近50a北京人居环境中气候因子的变化特征   总被引：7，自引：1，他引：7  

张秀丽  孙燕 《南京气象学院学报》2007,30(4):519-523

应用1951—2003年逐日气象观测资料,分析影响北京城市人居环境主要气候因子的变化特征。结果表明：近50 a北京增暖趋势明显,气候变暖与极端热（冷）不舒适日数之间具有较好的相关性,其所导致的总体趋势是使热（冷）不舒适日数上升（下降）,同时增加了出现极端热（冷）不舒适日的随机性。分析还表明,北京年加热度日指数存在明显下降趋势,年制冷度日指数变化正好相反,这意味着未来北京冬季供暖耗费能源将会减少,而夏季降温耗费能源将会增加。  相似文献   

北京地区热度日和冷度日的变化特征   总被引：13，自引：3，他引：13       下载免费PDF全文

谢庄苏德斌  虞海燕李德平于丽萍  胡天洁 《应用气象学报》2007,18(2):232-236

应用1951—2004年北京逐日平均温度制作北京月、年的热度日 (HDD) 和冷度日 (CDD)。其中平均月HDD以1月 (687.9度日) 最大, 多年平均的年值为2922.6度日, 多年变化呈明显的下降趋势, 下降率为-99.5度日/10 a。平均月CDD以7月 (259.2度日) 最大。CDD多年平均的年值为826.7度日, 多年变化呈上升趋势, 上升率为39.0度日/10 a。1971—2004年HDD月城郊差值 (北京站-密云站) 冬季较大, 最大值为-73.8度日 (12月)。月CDD的城郊差值比HDD的差值小, 最大差值在8月 (34.0度日)。年HDD和CDD与年平均气温具有较高的相关性。年际、年代际HDD与年际、年代际平均气温具有反位相变化趋势, 随着气候增暖, 北京地区HDD将趋于减小, 冬季用于供暖的能源将减少; CDD将趋于增加, 夏季用于制冷降温的能源将增加。  相似文献   

Coastal cooling/heating events: Laboratory experiments     

Natalia Demchenko  Irina Chubarenko 《Acta Geophysica》2007,55(1):56-64

We report the results of laboratory experiments on water heating/cooling, performed in 5 m long water channel with a slope. About 63 series of photos were analyzed: for 3 locations, for 3 bottom slopes (3.7, 6.7 and 12 degrees) and for different Ra numbers. It was pointed out that there exist two types of mixing characterizing different circulations in the presence of slope: gravity current and undersurface jet; the thermal bar is the region where one type of mixing is replaced by another; the highest speed and flowrate are at the break point; the flow is three-dimensional.  相似文献   

Chandra X-ray observations of the 3C 295 cluster core     

S.W. Allen  G.B. Taylor  P.E.J. Nulsen  R.M. Johnstone  L.P. David  S. Ettori  A.C. Fabian  W. Forman  C. Jones  B. McNamara 《Monthly notices of the Royal Astronomical Society》2001,324(4):842-858

We examine the properties of the X-ray gas in the central regions of the distant ( z =0.46) , X-ray luminous cluster of galaxies surrounding the powerful radio source 3C 295, using observations made with the Chandra Observatory . Between radii of 50 and 500 kpc, the cluster gas is approximately isothermal with an emission-weighted temperature, kT ∼5 keV . Within the central 50-kpc radius this value drops to kT ∼3.7 keV . The spectral and imaging Chandra data indicate the presence of a cooling flow within the central 50-kpc radius of the cluster, with a mass deposition rate of approximately 280 M_⊙ yr⁻¹. We estimate an age for the cooling flow of 1–2 Gyr , which is approximately 1000 times older than the central radio source. We find no evidence in the X-ray spectra or images for significant heating of the X-ray gas by the radio source. We report the detection of an edge-like absorption feature in the spectrum for the central 50-kpc region, which may be caused by oxygen-enriched dust grains. The implied mass in metals seen in absorption could have been accumulated by the cooling flow over its lifetime. Combining the results on the X-ray gas density profile with radio measurements of the Faraday rotation measure in 3C 295, we estimate the magnetic field strength in the region of the cluster core to be B ∼12 μG .  相似文献   

‘Evolution of a Storm-driven Cloudy Boundary Layer in the Arctic’     

Jun?InoueEmail author  Branko?Kosovi?  Judith?A.?Curry 《Boundary-Layer Meteorology》2005,117(2):213-230

To investigate the processes of development and maintenance of low-level clouds during major synoptic events, the cloudy boundary layer under stormy conditions during the summertime Arctic has been studied using observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment and large-eddy simulations (LES). On 29 July 1998, a stable Arctic cloudy boundary-layer event was observed after the passage of a synoptic low pressure system. The local dynamic and thermodynamic structure of the boundary layer was determined from aircraft measurements including the analysis of turbulence, cloud microphysics and radiative properties. After the upper cloud layer advected over the existing cloud layer, the turbulent kinetic energy (TKE) budget indicated that the cloud layer below 200 m was maintained predominantly by shear production. Observations of longwave radiation showed that cloud-top cooling at the lower cloud top has been suppressed by radiative effects of the upper cloud layer. Our LES results demonstrate the importance of the combination of shear mixing near the surface and radiative cooling at the cloud top in the storm-driven cloudy boundary layer. Once the low-level cloud reaches a certain height, depending on the amount of cloud-top cooling, the two sources of TKE production begin to separate in space under continuous stormy conditions, suggesting one possible mechanism for the cloud layering. The sensitivity tests suggest that the storm-driven cloudy boundary layer is possibly switched to the shear-driven system due to the advection of upper clouds or to the buoyantly driven system due to the lack of wind shear. A comparison is made of this storm-driven boundary layer with the buoyantly driven boundary layer previously described in the literature.  相似文献   

Development of micro-scale joints in volcanic rocks under thermal stress     

Susanta Kumar Samanta 《Journal of Earth System Science》2001,110(3):191-203

Petrographic studies of samples of the Rajmahal basalt reveal a variety of microscopic joints within phenocrysts, which seem to have developed under the influence of thermal stresses during cooling. The theoretical analysis shows that:

–	•thermal stresses develop in a system only under unsteady state of cooling,
–	•the stresses responsible for the development of joints are tensile in nature, and
–	•the magnitude of stresses increases with increasing rates of cooling.

In order to understand the effects of cooling rate on the mode of jointing, analogue model experiments were performed by quenching melt films of organic, crystalline materials under varying cooling conditions. In experiments, non-branching linear joints developed at relatively lower rates of cooling by a process of sub-critical crack propagation. On the other hand, at higher rates of cooling the mechanism of crack propagation was essentially supercritical leading to the development of branching joints.  相似文献   

RADIATIVE COOLING AND BROADBAND PHENOMENON IN LOW-FREQUENCY WAVES     

付遵涛  蒋循  乔方利  刘式适 《热带气象学报(英文版)》2000,6(1):75-85

In this paper, we analyze the effects of radiative cooling on the pure baroclinic low-frequency waves under the approximation of equatorial β-plane and semi-geostrophic condition. The results show that radiative cooling does not, exclusively, provide the damping effects on the development of low-frequency waves.Under the delicate radiative-convective equilibrium, radiative effects will alter the phase speed and wave period,and bring about the broadband of phase velocity and wave period by adjusting the vertical profiles of diabaticheating. When the intensity of diabatic heating is moderate and appropriate, it is conductive to the development and sustaining of the low-frequency waves and their broadband phenomena, not the larger, the better. The radiative cooling cannot be neglected in order to reach the moderate and appropriate intensity of diabatic heating.  相似文献   

中国东部地区夏季对流层大气辐射加热的研究   总被引：2，自引：0，他引：2  

王承伟  陈渭民  宋庆利  胡文东  殷世萍 《南京气象学院学报》2005,28(3):384-390

应用TOVS资料及MORTRAN3模式，研究中国东部夏季对流层的太阳短波辐射和红外辐射对大气的加热状况。考虑不同纬度，不同大气状况下12个站点43个样本的太阳加热率和红外冷却率情况，分析发现：在夏季的对流层，太阳加热率随着距地面的高度增加而减小，它的大小及变化率与纬度、天顶角及当时大气的状况有关，同时，太阳加热率也存在日变化。红外冷却率在对流层中、高层有极小值，它的大小及变化率与当时的大气状况及纬度有关。将本文的结果与前人的结论及实况相比较，发现本文较为真实地反映了中国东部地区夏季对流层的辐射加热情况，利用卫星资料计算的结果基本可信，  相似文献   

Isotopic equilibration ages for the Miyanohara tonalite from the Higo metamorphic belt in central Kyushu, Southwest Japan: Implications for the tectonic setting during the Triassic     

Atsushi Kamei  Masaaki Owada  Takuji Hamamoto  Yasuhito Osanai  Masaki Yuhara and  Hiroo Kagami 《Island Arc》2000,9(1):97-112

Abstract Miyanohara tonalite occurs in the middle part of the Higo metamorphic belt in the central Kyushu, Southwest Japan. This tonalite intrudes into early Permian Ryuhozan metamorphic rocks in the south and is intruded by Cretaceous Shiraishino granodiorite in the north. The Miyanohara tonalite yielded three mineral ages: (i) 110–100 Ma for Sm–Nd and Rb–Sr internal isochrons and for K–Ar hornblende; (ii) 183 Ma for Sm–Nd internal isochron; and (iii) 211 Ma for Sm–Nd internal isochron. The ages of 110–100 Ma may indicate cooling age due to the thermal effect of the Shiraishino granodiorite intrusion. The ages of 183 Ma and 211 Ma are consistent with timing of intrusion of the Miyanohara tonalite based on geologic constraints. The hornblende in the sample which gave 183 Ma shows discontinuous zoning under microscope, whereas the one which gave 211 Ma does not show zonal structure. These mineralogical features suggest that the 183 Ma sample has suffered severely from later tectonothermal effect compared with the 211 Ma sample. Therefore, the age of 211 Ma is regarded as near crystallization age for the Miyanohara tonalite. The magmatic process, geochronology and initial Sr and Nd isotope ratios for the Miyanohara tonalite are similar to those of early Jurassic granites from the Outer Plutonic Zone of the Hida belt that constitutes a marginal part of east Asia before the opening of the Japan Sea. Intrusion of the Miyanohara tonalite is considered to have taken place in the active continental margin during the late Triassic.  相似文献   

准噶尔盆地的类型和构造演化   总被引：35，自引：1，他引：34  

张晓东 《地学前缘》2000,7(4):431-440

准噶尔盆地的早二叠世属于裂谷还是前陆盆地 ,存在意见分歧 ;晚二叠世—老第三纪盆地的性质也不确定。文中通过对盆地构造几何学、沉降史、热史及火山岩的综合分析研究 ,对盆地类型和构造演化获得了一些新的认识 :( 1)准噶尔盆地在早二叠世为裂谷 ,晚二叠世为热冷却伸展坳陷 ,三叠纪—老第三纪为克拉通内盆地 ,新第三纪至今 ,由于印度板块与亚洲大陆碰撞才形成陆内前陆盆地。 ( 2 )对石炭纪—早二叠世的岩浆活动结合区域构造资料的研究表明 ,准噶尔地区古生代的板块运动和造山作用具软碰撞特点 ,早二叠世的裂谷盆地是在软碰撞背景下造山带伸展塌陷的产物。 ( 3)地幔热对流作用可能是软碰撞造山后伸展塌陷的主要深部动力学机制。  相似文献