What causes the adiabatic lapse rate?     

Trevor J McDougall  Rainer Feistel 《Deep Sea Research Part I: Oceanographic Research Papers》2003,50(12):1523-1535

The adiabatic lapse rate is commonly explained as being proportional to the work done on a fluid parcel as its volume changes in response to an increase in pressure. According to this explanation the adiabatic lapse rate would increase with both pressure and the fluid's compressibility, but this is not the case. Rather, the adiabatic lapse rate is proportional to the thermal expansion coefficient and is independent of the fluid's compressibility. Here we show that the adiabatic lapse rate is independent of the increase in the internal energy that a parcel experiences when it is compressed. We explain what is missing from the traditional explanation of the adiabatic lapse rate and we explore the thermodynamic cause of the adiabatic lapse rate. In particular, we seek to explain how the adiabatic lapse rate can be negative in cool fresh water.  相似文献   

重力梯度之地形改正方法与研究     

冯进凯  王庆宾  黄佳喜  张超 《测绘工程》2017,26(12)

简要介绍地形起伏对地面点重力梯度的影响,推导棱柱法计算重力梯度改正的严格积分公式并和积分核累加法对比验证了其正确性;将积分区域划分为中央区和远区,中央区采用严格的棱柱法进行计算,远区采用线性积分的方式逼近真实值,简化了积分过程;根据重力梯度应用的要求针对不同类型地形设定了中央区划分准则。实验表明:根据文中提出的方法和分区准则,相比于传统的积分法和棱柱法,计算速度得到提高,且精度要求相比于积分核累加法优于0.01E。  相似文献   

Analyzing the Impacts of Urban Expansion on Green Fragmentation Using Constraint Gradient Analysis   总被引：1，自引：0，他引：1  

Limin Jiao  Gang Xu  Fengtao Xiao  Yaolin Liu  Boen Zhang 《The Professional geographer》2017,69(4):553-566

Many existing gradient analysis methods are arbitrary or too simple in gradient partitioning and unsuitable for cities with irregular forms. We propose an improved gradient analysis method with urban structural features as spatial constraints to properly partition an urban area into more homogeneous buffers. Taking the Wuhan metropolitan area in China as an example, we use the improved gradient partitioning method and six landscape metrics to characterize urban expansion and green space fragmentation in 1989, 2001, and 2013 and investigate the relationship between urban green fragmentation and urban expansion using correlation analysis and regression modeling. The results show that the fragmentation of built-up area in each buffer generally decreases from 1989 to 2013, but the fragmentation of green space increases. For each time point, with growing distance from urban centers, the fragmentation of built-up area increases and green space fragmentation decreases. This shows that urbanization exerts a significant influence on fragmentation of urban green space from both a temporal and a spatial perspective. Intensive urban expansion moved outward mainly at the cost of agricultural land and resulted in more fragmented green space in the urban fringe. Further quantitative analyses show that the area ratio and fragmentation of the built-up area are statistically negatively correlated with the fragmentation of green space. The improved gradient analysis with spatial constraints can generate more homogeneous ring gradients and then lead to more reasonable results, thereby helping to better understand how urban expansion affects landscape dynamics.  相似文献   

Neolithic wooden trackways and bog hydrology     

Wil A. Casparie  Aonghus Moloney 《Journal of Paleolimnology》1994,12(1):49-64

Five wooden trackways in raised bogs located along a precipitation gradient in Northwest Europe (Ireland, England, The Netherlands and Germany), and all dated toc. 2600 cal.BC, show differences in building method related to variable hydrological conditions in the local bog surfaces. Differences in the bearing strength of the highly humified hummock-hollow surfaces can be largely attributed to differences in the climatically related water content of the peat. Water balance studies, based on current climatic data and using the concept of system-linked discharge, can explain the hydrological differences between the ombrotrophic bogs established by archaeological excavations of the wooden trackways. Active peat growth at the time of construction and building methods used indicate mean annual precipitation values similar to present reflecting the modern rainfall gradient.This publication is the fourth paper in a series of papers presented at the session on Past Climatic Change and the Development of Peatlands at the ASLO and SWS Meetings in Edmonton, Canada, May 30–June 3, 1993. Dr P. Kuhry and Dr S. C. Zoltai are serving as Guest Editors.  相似文献   

Numerical study on residual current and its impact on mass transport in the Hangzhou Bay and the Changjiang Estuary Ⅰ.A3-D joint model of the Hangzhou Bay and the Changjiang Estuary     

Zhu Shouxian  Shi Fengyan  Zhu Jianrong  Ding Pingxing 《海洋学报(英文版)》2001,20(1):1-13

A 3-D numerical model is set up in a large domain covering the Hang zhou Bay and the Changjiang Estuary based on the ECOM model in orthogonal curvilinear coordinates.The numerical schemes for baroclinic pressure gradient (BPG) terms and convective terms are improved in the paper according to the characteristics of velocity field and mass transport in the area.The model is validated by the simulations of residual current and salinity transport in the Hangzhou Bay and the Changjiang Estuary.  相似文献   

Horizontal Pressure Gradient Errors of the Monterey Bay Sigma Coordinate Ocean Model with Various Grids     

Le Ngoc Ly  Lin Jiang 《Journal of Oceanography》1999,55(1):87-97

A coastal ocean -coordinate model of Monterey Bay (MOB) with realistic bottom topography and coastlines is developed using the Princeton Ocean Model (POM) and grid generation technique (GGT) to study the horizontal pressure gradient errors associated with the MOB steep topography. The submarine canyon in MOB features some of the steepest topography encountered anywhere in the world oceans. The MOB grids are designed using the EAGEAL View and GENIE⁺⁺ grid generation systems. A grid package developed by Ly and Luong (1993) is used in this study to couple grids to the model. The MOB model is tested with both orthogonal and curvilinear nearly-orthogonal (CNO) grids. The CNO grid has horizontal resolution which varies from 300 m to 2 km, while the resolution of the orthogonal grid is uniform with x = 1.25 km and y = 1.38 km. These grids cover a domain of 180 × 160 km with the same number of grid points of 131 × 131. Vertical resolutions of 25, 35 and 45 vertical sigma levels are tested. The error in the MOB are evaluated in terms of mean kinetic energy and velocity against various grids, vertical, horizontal resolution and distributions, and bottom topography smoothing. Simulations with various grids show that GGT can be used as another tool in reducing -coordinate errors in coastal ocean modeling besides increasing resolution and smoothing bottom topography. Topographical smoothing not only reduces topographic slope, but changes realistic topography. A CNO grid with a high grid density packed along steep slopes and Monterey Submarine Canyon reduces the errors by 40% compared to a rectangular grid with the same number of grid points. The CNO grid is more efficient than the rectangular grid, since it has most of its grids over water. The simulations show that the presented MOB -coordinate model can be used with a confidence regarding horizontal pressure gradient error.  相似文献   

An Eta-Coordinate Version of the Princeton Ocean Model   总被引：1，自引：0，他引：1  

Yiyong Luo  Changlong Guan  Dexing Wu 《Journal of Oceanography》2002,58(4):589-597

The Princeton Ocean Model (POM) is widely used in both the research and real-time marine forecast communities. However, there is a single heavily criticized feature and shortcoming of POM, i.e., the pressure gradient (PG) error associated with sloping topography. To overcome this problem, in this paper we present an eta-coordinate POM (ECPOM). The eta-coordinate system was originally adopted in atmospheric numerical models and has proved to be effective in removing the large errors associated with the horizontal pressure gradient force and advection and diffusion terms along a steeply sloping topography. A familiar idealized seamount problem is used to test the PG error in the ECPOM in order to isolate errors from other sources, as is done in the literature. The model is set up so that, ideally, the ocean should be at rest forever; any development of circulation is regarded as numerically artificial. Results show that in ECPOM, errors are dramatically reduced by two orders of magnitude over a wide range of parameters. As a trade-off, the bottom boundary of the ECPOM is a stepwise instead of a continuous one, as in the sigma-coordinate POM (SCPOM). Modification of the SCPOM to the ECPOM is straightforward and minimal. Compared to the z-coordinate model, the ECPOM is numerically simpler since the eta-coordinate has a surface-following character. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The effects of acid sulphate run-off on a subtidal estuarine macrobenthic community in the Richmond River, NSW, Australia   总被引：1，自引：0，他引：1  

Corfield  Jamie 《ICES Journal of Marine Science》2000,57(5):1517-1523

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Three-dimensional modelling of soil organic carbon density and carbon sequestration potential estimation in a dryland farming region of China     

SUN Zhongxiang  BAI Huiqing  YE Huichun  ZHUO Zhiqing  HUANG Wenjiang 《地理学报(英文版)》2021,31(10):1453-1468

Soil organic carbon density(SOCD) and soil organic carbon sequestration potential(SOCP) play an important role in carbon cycle and mitigation of greenhouse gas emissions. However, the majority of studies focused on a two-dimensional scale, especially lacking of field measured data. We employed the interpolation method with gradient plane nodal function(GPNF) and Shepard(SPD) across a range of parameters to simulate SOCD with a 40 cm soil layer depth in a dryland farming region(DFR) of China. The SOCP was estimated using a carbon saturation model. Results demonstrated the GPNF method was proved to be more effective in simulating the spatial distribution of SOCD at the vertical magnification multiple and search point values of 3.0×10~6 and 25, respectively. The soil organic carbon storage(SOCS) of 40 cm and 20 cm soil layers were estimated as 22.28×10~(11) kg and 13.12×10~(11) kg simulated by GPNF method in DFR. The SOCP was estimated as 0.95×10~(11) kg considered as a carbon sink at the 20–40 cm soil layer. Furthermore, the SOCP was estimated as –2.49×10~(11) kg considered as a carbon source at the 0–20 cm soil layer. This research has important values for the scientific use of soil resources and the mitigation of greenhouse gas emissions.  相似文献   

A Perspective on the Evolution of Atmospheric Blocking Theories: From Eddy-Mean flow Interaction to Nonlinear Multiscale Interaction     

Dehai LUO  Binhe LUO  Wenqi ZHANG 《大气科学进展》2023,40(4):553-569

In this paper, we first review the research advancements in blocking dynamics and highlight the merits and drawbacks of the previous theories of atmospheric blocking. Then, the dynamical mechanisms of atmospheric blocking are presented based on a nonlinear multi-scale interaction(NMI) model. Previous studies suggested that the eddy deformation(e.g., eddy straining, wave breaking, and eddy merging) might lead to the formation and maintenance of atmospheric blocking.However, the results were specu...  相似文献