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What is Spring?

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Investigate the signs of Spring with Greenwave!

The aim of the Greenwave project is to observe the onset of spring as it arrives in Ireland and shows its presence throughout the island. But what exactly is the spring? This article will explore what happens during the season and why it occurs at all.

"Spring is the season of the year that comes between winter and summer."

Before we learn more about what happens during the spring you might wonder why we have seasons at all. Seasons are caused by the fact that the axis that the earth turns on is not quite straight. This means that as the year passes the North Pole is tilted somewhat towards the sun for half the year and slightly away from the sun for the other half.

During the months that the North Pole is tilted towards the sun the days in the northern hemisphere get longer and the land receives more of the suns rays. The sun also shines more directly onto the earth and provides increased amounts of energy. As a result the average temperature rises during this period, giving us the spring and summer seasons. When the earth begins to tilt away from the sun the days begin to shorten and cool down in the northern hemisphere and we move into the autumn and winter. Can you guess what is happening in the southern hemisphere at this time? That's right, the seasons are reversed and the spring will be getting started in the southern half of the planet while the autumn is developing in the north.

In the northern Hemisphere, the spring commences on the vernal equinox (March 20th or 21st) and ends on the summer solstice which occurs on the 21st of June. An equinox is a day in which the length of the day and the night are of equal duration all around the planet. The summer solstice is the day when the sun reaches its most northerly declination and hence this is the day of the year where the sun is in the sky for longest in the northern half of the planet.

So, the spring occurs officially between mid March and mid June, however, as you know from the species we observe during the Greenwave project, the indications that spring has sprung can be seen well before the middle of March.

"Did you know - due to the tilt in earth's axis while it is spring time in the Northern Hemisphere it will be autumn in the south."

So what happens in Ireland during the spring season? As we have learned, during spring the country receives increasing amounts of energy from the sun. This leads to a rise in air, water and ground temperatures which in turn prompts the onset of renewed plant growth after a quiet winter. At the same time, the slowly rising temperature and the increased availability of food leads the animals that eat the newly regenerating plants to start to appear followed soon after by their predators. Animals and insects like the hedgehog, the frog and the ladybird will emerge from their winter hibernation ready to breed and start building up their stores of energy after depleting them during the winter.

The swallow and other migratory animals will also start to appear on our shores, attracted - in the swallow's case - by the large amounts of insects that they can feed on, the mild weather and the long hours of daylight that allow them to gather food to feed their young.