Snow white sushi roll
The physical properties of snow vary considerably from event to event, sample to sample, and over time. Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, snow white sushi roll on the ground where they undergo further changes.
Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air. Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, which freeze in hexagonal-shaped crystals. Major snow-prone areas include the polar regions, the northernmost half of the Northern Hemisphere and mountainous regions worldwide with sufficient moisture and cold temperatures. Below 500: annually, but not in all of its territory. Snow develops in clouds that themselves are part of a larger weather system. The physics of snow crystal development in clouds results from a complex set of variables that include moisture content and temperatures.
The resulting shapes of the falling and fallen crystals can be classified into a number of basic shapes and combinations thereof. Snow clouds usually occur in the context of larger weather systems, the most important of which is the low-pressure area, which typically incorporate warm and cold fronts as part of their circulation. Mid-latitude cyclones are low-pressure areas which are capable of producing anything from cloudiness and mild snow storms to heavy blizzards. A warm front can produce snow for a period as warm, moist air overrides below-freezing air and creates precipitation at the boundary. Often, snow transitions to rain in the warm sector behind the front. The same effect occurring over bodies of salt water is termed ocean-effect or bay-effect snow. The effect is enhanced when the moving air mass is uplifted by the orographic influence of higher elevations on the downwind shores.
This uplifting can produce narrow but very intense bands of precipitation which may deposit at a rate of many inches of snow each hour, often resulting in a large amount of total snowfall. The areas affected by lake-effect snow are called snowbelts. Orographic or relief snowfall is created when moist air is forced up the windward side of mountain ranges by a large-scale wind flow. Mountain waves have also been found to help enhance precipitation amounts downwind of mountain ranges by enhancing the lift needed for condensation and precipitation. A snowflake consists of roughly 1019 water molecules which are added to its core at different rates and in different patterns depending on the changing temperature and humidity within the atmosphere that the snowflake falls through on its way to the ground. As a result, snowflakes differ from each other though they follow similar patterns.
Once a droplet has frozen, it grows in the supersaturated environment—one where air is saturated with respect to ice when the temperature is below the freezing point. Micrography of thousands of snowflakes from 1885 onward, starting with Wilson Alwyn Bentley, revealed the wide diversity of snowflakes within a classifiable set of patterns. Closely matching snow crystals have been observed. Ukichiro Nakaya developed a crystal morphology diagram, relating crystal shapes to the temperature and moisture conditions under which they formed, which is summarized in the following table. Nakaya discovered that the shape is also a function of whether the prevalent moisture is above or below saturation.
Forms below the saturation line trend more towards solid and compact while crystals formed in supersaturated air trend more towards lacy, delicate, and ornate. Many more complex growth patterns also form, which include side-planes, bullet-rosettes, and planar types, depending on the conditions and ice nuclei. Magono and Lee devised a classification of freshly formed snow crystals that includes 80 distinct shapes. Snow accumulates from a series of snow events, punctuated by freezing and thawing, over areas that are cold enough to retain snow seasonally or perennially. Major snow-prone areas include the Arctic and Antarctic, the Northern Hemisphere, and alpine regions. Snow flurry, snow shower, snow storm and blizzard describe snow events of progressively greater duration and intensity. Snowstorm intensity may be categorized by visibility and depth of accumulation.
Heavy: visibility is less than 0. The International Classification for Seasonal Snow on the Ground defines “height of new snow” as the depth of freshly fallen snow, in centimeters as measured with a ruler, that accumulated on a snowboard during an observation period of 24 hours, or other observation interval. January or nearly half of the land surface in that hemisphere. 2006 suggests a reduction of 0.
