When Really is the First Day of Spring? (Credit: National Centers for Environmental Information, NASA, SPACE)
DISCUSSION: As we transition into spring in the Northern Hemisphere, it is important to understand the difference between astronomical and meteorological seasons. The first day of spring falls on March 20th for the astronomical season, while for the meteorological season it falls almost three weeks earlier on March 1st. So which one should we follow?
The astronomical season of spring falls between March 20th to June 21st and refers to the position of the Earth’s orbit in relation to the sun. The Earth’s axis is an imaginary pole going through the center of Earth from the North Pole to the South Pole. Each day the Earth completes a full spin around its axis creating days and nights. But since the axis is not straight, this causes the Earth to have seasons. As the Earth travels around the sun, the axis always stays in the same position which allows different parts of the Earth to receive direct rays from the sun at different times of the year. In March and September, the sun shines equally on the Southern and Northern hemispheres, which marks the beginning of fall and spring. In the Southern Hemisphere, the seasons are reversed but fall on the same days as the Northern Hemisphere. Leap years cause the exact date to vary. Furthermore, this also makes the length of the seasons to range from 89 to 93 days, which makes comparing seasonal statistics year to year extremely difficult for climatologists.
The spring season falls between March 1st and May 31st for the meteorological seasons. Meteorologist split the four seasons into three months each based off of annual temperature cycles and the calendar. Winter is known to be the coldest months: December, January, and February; while summer is known to be the warmest months: June, July, and August. Fall and spring are known as transition seasons, March, April, and May get increasingly warmer, while September, October, and November get increasingly colder. Since these seasons follow the calendar, the days per season are more consistent, ranging from 90 to 92 days. This allows climatologists to easily calculate seasonal statistics for each month and season, which is helpful for commerce and agriculture.
Even though these aren’t the only two ways of categorizing the seasons, these are the most common. The National Weather Service prefers to follow the meteorological seasons as it is more practical to handle whole months of data rather than fractions of months. Before meteorological seasons were put into use, it was tedious for the NWS to make exact seasonal comparisons since the first day of each season had varying dates. Even though the NWS follows the meteorological seasons, not everyone does. For example, schools don’t let kids out for summer on the first day of June, but instead near 21st. So while there is no wrong season to follow, there are advantages and disadvantages to them.
(Citied: National Centers for Environmental Information, NASA, SPACE)
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© 2018 Weather Forecaster Allison Finch