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Global terrestrial stilling
Global terrestrial stilling is the decrease of wind speed observed near the Earth's surface between the 1980s until around 2010, originally termed "stilling". This slowdown of near-surface terrestrial winds mainly affected mid-latitude regions of both hemispheres, with a global average reduction of −0.140 m s−1 dec−1 (meters per second per decade) or between 5 and 15% over the past 50 years. With high-latitude (> 75° from the equator) showing increases in both hemispheres. In contrast to the observed weakening of winds over continental surfaces, winds have tended to strengthen over ocean regions. There has been a (partial) reversal of the trend since around 2010.
The exact cause(s) of the global terrestrial stilling are uncertain and has been mainly attributed to two major drivers: (i) changes in large scale atmospheric circulation, and (ii) an increase of surface roughness due to e.g. forest growth, land use changes, and urbanization.
Given climate change, changes in wind speed are currently a potential concern for society, due to their impacts on a wide array of spheres, such as wind power generation, ecohydrological implications for agriculture and hydrology, wind-related hazards and catastrophes, or air quality and human health, among many others.
The attribution of this weakening of terrestrial near-surface wind speed is not conclusive, probably because of several factors which interact simultaneously, and may change in space in time. Scientists have pointed out various major causes influencing this slowdown in wind speed:
(i) The increase in land-surface roughness (e.g. forest growth, land use changes and urbanization) near meteorological station where anemometer instruments measure wind lead to a reinforcement of friction force that weaken low-level winds.
(ii) The variability of large-scale atmospheric circulation, associated with the poleward expansion of the Hadley cell and the shifting of centers of action (i.e. anticyclones and cyclones) controlling changes in near-surface wind speed.
(iii) The changes in how wind speed is measured, including the deterioration or instrumental drift of anemometer devices; the technological improvement of anemometers; anemometer height changes; shifts in measurements sites; changes in the environment around the monitoring station; calibration issues; and measuring time intervals.
(iv) The "global dimming", i.e., the decrease in the amounts of solar radiation reaching the Earth's surface due to increased aerosol and greenhouse gas concentrations, forces a stabilization of the atmosphere resulting in weak winds.
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Global terrestrial stilling
Global terrestrial stilling is the decrease of wind speed observed near the Earth's surface between the 1980s until around 2010, originally termed "stilling". This slowdown of near-surface terrestrial winds mainly affected mid-latitude regions of both hemispheres, with a global average reduction of −0.140 m s−1 dec−1 (meters per second per decade) or between 5 and 15% over the past 50 years. With high-latitude (> 75° from the equator) showing increases in both hemispheres. In contrast to the observed weakening of winds over continental surfaces, winds have tended to strengthen over ocean regions. There has been a (partial) reversal of the trend since around 2010.
The exact cause(s) of the global terrestrial stilling are uncertain and has been mainly attributed to two major drivers: (i) changes in large scale atmospheric circulation, and (ii) an increase of surface roughness due to e.g. forest growth, land use changes, and urbanization.
Given climate change, changes in wind speed are currently a potential concern for society, due to their impacts on a wide array of spheres, such as wind power generation, ecohydrological implications for agriculture and hydrology, wind-related hazards and catastrophes, or air quality and human health, among many others.
The attribution of this weakening of terrestrial near-surface wind speed is not conclusive, probably because of several factors which interact simultaneously, and may change in space in time. Scientists have pointed out various major causes influencing this slowdown in wind speed:
(i) The increase in land-surface roughness (e.g. forest growth, land use changes and urbanization) near meteorological station where anemometer instruments measure wind lead to a reinforcement of friction force that weaken low-level winds.
(ii) The variability of large-scale atmospheric circulation, associated with the poleward expansion of the Hadley cell and the shifting of centers of action (i.e. anticyclones and cyclones) controlling changes in near-surface wind speed.
(iii) The changes in how wind speed is measured, including the deterioration or instrumental drift of anemometer devices; the technological improvement of anemometers; anemometer height changes; shifts in measurements sites; changes in the environment around the monitoring station; calibration issues; and measuring time intervals.
(iv) The "global dimming", i.e., the decrease in the amounts of solar radiation reaching the Earth's surface due to increased aerosol and greenhouse gas concentrations, forces a stabilization of the atmosphere resulting in weak winds.