Application of a semi-spectral cloud water parameterization to cooling tower plumes simulations     

Emmanuel Bouzereau  Luc Musson Genon  Bertrand Carissimo 《Atmospheric Research》2008,90(1):78-90

In order to simulate the plume produced by large natural draft cooling towers, a semi-spectral warm cloud parameterization has been implemented in an anelastic and non-hydrostatic 3D micro-scale meteorological code. The model results are compared to observations from a detailed field experiment carried out in 1980 at Bugey (location of an electrical nuclear power plant in the Rhône valley in East Central France) including airborne dynamical and microphysical measurements. Although we observe a slight overestimation of the liquid-water content, the results are satisfactory for all the 15 different cases simulated, which include different meteorological conditions ranging from low wind speed and convective conditions in clear sky to high wind and very cloudy. Such parameterization, which includes semi-spectral determination for droplet spectra, seems to be promising to describe plume interaction with atmosphere especially for aerosols and cloud droplets.  相似文献   

地形动力作用对华北暴雨和云系影响的数值研究   总被引：9，自引：4，他引：5       下载免费PDF全文

廖菲  胡娅敏  洪延超 《高原气象》2009,28(1):115-126

为了进一步研究地形对华北暴雨的影响,本文从云微物理学的角度出发,选取了2005年7月22～24日的一次华北暴雨过程为研究对象,利用中尺度数值模式ARPS,通过地形高度敏感性试验,详细讨论了地形高度变化对流场、云及降水微物理过程的影响.结果表明:地形高度变化对水平和垂直流场的大小和分布都有较大影响;地形高度增加有利于迎风坡附近水平风场辐合和垂直上升运动发展,这对云的垂直和水平发展影响都很大,尤其是对中高层云的发展影响最明显,并且能明显扩大地面降水的分布范围,地面最大降水量也有所增多.这主要是由于地形高度增加后能促进中高层云水的产生,尤其是零度层之上的过冷云水含量的增多,这大大促进了冰相粒子(雪和霰)的增多,从而使得以冷云过程为主的此次降水过程中,冰相粒子融化形成的雨水含量增多.虽然地形高度的增加会抑制云系发展前期的暖云过程,但对冷云过程有持续加强作用,而且不会明显改变云内降水的形成机制,冷云过程依然是降水的最大贡献项,总体上促进了云和降水的发展.  相似文献   

一个半线性耦合抛物型方程组爆破解的速率估计     

范萍  李刚  黄瑜 《南京气象学院学报》2008,31(3):441-446

考虑一个方程和非线性边界条件耦合的半线性抛物型方程组,运用Scaling方法、Green函数、Schauder估计等方法,研究该方程组解的爆破速率,并给出非线性反应项和吸收项对爆破速率的影响。  相似文献   

红外焦平面探测器信息获取与预处理电路设计     

范文龙  董峰  傅雨田 《遥感学报》2014,18(Z1):30-34

针对中国科学院上海技术物理研究所研制的1500元红外线列焦平面探测器的输出特性,提出了以低噪声运放为核心的信息获取电路和以FPGA(Field Programmable Gate Array)为核心的数据预处理的设计方案,实现了驱动电路和探测器的良好匹配,较好地发挥了探测器高灵敏度的特性.测试结果表明,该方案不仅对系统获得优于50 mK噪声等效温差的高灵敏度成像起到了重要作用,足够宽的量化设计还保证了系统的动态范围和图像的丰富层次.该设计方案已成功应用在一些其他类型的红外焦平面探测器中.  相似文献   

Planetary transit observations at the University Observatory Jena: XO‐1b and TrES‐1     

St. Raetz  M. Mugrauer  T.O.B. Schmidt  T. Roell  T. Eisenbeiss  M.M. Hohle  N. Tetzlaff  M. Va&#x;ko  A. Seifahrt  Ch. Broeg  J. Koppenhoefer  R. Neuhuser 《Astronomische Nachrichten》2009,330(5):475-481

We report on observations of transit events of the transiting planets XO‐1b and TrES‐1 with a 25 cm telescope of the University Observatory Jena. With the transit timings for XO‐1b from all 50 available XO, SuperWASP, Transit Light Curve (TLC)‐Project‐ and Exoplanet Transit Database (ETD)‐data, including our own I ‐band photometry obtained in March 2007, we find that the orbital period is P = (3.941501 ± 0.000001) d, a slight change by ∼3 s compared to the previously published period. We present new ephemeris for this transiting planet. Furthermore, we present new R ‐band photometry of two transits of TrES‐1. With the help of all available transit times from literature this allows us to refine the estimate of the orbital period: P = (3.0300722 ± 0.0000002) d. Our observations will be useful for future investigations of timing variations caused by additional perturbing planets and/or stellar spots and/or moons (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Repeating microlensing events in the OGLE data     

J. Skowron  &#;. Wyrzykowski  S. Mao  M. Jaroszy&#;ski 《Monthly notices of the Royal Astronomical Society》2009,393(3):999-1009

Microlensing events are usually selected among single-peaked non-repeating light curves in order to avoid confusion with variable stars. However, a microlensing event may exhibit a second microlensing brightening episode when the source or/and the lens is a binary system. A careful analysis of these repeating events provides an independent way to study the statistics of wide binary stars and to detect extrasolar planets. Previous theoretical studies predicted that 0.5–2 per cent of events should repeat due to wide binary lenses. We present a systematic search for such events in about 4000 light curves of microlensing candidates detected by the Optical Gravitational Lensing Experiment (OGLE) towards the Galactic bulge from 1992 to 2007. The search reveals a total of 19 repeating candidates, with six clearly due to a wide binary lens. As a by-product, we find that 64 events (∼2 per cent of the total OGLE-III sample) have been misclassified as microlensing; these misclassified events are mostly nova or other types of eruptive stars. The number and importance of repeating events will increase considerably when the next-generation wide-field microlensing experiments become fully operational in the future.  相似文献   

Dynamical simulations of the planetary system HD 69830     

Matthew J. Payne  Eric B. Ford  Mark C. Wyatt  Mark Booth 《Monthly notices of the Royal Astronomical Society》2009,393(4):1219-1234

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On corotation torques, horseshoe drag and the possibility of sustained stalled or outward protoplanetary migration   总被引：1，自引：0，他引：1  

S.-J. Paardekooper  J. C. B. Papaloizou 《Monthly notices of the Royal Astronomical Society》2009,394(4):2283-2296

We study the torque on low-mass protoplanets on fixed circular orbits, embedded in a protoplanetary disc in the isothermal limit. We consider a wide range of surface density distributions including cases where the surface density increases smoothly outwards. We perform both linear disc response calculations and non-linear numerical simulations. We consider a large range of viscosities, including the inviscid limit, as well as a range of protoplanet mass ratios, with special emphasis on the co-orbital region and the corotation torque acting between disc and protoplanet.
For low-mass protoplanets and large viscosity, the corotation torque behaves as expected from linear theory. However, when the viscosity becomes small enough to enable horseshoe turns to occur, the linear corotation torque exists only temporarily after insertion of a planet into the disc, being replaced by the horseshoe drag first discussed by Ward. This happens after a time that is equal to the horseshoe libration period reduced by a factor amounting to about twice the disc aspect ratio. This torque scales with the radial gradient of specific vorticity, as does the linear torque, but we find it to be many times larger. If the viscosity is large enough for viscous diffusion across the co-orbital region to occur within a libration period, we find that the horseshoe drag may be sustained. If not, the corotation torque saturates leaving only the linear Lindblad torques. As the magnitude of the non-linear co-orbital torque (horseshoe drag) is always found to be larger than the linear torque, we find that the sign of the total torque may change even for mildly positive surface density gradients. In combination with a kinematic viscosity large enough to keep the torque from saturating, strong sustained deviations from linear theory and outward or stalled migration may occur in such cases.  相似文献   

Vortices in self-gravitating gaseous discs     

G. R. Mamatsashvili  W. K. M. Rice 《Monthly notices of the Royal Astronomical Society》2009,394(4):2153-2163

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Diurnal thermal tides in a non-synchronized hot Jupiter     

Pin-Gao Gu  Gordon I. Ogilvie 《Monthly notices of the Royal Astronomical Society》2009,395(1):422-435

We perform a linear analysis to investigate the dynamical response of a non-synchronized hot Jupiter to stellar irradiation. In this work, we consider the diurnal Fourier harmonic of the stellar irradiation acting at the top of a radiative layer of a hot Jupiter with no clouds and winds. In the absence of the Coriolis force, the diurnal thermal forcing can excite internal waves propagating into the planet's interior when the thermal forcing period is longer than the sound crossing time of the planet's surface. When the Coriolis effect is taken into consideration, the latitude-dependent stellar heating can excite weak internal waves (g modes) and/or strong baroclinic Rossby waves (buoyant r modes) depending on the asynchrony of the planet. When the planet spins faster than its orbital motion (i.e. retrograde thermal forcing), these waves carry negative angular momentum and are damped by radiative loss as they propagate downwards from the upper layer of the radiative zone. As a result, angular momentum is transferred from the lower layer of the radiative zone to the upper layer and generates a vertical shear. We estimate the resulting internal torques for different rotation periods based on the parameters of HD 209458b.  相似文献