天气雷达定量测量淮河降水实验、研究工作进展

天气雷达定量测量淮河降水实验、研究工作进展徐胜，徐慧（水利部淮委水情信息中心）１引言古往今来，人们在与自然灾害作斗争的实践中认识到，暴雨、洪水监测和预报的困难主要来自四个方面：一是情报不能及时获得，气象台站提供的每天地面四次，高空两次探测资料和水文站...

高水分小麦包装储存机械通风降水实验

高大平房仓中包装储存的高水分小麦,在没有地上笼通风设施的情况下,利用离心风机,辅以轴流风机,进行机械通风和自然通风降水,结果表明:第一阶段利用秋冬季节干燥空气进行机械通风降温降水效果明显,第二阶段的降水确保了小麦的安全度夏,此后进行保湿通风减少水分损失,可提高仓储经济效益。

云降水物理学虚拟仿真实验设计与实现

为了有效解决传统云物理实践教学中自然云雾过程不可及、不可逆和多因素影响等难点,围绕云雾降水的宏微观过程,以外场仪器观测、数据分析和数值模拟为基础,借助先进的虚拟仿真技术,递进式开发了涵盖基础操作、设计验证和综合探索3层次的虚拟仿真实验,并采用自主探究式等多种教学方法,有效地加深了学生对云降水过程知识点的掌握,切实提升了学生防灾减灾实践创新能力。

砂卵石地层深基坑降水控制系统及控制方法

文章根据砂卵石地层深基坑施工降水的特点和要求,在传统降水井施工基础上提供了一种砂卵石地层深基坑降水精确控制系统及控制方法,实现了控制的自动化和智能化。根据开挖深度变化确定合适的抽水流量、降水井组合以及工作时长,避免过度降水造成的资源浪费和安全隐患,并有效节约降水用电费用。

Experimental 15-day-lead statistical forecast of intraseasonal summer monsoon rainfall over Eastern China

This study utilizes daily Asian Precipitation–Highly-Resolved Observational Data Integration Towards Evaluation（APHRODITE）gridded rainfall and the U.S.National Centers for Environmental PredictionDepartment of Energy reanalysis II products to examine the intraseasonal oscillations（ISOs）of rainfall over Eastern China during each summer of 1996,2002,and 2006.These three cases represent three typical spatial patterns of intraseasonal rainfall anomalies over Eastern China,with the strongest intraseasonal rainfall occurring over the middle and lower Yangtze Basin,southern Yangtze Basin,and Southeast China,respectively.The intraseasonal rainfall anomalies over Eastern China are dominated by both 30–60-and 10–20-day ISOs in each summer and are further modulated by the boreal summer ISOs（BSISOs）over the entire Asian summer monsoon region.The objective of this study is thus to apply the Bayesian wavelet-banding（WB）scheme to predicting intraseasonal rainfall over Eastern China.Several key factors associated with BSISOs are selected as predictors to experimentally develop a 15-day-lead statistical forecast.The forecast results show promise for the intraseasonal rainfall anomalies over Eastern China.Correlations generally greater than or equal to 0.6 are noted between the observed and predicted ISOs of rainfall over the major intraseasonal activity centers during each of the three summers.Such a high forecasting skill on intraseasonal timescales over various areas in Eastern China demonstrates the general usefulness of the WB scheme.

Coupled modeling of land hydrology-regional climate including human carbon emission and water exploitation

Carbon emissions and water use are two major kinds of human activities. To reveal whether these two activities can modify the hydrological cycle and climate system in China, we conducted two sets of numerical experiments using regional climate model RegCM4. In the first experiment used to study the climatic responses to human carbon emissions, the model were configured over entire China because the impacts of carbon emissions can be detected across the whole country. Results from the first experiment revealed that near-surface air temperature may significantly increase from 2007 to 2059 at a rate exceeding 0.1 ~C per decade in most areas across the country; southwestern and southeastern China also showed increasing trends in summer precipitation, with rates exceeding 10 mm per decade over the same period. In summer, only northern China showed an increasing trend of evapotranspiration, with increase rates ranging from 1 to 5 mm per decade; in winter, increase rates ranging from 1 to 5 mm per decade were observed in most regions. These effects are believed to be caused by global warming from human carbon emissions. In the second experiment used to study the effects of human water use, the model were configured over a limited region-- Haihe River Basin in the northern China, because compared with the human carbon emissions, the effects of human water use are much more local and regional, and the Haihe River Basin is the most typical region in China that suffers from both intensive human groundwater exploitation and surface water diversion. We incorporated a scheme of human water regulation into RegCM4 and conducted the second experiment. Model outputs showed that the groundwater table severely declined by -10 m in 1971-2000 through human groundwater over- exploitation in the basin; in fact, current conditions are so extreme that even reducing the pumping rate by half cannot eliminate the ground- water depletion cones observed in the area. Other hydrological and climatic elements, such as soil moisture, runoff generation, air humidity, precipitation, wind field, and soil and air temperature, were also significantly affected by anthropogenic water withdrawal and consumption, although these effects could be mitigated by reducing the amount of water drawn for extraction and application.

Modeling of the Precipitation Process in a Rotating Packed Bed and Its Experimental Validation

A mixing-precipitation model based on the modified coalescence-redispersion model was presented to describe the flow,mixing,nucleation and growth in a rotating packed bed(RPB) .The model was coupled with population balance,mass balance and crystallization kinetics.It predicted well the influence of coalescence prob-ability,which represents the mixing intensity among droplets,on the particle number density,supersaturation and mean particle size of the produced precipitates.The effects of the radial thickness of packing,liquid flow rate and rotating speed on the product particle size were also investigated.The results indicate that the needed radial length of packing is short for sparingly soluble substance precipitation(about 40-50 mm in this work) ,and the mean parti-cle size of precipitates decreases with the increase of rotating speed and liquid flow rate,respectively.The validity of this model was verified by experiment on BaSO4 precipitation in RPB.

Sensitivity of Precipitation in Aqua-Planet Experiments with an AGCM

The sensitivity of precipitation was studied by conducting control aqua-planet experiments(APEs) with a model to determine atmospheric general circulation.The model includes two versions: that with a spectral dynamical core(SAMIL) and that with a finite-volume dynamical core(FAMIL).Three factors were investigated including dynamical core,time-step length,and horizontal resolution.Numerical results show that the dynamical core significantly affects the structure of zonal averaged precipitation.FAMIL exhibited an equatorial precipitation belt with a single narrow peak,and SAMIL showed a broader belt with double peaks.Moreover,the time step of the model physics is shown to affect the zonal-averaged tropical convective precipitation ratio such that a longer time step leads to more production and consumption of convective available potential energy and convection initiated away from the equator,which corresponds to equatorial double peaks of precipitation.Further,precipitation is determined to be sensitive to horizontal resolution such that higher horizontal resolution allows for more small-scale kinetic energy to be resolved and leads to a broader probability distribution of low-level vertical velocity.This process results in heavier rainfall and convective precipitation extremes in the tropics.Abstract The sensitivity of precipitation was studied by conducting control aqua-planet experiments(APEs)with a model to determine atmospheric general circulation.The model includes two versions:that with a spectral dynamical core(SAMIL)and that with a finite-volume dynamical core(FAMIL).Three factors were investigated including dynamical core,time-step length,and horizontal resolution.Numerical results show that the dynamical core significantly affects the structure of zonal averaged precipitation.FAMIL exhibited an equatorial precipitation belt with a single narrow peak,and SAMIL showed a broader belt with double peaks.Moreover,the time step of the model physics is shown to affect the zonal-averaged tropical convective precipitation ratio such that a longer time step leads to more production and consumption of convective available potential energy and convection initiated away from the equator,which corresponds to equatorial double peaks of precipitation.Further,precipitation is determined to be sensitive to horizontal resolution such that higher horizontal resolution allows for more small-scale kinetic energy to be resolved and leads to a broader probability distribution of low-level vertical velocity.This process results in heavier rainfall and convective precipitation extremes in the tropics.

Modeled Influence of East Asian Black Carbon on Inter-Decadal Shifts in East China Summer Rainfall

Two inter-decadal shifts in East China summer rainfall during the last three decades of the 20th century have been identified.One shift occurred in the late 1970s and featured more rainfall in the Yangtze River valley and prolonged drought in North China.The other shift occurred in the early 1990s and featured increased rainfall in South China.The role of black carbon(BC) aerosol in the first shift event is controversial,and it has not been documented for the second event.In this study,the authors used Geophysical Fluid Dynamics Laboratory's(GFDL's) atmospheric general circulation model known as Atmosphere and Land Model(AM2.1) ,which has been shown to capture East Asian climate variability well,to investigate these issues by conducting sensitive experiments with or without historical BC in East Asia. The results suggest that the model reproduces the first shift well,including intensified rainfall in the Yangtze River and weakened monsoonal circulation.However,the model captures only a fraction of the observed variations for the second shift event.Thus,the role of BC in modulating the two shift events is different,and its impact is relatively less important for the early 1990s event.

Developing Flow Pressure Drop and Friction Factor of Water in Copper Microchannels

Experiments of de-ionized water flowing in microchannels made in copper blocks were carried out to obtain pressure drop and friction factor and to investigate any possible discrepancies from conventional theory. Three channels with widths of 0.5 mm, 1.0 mm, 1.71 mm, a depth of 0.39 mm and a length of 62 mm were tested. For adiabatic tests, the temperature of the working fluid was maintained at 30 ℃, 60 ℃ and 90 ℃ without any heat fluxes supplied to the test section. The experimental conditions covered a range of Reynolds numbers from 234 to 3,430. For non-adiabatic tests, the inlet temperature and heat flux applied were 30 ℃ and 147 kW/m2 and only for the 0.635 mm channel. The friction factors obtained for the widest channel （Dh = 0.635 mm） are reported for both adiabatic and non-adiabatic experiments to assess possible temperature effects. The paper focuses on the effect of hydraulic diameter on pressure drop and friction factor over the experimental conditions. The pressure drop was found to decrease as the inlet temperature was increased, while the friction factors for the three test sections did not show significant differences. The experimental friction factors were in reasonable agreement with conventional developing flow theory. The effect of temperature on friction factor was not considerable as the friction factor with and without heat flux was almost the same.

EXPERIMENTS ON ASSIMILATION OF INITIAL VALUES IN NUMERICAL PREDICTION OF A WARM-SECTOR PRECIPITATION IN SOUTH CHINA

In order to understand the impact of initial conditions upon prediction accuracy of short-term forecast and nowcast of precipitation in South China, four experiments i.e. a control, an assimilation of conventional sounding and surface data, testing with nudging rainwater data and the assimilation of radar-derived radial wind, are respectively conducted to simulate a case of warm-sector heavy rainfall that occurred over South China, by using the GRAPES_MESO model. The results show that (1) assimilating conventional surface and sounding observations helps improve the 24-h rainfall forecast in both the area and order of magnitude; (2) nudging rainwater contributes to a significant improvement of nowcast, and (3) the assimilation of radar-derived radial winds distinctly improves the 24-h rainfall forecast in both the area and order of magnitude. These results serve as significant technical reference for the study on short-term forecast and nowcast of precipitation over South China in the future.

Experimental Study of Falling-film Mode Transitions between Horizontal Tubes in CaCl_2/Water Absorber

It is important to accurately predict the flow mode especially intertube falling-film mode of absorbent for its great impact on the heat and mass transfer in a horizontal tube absorber. In this paper, a test facility used to study falling-film outside horizontal tubes was built, and experiments were conducted to explore the intertube mode transi- tions with water-calcium chloride （CaC12/water） solution in quiescent surroundings. The correlations which are more suitable for predicting CaC1jwater solution intertube mode transitions were developed. In general, the transitional Re will decrease with the solution concentration increasing, and its effects increase with the transitions from droplet mode to sheet mode. Hysteresis exists in all the mode transitions, and it is more obvious for low concentration solutions. The results may be an important support for modeling, designing and operating of CaC12/water falling-film absorber.