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A new parameterization for atmospheric transmission and O2 photodissociation in the Schumann-Runge band region has been developed and tested with a 1D radiative-photochemical model. The parameterization is based on the O2-column along the line of sight to the Sun and the local temperature. Line-by-line calculations have served as a benchmark for testing this method and several other, commonly used, parameterizations. The comparisons suggest that differences between the line-by-line calculations and currently accepted parameterizations can be reduced significantly by using the new method, particularly at large solar zenith angles. The production rate of O-atoms computed with this method shows less than 6% deviation compared to the line-by-line calculations at any altitude, all solar zenith angles and in all seasons. The largest errors are found toward the shorter wavelengths in the Schumann-Runge region at low altitudes. Transmittance is approximated to better than 4% at any altitude and/or solar zenith angle. The total O-production rate above 20 km is approximated to better than 2%. The new parameterization is easily implemented in existing photochemical models and in many cases it may simply replace the existing algorithm. The computational effort exceeds that of other parameterizations but in view of the total computation time needed for the actual calculation of the parameterized Schumann-Runge bands this should not lead to significant performance degeneration. The first 14 coefficients of the parameterization are included in this study. Both the complete sets of coefficients and a simple algorithm can be obtained by contacting the authors. A photochemical model study shows the largest effect of the parameterization method is on odd hydrogen concentrations. Subsequent interaction with an odd oxygen family causes differences in the ozone concentrations between the different parameterizations of more than 10% at selected altitudes. Although it is already established that deficiencies in the treatment of Schumann-Runge band absorption are unlikely to explain the current underestimation of ozone concentration at the stratopause in a variety of photochemical models, this study does show that the choice of parameterization has a large impact on the accuracy of the results at large solar zenith angles and in different seasons. 相似文献
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I.C. McDade E.J. Llewellyn R.G.H. Greer D.P. Murtagh 《Planetary and Space Science》1982,30(11):1133-1136
A simple vibrational relaxation model which reproduces the observed altitude integrated vibrational distribution of the Herzberg I bands in the nightglow is used to derive the altitude profiles of the individual vibrational levels at 1 km intervals in the 85–115 km height range. The possible errors associated with using rocket-borne photometer measurements of a limited number of bands in the O2(A3Σu+?X3Σg?) system to infer the total Herzberg I emission profile are assessed. 相似文献
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M. S. Johnston P. Eriksson S. Eliasson C. G. Jones R. M. Forbes D. P. Murtagh 《Climate Dynamics》2012,39(11):2713-2731
Tropical upper tropospheric humidity, clouds, and ice water content, as well as outgoing longwave radiation (OLR), are evaluated in the climate model EC Earth with the aid of satellite retrievals. The Atmospheric Infrared Sounder and Microwave Limb Sounder together provide good coverage of relative humidity. EC Earth’s relative humidity is in fair agreement with these observations. CloudSat and CALIPSO data are combined to provide cloud fractions estimates throughout the altitude region considered (500–100?hPa). EC Earth is found to overestimate the degree of cloud cover above 200?hPa and underestimate it below. Precipitating and non-precipitating EC Earth ice definitions are combined to form a complete ice water content. EC Earth’s ice water content is below the uncertainty range of CloudSat above 250?hPa, but can be twice as high as CloudSat’s estimate in the melting layer. CERES data show that the model underestimates the impact of clouds on OLR, on average with about 9?W?m?2. Regionally, EC Earth’s outgoing longwave radiation can be ~20?W?m?2 higher than the observation. A comparison to ERA-Interim provides further perspectives on the model’s performance. Limitations of the satellite observations are emphasised and their uncertainties are, throughout, considered in the analysis. Evaluating multiple model variables in parallel is a more ambitious approach than is customary. 相似文献
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Earth observation relies heavily on imaging. Extraction of informationin turn relies on image processing and analysis. A new and powerfulmethodology has come to the fore in recent years, based on the waveletand other multiscale transforms. Of the many possible application areaswe describe in this paper some approaches for object and feature findingin images', noise filtering of synthetic aperture radar (SAR) images, andthe automatic geometrical registration of different images. 相似文献
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M. J. López-González D. P. Murtagh P. J. Espy J. J. López-Moreno R. Rodrigo G. Witt 《Annales Geophysicae》1996,14(1):59-67
The temporal variation of OH* emission and weighted rotational temperature has been studied for high-latitude summer conditions. Observations for 60°N latitude show OH weighted temperatures that always exceed 145 K even during periods of noctilucent clouds. Using a one-dimensional model the effects in excited OH concentration produced by changes in temperature, eddy diffusion, and water concentration have been analysed. We are forced to conclude that there remains a discrepancy between the OH temperatures predicted by the model and that obtained from OH* measurements. An increase in OH* concentration from June to the beginning of August, followed by a slow decrease during August has been obtained in agreement with the measurements. The 16-day modulation present in the measurements was simulated in a simple manner by varying the temperature in the mesopause region. This variation produces periodic modulations in both OH* concentration and weighted temperature of 16 days. The results show the temperature leading the OH* column concentration by three days. This phase shift is also present in the observations. 相似文献
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Murtagh A 《Irish geography : bulletin of the Geographical Society of Ireland》2010,43(2):149-159
Getting food to our plates has become a highly complex, industrialised and globalised process. However, transformations in how our food is supplied are not without resistance. Initiatives are emerging that take a step back to simpler, alternative methods of food supply, bringing the producer and consumer closer together. Alternative food initiatives which are commonly found in Ireland include allotments, community gardens, farmers' markets, farm shops and on-farm food enterprises. Understanding alternative food activities as a social movement can illuminate a fresh perspective on their nature and potential. While briefly considering the broad dynamics of alternative food activity in Ireland, this exploratory paper looks at the question of the nature of resistance and whether a collective vision may exist across initiatives, illustrated by two examples, a community garden and consumer food co-op. Finally some conclusions as to how alternative food initiatives may play a transformative role within the contemporary food system are discussed. 相似文献
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Eight thousand images of the solar corona were captured during the June 2001 total solar eclipse. New software for the alignment
of the images and an automated technique for detecting intensity oscillations using multi-scale wavelet analysis were developed.
Large areas of the images covered by the Moon and the upper corona were scanned for oscillations and the statistical properties
of the atmospheric effects were determined. The à Trous wavelet transform was used for noise reduction and Monte Carlo analysis as a significance test of the detections. The effectiveness
of those techniques is discussed in detail. 相似文献
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F.D. Murtagh 《Astrophysics and Space Science》1997,247(1-2):31-40
Astronomy as a discipline is essentially online and digital. It thus offers an ideal framework for the examination of current
trends in electronic publishing. Electronic publishing is driven on the winds of various underlying technologies. We look
at a number of these, focusing on information access and retrieval.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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