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41-487: Milešovka is at an altitude of 837 metres above sea level and therefore has a pronounced alpine climate . This results in the average temperature in the region being three to four degrees Celsius cooler than Prague. 50°33.314′N 13°55.892′E  /  50.555233°N 13.931533°E  / 50.555233; 13.931533 This Ústí nad Labem Region location article is a stub . You can help Misplaced Pages by expanding it . Alpine climate Alpine climate

82-774: A ( T ) a b − ln ⁡ P a ( T ) a ; {\displaystyle {\begin{aligned}P_{\mathrm {s} }(T)&={\frac {100}{\mathrm {RH} }}P_{\mathrm {a} }(T)=ae^{\frac {bT}{c+T}};\\[8pt]P_{\mathrm {a} }(T)&={\frac {\mathrm {RH} }{100}}P_{\mathrm {s} }(T)=ae^{\gamma (T,\mathrm {RH} )}\\&\approx P_{\mathrm {s} }(T_{\mathrm {w} })-BP_{\mathrm {mbar} }0.00066\left(1+0.00115T_{\mathrm {w} }\right)\left(T-T_{\mathrm {w} }\right);\\[8pt]T_{\mathrm {d} }&={\frac {c\ln {\frac {P_{\mathrm {a} }(T)}{a}}}{b-\ln {\frac {P_{\mathrm {a} }(T)}{a}}}};\end{aligned}}} For greater accuracy, P s ( T ) (and therefore γ ( T , RH)) can be enhanced, using part of

123-412: A ( T ) a b − ln ⁡ P a ( T ) a = c ln ⁡ ( R H 100 P s , m ( T ) a ) b − ln ⁡ ( R H 100 P s , m ( T )

164-1021: A ) = c γ m ( T , R H ) b − γ m ( T , R H ) ; {\displaystyle {\begin{aligned}P_{\mathrm {s,m} }(T)&=ae^{\left(b-{\frac {T}{d}}\right)\left({\frac {T}{c+T}}\right)};\\[8pt]\gamma _{\mathrm {m} }(T,\mathrm {RH} )&=\ln \left({\frac {\mathrm {RH} }{100}}e^{\left(b-{\frac {T}{d}}\right)\left({\frac {T}{c+T}}\right)}\right);\\[8pt]T_{d}&={\frac {c\ln {\frac {P_{\mathrm {a} }(T)}{a}}}{b-\ln {\frac {P_{\mathrm {a} }(T)}{a}}}}={\frac {c\ln \left({\frac {\mathrm {RH} }{100}}{\frac {P_{\mathrm {s,m} }(T)}{a}}\right)}{b-\ln \left({\frac {\mathrm {RH} }{100}}{\frac {P_{\mathrm {s,m} }(T)}{a}}\right)}}={\frac {c\gamma _{m}(T,\mathrm {RH} )}{b-\gamma _{m}(T,\mathrm {RH} )}};\end{aligned}}} where There are several different constant sets in use. The ones used in NOAA 's presentation are taken from

205-418: A e γ ( T , R H ) ≈ P s ( T w ) − B P m b a r 0.00066 ( 1 + 0.00115 T w ) ( T − T w ) ; T d = c ln ⁡ P

246-683: A 1980 paper by David Bolton in the Monthly Weather Review : These valuations provide a maximum error of 0.1%, for −30 °C ≤ T ≤ 35°C and 1% < RH < 100% . Also noteworthy is the Sonntag1990, Another common set of values originates from the 1974 Psychrometry and Psychrometric Charts . Also, in the Journal of Applied Meteorology and Climatology , Arden Buck presents several different valuation sets, with different maximum errors for different temperature ranges. Two particular sets provide

287-490: A dew point of approximately 4.0 to 16.5 °C (39 to 62 °F) (by Simple Rule calculation below). Lower dew points, less than 10 °C (50 °F), correlate with lower ambient temperatures and cause the body to require less cooling. A lower dew point can go along with a high temperature only at extremely low relative humidity, allowing for relatively effective cooling. People inhabiting tropical and subtropical climates acclimatize somewhat to higher dew points. Thus,

328-449: A given body of air is the temperature to which it must be cooled to become saturated with water vapor. This temperature depends on the pressure and water content of the air. When the air is cooled below the dew point, its moisture capacity is reduced and airborne water vapor will condense to form liquid water known as dew . When this occurs through the air's contact with a colder surface, dew will form on that surface. The dew point

369-429: A good measure for use in evaluating comfort level. Discomfort also exists when the dew point is very low (below around −5 °C or 23 °F). The drier air can cause skin to crack and become irritated more easily. It will also dry out the airways. The US Occupational Safety and Health Administration recommends indoor air be maintained at 20–24.5 °C (68–76 °F) with a 20–60% relative humidity, equivalent to

410-491: A mountain is roughly equivalent to moving 80 kilometres (50 miles or 0.75° of latitude ) towards the pole. This relationship is only approximate, however, since local factors, such as proximity to oceans , can drastically modify the climate. As the altitude increases, the main form of precipitation becomes snow and the winds increase. The temperature continues to drop until the tropopause , at 11,000 metres (36,000 ft), where it does not decrease further. This

451-835: A range of −40 °C to +50 °C between the two, with even lower maximum error within the indicated range than all the sets above: There is also a very simple approximation that allows conversion between the dew point, temperature, and relative humidity. This approach is accurate to within about ±1 °C as long as the relative humidity is above 50%: T d ≈ T − 100 − R H 5 ; R H ≈ 100 − 5 ( T − T d ) ; {\displaystyle {\begin{aligned}T_{\mathrm {d} }&\approx T-{\frac {100-\mathrm {RH} }{5}};\\[5pt]\mathrm {RH} &\approx 100-5(T-T_{\mathrm {d} });\end{aligned}}} This can be expressed as

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492-438: A relative humidity of 100% means dew point is the same as air temp. For 90% RH, dew point is 3 °F lower than air temperature. For every 10 percent lower, dew point drops 3 °F. The frost point is similar to the dew point in that it is the temperature to which a given parcel of humid air must be cooled, at constant atmospheric pressure , for water vapor to be deposited on a surface as ice crystals without undergoing

533-734: A resident of Singapore or Miami , for example, might have a higher threshold for discomfort than a resident of a temperate climate like London or Chicago . People accustomed to temperate climates often begin to feel uncomfortable when the dew point gets above 15 °C (59 °F), while others might find dew points up to 18 °C (64 °F) comfortable. Most inhabitants of temperate areas will consider dew points above 21 °C (70 °F) oppressive and tropical-like, while inhabitants of hot and humid areas may not find this uncomfortable. Thermal comfort depends not just on physical environmental factors, but also on psychological factors. Devices called hygrometers are used to measure dew point over

574-438: A simple rule of thumb: For every 1 °C difference in the dew point and dry bulb temperatures, the relative humidity decreases by 5%, starting with RH = 100% when the dew point equals the dry bulb temperature. The derivation of this approach, a discussion of its accuracy, comparisons to other approximations, and more information on the history and applications of the dew point, can be found in an article published in

615-401: A wide range of temperatures. These devices consist of a polished metal mirror which is cooled as air is passed over it. The dew point is revealed by observing the loss of clarity in the reflection cast by the mirror. Manual devices of this sort can be used to calibrate other types of humidity sensors, and automatic sensors may be used in a control loop with a humidifier or dehumidifier to control

656-409: Is (unless declared otherwise, all temperatures are expressed in degrees Celsius ): P s ( T ) = 100 R H P a ( T ) = a e b T c + T ; P a ( T ) = R H 100 P s ( T ) =

697-411: Is affected by the air's humidity . The more moisture the air contains, the higher its dew point. When the temperature is below the freezing point of water, the dew point is called the frost point , as frost is formed via deposition rather than condensation. In liquids, the analog to the dew point is the cloud point . If all the other factors influencing humidity remain constant, at ground level

738-538: Is at a higher elevation than New York, it will tend to have a lower barometric pressure. This means that if the dew point and temperature in both cities are the same, the amount of water vapor in the air will be greater in Denver. When the air temperature is high, the human body uses the evaporation of perspiration to cool down, with the cooling effect directly related to how fast the perspiration evaporates. The rate at which perspiration can evaporate depends on how much moisture

779-1027: Is higher than the highest summit . Although this climate classification only covers a small portion of the Earth's surface, alpine climates are widely distributed. They are present in the Himalayas , the Tibetan Plateau , Gansu , Qinghai and Mount Lebanon in Asia ; the Alps , the Urals , the Pyrenees , the Cantabrian Mountains and the Sierra Nevada in Europe ; the Andes in South America ;

820-458: Is in the air and how much moisture the air can hold. If the air is already saturated with moisture (humid), perspiration will not evaporate. The body's thermoregulation will produce perspiration in an effort to keep the body at its normal temperature even when the rate at which it is producing sweat exceeds the evaporation rate, so one can become coated with sweat on humid days even without generating additional body heat (such as by exercising). As

861-453: Is known as the adiabatic lapse rate , which is approximately 9.8 °C per kilometer (or 5.4 °F per 1000 feet) of altitude. The presence of water in the atmosphere complicates the process of convection. Water vapor contains latent heat of vaporization . As air rises and cools, it eventually becomes saturated and cannot hold its quantity of water vapor. The water vapor condenses (forming clouds ), and releases heat, which changes

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902-444: Is the process of convection . Convection comes to equilibrium when a parcel of air at a given altitude has the same density as its surroundings. Air is a poor conductor of heat, so a parcel of air will rise and fall without exchanging heat. This is known as an adiabatic process , which has a characteristic pressure-temperature curve. As the pressure gets lower, the temperature decreases. The rate of decrease of temperature with elevation

943-503: Is the typical climate for elevations above the tree line , where trees fail to grow due to cold. This climate is also referred to as a mountain climate or highland climate . There are multiple definitions of alpine climate. In the Köppen climate classification , the alpine and mountain climates are part of group E , along with the polar climate , where no month has a mean temperature higher than 10 °C (50 °F). According to

984-1029: The Bulletin of the American Meteorological Society . For temperatures in degrees Fahrenheit, these approximations work out to T d , ∘ F ≈ T ∘ F − 9 25 ( 100 − R H ) ; R H ≈ 100 − 25 9 ( T ∘ F − T d , ∘ F ) ; {\displaystyle {\begin{aligned}T_{\mathrm {d,^{\circ }F} }&\approx T_{\mathrm {{}^{\circ }F} }-{\tfrac {9}{25}}\left(100-\mathrm {RH} \right);\\[5pt]\mathrm {RH} &\approx 100-{\tfrac {25}{9}}\left(T_{\mathrm {{}^{\circ }F} }-T_{\mathrm {d,^{\circ }F} }\right);\end{aligned}}} For example,

1025-748: The Bögel modification , also known as the Arden Buck equation , which adds a fourth constant d : P s , m ( T ) = a e ( b − T d ) ( T c + T ) ; γ m ( T , R H ) = ln ⁡ ( R H 100 e ( b − T d ) ( T c + T ) ) ; T d = c ln ⁡ P

1066-567: The Holdridge life zone system, there are two mountain climates which prevent tree growth : a) the alpine climate, which occurs when the mean biotemperature of a location is between 1.5 and 3 °C (34.7 and 37.4 °F). The alpine climate in Holdridge system is roughly equivalent to the warmest tundra climates (ET) in the Köppen system. b) the alvar climate, the coldest mountain climate since

1107-937: The Sierra Nevada , the Cascade Range , the Rocky Mountains , the northern Appalachian Mountains ( Adirondacks and White Mountains ), and the Trans-Mexican Volcanic Belt in North America ; the Southern Alps in New Zealand ; the Snowy Mountains in Australia ; high elevations in the Atlas Mountains , Ethiopian Highlands , and Eastern Highlands of Africa ; the central parts of Borneo and New Guinea ; and

1148-431: The relative humidity rises as the temperature falls; this is because less vapor is needed to saturate the air. In normal conditions, the dew point temperature will not be greater than the air temperature, since relative humidity typically does not exceed 100%. In technical terms, the dew point is the temperature at which the water vapor in a sample of air at constant barometric pressure condenses into liquid water at

1189-427: The air surrounding one's body is warmed by body heat, it will rise and be replaced with other air. If air is moved away from one's body with a natural breeze or a fan, sweat will evaporate faster, making perspiration more effective at cooling the body, thereby increasing comfort. By contrast, comfort decreases as unevaporated perspiration increases. A wet bulb thermometer also uses evaporative cooling , so it provides

1230-419: The biotemperature is between 0 °C and 1.5 °C (biotemperature can never be below 0 °C). It corresponds more or less to the coldest tundra climates and to the ice cap climates (EF) as well. Holdrige reasoned that plants net primary productivity ceases with plants becoming dormant at temperatures below 0 °C (32 °F) and above 30 °C (86 °F). Therefore, he defined biotemperature as

1271-448: The dew point is high and condensation can occur on surfaces that are only a few degrees cooler than the air. A high relative humidity implies that the dew point is close to the current air temperature. A relative humidity of 100% indicates the dew point is equal to the current temperature and that the air is maximally saturated with water. When the moisture content remains constant and temperature increases, relative humidity decreases, but

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1312-1082: The dew point of the air in a building or in a smaller space for a manufacturing process. A well-known empirical approximation used to calculate the dew point, T d , given just the actual ("dry bulb") air temperature, T (in degrees Celsius) and relative humidity (in percent), RH, is the Magnus formula: γ ( T , R H ) = ln ⁡ ( R H 100 ) + b T c + T ; T d = c γ ( T , R H ) b − γ ( T , R H ) ; {\displaystyle {\begin{aligned}\gamma (T,\mathrm {RH} )&=\ln \left({\frac {\mathrm {RH} }{100}}\right)+{\frac {bT}{c+T}};\\[8pt]T_{\mathrm {d} }&={\frac {c\gamma (T,\mathrm {RH} )}{b-\gamma (T,\mathrm {RH} )}};\end{aligned}}} where b = 17.625 and c = 243.04°C. The values of b and c were selected by minimizing

1353-549: The dew point remains constant. General aviation pilots use dew point data to calculate the likelihood of carburetor icing and fog , and to estimate the height of a cumuliform cloud base . Increasing the barometric pressure raises the dew point. This means that, if the pressure increases, the mass of water vapor per volume unit of air must be reduced in order to maintain the same dew point. For example, consider New York City (33 ft or 10 m elevation) and Denver (5,280 ft or 1,610 m elevation ). Because Denver

1394-444: The dew point, and no dew or fog forms, the vapor is called supersaturated . This can happen if there are not enough particles in the air to act as condensation nuclei . The dew point depends on how much water vapor the air contains. If the air is very dry and has few water molecules, the dew point is low and surfaces must be much cooler than the air for condensation to occur. If the air is very humid and contains many water molecules,

1435-440: The lapse rate from the dry adiabatic lapse rate to the moist adiabatic lapse rate (5.5 °C per kilometre or 3 °F per 1000 feet). The actual lapse rate, called the environmental lapse rate , is not constant (it can fluctuate throughout the day or seasonally and also regionally), but a normal lapse rate is 5.5 °C per 1,000 m (3.57 °F per 1,000 ft). Therefore, moving up 100 metres (330 ft) on

1476-489: The maximum deviation over the range -40°C to +50°C. The more complete formulation and origin of this approximation involves the interrelated saturated water vapor pressure (in units of millibars , also called hectopascals ) at T , P s ( T ), and the actual vapor pressure (also in units of millibars), P a ( T ), which can be either found with RH or approximated with the barometric pressure (in millibars), BP mbar , and " wet-bulb " temperature, T w

1517-421: The mean of all temperatures but with all temperatures below freezing and above 30 °C adjusted to 0 °C; that is, the sum of temperatures not adjusted is divided by the number of all temperatures (including both adjusted and non-adjusted ones). The variability of the alpine climate throughout the year depends on the latitude of the location. For tropical oceanic locations, such as the summit of Mauna Loa ,

1558-407: The same rate at which it evaporates. At temperatures below the dew point, the rate of condensation will be greater than that of evaporation, forming more liquid water. The condensed water is called dew when it forms on a solid surface, or frost if it freezes. In the air, the condensed water is called either fog or a cloud , depending on its altitude when it forms. If the temperature is below

1599-605: The summits of Mount Pico in the Atlantic and Mauna Loa in the Pacific . The lowest altitude of alpine climate varies dramatically by latitude. If alpine climate is defined by the tree line, then it occurs as low as 650 metres (2,130 ft) at 68°N in Sweden, while on Mount Kilimanjaro in Tanzania, the tree line is at 3,950 metres (12,960 ft). Dew point The dew point of

1640-403: The surface. If radiation were the only way to transfer heat from the ground to space, the greenhouse effect of gases in the atmosphere would keep the ground at roughly 333 K (60 °C; 140 °F), and the temperature would decay exponentially with height. However, when air is hot, it tends to expand, which lowers its density. Thus, hot air tends to rise and transfer heat upward. This

1681-460: The temperature is roughly constant throughout the year. For mid-latitude locations, such as Mount Washington in New Hampshire , the temperature varies seasonally, but never gets very warm. The temperature profile of the atmosphere is a result of an interaction between radiation and convection . Sunlight in the visible spectrum hits the ground and heats it. The ground then heats the air at

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