Today is the Vernal Equinox, the first day of spring in the northern hemisphere. The new season officially begins at 11:49 PM Eastern Daylight Time.
Our astronomical seasons are a product of the tilt of the Earth’s axis – a 23.5° angle – and the movement of the planet around the sun. During the spring months, the Earth’s axis is tilted neither toward nor away from the sun. This position distributes the sun’s energy equally between the northern and southern hemispheres.
Since the winter solstice in December, the arc of the sun’s apparent daily passage across the sky has been getting higher and daylight hours have been increasing. Today, the sun appears directly overhead at the equator and we have approximately equal hours of day and night. The word “equinox” is derived from Latin and means “equal night”.
As a transitional season, spring is a time when the chill of winter fades away and the warmth of summer gradually returns. The most noticeable increases in average daily temperature, however, usually lag the equinox by a few weeks.
The vernal equinox normally takes place on March 20 or 21, but this year it is arriving a day early. The main reasons for this involve complicated calendar issues related to leap year and daylight savings time. Happy Spring!
Earth’s solstices and equinoxes. Image Credit: NASA
According to Irish folklore, a pot of gold can be found at the end of a rainbow. In reality, however, it is impossible to locate the terminus of this optical phenomenon.
Refraction and reflection inside a raindrop. Credit: Met Office
For a rainbow to form, rain has to be falling in one part of the sky while the sun is out in another. The water droplets in the air act like prisms that refract and reflect the sunlight, revealing the colors of the visible spectrum. Red is refracted the least and is always on the top of a single bow while blue is on the bottom. Since we only see one color from each drop, it takes a countless number to produce a rainbow.
A double rainbow is seen when the light reflects twice inside the raindrops. Since each reflection weakens the intensity of the light, the second bow appears dimmer. The order of the colors is also reversed, with blue on top and red on the bottom.
That said, these colorful arcs are not physical entities that can be approached. No matter how close they appear to be, they are always tantalizingly out of reach. Nevertheless, most people consider seeing one to be a treasure with no gold required.
With a little luck, you can spot a rainbow if you face a moisture source – clearing rain clouds or mist from a waterfall – while the sun is at your back.
Happy Saint Patrick’s Day!
Rainbow and faint second rainbow form after a rainstorm in Bermuda. Credit: Melissa Fleming
Our global temperature continued its upward trend last month. February 2020 marked not only the second warmest February, but also closed out the planet’s second warmest December – February season on record.
According to the State of the Climate Report by NOAA’s National Centers for Environmental Information, Earth’s combined average temperature for February – over both land and sea surfaces – was 55.91°F, which is 2.11°F above the 20th-century average. This February also marked the 422nd consecutive month with a global temperature above its long-term norm. That means the last time any month posted a below average reading was December 1984.
It is also important to note that the ten warmest Februarys have all occured since 1998.
The three-month period of December, January, and February – meteorological winter in the northern hemisphere – was also unusually warm. NOAA reports that Earth’s average temperature for the season was 2.02°F above the 20th century average of 53.8°F. That makes it the second warmest such period on record.
While heat dominated most of the planet this season, some places were particularly warm, including much of Europe and Asia. Here in the contiguous US, it was the sixth warmest winter on record.
Coming on the heels of 2019, Earth’s second warmest year on record, these soaring temperatures are largely attributed to the long-term trend of human-caused climate change.
In fact, February’s temperature marked the highest departure from average for any month during ENSO neutral conditions. That means neither El Niño nor La Niña was present in the Pacific to influence temperatures.
Global temperature records date back to 1880.
The month of March has only just begun, but it felt more like mid-May in New York City on Monday.
In Central Park, the temperature soared to 72°F. While unusually mild, it was not a record breaker for the date. That honor belongs to March 9, 2016 when the high reached 77°F. Nonetheless, this Monday marked the warmest day the Big Apple has seen since last November.
The city’s average high for the date is 47°F.
The primary driver of this unseasonable warmth was a large ridge in the jet stream. Sitting over the eastern part of the US, it allowed warm air from the south to flow further north than it normally would at this time of the year.
Credit: The Weather Gamut
The meteorological winter of December 2019 – February 2020 was unusually mild across most of the contiguous United States.
According to NOAA, the mean temperature for the lower forty-eight states was 36°F. At 3.8°F above average, the season now ranks as the nation’s sixth warmest winter on record.
Regionally, the eastern part of the country was particularly warm. Twenty-four states posted a winter season among their top ten warmest ever recorded.
After a very brief cold snap over the weekend, temperatures in New York City have returned to the above average levels that have dominated most of this winter season.
The temperature in Central Park soared to an unseasonably warm 59°F on Tuesday. While that is 14°F above normal, it was the relatively balmy overnight low that hit record territory. According to the NWS, the temperature only cooled off to 49°F, which tied the maximum minimum record for the date set in 1991.
The normal low temperature in the Big Apple at this time of year is 32°F.
The spring equinox is still a few weeks away, but meteorological winter (December, January, and February) has officially ended and it tied the winter of 1990-91 as the seventh warmest on record in New York City.
The season, with daily highs ranging from 25°F to 69°F, felt like a temperature roller coaster. But in the end, the warmth came out on top. The city’s average temperature for the season, according to the NWS, was 39.2°F. That is an incredible 4.1°F above normal.
In all, sixty-three out of ninety-one days posted above average readings and every month was warmer than its long-term norm. In fact, February 2020 was the city’s fifth warmest February on record.
In terms of snowfall, the city received a paltry 4.8 inches in Central Park, which is a staggering 16.5 inches below average. That makes the winter of 2019-2020 the fourth least snowy winter on record for the Big Apple.
This winter’s pattern of prolonged periods of warmth separated by a few short-lived cold snaps was largely driven by the North Atlantic Oscillation’s positive phase occurring more often and lasting longer than its negative phase.
The city’s warmest winter on record was the 2001-2002 season with an average temperature of 41.5°F. Central Park weather records date back to 1869.
Credit: The Weather Gamut
“March comes in like a lion, and goes out like a lamb”. This old proverb refers to March’s famously changeable weather.
As a month where we transition from winter to spring, March can often start off cold and blustery, but end warm and calm. From the beginning to the end of the month, the average daily temperature increases by 10°F. Exact conditions, of course, vary from year to year.
Although the precise origins of this popular phrase are unknown, many believe it is based on the constellations. At the beginning of March, Leo (lion) is highest in the midnight sky, while Aries (ram) begins to rise toward the end of the month.
Credit: The New Yorker
February 2020 was not only a month of weather whiplash in New York City, but it was also a month for the record books in terms of above-average temperatures and below-average snowfall.
Of its twenty-nine days, twenty-two produced above-average temperatures, including one that was record warm. This unseasonable heat helped drive the city’s mean temperature for the month up to 40.1°F, which is 4.8°F above normal. That means February 2020 tied February 1954 as the fifth warmest February on record in the Big Apple. The top spot belongs to February 2018, when the average temperature for the month was 42°F.
February is usually the city’s snowiest month on the calendar, but this year only a trace of snow (less than 0.1 inches) was measured in Central Park. That makes February 2020 the second least-snowy February on record. Only 1998 produced less snow, with a definitive 0.0 inches. On average, February brings the city 9.2 inches of snow.
Rainfall was also somewhat scarce. Only 2.54 inches was reported. That is 0.55 below normal for the month.
Credit: The Weather Gamut
Winter is the fastest warming season in the United States. In the northeast, it has warmed three times faster than summer. That said, cold snaps – periods of unusually chilly weather – are still happening, but less often.
According to a study by Climate Central, the frequency and duration of these frosty events in the contiguous US have been declining as the overall climate warms. Looking at data from cities across the country, the non-profit news organization found that some places, such as Las Vegas, NV, have lost cold days faster than others. Here in New York City, the average reduction was 5 days since 1970.
Credit: Climate Central