Читать книгу Explore it. The USA - Д. С. Ведунова - Страница 5

Due to the large size of the country, its length and wide variety of geographical features in the US, it is possible to find areas with almost any climatic characteristics. Most of the USA (states south of 40 degrees north) is located in the subtropical climate zone, temperate climate prevails to the north, Hawaii and southern Florida lie in the tropics, and the north of Alaska belongs to the polar regions. The great plains to the west of the 100th meridian are classified as semi-deserts, the Great Basin and the areas around it are arid, and the coastal regions of California are a Mediterranean climate. The type of climate within the boundaries of one belt can vary significantly depending on the terrain, the proximity of the ocean and other factors. The favorable climate had a considerable influence on the settlement of the continent by Europeans and in many ways contributed to the US occupying the leading positions in the world.

The overall temperature background is fairly uniform. In summer, the temperature in most areas ranges from +22° C to +28° C, with the difference between the northern and southern states is relatively small. Winter in most of the country is quite mild – the average January temperature ranges from -2° C in the north to +8° C in the south. However, considerable temperature fluctuations are not uncommon due to free penetration of air masses both from the Arctic region and from tropical latitudes (the mountain systems of the USA located in the meridional direction act as a kind of «pipe» through which cyclones and anticyclones move from north to south or vice versa, practically without encountering obstacles). In the mountainous regions it is always cooler than in the adjoining territories of the plains – in the summer by 4—8 degrees, in winter – by 7—12. At the same time, in the pre-oceanic regions in winter it is always warmer, and in the summer it is cooler than in the center of the country (the eastern coast of the country, heated by the warm Gulf Stream, has a temperature 5—7 degrees above all central and western regions).

Depending on the nature of the mountain systems, weather stability also changes markedly: in low Appalachians the climate differs little from the flat areas of the east of the country and is quite constant, while the extensive and high ridges of the Cordillera system are widely known for their cooler, dry and unstable weather.

The nature of the distribution of precipitation is also very uneven. In the southeastern states and on the Pacific coast, it drops to 2000 mm of rain per year, in the Hawaiian Islands – up to 4000 mm and more, while in the central regions of California or Nevada – no more than 200 mm. And the nature of the distribution of precipitation depends entirely on the terrain – the western slopes of the mountains and the Atlantic regions receive significantly more rain than the eastern ones, while in the entire Great Plains, from the coastal lowlands of the south to the wooded areas of the north, there is almost the same amount of precipitation 300—500 mm).

At any time of the year, you can find the US region, where rest would be comfortable in its weather conditions. The swimming season in the north and in the center of the Atlantic coast lasts from June to August-September, although to quite acceptable values the water warms up in May and in October. On the coast of Florida you can swim practically all year round (the average temperature of the water even rarely falls below +22° С even in winter months), however in the period from July to September it is quite hot (+36—39° С) and very high air humidity (up to 100%), and from June to November, tropical hurricanes are not uncommon.

The Pacific coast has a noticeably larger difference in water and air temperatures between the northern and southern regions. In the southern part of the coast, you can swim practically all year round, although in the period from November to March even in California, the temperature of the water rarely rises above +14° C (many seas with well-heated water are used for sea recreation). At the same time in the north, in Oregon and Washington, even in the summer months, there are often noticeable cold snaps of both water and air, in winter the temperature regime is quite common for regions with a temperate marine climate (air from -6 to +4° C, water – about +4° C). Contrary to popular belief, Oregon’s climate is dry enough (rain falls less than in Atlanta or Houston) and warm enough (summer highs rarely exceed +30° C, and in winter the thermometer remains at +2° C). Therefore, you can find excellent opportunities for recreation almost all the year round.

To the north, in the state of Washington, two distinct climatic zones, west of the Cascade Mountains, on the Pacific coast and in Seattle, quite clearly distinguish themselves, in the summer, it is rarely hotter than +26° C, and in the winter – colder +8° C, while the eastern part of the staff has a noticeably warmer summer and a cool winter. Traditionally, the summer tourist season here begins with Memorial Day and continues until Labor Day, and even some of the sights are open to visitors only during this period.

The central mountain areas can be visited all year round, in the southern part of the Rocky Mountains in the summer it is too hot (+26—34° C), therefore it is recommended to plan your trip for the spring or autumn. To avoid the influx of tourists, it is recommended to plan visits to national parks, for example, in late autumn or early spring, when the weather conditions are quite comfortable. The western slopes of the Rocky Mountains and the eastern part of California during the summer are also not very pleasant to visit – too hot, however, the seaside part of the same California at this time has quite pleasant weather conditions.

There are no seasonal restrictions for visiting Los Angeles. Despite its dry and hot semi-desert climate, the city is protected from the burning heat by mountain chains in the north and east, as well as by the Pacific Ocean itself. August and September are the hottest months (+24—30° C), January and February are the coolest (around +12° C) and the wettest, but at any time of the year ocean breezes soften the weather in the direction of greater comfort. However, the city smog combined with the summer heat makes the end of the summer not the best time to visit the metropolis, while the resort areas adjacent to it from the north and south have excellent weather conditions during this period.

The climate of Alaska is quite severe, since 30% of its territory is beyond the Arctic Circle. In northern and central regions with their subarctic climate, the thermometer’s column often drops to -45-50° C in winter, while in summer the air warms up to +16—20° C (in northern regions – +2—6° C) with very low precipitation (about 250 mm per year). In the southern and central regions the climate is temperate marine, the average temperature here in the summer is about +18° C, but often the air warms up to +30° C), in winter – from -6° C to +4° C, precipitation falls from 400 to 600 mm per year.

The vegetation of the USA

Through the territory of the United States there are various climatic zones, and in some parts of this vast country there is a truly unique microclimate in which an amazing plant world has formed.

Of course, the economic development of the North American continent played a role, however, rather large areas, about 30%, are now covered by forests. In general, coniferous species predominate – spruce, pine, fir. In the north-east of the country there are massifs of mixed forests, where, in addition to coniferous trees, grow oaks, maples, plane trees, birches, ash trees, sycamore. In the Mojave Desert, there are also original forests – cactus. In Alaska, the most northerly state of the USA, only mosses and lichens grow, in deserts and semi-deserts – shrubs, yucca, wormwood, quinoa, in alpine and subalpine meadows – heather and other flowering plants. Closer to the south, there are magnolias and rubber trees, on the coast of the Gulf of Mexico – mangrove forests, on the west coast – citrus trees, and in Hawaii – tropical jungles with palm trees, lianas, orchids and other exotic representatives of the flora. Vegetation of national parks and reserves is also unique. In the Yellowstone National Park, which has existed for more than 130 years, there are 1,870 plant species, of which the predominant majority are native species.

Most of the forests of the park are filled with pine conifer. In the undergrowth there are deciduous trees: birch, willow, aspen. In the Everglades National Park, more than 2,000 plant species are represented (different species of mangrove, mahogany, oak, willow, cypress, pine etc.). Also here are preserved in their original form tropical marshes with 25 species of orchids.

In the Zion National Park, there are mixed and coniferous forests, desert and coastal vegetation – only 450 species. In the Yosemite National Park, there are 1600 plant species, of which 160 are endemic. Next to it is broken the Sequoia park, where the tallest trees in the world grow. The highest sequoia called «Hyperion height» has a height of 115.5 meters. The northernmost part of the rain forest in the world is located in the Olympic Park. It is also the wettest area on the mainland of the United States.

Fauna of the USA

The rich fauna of the United States is mainly due to the vast expanses and careful protection of nature, which already had to suffer a lot of troubles from man.

The animal world of the US, although it has some similarities with the European one, however, there are unique animals on the North American continent. To the common animals with Eurasia one can include deer, moose, wolf, hare, sable, ermine, wolverine, woodpeckers, owls, etc. Unique North American animals are porcupines, martens ilka, large flying squirrels, red squirrels, etc.

The nature of the animal world is mainly determined by climatic conditions and vegetation. In broadleaf forests, black bears (baribals) and grizzly bears, virgin deer, red lynx, cougar, possums, skunks, chipmunks are common. In mixed forests live brown bears, lynxes, martens and wolverines. Alaskans arrange seals and walrus rookeries. In the steppes, in addition to large artiodactyls (bison, deer, vilorogie antelope, thick-legged sheep), there are foxes, coyotes, badgers, ferrets. Bison was mercilessly exterminated by man for the sake of valuable skins, but at present they are under the protection of the law. Deserts are inhabited mainly by small mammals (marsupials, etc.), reptiles (snakes, lizards, iguanas), as well as insects (scorpions, spiders, etc.). In the tropical forests of the Gulf Coast there are crocodiles and alligators, as well as anteaters, porcupines and marmosets. In the reservoirs live nutria, muskrats, beavers, as well as amphibians – frogs, toads, newts.

Birds living in the United States are very diverse. In the middle latitudes you can observe owls, vultures, eagles, mockingbirds, cranes, snipe, peregrine falcon, cormorants. In the south of the country there are more exotic species – parrots, flamingos, pelicans, hummingbirds.

The fish world is mainly represented by salmonids – only in the Yellowstone reserve are 18 species. Near the Hawaiian Islands, 600 species of tropical fish adjoin the turtles.

Save a huge species diversity of the animal kingdom of the United States help the extensive national parks and reserves. The largest species diversity of mammals, birds, fish and insects can be found in the national parks of Yellowstone, Everglades, Zion (about 300 bird species), Bryce Canyon (60 mammal species and 160 bird species), Santa Ana (the largest bird sanctuary). In the world-famous Yellowstone Reserve, the largest populations of bison, grizzly bears, pumas and wolverines have been preserved. In the Everglades National Park, where tropical marshes are preserved, there are co-existing Mississippian alligators and sharply crocodiles, as well as numerous bird species, including exotic ones.