Meteorology: Research Trivia

Whether it is cloudy or not, tells us whether the air is rising or not. Warm air is less dense than the same amount of cold air. As air rises, it expands adiabatically (without transfer of heat from its surroundings), so it cools. Colder air can absorb lower concentrations of water vapor than warm air, so the moisture forms clouds. Therefore, cloudy skies can be associated with rising air, and clear skies are often associated with descending air.

What causes wind?

Horizontally moving air is called wind, whereas vertically moving air are called air currents. 1st of all, gases will move horizontally or vertically from regions of high atmospheric pressure to low atmospheric pressure. Furthermore, expansion of gases causes cooling and compression causes warming. A mass of warm air tends to move vertically to higher altitudes (where the pressure is lower, and in doing so expands adiabatically, and becomes cooler). And then, cold masses of air at higher altitudes does the opposite, sinking and becoming warmer (both happen at a rate of about 10 Celsius per 1000 meter).

Wind occurs because of differences in air pressure. If not for these circulation patterns, the equatorial regions would be unbearably hot and the polar regions intolerably cold.

(Also note that the temperature change of gases when air is compressed is the basis of how refrigerators work.).

Low pressures and high temperatures.

When the temperature is high, the density of the air is lower. So the column of air above you weighs less, so the air pressure drops. If the pressure gets lower than in surrounding areas, the air will rise, clouds will form and the temperature will drop (during the day). But a lot depends on regional effects. When the pressure distribution is such that the wind comes from the continent, the air is dry, which mean less clouds and higher temperatures in summer.

Clouds and temperature.

Clouds make the days cooler and nights warmer, on average.

-Clouds cool off slower, and heats up slower. This makes for higher lows, and lower highs.
-Clouds radiate some sunlight back to space, keeping the ground from getting too hot, and IR radiation back to Earth, so they maintain higher night time temperature. It also depends on the type of cloud: cirrostratus clouds are almost transparent to visible light but not to IR, so they mostly affect night time temperature.
-Humid air has more energy than dry air (the energy required to turn water into vapor). Energy is released when vapor turns again into clouds, this release of energy warms the air, so it is less cold.
-When wind comes in from the ocean, more clouds are created, because of higher water content. In the summer, sea air is cooler than land air, and in winter, sea air is warmer. So for cloudy days in the winters, you likely have warm winds from the seas.

The highest rain:

Cirrus clouds are composed exclusively of ice crystals and can be found at elevation of 25,000 to 35,000 feet. Thunderstorms, or cumulonimbus clouds, are the high clouds and can elevate to nearly 70,000 feet in the worst unstable environment when air aloft is very cold and surface air is very warm and moist.

Low-altitude clouds cause colder weather, higher-altitude clouds cause warmer weather. Absorbing solar radiation, warms the atmosphere.

Temperature and rain.

An increase of 3 C (5.4 F) correlates with a 10% decrease in rain.

What’s a good way to stop the rainfall?

Increase the temperature of the clouds. For rain to form wet air needs to ascend to a height where due to adiabatic cooling its humidity exceeds 100%.

Why are clouds white?

Due to Mie scattering, the scattering of light by particles with sizes comparable to the wavelength of light. In clouds, water droplets and ice crystals act as scattering particles. Unlike Rayleigh scattering (which causes the sky to be blue by scattering shorter wavelengths more effectively of free electrons), Mie scattering scatters all wavelengths of visible light more or less equally. Therefore, Mie scattering is not as strongly wave-dependent.

So why can't Rayleigh scattering cause clouds to be blue, and Mie scattering cause the sky to be white?

Because the skies are made of nitrogen and oxygen gas, whereas clouds are made of water droplets and ice crystals. Rayleigh scattering causes oxygen and nitrogen to be blue, more than it does to carbon dioxide.

Why is it hot in the center of the Earth?

There are many heat sources. 1 is that during the formation of the Earth, before it had an atmosphere, it was impacted by many rocks. These impacts created heat by friction. Gravity compressed the Earth, which causes an increase in temperature as well (same amount of energy in a smaller space).

As the molten Earth sat, it churned as denser compounds sank and less dense compounds floated. This causes more friction and therefore more heat.

It continues to be heated to this day largely by radioactive decay. As uranium and thorium in the Earth's crust decay, they release energetic particles which bump into other slower particles - more friction, more heat. The heat is trapped deep inside because most of the outer crust is a poor conductor of heat.

Jet streams - and how it increases and decreases airplane speed.

Jet streams are fast moving air which can attain speeds of 200 mph and travel between 10,000 ft to above 40,000 ft in the atmosphere roughly halfway between the North Pole and the equator. The greater the north/south temperature spread through the atmosphere, the stronger the jet stream winds which result. The onset of colder weather increases the north/south temp spread across the mid-latitudes strengthening jet streams in fall, winter and spring.

In the northern hemisphere, jet streams travel east, making airplanes travel faster or slower, for heading east or west. While the jet aircraft generally fly over 500 mph when at cruising altitude, ground speeds have increased to as much as 800 mph. Fast-moving jet streams can cut the time it takes for eastbound flights to make it to their destination - cutting trans-Atlantic flight times by an hour. By the same token, westbound flights fight the headwinds generated by jet streams slowing ground speeds and lengthening flying times. Pilots attempt to minimize these headwinds by adopting flight paths north or south of jet streams.

Jet streams are a product of differing temps through the atmosphere. The greater the temperature spread through the atmosphere, the stronger the winds in the jet streams. Jet streams aid in storm development and the stronger jet streams in the colder months are among the reasons storms grow larger and more intense in the colder months. As the cold season comes on, jet streams grow stronger and the north/south temp spread widens.

Examples:

In fall 2023, passenger aircraft traveling east from the U.S. across the Atlantic have reached up to 778 mph. That’s a little over 200 miles per hour faster than normal cruising speeds. The jet stream is a “core of strong winds around 5 to 7 miles above the Earth’s surface, blowing from west to east,” as the U.K.’s Met Office describes it.

In Feb. 2019, a Virgin Atlantic plane flew at 801 mph from Los Angeles to London, reaching its top speed over Pennsylvania thanks to a 200 mph jet stream – although it slowed down to a mere 710 mph once it hit the ocean. The aircraft, a Boeing 787 Dreamliner, usually has a cruising speed of around 560 mph. Virgin founder Richard Branson described it as flying “faster than any other commercial non-supersonic plane in history.”

Its record was broken the following year (Feb. 2020) by a British Airways Boeing 747-400, at 825 mph (1,328 km/h) on a New York to London flight, slashing the journey time from around 7 hours to just under 5. On that same day, another Virgin Atlantic plane made the same route with a journey time of just 2 minutes more.