This article was originally published on March 30, 2021.
“April showers bring Mayflowers,” or so we were told. Perhaps that’s why each year in the northern hemisphere, the onset of spring brings predictable months of drizzle.
However, it is important to note that spring does not occur at the same time everywhere in the world. Seasonal changes result from the Earth’s rotation around the sun, so the timing of a the given season depends on the hemisphere you are in. In the northern hemisphere, each season lasts about three months, with spring running from March 1 to May 31. The southern hemisphere experiences the opposite seasons, with spring falling from September 1 to November 30.
Overall, the Northern Hemisphere receives more precipitation than its southern counterpart. But what exactly causes spring rains in regions north of the equator?
Spring rain: a transition to summer
Whether or not an area is particularly rainy depends on where you live: Factors such as latitude, altitude, prevailing winds and the influence of topography precipitation. This blend of ingredients positions the northern hemisphere to receive rain in the spring, especially in the USA.
It turns out that the mystery behind seasonal precipitation — in this case, rain in the spring — is actually relatively simple. Clouds above us form from water vapor that has evaporated from the Earth’s surface. During the spring transition from cooler to warmer temperatures, the air around us warms up. Cool, dry winter air combines with the incoming hot, humid summer air. The mixture of temperatures causes this air to rise and the moisture escapes in the form of rain.
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This leads to a particularly wet spring in the northern hemisphere due to a combination of ideal temperature conditions, proximity to mountain ranges and prevailing winds.
And when summer finally approachesspring showers turn to occasional precipitation as temperatures rise.
Spring in the Southern Hemisphere
While it’s raining in the southern hemisphere during their springshowers do not occur everywhere.
According to Trenberth, the configuration of the continents in relation to the ocean is rather different south of the equator: the continents are subtropical and the main storm tracks are at higher latitudes than in the northern hemisphere, which means that areas such as New Zealand, Tasmania and southern Australia, southern Africa and southern Chile and Argentina experience the most spring storms.
April showers bring tornadoes and thunderstorms?
Kevin Trenbergh, a climatologist who leads the climate analysis section at the National Center for Atmospheric Research (NCAR)explains that spring brings many thunderstorms and tornadoes.
In the United States, storms move from the Pacific to the eastern region, while picking up a lot of moisture from the Gulf of Mexico. This can often lead to huge thunderstorms and tornado outbreaks.
Opposing climate patterns in the Pacific Ocean known as El Niño and La Niña can also impact weather patterns around the world. El Niño occurs when surface waters are warmer than usual around the Pacific equator. On the other hand, Trenberth describes La Niña as when conditions are colder than normal in the tropical Pacific but warmer near Indonesia. In fact, this year’s forecast calls for a stronger-than-usual tornado season due to the La Niña pattern, he says.
A Future of Altered Seasons: More Spring Rain?
Global warming induced by climate change has caused a change of season around the world. With shorter winters and relatively earlier springs, rising temperatures are also disrupting weather patterns: as the world warms, more water evaporates, leading to greater humidity in the atmosphere above. over the oceans.
This triggers more intense rains and can trigger more storms and increase the risk of spring flooding. Conversely, milder months may bring less rain in the future – any depends on where you live.