Meteorological Aspects of Climate Change
and Climate Variability

Introduction

Climate variability (the natural variation of climate at a location) and climate change (anthropogenic causes of climate change) manifest themselves in a variety of ways over a wide range of spatial and tempo ral scales. Examples are temperature change, precipitation change, and changes in the occurrences of hazardous and damaging weather phenomena (extreme weather). Climate variability and change may be detrimental or even beneficial to a region depending o n their resultant effects.

Climate Variability and Change

  1. Climate variability: the natural variation in climate.

    1. Studies of signals such as El Ni ño-Southern Oscillation (ENSO), quasi-biennial oscillation, atmospheric carbon dioxide, solar radiation variation, and volcanic activity.
    2. Climate variability using paleosols to obtain more information about prehistoric climates is helping to uncover some of the dramat ic natural events in the past.

  1. Climate change: possible anthropogenic causes of variation in climate.
  2. Global warming
  3. Global cooling

Extreme Weather

Extreme weather is weather phenomena occurring outside of one’s experience leading to significant societal impacts (e.g., property damage, loss of life, economic impacts).

  1. Synoptic-scale (~10000 km) storms

  1. Blizzards are storms with winds greater than 35 miles per hour and visibility less than ¼ mile in snow and/or blowing snow.

    1. The early spring (early April) Northern Plains blizzard of 1997, named "Hannah"
    2. Superstorm of 1993

  1. Hurricanes. The Atlantic season of 1996 tied the record for the most activity, while 1997’s season has been relatively quiet. In the easte rn Pacific, activity has been above average with three storms making landfall in northwestern Mexico.

  1. Mesoscale storms

    1. Severe local storms

1. Hail causes millions of dollars of damage to crops and property each year. This year in Jamestown, North Dakota, la rge hailstones damaged a considerable portion of the city. Last year, Grand Forks experienced a severe thunderstorm with hailstones up to 2 inches in diameter with millions in damage to cars, homes, crops, and other property. Some of the largest hail ob served (with diameters to 6 inches) falls in the region known as "Tornado Alley" over portions of Kansas, Oklahoma, and Texas.

2. Tornadoes are probably the most feared natural phenomena. More occur on the North American continent than anywhere else in the world, though they can (and have) affect(ed) nearly all regions of the world. With wind speeds in the st rongest tornadoes exceeding 300 miles per hour, these storms can cause enormous damage. Fortunately, their scale is relatively small (diameters range from about 50 feet to over one mile) so that they affect a limited area.

    1. general
    2. research
    3. public safety

    1. Microbursts are small-scale (~1 km) bursts of winds originating in thunderstorms. They can lead to surfac e winds in excess of 100 miles per hour, causing damage similar to a tornado. They also present an aviation hazard since extreme wind shear occurs with this phenomenon.

  1. Scales of weather phenomena

  1. Temporal: ranges from seconds to decades, even centuries.
  2. Spatial: human (1 m) to global (10000 km).

  1. Some regional data

  1. Grand Forks maximum and minimum temperatures
  2. Grand Forks precipitation
  3. Grand Forks 1997-1998 Winter Season snowfall

 

Summary

While virtually no doubt exists that we, as a region, have witnessed a wide variation in weather over the past decade, it is not presently possible to show a causal relationship between human activity and climate change. Any climate change is superimposed on natural climate variability and it is difficult to discern the two. More investigation of the above subjects is needed, which is part of RWIC’s research mission.

University of North Dakota / School of Aerospace Sciences / Atmospheric Science Department

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