COOLING RATES, SKY VIEW FACTORS AND THE DEVELOPMENT OF INTRA-URBAN AIR TEMPERATURE DIFFERENCES     

BJÖRN HOLMER  SOFIA THORSSON  INGEGÄRD ELIASSON 《Geografiska Annaler: Series A, Physical Geography》2007,89(4):237-248

Intra‐urban cooling rates were monitored for a year in the centre of Göteborg on the Swedish west coast. Five sites with different building geometry ‐ from dense canyon to open space ‐ within a radius of 300 m were analysed. Results showed two modes of cooling during the night. In the first mode, the cooling was site‐dependent ‐the open space cooled the most and the dense canyon the least. In the second mode, which began about 3–4 hours after sunset, all sites cooled at the same rate. Our hypothesis is that in the early part of the evening both radiative divergence and sensible heat dominate the cooling. However, as the evening progresses, a spatially homogeneous inversion is established which controls the radiative cooling, making the cooling independent of both surface geometry and surface type. From April to November the sites cooled rapidly around sunset and the cooling slowly decreased during the rest of the night. However, between December and March, the cooling was less intense, with an almost constant rate during the entire night. It has been suggested that this might be the result of the draining of stored solar heat during the summer and a continuous flux of anthropogenic heating during the winter.  相似文献   

The numerical solution of the Advection-Dispersion Equation: A review of some basic principles     

Steve Wallis 《Acta Geophysica》2007,55(1):85-94

The simulation of solute transport in rivers is frequently based on numerical models of the Advection-Dispersion Equation. The construction of reliable computational schemes, however, is not necessarily easy. The paper reviews some of the most important issues in this regard, taking the finite volume method as the basis of the simulation, and compares the performance of several types of scheme for a simple case of the transport of a patch of solute along a uniform river. The results illustrate some typical (and well known) deficiencies of explicit schemes and compare the contrasting performance of implicit and semi-Lagrangian versions of the same schemes. It is concluded that the latter have several benefits over the other types of scheme.  相似文献   

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   

A One-dimensional Ensemble Forecast and Assimilation System for Fog Prediction     

M. D. Müller  C. Schmutz  E. Parlow 《Pure and Applied Geophysics》2007,164(6-7):1241-1264

A probabilistic fog forecast system was designed based on two high resolution numerical 1-D models called COBEL and PAFOG. The 1-D models are coupled to several 3-D numerical weather prediction models and thus are able to consider the effects of advection. To deal with the large uncertainty inherent to fog forecasts, a whole ensemble of 1-D runs is computed using the two different numerical models and a set of different initial conditions in combination with distinct boundary conditions. Initial conditions are obtained from variational data assimilation, which optimally combines observations with a first guess taken from operational 3-D models. The design of the ensemble scheme computes members that should fairly well represent the uncertainty of the current meteorological regime. Verification for an entire fog season reveals the importance of advection in complex terrain. The skill of 1-D fog forecasts is significantly improved if advection is considered. Thus the probabilistic forecast system has the potential to support the forecaster and therefore to provide more accurate fog forecasts.  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   

液氮消过冷雾对冷云催化增雨的启示     

秦长学 《气象》2001,27(7):20-23

对用液氮消过冷雾和冷云催化增雨作业的宏、微观条件进行比较，找出其异同点，并根据消冷雾作业所出现的物理响应推演冷云催化后应出现的结果，以弥补飞机云中催化后缺少直接观测资料的缺陷，进而对液氮（LN）增雨效果进行探讨。  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)

ＩＮＴＲＯＤＵＣＴＩＯＮＩｔｉｓａｎａｃｋｎｏｗｌｅｄｇｅｄｆａｃｔｔｈａｔａｒａｇｏｎｉｔｅ,ａｈｉｇｈ ｐｒｅｓｓｕｒｅｐｏｌｙｍｏｒｐｈｏｆＣａＣＯ3 ,ｏｃｃｕｒｓｗｉｄｅｌｙａｓａｎｉｎｄｅｘｍｉｎｅｒａｌｏｆｈｉｇｈ ｐｒｅｓｓｕｒｅａｎｄｌｏｗ ｔｅｍｐｅｒａｔｕｒｅｍｅｔａｍｏｒｐｈｉｓｍ (ｇｌａｕｃｏｐｈａｎｅｓｃｈｉｓｔｆａｃｉｅｓ)ｗｉｔｈｉｎｔｈｅｇｅｏｄｙｎａｍｉｃｃｏｎｔｅｘｔｏｆｓｕｂｄｕｃｔｉｏｎ ｏｂｄｕｃｔｉｏｎａｎｄｃｏｎｔｉｎｅｎｔａｌｃｏｌｌｉｓｉｏｎ (Ｌｉｏｕ…  相似文献