Abstract A two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea. The domain includes a representation of part of Borneo as well as the sea so that the model can simulate the initiation of convection. Also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle. This allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck, which typically occupies several hundred kilometers of the domain. Frank and Cohen's cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area. The major conclusions are: Ice phase processes are important in determining the level of maximum large-scale heating and vertical motion because there is a strong anvil componen...

Numerical study of convection observed during the Winter Monsoon Experiment using a mesoscale two-dimensional model [presentation]

This overview compiles the actual knowledge of the biogenic emissions of some volatile organic compounds (VOCs), i.e., isoprene, terpenes, alkanes, alkenes, alcohols, esters, carbonyls, and acids. We discuss VOC biosynthesis, emission inventories, relations between emission and plant physiology as well as temperature and radiation, and ecophysiological functions. For isoprene and monoterpenes, an extended summary of standard emission factors, with data related to the plant genus and species, is included. The data compilation shows that we have quite a substantial knowledge of the emission of isoprene and monoterpenes, including emission rates, emission regulation, and biosynthesis. The situation is worse in the case of numerous other compounds (other VOCs or OVOCs) being emitted by the biosphere. This is reflected in the insufficient knowledge of emission rates and biological functions. Except for the terpenoids, only a limited number of studies of OVOCs are available; data are summarized for alkanes, alkenes, carbonyls, alcohols, acids, and esters. In addition to closing these gaps of knowledge, one of the major objectives for future VOC research is improving our knowledge of the fate of organic carbon in the atmosphere, ending up in oxidation products and/or as aerosol particles.

Biogenic Volatile Organic Compounds (VOC): An Overview on Emission, Physiology and Ecology

Reactions on mineral dust.

https://escholarship.org/content/qt8mf445sh/qt8mf445sh.pdf?t=nu02or

Atmospheric composition change – global and regional air quality

Secondary organic aerosol formation in cloud and fog droplets: a literature evaluation of plausibility

Temporal variations in formaldehyde, acetaldehyde and acetone and budget of formaldehyde at a rural site in Southern Germany

FTIR spectroscopic measurements of surface bond products of nitrogen oxides on aerosol surfaces : implications for heterogeneous HNO2 production

Young, clonal Norway spruce trees (Picea abies L.) were exposed for 2 years at high altitudes to ambient atmospheric concentrations of photooxidants containing hydroxymethyl hydroperoxide (HMHP) as an important constituent. In spruce needles from a site with higher concentrations of organic peroxides in air, the apoplastic peroxidase activities were significantly lower than in needles exposed to lower organic peroxide concentrations. Guaiacol peroxidase activities in total needle extracts were not affected. In vitro HMHP at a concentration of 35 [mu]M inhibited apoplastic and total needle guaiacol peroxidase activities by 50% at pH 5.25. At the same pH, ascorbate-specific peroxidase activity required about 100 [mu]M HMHP for 50% inhibition. At pH 7, 1.46 mM HMHP caused a 50% reduction in guaiacol peroxidase and a 13% reduction in ascorbate peroxidase activity. The present results suggest that HMHP in ambient air may affect peroxidase activity in spruce needles. Peroxidases located in the relatively acidic aqueous phase of the cell walls appear to be more susceptible to HMHP inhibition than those present in neutral or slightly alkaline symplastic compartments of cells such as the cytosol or chloroplasts.

Inhibition of Apoplastic and Symplastic Peroxidase Activity from Norway Spruce by the Photooxidant Hydroxymethyl Hydroperoxide

Assessing the meteorological conditions of a deep Italian Alpine valley system by means of a measuring campaign and simulations with two models during a summer smog episode

H 2 O 2 has two faces in plants: it is toxic at low concentrations in the chloroplasts, and it is a necessary cosubstrate for the production of biopolymers in the apoplastic compartment. Plants have evolved an antioxidant system that enables them to cope with high intrinsic production rates of H 2 O 2 . Measurements of H 2 O 2 in air at a rural, forested site were used to calculate the influx of atmospheric H 2 O 2 into spruce needles. The estimated uptake rates were compared with the capacity of protective systems present in the aqueous matrix of the cell wall and inside the cells in the symplastic space. Evidence is presented that the rate of H 2 O 2 detoxification exceeds its uptake up to 10 6 -fold (...)

Wolfgang Junkermann

Papers

Temporal variations in formaldehyde, acetaldehyde and acetone and budget of formaldehyde at a rural site in Southern Germany

FTIR spectroscopic measurements of surface bond products of nitrogen oxides on aerosol surfaces : implications for heterogeneous HNO2 production

Inhibition of Apoplastic and Symplastic Peroxidase Activity from Norway Spruce by the Photooxidant Hydroxymethyl Hydroperoxide

Assessing the meteorological conditions of a deep Italian Alpine valley system by means of a measuring campaign and simulations with two models during a summer smog episode

Does atmospheric hydrogen peroxide contribute to damage to forest trees