Seasonal changes in the vertical distribution of dust in the lower troposphere

1970 ◽  
Vol 75 (12) ◽  
pp. 2179-2184 ◽  
Author(s):  
Sherwood B. Idso ◽  
Paul C. Kangieser
Keyword(s):  
Vertical Distribution ◽  
Seasonal Changes ◽  
Lower Troposphere ◽  
The Vertical Distribution

scholarly journals Multi-model study of mercury dispersion in the atmosphere: Vertical distribution of mercury species

2016 ◽  
Author(s):  
Johannes Bieser ◽  
Franz Slemr ◽  
Jesse Ambrose ◽  
Carl Brenninkmeijer ◽  
Steve Brooks ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Atmospheric Chemistry ◽  
Lower Troposphere ◽  
Elemental Mercury ◽  
Mercury Species ◽  
Substantial Impact ◽  
Model Studies ◽  
Model Study ◽  
The Impact ◽  
The Vertical Distribution

Abstract. Atmospheric chemistry and transport of mercury play a key role in the global mercury cycle. However, there are still considerable knowledge gaps concerning the fate of mercury in the atmosphere. This is the second part of a model inter-comparison study investigating the impact of atmospheric chemistry and emissions on mercury in the atmosphere. While the first study focused on ground based observations of mercury concentration and deposition, here we investigate the vertical distribution and speciation of mercury from the planetary boundary layer to the lower stratosphere. So far, there have been few model studies investigating the vertical distribution of mercury, mostly focusing on single aircraft campaigns. Here, we present a first comprehensive analysis based on various aircraft observations in Europe, North America, and on inter-continental flights. The investigated models proved to be able to reproduce the distribution of total and elemental mercury concentrations in the troposphere including inter-hemispheric trends. One key aspect of the study is the investigation of mercury oxidation in the troposphere. We found that different chemistry schemes were better at reproducing observed oxidized mercury (RM) patterns depending on altitude. High RM concentrations in the upper troposphere could be reproduced with oxidation by bromine while elevated concentrations in the lower troposphere were better reproduced by OH and ozone chemistry. However, the results were not always conclusive as the physical and chemical parametrizations in the chemistry transport models also proved to have a substantial impact on model results.

Vertical distribution of pelagial zooplankton in a middle-sized dimictic valley reservoir

Biologia ◽  
2006 ◽  
Vol 61 (2) ◽  
Author(s):  
Martina Hudcovicová ◽  
Marian Vranovsky
Keyword(s):  
Vertical Distribution ◽  
Water Column ◽  
Seasonal Changes ◽  
Thermal Gradient ◽  
Summer Temperature ◽  
Zooplankton Abundance ◽  
Invertebrate Predation ◽  
Chaoborus Flavicans ◽  
Daphnia Cucullata ◽  
The Vertical Distribution

AbstractOur observations indicate the vertical distribution of zooplankton and its seasonal changes in Dubník II reservoir (Slovakia) are determined mainly by the thermal regime of the reservoir, by transparency, and by fish and invertebrate predation. During periods of circulation, zooplankton vertical distribution in the whole water column was more homogeneous, whilst during summer temperature stratification zooplankton concentrated in the epilimnion — rotifers in higher layers than crustaceans. During summer stagnation a steep thermal gradient occurred at the boundary of the epi-and hypolimnion and low temperature and low dissolved oxygen in hypolimnion offered a refuge for Chaoborus flavicans larvae against fish, enabling coexistence of vertebrate and invertebrate predation. This evidence supports our previous findings concerning dominance of rotifers in zooplankton and representation of crustaceans by small-bodied species in the study reservoir. Steep thermal gradient and the presence of Chaoborus larvae caused very low zooplankton abundance in the lower part of the water column and a reduction of cladocerans refuges against fish to layers of thermocline or closely under thermocline where Daphnia cucullata and Daphnia parvula were found. Our previous assumptions about the high density of zooplanktivorous fish in Dubník II reservoir are supported by the fact that these small cladocerans are represented by smaller individuals in the upper layers and bigger individuals in deeper layers.

Vertical Distribution of Xiphinemabakeri Nematodes in Soil in a Douglas-fir Nursery

1974 ◽  
Vol 4 (2) ◽  
pp. 175-178
Author(s):  
Jack R. Sutherland
Keyword(s):  
Moisture Content ◽  
Vertical Distribution ◽  
Distribution Pattern ◽  
Seasonal Changes ◽  
Root Distribution ◽  
Pore Space ◽  
Douglas Fir ◽  
Soil Samples ◽  
Nematode Control ◽  
The Vertical Distribution

Soil samples were collected throughout the year to determine the vertical distribution of Xiphinemabakeri nematodes in soil in a Douglas-fir [Pseudotsugamenziesii (Mirb.) Franco] nursery and to monitor seasonal changes in nematode distribution pattern. Root distribution, moisture content, available pore space, and osmotic pressure were also determined for soil samples taken at various depths to see if they were related to nematode distribution. More than 90% of the nematodes were present in the upper 20 cm of soil, especially from 0 to 10 cm, and this percentage did not change with season. Nematode distribution was related only to root distribution. The significance of the results for nematode control practices is discussed.

scholarly journals Dependence of the vertical distribution of bromine monoxide in the lower troposphere on meteorological factors such as wind speed and stability

2015 ◽  
Vol 15 (4) ◽  
pp. 2119-2137 ◽  
Author(s):  
P. K. Peterson ◽  
W. R. Simpson ◽  
K. A. Pratt ◽  
P. B. Shepson ◽  
U. Frieß ◽  
...  
Keyword(s):  
Wind Speed ◽  
Vertical Distribution ◽  
Degrees Of Freedom ◽  
Atmospheric Stability ◽  
Lower Troposphere ◽  
Optimal Estimation ◽  
Vertical Column ◽  
Vertical Column Density ◽  
Halogen Activation ◽  
The Vertical Distribution

Abstract. Multiple axis differential absorption spectroscopy (MAX-DOAS) measurements of bromine monoxide (BrO) probed the vertical structure of halogen activation events during March–May 2012 at Barrow, Alaska. An analysis of the BrO averaging kernels and degrees of freedom obtained by optimal-estimation-based inversions from raw MAX-DOAS measurements reveals the information is best represented by reducing the retrieved BrO profile to two quantities: the integrated column from the surface through 200 m (VCD200 m), and the lower tropospheric vertical column density (LT-VCD), which represents the integrated column of BrO from the surface through 2 km. The percentage of lower tropospheric BrO in the lowest 200 m was found to be highly variable ranging from shallow layer events, where BrO is present primarily in the lowest 200 m, to distributed column events where BrO is observed at higher altitudes. The highest observed LT-VCD events occurred when BrO was distributed throughout the lower troposphere, rather than concentrated near the surface. Atmospheric stability in the lowest 200 m influenced the percentage of LT-VCD that is in the lowest 200 m, with inverted temperature structures having a first-to-third quartile range (Q1–Q3) of VCD200 m/LT-VCD from 15–39%, while near-neutral-temperature structures had a Q1–Q3 range of 7–13%. Data from this campaign show no clear influence of wind speed on either lower tropospheric bromine activation (LT-VCD) or the vertical distribution of BrO, while examination of seasonal trends and the temperature dependence of the vertical distribution supported the conclusion that the atmospheric stability affects the vertical distribution of BrO.

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