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"The concept of global warming was created
by and for the Chinese in order to
make U.S. manufacturing non-competitive."
Donald Trump - 6 Nov 2012

USA - Climate

Firefighters on 23 August 2020 battled some of California's largest-ever fires that had forced tens of thousands from their homes and burned one million acres, with further lightning strikes and gusty winds forecast in the days ahead. The two largest blazes -- the SCU Lightning Complex to the south of the San Francisco Bay area, and the LNU Lightning Complex to the north -- are the second and third largest fires in California history. About 119,000 people had been evacuated, with many struggling to find shelter and hesitating to go to centers set up by authorities because of coronavirus risks.

Thousands of lightning strikes had hit the state in the previous week, igniting fires that left smoke blanketing the region, bringing the total area burned to "close to one million acres," or 400,000 hectares, according to CalFire public information officer Jeremy Rahn. That iwa considered a stunning toll this early in California's fire season, which normally runs from August to November, and it came as exhausted firefighters are already struggling to keep up with the far-flung blazes.

The disparate force battling the many blazes now includes 2,400 fire engines, 60 of them from other states, with several hundred more requested, CalFire said. More than 200 aircraft, including 95 fixed-wing planes, are taking part in what CalFire spokesman Daniel Berlant called "a significant air force" dropping loads of water, monitoring the spread of flames or ferrying firefighters and equipment.

Almost 20 fires ravaged California in the summer of 2018. The region was experiencing earlier, longer and more ferocious wildfire seasons due to increasingly hot, dry temperatures. In 2017, more than a dozen massive blazes swept through Northern California, killing 41 people, destroying 6,000 homes and devastating the area's celebrated wine country. Up until then, this had been the deadliest and most destructive series of fires in California's history. In 2018, the Ferguson Fire has devastated Yosemite National Park in California, while the more northerly Carr Fire has burned more than 220,000 acres (81,000 hectares), 1,079 homes and 500 buildings. The largest fire blanketing the region in smoke, however, is the Mendocino complex a merger of two fires which has burned more than 415,000 acres of northern California, 157 homes and 120 other buildings. This made it the largest fire in the states history, surpassing the Thomas Fire of December 2017.

US media said twin hurricanes were unprecedented in the Gulf of Mexico since records began 150 years ago. Tropical Storm Marco strengthened into a hurricane with winds of 75 miles (120 kilometers) per hour, and was forecast to hit the state of Louisiana on 24 August 2020. Tropical Storm Laura hammered Haiti and the Dominican Republic with heavy rain, killing at least 12 people -- 9 in Haiti and three in the Dominican Republic. It was set to become a hurricane on 25 August 2020 that could hit the US coastal region the next day.

America's climate is mostly temperate, but tropical in Hawaii and Florida, arctic in Alaska, semi-arid in the great plains west of the Mississippi River, and arid in the Great Basin of the south-west; low winter temperatures in the north-west are ameliorated occasionally in January and February by warm Chinook winds from the eastern slopes of the Rocky Mountains.

The northern part of the United States, except near the Pacific Coast, has long and severe winters. The snow is deep and covers the ground for months. The lakes and rivers are frozen and furnish an abundance of ice. The summer is short, but often very hot. The summer days are very long, however, so that there is enough sunlight and warmth to ripen enormous crops of wheat, oats, and other grains. In the central part of the United States, the summers are very hot and the winters are cold.

In the north central part of the United States, however, the air is so dry that extremes of heat and cold do not cause so great discomfort as they would cause near the ocean. The Pacific coast of the United States has two seasons, a dry summer and a rainy winter. The temperature is mild the year round. Even as far north as the mouth of the Columbia River and Puget Sound, flowers may be gathered every day of the year.

The southern part of the United States is warm. In the most southern portions near the Gulf of Mexico snow never falls and frosts are rare, in some places even unknown. Somewhat farther north the winters are very short and mild; snow falls seldom, perhaps once or twice a year, and frosts are not common.

The risks of natural disasters and severe weather are much greater than in Europe. Before any excursion to a nature park or road trip, it is advisable to obtain information about the weather forecast and to follow the instructions given by the local authorities in the event of a storm or tornado warning. In natural parks, especially in the mountains and in the desert regions, it is advisable not to deviate from the marked trails and to inform themselves systematically with the local guides.

Hurricane risks are common on both the Atlantic and Gulf of Mexico and to a lesser extent on the coasts of Georgia and From Caroline between the beginning of June and October. The island of Puerto Rico is affected very frequently by tropical depressions whose exact trajectory is always difficult to predict. Two phases of warning: "Hurricane Watch" or observation, and "Hurricane Warning", when the threat becomes clear (also valid in case of tornadoes, floods and sudden floods - "flash floods"). Hurricanes are classified into 5 categories (5 means a speed of 250 km / hour). During the hurricane season (June to November), landslides, mudslides, flooding and disruptions to essential services may also occur.

Climate is the aggregate of day-to-day weather conditions over a period of many years. It is the result of the interaction of many different elements, the most important of which are temperature and precipitation.

Climatic patterns are a result of the interaction of three geographic controls. The first is latitude. The earth is tilted on its axis with reference to the plane of its orbit around the sun. As it makes its annual revolution around the sun, first the Northern Hemisphere and then the Southern are exposed to the more direct rays of the sun. During the Northern Hemisphere's summer, higher latitude locations have longer days, with far northern points experiencing a period of continuous daylight. Daylight periods during the winter months are shorter at higher latitudes, whereas more southerly locations have both longer days and exposure to more direct rays of the sun.

The second control is based on the relationship between land and water. Land tends to heat and cool more rapidly than water. In a tendency called continentality, places far from large bodies of water experience greater seasonal extremes of temperature than do coastal communities. Parts of the northern Great Plains experience annual temperature ranges close to 65; annual differences of as much as 100 (from 50 to -50) have been recorded in some locations.

The converse effect occurs at maritime locations, especially on the western coast of continents in the mid-latitudes. These locations have smaller temperature ranges as a result of what is called a maritime influence. Summer and winter extremes are moderated by the movement onshore of prevailing westerly wind systems from the ocean. Horizontal and vertical ocean currents minimize seasonal variations in the surface temperature of the water. The moderated water temperature serves to curb temperature extremes in the air mass above the surface.

Proximity to large water bodies also tends to have a positive influence on precipitation levels, with coastal locations receiving generally higher amounts. The reason for this should be obvious; large water bodies provide greater levels of evaporation and thus increase the amount of moisture in the atmosphere. That, in turn, increases the possibility of precipitation. There are, however, notable exceptions to this rule, including the dry coast of southern California and the Arctic coastline of Alaska.

The third prime geographic influence on climate is topography. Most obvious is the relationship between elevation and temperature, with higher elevations cooler than lower elevations. The influence of topography can be broader, however, because of its effect on wind flow. If a major mountain chain lies astride a normal wind direction, the mountains force the air to rise and cool. As the air mass cools, the amount of moisture that it can hold is reduced. Precipitation results if the cooling causes the relative humidity to reach 100 percent. Moisture falls on the windward side, and the lee is dry. The wettest area in North America is along the Pacific coast from Oregon to southern Alaska, where moisture-laden winds strike mountains along the shore. Average annual precipitation is more than 200 centimeters throughout the area, and in some places exceeds 300 centimeters.

Mountains also can reduce the moderating effects of maritime conditions on temperature, as happens in the interior of the Pacific Northwest. The Western Cordillera (mountain mass) confines West Coast maritime climatic conditions to that coast. Some of the greatest variations in both precipitation and temperature to be found across a small distance anywhere in America exist between the west and east sides of parts of the Coast Ranges. The aridity of the central and northern interior West is due in large part to the barrier effect of the north-south-trending mountain ranges of the West.

East of the Rockies, the topographic effect on precipitation eventually disappears, partly because the eastern mountains are lower and thus pose less of a barrier to moving air, and partly because much of the weather of the interior is a result of conflict between two huge air masses that are unimpeded, one flowing northward from the Gulf of Mexico, and the other flowing southward out of Canada. The contact of these air masses creates what are often violent displays of weather in the region.

This illustrates a fourth major and complex influence on climate, the impact of air mass characteristics and wind systems. America's weather is affected markedly by the confrontation between polar continental air masses (usually cold, dry, and stable) and tropical maritime air masses (warm, moist, and unstable). The former push farthest south in winter, whereas the latter extend farthest north in summer. Most parts of America are subject to a generally westerly wind flow that tends to move weather systems eastward. The continental climate of the interior is thus pushed onto the East Coast.

The interaction of these climatic controls creates a pattern of climatic regionalization. In the East, the principal element in climatic variation is temperature; in the West, it is precipitation. In the East, the divisions between the climate regions are based largely on the length of the growing season--the period from the average date of the last frost in spring to the first frost in fall--and on the average summer maximum temperature or winter minimum temperature. In the West, average annual precipitation is the key, although moderated temperatures are an important aspect of the marine West Coast climate. In the East, the more northerly areas are generally drier; in the West, they are colder. In the East, the major influence on climatic variation is latitude; in the West, it is topography.

The 2020 Atlantic hurricane season started 01 June 2020, and federal scientists expected storms to be more frequent and powerful. Two named storms had already formed in the Atlantic this spring before the official start of the season. As Florida and other coastal states plan for hurricanes, they were confronting troubling new public safety calculations because of the novel coronavirus.

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Page last modified: 28-08-2020 19:46:20 ZULU