25 years ago, in late August 1998, something interesting happened in Canadian atmospheric science:
A large Canadian scientific stratospheric balloon was launched from Saskatchewan on August 24, 1998. It was intended to have a flight lasting about 24 hours and stay relatively near its launch site. Instead, it went on an unexpected adventure across an ocean and into several countries’ airspaces. Fighter jets were tasked with taking it down. World news organizations covered the updates.
This is the MANTRA 1998 story.
What is a stratospheric balloon?
It’s a very large balloon, typically filled with Helium, that carries a scientific payload (instruments and support systems) weighing up to ~a tonne (1000 kg) into the stratosphere (15 to ~50 km altitude).
They can be as tall as the CN Tower observation deck!
Stratospheric balloons like MANTRA are much larger & complex than common weather balloons, which also are typically Helium filled and carry instruments into the stratosphere. But those payloads are very small and light: ~250 g. That makes MANTRA’s scientific sensor payload (~300 kg) about 1200 times larger. Some sensor payloads are even larger.
Eureka Weather Station balloon launch preparations.
MANTRA was 150 meters high or about the size of a 25-story building when at stratospheric altitudes.
Photo showing MANTRA98 being prepared for launch, overnight August 23/24, 1998.
The MANTRA balloon included a variety of instruments designed to measure ozone chemistry-related atmospheric gases. There were also systems for power and control of the balloon. Its gondola was 2 m × 2 m × 2 m in size, constructed using a light aluminum frame. The total payload weighed 630 kg.
Schematic of MANTRA gondola from Strong et al. 2005.
More specifically, MANTRA instruments sought to acquire:
Vertical profiles of: NO2, HNO3, HCl, CFC-11, CFC-12, N2O, CH4, temperature, and aerosol backscatter from balloon instruments.
Total columns of: O3, NO2, SO2, aerosol optical depth by ground-based spectrometers.
Two major aspects of seasonal change are weather and the “length of the day” — i.e., the number of sunlight hours.
The magnitude of this change depends on latitude. Near the equator, the amount of sunlight stays relatively constant. In mid-latitudes there’s quite a noticeable change in the length of daytime. In Toronto, for example, the amount of sunlight in a day stretches from 9 hours in the middle of winter to over 15 hours in the middle of summer. In the polar regions the change is even more dramatic. There are times when the sun never sets (“midnight sun”) and times when the sun never rises (“polar night”). The seasonal change in sunlight has profound impacts on the environment, animals and plants, and people.
I wrote an earlier post about sunlight changing over the seasons, motivated by my time doing fieldwork in the Canadian High Arctic. In this post, I wanted to look at the same topic more generally and create an interactive plot for people to explore.
Joseph Mendonca and I watch the sun rise late morning on Feb. 25, 2013 in Eureka, Nunavut (photo credit: Paul Loewen)
This interactive figure illustrates the number of sunlight hours there are at a various Canadian cities and locations.
You can select a location by clicking on the entries in the legend. There are tools in the top-left of the figure to let you zoom in and explore the data.
Why does this happen?
This happens because the Earth’s axis tilts the Polar Regions completely away from the Sun, and into complete darkness in winter, and tilts towards the Sun for part of the summer. During summer in the Arctic, the Sun moves in a circle across the sky once per day, never setting.
Over the course of the year in the Polar Regions, the Earth’s axial tilt creates Polar Night during winter and the Midnight Sun during summer. Credit: https://en.wikipedia.org/wiki/Arctic_Circle#Midnight_sun_and_polar_night
Here’s a fun trivia question to ask friends and family: on what day of the year do all places on the planet have the same length of a day? The length of a day is equal everywhere on the planet two days a year.** These days are called the equinoxes. You can see these days by plotting multiple sites and looking where they intersect. I’ve also added an option on the plot to show them as lines on the plot.
Also noticeable on the plot is that the length of the day is maximum mid-summer and minimum in winter. These dates are the solstices, when the tilt of the Earth is either fully towards or away from the Sun.
I hope this puts the changing daylight hours you experience in a new light.
Enjoy!
Sunset over Mississauga, viewed from downtown Toronto
** atmospheric refraction can slightly impact the equality of the daytime/nighttime on the day of the equinoxes.
Acknowledgements:
Thank you to the python community, which has developed and maintained the packages I use to make nice plots, i.e. bokeh, numpy, pandas, ephem, and pytz.
Several of my photos have been featured in the Blackwood Gallery’s newly-published broadsheet, Society for the Diffusion of Useful Knowledge (SDUK) Volume 4: Grafting. A PDF copy of the full publication is online here.
The vision of the SDUK project is:
“To productively collide with the present crisis, ideas cannot be constrained by disciplines. An ecology of knowledge based on the relationship and antagonism of “useful” ideas will be composed and circulated through THESOCIETY FOR THE DIFFUSION OF USEFUL KNOWLEDGE (SDUK). The name of this innovative platform is borrowed from a non-profit society founded in London in 1826, focused on… spreading important world knowledge to anyone seeking to self-educate…”
There are some interesting pieces in the issue. My favourite is by Skye Moret, who presents the colour pallet of Antarctica in a visually stunning and fascinating way. A version of her piece is also on her website here.
The printed publication has been distributed at libraries, bookstores and communities centres in the GTHA and across Canada.
Days are getting longer everywhere in the northern hemisphere this time of year.* In the Arctic, the change in sunlight is particularly dramatic.
A few days ago, sunlight returned to Eureka, Nunavut for the first time since October, marking the end of Polar Night.
Joseph Mendonca and I watch the sun rise late morning on Feb. 25, 2013 in Eureka, Nunavut (photo credit: Paul Loewen)
During the transition between Polar Night and the continuous daylight of summer (“Midnight Sun”), a team of Canadian scientists take measurements of the changing atmosphere above Eureka at the Polar Environment Atmospheric Research Laboratory (PEARL) using specialized instruments.
(I was part of that team until recently. Daily updates from the campaign are posted here.)
Installing atmospheric monitoring instruments on the roof of the PEARL Ridge Lab during the 2014 sunrise campaign.
The return of sunlight after a long absence generates significant changes in the atmosphere. Ozone depletion chemistry, for example, is acutely impacted. A former colleague of mine wrote a blog about it here.
I made a few plots to show how big the sunlight shift is in high Arctic, with a few other locations included for comparison. This change in light has profound impacts on the environment, animals and plants, and people.
In Toronto (43°N), the amount of sunlight in a day stretches from 9 hours in mid-winter to over 15 hours in mid-June.
Sunlight hours each day in Toronto
The size of the seasonal change in sunlight depends on latitude. If you go south from Toronto, there’s less change over the course of the year. In the Caribbean, for example, a hypothetical province called Saskatchewarm would have relatively stable sunlight throughout the year:
Sunlight hours each day in the hypothetical “Saskatchewarm” in the Caribbean
Yellowknife, Northwest Territories (63°N) is much farther north than most Canadians venture. I recommend visiting it: there is fantastic art and culture to see. And it’s a good place to see Aurora Borealis. Since it’s 2000 km north of Toronto, it experiences a much larger swing in seasonal sunlight. It’s quite a big change: days in Yellowknife range from 5 hours in mid-winter to 20 hours mid-summer.
Sunlight hours each day in Yellowknife (2000 km north of Toronto)
From the North/South point of view, Yellowknife is roughly equal distances between the southernmost and the northernmost parts of Canada. The Canadian Arctic is a vast region. Let’s head another 2000 km north to look at daylight in the extreme case of Eureka.
Arctic landscape – Ellesmere Island
Eureka is a high Arctic research site at 80°N, on Ellesmere Island. The daylight hours plot is oddly shaped compared to southern sites. For most of the year, daylight doesn’t change day-to-day: it’s either totally dark or light.
Sunlight hours each day in Eureka
The transition between total darkness and never ending day takes only 2 months. This morning, the Eureka sunrise occurred at a rather convenient 10 am. It’ll set mid-afternoon. In a week, sunrise will occur more than an hour earlier, and sunset an hour later.
Rapid change in high Arctic sunlight
Sunrise at Eureka, Nunavut from the road to PEARL
Why does this happen?
This happens because the Earth’s axis tilts the Polar Regions completely away from the Sun, and into complete darkness in winter, and tilts towards the Sun for part of the summer. During summer in the Arctic, the Sun moves in a circle across the sky once per day, never setting.
Over the course of the year in the Polar Regions, the Earth’s axial tilt creates Polar Night during winter and the Midnight Sun during summer. Credit: https://en.wikipedia.org/wiki/Arctic_Circle#Midnight_sun_and_polar_night
If we combine the plots for all three sites, a couple of interesting dates pop out:
Sunlight at Eureka, Yellowknife, and Toronto
Here’s a fun trivia question to ask friends and family: on what day of the year do all places on the planet have the same length of a day?
The length of a day is equal everywhere on the planet two days a year.** These are the intersection points between the sunlight hours at Toronto, Yellowknife, and Eureka. If I added other cities, they would also intersect at those points. These special dates, March 20 and September 23, are when the Earth is facing the sun upright with no relative tilt. Day and night are both 12-hours long. (Another trivia question could be on what day are day and night the same length.) They’re called the equinoxes.
Also noticeable on the plot is that the length of the day is maximum mid-summer (June 21) and minimum in winter (December 21). These dates are the solstices, when the tilt of the Earth is either fully towards or away from the Sun.
I hope this puts the changing daylight hours you experience in a new light.
Enjoy!
Sunset over Mississauga, viewed from downtown Toronto
** atmospheric refraction can slightly impact the equality of the daytime/nighttime on the day of the equinoxes.
Acknowledgements:
Thank you to the python community, which has developed and maintained the packages I use to make nice plots, i.e. matplotlib, numpy, pandas, and calculate the sunrise/sunset, i.e. ephem, pytz.
