scholarly journals Maize Pollen Dispersal under Convective Conditions

2008 ◽  
Vol 47 (1) ◽  
pp. 291-307 ◽  
Author(s):  
Matthew T. Boehm ◽  
Donald E. Aylor ◽  
Elson J. Shields
Keyword(s):  
Atmospheric Transport ◽  
Geometric Mean ◽  
Pollen Dispersal ◽  
Gm Crops ◽  
Convective Conditions ◽  
Convective Boundary ◽  
Heavy Particles ◽  
Maize Pollen ◽  
Modified Model ◽  
Pollen Concentrations

Abstract The widespread adoption of genetically modified (GM) crops has led to a need to better understand the atmospheric transport of pollen because of concerns over potential cross-pollination between GM and non-GM crops. Maize pollen concentrations were modeled by a modified Lagrangian stochastic (LS) model of the convective boundary layer (CBL) and were compared with concentrations measured by airborne remotely piloted vehicles (RPVs) flown from directly above to 2 km from source fields. The turbulence parameterization in an existing CBL LS model was modified to incorporate the effects of shear-driven turbulence, which has an especially large impact near the surface, where maize pollen is released. The modified model was used to calculate concentrations corresponding to the RPV flight tracks. For the most convective cases, when at least 95% of the pollen came from sources near the RPV flight track for which source strength measurements are available and the results are less sensitive to uncertainty in wind direction since most of the pollen came from directly beneath the flight track, the geometric mean of the ratio between the modeled and measured concentrations was 0.94. When cases with larger contributions from more distant fields were included, the overall geometric mean decreased to 0.43. The scatter of the measured concentrations about the modeled values followed a lognormal distribution. These results indicate that the modified model presented herein can substantially improve the description of the near-source dispersion of heavy particles released near the surface during convective conditions.

Effective maize pollen dispersal in the field

Euphytica ◽  
1974 ◽  
Vol 23 (1) ◽  
pp. 129-134 ◽  
Author(s):  
E. Paterniani ◽  
A. C. Stort
Keyword(s):  
Pollen Dispersal ◽  
Maize Pollen

A Holocene Ice-Core Pollen Record from Ellesmere Island, Nunavut, Canada

2000 ◽  
Vol 54 (2) ◽  
pp. 275-283 ◽  
Author(s):  
Jocelyne C. Bourgeois ◽  
Roy M. Koerner ◽  
Konrad Gajewski ◽  
David A. Fisher
Keyword(s):  
Atmospheric Transport ◽  
Ice Core ◽  
Early Holocene ◽  
Pollen Deposition ◽  
Pollen Record ◽  
Tree Pollen ◽  
Eastern Canada ◽  
Ice Cap ◽  
Pollen Concentrations ◽  
Holocene Record

A Holocene record of pollen deposition was obtained from an ice core drilled through the Agassiz Ice Cap. The pollen records long-range atmospheric transport to the ice cap. Pollen concentrations were highest in the early Holocene (∼15 grains/L), decreased in the mid-Holocene (∼6 grains/L), and increased in the late Holocene (∼9 grains/L). In the early Holocene, the higher concentration of tree pollen at a time when large parts of Canada were still ice-covered, and when forest was generally farther away, implies that atmospheric circulation was stronger than at present. Following deglaciation, as vegetation migrated north in central and eastern Canada, sources of pollen were closer to the Agassiz Ice Cap. However, the concentration of tree pollen decreased on the ice cap. This was followed by several relatively rapid changes after 3500 yr ago. Until ca. 3500 yr ago, the pollen concentration curves resembled the ice core δ18O and summer melt layer curves, both regarded as temperature proxies.

Lagrangian numerical simulations of canopy air flow effects on maize pollen dispersal

2007 ◽  
Vol 102 (2) ◽  
pp. 151-162 ◽  
Author(s):  
Raymond W. Arritt ◽  
Craig A. Clark ◽  
A. Susana Goggi ◽  
Higinio Lopez Sanchez ◽  
Mark E. Westgate ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Air Flow ◽  
Pollen Dispersal ◽  
Maize Pollen ◽  
Flow Effects

Spatially explicit modelling of transgenic maize pollen dispersal and cross-pollination

2003 ◽  
Vol 225 (2) ◽  
pp. 241-255 ◽  
Author(s):  
Christine Loos ◽  
Ralf Seppelt ◽  
Sara Meier-Bethke ◽  
Joachim Schiemann ◽  
Otto Richter
Keyword(s):  
Pollen Dispersal ◽  
Transgenic Maize ◽  
Spatially Explicit ◽  
Maize Pollen ◽  
Cross Pollination

Correcting an Error in “Early Irrigation on the Colorado Plateau near Zuni Pueblo, New Mexico”

2004 ◽  
Vol 69 (1) ◽  
pp. 149-150
Author(s):  
Glenna Dean
Keyword(s):  
New Mexico ◽  
Correction Factor ◽  
Rio Grande Valley ◽  
Pollen Grains ◽  
Rio Grande ◽  
Old Fields ◽  
Laboratory Methods ◽  
Maize Pollen ◽  
Corn Pollen ◽  
Pollen Concentrations

Damp et al. (2002:667) quote me as stating “Old fields in New Mexico in the fertile Rio Grande Valley produced maize pollen, typically at levels of less than 2.0 grains per cc (Dean 1998)” (emphasis added). In actuality, my statement reads, “It is not uncommon for as few as five corn pollen grains/g of sample to be the only evidence of a prehistoric cornfield” (Dean 1998:55; emphasis added). There is no “standard correction factor” that will allow sediment weights to be transformed to volumes or vice versa. Pollen concentrations for cultigens in pre-Columbian New Mexico fields can be very small numbers and reproducibility of laboratory methods is crucial.

Acoustic Sounder Observations of Atmospheric Turbulence Parameters in a Convective Boundary Layer

1993 ◽  
Vol 32 (8) ◽  
pp. 1433-1440 ◽  
Author(s):  
Frank Quintarelli
Keyword(s):  
Boundary Layer ◽  
Atmospheric Turbulence ◽  
Autocorrelation Function ◽  
Dissipation Rate ◽  
Function Method ◽  
Convective Conditions ◽  
Convective Boundary ◽  
Pulse Volume ◽  
Spectral Variance ◽  
Turbulence Parameters

Abstract Acoustic sounder observations of atmospheric turbulence parameters presented in this paper include estimates of the dissipation rate ε, estimates of turbulent scale lengths λ, and uncertainties in measurements of the variance of the vertical wind σ2w caused by pulse volume filtering. The calculations are mainly restricted to periods when the convective regime is well established. Two techniques are used to determine ε and λ. Structure functions and the spectral variance of the echo are used to determine ε. The spectrum of vertical velocities are used to calculate λm and the autocorrelation function is used to calculate λe. Estimates of ε obtained from the spectral variance of the echo compare favorably with estimates from the structure function during convective regimes but the agreement is poor in other regimes. The autocorrelation function method for obtaining length scales yields results more reliably than the spectral method. The ratio λm/λe compares favorably with values reported in the literature except at low heights where it is markedly lower. The effects of pulse volume filtering on measurements of σ2w were found to be significant. In convective conditions, σ2w deduced from the Doppler shift of the echo can be underestimated by up to 25% and by greater amounts in other conditions.

scholarly journals The Lagrangian particle dispersion model FLEXPART-WRF version 3.0

2013 ◽  
Vol 6 (3) ◽  
pp. 3615-3654 ◽  
Author(s):  
J. Brioude ◽  
D. Arnold ◽  
A. Stohl ◽  
M. Cassiani ◽  
D. Morton ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Atmospheric Transport ◽  
Dispersion Model ◽  
Vertical Gradient ◽  
Particle Dispersion ◽  
Point Sources ◽  
Lagrangian Particle ◽  
Convective Boundary ◽  
Meteorological Model ◽  
Computational Performance

Abstract. The Lagrangian particle dispersion model FLEXPART was originally designed for calculating long-range and mesoscale dispersion of air pollutants from point sources, such as after an accident in a nuclear power plant. In the meantime FLEXPART has evolved into a comprehensive tool for atmospheric transport modeling and analysis at different scales. This multiscale need has encouraged new developments in FLEXPART. In this document, we present a FLEXPART version that works with the Weather Research and Forecasting (WRF) mesoscale meteorological model. We explain how to run and present special options and features that differ from its predecessor versions. For instance, a novel turbulence scheme for the convective boundary layer has been included that considers both the skewness of turbulence in the vertical velocity as well as the vertical gradient in the air density. To our knowledge, FLEXPART is the first model for which such a scheme has been developed. On a more technical level, FLEXPART-WRF now offers effective parallelization and details on computational performance are presented here. FLEXPART-WRF output can either be in binary or Network Common Data Form (NetCDF) format with efficient data compression. In addition, test case data and the source code are provided to the reader as Supplement. This material and future developments will be accessible at http://www.flexpart.eu.

scholarly journals Identifying urban sources as cause to elevated grass pollen concentrations using GIS and remote sensing

2012 ◽  
Vol 9 (10) ◽  
pp. 14217-14253 ◽  
Author(s):  
C. A. Skjøth ◽  
P. V. Ørby ◽  
T. Becker ◽  
C. Geels ◽  
V. Schlünssen ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Grass Pollen ◽  
Atmospheric Transport ◽  
Local Scale ◽  
Source Distribution ◽  
Local Source ◽  
Source Areas ◽  
Pollen Concentrations ◽  
Pollen Sources ◽  
The City

Abstract. We examine here the hypothesis that during flowering, the grass pollen concentrations at a specific site reflect the distribution of grass pollen sources within a few kilometres from this site. We perform this analysis on data from a measurement campaign in the city of Aarhus (Denmark) using three pollen traps and by comparing these observations with a novel inventory of grass pollen sources. The source inventory is based on a new methodology developed for urban scale grass pollen sources. The new methodology is believed to be generally applicable for the European area, as it relies on commonly available remote sensing data combined with management information for local grass areas. The inventory has identified a number of grass pollen source areas present within the city domain. The comparison of the measured pollen concentrations with the inventory shows that the atmospheric concentrations of grass pollen in the urban zone reflects the source areas identified in the inventory, and that these pollen sources that are found to affect the pollen levels are located near and within the city domain. The results also show that during days with peak levels of pollen concentrations, there is no correlation between the three urban traps and an operational trap located just 60 km away. This finding suggests that during intense flowering, the grass pollen concentration mirrors the local source distribution, and is thus a local scale phenomenon. Model simulations aiming at assessment of population exposure to pollen levels are therefore recommended to take into account both local sources and local atmospheric transport, and not rely only on describing regional to long-range transport of pollen. The derived pollen source inventory can be entered into local scale atmospheric transport models in combination with other components that simulates pollen release in order to calculate urban scale variations in the grass pollen load. The gridded inventory with a resolution of 14 m is therefore made available as supplementary material to this paper, and the verifying grass pollen observations are in additional available in tabular form.

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