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161.
Using synthetic geometrical clouds and radiative microwave model, we examine the possibility to correct the estimations of liquid water path (LWP) or rain rate with cloud cover measurement. This information may be gotten by co-localized measurements of microwave and infrared/visible measurements on new satellites (TRMM, ADEOS 2, …). In a first step, the effects of fractional cloud cover on microwave brightness temperatures (TB) are investigated in three typical cases of nonprecipitating and precipitating (stratiform and convective) clouds. The beam-filling error (BFE) on brightness temperatures may be analyzed with the known spatial variability using 1D or 3D radiative transfer model. Relationships between BFE and subpixel cloud fraction (CF) are discussed according to the cloud type. We tested several parameters that characterize the horizontal cloud inhomogeneity within a radiometer field of view. BFE was found very sensitive to cloud type and inhomogeneity and is maximum for raining cloud with open spatial structure. In order to account for the uncertainty introduced by the spatial distribution, dependence of BFE on textural-based parameters is also discussed using homogeneity, entropy and an indicator of CF horizontal gradient. 相似文献
162.
YAO Zhanyu LI Wanbiao GAO Huilin ZHU Yuanjing ZHAO Bolin ZHANG Qiang 《Acta Meteorologica Sinica》2004,18(1):95-104
The ability of the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) for flooding and soil wetness detection has been demonstrated in this study.On the basis of TMI measurements,four methods,the classification method,the soil wetness index (SWI) method. the polarization difference index (PDI) method,and the polarization ratio index (PRI) method, were brought out to monitor flooding and study soil wetness in the Changjiang and Huaihe River Basins during the summer 1998.Compared with the images provided by L-band Synthetic Aperture Radar (L-SAR) and Radar Satellite (Radarsat) and the figures derived from daily rainfall data based on the Z-index method,the detection of flooding and soil wetness by TMI was proved to be feasible. 相似文献
163.
A. M. Uralov V. V. Grechnev G. V. Rudenko I. G. Rudenko H. Nakajima 《Solar physics》2008,249(2):315-335
Neutral Line associated Sources (NLSs) are quasi-stationary microwave sources projected onto vicinities of the neutral line
of the photospheric magnetic field. NLSs are often precursors of powerful flares, but their nature is unclear. We endeavor
to reveal the structure of an NLS and to analyze a physical connection between such a source with a site of energy release
in the corona above NOAA 10488 (October/November 2003). Evolution of this AR includes emergence and collision of two bipolar
magnetic structures, rise of the main magnetic separator, and the appearance of an NLS underneath. The NLS appears at a contact
site of colliding sunspots, whose relative motion goes on, resulting in a large shear along a tangent. Then the nascent NLS
becomes the main source of microwave fluctuations in the AR. The NLS emission at 17 GHz is dominated by either footpoints
or the top of a loop-like structure, an NLS loop, which connects two colliding sunspots. During a considerable amount of time,
the emission dominates over that footpoint of the NLS loop, where the magnetic field is stronger. At that time, the NLS resembles
a usual sunspot–associated radio source, whose brightness center is displaced towards the periphery of a sunspot. Microwave
emission of an X2.7 flare is mainly concentrated in an ascending flare loop, initially coinciding with the NLS loop. The top
of this loop is located at the base of a non-uniform bar-like structure visible in soft X-rays and at 34 GHz at the flare
onset. We reveal i) upward lengthening of this bar before the flare onset, ii) the motion of the top of an apparently ascending flare loop along the axis of this bar, and iii) a non-thermal microwave source, whose descent along the bar was associated with the launching of a coronal ejection. We
connect the bar with a probable position of a nearly vertical diffusion region, a site of maximal energy release inside an
extended pre-flare current sheet. The top of the NLS loop is located at the bottom of this region. A combination of the NLS
loop and diffusion region constitutes the skeleton of a quasi-stationary microwave NLS. 相似文献
164.
As the important components of the earth’s atmospheric system, cloud and precipitation strongly affect the global hydrology and energy cycles through the interaction of solar and infrared radiation with cloud droplets and the release of latent heat in precipitation development. The microwave observations in cloudy and rainy conditions have a large amount of information closely related to the development of weather systems, especially the severe weather systems like typhoon and rainstorm. Nevertheless, satellite microwave observations are usually only assimilated in clear-sky above the ocean and their cloud and precipitation content is discarded. Over the past two decades, several Numerical Weather Prediction (NWP) centers have gradually developed the “all-sky” approach to make use of the cloud- and precipitation-affected microwave radiances. It’s been proved that the all-sky assimilation can be used to improve the first guessed mass, wind, humidity, cloud and precipitation through the tracer effect. For providing an investigated reference for the future research of all-weather assimilation in domestic numerical weather forecast, this paper reviewed the all-sky assimilation methods using microwave observation data, analyzed the advantages and disadvantages of each method, and discussed the key technical problems and the existing difficulties and challenges in this field. With the development and application of the new generation of NWP model in China, advancing the domestic research of all-weather data assimilation technology will bring more scientific and practical benefits in the future. 相似文献
165.
本文扼要地介绍了近两年来全球性国际通信学术会议动态以及我国电信科学技术和工程建设的进展情况,研讨了我国气象通信建设的发展趋势,供各界参考。 相似文献
166.
Eric J. Lerner 《Astrophysics and Space Science》1995,227(1-2):61-81
The COBE data on cosmic Background radiation (CBR) isotropy and spectrum are generally considered to be explicable only in the context of the Big Bang theory and to be confirmation of that theory. However, this data can also be explained by an alternative, non-Big Bang model which hypothesizes an intergalactic radio-absorbing and scattering medium. A simple, inhomogenous model of such an absorbing medium can reproduce both the isotropy and spectrum of the CBR within the limits observed by COBE, and in fact gives a better to fit to the spectrum observations than does a pure blackbody. Such a model does not contradict any other observations, such as the existence of distant radio sources. 相似文献
167.
V.G. Ledenev R.A. Sych Y. Yan Q. Fu G. Huang H. Wu 《Journal of Atmospheric and Solar》2005,67(17-18):1720
A study is made of the initial stage of the 25 August 1999, event using high time-resolution microwave observations, as well as the data from the Siberian Solar Radio Telescope and Yohkoh/SXT/HXT. Microwave emission revealed fine structures with a typical time scale of about 1 s with a frequency drift 1 GHz/s, and structures with a typical time scale of less than 0.1 s with a frequency drift 10 GHz/s. Emission bands with a slower frequency drift are generated by energetic electrons subjected to the cyclotron resonance condition. This slower frequency drift is a consequence of a change in plasma density caused by the coalescence of magnetic structures with a typical size of the order of 108 cm, while the emission with a faster drift is generated by beams of energetic electrons generating Cherenkov resonance emission. The energetic electron beams are produced as a result of the interaction of magnetic structures 106–107 cm in size. 相似文献
168.
Donglian Sun Menas Kafatos Guido Cervone Zafer Boybeyi Ruixin Yang 《Natural Hazards》2007,43(2):273-284
Sea surface temperature (SST) from the remotely sensed infrared measurements, like the GOES, AVHRR, and MODIS, etc., show
missing values of SST over the cloudy regions associated with hurricanes. While satellite microwave measurements, like the
Tropical Rainfall Measuring Mission (TRMM) microwave imager (TMI), can provide SST even under cloudy conditions. Both satellite
microwave measurements and buoy observations show SST increase in advance of significant hurricane intensification. Moreover,
hurricane intensification may also be related to the location of high SST. Our results indicate pre-existing high SST anomaly
(SSTA) located at the right side of the storm track for Hurricane Katrina. Numerical simulations also confirm the important
impacts of SSTA location on hurricane intensification. Similar situations are also found for Hurricanes Rita and Wilma. In
contrast, if there is no high SSTA at the right location, hurricane may not undergo further intensification. This may explain
why not all tropical cyclones associated with warm waters can attain peak intensity (categories 4 and 5) during their life
cycle, and partially explains why hurricanes do not reach the maximum potential intensity as calculated only according to
the magnitude of SST. 相似文献
169.
ICP-AES测定海洋生物体中13种元素的微波消解条件优化 总被引:3,自引:1,他引:2
报道了微波密闭消解正交试验条件优化电感耦合等离子体发射光谱法(ICP-AES),同时测定8种海洋生物体中硒、铁、锰、锌、钙、镁、锶、砷、镉、铬、铜、铅和镍等13种元素含量的实验结果。优化后的样品消解条件为加入的HNO3V:H O2 2V=6.0 mL:1.0 mL,第二步程序升温温度为170℃,消解时间20 min;测定标准曲线相关系数大于0.999,相对标准偏差为0.30%~2.55%,加标回收率为92.0%~104.8%,方法检出限为0.0010~0.0468μg/g。结果表明,优化后方法测定操作简便、具有高的灵敏度、准确度和精密度,且能多元素同时测定,适合于海洋生物样品中这些元素含量的准确测定,并可为评估海产品食用安全提供科学依据。 相似文献
170.