NASA首次進行雪花融化模擬，美到窒息

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This model reproduces key features of melting snowflakes that have been observed in nature: first, meltwater gathers in any concave regions of the snowflake"s surface. These liquid-water regions merge as they grow and eventually form a shell of liquid around an ice core, finally developing into a water drop. Credit: NASA

該模型再現了自然界中觀察到的融化雪花的主要特徵：首先，融水會在雪花表面的任何凹陷處聚集。這些液態水區域隨著它們的生長而融合，最終形成一個圍繞在冰核周圍的液體殼，最終形成水滴。來源：NASA

NASA has produced the first three-dimensional numerical model of melting snowflakes in the atmosphere. Developed by scientist Jussi Leinonen of NASA"s Jet Propulsion Laboratory in Pasadena, California, the model provides a better understanding of how snow melts can help scientists recognize the signature in radar signals of heavier, wetter snow—the kind that breaks power lines and tree limbs—and could be a step toward improving predictions of this hazard.

美國國家宇航局已經製作了第一個在大氣中融化雪花的三維數值模型。該模型由美國宇航局噴氣推進實驗室的科學家Jussi Leinonen在加利福尼亞州帕薩迪納市開發，該模型可以更好地理解了雪是如何融化的，幫助科學家認識雷達信號中較重，較潮濕的雪的特徵 - 這種打破電線和樹枝的雪花 - 這可能是朝著改善這種危險的預測邁出的一步。

Snowflake research is one of many ways that NASA studies the frozen regions of Earth, collectively known as the cryosphere.

雪花研究是NASA研究地球凍結區域的許多方法之一，統稱為冰凍圈。

Leinonen"s model reproduces key features of melting snowflakes that have been observed in nature. First, meltwater gathers in any concave regions of the snowflake"s surface. These liquid-water regions then merge to form a shell of liquid around an ice core, and finally develop into a water drop. The modeled snowflake shown in the video is less than half an inch (one centimeter) long and composed of many individual ice crystals whose arms became entangled when they collided in midair.

Leinonen的模型再現了自然界中已經觀察到的融化的雪花的主要特徵。首先，融水會聚集在雪花表面的任何凹陷處。這些凹陷處的液態水隨後合併，形成一個圍繞冰核的液體殼，並最終形成水滴。視頻中顯示的模擬雪花長度不到半英寸（1厘米），由許多單個冰晶組成，當它們在半空中相撞時，它們會纏繞在一起。

Leinonen said he got interested in modeling melting snow because of the way it affects observations with remote sensing instruments. A radar "profile" of the atmosphere from top to bottom shows a very bright, prominent layer at the altitude where falling snow and hail melt—much brighter than atmospheric layers above and below it. "The reasons for this layer are still not particularly clear, and there has been a bit of debate in the community," Leinonen said.Simpler models can reproduce the bright melt layer, but a more detailed model like this one can help scientists to understand it better, particularly how the layer is related to both the type of melting snow and the radar wavelengths used to observe it.

Leinonen表示，他對模擬融雪的建模很感興趣，因為它影響了遙感儀器的觀測。從上到下的大氣雷達「剖面」顯示了一個非常明亮，突出的高度層，在這裡降雪和冰雹融化 - 比上下的大氣層明亮得多。 Leinonen說：「這一層的原因還不是特別清楚，社區中也存在一些爭論。」模型可以再現明亮的融化層，但像這樣的更詳細的模型可以幫助科學家更好地理解它，特別是該層如何與融雪的類型和用於觀測它的雷達波長相關。

A paper on the numerical model, titled "Snowflake melting simulation using smoothed particle hydrodynamics," recently appeared in the Journal of Geophysical Research - Atmospheres. Some of the most remote places on Earth are showing signs of change, with potentially global impacts.

最近在《地球物理研究- 大氣》雜誌上發表了題為「利用平滑粒子流體動力學進行雪花融化模擬」的數值模型的論文。地球上一些最偏遠的地方正在顯示出變化的跡象，並可能對全球產生影響。

In 2018, NASA is scheduled to launch two new satellite missions and conduct an array of field research that will enhance our view of Earth"s ice sheets, glaciers, sea ice, snow cover and permafrost. Collectively, these frozen regions are known as the cryosphere. Over the course of the year NASA will share an inside look at what the agency is doing to better understand this critical component of our home planet.

2018年，美國國家航空航天局計劃發射兩個新的衛星，並進行一系列實地研究，以增強我們對地球冰蓋，冰川，海冰，積雪和永久凍土的認識。總的來說，這些冰凍地區被稱為冰凍圈。在這一年的時間裡，美國航空航天局將分享一個內部的觀察，看看該機構正在做什麼，以更好地了解我們的地球家園的這個關鍵組成部分。

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