Wonderful Natural Phenomena in Winter冬日美妙的自然现象

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.

白霜是预示冬天到来的最早预告。白霜的英文名来源于古英语单词（hoar，意思是“显得古老”），它是一层薄薄的羽毛状冰层，通常在晴朗的寒夜凝结于物体表面。晴天使地面温度比周围空气的温度下降更快，大气中的湿气在与地面接触时凝结成固体。即使地面上几英尺的空气远高于冰点，也会形成这种冰霜，并且通常在日出后一两个小时内融化。

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.

当雨点落在温度在冰点以下的表面时，会立即形成所谓的“雨凇”，即光滑、透明的冰层。雨雪过后，可见雨凇覆盖在树枝和植物上。

HARD RIME

硬雾淞

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.

随着天气变冷，可能会出现冻雾。当冻雾与风结合时，物体的迎风面会形成硬雾凇。Rime字面意思是“白霜”，“软雾凇”与厚厚的白霜非常相似，但在气象层面上略有不同。此外，硬雾凇要更厚更硬，由高密度的不规则冰晶团聚合在一起形成。

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.

在湖泊周围（偶尔出现湖泊效应降雪）和沿海地区，最常出现满足雷雪天气的气候条件。在这些地方，阳光让地面温度上升，导致相对温暖潮湿的不稳定空气柱上升，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.

但光有云层并不能产生雷雪。只有当云层和地面之间的空气层比云层温度高，但仍然冷到足以形成降雪，并且风向切变将温暖的空气稍微向上推时，才会形成雷雪。

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

雪通常会掩盖雷声，这意味着许多时候可能听不到雷声。

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.

當积雪一年又一年堆积起来，就形成了“粒雪”。粒雪比普通积雪的密度大得多，这是两个因素导致的：在温暖的季节，一部分雪融化使积雪堆积得更紧密;在寒冷的季节，新雪落在密实的积雪顶部，将晶体推到一起而不融化。

Word Study

condense /k?n'dens/ v. （由气体）冷凝;（使气体）凝结

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

muffle /'m?fl/ v. 压抑（声音）;使（声音）降低;使听不清

accumulate /?'kju?mj?le?t/ v.（数量）逐渐增加;（数额）逐渐增长

Debts began to accumulate.