Simulation of Atmospheric Boundary Layer Characteristics during Indian Summer Monsoon using Observations from Monsoon Trough Boundary Layer Experiment at Jodhpur, India     

T. V. B. P. S. Rama Krishna  Maithili Sharan 《Pure and Applied Geophysics》2007,164(8-9):1839-1859

The diurnal structure of the boundary layer during Indian summer monsoon period is studied using a one-dimensional meteorological boundary layer model and the observations collected from the Monsoon Trough Boundary Layer Experiment conducted in 1990 at Jodhpur, India. The model was initialized with the observed temperature profiles at 0530 LST on 17 July, 1990 at Jodhpur and was run for 26 hours. The study is carried out with a geostrophic wind speed of 9.5 m s⁻¹ corresponding to the strong wind simulation. The mean thermodynamic and wind structure simulated by the model are in good agreement with those observed from 30 m tower. The computed surface layer characteristics such as the surface fluxes, TKE and standard deviations of velocity components are found to be reasonably in good agreement with those based on turbulence measurements. The shear and buoyancy budget computed from the model are also compared with the turbulence measurements. The integrated cooling budget in the nocturnal boundary layer is examined.  相似文献   

Cooling rate effect as a cause of systematic overestimating of the absolute Thellier paleointensities: A cautionary note     

J. Morales  A. Goguitchaichvili  J. Urrutia-Fucugauchi 《Studia Geophysica et Geodaetica》2007,51(2):315-326

Cooling rate (CR) effects on the intensity of thermoremanent magnetization has been documented for archaeomagnetic materials, where cooling in laboratory conditions is generally much faster compared to natural cooling rates. Since the latter condition also applies to many volcanic rocks, we have investigated in this study the influences of the CR on the determination of absolute paleointensity using recent basaltic rocks. We used magnetically and thermally stable samples mainly containing Ti-poor pseudo-singledomain titanomagnetites (the most widely used material for Thellier paleointensity experiments). These samples previously succeed in retrieving the strength of laboratory field intensities with the Coe’s version of the Thellier method in a simulated paleointensity experiment using similar cooling rates. Our experimental results indicate that the cooling rate effects produce systematic and significant overestimates of the absolute intensity up to 70%. The effect can be much larger than predicted by Neél theory for non-interacting single-domain grains.  相似文献   

山西省雾的分析和预报   总被引：7，自引：0，他引：7  

杨小萍  骆丽楠等 《山西气象》2001,(3):7-9

公路为山西省经济发展做出巨大的贡献。为保证公路安全畅通，本文对影响公路安全行驶的重要天气－－雾的地理和时间分布进行分析，并根据雾的发生条件，提出了雾的预报思路。  相似文献   

An abrupt cooling event early in the last interglacial in the northern South China Sea     

TU Xia  ZHENG Fan  Wang Jiliang  CAI Huimei  WANG Pinxian  C.Bühring  M.Sarnthein 《中国科学D辑(英文版)》2001,44(10):865-870

The high-resolution quantitative analysis of the planktonic foraminifera and the δ¹⁸O records of the section between 96.49– 137.6 mcd at ODP Site 1144 on the continental slope of northern South China Sea reveals an abrupt cooling event of sea surface temperature (SST) during the last interglacial (MIS 5.5, i.e. 5e). The dropping range of the winter SST may come to 7.5°C corresponding to 1.2‰ of the δ¹⁸O value of sea surface water. This event is comparable with those discovered in the west Europe and the northern Atlantic Ocean, but expressed in a more intensive way. It is inferred that this event may have been induced by middle- to low-latitude processes rather than by polar ice sheet change. Since the Kuroshio-index speciesPulleniatina obliquiloculata displayed the most distinct change at the event, it may also be related to the paleoceanographic change of the low-latitude area in the western Pacific Ocean. This event can be considered as one of “Younger Dryas-style coolings” and is indicative of climate variability of the last interglacial stage.  相似文献   

Variations in chemical compositions of the eolian dust in Chinese Loess Plateau over the past 2.5 Ma and chemical weathering in the Asian inland   总被引：5，自引：0，他引：5  

CHEN Jun  LIU Lianwen  JI Junfeng  YANG Jiedong  CHEN Yang 《中国科学D辑(英文版)》2001,44(5):403-413

Major and trace elements as well as strontium isotopic composition have been analyzed on the acid-insoluble (AI) phase of the loess-paleosol sequence from Luochuan, Shaanxi Province, China. Results show that the chemical composition of AI phase of loess and paleosols is distinctive to the average composition of upper continental crust (UCC), characterized by depletion of mobile elements Na, Ca and Sr. The distribution pattern of elements in AI phase reveals that initial dust, derived from a vast area of Asian inland, has suffered from Na- and Ca-removed chemical weathering compared to UCC. Some geochemical parameters (such as CIA values, Na/K, Rb/Sr and⁸⁷Sr/⁸⁶Sr ratios) display a regular variation and evolution, reflecting that the chemical weathering in the source region of loess deposits has decreased gradually since 2.5 Ma with the general increase of global ice volume. This coincidence reflects that the aridity of Asian inland since the Quaternary is a possible regional response to the global climate change.  相似文献   

Aragonite from Mulanshan Glaucophane Schist: Implications for Regional Evolution of Southwestern Dabie Mountains, Central China     

Zhao Wenyu Center of Material Research  Analysis  Wuhan University of Technology  Wuhan Liu Rong Wang QinyanFaculty of Earth Sciences  China University of Geosciences  Wuhan Peng Changqi Zhang QingjieCenter of Material Research  Anal 《中国地质大学学报(英文版)》2001,12(3)

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Parameterization of the non-local thermodynamic equilibrium source function with chemical production by an equivalent two-level model     

Xun ZHU 《大气科学进展》2003,20(4):487-495

The classic two-level or equivalent two-level model that includes only the statistical equilibriumof radiative and thermal processes of excitation and quenching between two vibrational energy levelsis extended by adding chemical production to the rate equations. The modifications to the non-localthermodynamic equilibrium source function and cooling rate are parameterized by φc, which characterizesthe ratio of chemical production to collisional quenching. For applications of broadband emission of O3 at9.6 μm, the non-LTE effect of chemical production on the cooling rate and limb emission is proportionalto the ratio of O to O3. For a typical [O]/[O3], the maximum enhancements of limb radiance and coolingrate are about 15%-30% and 0.03-0.05 K day-1, respectively, both occurring near the mesopause regions.This suggests that the broadband limb radiance above ～80 km is sensitive to O3 density but not sensitiveto the direct cooling rate along the line-of-sight, which makes O3 retrieval feasible but the direct coolingrate retrieval difficult by using the O3 9.6 μm band limb emission.  相似文献   

Response of Atmospheric Low-frequency Wave to Oceanic Forcing in the Tropics     

FuZuntao  Zhao Qiang  QiaoFangli  Liu Shikuo 《大气科学进展》2000,17(4):569-575

1. IntroductionInvestigations about atmospheric LFW have been a focus of research since Madden andJulian/s outstanding analysis works (1971, 1972). Many dynamical and thermal mechanisms(Chao et al., 1996; Fu et al., 1998; Hendon et al., 1998; Krishnamurti et al., 1988; Lau andChan, 1988) have been advised to explain LFW. Among them are oceanic effects, such as SSTeffect, thermal forcing and others. Usually atmosphere and ocean are taken as a coupled system, which is used to explain ENS…  相似文献   

Two attempts of study of seismic source from teleseismic data by simulated annealing non-linear inversion     

P. Kolář 《Journal of Seismology》2000,4(2):197-213

Two seismic source studies usingteleseismic data are performed by Simulated Annealing(SA), a non-linear inversion method. The Very FastSimulated Annealing (VFSA) algorithm is used and onlyteleseismic data are inverted. We have designed a fastand efficient way of multiple direct problemevaluation, which is based on pre-calculating theelementary Green's function. During the process we setthe values of the inversion control parameters(temperature, number of iterations) and modified thecooling schedule. In the current version, theinversion seeks for the point source mechanism, thedepth of the source, the scalar moment and the sourcetime function (STF). The method is applied to twoearthquakes: 18 Nov. 1992 in Greece, M 5.9 and 14 Sep.1995 in Mexico, M7.3. The calculation is performed ona simple 1D model of the structure. For the firstearthquake the inversion recovered the solution fairlywell; for the second the solution was less acceptable.However, we do not consider this fact to be a failureof the method, but a consequence of an inadequatemodel of the source and of the medium structure. Acasual attempt of reliability determination was alsoperformed; the obtained values of errors arereasonable, except for a few cases when the methodfailed.  相似文献   

X-ray observations of distant Abell clusters     

E. Rizza  J. O. Burns  M. J. Ledlow  F. N. Owen  W. Voges  & M. Bliton 《Monthly notices of the Royal Astronomical Society》1998,301(2):328-342

We present results from a ROSAT HRI study of 11 distant ( z  ∼ 0.2–0.3) Abell clusters. We have performed a morphological analysis to search for and quantify substructure in the clusters. About 70 per cent of the sample shows significant evidence of substructure in the form of centroid shift or obvious X-ray clumps. We examine the clusters for the presence of cooling flows, and determine the physical properties of the ICM by deprojecting the HRI data. Nine of the clusters have central cooling times less than the age of the system, in agreement with fractions determined from nearby, X-ray-bright samples. Additional PSPC results are presented for four clusters in the sample, and ASCA results for six clusters. The temperatures and metallicities for these distant clusters appear to be consistent with nearby clusters of similar richness.  相似文献