90 research outputs found

    Variance methods to estimate regional heat fluxes with aircraft measurements in the convective boundary layer

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    Turbulence data obtained by aircraft observations in the convective boundary layer (CBL) were analyzed to estimate the regional surface heat fluxes through application of the variance methods. Several heights within and above the CBL were flown repeatedly above the flux observation site in a homogeneous steppe region in Mongolia. The vertical profiles of the second moment about the mean, i.e., the variance, of temperature were found to follow in general the functional forms proposed in previous studies. These variance statistics were applied to the variance formulations to estimate surface sensible heat fluxes. First, the flux estimation was made with these equations and the constant parameters as proposed in previous studies. Then, the constants were re-calibrated with the current data set and used for flux estimation. In addition, a new simpler formulation was proposed and also calibrated with the current data set. Finally, additional variables, which represent the large scale atmospheric conditions namely baroclinity and advection, were considered for possible improvement of the flux estimation. The resulting rms difference of the estimated sensible heat flux and ground based measurements was reduced from about 40–100 W m−2 for the results obtained with the original constants and formulations, to 30 W m−2 or less for those obtained with locally calibrated constants and introduction of four additional variables. All formulations including the new simple equation performed equally well

    Thermodynamic properties of small flares in the quiet Sun observed by Hα\alpha and EUV: plasma motion of the chromosphere and time evolution of temperature/emission measure

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    Small flares frequently occur in the quiet Sun. Previous studies have noted that they share many common characteristics with typical solar flares in active regions. However, their similarities and differences are not fully understood, especially their thermal properties. In this study, we performed imaging spectroscopic observations in the Hα\alpha line taken with the Solar Dynamics Doppler Imager on the Solar Magnetic Activity Research Telescope (SMART/SDDI) at the Hida Observatory and imaging observations with the Atmospheric Imaging Assembly onboard Solar Dynamics Observatory (SDO/AIA). We analysed 25 cases of small flares in the quiet Sun over the thermal energy range of 10241027erg10^{24}-10^{27}\,\mathrm{erg}, paying particular attention to their thermal properties. Our main results are as follows: (1) We observe a redshift together with line centre brightening in the Hα\alpha line associated with more than half of the small flares. (2) We employ differential emission measure analysis using AIA multi-temperature (channel) observations to obtain the emission measure and temperature of the small flares. The results are consistent with the Shibata & Yokoyama (1999, 2002) scaling law. From the scaling law, we estimated the coronal magnetic field strength of small flares to be 5 --15 G. (3) The temporal evolution of the temperature and the density shows that the temperature peaks precede the density peaks in more than half of the events. These results suggest that chromospheric evaporations/condensations play an essential role in the thermal properties of some of the small flares in the quiet Sun, as does for large flares.Comment: 14 pages, 12 figures, accepted for publication in MNRA

    Unified Relationship between Cold Plasma Ejections and Flare Energies Ranging from Solar Microflares to Giant Stellar Flares

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    We often find spectral signatures of chromospheric cold plasma ejections accompanied by flares in a wide range of spatial scales in the solar and stellar atmospheres. However, the relationship between physical quantities (such as mass, kinetic energy, and velocity) of cold ejecta and flare energy has not been investigated in a unified manner for the entire range of flare energies to date. This study analyzed the spectra of cold plasma ejections associated with small-scale flares and solar flares (energy 10251029erg10^{25}-10^{29}\,\mathrm{erg}) to supply smaller energy samples. We performed Hα\alpha imaging spectroscopy observation by the Solar Dynamics Doppler Imager on the Solar Magnetic Activity Research Telescope (SMART/SDDI). We determined the physical quantities of the ejecta by cloud model fitting to the Hα\alpha spectrum. We determined flare energy by differential emission measure analysis using Atmospheric Imaging Assembly onboard Solar Dynamics Observatory (SDO/AIA) for small-scale flares and by estimating the bolometric energy for large-scale flares. As a result, we found that the ejection mass MM and the total flare energy EtotE_{\mathrm{tot}} follow a relation of MEtot2/3M\propto E_{\mathrm{tot}}^{2/3}. We show that the scaling law derived from a simple physical model explains the solar and stellar observations with a coronal magnetic field strength as a free parameter. We also found that the kinetic energy and velocity of the ejecta correlate with the flare energy. These results suggest a common mechanism driven by magnetic fields to cause cold plasma ejections with flares on the Sun and stars.Comment: 23 pages, 10 figures; accepted for publication in Ap

    地域における減塩活動の展開

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    塩分過剰摂取と高血圧症あるいは心血管疾患との関連性から、減塩活動が行われてきている。本稿では、減塩指向社会について、減塩活動の現状を、特にポピュレーションアプローチの観点から概説した。減塩活動のポピュレーションアプローチに関する研究と実践は、近年、加速しつつある。 その上で、日本の地域レベルでの減塩活動の事例をいくつか紹介し、その現状をまとめた。地域社会の啓発や食環境の整備を、行政、専門家集団、食品関連業界、そして住民などが協同して進めてきている実態が見てとれる。こうした活動の成果も検証されつつある。さらに、減塩活動の展望や地域医療の発展と類似する点についても見解を加えた

    The ABCflux database : Arctic-boreal CO2 flux observations and ancillary information aggregated to monthly time steps across terrestrial ecosystems

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    Past efforts to synthesize and quantify the magnitude and change in carbon dioxide (CO2) fluxes in terrestrial ecosystems across the rapidly warming Arctic-boreal zone (ABZ) have provided valuable information but were limited in their geographical and temporal coverage. Furthermore, these efforts have been based on data aggregated over varying time periods, often with only minimal site ancillary data, thus limiting their potential to be used in large-scale carbon budget assessments. To bridge these gaps, we developed a standardized monthly database of Arctic-boreal CO2 fluxes (ABCflux) that aggregates in situ measurements of terrestrial net ecosystem CO2 exchange and its derived partitioned component fluxes: gross primary productivity and ecosystem respiration. The data span from 1989 to 2020 with over 70 supporting variables that describe key site conditions (e.g., vegetation and disturbance type), micrometeorological and environmental measurements (e.g., air and soil temperatures), and flux measurement techniques. Here, we describe these variables, the spatial and temporal distribution of observations, the main strengths and limitations of the database, and the potential research opportunities it enables. In total, ABCflux includes 244 sites and 6309 monthly observations; 136 sites and 2217 monthly observations represent tundra, and 108 sites and 4092 observations represent the boreal biome. The database includes fluxes estimated with chamber (19 % of the monthly observations), snow diffusion (3 %) and eddy covariance (78 %) techniques. The largest number of observations were collected during the climatological summer (June-August; 32 %), and fewer observations were available for autumn (September-October; 25 %), winter (December-February; 18 %), and spring (March-May; 25 %). ABCflux can be used in a wide array of empirical, remote sensing and modeling studies to improve understanding of the regional and temporal variability in CO2 fluxes and to better estimate the terrestrial ABZ CO2 budget. ABCflux is openly and freely available online (Virkkala et al., 2021b, https://doi.org/10.3334/ORNLDAAC/1934).Peer reviewe

    Author Correction: The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data

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    The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data

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    The FLUXNET2015 dataset provides ecosystem-scale data on CO2, water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-filled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the first time in this paper. In addition, 206 of these sites are for the first time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible.Peer reviewe
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