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42-579: The Ontonagon River's principal tributaries are its West, South, Middle and East branches, all of which flow in part through the Ottawa National Forest : Below the confluence of its various branches, the Ontonagon River flows generally north-northwestwardly for 24.7 miles (39.7 km) in Ontonagon County to the village of Ontonagon , where it flows into Lake Superior . On March 3, 1992,

84-774: 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

126-412: 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 )

168-1021: 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

210-418: 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

252-683: 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

294-490: 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,

336-429: 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

378-835: 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

420-438: 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

462-734: 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

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504-438: 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

546-401: 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

588-409: 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 ) =

630-403: 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 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

672-584: Is home to several clans of the Ojibwa people who coexisted with the Forest's numerous rocky wetlands . They harvested many of the region's mammals , particularly beaver , for their pelts, and sold them to traders from Canada and the eastern United States, such as the traders of the American Fur Company . After the fur trade declined, the nation sold most of the forest in the 1854 Treaty of La Pointe . A part of

714-401: Is the temperature at which the water vapor in a sample of air at constant barometric pressure condenses into liquid water at 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

756-1029: 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,

798-748: 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

840-644: The Ontonagon Boulder , was removed from the west branch of the Ontonagon River and transported in 1842 to Detroit, where it was weighed at 3708 pounds. It is displayed in Washington, D.C. , at the Smithsonian National Museum of Natural History . Ottawa National Forest The Ottawa National Forest is a national forest that covers 993,010 acres (401,860 ha) in the Upper Peninsula of

882-713: The Presque Isle River . As the Black River, a National Wild and Scenic River , falls from near Copper Peak down towards the lake, it tumbles over seven separate mapped and named waterfalls . The Presque Isle river and its major tributary, Copper Creek , have eleven waterfalls, although four of the Presque Isle falls are outside the national forest and are located within the boundaries of the adjacent Porcupine Mountains Wilderness State Park . Underwood Hill, at 1,867 feet (569 m) in altitude (more than 1,200 feet (370 m) above

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924-643: The Sturgeon River Gorge Wilderness near Kenton, Michigan , and the Sylvania Wilderness near Watersmeet, Michigan. The North Country Trail runs through the forest. Hikers can use the trail to access O Kun de Kun Falls . Opened in 1971, the Ottawa Visitor Center offers interpretive programs and exhibits about the natural history and resources of the Forest. The center's mission is to guide visitors to safe, wise and caring use of

966-559: The U.S. state of Michigan . It includes much of Gogebic and Ontonagon counties, as well as slices of Iron , Houghton , Baraga , and Marquette counties. The forest is under the jurisdiction of the U.S. Forest Service . The headquarters are in Ironwood, Michigan , on the Wisconsin border, and the principal visitor center is located in Watersmeet, Michigan , in the southern section of

1008-401: The cloud point . If all the other factors influencing humidity remain constant, at ground level 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

1050-411: The Forest. Dew point The dew point of 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

1092-676: The Forest. These and other towns within and adjacent to the Forest are served by U.S. Highway 2 , one of the principal highways of the Western Upper Peninsula. There are local ranger district offices in Bessemer , Iron River , Kenton , Ontonagon , and Watersmeet. Wooded slopes mark the south shore of Lake Superior within the Ottawa National Forest, particularly within the Black River country between Little Girl's Point and

1134-422: 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

1176-427: 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

1218-401: The air's contact with a colder surface, dew will form on that surface. The dew point 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

1260-426: The air, the condensed water is called either fog or a cloud , depending on its altitude when it forms. If the temperature is below 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,

1302-445: 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 is at a higher elevation than New York, it will tend to have a lower barometric pressure. This means that if

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1344-465: 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 is in the air and how much moisture

1386-411: 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, 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

1428-1082: 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

1470-742: The following reaches of the Ontonagon's upper tributaries were collectively designated the Ontonagon National Wild and Scenic River : The upper courses of the East and Middle branches in the Ottawa National Forest ; the Cisco Branch in its entirety; and approximately the middle section of the West Branch, from Cascade Falls to the Victoria Reservoir. A very large mass of solid, nearly pure copper ,

1512-529: The level of nearby Lake Superior) is the highest elevation in the Presque Isle River drainage area. However, this is not the highest point in the national forest. That honor belongs to an unnamed 1,900-foot (580 m) hill north of Lac Vieux Desert in southeastern Gogebic County. Rain or snow that falls on the north side of this hill flows through the Ontonagon River towards Lake Superior; precipitation on

1554-453: The logging era ended, the heavily exploited forest was partly abandoned. The U.S. federal government established the Ottawa National Forest in 1931, but the forest did not reach its full size until after two large land purchases in 1933 and 1935. In 1935 the national forest reached its maximum size of 1,026,329 acres (4,105 km ). After some privatizations , the Forest reached its current 1.0 million acre (4,000 km ) extent. During

1596-489: 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

1638-518: The nation used some of the proceeds from their fur trapping to purchase lands around Lac Vieux Desert, where their descendants remain today as the Lac Vieux Desert Band of Lake Superior Chippewa . As a result of the construction of the Duluth, South Shore and Atlantic Railway in 1892–1894, the forest was opened to logging . A few parcels of old-growth white pine and red pine remain. After

1680-511: The south side flows through the Wisconsin River to the Gulf of Mexico . The Ottawa National Forest is an area of relatively high precipitation in both winter and summer. Sections of the Forest receive more than 200 inches (500 cm) of snow annually. In winter, Lake Superior, which usually does not freeze over, is itself the source of much of the water vapor that falls in the area. In many of

1722-534: The summer months, moist air carried by southerly winds from the faraway Gulf does not fall below the dew point in temperature until it enters the Lake Superior basin. The forested area is rich in water but poor in topsoil . The glaciers of various Ice Ages , including the most recent Wisconsonian glaciation , scraped much of the forested area down to bare rock or sand. The result is a highly characteristic boreal forest ecosystem . The Ottawa National Forest

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1764-497: The years after World War II , growing automobile tourism made it possible for a wider variety of people to visit the forest. Ottawa National Forest is used for fishing , canoeing , and lake kayaking . In winter, the Forest welcomes cross-country skiers and snowmobilers . The Ottawa National Forest contains three designated U.S. wilderness areas, managed as such by the Forest Service. They are McCormick Wilderness and

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