UNCERTAINTY IN THE SPECIFICATION OF SURFACE CHARACTERISTICS: A STUDY OF PREDICTION ERRORS IN THE BOUNDARY LAYER   总被引：1，自引：0，他引：1  

Kiran Alapaty  Sethu Raman  Devdutta S. Niyogi 《Boundary-Layer Meteorology》1997,82(3):475-502

The effects of uncertainty in the specification of surface characteristics on simulated atmospheric boundary layer (ABL) processes and structure were investigated using a one-dimensional soil-vegetation-boundary layer model. Observational data from the First International Satellite Land Surface Climatology Project Field Experiment were selected to quantify prediction errors in simulated boundary-layer parameters. Several numerical 12-hour simulations were performed to simulate the convective boundary-layer structure, starting at 0700 LT 6 June 1987.In the control simulation, measured surface parameters and atmospheric data were used to simulate observed boundary-layer processes. In the remaining simulations, five surface parameters – soil texture, initial soil moisture, minimum stomatal resistance, leaf area index, and vegetation cover – were varied systematically to study how uncertainty in the specification of these surface parameters affects simulated boundary-layer processes.The simulated uncertainty in the specification of these five surface parameters resulted in a wide range of errors in the prediction of turbulent fluxes, mean thermodynamic structure, and the depth of the ABL. Under certain conditions uncertainty in the specifications of soil texture and minimum stomatal resistance had the greatest influence on the boundary-layer structure. A lesser but still moderately strong effect on the simulated ABL resulted from (1) a small decrease (4%) in the observed initial soil moisture (although a large increase [40%] had only a marginal effect), and (2) a large reduction (66%) in the observed vegetation cover. High uncertainty in the specification of leaf area index had only a marginal impact on the simulated ABL. It was also found that the variations in these five surface parameters had a negligible effect on the simulated horizontal wind fields. On the other hand, these variations had a significant effect on the vertical distribution of turbulent heat fluxes, and on the predicted maximum boundary-layer depth, which varied from about 1400–2300 m across the 11 simulations. Thus, uncertainties in the specification of surface parameters can significantly affect the simulated boundary-layer structure in terms of meteorological and air quality model predictions.  相似文献   

The transport of gravel in an ephemeral sandbed river     

Marwan A. Hassan  Asher P. Schick  Paul A. Shaw 《地球表面变化过程与地形》1999,24(7):623-640

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When we cannot not compare. A commentary on Tariq Jazeel's ‘Singularity. A manifesto for incomparable geographies’     

Kiran Asher 《Singapore journal of tropical geography》2019,40(1):26-29

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A conserved local cross helicity for non-barotropic MHD     

Asher Yahalom 《地球物理与天体物理流体动力学》2017,111(2):131-137

Cross helicity is not conserved in non-barotropic magnetohydro-dynamics (MHD) (as opposed to barotropic or incompressible MHD). Here we show that variational analysis suggests a new kind of local cross helicity which is conserved in the non-barotropic case. This local cross helicity can be integrated to a global non-barotropic cross helicity which was suggested in the work of Webb et al. (2014a,b). The non-barotropic cross helicity reduces to the standard cross helicity under barotropic assumptions. The new local cross helicity is conserved even for topologies for which the variational principle does not apply.  相似文献   

The influence of boulder shape on the spatial distribution of crustose coralline algae (Corallinales,Rhodophyta)          下载免费PDF全文

Kiran Liversage 《Marine Ecology》2016,37(2):459-462

Studies investigating the many ecologically and economically important species in benthic boulder habitats often use artificial boulders for determining species colonization. In some cases square‐edged blocks are used that are shaped much differently than the ovoid or ‘round’ boulders often occurring naturally. Here it was tested if the shape of boulders affects the distribution across the boulder surface of crustose coralline algae (CCA), a taxon that strongly influences ecological dynamics in this habitat. The distance that CCA extends from the edge of boulders toward the centre of the underside was measured, and it was found that CCA extended further underneath boulders that were round‐shaped compared with those that were block‐shaped, probably because of light reaching further underneath round boulders. This result shows how at least one important taxon can be affected by variation in the shape of these boulders. Hypotheses being tested that use artificial substrata to model naturally occurring boulders should be carried out only in places where the artificial and naturally occurring boulders match physically.  相似文献   

The fundamental role of the Oort cloud in determining the flux of comets through the planetary system     

V. V. Emel'yanenko  D. J. Asher  M. E. Bailey 《Monthly notices of the Royal Astronomical Society》2007,381(2):779-789

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High-eccentricity trans-Neptunian objects as a source of Jupiter-family comets     

V. V. Emel'yanenko  D. J. Asher  M. E. Bailey 《Monthly notices of the Royal Astronomical Society》2004,350(1):161-166

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Spectral analysis of wind and temperature components during lightning in pre-monsoon season over Ranchi     

Arun K. Dwivedi  Sagarika Chandra  Manoj Kumar  Sanjay Kumar  N. V. P. Kiran Kumar 《Meteorology and Atmospheric Physics》2015,127(1):95-105

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Peak ground motion predictions in India: an appraisal for rock sites   总被引：1，自引：0，他引：1  

Sankar Kumar Nath  Kiran Kumar Singh Thingbaijam 《Journal of Seismology》2011,15(2):295-315

Proper selection and ranking of Ground Motion Prediction Equations (GMPEs) is critical for successful logic-tree implementation in probabilistic seismic hazard analysis. The present study explores this issue in predicting peak ground accelerations at the rock sites in India. Macroseismic intensity data complemented with limited strong ground-motion recordings are used for the purpose. The findings corroborate the possible conformity between the GMPEs developed for tectonically active shallow crust across the globe. On the other hand, the relevant GMPEs in the intraplate regions cluster into two different groups with the equations of lower ranks catering to higher ground motions. The earthquakes in the subduction zones have significant regional implications. However, affinity in the ground-motion attenuations between the major interface events (M _W > 7.4) in Andaman-Nicobar, Japan and Cascadia, respectively, is noted. This can be also observed for the intraslab events in the Hindukush and Taiwan respectively. Overall, we do not observe any significant advantage with the equations developed using the regional data. These findings are expected to be useful in probabilistic seismic hazard analysis across the study region.  相似文献   

Variations in Oscillation Frequencies From Minimum to Maximum of Solar Activity     

Jain  Kiran  Bhatnagar  A. 《Solar physics》2003,213(2):257-268

The temporal variation in intermediate-degree-mode frequencies is analysed using helioseismic data which cover the minimum to the maximum phase of the current solar cycle. To study the variation in detail, the measured frequency shifts of f and p modes are decomposed into two components, viz., oscillatory and non-oscillatory. The f-mode frequencies exhibit prominent oscillatory behavior in contrast to p modes where the oscillatory nature of the frequencies is not clearly seen. Also, the oscillatory part contributes significantly to the f-mode frequencies while p-mode frequencies have maximum contribution from the non-oscillatory part. The amplitude of both oscillatory and non-oscillatory parts is found to be a function of frequency. The non-oscillatory part is observed to have a strong correlation with solar activity.  相似文献