Category Science

            Area with a Tropical climate have high temperatures (24°C to 27°C (75°F to 81°F)) throughout the year. The atmosphere is very humid (full of moisture) and the levels of rainfall are very high — at least 150cm (59in) — particularly in those regions close to the Equator.

          Some people assume the word tropical climate refers to their favorite warm vacation spot. However, this is a bit far from the truth since the word tropical is defined differently in meteorology. A tropical climate is identified as a climate characteristic to the tropics; that is from the equator to the Tropic of Capricorn in the south and from the Equator to the Tropic of Cancer in the north. The Koppen climate classification defines a tropical climate as a non-arid climate in which the mean temperature is about 64°F throughout the year. Unlike subtropical regions which are characterized by variations in temperature to different degrees and day length, temperatures in tropical climates, remain relatively constant all year long as variations for different seasons are dominated by rainfall. Tropical climates comprise of only two seasons which are the dry season and the wet season. Changes in solar angle are small in tropical climates which happen to be frost-free. There are different varieties of tropical climates within the tropical climate zone. The different varieties are based on precipitation. Here are the three subtypes of tropical climates.

The Tropical Wet and Dry Climate

          Also known as the Savannah climate, the tropical wet and dry climate experiences a long dry period and less annual rainfall. The driest month in a wet and dry tropical climate has precipitation of less than 2.4 inches and less than 3.9 inches total annual precipitation. The tropical wet and dry climate are mainly found in Lagos, Nigeria; Bangalore, India; Dar es Salaam, Tanzania; Barquisimeto, Venezuela; Darwin, Australia; Honolulu, US; Fort Myers, Florida; Rio de Janeiro, Brazil; and Kupang, Indonesia among others.

The Tropical Monsoon Climate

          A tropical monsoon climate is the type of climate found in the Southern and Central regions of America and the Southeast and Southern parts of Asia as well as parts of Australia and Africa. The tropical monsoon climate is influenced by the monsoon winds which according to the seasons change directions. For this part of the equator, the driest month of the tropical monsoon climate occurs either soon after or at the ‘winter’ solstice. Rainfall is usually less than 2.4 inches but exceeds 3.9 inches total annual precipitation. Examples of the area that experience tropical monsoon climates include Jakarta, Indonesia; Miami, Florida; Abidjan, Ivory Coast; Puerto Ayacucho, Venezuela; Chittagong, Bangladesh; Yangon, Myanmar; Cairns, Australia; and Macapa, Brazil among others.

Tropical Rainforest Climate

          The tropical rainforest climate is found in places that are around the equatorial region usually between 5° to 10° latitude of the equator. However, in several eastern coastal regions, such climates might extend beyond 26° from the equator. Tropical rainforest climates are mainly characterized by low-pressure systems since they are dominated by doldrums thus receiving rainfall all year long. There is no specific season found in the tropical rainforest climate. All 12 months in this type of climate have an average precipitation of at least 2.4 inches. Examples of areas with tropical rainforest climates include Mbandaka, Congo; Singapore; Klang, Malaysia; Hilo, Hawaii; Innisfail, Australia; Apia Samoa, Davao, Philippines; Bogor, Indonesia among others.

Picture Credit : Google

            There are two types of temperate climate — cool and warm. Cool temperate areas have rainfall throughout the year, warm summers, and winters with temperatures often below freezing. The warm temperate climate features mild, wet winters where the temperature rarely gets below 4°C (39°F). The summers are hot and dry, with temperatures averaging 20°C to 27°C (68°F to 81°F).

            In geography, temperate latitudes of the Earth lie between the subtropics and the polar circles. Average yearly temperatures in these regions are not extreme, not burning hot nor freezing cold. Temperate means moderate.

            Unlike in the tropics, temperatures can change greatly here, between summer and winter. So, most places with a temperate climate have four seasons: summer, autumn, winter and spring. Other areas with a temperate climate can have very unpredictable weather. One day it may be sunny, the next may be rainy, and after that it may be cloudy. This is normal in summer as well as in winter. These are the main types of temperate climate:

• A maritime climate is generally for places near the sea. That includes London, Dublin, Melbourne and Auckland. Most places do not have a rainy season and a dry season. Prevailing winds in the temperate zone are from the west. The western edge of temperate continents usually get this maritime climate. Examples are Western Europe, and western North America at latitudes between 40° and 60° north (65°N in Europe).
• Some parts of the temperate zone have a Mediterranean climate, which have a dry summer – for example Madrid, and Adelaide.
• Some parts of the temperate zone, especially in the northern part of the continental climate, have severe winters – for example Moscow and Minnesota – this is called a hemiboreal climate.
• Some places in the temperate zone have hot summers and cold winters, for example Chicago, Budapest and Almaty.

Picture Credit : Google

            A region’s climate is the general pattern of weather that it experiences over a long period of time. Climate depends on a number of factors. The position of the area on the Earth’s surface, and its height above sea level are two factors. Warmth carried around the world by ocean currents affects the climate on land, and those areas far from the sea will have a different climate from those on the coast. There are eight main types of climate, but there are variations to be found within them.

           Climate is the average weather conditions in a place over a long period of time—30 years or more. And as you probably already know, there are lots of different types of climates on Earth.

            For example, hot regions are normally closest to the equator. The climate is hotter there because the Sun’s light is most directly overhead at the equator. And the North and South Poles are cold because the Sun’s light and heat are least direct there.

            Using this information, in the late 1800s and early 1900s a German climate scientist named Wladimir Koppen divided the world’s climates into categories. His categories were based on the temperature, the amount of precipitation, and the times of year when precipitation occurs. The categories were also influenced by a region’s latitude—the imaginary lines used to measure our Earth from north to south from the equator.

            Today, climate scientists split the Earth into approximately five main types of climates. They are:

A: Tropical. In this hot and humid zone, the average temperatures are greater than 64°F (18°C) year-round and there is more than 59 inches of precipitation each year.

B: Dry. These climate zones are so dry because moisture is rapidly evaporated from the air and there is very little precipitation.

C: Temperate. In this zone, there are typically warm and humid summers with thunderstorms and mild winters.

D. Continental. These regions have warm to cool summers and very cold winters. In the winter, this zone can experience snowstorms, strong winds, and very cold temperatures—sometimes falling below -22°F (-30°C)!

E: Polar. In the polar climate zones, it’s extremely cold. Even in summer, the temperatures here never go higher than 50°F (10°C)!

Picture Credit : Google

            When the Sun is directly overhead at its most northern or southern position, it is called the solstice. The Northern Hemisphere’s summer solstice occurs when the Sun is above the Tropic of Cancer — on 20, 21 or 22 June — and marks the beginning of summer. Its winter solstice (the Southern Hemisphere’s summer solstice) is on 21 or 22 December. The summer solstice is the longest day of the year; the winter equivalent is the shortest.

            Solstice, either of the two moments in the year when the Sun’s apparent path is farthest north or south from Earth’s Equator. The situation is exactly the opposite in the Southern Hemisphere, where the seasons are reversed. At the winter solstice the day is the year’s shortest, and at the summer solstice it is the year’s longest. The term solstice also is used in reference to either of the two points of greatest deviation of the ecliptic (the Sun’s apparent annual path) from the celestial equator.

            At the time of the summer solstice in the Northern Hemisphere, the North Pole is tilted about 23.4° (23°27´) toward the Sun. Because the Sun’s rays are shifted northward by the same amount, the vertical noon rays are directly overhead at the Tropic of Cancer (23°27´ N). Six months later the South Pole is inclined about 23.4° toward the Sun. On this day of the summer solstice in the Southern Hemisphere the Sun’s vertical overhead rays progress to their southernmost position, the Tropic of Capricorn (23°27´ S). Compare equinox. See also season.

Picture Credit : Google

            Many people suffer from the “winter blues”. Feeling tired, run down and a bit sad is a natural response to the long, dark days, cold weather and the effects of colds and flu. A few people experience exaggerated symptoms, which doctors have recognized as a medical condition known as Seasonal Affective Disorder, or SAD. A lack of daylight can cause sufferers of SAD to become very depressed and have problems sleeping and eating.

            Seasonal affective disorder (SAD) is a type of depression that’s related to changes in seasons — SAD begins and ends at about the same times every year. If you’re like most people with SAD, your symptoms start in the fall and continue into the winter months, sapping your energy and making you feel moody. Less often, SAD causes depression in the spring or early summer.

            Treatment for SAD may include light therapy (phototherapy), medications and psychotherapy.

Don’t brush off that yearly feeling as simply a case of the “winter blues” or a seasonal funk that you have to tough out on your own. Take steps to keep your mood and motivation steady throughout the year.

Symptoms

            In most cases, seasonal affective disorder symptoms appear during late fall or early winter and go away during the sunnier days of spring and summer. Less commonly, people with the opposite pattern have symptoms that begin in spring or summer. In either case, symptoms may start out mild and become more severe as the season progresses.

Signs and symptoms of SAD may include:

• Feeling depressed most of the day, nearly every day
• Losing interest in activities you once enjoyed
• Having low energy
• Having problems with sleeping
• Experiencing changes in your appetite or weight
• Feeling sluggish or agitated
• Having difficulty concentrating
• Feeling hopeless, worthless or guilty
• Having frequent thoughts of death or suicide

Fall and winter SAD

Symptoms specific to winter-onset SAD, sometimes called winter depression, may include:

• Oversleeping
• Appetite changes, especially a craving for foods high in carbohydrates
• Weight gain
• Tiredness or low energy

Spring and summer SAD

Symptoms specific to summer-onset seasonal affective disorder, sometimes called summer depression, may include:

• Trouble sleeping (insomnia)
• Poor appetite
• Weight loss
• Agitation or anxiety

Picture Credit : Google

            In the parts of the world that are close to the poles, the way the Earth tilts means that the summer months in those regions are marked by constant daylight. Parts of Scandinavia, for instance, are known as the “land of the midnight Sun”. In mid-winter, these areas experience the opposite — total darkness for 24 hours a day.

            The midnight sun is a natural phenomenon that occurs in the summer months in places north of the Arctic Circle or south of the Antarctic Circle, when the Sun remains visible at the local midnight.

            Around the summer solstice (approximately 21 June in the Northern Hemisphere and 23 December in the Southern Hemisphere), the Sun is visible for the full 24 hours, given fair weather. The number of days per year with potential midnight sun increases the closer towards either pole one goes. Although approximately defined by the polar circles, in practice the midnight sun can be seen as much as 55 miles (90 km) outside the polar circle, and the exact latitudes of the farthest reaches of midnight sun depend on topography and vary slightly year-to-year.

            Because there are no permanent human settlements south of the Antarctic Circle, apart from research stations, the countries and territories whose populations experience the midnight sun are limited to those crossed by the Arctic Circle: the Canadian Yukon, Nunavut, and Northwest Territories; the nations of Iceland, Finland, Norway, Sweden, Denmark (Greenland), Russia; and the State of Alaska in the United States. A quarter of Finland’s territory lies north of the Arctic Circle, and at the country’s northernmost point the sun does not set at all for 60 days during summer. In Svalbard, Norway, the northernmost inhabited region of Europe, there is no sunset from approximately 19 April to 23 August. The extreme sites are the poles, where the sun can be continuously visible for half the year. The North Pole has midnight sun for 6 months from late March to late September.

            The opposite phenomenon, polar night, occurs in winter, when the Sun stays below the horizon throughout the day.

            Since the axial tilt of the Earth is considerable (approximately 23 degrees 27 minutes), the Sun does not set at high latitudes in local summer. The Sun remains continuously visible for one day during the summer solstice at the polar circle, for several weeks only 100 km (62 mi) closer to the pole, and for six months at the pole. At extreme latitudes, the midnight sun is usually referred to as polar day.

            At the poles themselves, the Sun rises and sets only once each year on the equinox. During the six months that the Sun is above the horizon, it spends the days continuously moving in circles around the observer, gradually spiralling higher and reaching its highest circuit of the sky at the summer solstice.

            Because of atmospheric refraction, and also because the Sun is a disc rather than a point, the midnight sun may be experienced at latitudes slightly south of the Arctic Circle or north of the Antarctic Circle, though not exceeding one degree (depending on local conditions). For example, Iceland is known for its midnight sun, even though most of it (Grímsey is the exception) is slightly south of the Arctic Circle. For the same reasons, the period of sunlight at the poles is slightly longer than six months. Even the northern extremities of Scotland (and places at similar latitudes, such as St. Petersburg) experience twilight throughout the night in the northern sky at around the summer solstice.

            Observers at heights appreciably above sea level can experience extended periods of midnight sun as a result of the “dip” of the horizon viewed from altitude.

Picture Credit : Google