Prediction of periodically correlated processes by wavelet transform and multivariate methods with applications to climatological data     

Mitra Ghanbarzadeh  Mina Aminghafari 《Theoretical and Applied Climatology》2015,120(3-4):433-444

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Improving WRF-Hydro runoff simulations of heavy floods through the sea surface temperature fields with higher spatio-temporal resolution     

Berina Mina Kilicarslan  Ismail Yucel  Heves Pilatin  Eren Duzenli  Mustafa Tugrul Yilmaz 《水文研究》2021,35(9):e14338

This study investigates the impact of the spatio-temporal accuracy of four different sea surface temperature (SST) datasets on the accuracy of the Weather Research and Forecasting (WRF)-Hydro system to simulate hydrological response during two catastrophic flood events over the Eastern Black Sea (EBS) and the Mediterranean (MED) regions of Turkey. Three time-variant and high spatial resolution external SST products (GHRSST, Medspiration and NCEP-SST) and one coarse-resolution and time-invariant SST product (ERA5- and GFS-SST for EBS and MED regions, respectively) already embedded in the initial and the boundary conditions datasets of WRF model are used in deriving near-surface atmospheric variables through WRF. After the proper event-based calibration is performed to the WRF-Hydro system using hourly and daily streamflow data in both regions, uncoupled model simulations for independent SST events are conducted to assess the impact of SST-triggered precipitation on simulated extreme runoff. Some localized and temporal differences in the occurrence of the flood events with respect to observations depending on the SST representation are noticeable. SST products represented with higher cross-correlations (GHRSST and Medspiration) revealed significant improvement in flood hydrographs for both regions. The GHRSST dataset shows a substantial improvement in NSE (~70%), RMSE reduction up to 20%, and an increase in correlation from 0.3 to 0.8 with respect to the invariable SST (ERA5) in simulated runoffs over the EBS region. The use of both GHRSST and Medspiration SST data characterized with high spatio-temporal correlation resulted in runoff simulations exactly matching the observed runoff peak of 300 m³/s by reducing the overestimation seen in invariable SST (GFS) in the MED region. Improved precipitation simulation skills of the WRF model with the detailed SST representation show that the hydrographs of GHRSST and Medspiration simulations show better performance compared to the simulated hydrographs by observed precipitation.  相似文献   

Total Hg concentrations in stream and lake sediments: Discerning geospatial patterns and controls across Canada   总被引：1，自引：0，他引：1  

Mina NasrJae Ogilvie  Mark CastonguayAndy Rencz  Paul A. Arp 《Applied Geochemistry》2011,26(11):1818-1831

This article presents an analysis of Geological Survey of Canada (GSC) open-file data for total Hg concentrations (THg) in stream and lake sediments at 142,028 sampling locations. This analysis was done for select survey zones across Canada, with emphasis on discerning THg-relevant geographic, geological, atmospheric and topographic controls. THg was generally highest in areas affected by mining and smelting, followed by areas with high metallogenic source locations. Background levels for THg were elevated in the more populated areas along the south, but dropped toward the remote and coldest locations in the east, north and west. This trend was correlated (R² = 0.74; P < 0.0001) with the 2005 GRAHM projections (Global/Regional Atmospheric Heavy Metals Model) for atmospheric Hg deposition (zones and locations with major geogenic sources and mining activities removed). Mean THg was higher for upland lakes (100.9 ± 0.5 SE, ppb) and streams (71.7 ± 0.6 SE, ppb) than for lowland lakes (94.4 ± 0.86 SE, ppb) and streams (64.2 ± 1.26 SE, ppb). The east-central portion of the Yukon Territory (Selwyn Basin) was analyzed in further detail. Here, THg within the sediments increased with increasing loss-on-ignition and increasing trace-element concentrations, and decreased with an increasing wet-area component per catchment above the sediment sampling locations. The characterization and quantification of these Hg trends is important for modeling and mapping health risks to ecosystems and communities across Canada and elsewhere.  相似文献   

2013年3月19日江西省冰雹天气成因分析   总被引：2，自引：0，他引：2  

金米娜  陈云辉  许爱华  郭艳  陈娟 《湖北气象》2013,(2):158-166

利用常规观测资料和卫星、雷达、自动站等非常规观测资料以及NCEP再分析资料,对2013年3月19日江西省大范围冰雹天气过程形成原因进行分析。结果表明,该过程是在有利的环境条件下发生的：对流层中低层强热力不稳定和强动力不稳定为冰雹生成和增长提供了不稳定机制;暖湿边界层偏南风急流和低层西南急流以及中层“干”西南急流对热力不稳定和动力不稳定机制发展有重要贡献;适宜的0℃层和-20℃层高度有利于冰雹增长。江西北部冰雹天气是在边界层有锋面逆温的条件下发生的,为“高架雷暴”类对流,南部冰雹天气是在边界层有较强暖平流的条件下发生的,为非“高架雷暴”类对流,两类对流的边界层温度层结分布差异明显。与历史同类个例比较发现,假相当位温垂直变化不仅能表征条件不稳定发展程度,对雷雨大风类强对流天气的判断也有一定参考意义。  相似文献   

The excitation, propagation and dissipation of waves in accretion discs: the non-linear axisymmetric case     

M. R. Bate  G. I. Ogilvie  S. H. Lubow  J. E. Pringle 《Monthly notices of the Royal Astronomical Society》2002,332(3):575-600

We analyse the non-linear propagation and dissipation of axisymmetric waves in accretion discs using the ZEUS-2D hydrodynamics code. The waves are numerically resolved in the vertical and radial directions. Both vertically isothermal and thermally stratified accretion discs are considered. The waves are generated by means of resonant forcing, and several forms of forcing are considered. Compressional motions are taken to be locally adiabatic  ( γ =5/3)  . Prior to non-linear dissipation, the numerical results are in excellent agreement with the linear theory of wave channelling in predicting the types of modes that are excited, the energy flux by carried by each mode, and the vertical wave energy distribution as a function of radius. In all cases, waves are excited that propagate on both sides of the resonance (inwards and outwards). For vertically isothermal discs, non-linear dissipation occurs primarily through shocks that result from the classical steepening of acoustic waves. For discs that are substantially thermally stratified, wave channelling is the primary mechanism for shock generation. Wave channelling boosts the Mach number of the wave by vertically confining the wave to a small cool region at the base of the disc atmosphere. In general, outwardly propagating waves with Mach numbers near resonance  ℳ_r≳0.01  undergo shocks within a distance of order the resonance radius.  相似文献   

The evolution of a warped disc around a Kerr black hole     

S. H. Lubow  G. I. Ogilvie  J. E. Pringle 《Monthly notices of the Royal Astronomical Society》2002,337(2):706-712

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On the wake generated by a planet in a disc     

G. I.Ogilvie  S. H.Lubow 《Monthly notices of the Royal Astronomical Society》2002,330(4):950-954

A planet of low mass orbiting in a two-dimensional gaseous disc generates a one-armed spiral wake. We explain this phenomenon as the result of constructive interference between wave modes in the disc, somewhat similar to the Kelvin wedge produced in the wake of a ship. The same feature is not expected in a three-dimensional disc with thermal stratification.  相似文献   

Excursion guide 13: The Permo-Triassic sandstones of Morayshire, Scotland     

S. Ogilvie  K. Glennie  & C. Hopkins 《Geology Today》2000,16(5):185-190

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Solar wind observations with the ion composition instrument aboard the ISEE-3/ICE spacecraft     

K. W. Ogilvie  M. A. Coplan  P. Bochsler  J. Geiss 《Solar physics》1989,124(1):167-183

In this paper we use the observations of solar wind helium ions made by the Ion Composition Instrument (ICI) on the ISEE-3/ICE spacecraft to study the variation of helium abundance in the solar wind and to arrive at an average value of that quantity for the period August 1978 to December 1982. The abundance varies in a similar way to that observed in the previous solar cycle, but more detailed dependence on velocity and solar cycle epoch is observed. The long-term average helium abundance is used in conjunction with long term abundances of ³He, O, Ne, Si, and Fe, measured with respect to helium using the same instrument, to compile abundances with respect to hydrogen which can be reliably compared with solar system abundances. With the extended data set we are able to show Si and Fe to be overabundant by a factor of three with respect to solar system abundances and He underabundant by a factor of two.  相似文献   

Magnetic and thermal pressures in the solar wind   总被引：1，自引：0，他引：1  

L. F. Burlaga  K. W. Ogilvie 《Solar physics》1970,15(1):61-71

Explorer 34 solar wind data for the period June to December, 1967 show that(a) The magnetic pressure, P _BB ²/8, and thermal pressure,P _kn _p kTp+n kT+n _e kTe,are variable and positively correlated on a scale of 2 days, but (b) changes in P _b and P _k are anticorrelated on a scale 1 hr (0.01 AU). Thus, dynamical hydromagnetic processes (dv/dto) must occur on the mesoscale, but the solar wind tends to be in equilibrium(P _B+P _Kconstant) on a smaller scale, the microscale. The 3-hr averages show that the most probable value of P _{k/P B} is =1.0±0.1, which implies that the most probable state of the solar wind at 1 AU is not one of equipartition between the thermal energy and magnetic energy. The average total pressure for a given bulk speed(P(V)=P ^k+P _k+P _B) is essentially independent of V, implying that P is not determined by the heating or acceleration mechanisms of the solar wind; the average pressure is P=(2.9±1.5)×10^-10dyne/cm².  相似文献