The Chemical Weather

2005 ◽  
Vol 2 (1) ◽  
pp. 6 ◽  
Author(s):  
Mark G. Lawrence ◽  
Øystein Hov ◽  
Matthias Beekmann ◽  
Jørgen Brandt ◽  
Hendrik Elbern ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Atmospheric Chemistry ◽  
Wind Direction ◽  
Strong Influence ◽  
Trace Gases ◽  
Short Term ◽  
Chemical Complexity ◽  
Chemical Climate ◽  
Short Term Variability

Environmental Context. Meteorological weather—temperature, pressure, wind direction—is familiar to all, and contrasts with meteorological climate in short-term (weather) versus long-term (climate) influence. From the atmospheric chemistry side, the focus has largely been on the chemical climate, the long-term mean concentrations of important trace gases and aerosols. An emerging new focus of study is the chemical weather—the tremendous short-term variability of the atmospheric chemical composition, resulting from the strong influence of meteorological variability, chemical complexity, and regionally and temporally varying emissions.

scholarly journals Technical note: A new comprehensive SCAVenging submodel for global atmospheric chemistry modelling

2006 ◽  
Vol 6 (3) ◽  
pp. 565-574 ◽  
Author(s):  
H. Tost ◽  
P. Jöckel ◽  
A. Kerkweg ◽  
R. Sander ◽  
J. Lelieveld
Keyword(s):  
Chemical Composition ◽  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Aerosol Particles ◽  
Trace Gases ◽  
Precipitation Chemistry ◽  
Technical Note ◽  
Transport Processes ◽  
New Method

Abstract. We present the new scavenging scheme SCAV, simulating the removal of trace gases and aerosol particles by clouds and precipitation in global atmospheric chemistry models. The scheme is quite flexible and can be used for various purposes, e.g. long term chemistry simulations as well as detailed cloud and precipitation chemistry calculations. The presence of clouds can substantially change the chemical composition of the atmosphere. We present a new method of mechanistically coupling gas phase, aerosol, cloud and precipitation chemistry, which enables studies of feedbacks between multiphase chemistry and transport processes.

scholarly journals Technical note: A new comprehensive SCAVenging submodel for global atmospheric chemistry modelling

2005 ◽  
Vol 5 (6) ◽  
pp. 11157-11181 ◽  
Author(s):  
H. Tost ◽  
P. Jöckel ◽  
A. Kerkweg ◽  
R. Sander ◽  
J. Lelieveld
Keyword(s):  
Chemical Composition ◽  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Aerosol Particles ◽  
Trace Gases ◽  
Precipitation Chemistry ◽  
Technical Note ◽  
Transport Processes ◽  
New Method

Abstract. We present the new scavenging scheme SCAV, simulating the removal of trace gases and aerosol particles by clouds and precipitation in global atmospheric chemistry models. The scheme is quite flexible and can be used for various purposes, e.g. long term chemistry simulations as well as detailed cloud and precipitation chemistry calculations. The presence of clouds can substantially change the chemical composition of the atmosphere. We present a new method of mechanistically coupling gas phase, aerosol, cloud and precipitation chemistry, which enables studies of feedbacks between multiphase chemistry and transport processes.

scholarly journals Fetal Vibroacoustic Stimulation in Computerized Cardiotocographic Analysis: The Role of Short-Term Variability and Approximate Entropy

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Maria Laura Annunziata ◽  
Mariamaddalena Scala ◽  
Natascia Giuliano ◽  
Salvatore Tagliaferri ◽  
Olga Carmela Maria Imperato ◽  
...  
Keyword(s):  
High Risk ◽  
Perinatal Outcomes ◽  
Approximate Entropy ◽  
Computer Assisted ◽  
Short Term ◽  
Fetal Movements ◽  
The Impact ◽  
Short Term Variability

The aim of this study was to evaluate the impact of vibroacoustic stimulation (VAS) on computerized cardiotocography short-term variability (STV) and approximate entropy (ApEn) in both low- and high-risk pregnancies. VAS was performed on 121 high- and 95 low-risk pregnancies after 10 minutes of continuous quiet, while their FHR parameters were monitored and recorded by cCTG analysis. Fetal heart rate was recorded using a computer-assisted equipment. Baseline FHR, accelerations, decelerations, STV, long-term irregularity (LTI), ApEn, and fetal movements (FMs) were calculated for defined observational periods before VAS and after 10 minutes. Data were also investigated in relationship with the perinatal outcome. In each group of patients, FHR after VAS remained almost unmodified. Fetal movements significantly increased after VAS in both groups. Results show that only in the high-risk pregnancies, the increase of STV and the decrease of ApEn after VAS were significantly associated with favorable perinatal outcomes.

scholarly journals Modelling large timescale and small timescale service variability

2019 ◽  
Vol 293 (1) ◽  
pp. 123-140
Author(s):  
Marco Gribaudo ◽  
Illés Horváth ◽  
Daniele Manini ◽  
Miklós Telek
Keyword(s):  
Service Time ◽  
Large Scale ◽  
Service Time Distribution ◽  
Efficient Computation ◽  
Short Term ◽  
Service Unit ◽  
Long Term Effect ◽  
Short And Long Term ◽  
Short Term Variability

Abstract The performance of service units may depend on various randomly changing environmental effects. It is quite often the case that these effects vary on different timescales. In this paper, we consider small and large scale (short and long term) service variability, where the short term variability affects the instantaneous service speed of the service unit and a modulating background Markov chain characterizes the long term effect. The main modelling challenge in this work is that the considered small and long term variation results in randomness along different axes: short term variability along the time axis and long term variability along the work axis. We present a simulation approach and an explicit analytic formula for the service time distribution in the double transform domain that allows for the efficient computation of service time moments. Finally, we compare the simulation results with analytic ones.

scholarly journals Ratios among atmospheric trace gases together with winds imply exploitable information for bird navigation: a model elucidating experimental results

2013 ◽  
Vol 10 (11) ◽  
pp. 6929-6943 ◽  
Author(s):  
H. G. Wallraff
Keyword(s):  
Atmospheric Chemistry ◽  
Wind Direction ◽  
Spatial Information ◽  
Trace Gases ◽  
Atmospheric Trace Gases ◽  
Spatial Gradients ◽  
Home Site ◽  
Environmental Air ◽  
The Individual ◽  
At Home

Abstract. A model of avian goal-oriented navigation is described that is based on two empirical findings building a bridge from ornithology to atmospheric chemistry. (1) To orient their courses homeward from distant unfamiliar areas, homing pigeons require long-term exposure to undisturbed winds at the home site and olfactory access to the environmental air at home and abroad. (2) Above Germany, ratios among some atmospheric trace gases vary along differently oriented spatial gradients as well as depending on wind direction. The model emulates finding (1) by utilising the analysed air samples on which finding (2) is based. Starting with an available set of 46 omnipresent compounds, virtual pigeons determine the profile of relative weights among them at each of 96 sites regularly distributed around a central home site within a radius of 200 km and compare this profile with corresponding profiles determined at home under varying wind conditions. Referring to particular similarities and dissimilarities depending on home-wind direction, they try to estimate, at each site, the compass direction they should fly in order to approach home. To make the model work, an iterative algorithm imitates evolution by modifying sensitivity to the individual compounds stepwise at random. In the course of thousands of trial-and-error steps it gradually improves homeward orientation by selecting smaller sets of most useful and optimally weighted substances from whose proportional configurations at home and abroad it finally derives navigational performances similar to those accomplished by real pigeons. It is concluded that the dynamic chemical atmosphere most likely contains sufficient spatial information for home-finding over hundreds of kilometres of unfamiliar terrain. The underlying chemo-atmospheric processes remain to be clarified.

Air Chemistry

1959 ◽  
Vol 40 (10) ◽  
pp. 493-498 ◽  
Author(s):  
Christian E. Junge
Keyword(s):  
Atmospheric Chemistry ◽  
Aerosol Particles ◽  
Trace Gases ◽  
Special Importance ◽  
Physical Processes ◽  
Industrial Activities ◽  
Cent Increase ◽  
Air Chemistry

The field of atmospheric chemistry, which is defined as the chemistry of trace substances in the troposphere, is reviewed. Trace substances can be present as aerosols or as gases. Major sources of aerosols are the ocean and industrial activities. The chemical composition of the aerosol particles is not only determined by their source but also by various processes in the atmosphere—notably, reactions with gas traces. Only little is known about trace gases like SO2, H2S, NH3 or NO2. Of special importance for meteorology is CO2 and its long-term fluctuations. The facts and possible reasons for its 10 per cent increase during this century are discussed. The last part of the discussion is concerned with the physical processes by which the trace substances are removed from the atmosphere, primarily the role of precipitation.

SPOTing long-term changes in vegetation over short-term variability

2012 ◽  
Vol 28 (1) ◽  
pp. 2-24 ◽  
Author(s):  
Nisha Bao ◽  
Alex Lechner ◽  
Andrew Fletcher ◽  
Peter Erskine ◽  
David Mulligan ◽  
...  
Keyword(s):  
Short Term ◽  
Long Term Changes ◽  
Short Term Variability
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