A striped pattern of snowfall and snow cover

1993 ◽  
Vol 18 ◽  
pp. 27-32
Author(s):  
Yasuaki Nohguchi ◽  
Takashi Ikarashi ◽  
Osamu Abe ◽  
Atsushi Sato

A striped pattern can be seen by spraying ink on a vertical wall of a snow pit to observe the layered structure of a snow cover. This pattern is caused by variations of snowfall in time, particularly pauses in snowfall, and its structure is related to a kind of fractal. In this paper, we consider snowfall and snow cover from a viewpoint of fractals and show that the layered structure of snow cover is a record of fractals on atmospheric-turbulence phenomena through the time variation of snowfall.

1993 ◽  
Vol 18 ◽  
pp. 27-32
Author(s):  
Yasuaki Nohguchi ◽  
Takashi Ikarashi ◽  
Osamu Abe ◽  
Atsushi Sato

A striped pattern can be seen by spraying ink on a vertical wall of a snow pit to observe the layered structure of a snow cover. This pattern is caused by variations of snowfall in time, particularly pauses in snowfall, and its structure is related to a kind of fractal. In this paper, we consider snowfall and snow cover from a viewpoint of fractals and show that the layered structure of snow cover is a record of fractals on atmospheric-turbulence phenomena through the time variation of snowfall.


Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 285
Author(s):  
Marcus Bursik ◽  
Qingyuan Yang ◽  
Adele Bear-Crozier ◽  
Michael Pavolonis ◽  
Andrew Tupper

Volcanic ash clouds often become multilayered and thin with distance from the vent. We explore one mechanism for the development of this layered structure. We review data on the characteristics of turbulence layering in the free atmosphere, as well as examples of observations of layered clouds both near-vent and distally. We then explore dispersion models that explicitly use the observed layered structure of atmospheric turbulence. The results suggest that the alternation of turbulent and quiescent atmospheric layers provides one mechanism for the development of multilayered ash clouds by modulating vertical particle motion. The largest particles, generally μ>100 μm, are little affected by turbulence. For particles in which both settling and turbulent diffusion are important to vertical motion, mostly in the range of 10–100 μμm, the greater turbulence intensity and more rapid turbulent diffusion in some layers causes these particles to spend greater time in the more turbulent layers, leading to a layering of concentration. The results may have important implications for ash cloud forecasting and aviation safety.


Author(s):  
Tai D. Nguyen ◽  
Ronald Gronsky ◽  
Jeffrey B. Kortright

Nanometer period Ru/C multilayers are one of the prime candidates for normal incident reflecting mirrors at wavelengths < 10 nm. Superior performance, which requires uniform layers and smooth interfaces, and high stability of the layered structure under thermal loadings are some of the demands in practical applications. Previous studies however show that the Ru layers in the 2 nm period Ru/C multilayer agglomerate upon moderate annealing, and the layered structure is no longer retained. This agglomeration and crystallization of the Ru layers upon annealing to form almost spherical crystallites is a result of the reduction of surface or interfacial energy from die amorphous high energy non-equilibrium state of the as-prepared sample dirough diffusive arrangements of the atoms. Proposed models for mechanism of thin film agglomeration include one analogous to Rayleigh instability, and grain boundary grooving in polycrystalline films. These models however are not necessarily appropriate to explain for the agglomeration in the sub-nanometer amorphous Ru layers in Ru/C multilayers. The Ru-C phase diagram shows a wide miscible gap, which indicates the preference of phase separation between these two materials and provides an additional driving force for agglomeration. In this paper, we study the evolution of the microstructures and layered structure via in-situ Transmission Electron Microscopy (TEM), and attempt to determine the order of occurence of agglomeration and crystallization in the Ru layers by observing the diffraction patterns.


2019 ◽  
Author(s):  
V.B. Kalmanova

В статье представлены результаты исследования экологогеохимического состояния снежного покрова как индикатора качества атмосферного воздуха г. Биробиджана. Выявлены основные природные и антропогенные факторы, предопределяющие экологическое состояние городской территории в зимний период (климатические, планировочная структура, стационарные и мобильные источники загрязнения). Определено, что выбросы основных загрязнителей во время отопительного сезона превышает летний в 6,5 раз. Проведены геохимические исследования снежного покрова на 60 экспериментальных площадках, заложенных в различных функциональных зонах города. Выявлено значительное превышение тяжелых металлов над фоновым уровнем: железа до 60, марганца до 50, меди до 40, цинка до 20, никеля до 12, свинца до 10, кобальта до 6 раз. С 2003 по 2018 годы содержание химических элементов в снеге увеличилось в 2 раза за счет мобильных источников загрязнения, ТЭЦ, котельных. Проведена сравнительная характеристика накопления тяжелых металлов в снеге за 2003 и 2018 годы и установлен ранжированный ряд загрязняющих токсичных веществ. Разработана шкала оценки загрязнения депонирующих сред по суммарному показателю концентрации тяжелых металлов, согласно которой в Биробиджане выявлено 5 уровней загрязнения снежного покрова. В целом экологическое состояние урбанизированной территории признано неудовлетворительным (8 площади территории относится к очень высокому, 14 к высокому, 21 к выше среднему, 27 к среднему уровням загрязнения, 30 к относительно чистым районам города). По полученным результатам разработана карта в программе ArcView GIS Экологогеохимическое районирование территории г. Биробиджана по уровню загрязнения снежного покрова с выделением наиболее загрязненных участков (70 от общей площади города является загрязненной). По результатам проведенных исследований предложены конструктивные методы планирования урбанизированной территории с целью улучшения ее экологического состояния: проведение геомониторинга (контроль загрязнения снежного покрова и своевременный его вывоз на специально оборудованные полигоны). Snow cover is taken as an indicator of air quality using Birobidzhan, a middlesize city in the Russian Far East, as a case study. The main natural and manmade determinants influencing the ecological state of the urban area in winter are identified: climate, a planning structure, and the stationary and mobile sources of pollution. During the heating season the emission of major pollutants exceeds the summer level by 6.5 times. The geochemical study of snow cover was performed at 60 experimental sites in different functional urban areas. A significant excess of heavy metals over the regional background level was revealed: iron up to 60 times, manganese up to 50, copper up to 40, zinc up to 20 , nickel up to 12, lead up to 10, cobalt up to 6 times. From 2003 to 2018 the content of chemical elements in snow increased in 2 times due to the mobile sources of pollution, thermal power plants, and boilers. The comparative characteristic of accumulation of heavy metals in snow for 2003 and 2018 is carried out, and the ranked number of polluting toxic substances is established. The scale of pollution assessment in depositing environments was developed using the cumulative indicator of heavy metal concentration. Five levels of snow cover pollution are found in Birobidzhan: low, moderate, above moderate, high and very high. As a whole, the ecological state of the urban area is considered as unsatisfactory (8 of the area with a very high level of pollution, 14 with high, 21 above moderate, 27 a moderate level of pollution, 30 a relatively clean area). According to the results, a map was developed in the ArcView GIS program Ecological and geochemical zoning of Birobidzhan, using the level of the snow cover pollution with the allocation of the most polluted areas (70 of the total area of the city is polluted). According to the results, a constructive method of planning in an urban area is proposed in order to improve its environmental condition: geomonitoring as a control of pollution in snow cover and its prompt removal to specially equipped landfills.


1998 ◽  
Vol 4 (2-3) ◽  
pp. 27-33
Author(s):  
V.B. Efimov ◽  
I.A. Kalmykov ◽  
S.E. Yatsevich

Author(s):  
Takaaki OKUMURA ◽  
Atsushi KUROKAWA ◽  
Hiroo MASUDA ◽  
Toshiki KANAMOTO ◽  
Masanori HASHIMOTO ◽  
...  

Author(s):  
Yagya Dutta Dwivedi ◽  
Vasishta Bhargava Nukala ◽  
Satya Prasad Maddula ◽  
Kiran Nair

Abstract Atmospheric turbulence is an unsteady phenomenon found in nature and plays significance role in predicting natural events and life prediction of structures. In this work, turbulence in surface boundary layer has been studied through empirical methods. Computer simulation of Von Karman, Kaimal methods were evaluated for different surface roughness and for low (1%), medium (10%) and high (50%) turbulence intensities. Instantaneous values of one minute time series for longitudinal turbulent wind at mean wind speed of 12 m/s using both spectra showed strong correlation in validation trends. Influence of integral length scales on turbulence kinetic energy production at different heights is illustrated. Time series for mean wind speed of 12 m/s with surface roughness value of 0.05 m have shown that variance for longitudinal, lateral and vertical velocity components were different and found to be anisotropic. Wind speed power spectral density from Davenport and Simiu profiles have also been calculated at surface roughness of 0.05 m and compared with k−1 and k−3 slopes for Kolmogorov k−5/3 law in inertial sub-range and k−7 in viscous dissipation range. At high frequencies, logarithmic slope of Kolmogorov −5/3rd law agreed well with Davenport, Harris, Simiu and Solari spectra than at low frequencies.


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