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991.
992.
P. K. Pal W. J. Prakash P. K. Thapliyal C. M. Kishtawal 《Meteorology and Atmospheric Physics》1999,71(3-4):157-168
Summary ?A methodology has been developed to assimilate satellite-measured rainfall during the initial phase of model integration
for extended range monsoon prediction. The vertical profiles of latent heating corresponding to different rain rates have
been derived from the model statistics. These heating rates have been assimilated through nudging in the thermodynamics equation
of the model. This procedure of assimilating observed heating has corrected the simulation of heating location in the model
and consequently removed the anomalous sinking motion over Indian landmass. With the correction of vertical circulation, both
mean July rainfall over India and the distribution have improved. Interannual variability has been brought out for the years
1987 and 1988. In view of the availability of rainfall profile from Tropical Rain Measuring Mission (TRMM) there is a scope
of adopting this method of assimilating observed rainfall, for extended range monsoon prediction.
Received February 12, 1999/Revised May 4, 1999 相似文献
993.
Della Vecchia A. Ferrazzoli P. Wigneron J.-P. Grant J.P. 《Geoscience and Remote Sensing Letters, IEEE》2007,4(4):508-512
This letter describes recent advances in modeling forest emissivity at L-band. The formulation is based on a previously developed discrete model and includes a new representation of forest litter. Comparisons with multitemporal radiometric data collected in the framework of the ldquoBray 2004rdquo experiment, which was carried out within Les Landes forest, are shown and discussed. Input variables are given by using detailed ground measurements. In general, the model reproduces both absolute values and temporal variations of measured brightness temperature. The contribution of the litter to overall emission was found to be important. 相似文献
994.
995.
Summary Boron-doped mullites were synthesized using aluminium nitrate-nonahydrate, tetraethoxysilane and boric acid in a sol–gel process
with subsequent annealing at 950 and 1300 °C for five hours. Two different bulk compositions with constant Al2O3 contents (60 and 70 mol%, respectively) and varying SiO2 plus B2O3 contents were investigated. X-ray powder diffraction analyses yielded a linear decrease of the lattice parameters with increasing
bulk B2O3 content, which was interpreted as to be due to boron incorporation. Related to the increasing boron content, corresponding
infrared spectra revealed a slight and continuous shift for most of the absorption bands. These data show that mullite is
able to incorporate large amounts of boron into its structure (up to about 20 mol% B2O3 depending on the bulk composition of the starting materials). Infrared analyses suggest that boron is incorporated into the
mullite structure in form of planar three-fold coordinated BO3 groups.
Author’s address: A. Beran, Institut für Mineralogie und Kristallographie, Universit?t Wien-Geozentrum, Althanstra?e 14, 1090 Wien, Austria 相似文献
996.
997.
D.M. Worrall M. Birkinshaw M.J. Hardcastle C.R. Lawrence 《Monthly notices of the Royal Astronomical Society》2001,326(3):1127-1133
We report results of an 18-ks exposure with the ACIS instrument on Chandra of the powerful z =0.62 radio galaxy 3C 220.1. The X-ray emission separates into cluster gas of emission-weighted kT ∼5 keV , 0.7–12 keV luminosity (to a radius of 45 arcsec) of 5.6×1044 erg s−1 and unresolved emission (coincident with the radio core). While the extended X-ray emission is clearly thermal in nature, a straightforward cooling-flow model, even in conjunction with a point-source component, is a poor fit to the radial profile of the X-ray emission. This is despite the fact that the measured properties of the gas suggest a massive cooling flow of ∼130 M⊙ yr−1 , and the data show weak evidence for a temperature gradient. The central unresolved X-ray emission has a power-law spectral energy index α ∼0.7 and 0.7–12 keV luminosity of 1045 erg s−1 , and any intrinsic absorption is relatively small. The two-point spectrum of the core emission between radio and X-ray energies has α rx =0.75 . Since this is a flatter spectrum than seen in other sources where the X-ray emission is presumed to be radio-related, regions close to the active galactic nucleus (AGN) in this source may dominate the central X-ray output, as is believed to be the case for lobe-dominated quasars. Simple unification models would be challenged if this were found to be the case for a large fraction of high-power radio galaxies. 相似文献
998.
A numerical model based upon fundamental principles, a standard (k, ) turbulence closure and a finite element integration technique, is applied to separated flows over hills. Predictions are compared to experimental data from a wind tunnel. Although few-equation turbulence closures have been shown to have obvious deficiencies with respect to comparable flows, the model predicts remarkably accurately, without coefficient adjustments of any kind. Even the turbulent intensity is predicted quite realistically. 相似文献
999.
Heidi Kreibich Veit Blauhut Jeroen C. J. H. Aerts Laurens M. Bouwer Henny A. J. Van Lanen Alfonso Mejia 《水文科学杂志》2020,65(3):491-494
ABSTRACTWe thank the authors, Brunella Bonaccorso and Karsten Arnbjerg-Nielsen for their constructive contributions to the discussion about the attribution of changes in drought and flood impacts. We appreciate that they support our opinion, but in particular their additional new ideas on how to better understand changes in impacts. It is great that they challenge us to think a step further on how to foster the collection of long time series of data and how to use these to model and project changes. Here, we elaborate on the possibility to collect time series of data on hazard, exposure, vulnerability and impacts and how these could be used to improve e.g. socio-hydrological models for the development of future risk scenarios. 相似文献
1000.
Damages to natural building stones induced by the action of frost are considered to be of great importance. Commonly, the frost resistance of building stones is checked by standardised freeze–thaw tests before using. Corresponding tests normally involve 30–50 freeze–thaw action cycles. In order to verify the significance of such measurements, we performed long-term tests on four selected rocks over 1,400 freeze–thaw action cycles. Additionally, numerous petrophysical parameters were analysed to compare the behaviour of rocks in the weathering tests according to the current explanatory models of stress formation by growing ice crystals in the pore space. The long-term tests yield more information about the real frost sensibility of the rocks. A clear deterioration cannot be determined in most cases until 50 weathering cycles have been completed. In the freeze–thaw tests, the samples are also stressed by changing temperature and moisture, indicating that different decay mechanisms can interfere with each other. Thus, thermohygric and moisture expansion are important damage processes. 相似文献