Search

We present unique observations of a total solar eclipse from a small unmanned aircraft system (sUAS) platform that was operated during the 21 August 2017 North American solar eclipse. The observations were collected near Ten Mile, Tennessee, where eclipse totality lasted 2 min 38 s. A 2-m micrometeorological tripod was erected on-site to measure surface and air temperature, near-surface water vapour, incoming and outgoing shortwave and longwave radiative fluxes, and turbulent fluxes. The sUAS platform and micrometeorological tripod observations indicate significant cooling below a height of 50 m above ground level (a.g.l.) during and shortly after totality. Near-surface temperatures do not return to pre-eclipse values until about 60 min following totality. Above about 50 m a.g.l., smaller temperature changes are observed during the eclipse, as the duration of the eclipse has less influence on deeper boundary-layer turbulence. Additionally, the sensible heat flux becomes slightly negative around totality, and the turbulence kinetic energy and vertical velocity variance concurrently decrease. The evolution of the near-surface meteorological fields are investigated in more detail using a large-eddy simulation (LES) model. The simulations generally reproduce the observations well, in terms of the timing and magnitude of changes in temperature, moisture and sensible and latent heat fluxes. However, the LES model slightly underestimates the diurnal range and decrease in temperature during the eclipse while overestimating the sensible heat fluxes. [ABSTRACT FROM AUTHOR]

In Kochendorfer et al. (Boundary-Layer Meteorol 145:383-398, , hereafter K2012) the vertical wind speed $$(w)$$ measured by a non-orthogonal three-dimensional sonic anemometer was shown to be underestimated by $$\approx $$12 %. Turbulent statistics and eddy-covariance fluxes estimated using $$w$$ were also affected by this underestimate in $$w$$. Methodologies used in K2012 are clarified here in response to Mauder's comment. In addition, further analysis of the K2012 study is presented to help address questions raised in the comment. Specific responses are accompanied with examples of time series, calculated correlation coefficients, and additional explanation of the K2012 methods and assumptions. The discussion and analysis included in the comment and in this response do not affect the validity of the methods or conclusions presented in K2012. [ABSTRACT FROM AUTHOR]

Sonic anemometers are capable of measuring the wind speed in all three dimensions at high frequencies (10-50 Hz), and are relied upon to estimate eddy-covariance-based fluxes of mass and energy over a wide variety of surfaces and ecosystems. In this study, wind-velocity measurement errors from a three-dimensional sonic anemometer with a non-orthogonal transducer orientation were estimated for over 100 combinations of angle-of-attack and wind direction using a novel technique to measure the true angle-of-attack and wind speed within the turbulent atmospheric surface layer. Corrections to the vertical wind speed varied from −5 to 37% for all angles-of-attack and wind directions examined. When applied to eddy-covariance data from three NOAA flux sites, the wind-velocity corrections increased the magnitude of CO fluxes, sensible heat fluxes, and latent heat fluxes by ≈11%, with the actual magnitude of flux corrections dependent upon sonic anemometer, surface type, and scalar. A sonic anemometer that uses vertically aligned transducers to measure the vertical wind speed was also tested at four angles-of-attack, and corrections to the vertical wind speed measured using this anemometer were within ±1% of zero. Sensible heat fluxes over a forest canopy measured using this anemometer were 15% greater than sensible heat fluxes measured using a sonic anemometer with a non-orthogonal transducer orientation. These results indicate that sensors with a non-orthogonal transducer orientation, which includes the majority of the research-grade three-dimensional sonic anemometers currently in use, should be redesigned to minimize sine errors by measuring the vertical wind speed using one pair of vertically aligned transducers. [ABSTRACT FROM AUTHOR]

The high-arctic terrestrial environment is generally recognized as one of the world's most sensitive areas with regard to global warming. In this study, we examined the influence of an isolated warm period on net ecosystem carbon dioxide (CO2) exchange at high latitude during autumn. Using the Free Air Temperature Increase (FATI) technique, we manipulated air, soil, and vegetation temperatures in late August in a tundra site at Zackenberg in the National Park of North and East Greenland (74°N 21°W). The consequences for gross canopy photosynthesis, canopy respiration, and belowground respiration of increasing these temperatures by approximately 2.5°C were determined with closed dynamic CO2 exchange systems. Under current temperatures, the ecosystem acted as a net CO2 source, releasing 19 g CO2-C m−2 over the 14-day study period. Warm soils and senescing vegetation in autumn were unequivocally responsible for this efflux. Heating enhanced CO2 efflux to 29 g CO2-C m−2. This effect was attributed to a 39% increase in belowground respiration, which was the main component of the carbon (C) budget. Gross photosynthesis, on the other hand, was not affected significantly by the simulated warming. Although the aftereffects of an isolated warm period on the C balance in early winter could be significant, simulations with a simple C budget model suggest that soil carbon pools are not affected to a great extent by such a climatic disturbance. The influence on atmospheric carbon, however, appears to be significant. [ABSTRACT FROM AUTHOR]

In this study, we directly measure culture along two of Hofstede's (2980) dimensions, individualism-collectivism and power distance, which we argue are potentially more malleable than stable, at least within the developing nation of interest, Indonesia. We compare these direct measures from Indonesia with those from a developed country, the United States, to gouge the degree to which the culture of this emerging economy remains stable despite strong foreign influences. Utilizing English and back-translated Indonesian language versions of the 2994 Values Survey Module, we find statistically significant support for a narrowing of the differences in these two cultural dimensions between Indonesian and U.S. managers compared to earlier findings by Hofstede (1991). [ABSTRACT FROM AUTHOR]