Wonderful Natural Phenomena in Winter冬日美妙的自然現(xiàn)象

HOAR FROST

白霜

One of the first signs of winter is the hoar frost. Deriving its name from an Old English word （hoar， meaning “to appear old”）， this is the thin， feathery coating of ice that often forms on objects during cool nights with clear skies. The clear skies allow the ground to lose heat more quickly than the surrounding air， and the humidity in the atmosphere condenses and freezes into a solid when it makes contact with surfaces. This frost can occur even when the air a few feet above ground is well above freezing， and usually melts within an hour or two of sunrise.

白霜是預示冬天到來的最早預告。白霜的英文名來源于古英語單詞（hoar，意思是“顯得古老”），它是一層薄薄的羽毛狀冰層，通常在晴朗的寒夜凝結(jié)于物體表面。晴天使地面溫度比周圍空氣的溫度下降更快，大氣中的濕氣在與地面接觸時凝結(jié)成固體。即使地面上幾英尺的空氣遠高于冰點，也會形成這種冰霜，并且通常在日出后一兩個小時內(nèi)融化。

GLAZE ICE

雨凇

When falling precipitation hits a surface thats below freezing， it can instantly form whats known as “glaze ice”. a buildup of smooth， clear， and transparent ice. It can be seen coating tree branches and plants following an ice storm.

當雨點落在溫度在冰點以下的表面時，會立即形成所謂的“雨凇”，即光滑、透明的冰層。雨雪過后，可見雨凇覆蓋在樹枝和植物上。

HARD RIME

硬霧淞

As the weather cools， freezing fogs can occur， and when that fog is combined with wind， hard rime can form on windward surfaces. “Rime” literally means “hoar frost，” and while slightly different on a meteorological level， “soft rime” is very similar to a thick hoar frost. Hard rime， on the other hand， is much thicker and harder， and consists of fairly dense pellets of irregular ice crystals glommed together.

隨著天氣變冷，可能會出現(xiàn)凍霧。當凍霧與風結(jié)合時，物體的迎風面會形成硬霧凇。Rime字面意思是“白霜”，“軟霧凇”與厚厚的白霜非常相似，但在氣象層面上略有不同。此外，硬霧凇要更厚更硬，由高密度的不規(guī)則冰晶團聚合在一起形成。

THUNDERSNOW

雷雪

The conditions required to create thundersnow are most common around lakes （it occasionally accompanies lake-effect snow） and coastal areas. In these places， the sun is able to heat the ground and cause relatively warm and humid columns of unstable air to rise up and form turbulent clouds.

在湖泊周圍（偶爾出現(xiàn)湖泊效應降雪）和沿海地區(qū)，最常出現(xiàn)滿足雷雪天氣的氣候條件。在這些地方，陽光讓地面溫度上升，導致相對溫暖潮濕的不穩(wěn)定空氣柱上升，形成湍流云。

But clouds alone dont make thundersnow. Only if the layer of air between the clouds and the ground is warmer than the cloud cover， but still cold enough to create snow， and the wind shear is pushing the warmer air slightly upwards， does thundersnow form.

但光有云層并不能產(chǎn)生雷雪。只有當云層和地面之間的空氣層比云層溫度高，但仍然冷到足以形成降雪，并且風向切變將溫暖的空氣稍微向上推時，才會形成雷雪。

The snow can often muffle the thunderclap， meaning that many instances of thundersnow probably go unnoticed.

雪通常會掩蓋雷聲，這意味著許多時候可能聽不到雷聲。

FIRN

粒雪

When years and years of snowpack accumulate， that buildup is called “firn”. Its much denser than regular snowpack， because of two factors： the partial melting during warmer seasons packs the snow mass closer together; and the new snow falling on top of the ultra-condensed pack pushes the crystals together without melting during the cold season.

當積雪一年又一年堆積起來，就形成了“粒雪”。粒雪比普通積雪的密度大得多，這是兩個因素導致的：在溫暖的季節(jié)，一部分雪融化使積雪堆積得更緊密;在寒冷的季節(jié)，新雪落在密實的積雪頂部，將晶體推到一起而不融化。

Word Study

condense /k?n'dens/ v. （由氣體）冷凝;（使氣體）凝結(jié)

transparent /tr?ns'p?r?nt/ adj. 透明的;清澈的

muffle /'m?fl/ v. 壓抑（聲音）;使（聲音）降低;使聽不清

accumulate /?'kju?mj?le?t/ v.（數(shù)量）逐漸增加;（數(shù)額）逐漸增長

Debts began to accumulate.