scholarly journals Atmospheric effects in Scotland of the AD 1783–84 Laki eruption in Iceland

The Holocene ◽  
2021 ◽  
pp. 095968362098805
Author(s):  
Alastair G Dawson ◽  
Martin P Kirkbride ◽  
Harriet Cole
Keyword(s):  
Pressure Fluctuations ◽  
Negative Temperature ◽  
Air Pressure ◽  
Simultaneous Occurrence ◽  
Atmospheric Effects ◽  
Discrete Groups ◽  
Weather Patterns ◽  
Air Temperatures ◽  
Air Temperature Anomaly ◽  
Forced Cooling

Daily weather diaries and meteorological records from Scotland reveal complex weather patterns following the 1783–84 fissure eruption of the Laki volcano, Iceland. Four diarists in eastern and northern Scotland describe the near-simultaneous occurrence of discrete groups of days characterised by ‘foggy’, ‘gloomy’ and ‘hazy’ conditions during June and July 1783. The weather records suggest that an ash-rich portion of the initial plume may have arrived synchronously across eastern Scotland on June 15th, 5 days after the first eruption in Iceland, and lingered for between 5 and 7 days. Following a 3-day interval of fine weather, a sulphurous haze arrived on June 24th and persisted for the rest of the summer. As the summer progressed air pollution episodes became shorter, less frequent and more influenced by air pressure fluctuations. The effect of the eruption on Scotland’s climate is unclear although a negative air temperature anomaly of 1.5°C to 2.5°C below the decadal average occurred in September 1783 lasting for 16 days at Dalkeith and 33 days at Fochabers. The 1783–84 winter in Scotland was one of the coldest in recent centuries and was accompanied by prolonged snow and frost through the first 4 months of 1784. During this period, temperatures in eastern Scotland averaged 2.0°C to 2.6°C below the decadal average. The duration and amplitude of post-eruption negative temperature anomalies appear to have been strongly associated with synoptic air pressure and wind flow patterns and not simply related to volcanically-forced cooling. This challenges the hypothesis that the Laki eruptions were responsible for the sustained lowering of air temperatures over the three successive winters of 1783–84, 1784–85 and 1785–86.

scholarly journals Retrieval of Summer Sea Ice Concentration in the Pacific Arctic Ocean from AMSR2 Observations and Numerical Weather Data Using Random Forest Regression

2021 ◽  
Vol 13 (12) ◽  
pp. 2283
Author(s):  
Hyangsun Han ◽  
Sungjae Lee ◽  
Hyun-Cheol Kim ◽  
Miae Kim
Keyword(s):  
Random Forest ◽  
Sea Ice ◽  
Arctic Ocean ◽  
Open Water ◽  
The Arctic ◽  
Atmospheric Effects ◽  
Sea Ice Concentration ◽  
Air Temperatures ◽  
The Pacific ◽  
Ice Concentration

The Arctic sea ice concentration (SIC) in summer is a key indicator of global climate change and important information for the development of a more economically valuable Northern Sea Route. Passive microwave (PM) sensors have provided information on the SIC since the 1970s by observing the brightness temperature (TB) of sea ice and open water. However, the SIC in the Arctic estimated by operational algorithms for PM observations is very inaccurate in summer because the TB values of sea ice and open water become similar due to atmospheric effects. In this study, we developed a summer SIC retrieval model for the Pacific Arctic Ocean using Advanced Microwave Scanning Radiometer 2 (AMSR2) observations and European Reanalysis Agency-5 (ERA-5) reanalysis fields based on Random Forest (RF) regression. SIC values computed from the ice/water maps generated from the Korean Multi-purpose Satellite-5 synthetic aperture radar images from July to September in 2015–2017 were used as a reference dataset. A total of 24 features including the TB values of AMSR2 channels, the ratios of TB values (the polarization ratio and the spectral gradient ratio (GR)), total columnar water vapor (TCWV), wind speed, air temperature at 2 m and 925 hPa, and the 30-day average of the air temperatures from the ERA-5 were used as the input variables for the RF model. The RF model showed greatly superior performance in retrieving summer SIC values in the Pacific Arctic Ocean to the Bootstrap (BT) and Arctic Radiation and Turbulence Interaction STudy (ARTIST) Sea Ice (ASI) algorithms under various atmospheric conditions. The root mean square error (RMSE) of the RF SIC values was 7.89% compared to the reference SIC values. The BT and ASI SIC values had three times greater values of RMSE (20.19% and 21.39%, respectively) than the RF SIC values. The air temperatures at 2 m and 925 hPa and their 30-day averages, which indicate the ice surface melting conditions, as well as the GR using the vertically polarized channels at 23 GHz and 18 GHz (GR(23V18V)), TCWV, and GR(36V18V), which accounts for atmospheric water content, were identified as the variables that contributed greatly to the RF model. These important variables allowed the RF model to retrieve unbiased and accurate SIC values by taking into account the changes in TB values of sea ice and open water caused by atmospheric effects.

Impact of high air temperatures on Brassicacae crops in southern Ontario

2006 ◽  
Vol 86 (4) ◽  
pp. 1209-1215 ◽  
Author(s):  
Jon Warland ◽  
Alan W McKeown ◽  
Mary Ruth McDonald
Keyword(s):  
Vegetable Crops ◽  
Cool Season ◽  
Marketable Yield ◽  
Weather Patterns ◽  
Air Temperatures ◽  
The Family ◽  
Chi Squared ◽  
Hot Weather ◽  
Insight Into ◽  
Seasonal Weather

The yield patterns of many cool season vegetable crops were observed to be different from the gradual increase in yields that has been reported over time for corn and soybeans in Ontario. A study was conducted to determine if there was a relationship between yield and seasonal weather patterns for five vegetables (broccoli, cabbage, cauliflower, radish and rutabaga) in the family Brassicacae. The iterative chi-squared technique was used to identify correlations between daily temperature and marketable yield. Yields of all five of the crops showed some damage due to hot weather in August. For cauliflower, cabbage and rutabaga there was roughly a 10% yield loss for every 10 d that the temperature reached 30°C or above during the growing season. These results shed new insight into the mechanisms by which weather affects yield. Key words: Cabbage, broccoli, cauliflower, radish, rutabaga, yield, climate

scholarly journals Chaotic air pressure fluctuations during departure of air bubbles from two neighbouring nozzles

2012 ◽  
Vol 33 (1) ◽  
pp. 127-137 ◽  
Author(s):  
Romuald Mosdorf ◽  
Tomasz Wyszkowski
Keyword(s):  
Correlation Dimension ◽  
Cross Correlation ◽  
Pressure Fluctuations ◽  
Air Pressure ◽  
Hydrodynamic Interactions ◽  
Largest Lyapunov Exponent ◽  
Distilled Water ◽  
Air Bubbles ◽  
Bubble Interactions ◽  
Correlation Exponent

Chaotic air pressure fluctuations during departure of air bubbles from two neighbouring nozzlesIn the experiment, bubbles were generated from two brass nozzles with inner diameters of 1.1 mm. They were submerged in the glass tank filled with distilled water. There have been measured the air pressure fluctuations and the signal from the laser-phototransistor sensor. For analysis of the pressure signal the correlation (the normalized cross - correlation exponent) and non-linear analyses have been used. It has been shown that hydrodynamic interactions between bubbles can lead to bubble departure synchronization. In this case the bubble departures become periodic. The results of calculation of correlation dimension and the largest Lyapunov exponent confirm that hydrodynamic bubble interactions observed for 4 mm spacing between nozzels cause the periodic bubble departures from two neighbouring nozzles.

Comparison of wind-induced air pressure fluctuations at sites with different land use

2021 ◽  
Author(s):  
Manuel Mohr ◽  
Thomas Laemmel ◽  
Martin Maier ◽  
Sven Kolbe ◽  
Christopher Jung ◽  
...  
Keyword(s):  
Land Use ◽  
Surface Roughness ◽  
Wind Speed ◽  
Trace Gases ◽  
Pressure Fluctuations ◽  
Air Pressure ◽  
High Wind ◽  
High Wind Speed ◽  
Site Specific ◽  
Quadratic Relationship

<p>Previous studies showed at a forest site, that small air pressure fluctuations that are generated during periods of high wind speed significantly enhance topsoil gas transport, which is called pressure-pumping. The strength of these air pressure fluctuations can be described by the pressure pumping coefficient (<em>PPC</em>) which is defined as the mean absolute slope between two measurements (0.5 s) per 30 min interval. It was shown that at this site a quadratic relationship exists between the <em>PPC </em>and above canopy wind speed.</p><p>To investigate the variability of small air pressure fluctuations, high-frequency airflow and air pressure measurements were carried out at ten European and American sites with different land use (grassland, crop, forest, urban). The air pressure fluctuations were generally measured above the soil surface and airflow above the site-specific canopy (above trees in forests, on the top of a high building in the city). The measurements took place between 2016 and 2020 and commonly lasted at least one month per site.</p><p>Results show that the site-specific <em>PPC </em>increases in a quadratic relationship with above-canopy wind speed at all sites. The data was very close to a quadratic relationship at sites with rather uniform forests and level topography (R² > 0.92), while more complex sites revealed a larger scattering of this correlation (R² > 0.65).</p><p>At some sites, the <em>PPC </em>is also highly dependent on the prevailing wind direction. It is shown that the local surface roughness of the plant canopy can be excluded as a main driver of the PPC. Moreover, analysis of surface roughness parameters suggests that the topographic exposure around the measurement sites is responsible for the variability in the <em>PPC</em>.</p><p>However, due to the limited data availability and the complexity of the sites (topography, canopy, buildings), it cannot yet be ruled out that other effects have an influence on the <em>PPC</em>. In any case, from the results it can be inferred that wind-induced air pressure fluctuations responsible for pressure-pumping are detectable over a variety of natural and artificial surfaces. It must, therefore, be assumed that they have the potential to increase the diffusion-limited transport rate of trace gases in the soil as well as the soil-atmosphere exchange of trace gases over a large number of surfaces during periods of high wind speed.</p>

Nasal air pressure fluctuations under different conditions

1927 ◽  
Vol 23 (8) ◽  
pp. 855-855
Author(s):  
N. Khodyakov
Keyword(s):  
Pressure Fluctuations ◽  
Air Pressure

Citing the literature data on this issue, N. Khodyakov reports his observations on 36 patients. In this number 6 people had approximately normal relations in the airways, others were with various pathological processes: deviation of the septum, hypertrophic and atrophic processes, adenoids, disease of the Highmor's cavities and labyrinths.

The directional spectrum of ocean waves, and processes of wave generation

1962 ◽  
Vol 265 (1322) ◽  
pp. 286-315 ◽  
Keyword(s):  
Pressure Fluctuations ◽  
Wave Spectrum ◽  
Ocean Waves ◽  
Wave Generation ◽  
Air Pressure ◽  
Sea Surface ◽  
Shear Instability ◽  
Main Stage ◽  
Sea Waves ◽  
Directional Spectrum

This paper describes some recent observations of the directional spectrum of sea waves and of air pressure fluctuations at the sea surface, and discusses their implications for theories of wave generation. The angular spread of the wave energy in the generating area is found to be comparable with the ‘resonance angle’ sec -1 ( σU/g ) ( σ = wave frequency, U = wind speed) but lies slightly below it in the middle range of frequencies. The best fit to the directional spectrum F ( σ, ɸ ) is shown to be a cosine-power law: F ( σ, ɸ ) ∝ cos 2s (1/2 ɸ ), where s decreases as σ in ­ creases. At the higher frequencies the total spectrum satisfies the equilibrium law: F ( σ ) ∝ σ -5 . The initial stages of wave generation are attributed to turbulence in the air stream, and the main stage of growth to the shear instability mechanism described by Miles. At the highest frequencies the form of the spectrum suggests that wave breaking plays a predominant part, as proposed by Phillips. The broadening of the angular distribution at the highest frequencies may also be due partly to third-order ‘resonant’ interactions among components of the wave spectrum . The air-pressure fluctuations are nearly in phase with the vertical displacement of the sea surface (over most of the frequency range) and are consistent with the shear-flow model proposed by Miles. The turbulent component of the air pressure is much smaller than was previously supposed.

scholarly journals Satellite observations of surface temperature during the March 2015 total solar eclipse

2016 ◽  
Vol 374 (2077) ◽  
pp. 20150219 ◽  
Author(s):  
Elizabeth Good
Keyword(s):  
Surface Temperature ◽  
Solar Eclipse ◽  
Land Surface ◽  
Total Solar Eclipse ◽  
Atmospheric Effects ◽  
Near Surface ◽  
Full Characterization ◽  
Air Temperatures ◽  
Infrared Imager ◽  
Land Surface Temperatures

The behaviour of remotely sensed land surface temperatures (LSTs) from the spinning-enhanced visible and infrared imager (SEVIRI) during the total solar eclipse of 20 March 2015 is analysed over Europe. LST is found to drop by up to several degrees Celcius during the eclipse, with the minimum LST occurring just after the eclipse mid-point (median=+1.5 min). The drop in LST is typically larger than the drop in near-surface air temperatures reported elsewhere, and correlates with solar obscuration ( r =−0.47; larger obscuration = larger LST drop), eclipse duration ( r =−0.62; longer duration = larger LST drop) and time ( r =+0.37; earlier eclipse = larger LST drop). Locally, the LST drop is also correlated with vegetation (up to r =+0.6), with smaller LST drops occurring over more vegetated surfaces. The LSTs at locations near the coast and at higher elevation are also less affected by the eclipse. This study covers the largest area and uses the most observations of eclipse-induced surface temperature drops to date, and is the first full characterization of satellite LST during an eclipse (known to the author). The methods described could be applied to Geostationary Operational Environmental Satellite (GOES) LST data over North America during the August 2017 total solar eclipse. This article is part of the themed issue ‘Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse’.

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