was 181%, the highest in the world and the highest in the country's history at that time, 800% in 2016, over 4,000% in 2017, and 1,698,488% in 2018, with Venezuela spiraling into hyperinflation. While the Venezuelan government "has essentially stopped" producing official inflation estimates as of early 2018, one estimate of the rate at that time was 5,220%, according to inflation economist Steve Hanke of Johns Hopkins University.


title: Hyperinflation

text: Inflation has affected Venezuelans so much that in 2017, some people became video game gold farmers and could be seen playing games such as "RuneScape" to sell in-game currency or characters for real currency. In many cases, these gamers made more money than salaried workers in Venezuela even though they were earning just a few dollars per day. During the Christmas season of 2017, some shops would no longer use price tags since prices would inflate so quickly, so customers were required to ask staff at stores how much each item was.


title: Hyperinflation

text: The International Monetary Fund estimated in 2018 that Venezuela's inflation rate would reach 1,000,000% by the end of the year. This forecast was criticized by Steve H. Hanke, professor of applied economics at The Johns Hopkins University and senior fellow at the Cato Institute. According to Hanke, the IMF had released a "bogus forecast" because "no one has ever been able to accurately forecast the course or the duration of an episode of hyperinflation. But that has not stopped the IMF from offering inflation forecasts for Venezuela that have proven to be wildly inaccurate".


title: Hyperinflation

text: In July 2018, hyperinflation in Venezuela was sitting at 33,151%, "the 23rd most severe episode of hyperinflation in history".


title: Hyperinflation

text: In April 2019, the International Monetary Fund estimated that inflation would reach 10,000,000% by the end of 2019.


title: Hyperinflation

text: In May 2019, the Central Bank of Venezuela released economic data for the first time since 2015. According to this release, the inflation of Venezuela was 274% in 2016, 863% in 2017 and 130,060% in 2018. The annualised inflation rate as of April 2019 was estimated to be 282,972.8% as of April 2019, and cumulative inflation from 2016 to April 2019 was estimated at 53,798,500%.


title: Hyperinflation

text: The new reports imply a contraction of more than half of the economy in five years, according to the "Financial Times" "one of the biggest contractions in Latin American history". According to undisclosed sources from Reuters, the release of these numbers was due to pressure from China, a Maduro ally. One of these sources claims that the disclosure of economic numbers may bring Venezuela into compliance with the IMF, making it harder to support Juan Guaidó during the presidential crisis. At the time, the IMF was not able to support the validity of the data as they had not been able to contact the authorities.


title: Hyperinflation

text: Vietnam went through a period of chaos and high inflation in the late 1980s, with inflation peaking at 774% in 1988, after the country's "price-wage-currency" reform package, led by then-Deputy Prime Minister , had failed. High inflation also occurred in the early stages of the socialist-oriented market economic reforms commonly referred to as the Đổi Mới.


title: Hyperinflation

text: Hyperinflation in the Socialist Federal Republic of Yugoslavia happened before and during the period of breakup of Yugoslavia, from 1989 to 1991. In April 1992, one of its successor states, FR Yugoslavia, entered a period of hyperinflation in the Federal Republic of Yugoslavia, that lasted until 1994. One of several regional conflicts accompanying the dissolution of Yugoslavia was the Bosnian War (1992–1995). The Belgrade government of Slobodan Milošević backed ethnic Serbian forces in the conflict, resulting in a United Nations boycott of Yugoslavia. The UN boycott collapsed an economy already weakened by regional war, with the projected monthly inflation rate accelerating to one million percent by December 1993 (prices double every 2.3 days).


title: Hyperinflation

text: The highest denomination in 1988 was 50,000 . By 1989, it was 2,000,000 . In the 1990 currency reform, 1 new dinar was exchanged for 10,000 old dinars. After socialist Yugoslavia broke up, the 1992 currency reform in FR Yugoslavia led to 1 new dinar being exchanged for 10 old dinars. The highest denomination in 1992 was 50,000 . By 1993, it was 10,000,000,000 . In the 1993 currency reform, 1 new dinar was exchanged for 1,000,000 old dinars. Before the year was over, however, the highest denomination was 500,000,000,000 dinars. In the 1994 currency reform, 1 new dinar was exchanged for 1,000,000,000 old dinars. In another currency reform a month later, 1 novi dinar was exchanged for 13 million dinars (1 novi dinar = 1 Deutschmark at the time of exchange). The overall impact of hyperinflation was that 1 novi dinar was equal to 1 × 10 – 1.3 × 10 pre-1990 dinars. Yugoslavia's rate of inflation hit 5 × 10% cumulative inflation over the time period 1 October 1993 and 24 January 1994.


title: Hyperinflation

text: Hyperinflation in Zimbabwe was one of the few instances that resulted in the abandonment of the local currency. At independence in 1980, the Zimbabwe dollar (ZWD) was worth about US$1.25. Afterwards, however, rampant inflation and the collapse of the economy severely devalued the currency. Inflation was relatively steady until the early 1990s when economic disruption caused by failed land reform agreements and rampant government corruption resulted in reductions in food production and the decline of foreign investment. Several multinational companies began hoarding retail goods in warehouses in Zimbabwe and just south of the border, preventing commodities from becoming available on the market. The result was that to pay its expenditures Mugabe's government and Gideon Gono's Reserve Bank printed more and more notes with higher face values.


title: Hyperinflation

text: Hyperinflation began early in the 21st century, reaching 624% in 2004. It fell back to low triple digits before surging to a new high of 1,730% in 2006. The Reserve Bank of Zimbabwe revalued on 1 August 2006 at a ratio of 1,000 ZWD to each second dollar (ZWN), but year-to-year inflation rose by June 2007 to 11,000% (versus an earlier estimate of 9,000%). Larger denominations were progressively issued in 2008:


title: Hyperinflation

text: Inflation by 16 July officially surged to 2,200,000% with some analysts estimating figures surpassing 9,000,000%. As of 22 July 2008 the value of the Zimbabwe dollar fell to approximately Z$688 billion per US$1, or Z$688 trillion in pre-August 2006 Zimbabwean dollars.


title: Hyperinflation

text: On 1 August 2008, the Zimbabwe dollar was redenominated at the ratio of ZWN to each third dollar (ZWR). On 19 August 2008, official figures announced for June estimated the inflation over 11,250,000%. Zimbabwe's annual inflation was 231,000,000% in July (prices doubling every 17.3 days). By October 2008 Zimbabwe was mired in hyperinflation with wages falling far behind inflation. In this dysfunctional economy hospitals and schools had chronic staffing problems, because many nurses and teachers could not afford bus fare to work. Most of the capital of Harare was without water because the authorities had stopped paying the bills to buy and transport the treatment chemicals. Desperate for foreign currency to keep the government functioning, Zimbabwe's central bank governor, Gideon Gono, sent runners into the streets with suitcases of Zimbabwean dollars to buy up American dollars and South African rand.


title: Hyperinflation

text: For periods after July 2008, no official inflation statistics were released. Prof. Steve H. Hanke overcame the problem by estimating inflation rates after July 2008 and publishing the Hanke Hyperinflation Index for Zimbabwe. Prof. Hanke's HHIZ measure indicated that the inflation peaked at an annual rate of 89.7 sextillion percent (89,700,000,000,000,000,000,000%, or %) in mid-November 2008. The peak monthly rate was 79.6 billion percent, which is equivalent to a 98% daily rate, or around % yearly rate. At that rate, prices were doubling every 24.7 hours. Note that many of these figures should be considered mostly theoretical since hyperinflation did not proceed at this rate over a whole year.


title: Hyperinflation

text: At its November 2008 peak, Zimbabwe's rate of inflation approached, but failed to surpass, Hungary's July 1946 world record. On 2 February 2009, the dollar was redenominated for the third time at the ratio of ZWR to 1 ZWL, only three weeks after the Z$100 trillion banknote was issued on 16 January, but hyperinflation waned by then as official inflation rates in USD were announced and foreign transactions were legalised, and on 12 April the Zimbabwe dollar was abandoned in favour of using only foreign currencies. The overall impact of hyperinflation was US$1 = Z$.


title: Hyperinflation

text: Ironically, following the abandonment of the ZWR and subsequent use of reserve currencies, banknotes from the hyperinflation period of the old Zimbabwe dollar began attracting international attention as collectors items, having accrued numismatic value, selling for prices many orders of magnitude higher than their old purchasing power.


title: Hyperinflation

text: Countries have experienced periods of very high inflation, that did not reach hyperinflation, as defined as a "monthly" inflation rate exceeding 50% per month.


title: Hyperinflation

text: As the first user of fiat currency, China was also the first country to experience high inflation. Paper currency was introduced during the Tang Dynasty, and was generally welcomed. It maintained its value, as successive Chinese governments put in place strict controls on issuance. The convenience of paper currency for trade purposes led to strong demand for paper currency. It was only when discipline on quantity supplied broke down that inflation emerged. The Yuan Dynasty (1271–1368) was the first to print large amounts of fiat paper money to fund its wars, resulting in very high inflation.


title: Hyperinflation

text: During the Crisis of the Third Century, Rome underwent high inflation caused by years of coinage devaluation.


title: Hyperinflation

text: Argentina has an economic history of very high inflation since World War II, mostly caused by excessive money supply increases. The Latin American debt crisis was caused by foreign debt held in other currencies, and exploded because the floating exchange rates depreciated the Argentinian currencies because of inflation, capital flight, and not enough foreign reserve currencies ratio.


title: Hyperinflation

text: Between 1620 and 1622 the Kreuzer fell from 1 Reichsthaler to 124 Kreuzer in end of 1619 to 1 Reichstaler to over 600 (regionally over 1000) Kreuzer in end of 1622, during the Thirty Years' War. This is a monthly inflation rate of over 20.6% (regionally over 34.4%).


title: Hyperinflation

text: After the Military dictatorship in Brazil ended in 1985 and its transition to democracy. Tancredo Neves dies shortly after winning the 1985 Brazilian presidential election and his Vice President José Sarney becomes president. In 1986 inflation was already at 400% annually and Sarney tried to remedy inflation with a wage freeze, price controls, and reforming the currency by dropping three zeros from it, all while tripling the money supply to fund government expenditures and public sector that was consuming 50% of GDP at the time. Bank loans had an interest rate of around 25% a month to maintain a positive real yield during inflation. In February 1987 the government defaulted on $110 billion in foreign loans, that was part of the Latin American debt crisis.


title: Hyperinflation

text: Between 1987 and 1995 the Iraqi Dinar went from an official value of 0.306 Dinars/USD (or US$3.26 per dinar, though the black market rate is thought to have been substantially lower) to 3,000 dinars/USD due to government printing of tens of trillions of dinars starting with a base of only tens of billions. That equates to approximately 315% inflation per year averaged over that eight-year period.


title: Hyperinflation

text: In spite of increased oil prices in the late 1970s (Mexico is a producer and exporter), Mexico defaulted on its external debt in 1982. As a result, the country suffered a severe case of capital flight and several years of acute inflation and peso devaluation, leading to an accumulated inflation rate of almost 27,000% between December 1975 and late 1988. On 1 January 1993, Mexico created a new currency, the "nuevo peso" ("new peso", or MXN), which chopped three zeros off the old peso (One new peso was equal to 1,000 old MXP pesos).


title: Hyperinflation

text: After the Nicaraguan Revolution in 1979 where the communist Sandinista National Liberation Front ousted the Somoza dictatorship, the economy contracted by 34 percent during that time. The Sandinistas nationalized many industries and had expansive monetary policy that started to contribute to rising inflation. Fighting with the Contras and the United States embargo against Nicaragua in May 1985 also contributed to the problem. Inflation hit 10,000% in 1988.


title: Hyperinflation

text: Between 1998 and 1999, Ecuador faced a period of economic instability that resulted from a combined banking crisis, currency crisis, and sovereign debt crisis. Severe inflation and devaluation of the Ecuadorean Sucre lead to President Jamil Mahuad announcing on 9 January 2000 that the US dollar would be adopted as the national currency.


title: Hyperinflation

text: Despite the government's efforts to curb inflation, the Sucre depreciated rapidly at the end of 1999, resulting in widespread informal use of U.S. dollars in the financial system. As a last resort to prevent hyperinflation, the government formally adopted the U.S. dollar in January 2000. The stability of the new currency was a necessary first step towards economic recovery, but the exchange rate was fixed at 25,000:1, which resulted in great losses of wealth.


title: Hyperinflation

text: In Roman Egypt, where the best documentation on pricing has survived, the price of a measure of wheat was 200 drachmae in 276 AD, and increased to more than 2,000,000 drachmae in 334 AD, roughly 1,000,000% inflation in a span of 58 years.


title: Hyperinflation

text: Although the price increased by a factor of 10,000 over 58 years, the annual rate of inflation was only 17.2% (1.4% monthly) compounded.


title: Hyperinflation

text: Romania experienced high inflation in the 1990s. The highest denomination in 1990 was 100 lei and in 1998 was 100,000 lei. By 2000 it was 500,000 lei. In early 2005 it was 1,000,000 lei. In July 2005 the lei was replaced by the new leu at 10,000 old lei = 1 new leu. Inflation in 2005 was 9%. In July 2005 the highest denomination became 500 lei (= 5,000,000 old lei).


title: Hyperinflation

text: In the transition from the Soviet Union planned economy and price controls to a free market economy there were substantial imbalances in supply and demand. The Government increased the money supply by eighteen times by the end of 1992. A lot of corruption from Government enterprises taking up debt and getting bailed out from the government. The Federal budget deficit was 20 percent of GDP in 1992, mostly financed by increasing money supply. This resulted in an inflation rate of over 2,000% in 1992.


title: Hyperinflation

text: The Second Transnistrian ruble consisted solely of banknotes and suffered from high inflation, necessitating the issue of notes overstamped with higher denominations. 1 and sometimes 10 rubles become 10,000 rubles, 5 rubles become 50,000 and 10 rubles become 100,000 rubles. In 2000, a new ruble was introduced at a rate of 1 new ruble = 1,000,000 old rubles.


title: Hyperinflation

text: During the Revolutionary War, when the Continental Congress authorized the printing of paper called continental currency, the monthly inflation rate reached a peak of 47% in November 1779 (Bernholz 2003: 48). These notes depreciated rapidly, giving rise to the expression "not worth a continental". One cause of the inflation was counterfeiting by the British, who ran a press on HMS "Phoenix", moored in New York Harbor. The counterfeits were advertised and sold almost for the price of the paper they were printed on.


title: Hyperinflation

text: During the U.S. Civil War between January 1861 and April 1865, the Confederate States decided to finance the war by printing money. The Lerner Commodity Price Index of leading cities in the eastern Confederacy states subsequently increased from 100 to 9,200 in that time. In the final months of the Civil War, the Confederate dollar was almost worthless. Similarly, the Union government inflated its greenbacks, with the monthly rate peaking at 40% in March 1864 (Bernholz 2003: 107).


title: Hyperinflation

text: Inflation rate is usually measured in percent per year. It can also be measured in percent per month or in price doubling time.


title: Hyperinflation

text: Often, at redenominations, three zeroes are cut from the bills. It can be read from the table that if the (annual) inflation is for example 100%, it takes 3.32 years to produce one more zero on the price tags, or 3 × 3.32 = 9.96 years to produce three zeroes. Thus can one expect a redenomination to take place about 9.96 years after the currency was introduced.


title: Aja (album)

text: Aja (, pronounced like "Asia") is the sixth studio album by the American jazz rock band Steely Dan. It was released on September 23, 1977, by ABC Records. Recording alongside nearly 40 musicians, band leaders Donald Fagen and Walter Becker pushed Steely Dan further into experimenting with different combinations of session players while pursuing longer, more sophisticated compositions for the album.


title: Aja (album)

text: The album peaked at number three on the US charts and number five in the UK, ultimately becoming Steely Dan's most commercially successful LP. It spawned a number of hit singles, including "Peg", "Deacon Blues", and "Josie".


title: Aja (album)

text: In July 1978, "Aja" won the Grammy Award for Best Engineered Recording – Non-Classical and received Grammy nominations for Album of the Year and Best Pop Performance by a Duo or Group with Vocals. It has since appeared frequently on professional rankings of the greatest albums, with critics and audiophiles applauding the album's high production standards. In 2010, the Library of Congress selected the album for preservation in the National Recording Registry for being "culturally, historically, or artistically significant."


title: Aja (album)

text: The album was produced by Steely Dan's longtime producer Gary Katz and features several leading session musicians. The eight-minute-long title track features a jazz-based chord progression and a solo by saxophonist Wayne Shorter. Becker did not perform on "Black Cow" and "Peg".


title: Aja (album)

text: The album's title is pronounced like "Asia". Donald Fagen has said the album was named for a Korean woman who married the brother of one of his high-school friends. The cover photo by Hideki Fujii features Japanese model and actress Sayoko Yamaguchi and was designed by Patricia Mitsui and Geoff Westen. The inside photos were taken by Walter Becker and Dorothy A. White.


title: Aja (album)

text: "Aja" was released on , by ABC Records. In anticipation of the release, Katz urged the relatively private Fagen and Becker to raise their public profile, including a meeting with Irving Azoff for his services as their manager. Fagen expressed initial reservations at the time: "We were ready to go blissfully through life without a manager."


title: Aja (album)

text: With Azoff's connections with record stores and the album being offered at a discounted price, "Aja" became "one of the season's hottest albums and by far Steely Dan's fastest-selling ever", according to Cameron Crowe in the December 1977 issue of "Rolling Stone". Within three weeks of release, the album reached the top five of the "Billboard" 200, ultimately peaking at number three to become the band's highest-peaking album on the chart. It also reached number five on the UK albums chart. According to "Billboard", it became the band's biggest hit and one of the first albums to be certified platinum.


title: Aja (album)

text: When DTS attempted to make a 5.1 version, it was discovered that the multitrack masters for both "Black Cow" and the title track were missing. For this same reason, a multichannel SACD version was cancelled by Universal Music. Donald Fagen has offered a reward for the missing masters or any information that leads to their recovery.


title: Aja (album)

text: Reviewing in 1977 for "Rolling Stone", Michael Duffy said that "the conceptual framework of [Steely Dan's] music has shifted from the pretext of rock & roll toward a smoother, awesomely clean and calculated mutation of various rock, pop and jazz idioms", while their lyrics "remain as pleasantly obtuse and cynical as ever". Duffy added that while the duo's "extreme intellectual self-consciousness" was beginning to show its limitations, the latter "may be precisely the quality that makes Walter Becker and Donald Fagen the perfect musical antiheroes for the Seventies." Robert Christgau of "The Village Voice" initially "hated" the record before he "realized that, unlike "The Royal Scam", it was stretching me some", while noting that he was "grateful to find Fagen and Becker's collegiate cynicism in decline". However, he believed the band's preference for longer, more sophisticated songs "could turn into their fatal flaw". Greg Kot was also lukewarm toward the band's stylistic departure, later writing in the "Chicago Tribune": "The clinical coldness first evidenced on "The Royal Scam" is perfected here. Longer, more languid songs replace the acerbic pithiness of old." Barry Walters was more receptive in a retrospective review for "Rolling Stone", saying "rock has always excelled at embodying adolescent ache. But it's rare when rock captures the complications of adult sorrows almost purely with its sound."


title: Aja (album)

text: Jazz historian Ted Gioia cites "Aja" as an example of Steely Dan "proving that pop-rock could equally benefit from a healthy dose of jazz" during their original tenure, which coincided with a period when rock musicians frequently experimented with jazz idioms and techniques. In the opinion of "Pitchfork"s Amanda Petrusich, it is "as much a jazz record as a pop one", while Ben Ratliff from "The New York Times" says it "created a new standard for the relationship between jazz and rock, one that was basically irreproducible, by Steely Dan or anyone else ... a progressive jazz record with backbeats, a '70s hipster's extension of what had been Gil Evans's vision two decades earlier." In Dylan Jones' list of the best jazz albums for "GQ", "Aja" ranked 62nd.


title: Aja (album)

text: The album has been cited by music journalists as one of the best test recordings for audiophiles, due to its high production standards. Walters noted in his review "the album's surreal sonic perfection, its melodic and harmonic complexity - music so technically demanding its creators had to call in A-list session players to realize the sounds they heard in their heads but could not play, even on the instruments they had mastered." Reviewing "Aja"s 2007 all-analog LP reissue, Ken Kessler from "Hi-Fi News & Record Review" gave top marks to both recording and performance qualities, calling the album "sublime jazz-rock that hasn't aged at all - unless you consider 'intelligence' passe - it is everything you expected the painfully hip/cool Becker and Fagen to deliver."


title: Aja (album)

text: "Aja" has frequently appeared on rankings of the greatest albums of all time. In 1991, France's "Rock & Folk" included "Aja" on a list of the 250 best albums released during the magazine's existence, beginning in 1966. In 1999, it was ranked 59th on the national Israeli newspaper "Yedioth Ahronoth"s "Top 99 Albums of All Time". In 2000 it was voted number 118 in Colin Larkin's "All Time Top 1000 Albums". In 2003, the album was inducted into the Grammy Hall of Fame and ranked number 145 on "Rolling Stone"s "The 500 Greatest Albums of All Time" list, maintaining the rating in a 2012 revised list, before rising to number 63 in a 2020 reboot of the list. In 2006, "Aja" was included in the book "1001 Albums You Must Hear Before You Die". In 2010, the Library of Congress selected "Aja" for inclusion in the United States National Recording Registry based on its cultural, artistic or historical significance alongside De La Soul's 1989 debut album "3 Feet High and Rising" which sampled the album as well. Based on such rankings, the aggregate website Acclaimed Music lists "Aja" as 95th most acclaimed album of the 1970s and the 318th most acclaimed album in history.


title: Aja (album)

text: The singer Bilal names it among his 25 favorite albums, explaining that, "It's a great body of work. It seems very thought out from beginning to end, every song just had a certain vibe. The songwriting to the sound and the look of the album, the whole package was just very well thought out."


title: Aja (album)

text: In 1999, "Aja" was covered for an episode of the British documentary series "Classic Albums", featuring a song-by-song study of the album (the only omission being "I Got the News", which is played during the closing credits), interviews with Steely Dan co-founders Walter Becker and Donald Fagen (among others) plus new, live-in-studio versions of songs from the album. Becker and Fagen also play back several of the rejected guitar solos for "Peg", which were recorded before Jay Graydon produced the satisfactory take. Andy Gill, one of the other interviewees, said: "Jazz-rock was a fundamental part of the 70s musical landscape … [Steely Dan] wasn't rock or pop music with ideas above its station, and it wasn't jazzers slumming … it was a very well-forged alloy of the two – you couldn't separate the pop music from the jazz in their music." Discussing the album's sound, British musician Ian Dury said in the episode that he heard elements of legendary jazz musicians like Charlie Parker, Charles Mingus, and Art Blakey. "Well, "Aja"<nowiki>'</nowiki>s got a sound that lifts your heart up, and it's the most consistent up-full, heart-warming … even though, it is a classic LA kinda sound", Dury explained. "You wouldn't think it was recorded anywhere else in the world. It's got California through its blood, even though they are boys from New York … They've got a skill that can make images that aren't puerile and don't make you think you've heard it before … very 'Hollywood filmic' in a way, the imagery is very imaginable, in a visual sense."


title: Aja (album)

text: In retrospective appraisals, "Aja" has been discussed by music journalists as an important release in the development of yacht rock. For "Spin" in 2009, Chuck Eddy lists it among the genre's eight essential albums. Writing for "uDiscoverMusic" in 2019, Paul Sexton said that with the album, Steely Dan "announced their ever-greater exploration of jazz influences" that would lead to "their yacht-rock masterpiece" in 1980's "Gaucho". Patrick Hosken from MTV News said that both "Aja" and "Gaucho" show how "great yacht rock is also more musically ambitious than it might seem, tying blue-eyed soul and jazz to funk and R&B". "Aja" was included in "Vinyl Me, Please" magazine's list of the 10 best yacht rock albums, with an accompanying essay that said: "Steely Dan’s importance to yacht rock can’t be overstated. … Arguably the Dan is smoothest on the 1980 smash "Gaucho", but "Aja" finds Walter Becker and Donald Fagen comfortably hitting a middle-ground stride … as a mainstream hit factory while remaining expansive and adventurous". John Lawler from "Something Else!" said, "The song and performance that best exemplifies the half-time, funky, laid (way) back in the beat shuffle within the jazz-pop environment of the mid- to late- 70s can be found on 'Home at Last.' Bernard “Pretty” Purdie feeds off Chuck Rainey’s bass with righteous grooves and masterful off-beat fills with alacrity in this tight band favorite."


title: Aja (album)

text: The sessions for "Aja" produced several outtakes, including "The Bear" and “Stand by the Seawall”, the latter including an alternate version that is a complete different song, sharing only the name. The songs were never officially released, but “The Bear” would later be played live on their 2011 "Shuffle Diplomacy" tour.


title: Cloud

text: In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may compose the droplets and crystals. On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture (usually in the form of water vapor) from an adjacent source to raise the dew point to the ambient temperature.


title: Cloud

text: They are seen in the Earth's homosphere, which includes the troposphere, stratosphere, and mesosphere. Nephology is the science of clouds, which is undertaken in the cloud physics branch of meteorology. There are two methods of naming clouds in their respective layers of the homosphere, Latin and common name.


title: Cloud

text: Genus types in the troposphere, the atmospheric layer closest to Earth's surface, have Latin names because of the universal adoption of Luke Howard's nomenclature that was formally proposed in 1802. It became the basis of a modern international system that divides clouds into five physical "forms" which can be further divided or classified into altitude "levels" to derive ten basic "genera". The main representative cloud types for each of these forms are stratiform, cumuliform, stratocumuliform, cumulonimbiform, and cirriform. "Low-level" clouds do not have any altitude-related prefixes. However "mid-level" stratiform and stratocumuliform types are given the prefix "alto-" while "high-level" variants of these same two forms carry the prefix "cirro-". In both cases, "strato-" is dropped from the latter form to avoid double-prefixing. Genus types with sufficient vertical extent to occupy more than one level do not carry any altitude related prefixes. They are classified formally as low- or mid-level depending on the altitude at which each initially forms, and are also more informally characterized as "multi-level" or "vertical". Most of the ten genera derived by this method of classification can be subdivided into "species" and further subdivided into "varieties". Very low stratiform clouds that extend down to the Earth's surface are given the common names "fog" and "mist", but have no Latin names.


title: Cloud

text: In the stratosphere and mesosphere, clouds have common names for their main types. They may have the appearance of stratiform veils or sheets, cirriform wisps, or stratocumuliform bands or ripples. They are seen infrequently, mostly in the polar regions of Earth. Clouds have been observed in the atmospheres of other planets and moons in the Solar System and beyond. However, due to their different temperature characteristics, they are often composed of other substances such as methane, ammonia, and sulfuric acid, as well as water.


title: Cloud

text: Tropospheric clouds can have a direct effect on climate change on Earth. They may reflect incoming rays from the sun which can contribute to a cooling effect where and when these clouds occur, or trap longer wave radiation that reflects back up from the Earth's surface which can cause a warming effect. The altitude, form, and thickness of the clouds are the main factors that affect the local heating or cooling of Earth and the atmosphere. Clouds that form above the troposphere are too scarce and too thin to have any influence on climate change. Clouds are the main uncertainty in climate sensitivity.


title: Cloud

text: The origin of the term "cloud" can be found in the Old English words "clud" or "clod", meaning a hill or a mass of stone. Around the beginning of the 13th century, the word came to be used as a metaphor for rain clouds, because of the similarity in appearance between a mass of rock and cumulus heap cloud. Over time, the metaphoric usage of the word supplanted the Old English "", which had been the literal term for clouds in general.


title: Cloud

text: The table that follows is very broad in scope like the cloud template that follows it. There are some variations in styles of nomenclature between the classification scheme used for the troposphere (strict Latin except for surface based aerosols) and the higher levels of the homosphere (common terms, some informally derived from Latin). However, the schemes presented here share a cross-classification of physical forms and altitude levels to derive the 10 tropospheric genera, the fog and mist that forms at surface level, and several additional major types above the troposphere. The cumulus genus includes four species that indicate vertical size which can affect the altitude levels.


title: Cloud

text: Ancient cloud studies were not made in isolation, but were observed in combination with other weather elements and even other natural sciences. Around 340 BC, Greek philosopher Aristotle wrote "Meteorologica", a work which represented the sum of knowledge of the time about natural science, including weather and climate. For the first time, precipitation and the clouds from which precipitation fell were called meteors, which originate from the Greek word "meteoros", meaning 'high in the sky'. From that word came the modern term meteorology, the study of clouds and weather. "Meteorologica" was based on intuition and simple observation, but not on what is now considered the scientific method. Nevertheless, it was the first known work that attempted to treat a broad range of meteorological topics in a systematic way, especially the hydrological cycle.


title: Cloud

text: After centuries of speculative theories about the formation and behavior of clouds, the first truly scientific studies were undertaken by Luke Howard in England and Jean-Baptiste Lamarck in France. Howard was a methodical observer with a strong grounding in the Latin language, and used his background to formally classify the various tropospheric cloud types during 1802. He believed that scientific observations of the changing cloud forms in the sky could unlock the key to weather forecasting.


title: Cloud

text: Lamarck had worked independently on cloud classification the same year and had come up with a different naming scheme that failed to make an impression even in his home country of France because it used unusually descriptive and informal French names and phrases for cloud types. His system of nomenclature included 12 categories of clouds, with such names as (translated from French) hazy clouds, dappled clouds, and broom-like clouds. By contrast, Howard used universally accepted Latin, which caught on quickly after it was published in 1803. As a sign of the popularity of the naming scheme, German dramatist and poet Johann Wolfgang von Goethe composed four poems about clouds, dedicating them to Howard.


title: Cloud

text: An elaboration of Howard's system was eventually formally adopted by the International Meteorological Conference in 1891. This system covered only the tropospheric cloud types. However, the discovery of clouds above the troposphere during the late 19th century eventually led to the creation of separate classification schemes that reverted to the use of descriptive common names and phrases that somewhat recalled Lamarck's methods of classification. These very high clouds, although classified by these different methods, are nevertheless broadly similar to some cloud forms identified in the troposphere with Latin names.


title: Cloud

text: Terrestrial clouds can be found throughout most of the homosphere, which includes the troposphere, stratosphere, and mesosphere. Within these layers of the atmosphere, air can become saturated as a result of being cooled to its dew point or by having moisture added from an adjacent source. In the latter case, saturation occurs when the dew point is raised to the ambient air temperature.


title: Cloud

text: Adiabatic cooling occurs when one or more of three possible lifting agents – convective, cyclonic/frontal, or orographic – cause a parcel of air containing invisible water vapor to rise and cool to its dew point, the temperature at which the air becomes saturated. The main mechanism behind this process is adiabatic cooling. As the air is cooled to its dew point and becomes saturated, water vapor normally condenses to form cloud drops. This condensation normally occurs on cloud condensation nuclei such as salt or dust particles that are small enough to be held aloft by normal circulation of the air.


title: Cloud

text: One agent is the convective upward motion of air caused by daytime solar heating at surface level. Airmass instability allows for the formation of cumuliform clouds that can produce showers if the air is sufficiently moist. On moderately rare occasions, convective lift can be powerful enough to penetrate the tropopause and push the cloud top into the stratosphere.


title: Cloud

text: Frontal and cyclonic lift occur when stable air is forced aloft at weather fronts and around centers of low pressure by a process called convergence. Warm fronts associated with extratropical cyclones tend to generate mostly cirriform and stratiform clouds over a wide area unless the approaching warm airmass is unstable, in which case cumulus congestus or cumulonimbus clouds are usually embedded in the main precipitating cloud layer. Cold fronts are usually faster moving and generate a narrower line of clouds, which are mostly stratocumuliform, cumuliform, or cumulonimbiform depending on the stability of the warm airmass just ahead of the front.


title: Cloud

text: A third source of lift is wind circulation forcing air over a physical barrier such as a mountain (orographic lift). If the air is generally stable, nothing more than lenticular cap clouds form. However, if the air becomes sufficiently moist and unstable, orographic showers or thunderstorms may appear.


title: Cloud

text: Along with adiabatic cooling that requires a lifting agent, three major nonadiabatic mechanisms exist for lowering the temperature of the air to its dew point. Conductive, radiational, and evaporative cooling require no lifting mechanism and can cause condensation at surface level resulting in the formation of fog.


title: Cloud

text: Several main sources of water vapor can be added to the air as a way of achieving saturation without any cooling process: evaporation from surface water or moist ground, precipitation or virga, and transpiration from plants.


title: Cloud

text: Tropospheric classification is based on a hierarchy of categories with physical forms and altitude levels at the top. These are cross-classified into a total of ten genus types, most of which can be divided into species and further subdivided into varieties which are at the bottom of the hierarchy.


title: Cloud

text: Clouds in the troposphere assume five physical forms based on structure and process of formation. These forms are commonly used for the purpose of satellite analysis. They are given below in approximate ascending order of instability or convective activity.


title: Cloud

text: Tropospheric clouds form in any of three levels (formerly called "étages") based on altitude range above the Earth's surface. The grouping of clouds into levels is commonly done for the purposes of cloud atlases, surface weather observations, and weather maps. The base-height range for each level varies depending on the latitudinal geographical zone. Each altitude level comprises two or three genus-types differentiated mainly by physical form.


title: Cloud

text: The standard levels and genus-types are summarised below in approximate descending order of the altitude at which each is normally based. Multi-level clouds with significant vertical extent are separately listed and summarized in approximate ascending order of instability or convective activity.


title: Cloud

text: High clouds form at altitudes of in the polar regions, in the temperate regions, and in the tropics. All cirriform clouds are classified as high, thus constitute a single genus "cirrus" (Ci). Stratocumuliform and stratiform clouds in the high altitude range carry the prefix "cirro-", yielding the respective genus names "cirrocumulus" (Cc) and "cirrostratus" (Cs). If limited-resolution satellite images of high clouds are analysed without supporting data from direct human observations, distinguishing between individual forms or genus types becomes impossible, and they are collectively identified as "high-type" (or informally as "cirrus-type", though not all high clouds are of the cirrus form or genus).


title: Cloud

text: Nonvertical clouds in the middle level are prefixed by "alto-", yielding the genus names "altocumulus" (Ac) for stratocumuliform types and "altostratus" (As) for stratiform types. These clouds can form as low as above surface at any latitude, but may be based as high as near the poles, at midlatitudes, and in the tropics. As with high clouds, the main genus types are easily identified by the human eye, but distinguishing between them using satellite photography alone is not possible. When the supporting data of human observations are not available, these clouds are usually collectively identified as "middle-type" on satellite images.


title: Cloud

text: Low clouds are found from near the surface up to . Genus types in this level either have no prefix or carry one that refers to a characteristic other than altitude. Clouds that form in the low level of the troposphere are generally of larger structure than those that form in the middle and high levels, so they can usually be identified by their forms and genus types using satellite photography alone.


title: Cloud

text: These clouds have low- to mid-level bases that form anywhere from near the surface to about and tops that can extend into the mid-altitude range and sometimes higher in the case of nimbostratus.


title: Cloud

text: These very large cumuliform and cumulonimbiform types have cloud bases in the same low- to mid-level range as the multi-level and moderate vertical types, but the tops nearly always extend into the high levels. Unlike less vertically developed clouds, they are required to be identified by their standard names or abbreviations in all aviation observations (METARS) and forecasts (TAFS) to warn pilots of possible severe weather and turbulence.


title: Cloud

text: Genus types are commonly divided into subtypes called "species" that indicate specific structural details which can vary according to the stability and windshear characteristics of the atmosphere at any given time and location. Despite this hierarchy, a particular species may be a subtype of more than one genus, especially if the genera are of the same physical form and are differentiated from each other mainly by altitude or level. There are a few species, each of which can be associated with genera of more than one physical form. The species types are grouped below according to the physical forms and genera with which each is normally associated. The forms, genera, and species are listed from left to right in approximate ascending order of instability or convective activity.


title: Cloud

text: Of the non-convective stratiform group, high-level cirrostratus comprises two species. Cirrostratus "nebulosus" has a rather diffuse appearance lacking in structural detail. Cirrostratus "fibratus" is a species made of semi-merged filaments that are transitional to or from cirrus. Mid-level altostratus and multi-level nimbostratus always have a flat or diffuse appearance and are therefore not subdivided into species. Low stratus is of the species nebulosus except when broken up into ragged sheets of stratus fractus (see below).


title: Cloud

text: Cirriform clouds have three non-convective species that can form in "stable" airmass conditions. Cirrus fibratus comprise filaments that may be straight, wavy, or occasionally twisted by wind shear. The species "uncinus" is similar but has upturned hooks at the ends. Cirrus "spissatus" appear as opaque patches that can show light grey shading.


title: Cloud

text: Stratocumuliform genus-types (cirrocumulus, altocumulus, and stratocumulus) that appear in mostly stable air with limited convection have two species each. The "stratiformis" species normally occur in extensive sheets or in smaller patches where there is only minimal convective activity. Clouds of the "lenticularis" species tend to have lens-like shapes tapered at the ends. They are most commonly seen as orographic mountain-wave clouds, but can occur anywhere in the troposphere where there is strong wind shear combined with sufficient airmass stability to maintain a generally flat cloud structure. These two species can be found in the high, middle, or low levels of the troposphere depending on the stratocumuliform genus or genera present at any given time.


title: Cloud

text: The species "fractus" shows "variable" instability because it can be a subdivision of genus-types of different physical forms that have different stability characteristics. This subtype can be in the form of ragged but mostly "stable" stratiform sheets (stratus fractus) or small ragged cumuliform heaps with somewhat greater instability (cumulus fractus). When clouds of this species are associated with precipitating cloud systems of considerable vertical and sometimes horizontal extent, they are also classified as "accessory clouds" under the name "pannus" (see section on supplementary features).


title: Cloud

text: These species are subdivisions of genus types that can occur in partly unstable air with limited convection. The species "castellanus" appears when a mostly stable stratocumuliform or cirriform layer becomes disturbed by localized areas of airmass instability, usually in the morning or afternoon. This results in the formation of embedded cumuliform buildups arising from a common stratiform base. Castellanus resembles the turrets of a castle when viewed from the side, and can be found with stratocumuliform genera at any tropospheric altitude level and with limited-convective patches of high-level cirrus. Tufted clouds of the more detached "floccus" species are subdivisions of genus-types which may be cirriform or stratocumuliform in overall structure. They are sometimes seen with cirrus, cirrocumulus, altocumulus, and stratocumulus.


title: Cloud

text: A newly recognized species of stratocumulus or altocumulus has been given the name "volutus", a roll cloud that can occur ahead of a cumulonimbus formation. There are some volutus clouds that form as a consequence of interactions with specific geographical features rather than with a parent cloud. Perhaps the strangest geographically specific cloud of this type is the Morning Glory, a rolling cylindrical cloud that appears unpredictably over the Gulf of Carpentaria in Northern Australia. Associated with a powerful "ripple" in the atmosphere, the cloud may be "surfed" in glider aircraft.


title: Cloud

text: More general airmass instability in the troposphere tends to produce clouds of the more freely convective cumulus genus type, whose species are mainly indicators of degrees of atmospheric instability and resultant vertical development of the clouds. A cumulus cloud initially forms in the low level of the troposphere as a cloudlet of the species "humilis" that shows only slight vertical development. If the air becomes more unstable, the cloud tends to grow vertically into the species "mediocris", then strongly convective "congestus", the tallest cumulus species which is the same type that the International Civil Aviation Organization refers to as 'towering cumulus'.


title: Cloud

text: With highly unstable atmospheric conditions, large cumulus may continue to grow into even more strongly convective cumulonimbus "calvus" (essentially a very tall congestus cloud that produces thunder), then ultimately into the species "capillatus" when supercooled water droplets at the top of the cloud turn into ice crystals giving it a cirriform appearance.


title: Cloud

text: Genus and species types are further subdivided into "varieties" whose names can appear after the species name to provide a fuller description of a cloud. Some cloud varieties are not restricted to a specific altitude level or form, and can therefore be common to more than one genus or species.


title: Cloud

text: All cloud varieties fall into one of two main groups. One group identifies the opacities of particular low and mid-level cloud structures and comprises the varieties "translucidus" (thin translucent), "perlucidus" (thick opaque with translucent or very small clear breaks), and "opacus" (thick opaque). These varieties are always identifiable for cloud genera and species with variable opacity. All three are associated with the stratiformis species of altocumulus and stratocumulus. However, only two varieties are seen with altostratus and stratus nebulosus whose uniform structures prevent the formation of a perlucidus variety. Opacity-based varieties are not applied to high clouds because they are always translucent, or in the case of cirrus spissatus, always opaque.


title: Cloud

text: A second group describes the occasional arrangements of cloud structures into particular patterns that are discernible by a surface-based observer (cloud fields usually being visible only from a significant altitude above the formations). These varieties are not always present with the genera and species with which they are otherwise associated, but only appear when atmospheric conditions favor their formation. "Intortus" and "vertebratus" varieties occur on occasion with cirrus fibratus. They are respectively filaments twisted into irregular shapes, and those that are arranged in fishbone patterns, usually by uneven wind currents that favor the formation of these varieties. The variety "radiatus" is associated with cloud rows of a particular type that appear to converge at the horizon. It is sometimes seen with the fibratus and uncinus species of cirrus, the stratiformis species of altocumulus and stratocumulus, the mediocris and sometimes humilis species of cumulus, and with the genus altostratus.


title: Cloud

text: Another variety, "duplicatus" (closely spaced layers of the same type, one above the other), is sometimes found with cirrus of both the fibratus and uncinus species, and with altocumulus and stratocumulus of the species stratiformis and lenticularis. The variety "undulatus" (having a wavy undulating base) can occur with any clouds of the species stratiformis or lenticularis, and with altostratus. It is only rarely observed with stratus nebulosus. The variety "lacunosus" is caused by localized downdrafts that create circular holes in the form of a honeycomb or net. It is occasionally seen with cirrocumulus and altocumulus of the species stratiformis, castellanus, and floccus, and with stratocumulus of the species stratiformis and castellanus.


title: Cloud

text: It is possible for some species to show combined varieties at one time, especially if one variety is opacity-based and the other is pattern-based. An example of this would be a layer of altocumulus stratiformis arranged in seemingly converging rows separated by small breaks. The full technical name of a cloud in this configuration would be "altocumulus stratiformis radiatus perlucidus", which would identify respectively its genus, species, and two combined varieties.


title: Cloud

text: Supplementary features and accessory clouds are not further subdivisions of cloud types below the species and variety level. Rather, they are either "hydrometeors" or special cloud types with their own Latin names that form in association with certain cloud genera, species, and varieties. Supplementary features, whether in the form of clouds or precipitation, are directly attached to the main genus-cloud. Accessory clouds, by contrast, are generally detached from the main cloud.


title: Cloud

text: One group of supplementary features are not actual cloud formations, but precipitation that falls when water droplets or ice crystals that make up visible clouds have grown too heavy to remain aloft. "Virga" is a feature seen with clouds producing precipitation that evaporates before reaching the ground, these being of the genera cirrocumulus, altocumulus, altostratus, nimbostratus, stratocumulus, cumulus, and cumulonimbus.


title: Cloud

text: When the precipitation reaches the ground without completely evaporating, it is designated as the feature "praecipitatio". This normally occurs with altostratus opacus, which can produce widespread but usually light precipitation, and with thicker clouds that show significant vertical development. Of the latter, "upward-growing" cumulus mediocris produces only isolated light showers, while "downward growing" nimbostratus is capable of heavier, more extensive precipitation. Towering vertical clouds have the greatest ability to produce intense precipitation events, but these tend to be localized unless organized along fast-moving cold fronts. Showers of moderate to heavy intensity can fall from cumulus congestus clouds. Cumulonimbus, the largest of all cloud genera, has the capacity to produce very heavy showers. Low stratus clouds usually produce only light precipitation, but this always occurs as the feature praecipitatio due to the fact this cloud genus lies too close to the ground to allow for the formation of virga.


title: Cloud

text: "Incus" is the most type-specific supplementary feature, seen only with cumulonimbus of the species capillatus. A cumulonimbus incus cloud top is one that has spread out into a clear anvil shape as a result of rising air currents hitting the stability layer at the tropopause where the air no longer continues to get colder with increasing altitude.


title: Cloud

text: The "mamma" feature forms on the bases of clouds as downward-facing bubble-like protuberances caused by localized downdrafts within the cloud. It is also sometimes called "mammatus", an earlier version of the term used before a standardization of Latin nomenclature brought about by the World Meteorological Organization during the 20th century. The best-known is cumulonimbus with mammatus, but the mamma feature is also seen occasionally with cirrus, cirrocumulus, altocumulus, altostratus, and stratocumulus.


title: Cloud

text: A "tuba" feature is a cloud column that may hang from the bottom of a cumulus or cumulonimbus. A newly formed or poorly organized column might be comparatively benign, but can quickly intensify into a funnel cloud or tornado.


title: Cloud

text: An "arcus" feature is a roll cloud with ragged edges attached to the lower front part of cumulus congestus or cumulonimbus that forms along the leading edge of a squall line or thunderstorm outflow. A large arcus formation can have the appearance of a dark menacing arch.


title: Cloud

text: Several new supplementary features have been formally recognized by the World Meteorological Organization (WMO). The feature "fluctus" can form under conditions of strong atmospheric wind shear when a stratocumulus, altocumulus, or cirrus cloud breaks into regularly spaced crests. This variant is sometimes known informally as a Kelvin–Helmholtz (wave) cloud. This phenomenon has also been observed in cloud formations over other planets and even in the sun's atmosphere. Another highly disturbed but more chaotic wave-like cloud feature associated with stratocumulus or altocumulus cloud has been given the Latin name "asperitas". The supplementary feature "cavum" is a circular fall-streak hole that occasionally forms in a thin layer of supercooled altocumulus or cirrocumulus. Fall streaks consisting of virga or wisps of cirrus are usually seen beneath the hole as ice crystals fall out to a lower altitude. This type of hole is usually larger than typical lacunosus holes. A "murus" feature is a cumulonimbus wall cloud with a lowering, rotating cloud base than can lead to the development of tornadoes. A "cauda" feature is a tail cloud that extends horizontally away from the murus cloud and is the result of air feeding into the storm.


title: Cloud

text: Supplementary cloud formations detached from the main cloud are known as accessory clouds. The heavier precipitating clouds, nimbostratus, towering cumulus (cumulus congestus), and cumulonimbus typically see the formation in precipitation of the "pannus" feature, low ragged clouds of the genera and species cumulus fractus or stratus fractus.


title: Cloud

text: A group of accessory clouds comprise formations that are associated mainly with upward-growing cumuliform and cumulonimbiform clouds of free convection. "Pileus" is a cap cloud that can form over a cumulonimbus or large cumulus cloud, whereas a "velum" feature is a thin horizontal sheet that sometimes forms like an apron around the middle or in front of the parent cloud. An accessory cloud recently officially recognized by the World meteorological Organization is the "flumen", also known more informally as the "beaver's tail". It is formed by the warm, humid inflow of a super-cell thunderstorm, and can be mistaken for a tornado. Although the flumen can indicate a tornado risk, it is similar in appearance to pannus or scud clouds and does not rotate.


title: Cloud

text: Clouds initially form in clear air or become clouds when fog rises above surface level. The genus of a newly formed cloud is determined mainly by air mass characteristics such as stability and moisture content. If these characteristics change over time, the genus tends to change accordingly. When this happens, the original genus is called a "mother cloud". If the mother cloud retains much of its original form after the appearance of the new genus, it is termed a "genitus" cloud. One example of this is "stratocumulus cumulogenitus", a stratocumulus cloud formed by the partial spreading of a cumulus type when there is a loss of convective lift. If the mother cloud undergoes a complete change in genus, it is considered to be a "mutatus" cloud.


title: Cloud

text: The genitus and mutatus categories have been expanded to include certain types that do not originate from pre-existing clouds. The term "flammagenitus" (Latin for 'fire-made') applies to cumulus congestus or cumulonimbus that are formed by large scale fires or volcanic eruptions. Smaller low-level "pyrocumulus" or "fumulus" clouds formed by contained industrial activity are now classified as cumulus "homogenitus" (Latin for 'man-made'). Contrails formed from the exhaust of aircraft flying in the upper level of the troposphere can persist and spread into formations resembling cirrus which are designated cirrus "homogenitus". If a cirrus homogenitus cloud changes fully to any of the high-level genera, they are termed cirrus, cirrostratus, or cirrocumulus "homomutatus". Stratus cataractagenitus (Latin for 'cataract-made') are generated by the spray from waterfalls. "Silvagenitus" (Latin for 'forest-made') is a stratus cloud that forms as water vapor is added to the air above a forest canopy.


title: Cloud

text: Stratocumulus clouds can be organized into "fields" that take on certain specially classified shapes and characteristics. In general, these fields are more discernible from high altitudes than from ground level. They can often be found in the following forms:


title: Cloud

text: These patterns are formed from a phenomenon known as a Kármán vortex which is named after the engineer and fluid dynamicist Theodore von Kármán. Wind driven clouds can form into parallel rows that follow the wind direction. When the wind and clouds encounter high elevation land features such as a vertically prominent islands, they can form eddies around the high land masses that give the clouds a twisted appearance.


title: Cloud

text: Although the local distribution of clouds can be significantly influenced by topography, the global prevalence of cloud cover in the troposphere tends to vary more by latitude. It is most prevalent in and along low pressure zones of surface tropospheric convergence which encircle the Earth close to the equator and near the 50th parallels of latitude in the northern and southern hemispheres. The adiabatic cooling processes that lead to the creation of clouds by way of lifting agents are all associated with convergence; a process that involves the horizontal inflow and accumulation of air at a given location, as well as the rate at which this happens.<ref name="Convergence/divergence"></ref> Near the equator, increased cloudiness is due to the presence of the low-pressure Intertropical Convergence Zone (ITCZ) where very warm and unstable air promotes mostly cumuliform and cumulonimbiform clouds. Clouds of virtually any type can form along the mid-latitude convergence zones depending on the stability and moisture content of the air. These extratropical convergence zones are occupied by the polar fronts where air masses of polar origin meet and clash with those of tropical or subtropical origin. This leads to the formation of weather-making extratropical cyclones composed of cloud systems that may be stable or unstable to varying degrees according to the stability characteristics of the various airmasses that are in conflict.


title: Cloud

text: Divergence is the opposite of convergence. In the Earth's troposphere, it involves the horizontal outflow of air from the upper part of a rising column of air, or from the lower part of a subsiding column often associated with an area or ridge of high pressure. Cloudiness tends to be least prevalent near the poles and in the subtropics close to the 30th parallels, north and south. The latter are sometimes referred to as the horse latitudes. The presence of a large-scale high-pressure subtropical ridge on each side of the equator reduces cloudiness at these low latitudes. Similar patterns also occur at higher latitudes in both hemispheres.


title: Cloud

text: The luminance or brightness of a cloud is determined by how light is reflected, scattered, and transmitted by the cloud's particles. Its brightness may also be affected by the presence of haze or photometeors such as halos and rainbows. In the troposphere, dense, deep clouds exhibit a high reflectance (70% to 95%) throughout the visible spectrum. Tiny particles of water are densely packed and sunlight cannot penetrate far into the cloud before it is reflected out, giving a cloud its characteristic white color, especially when viewed from the top. Cloud droplets tend to scatter light efficiently, so that the intensity of the solar radiation decreases with depth into the gases. As a result, the cloud base can vary from a very light to very-dark-grey depending on the cloud's thickness and how much light is being reflected or transmitted back to the observer. High thin tropospheric clouds reflect less light because of the comparatively low concentration of constituent ice crystals or supercooled water droplets which results in a slightly off-white appearance. However, a thick dense ice-crystal cloud appears brilliant white with pronounced grey shading because of its greater reflectivity.


title: Cloud

text: As a tropospheric cloud matures, the dense water droplets may combine to produce larger droplets. If the droplets become too large and heavy to be kept aloft by the air circulation, they will fall from the cloud as rain. By this process of accumulation, the space between droplets becomes increasingly larger, permitting light to penetrate farther into the cloud. If the cloud is sufficiently large and the droplets within are spaced far enough apart, a percentage of the light that enters the cloud is not reflected back out but is absorbed giving the cloud a darker look. A simple example of this is one's being able to see farther in heavy rain than in heavy fog. This process of reflection/absorption is what causes the range of cloud color from white to black.


title: Cloud

text: Striking cloud colorations can be seen at any altitude, with the color of a cloud usually being the same as the incident light. During daytime when the sun is relatively high in the sky, tropospheric clouds generally appear bright white on top with varying shades of grey underneath. Thin clouds may look white or appear to have acquired the color of their environment or background. Red, orange, and pink clouds occur almost entirely at sunrise/sunset and are the result of the scattering of sunlight by the atmosphere. When the sun is just below the horizon, low-level clouds are gray, middle clouds appear rose-colored, and high clouds are white or off-white. Clouds at night are black or dark grey in a moonless sky, or whitish when illuminated by the moon. They may also reflect the colors of large fires, city lights, or auroras that might be present.


title: Cloud

text: A cumulonimbus cloud that appears to have a greenish or bluish tint is a sign that it contains extremely high amounts of water; hail or rain which scatter light in a way that gives the cloud a blue color. A green colorization occurs mostly late in the day when the sun is comparatively low in the sky and the incident sunlight has a reddish tinge that appears green when illuminating a very tall bluish cloud. Supercell type storms are more likely to be characterized by this but any storm can appear this way. Coloration such as this does not directly indicate that it is a severe thunderstorm, it only confirms its potential. Since a green/blue tint signifies copious amounts of water, a strong updraft to support it, high winds from the storm raining out, and wet hail; all elements that improve the chance for it to become severe, can all be inferred from this. In addition, the stronger the updraft is, the more likely the storm is to undergo tornadogenesis and to produce large hail and high winds.


title: Cloud

text: Yellowish clouds may be seen in the troposphere in the late spring through early fall months during forest fire season. The yellow color is due to the presence of pollutants in the smoke. Yellowish clouds are caused by the presence of nitrogen dioxide and are sometimes seen in urban areas with high air pollution levels.


title: Cloud

text: Tropospheric clouds exert numerous influences on Earth's troposphere and climate. First and foremost, they are the source of precipitation, thereby greatly influencing the distribution and amount of precipitation. Because of their differential buoyancy relative to surrounding cloud-free air, clouds can be associated with vertical motions of the air that may be convective, frontal, or cyclonic. The motion is upward if the clouds are less dense because condensation of water vapor releases heat, warming the air and thereby decreasing its density. This can lead to downward motion because lifting of the air results in cooling that increases its density. All of these effects are subtly dependent on the vertical temperature and moisture structure of the atmosphere and result in major redistribution of heat that affect the Earth's climate.


title: Cloud

text: The complexity and diversity of clouds in the troposphere is a major reason for difficulty in quantifying the effects of clouds on climate and climate change. On the one hand, white cloud tops promote cooling of Earth's surface by reflecting shortwave radiation (visible and near infrared) from the sun, diminishing the amount of solar radiation that is absorbed at the surface, enhancing the Earth's albedo. Most of the sunlight that reaches the ground is absorbed, warming the surface, which emits radiation upward at longer, infrared, wavelengths. At these wavelengths, however, water in the clouds acts as an efficient absorber. The water reacts by radiating, also in the infrared, both upward and downward, and the downward longwave radiation results in increased warming at the surface. This is analogous to the greenhouse effect of greenhouse gases and water vapor.


title: Cloud

text: High-level genus-types particularly show this duality with both short-wave albedo cooling and long-wave greenhouse warming effects. On the whole, "ice-crystal" clouds in the upper troposphere (cirrus) tend to favor net warming. However, the cooling effect is dominant with mid-level and low clouds, especially when they form in extensive sheets. Measurements by NASA indicate that on the whole, the effects of low and mid-level clouds that tend to promote cooling outweigh the warming effects of high layers and the variable outcomes associated with vertically developed clouds.


title: Cloud

text: As difficult as it is to evaluate the influences of current clouds on current climate, it is even more problematic to predict changes in cloud patterns and properties in a future, warmer climate, and the resultant cloud influences on future climate. In a warmer climate more water would enter the atmosphere by evaporation at the surface; as clouds are formed from water vapor, cloudiness would be expected to increase. But in a warmer climate, higher temperatures would tend to evaporate clouds. Both of these statements are considered accurate, and both phenomena, known as cloud feedbacks, are found in climate model calculations. Broadly speaking, if clouds, especially low clouds, increase in a warmer climate, the resultant cooling effect leads to a negative feedback in climate response to increased greenhouse gases. But if low clouds decrease, or if high clouds increase, the feedback is positive. Differing amounts of these feedbacks are the principal reason for differences in climate sensitivities of current global climate models. As a consequence, much research has focused on the response of low and vertical clouds to a changing climate. Leading global models produce quite different results, however, with some showing increasing low clouds and others showing decreases. For these reasons the role of tropospheric clouds in regulating weather and climate remains a leading source of uncertainty in global warming projections.


title: Cloud

text: Polar stratospheric clouds (PSC's) form in the lowest part of the stratosphere during the winter, at the altitude and during the season that produces the coldest temperatures and therefore the best chances of triggering condensation caused by adiabatic cooling. Moisture is scarce in the stratosphere, so nacreous and non-nacreous cloud at this altitude range is restricted to polar regions in the winter where the air is coldest.


title: Cloud

text: PSC's show some variation in structure according to their chemical makeup and atmospheric conditions, but are limited to a single very high range of altitude of about , so they are not classified into altitude levels, genus types, species, or varieties. There is no Latin nomenclature in the manner of tropospheric clouds, but rather descriptive names using common English.