Loftsveðurfar

Loftsveðurfar is the term used in meteorology to describe the conditions of the Earth's atmosphere at altitudes above the planetary boundary layer, primarily in the middle to upper troposphere and the lower stratosphere. It is studied separately from surface weather but is tightly connected to it, since upper-atmosphere circulation patterns drive the development and movement of weather systems at the surface. Key features include jet streams, upper-level troughs and ridges, and variations in tropopause height.

Data and methods: Observations come from radiosondes launched by weather balloons, aircraft, and satellites, providing profiles of temperature, humidity and wind. These observations are assimilated into numerical weather prediction models and used to produce upper-air charts at standard pressure levels (for example 500 hPa and 250 hPa), which help forecasters assess the overall weather pattern.

Applications and impacts: Loftsveðurfar influences the track and development of cyclones, the intensity of precipitation, and the potential for atmospheric instability. It is crucial for aviation, where upper-level winds and turbulence forecasts affect routing and safety.

Seasonal and long-term aspects: Upper-atmosphere circulation varies with season and is sensitive to climate change. Changes in jet-stream position and strength, as well as stratosphere-troposphere interactions, can modulate mid-latitude weather and extreme events. Long-term studies analyze trends in upper-air temperature and wind fields through reanalysis data.