Meteorological Phenomena: Crepuscular Rays

Whilst they may not know the name, most cloudspotters have probably noticed a beautiful sighting called Crepuscular rays. Here's your theme for the next “Reader's Meteo Collage” so keep your cameras photo ready so you can capture this amazing yet not-as-elusive phenom. Crepuscular rays occur when objects such as mountain peaks or clouds partially shadow the sun's rays. The name crepuscular means “relating to twilight” and these rays are observed at sunrise and sunset. The hours around dusk and dawn are called the crepuscular hours (relating to twilight) and have given this light phenomenon its name. Dusk and dawn is the time of the rays most frequent occurrences when the contrast between light and dark is the most obvious. However, they can be seen at any time of the day, depending on conditions. This visual effect is created when the sunlight is alternately scattered with dust, rain, snow, or mist, and obscured by something which casts a shadow. Classically, crepuscular rays appear as shafts of light coming from a cloud, with the sunlight piercing the cloud in thin places while the cloud shadows other parts, creating an illusion of pillars of light.

Dok mozda nisu upoznati da postoji naziv za ono sto su vidjeli, vecina osmatraca (profesionalnih, amaterskih ili entuzijasta) su zasigurno nekada primjetili krasan prizor koji se naziva Vecernje/sumracne/sutonske zrake. I ovo neka bude tema za slijedeci “Meteo kolaz citateljica” – neka vase kamerice budu spremne da zabiljeze ovaj fascinantni no ne i rijedak fenomen. Sumracne zrake se pojavljuju kada objekti poput npr.planinskih vrhova ili oblaka djelimicno bacaju sjenu na sunceve zrake. Naziv ovih zraka je doslovno izveden iz sutona/sumraka/predvecerja posto je tada najveca sansa da budu primjecene iako se javljaju i ujutro, u zoru. Ti sati su pogodni  za ovu pojavu posto je tada kontrast izmedju svjetla i tame najveci. Ipak, nekada se mogu osmotriti i tokom dana (ovisno od uvjeta) a licno sam ih uslikala par puta otprilike oko podneva. Vizuelni efekat karatkeristican za ovu pojavu se kreira kada je sunceva svjetlost neravnomjerno rastrkana zbog prasine, kise, snijega ili sumaglice u zraku te istovremeno i zaklonjena objektom koji baca sjenu. Klasican izgled sutonskih zraka su stubovi svjetla koji dolaze od oblaka tako sto sunceva svjetlost probija oblak na pojedinim mjestima dok su drugi dijelovi u sjeni, stvarajuci iluziju svjetlosnih stubova.

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Crepuscular rays appear to diverge outward from the setting sun but they actually do not radiate from one point but are near parallel. Similar to railway tracks disappearing into the distance, they seem to diverge because of the distance and perspective they are viewed at. Crepuscular rays are often red or yellow in appearance because blue light from the sun is selectively scattered out of the beam by air molecules. Crepuscular rays are colloquially known as a Jacob's Ladder, Gateways to Heaven, Buddha's Fingers, Jesus Beams, God's Rays, sunbeams, cloud breaks and many other names. It is not surprising that many of the names have religious connotations as crepuscular rays associate people of a heavenly light from the skies. Much more rare are Anti-crepuscular rays. Light rays scattered by dust and haze occasionally appear to converge toward the “antisolar” point, (the location on the horizon opposite the point where the sun is setting). These rays, called anti-crepuscular rays, originate at the sun, cross over the sky to the opposite horizon, and appear to converge toward the antisolar point because of perspective.

Vecernje/sumracne/sutonske zrake djeluju kao da dolaze iz pravca sunca, kriveci se ka ivicama prema vani no one ustvari leze paralelno jedna drugoj samo sto zbog pozicije sa koje ih promatramo i udaljenosti djeluju kao da se krive. Sutonske zrake cesto poprimaju crvenu ili zutu boju iz razloga sto se plavo svjetlo iz pravca sunca selektivno rasprsuje iz snopa zbog molekula zraka. Sutonske zrake su u narodu poznate i kao Jakobove stepenice, Stubiste do raja, Budini prsti, Isusove zrake, jednostavne sunceve zrake, lomljenje oblaka itd. Nije iznenadjujuce sto mnogi nazivi imaju religijsku konotaciju jer je jasno zasto neke ljude sutonske zrake podsjecaju na nebesko svjetlo – okrivite filmove za to ali i mitove. Dosta rijedja pojava od navedene su Protiv-sutonske/sumracne/vecernje zrake. One nastaju kada se sunceve zrake rastrkane iz istih razloga (no najcesce suhom sumaglicom) pocnu spajati u antisolarnoj tacki (tacka na horizontu suprotna poziciji sunca u datom trenutku). Te neobicne zrake zapocinju od sunca, prelaze preko neba na suprotnu stranu horizonta i spajaju se u toj antisolarnoj tacki. Te zrake nema potrebe da trazimo, zadrzati cemo se na klasicnim sutonskim zrakama. Imati cemo otprilike sedam dana da sakupimo fotke za kolaz kada ce biti objavljen na blogu. Jako se radujem novom zajednickom projektu sa vama!

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