Improving long-lead seasonal forecasts of precipitation over Southern China based on statistical downscaling using BCC_CSM1.1m     

《Dynamics of Atmospheres and Oceans》2021

Long-lead precipitation forecasts for 1–4 seasons ahead are usually difficult in dynamical climate models due to the model deficiencies and the limited persistence of initial signals. But, these forecasts could be empirically improved by statistical approaches. In this study, to improve the seasonal precipitation forecast over the southern China (SC), the statistical downscaling (SD) models are built by using the predictors of atmospheric circulation and sea surface temperature (SST) simulated by the Beijing Climate Center Climate System Model version 1.1 m (BCC_CSM1.1 m). The different predictors involved in each SD model is selected based on both its close relationship with the target seasonal precipitation and its reasonable prediction skill in the BCC_CSM1.1 m. Cross and independent validations show the superior performance of the SD models, relative to the BCC_CSM1.1 m. The temporal correlation coefficient of SD models could reach > 0.4, exceeding the 95 % confidence level. The SC precipitation index can be much better forecasted by the SD models than by the BCC_CSM1.1 m in terms of the interannual variability. In addition, the errors of the precipitation forecast in all four seasons are significantly reduced over most of SC in the SD models. For the 2015/2016 strong El Niño event, the SD models outperform the dynamical BCC_CSM1.1 m model on the spatial and regional-average precipitation anomalies, mostly due to the effective SST predictor in the SD models and the weak response of the SC precipitation to El Niño-related SST anomalies in the BCC_CSM1.1 m.  相似文献   

概率密度匹配方法在我国近海海面10 m风速预报中的应用     

胡海川  赵伟  董林 《热带气象学报》2021,37(1):91-101

海面风速对航运及海上生产作业影响重大,但数值模式对于海面的风速预报仍存在较大误差。为降低数值模式海面10 m风速预报的系统性误差,提高海上大风预报准确率,基于2017—2019年中国气象局地面气象观测资料对ECMWF确定性模式的10 m风场预报结果进行检验评估,并采用概率密度匹配方法对模式误差进行订正。分析结果表明,概率密度匹配方法可有效地改善数值模式10 m风速预报的系统性误差,订正后风速在各个预报时效和风速量级的平均误差均较订正前有所降低。对于大量级风速的预报,经概率密度匹配方法订正后的风速预报的漏报率可减少10%以上。订正后12 h预报时效的8、9级风速预报的平均绝对误差分别由4.15 m/s、5.61 m/s降低至3.12 m/s、4.08 m/s,120 h预报时效的8、9级风速预报的平均绝对误差由7.38 m/s、9.35 m/s减小至6.46 m/s、8.07 m/s。在冷空气、台风大风天气过程中,基于概率密度匹配方法订正后的风速与实况观测更接近,能够为我国近海洋面10 m风速的预报提供更准确的参考。   相似文献   

Modeling Atmospheric Chemistry: Interactions between Gas-Phase Species and Liquid Cloud/Aerosol Particles     

Rolf Sander 《Surveys in Geophysics》1999,20(1):1-31

For detailed modeling of atmospheric chemistry it is necessary to consider aqueous-phase reactions in cloud droplets and deliquesced aerosol particles. Often, the gas-phase concentration is in equilibrium with the aqueous phase. Then Henrys law can be used to describe the distribution between the phases provided that the Henrys law coefficient is known. In some cases, thermodynamic equilibrium will not be reached and it is necessary to use kinetic expressions of the rates involved. These rates depend on diffusion constants, accommodation coefficients, Henrys law coefficients, particle size distributions, and several other parameters. This review describes how these processes can be treated in computer modeling and how the necessary data can be obtained. Even though it is written primarily for use in modeling atmospheric chemistry, some parts will also be useful for waste water and pesticide control and in other areas where the distribution of chemicals between the aqueous and the gas phase is important.  相似文献   

承受负摩擦力的桩基沉降计算的迭代法   总被引：12，自引：1，他引：11  

赵锡宏  张启辉  张保良 《岩土力学》1999,20(2):17-21

结合负摩擦力产生的机理,认为软土地区的桩基的负摩擦力问题主要是沉降问题,而不是强度问题。利用半理论半经验的桩基沉降计算方法［１］ ,对承受负摩擦力的桩基的中性点及桩基的沉降、桩的分担比进行简单的迭代计算,由此可确定承受负摩擦力的桩基的沉降,计算结果与实测结果的对比表明,该法简单可行。  相似文献   

The Speciation of (CH3)2Sn2+ in Electrolyte Solution Containing the Major Components of Natural Waters     

Claudia Foti  Antonio Gianguzza  Frank J. Millero  Silvio Sammartano 《Aquatic Geochemistry》1999,5(4):381-398

Hydrolysis constants of dimethyltin(IV) cation, in different salt solutions (CaCl₂: 0.15 I 0.90; MgCl₂: 0.30 I 0.60; NaCl-–NaClO₄, NaCl-–NaNO₃ mixtures: I = 3; NaCl-–Na₂SO₄ mixtures: I = 1 mol dm^-3) were determined by potentiometric ([H⁺]-glass electrode) measurements. These data, together with previous data (De Stefano et al., 1996b) were interpreted in terms of DHT (Debye–Hückel type) and Pitzer equations. The mixed electrolyte solution results also allowed us to obtain and parameters for the Pitzer equation. Calorimetric measurements were made at different ionic strengths in order to find the temperature dependence of hydrolysis constants and of the relative interaction parameters. The body of results allows us to determine the speciation of natural waters in a wide range of ionic strengths and temperatures.  相似文献   

Obtaining the free frequencies of the non‐rigid Earth     

Juan Getino  José M. Farto  José M. Ferrándiz 《Celestial Mechanics and Dynamical Astronomy》1998,71(2):95-108

In this paper, the mathematical algorithm elaborated by González, Getino and Farto (1998) is applied to four different nonrigid Earth models, in order to obtain the analytical expressions of the corresponding free frequencies. The solutions are studied, and the contributions of the different considered effects are evaluated. A numerical integration is also carried out, showing the validity of the obtained analytical solutions.  相似文献   

Average attenuation of 0.7–5.0  Hz Lg waves and magnitude scale determination for the region bounding the western branch of the East African Rift     

Richard W. Ferdinand 《Geophysical Journal International》1998,134(3):818-830

The investigation of L g attenuation characteristics in the region bounding the western branch of the East African rift system using digital recordings from a seismic network located along the rift between Lake Rukwa and Lake Malawi is reported. A set of 24 recordings of L g waves from 12 regional earthquakes has been used for the determination of anelastic attenuation, Q _Lg , and regional body-wave magnitude, m _{b Lg} , scale. The events used have body-wave magnitudes, m _b , between 4.6 and 5.5, which have been determined teleseismically and listed in ISC bulletins. The data were time-domain displacement amplitudes measured at 10 different frequencies (0.7–5.0  Hz). Q _Lg and its frequency dependence, η , in the region can be represented in the form Q _Lg = (186.2 ± 6.5)  f  ^(0.78±0.05). This model is in agreement with models established in other active tectonic regions. The L g -wave-based magnitude formula for the region is given by m _{b Lg} = log   A + (3.76 ± 0.38)  log   D − (5.72 ± 1.06), where A is a half-peak-to-peak maximum amplitude of the 1  s L g wave amplitude in microns and D is the epicentral distance in kilometres. Magnitude results for the 12 regional earthquakes tested are in good agreement with the ISC body-wave magnitude scale.  相似文献   

Quaternary changes in delivery and accumulation of organic matter in sediments of Lake Biwa, Japan     

Philip A. Meyers  Keiji Takemura 《Journal of Paleolimnology》1997,18(3):211-218

A 911-m-long sediment core from Lake Biwa, Japan, provides a record of organic matter delivery and accumulation in this large lake during a succession of tectonic and climatic changes dating back to the latest Pliocene. Sediments deposited since 430 ky are profundal; older sediments vary in setting between shallow-water and fluviodeltaic conditions, with occasional deep-water intervals. C/N ratios identify algal production as the dominant source of organic matter throughout the core, although the proportion of land-derived contributions episodically increases in the fluviodeltaic and shallow-water sediments. Rates of organic matter delivery and burial in lake sediments change in response to glacial-interglacial climate changes over the past 430 ky. Sediments deposited during interglacial intervals have organic carbon mass accumulation rates up to 9 times greater than those from glacial intervals, reflecting interglacial climates that were wetter than glacial climates. Algal production of organic matter increased during interglacial times because of greater wash-in of soil nutrients, and organic matter preservation was enhanced because of faster sedimentation rates.  相似文献   

Winnie(1997)和Bilis(2000)变性过程的湿位涡分析   总被引：29，自引：8，他引：29       下载免费PDF全文

李英  陈联寿  雷小途 《热带气象学报》2005,21(2):142-152

9711号台风Winnie和0010号台风Bills均在中国大陆发生变性，但前者变性后再度加强，而后者变性后减弱消亡。从湿位涡理论出发，对比分析两者的变性过程，结果表明：作为变性台风，Winnie和Bilis均在北上过程中与中纬度西风槽发生作用，但前者与高空槽发生耦合，后者仅接近高空槽底部，没有发生耦合；Winnie变性加强过程表现为一个温带气旋在低层锋区上的强烈发展过程，主要与高层正位涡扰动下传、低层锋区及热带气旋低压环流之间的相互作用有关。Pm湿斜压项增长引起的倾斜涡度发展是登陆热带气旋变性加强的主要因子。在Bills变性过程中，高层无明显的正位涡扰动下传，热带气旋低压环流内无锋区面出现，大气斜压性弱且变化不明显。  相似文献   

1米太阳望远镜液压监控系统     

赵雪娟  柳光乾  张涛 《云南天文台台刊》2012,(2):162-167

1m太阳望远镜的方位驱动控制系统采用液压轴承,液压系统正常工作时望远镜才能实现平稳旋转。可通过油压、油温监测液压系统的工作状态。针对原有液压系统不能提供其工作状态实时监测和自动化程度较低的缺陷,设计了液压监控系统并将其集成到望远镜控制系统中,可实现油压油温数据采集、油压异常报警、油泵自动启停等功能,保证液压轴承的安全运转。介绍了该监控系统的结构和工作原理,阐述了油压、油温数据采集系统的软硬件实现并给出了相应的实验数据和运行结果。理论分析和实验结果表明系统工作正常,数据采集速度快、分辨率高,精度可满足要求,能长期稳定运行。  相似文献