February: Snow and Sun in the Bio­sphere

The Victoria Standard - - Environment - ANNAMARIE HATCHER

February is called ‘Bright sun Time’ (Apik­na­jit) or ‘Snow blin­der month’ in Mi’kmaq. To shine a light on the ‘bright sun char­ac­ter­is­tics’ of February in the Bras d’or Lake Bio­sphere, I con­sulted the so­lar an­gle cal­cu­la­tor made avail­able by the Na­tional Re­search Coun­cil of Canada and the cli­mate nor­mals (av­er­ages) for 1981 to 2010 col­lected by the Me­te­o­ro­log­i­cal Ser­vice of Canada.

In Jan­uary and February you need eye pro­tec­tion when en­joy­ing win­ter sports in the Bio­sphere. Snow blind­ness, caused by ul­tra­vi­o­let light from the sun, is a painful eye con­di­tion which can be de­scribed as a sun-burned eye. In north­ern re­gions, this con­di­tion was tra­di­tion­ally avoided by us­ing pro­tec­tion in the form of snow gog­gles, con­structed of wood or bone with a thin slit.

Be­tween 1981 and 2010, snow has been recorded in all months be­tween Oc­to­ber and May in the Bio­sphere. How­ever, in Oc­to­ber and May the ac­cu­mu­la­tion is min­i­mal. So, for our pur­poses, I will des­ig­nate Novem­ber to April as the ‘snowy months’. Be­sides, it feels bet­ter to say that it snows on 50% of the months of the year rather than 67%!

Bright sun­shine ob­ser­va­tions are made with a glass sphere (Camp­bell­stokes sun­shine recorder) which fo­cuses the sun’s rays on a card to gen­er­ate mea­sure­able burn marks. These mea­sure­ments are not avail­able for Bad­deck, so we will look at bright sun av­er­ages mea­sured in Sydney over the 1981 to 2010 pe­riod. April is the stand­out at 141 hours, twice the num­ber of hours of bright sun­light in De­cem­ber. February is 80% of April’s av­er­age.

Any­one who drives reg­u­larly over Kelly’s moun­tain in the win­ter will tell you that there are dis­tinct mi­cro­cli­mates through­out the Bio­sphere. In the pe­riod of 1981 to 2010, av­er­age recorded snow­fall for the year was 283 cm in Sydney and about 10% higher in Bad­deck at 312 cm. As ex­pected, the best time for ski­ing was prob­a­bly in Jan­uary be­cause the largest amounts of snow fell (81.7 cm in Bad­deck). That may not be the case this year. Al­though the month of February is not usu­ally the time of max­i­mum snow­fall, the amount recorded be­tween 1981 and 2010 is im­pres­sive (66.6 cm in Bad­deck) when com­pared to the amount recorded in some other parts of the prov­ince such as the Hal­i­fax Ci­tadel (35 cm).

How does the snow cover af­fect the amount of sun that is re­flected from the ground and into the eyes? Dur­ing sum­mer, land­scape el­e­ments such as green grass ab­sorb light. How­ever, dur­ing the snowy months, snowflakes scat­ter and re­flect the sun’s rays in­creas­ing the amount of light that is avail­able to en­ter the eye. The ra­tio of light re­flected to the amount of light that falls on a sur­face is called ‘albedo’. This is not to be con­fused with ‘li­bido’ which is an en­tirely dif­fer­ent thing! In­ter­est­ingly, snow ex­hibits a large amount of vari­abil­ity in albedo as a func­tion of the age of the snow sur­face and amount of cloud cover. To see what makes February rate as ‘snow blin­der month’, let’s take a look at how these things change over the snowy months.

Fresh new snow greater than 1 cm in depth has an albedo of about 0.85, mean­ing that it re­flects about 85% of the sun’s rays that hit it and ab­sorbs the rest. The char­ac­ter­is­tics of that snow­pack change as it ages. The del­i­cate crys­talline struc­ture of the snowflakes breaks down, spa­ces be­tween the grains are in­filled with wind-blown par­ti­cles and sur­face melt­ing causes a change from powder to a more gran­u­lar con­sis­tency. Be­cause of these fac­tors, the albedo of a melt­ing snow­pack can change rapidly, up to 9% per day. A fresh fall of greater than 1 cm will re­verse this trend. So, what about the du­ra­tion of snow­fall? Again, Jan­uary tops the list in the Bio­sphere, with snow fall­ing on about 50% of the days of the month. This is about dou­ble the num­ber of snowy Jan­uary days than the Hal­i­fax Ci­tadel. In the Bio­sphere, snow falls on 40% of February days, an im­pres­sive statis­tic!

The re­la­tion­ship be­tween cloud cover and snow­pack albedo is very sur­pris­ing and not what you might pre­dict. When skies are clear, the sun’s rays reach the snow sur­face di­rectly. When the rays reach the snow sur­face, the sur­face rough­ness casts shad­ows and sep­a­rate sur­face snow grains re­flect a di­rect beam only on one side. There is less of a shadow cast when skies are over­cast and dif­fuse light from the sun reaches sur­face snow crys­tals on all sides from all di­rec­tions. Thus, the albedo of a snow­pack is higher un­der over­cast skies. Dur­ing the snowy months it is very cloudy be­tween 60 and 70% of the time ac­cord­ing to the cli­mate nor­mal of Sydney (no mea­sure­ments are avail­able for Bad­deck). There is less cloud in Jan­uary and February than Novem­ber and De­cem­ber. The thin­ner clouds en­hance Ul­tra­vi­o­let lev­els be­cause of scat­ter­ing. Re­mem­ber that when you em­bark on a ski trip in lightly over­cast con­di­tions. Take your snow gog­gles!

So, where does that leave us in our ex­plo­ration of February as ‘Bright sun time’ in the Bras d’or Lake Bio­sphere? Con­di­tions are right in February for ‘Bright Sun Time’ but that de­scrip­tor may also ap­ply to Jan­uary or March in some years. This anal­y­sis dealt with cli­mate nor­mals, or av­er­ages over long time pe­ri­ods. Ev­ery year is dif­fer­ent. Re­mem­ber Jan­uary, 2015? The Bio­sphere looked a lot whiter than it did in Jan­uary, 2017. The di­ver­sity of weather pat­terns from year to year and the glob­ally chang­ing cli­mate may mean that ‘bright sun time’ will oc­cur in De­cem­ber or March for the cli­mate nor­mal anal­y­sis of 2017 to 2046. Maybe we won’t have a ‘bright sun time’ or as much snow in 2046 and the Bio­sphere res­i­dents who nor­mally leave for Florida dur­ing the snowy months will just stay put!

Dr. Annamarie Hatcher is an ad­junct pro­fes­sor in Unama’ki Col­lege, Cape Bre­ton Univer­sity, and a board mem­ber of the Bras d’or Lake Bio­sphere Re­serve As­so­ci­a­tion. For more in­for­ma­tion about the Bras d’or Lake Bio­sphere Re­serve As­so­ci­a­tion, please visit http:// blbra.ca/.

Friends of the au­thor, Sam and Gra­ham, are seen ski­ing Ben Eoin while wear­ing eye pro­tec­tion. Photo by Annamarie Hatcher.

Newspapers in English

Newspapers from Canada

© PressReader. All rights reserved.