scholarly journals Effects of vernal equinox solar eclipse on temperatures and wind directions in Switzerland

2017 ◽  
Author(s):  
Werner Eugster ◽  
Carmen Emmel ◽  
Sebastian Wolf ◽  
Nina Buchmann ◽  
Joseph P. McFadden ◽  
...  
Keyword(s):  
Air Temperature ◽  
Solar Eclipse ◽  
Wind Direction ◽  
Temperature Drop ◽  
Swiss Alps ◽  
Maximum Temperature ◽  
Small Scale ◽  
Near Surface ◽  
Vernal Equinox ◽  
Cold Air

Abstract. The vernal equinox total solar eclipse of 20 March 2015 produced a maximum occultation of 65.8 to 70.1 % over Switzerland during the morning hours (09:22 to 11:48 CET). Skies were generally clear over the Swiss Alps due to a persistent high-pressure band between the UK and Russia associated with a rather weak pressure gradient over the continent. To assess the effects of penumbral shading on near-surface meteorology across Switzerland, air temperature data measured at 10-minute intervals at 184 MeteoSwiss weather stations that reported air temperature at 10-minute intervals were used. Wind speed and direction data were available from 165 of these stations. Additionally, six Swiss FluxNet eddy covariance flux (ECF) sites provided turbulent measurements at 20 Hz resolution. During maximum occultation the temperature drop was up to 5.8 K at a mountain site where cold air can pool in the topographic depression of the weather station. The bootstrapped average of the maximum temperature drops of all 184 MeteoSwiss sites during the solar eclipse was 1.51 ± 0.02 K (mean ± SE). A detailed comparison with literature values since 1834 showed a temperature decrease by 2.6 ± 1.7 K (average of all reports) with extreme values up to 11 K. On fair weather days under weak larger scale pressure gradients, local thermo-topographic wind systems develop that are driven by small-scale pressure and temperature gradients. At one ECF site, the penumbral shading delayed the morning transition from down-valley to up-valley wind conditions, and at another site, it prevented this transition from occurring at all. Data from the 165 MeteoSwiss sites measuring wind direction did not show a consistent pattern of wind direction response to the passing of the penumbral shadow. These results suggest that the local topographic setting had an important influence on the temperature drop and the wind flow patterns during the eclipse. Still, results tend to lend support to a recent theory that the anticyclonic cold-air outflow from the center of the eclipse only extends ≈ 1600 km outwards, with cyclonic flow beyond that distance. This contrasts with an earlier theory that the anticyclonic outflow should reach as far as ≈ 2400 km from the center of the eclipse, which would have included all of Switzerland during the 2015 eclipse. Nevertheless, a significant cyclonic effect of the passing penumbral shadow was found in the elevation range ≈ 1700–2700 m a.s.l., but not at lower elevations of the Swiss Plateau. Thus, measurable effects of penumbral shading on the local wind system could be even found at ≈ 2000 km from the path of the eclipse (that is, Switzerland during the 2015 eclipse).

scholarly journals Effects of vernal equinox solar eclipse on temperature and wind direction in Switzerland

2017 ◽  
Vol 17 (24) ◽  
pp. 14887-14904 ◽  
Author(s):  
Werner Eugster ◽  
Carmen Emmel ◽  
Sebastian Wolf ◽  
Nina Buchmann ◽  
Joseph P. McFadden ◽  
...  
Keyword(s):  
Solar Eclipse ◽  
Wind Direction ◽  
Extreme Values ◽  
Temperature Drop ◽  
Swiss Alps ◽  
Maximum Temperature ◽  
Small Scale ◽  
Near Surface ◽  
Vernal Equinox ◽  
Cold Air

Abstract. The vernal equinox total solar eclipse of 20 March 2015 produced a maximum occultation of 65.8–70.1 % over Switzerland during the morning hours (09:22 to 11:48 CET). Skies were generally clear over the Swiss Alps due to a persistent high-pressure band between the UK and Russia associated with a rather weak pressure gradient over the continent. To assess the effects of penumbral shading on near-surface meteorology across Switzerland, air temperature data measured at 10 min intervals at 184 MeteoSwiss weather stations were used. Wind speed and direction data were available from 165 of these stations. Additionally, six Swiss FluxNet eddy covariance flux (ECF) sites provided turbulent measurements at 20 Hz resolution. During maximum occultation, the temperature drop was up to 5.8 K at a mountain site where cold air can pool in a topographic depression. The bootstrapped average of the maximum temperature drops of all 184 MeteoSwiss sites during the solar eclipse was 1.51 ± 0.02 K (mean ± SE). A detailed comparison with literature values since 1834 showed a temperature decrease of 2.6 ± 1.7 K (average of all reports), with extreme values up to 11 K. On fair weather days under weak larger-scale pressure gradients, local thermo-topographic wind systems develop that are driven by small-scale pressure and temperature gradients. At one ECF site, the penumbral shading delayed the morning transition from down-valley to up-valley wind conditions. At another site, it prevented this transition from occurring at all. Data from the 165 MeteoSwiss sites measuring wind direction did not show a consistent pattern of wind direction response to the passing of the penumbral shadow. These results suggest that the local topographic setting had an important influence on the temperature drop and the wind flow patterns during the eclipse. A significant cyclonic effect of the passing penumbral shadow was found in the elevation range ≈ 1700–2700 m a. s. l., but not at lower elevations of the Swiss Plateau. This contrasts with an earlier theory that the anticyclonic outflow should reach as far as ≈ 2400 km from the center of the eclipse, which would have included all of Switzerland during the 2015 eclipse. Thus, measurable effects of penumbral shading on the local wind system could be even found at ≈ 2000 km from the path of the eclipse (that is, Switzerland during the 2015 eclipse), and our results tend to lend support to a newer theory that the anticyclonic cold-air outflow from the center of the eclipse only extends ≈ 1600 km outwards, with cyclonic flow beyond that distance.

scholarly journals Evidence of elevation-dependent warming from the Chinese Tian Shan

2021 ◽  
Vol 15 (12) ◽  
pp. 5765-5783
Author(s):  
Lu Gao ◽  
Haijun Deng ◽  
Xiangyong Lei ◽  
Jianhui Wei ◽  
Yaning Chen ◽  
...  
Keyword(s):  
Air Temperature ◽  
Minimum Temperature ◽  
Swiss Alps ◽  
Maximum Temperature ◽  
Current Evidence ◽  
High Mountain ◽  
Regional Warming ◽  
Mean Temperature ◽  
Warming Rate ◽  
Tian Shan

Abstract. The phenomenon in which the warming rate of air temperature is amplified with elevation is termed elevation-dependent warming (EDW). It has been clarified that EDW can accelerate the retreat of glaciers and melting of snow, which can have significant impacts on the regional ecological environment. Owing to the lack of high-density ground observations in high mountains, there is widespread controversy regarding the existence of EDW. Current evidence is mainly derived from typical high-mountain regions such as the Swiss Alps, the Colorado Rocky Mountains, the tropical Andes and the Tibetan Plateau–Himalayas. Rare evidence in other mountain ranges has been reported, especially in arid regions. In this study, EDW features (regional warming amplification and altitude warming amplification) in the Chinese Tian Shan (CTM) were detected using a unique high-resolution (1 km, 6-hourly) air temperature dataset (CTMD) from 1979 to 2016. The results showed that there were significant EDW signals at different altitudes on different timescales. The CTM showed significant regional warming amplification in spring, especially in March, and the warming trends were greater than those of continental China with respect to three temperatures (minimum temperature, mean temperature and maximum temperature). The significance values of EDW above different altitude thresholds are distinct for three temperatures in 12 months. The warming rate of the minimum temperature in winter showed a significant elevation dependence (p<0.01), especially above 3000 m. The greatest altitudinal gradient in the warming rate of the maximum temperature was found above 4000 m in April. For the mean temperature, the warming rates in June and August showed prominent altitude warming amplification but with different significance above 4500 m. Within the CTM, the Tolm Mountains, the eastern part of the Borokoonu Mountains, the Bogda Mountains and the Balikun Mountains are representative regions that showed significant altitude warming amplification on different timescales. This new evidence could partly explain the accelerated melting of snow in the CTM, although the mechanisms remain to be explored.

Technology of Heat and Moisture Regeneration for Ventilation Systems

2021 ◽  
pp. 174-222
Keyword(s):  
Silica Gel ◽  
Air Temperature ◽  
Sodium Acetate ◽  
Temperature Drop ◽  
Sodium Sulphate ◽  
Efficiency Factor ◽  
Cold Air ◽  
Temperature Efficiency ◽  
Heat And Moisture ◽  
Ventilation Systems

The chapter is focused on technology of heat and moisture regeneration for ventilation systems. In the first sub-division recent progress in adsorptive technologies for air dehumidification, heating and conditioning is analyzed. In the next sub-divisions results of original researches of authors on adsorptive heat and moisture regeneration are given. The design of adsorptive heat-moisture regenerator for ventilation systems is shown. Its operation and the results of field tests are described. The technology of regeneration of low-potential heat and moisture by composite sorbent ‘silica gel – sodium sulphate' is suggested. Experimental plots of temperature, absolute and relative humidity at the inlet and the outlet of the apparatus and between cassettes with the composite are given. Correlation of flows switch-over time, airflow rate and temperature drop is stated. The relationships temperature efficiency factor vs. dimensionless temperature drop and moisture efficiency factor vs. absolute humidity dimensionless drop are derived with fair accuracy for engineering calculation. Ability of purposeful modification of the above-mentioned characteristics within broad ranges by changing the half-cycle time, the size of the granules of the adsorbent and its amount is revealed. The mathematical model and algorithm for determining the basic parameters of adsorptive regenerator operating processes are developed. The proposed algorithm involves calculating the volume of air passed through the layer of adsorptive heat-storage material, the concentration of water in the airflow at the outlet of the regenerator, the adsorption, the heat of adsorption, the final temperature of the cold air, the air temperature after mixing the cold air from the street and the warm air in the room at the warm end of the regenerator during inflow, calculation of the final concentration of water in the flow at the cold end of the regenerator, the volume of air passing through the layer of heat-accumulating material, adsorption and heat of adsorption, the final temperature of the air at the cold end of the regenerator, the air temperature after mixing of the cold air from the street and the warm air from the room at the cold end of regenerator during outflow, determining the temperature efficiency coefficient, summarized adsorption and maximal adsorption time. The correlation of air temperatures near the warm and cold end of the regenerator, as well as the temperature efficiency factors calculated according to the proposed algorithm and obtained by experimental way is confirmed. The mathematical modeling of the processes of operation of adsorption regenerators based on composites ‘silica gel – sodium sulphate' and ‘sodium acetate' in the conditions of the typical ventilation system of residential premises is carried out. The dependences of the temperature efficiency factor vs. the time of switching air flows and the velocity of air flow, as well as the temperatures of external and internal air under stationary conditions are shown. An optimal composition of composite adsorbents is stated to be 20% of silica gel and 80% of salt, that is, sodium sulphate or sodium acetate. Due to higher value of maximal adsorption composite ‘silica gel – Na2SO4' is shown to be required in half as much as compared with ‘silica gel – CH3COONa'. The results of the research can be used in the development of energy-efficient ventilation systems and devices for residential and warehouse premises.

scholarly journals The effect of the total solar eclipse of 29 March 2006 on meteorological variables in Greece

2007 ◽  
Vol 7 (21) ◽  
pp. 5543-5553 ◽  
Author(s):  
D. Founda ◽  
D. Melas ◽  
S. Lykoudis ◽  
I. Lisaridis ◽  
E. Gerasopoulos ◽  
...  
Keyword(s):  
Air Temperature ◽  
Solar Eclipse ◽  
Global Radiation ◽  
Surface Wind ◽  
Temperature Drop ◽  
Surface Air Temperature ◽  
Total Solar Eclipse ◽  
Meteorological Variables ◽  
Small Island ◽  
Meteorological Model

Abstract. This paper examines the effect of the total solar eclipse of 29 March 2006 on meteorological variables across Greece. Integrated micrometeorological measurements were conducted at Kastelorizo, a small island within the path of totality, and other sites within the Greek domain, with various degrees of solar obscuration. The observations showed a dramatic reduction in the incoming global radiation and subsequent, pronounced changes in surface air temperature with the lowest temperature values occurring about 15 min after the full phase. The amplitude of the air temperature drop was not analogous to the obscuration percentage but was principally determined by the surrounding environment (mainly the sea influence), the background meteorological conditions and local cloudiness. Surface wind-speed decreased in most sites as a result of the cooling and stabilization of the atmospheric boundary layer. This perturbation provided a unique opportunity to apply a sensitivity analysis on the effect of the eclipse to the Weather Research and Forecast (WRF) numerical mesoscale meteorological model. Strong anomalies, not associated with a dynamic response, were simulated over land especially in surface air temperature. The simulated temperature drop pattern was consistent with the observations.

scholarly journals The Large-eddy Observatory Voitsumra Experiment 2019 (LOVE19) with high-resolution, spatially-distributed observations of air temperature, wind speed, and wind direction from fiber-optic distributed sensing, towers, and ground-based remote sensing

2021 ◽  
Author(s):  
Karl Lapo ◽  
Anita Freundorfer ◽  
Antonia Fritz ◽  
Johann Schneider ◽  
Johannes Olesch ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Boundary Layer ◽  
Wind Speed ◽  
Air Temperature ◽  
Wind Direction ◽  
Fiber Optic ◽  
Layer Structure ◽  
Distributed Sensing ◽  
Near Surface ◽  
Large Eddy

Abstract. The weak-wind Stable Boundary Layer (wwSBL) is poorly described by theory and breaks basic assumptions necessary for observations of turbulence. Understanding the wwSBL requires distributed observations capable of separating between submeso and turbulent scales. To this end, we present the Large Eddy Observatory, Voitsumra Experiment 2019 (LOVE19) which featured 1350 m of fiber optic distributed sensing (FODS) of air temperature and wind speed, as well as an experimental wind direction method, at scales as fine as 1 s and 0.127 m in addition to a suite of point observations of turbulence and ground-based remote sensing. Additionally, flights with a fiber optic cable attached to a tethered balloon provide an unprecedented detailed view of the boundary layer structure with a resolution of 0.254 m and 10 s between 1–200 m height. Two examples are provided demonstrating the unique capabilities of the LOVE19 data for examining boundary layer processes: 1) FODS observations between 1m and ~200 m height during a period of gravity waves propagating across the entire boundary layer and 2) tracking a near-surface, transient submeso structure that causes an intermittent burst of turbulence. All data can be accessed at Zenodo through the DOI https://doi.org/10.5281/zenodo.4312976 (Lapo et al., 2020a).

scholarly journals Quasi-3-D resistivity imaging – mapping of heterogeneous frozen ground conditions using electrical resistivity tomography

2009 ◽  
Vol 3 (3) ◽  
pp. 895-918 ◽  
Author(s):  
C. Kneisel ◽  
A. Bast ◽  
D. Schwindt
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Swiss Alps ◽  
Small Scale ◽  
Frozen Ground ◽  
Resistivity Tomography ◽  
Near Surface ◽  
Glacier Forefield ◽  
Mountain Permafrost ◽  
Ground Conditions

Abstract. Up to now an efficient 3-D geophysical mapping of the subsurface in mountainous environments with rough terrain has not been possible. A merging approach of several closely spaced 2-D electrical resistivity tomography (ERT) surveys to build up a quasi-3-D model of the electrical resistivity is presented herein as a practical compromise for inferring subsurface characteristics and lithology. The ERT measurements were realised in a small glacier forefield in the Swiss Alps with complex terrain exhibiting a small scale spatial variability of surface substrate. To build up the grid for the quasi-3-D measurements the ERT surveys were arranged as parallel profiles and perpendicular tie lines. The measured 2-D datasets were collated into one quasi-3-D file. A forward modelling approach – based on studies at a permafrost site below timberline – was used to optimize the geophysical survey design for the mapping of the mountain permafrost distribution in the investigated glacier forefield. Quasi-3-D geoelectrical imaging is a useful method for mapping of heterogeneous frozen ground conditions and can be considered as a further milestone in the application of near surface geophysics in mountain permafrost environments.

scholarly journals Unmanned aerial vehicles reveal the impact of a total solar eclipse on the atmospheric surface layer

2019 ◽  
Vol 475 (2229) ◽  
pp. 20190212 ◽  
Author(s):  
Sean C. C. Bailey ◽  
Caleb A. Canter ◽  
Michael P. Sama ◽  
Adam L. Houston ◽  
Suzanne Weaver Smith
Keyword(s):  
Surface Layer ◽  
Unmanned Aerial Vehicles ◽  
Solar Eclipse ◽  
Atmospheric Surface Layer ◽  
Small Scale ◽  
Stable Layer ◽  
Holistic View ◽  
Near Surface ◽  
Aerial Vehicles ◽  
The Impact

We use unmanned aerial vehicles to interrogate the surface layer processes during a solar eclipse and gain a comprehensive look at the changes made to the atmospheric surface layer as a result of the rapid change of insolation. Measurements of the atmospheric surface layer structure made by the unmanned systems are connected to surface measurements to provide a holistic view of the impact of the eclipse on the near-surface behaviour, large-scale turbulent structures and small-scale turbulent dynamics. Different regimes of atmospheric surface layer behaviour were identified, with the most significant impact including the formation of a stable layer just after totality and evidence of Kelvin–Helmholtz waves appearing at the interface between this layer and the residual layer forming above it. The decrease in surface heating caused a commensurate decrease in buoyant turbulent production, which resulted in a rapid decay of the turbulence in the atmospheric surface layer both within the stable layer and in the mixed layer forming above it. Significant changes in the wind direction were imposed by the decrease in insolation, with evidence supporting the formation of a nocturnal jet, as well as backing of the wind vector within the stable layer.

scholarly journals High-Resolution Numerical Modelling of Near-Surface Atmospheric Fields in the Complex Terrain of James Ross Island, Antarctic Peninsula

Atmosphere ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 360
Author(s):  
Michael Matějka ◽  
Kamil Láska ◽  
Klára Jeklová ◽  
Jiří Hošek
Keyword(s):  
Wind Speed ◽  
Air Temperature ◽  
Antarctic Peninsula ◽  
Wind Direction ◽  
Wrf Model ◽  
Lower Altitude ◽  
Near Surface ◽  
James Ross Island ◽  
The Antarctic ◽  
The Impact

The Antarctic Peninsula belongs to the regions of the Earth that have seen the highest increase in air temperature in the past few decades. The warming is reflected in degradation of the cryospheric system. The impact of climate variability and interactions between the atmosphere and the cryosphere can be studied using numerical atmospheric models. In this study, the standard version of the Weather Research and Forecasting (WRF) model was validated on James Ross Island in the northern part of the Antarctic Peninsula. The aim of this study was to verify the WRF model output at 700 m horizontal resolution using air temperature, wind speed and wind direction observations from automatic weather stations on the Ulu Peninsula, the northernmost part of James Ross Island. Validation was carried out for two contrasting periods (summer and winter) in 2019/2020 to assess possible seasonal effects on model accuracy. Simulated air temperatures were in very good agreement with measurements (mean bias −1.7 °C to 1.4 °C). The exception was a strong air temperature inversion during two of the winter days when a significant positive bias occurred at the coastal and lower-altitude locations on the Ulu Peninsula. Further analysis of the WRF estimates showed a good skill in simulating near-surface wind speed with higher correlation coefficients in winter (0.81–0.93) than in summer (0.41–0.59). However, bias and RMSE for wind speed tended to be better in summer. The performance of three WRF boundary layer schemes (MYJ, MYNN, QNSE) was further evaluated. The QNSE scheme was generally more accurate than MYNN and MYJ, but the differences were quite small and varied with time and place. The MYNN and QNSE schemes tended to achieve better wind speed simulation quality than the MYJ scheme. The model successfully captured wind direction, showing only slight differences to the observed values. It was shown that at lower altitudes the performance of the model can vary greatly with time. The model results were more accurate during high wind speed southwestern flow, while the accuracy decreased under weak synoptic-scale forcing, accompanied by an occurrence of mesoscale atmospheric processes.

scholarly journals Evidence for elevation-dependent warming from the Chinese Tianshan Mountains

2020 ◽  
Author(s):  
Lu Gao ◽  
Haijun Deng ◽  
Xiangyong Lei ◽  
Jianhui Wei ◽  
Yaning Chen ◽  
...  
Keyword(s):  
Time Scales ◽  
Air Temperature ◽  
Tianshan Mountains ◽  
Swiss Alps ◽  
Maximum Temperature ◽  
High Mountains ◽  
Chinese Tianshan Mountains ◽  
Chinese Tianshan ◽  
Warming Rate ◽  
Different Time Scales

Abstract. The phenomenon that the warming rate of air temperature is amplified with elevation is termed elevation-dependent warming (EDW). It has been clarified that EDW can accelerate the retreat of glaciers and the melting of snow, which would have significant impacts on regional ecological environment. Owing to the lack of high-density ground observations in the high mountains, there is a widespread controversy on the existence of the EDW. Current evidences are mainly derived from some typical high mountains such as the Swiss Alps, the Colorado Rocky Mountains, the Tropical Andes and the Tibetan Plateau/Himalayas. Rare evidences in other mountains have been reported, especially in arid regions. In this study, EDW features in the Chinese Tianshan Mountains (CTM) are detected using a unique high-resolution (1 km, 6-hourly) air temperature data set (CTMD). The results showed that there are significant EDW signals at different altitudes on different time scales. The warming rate of the minimum temperature in winter shows significant elevation dependence, especially above 4000 m. The greatest altitudinal gradient in the warming rate of maximum temperature is found above 2500 m in April. For the mean temperature, the warming rates in January, February and March show prominent EDW features but with different significances. Within the CTM, the Tolm Mountains, the eastern part of the Borokoonu Mountains, the Bogda Mountains and the Balikun Mountains are the representative regions that show significant EDW features on different time scales. This new evidence partly explains the accelerated melting of glaciers in spring in the CTM.

Seasonal and Synoptic Variations in Near-Surface Air Temperature Lapse Rates in a Mountainous Basin

2008 ◽  
Vol 47 (1) ◽  
pp. 249-261 ◽  
Author(s):  
Troy R. Blandford ◽  
Karen S. Humes ◽  
Brian J. Harshburger ◽  
Brandon C. Moore ◽  
Von P. Walden ◽  
...  
Keyword(s):  
Air Temperature ◽  
Surface Air Temperature ◽  
Lapse Rate ◽  
Maximum Temperature ◽  
Weather Types ◽  
Near Surface ◽  
Air Masses ◽  
Synoptic Weather ◽  
South Central ◽  
Lapse Rates

Abstract To accurately estimate near-surface (2 m) air temperatures in a mountainous region for hydrologic prediction models and other investigations of environmental processes, the authors evaluated daily and seasonal variations (with the consideration of different weather types) of surface air temperature lapse rates at a spatial scale of 10 000 km2 in south-central Idaho. Near-surface air temperature data (Tmax, Tmin, and Tavg) from 14 meteorological stations were used to compute daily lapse rates from January 1989 to December 2004 for a medium-elevation study area in south-central Idaho. Daily lapse rates were grouped by month, synoptic weather type, and a combination of both (seasonal–synoptic). Daily air temperature lapse rates show high variability at both daily and seasonal time scales. Daily Tmax lapse rates show a distinct seasonal trend, with steeper lapse rates (greater decrease in temperature with height) occurring in summer and shallower rates (lesser decrease in temperature with height) occurring in winter. Daily Tmin and Tavg lapse rates are more variable and tend to be steepest in spring and shallowest in midsummer. Different synoptic weather types also influence lapse rates, although differences are tenuous. In general, warmer air masses tend to be associated with steeper lapse rates for maximum temperature, and drier air masses have shallower lapse rates for minimum temperature. The largest diurnal range is produced by dry tropical conditions (clear skies, high solar input). Cross-validation results indicate that the commonly used environmental lapse rate [typically assumed to be −0.65°C (100 m)−1] is solely applicable to maximum temperature and often grossly overestimates Tmin and Tavg lapse rates. Regional lapse rates perform better than the environmental lapse rate for Tmin and Tavg, although for some months rates can be predicted more accurately by using monthly lapse rates. Lapse rates computed for different months, synoptic types, and seasonal–synoptic categories all perform similarly. Therefore, the use of monthly lapse rates is recommended as a practical combination of effective performance and ease of implementation.

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