Empire of the Sun

Why does it not rain in Israel in the summer? How come it's now winter in Argentina? Why is August the hottest month of the year in Israel, if the days are getting shorter? And how is Hanukkah related to the sun? Forever following the sun

Written by: Ariel Keres, young Galileo
August is the hottest month of the year in Israel, on average. Those who do not enjoy the heat of summer so much and are already waiting for the return of winter, like me, do not particularly like the hot month of August. Despite the sea, the great vacation and the delicious watermelons, the whole country is completely dried out, and the sun is fiercely beating down on our heads. But as strange as it sounds, in August the days are already starting to get shorter: on August 21, daylight hours in Israel are more than an hour shorter than on the longest day of the year - June 21! So, it makes sense to think that June is the hottest month of the year, because it has "the most" sun, right? The facts show otherwise.
Besides the heat, the Israeli summer is also characterized by an unusual feature: it does not rain at all. Maybe it seems natural to us, but in most countries of the world, even in some of the desert countries, it rains even in the summer, that is, in the hot season. Not with us. If you continue reading, you will discover that the way the sun affects our atmosphere and weather is much more complex than the length of daylight hours in the summer or the temperature values ​​in August.

The setting of the sunrise

From the beginning of mankind, man understood that the sun is the source of life on earth. It gives light and heat, allows the plants to thrive and the water cycle to take place. Many ancient peoples worshiped the sun and considered it a god - and what's the wonder? How can one explain a mysterious ball that hangs in the sky and spreads light and heat without limit? In Egyptian mythology the sun god was called Re, in Greek mythology Helios, among the Celts who lived in Western Europe his name was Virotutis, and in Mesopotamian mythology: Shamash. Aztecs, who lived in and around South America, offered human sacrifices to the sun god because they believed that the sun loses blood every sunrise, and in order for it not to disappear, blood must be returned to it - from the veins of the unfortunate victims.
Many holidays in the various cultures are still connected to the cycle of the sun in the sky and the longest and shortest days of the year, and especially to the winter solstice. With the shortening of the daylight hours during the winter, people feared that the sun would disappear, and celebrated festivals of light designed to revive the sun and return it to the sky soon. Our holiday of light (Hanukkah) and the Christian holiday of light (Christmas) fall on the shortest days of the year. The celebrations are supposed to "convince" the sun to return to the sky as soon as the holidays are over.
The name of our sun is Sol. Despite its enormous size, it is considered a fairly normal star that is closer to the edge of the Milky Way galaxy than to its center, and its distance from Earth is about 149 million kilometers. Man aspired to understand the essence of the sun, but throughout history he had very few tools to do so, other than observations and common sense.
The ancient Greeks were a very practical and inquisitive people. There were among them who understood that the Earth revolves around the sun - and not the other way around, and even understood that the sun has a decisive influence on the weather, but they did not have scientific tools to measure the atmosphere and generate data. The great Greek philosopher and naturalist Aristotle believed that the world consists of four elements - air, water, fire and earth - and that under the influence of the sun they can change from one element to another (for example, water evaporates in heat and becomes "air"). Aristotle's ideas lasted about 1,900 years, but many of them were completely wrong. It was only during the Renaissance in Europe, about 500 years ago, that the first scientists began to challenge Aristotle's concepts and to measure and re-examine weather phenomena - temperatures, humidity, air pressure, clouds, the water cycle on Earth and how the sun affects all of these.
The great scientist Galileo Galilei, after whom the month you hold in your hand is named, invented the first thermometer in 1606. Later, Galileo insisted on asserting that the Earth revolves around the Sun, and not the other way around. As you may remember, the ancient Greeks already claimed this, but the Renaissance sages only started thinking about this revolutionary idea after the Polish astronomer Nicolaus Copernicus published it in a book in 1543.

Galileo supported Copernicus' idea and realized that it had enormous implications for the understanding of nature. But Galileo had to confront the Catholic Church and its executive arm - the Inquisition, who did not see his theories favorably. The Inquisition investigated Galileo, he was tried and sentenced to house arrest for the rest of his life. The religious authorities pressured him to retract his "dangerous ideas" - which removed the earth from its place at the center of the universe and replaced it with the sun.

Oblique heating

Today we know that Galileo was right, but why is the fact that the Earth revolves around the Sun so important? Because the amount of radiation that reaches us throughout the year depends on this coffee, and the changes in the intensity of the radiation allow for the change of seasons and weather phenomena.
Since the imaginary axis on which the Earth rotates around itself is inclined at a rate of about 23.5 degrees with respect to the plane of its orbit around the Sun (imagine a spinning top that continues to rotate even when it is slightly tilted on its side relative to the floor), the northern half of the Earth faces the Sun in the months of June to August. This is why we see that the sun is really high in the sky at noon, and therefore the northern half of the globe receives very strong radiation, and we say that now is a hot summer. The Earth then continues its journey around the Sun.
Six months later, in the months of December to February, it is precisely the southern part of the globe that faces the sun, and the people living in Australia and Argentina say that it is summer for them. Our part, the north, faces the opposite direction, receives less radiation and cools down. The sun is lower at noon, the daylight hours are shorter, and we say that we have winter.

The sun and the weather in Israel

Now we will return to the questions we asked at the beginning of the article: Why is it hotter in Israel in August than in June, even though the daylight hours are shorter? And why doesn't it rain here at all in the summer?
The answer to the first question is that on the longest day of the year, the sea and the deserts around us are still relatively "cold" - the sun has only begun to warm them. And despite the slow shortening of daylight hours in July and August, it will take a long time for the sun to warm the sea and the land well. In June, for example, the sea temperature is 26-25 degrees, and in August - 31-30 degrees, and this greatly affects the weather.
And the answer to the second question? The land heats up faster than the sea, so around the beginning of the second decade of June (around 12-10 of the month) summer weather takes over our region, and it only gets hotter until the end of August.
Broome above us is dominated by the subtropical plateau (Rome ridge) in the summer, and this does not allow the depressions carrying rain to reach us. In the summer the deserts are hot and the plateau spreads up to around the 40th latitude, that is, across almost the entire area of ​​the Mediterranean Sea. In this area, air from the sky sinks down, and it suppresses the development of cloudiness. Apart from that, the elevation causes an inversion (see below), and this does not allow rain clouds to develop, even though the lower part of the atmosphere is dominated by the Persian trough, a system of low pressure associated with the monsoon depression that sends us a spur from the Indian Ocean.
Only after the end of August, deep into September, does the sun's radiation weaken sufficiently, and the daylight hours shorten enough for the air to cool a little and the level that dominates our region to weaken. During this period, the plateau begins to retreat south from the Mediterranean region and slowly turns the area to cold, rain-bearing depressions that come from Europe. However, real rains usually start in Israel only in the month of November, and therefore it can be said that we have a period without precipitation almost from May to October - about five to six months a year!

Some meteorology terms

• Atmosphere: the envelope of gases that surrounds the entire earth and is made of a mixture of gases called air. Most weather phenomena occur in the lower ten kilometers of the atmosphere.
  Air pressure: the force exerted by the weight of the air on a unit area. When the air pressure is high (in Israel, for example, 1,020 millibars) they say there is a barometric level and the chance of rain is small; When the air pressure is low (eg 1,008 millibars) it is said that there is a barometric depression with a chance of rain.
• Barometric depression: an area where the air pressure is low compared to the area surrounding it. A barometric depression usually brings rains and even storms.
• Barometric level: an area where the air pressure is higher relative to the area surrounding it. A barometric level is characterized by stable weather, meaning no precipitation or rain clouds.
• Inversion: a layer of air in which the temperature increases with height (and does not decrease "as expected"). This layer prevents air flow through it upwards.

The article appeared in the August issue of Young Galileo – Monthly for curious children

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