Integrated water vapor during active and break spells of monsoon and its relationship with temperature,precipitation and precipitation efficiency over a tropical site

Global Positioning System(GPS)measurements of integrated water vapor(IWV)for two years(2014 and 2015)are presented in this paper.Variation of IWV during active and break spells of Indian summer monsoon has been studied for a tropical station Hyderabad(17.4°N,78.46°E).The data is validated with ECMWF Re-Analysis(ERA)91 level data.Relationships of IWV with other atmospheric variables like surface temperature,rain,and precipitation efficiency have been established through cross-correlation studies.A positive correlation coefficient is observed between IWV and surface temperature over two years.But the coefficient becomes negative when only summer monsoon months(June,July,August,and September)are considered.Rainfall during these months cools down the surface and could be the reason for this change in the correlation coefficient.Correlation studies between IWV-precipitation,IWVprecipitation efficiency(P.E),and precipitation-P.E show that coefficients are-0.05,-0.10 and 0.983 with 95%confidence level respectively,which proves that the efficacy of rain does not depend only on the level of water vapor.A proper dynamic mechanism is necessary to convert water vapor into the rain.The diurnal variations of IWV during active and break spells have been analyzed.The amplitudes of diurnal oscillation and its harmonics of individual spell do not show clear trends but the mean amplitudes of the break spells are approximately double than those of the active spells.The amplitudes of diurnal,semidiurnal and ter-diurnal components during break spells are 1.08 kg/m^(2),0.52 kg/m;and 0.34 kg/m;respectively.The corresponding amplitudes during active spells are 0.68 kg/m^(2),0.41 kg/m;and 0.23 kg/m;.

Precipitation efficiency and its relationship to physical factors

The precipitation efficiency and its relationship to physical factors are examined by analyzing a two-dimensional cloud-resolving model simulation during TOGA COARE in this study. The basic physical factors include convective avail- able potential energy, water-vapor convergence, vertical wind shear, cloud ratio, sea surface temperature, air temperature, and precipitable water. Precipitation efficiencies do not show a close relationship to air temperature nor to sea surface tem- perature nor to precipitable water. The precipitation efficiency increases as the water-vapor convergence rate increases and vertical wind shear weakens, whereas it decreases as the convective available potential energy dissipates and anvil clouds develop.

Spatial distribution of atmospheric water vapor and its relationship with precipitation in ,summer over the Tibetan Plateau

By using the observed monthly mean temperature and humidity dat, asets of 14 ra- diosonde stations and monthly mean precipitation data of 83 surface station., from 1979 to 2008 over the Tibetan Plateau （TP）, the relationship between the atmospheric water vapor （WV） and precipitation in summer and the precipitation conversion efficiency IPEC） over the TP are analyzed. The results are obtained as follows. （1） The summer WV decreases with increasing altitude, with the largest value area observed in the northeastern part of the TP, and the second largest value area in the southeastern part of the TP, while the northwestern part is the lowest value area. The summer precipitation decreases from southeast to north- west. （2） The summer WV presents two main patterns based on the EOF analysis： the whole region consistent-type and the north-south opposite-type. The north-south opposite-type of the summer WV is similar to the first EOF mode of the summer precipitation and both of their zero lines are located to the north of the Tanggula Mountains. （3） The summer precipitation is more （less） in the southern （northern） TP in the years with the distribution of deficient summer WV in the north while abundant in the south, and vice versa. （4） The PEC over the TP is between 3% and 38% and it has significant spatial difference in summer, which is obviously bigger in the southern TP than that in the northern TP.

Gas exchange of Populus euphratica leaves in a riparian zone

Riparian vegetation belts in arid regions of Central Asia are endangered to lose their ecosystem services due to intensified land use.For the development of sustained land use,management knowledge of plant performance in relation to resource supply is needed.We estimated productivity related functional traits at the edges of the habitat of Populus euphratica Oliv.Specific leaf area （SLA） and carbon/nitrogen （C/N） ratio of P.euphratica leaves growing near a former river bank and close to moving sand dunes in the Ebinur Lake National Nature Reserve in Xinjiang,Northwest China （near Kazakhstan） were determined and daily courses of CO2 net assimilation （PN）,transpiration （E）,and stomatal conductance （gs） of two consecutive seasons were measured during July-August 2007 and June-July 2008.Groundwater level was high （1.5-2.5 m below ground） throughout the years and no flooding occurred at the two tree stands.SLA was slightly lower near the desert than at the former river bank and leaves contained less N in relation to C.Highest E and gs of P.euphratica were reached in the morning before noon on both stands and a second low maximum occurred in the afternoon despite of the unchanged high levels of air to leaf water vapor pressure deficit （ALVPD）.Decline of gs in P.euphratica was followed by decrease of E.Water use efficiency （WUE） of leaves near the desert were higher in the morning and the evening,in contrast to leaves from the former river bank that maintained an almost stable level throughout the day.High light compensation points and high light saturation levels of PN indicated the characteristics of leaves well-adapted to intensive irradiation at both stands.In general,leaves of P.euphratica decreased their gs beyond 20 Pa/kPa ALVPD in order to limit water losses.Decrease of E did not occur in both stands until 40 Pa/kPa ALVPD was reached.Full stomatal closure of P.euphratica was achieved at 60 Pa/kPa ALVPD in both stands.E through the leaf surface amounted up to 30％ of the highest E rates,indicating dependence on water recharge from the ground despite of obviously closed stomata.A distinct leaf surface temperature （Tleaf） threshold of around 30℃ also existed before stomata started to close.Generally,the differences in gas exchange between both stands were small,which led to the conclusion that micro-climatic constraints to E and photosynthesis were not the major factors for declining tree density with increasing distance from the river.

基于GNSS/MET的宁夏大气水汽分布及其与降水关系研究

为科学合理开发宁夏空中水资源,提升人工增雨作业效率和水平,摸清宁夏空中水资源时空变化特征及水汽变化与降水的关系,利用2014年1月—2020年12月宁夏23个全球导航卫星系统大气探测(GNSS/MET)站、地面自动气象站及银川市和平凉市探空站气象资料,采用统计诊断和对比分析方法,检验评估了GNSS/MET资料在宁夏不同地区的适用性,分析了宁夏大气水汽含量的时空变化特征及其与降水的关系,建立了宁夏大气水汽含量人工增雨作业指标,并对不同降水强度下的降水转化率进行了初步分析。结果表明:(1)GNSS/MET资料和探空观测数据反演得出的大气水汽含量间的相关系数为0.80~0.92,两者之间的相关性随天气过程中降水量的增大呈减小趋势,GNSS/MET资料反演的大气水汽含量在宁夏具有较好的代表性和适用性。(2)受东亚夏季风年变化影响,宁夏整层大气水汽含量夏季的最大,秋春季的次之,冬季的最小;8月大气水汽含量最大,12月大气水汽含量最小。受季风边缘区位置年际波动、六盘山和贺兰山地形抬升作用影响,宁夏大气水汽含量月均值呈现出南部和北部地区的波动较大、中部地区的波动较小的显著特征。(3)宁夏1—12月适宜人工增雨作业的大气水汽含量指标分别为4.9~7.0 mm、7.6~10.0 mm、12.7~17.8 mm、16.6~19.1 mm、22.4~25.7 mm、28.0~32.7 mm、36.2~42.0 mm、34.9~44.0 mm、27.5~32.5 mm、19.2~21.0 mm、10.4~14.5 mm、5.0~8.8 mm。(4)受到纬度、六盘山地形及西南季风等影响,六盘山西侧及宁夏最东侧的盐池大气水汽降水转化率较高;与腾格里沙漠、毛乌素沙地等相邻的宁夏中部的西部地区和北部的东部地区可能受到沙尘等影响,大气水汽降水转化率低。

半干旱区雨养春小麦蒸腾效率的计算与应用

与作物叶片水平的蒸腾效率研究相比,由于群体蒸腾量难以直接测量,作物产量水平的蒸腾效率往往不被重视。本研究根据文献中所给出的产量水平的小麦蒸腾效率与自由水面蒸发量之间的关系,依据文献数据、田间试验观测资料以及桶栽试验观测资料,建立黄土高原西端半干旱区雨养春小麦产量与耗水量之间的关系,并计算获得了该区1987-2011年春小麦蒸腾效率,从而模拟了该区春小麦水分利用效率的变化。结果表明,半干旱区雨养春小麦耗水量与产量呈极显著的线性关系(P<0.01),不受不同年份气候条件、供水变化以及作物品种的影响。春小麦蒸腾效率平均为16.301 kg/(hm^(2)·mm),土壤水分蒸发量平均为156 mm。而依据自由水面蒸发量推算每年的春小麦蒸腾效率,所获得的蒸散量与实测产量关系符合该地区文献记录的耗水量与产量关系,论证了蒸腾效率在不同地区相同作物中的保守性特点。同时依据桶栽试验观测所得的胞间二氧化碳浓度与大气二氧化碳浓度比值与生育期平均空气饱和差之间的关系,修订已有的研究公式,能够模拟所研究地区的春小麦水分利用效率。本研究结果可为半干旱区雨养春小麦产量的提高及水资源的高效利用提供可借鉴的依据。

山东省某滨海核电厂可能最大降雨分析计算

可能最大降雨(Probable Maximum Precipitation,PMP)是评价核电厂防洪安全和排水系统设计的重要参数。在分析山东省某滨海核电厂厂址区域暴雨特性和天气成因的基础上,采用当地暴雨放大方法(水汽放大法和水汽效率放大法)和暴雨移置放大法推求出厂址24 h PMP。通过计算方案的合理性检查,对比山东省可能最大24 h点降雨量等值线图和其他核电厂工程24 h PMP成果,经综合分析确定该厂址24 h PMP为1100.0 mm,研究成果可为全国类似流域的PMP研究提供参考和借鉴。

石羊河流域水分利用效率及其对饱和水汽压差的响应

水分利用效率(WUE)是叶片通过光合作用调节水分生理过程的指标,是联系生态系统碳循环与水循环关系的关键,反映了植被生态系统对立地环境快速调整和资源的变化适应策略。基于卫星遥感和地面观测数据,利用光能利用率模型和蒸散发经验估算模型,模拟石羊河流域2000—2019年植被总初级生产力(GPP)和蒸散发(ET)数据,估算2000—2019年不同植被类型的WUE空间分布特征,研究GPP/ET/WUE与饱和水汽压差(VPD)的相关性,探讨干旱区不同类型植被对水分利用及胁迫的适应策略。结果表明:(1)2000—2019年石羊河流域植被WUE、GPP和ET的平均值分别为0.80 gC m^(-2)mm^(-1)、256.52 gC/m2和302.52 mm,其三者的空间分布特征表现为“南高北低”,即由流域源头至下游逐渐减少的空间分布。(2)近20年内,流域内WUE、GPP和ET的变化率的平均值分别为0.017 gC m^(-2)mm^(-1)a^(-1),6.99 gC m-2a^(-1)和3.80 mm/a,流域总体呈现波动上升的趋势,但城区和民勤耕地-荒漠交接区呈不同程度的减少趋势。(3)流域内不同类型植被的WUE平均值关系为:森林>农作物>草地>灌丛>荒漠植被>湿地植被,WUE增加速度的平均值关系为:农作物>森林>草地>灌丛>荒漠植被>湿地植被,与GPP基本一致,其中ET在灌丛、荒漠植被、湿地植被地区呈现降低趋势。(4)研究区内GPP/ET/WUE与VPD相关性的空间分布特征与石羊河径流方向具有高度一致性,WUE与VPD相关性分布特征受土地利用以及径流方向影响显著。WUE与VPD呈正相关的区域主要分布在河西走廊绿洲东部和荒漠区东部,呈负相关区域主要分布在祁连山高海拔地区、河西走廊绿洲中部和荒漠区西部。因此,正确揭示内陆河植被GPP/ET/WUE的空间分异以及变化趋势及其对驱动因素VPD的响应,是了解流域尺度中干旱区植被对全球干旱加剧的适应性策略前提,进而为生态保护提供决策服务。

Water, heat fluxes and water use efficiency measurement and modeling above a farmland in the North China Plain

Net radiation (Rn), water vapor flux (LE), sensible heat flux (Hs) and soil heat flux (G)were measured above a summer maize field with the eddy-covariance technique, simulation and analysis of water, heat fluxes and crop water use efficiency were made with the RZ-SHAW model at the same time in this study. The results revealed significant diurnal and seasonal variability of water vapor flux for summer maize. Most part of Rn was consumed by the evapotranspiration of the summer maize. The proportion of water vapor flux to net radiation ((LE/Rn) increased with the crop development and peaked around milk-filling stage with a value of 60%, a slightly lower than that obtained by the RZ-SHAW model. Daily evapotranspiration estimated by the model agreed with the results measured with the eddy-covariance technique, indices of agreement (IA) for hourly water vapor fluxes simulated and measured were above 0.75, root mean square errors (RMSE) were no more than 1.0. Diurnal patterns of Hs showed the shape of inverted "U" shifted to the forenoon with a maximum value around 11:30 (Beijing time), while LE exhibited an inverted "V" with a maximum value at around 13:00, about an hour later than Hs. Diurnal change of CO2showed an asymmetrical "V" curve and its maximal rates occurred at about 11:30. Variations of water use efficiency during the phonological stages of the summer maize showed a rapid increase with the photosynthetic photon flux density (PPFD) after sunrise, a state of equilibrium around 10:00 followed a decrease. Maximum values of water use efficiency were 24.3, and its average value ranged from 7.6 to 10.3 g kg-1.

水浴式气化器设计技术改造

随着QY-1 200/30液氩立式水浴蒸汽气化器运行时间增长,效率下降,多次发生气化器底部因温度过低而结冰的异常现象,存在设备损坏风险。通过对气化器改造,改高温区溢流外排为低温区溢流外排,增加气化器底部排污清洁功能,减少了外排水热量损失,降低了蒸汽消耗量,提升了换热效率。

祁连山-黑河流域水循环中的大气过程

利用气象台站探空资料、地面观测资料和NCEP/NCAR再分析气候资料,分析了祁连山 黑河流域水循环中的大气过程,结果表明:受西风带波动影响的水汽来源贫乏是此区大气水汽含量少的原因之一;水汽输送通量辐散是此区大气水汽含量少的原因之二;就年平均而言,祁连山 黑河流域大气水汽含量仅为高湿的江南地区的20%,为半干旱区的华北中部的约40%;高海拔的祁连山区因降水效率高,地面蒸发量小,地表水物质易于聚积形成径流;黑河流域因降水效率低,降水量值与地面蒸发量值相当,对地表水的贡献很小。在祁连山 黑河流域2 5°×2 5°区域上空,大气年输入水量为6678亿m3,输出为6502亿m3,净输入水量为176亿m3;输入水汽呈逐年减少的趋势。20世纪70～80年代有明显的下降,近40年来祁连山 黑河流域的气温在升高,大气中的水汽含量在减少,降水量的减少将难以避免。

山东夏季空中水汽分布和水汽输送特征

利用山东省气象站的降水量资料和JRA-55、NCEP/NCAR再分析资料,分析了1962-2016年山东夏季整层大气可降水量、降水转化率、水汽通量及输送路径的分布特征和变化规律,探讨了夏季降水与水汽通量及其散度的相关性和多雨年的水汽来源。结果表明:从常年值来看,山东平均夏季降水量为401.2 mm,大气可降水量为3478.8 mm,降水转化率为11.5%。降水转化率和降水量的时空演变特征更加一致,经向水汽输送和局地水汽通量散度与地面有效降水的关系更加密切,当大气可降水量充沛、外部水汽输送充足并出现局地水汽辐合时,更加有利于山东南部地区降水的发生发展,从而形成夏季降水量和降水转化率气候特征表现出东南地区大于西北地区的空间分布型态。西北太平洋、南海、孟加拉湾和鄂霍茨克海至日本海是造成山东夏季降水异常偏多的重要水汽源地,巴尔喀什湖至贝加尔湖地区是重要的冷空气输送区域;当山东上游盛行偏西风时,自新疆和青藏高原至内蒙古的狭长带出现异常水汽扰动并发展,是由水汽异常引起的水汽通量异常对山东局地降水异常贡献的主要条件。

河南“21·7”特大暴雨水汽输送、收支和转化特征对局地强降水的影响机制研究

针对河南“21·7”特大暴雨的极端降水天气过程,利用FNL大气再分析资料、国家基准站降水观测数据和高分辨率的数值模拟结果,开展了暴雨多尺度系统协同作用下水汽输送、收支及转化特征对极端降水的影响机制研究。结果表明:通过强盛稳定的台风烟花与中高纬稳定的大气环流形势共同影响下建立的远距离水汽输送通道,使海上的水汽源源不断地被输送到内陆极端降水区。在局地中尺度低值系统产生的动力辐合和迎风坡地形的阻挡作用的共同影响下,远距离输送到极端降水区附近的水汽被有效地汇聚在极端降水区附近,并且依靠低层水汽动力辐合机制,使局地汇聚的水汽被进一步输送至对流层中高层,以此促进对流的发展。在对流上升运动和迎风坡地形抬升作用的共同影响下,通过增强气流的垂直上升运动,使更多的水汽被输送到对流层中高层,促使水汽向云冰粒子和雹粒子的凝华转换过程增强,最终导致降水效率得到显著提升,降水效率在地形迎风坡处显著增强表征的水汽向雨水的高效转化,对极端降水的演变起到了极好的指示作用。上述研究不仅系统性揭示了暴雨多尺度系统影响下极端降水区内局地水汽的主要来源与消耗过程,而且从水汽诊断的角度加深了对极端降水发生机理的认识。

单螺杆水蒸汽压缩机驱动的MVR系统性能实验研究

将单螺杆水蒸汽压缩机应用于机械蒸汽再压缩热泵(MVR)系统,并对该压缩机的工作过程进行分析;在不同蒸发温度的工况下,对采用闭式和开式循环的MVR系统进行实验研究.实验结果表明,当蒸发温度高于80℃时,压缩机的容积效率超过0.73,绝热内效率大于0.5;系统的实际COP最高达12.5,实际单位能耗蒸发水量最高可达20 kg/(k W·h);充分显示了单螺杆水蒸汽压缩机驱动MVR系统的高效节能特性.

山东省飞机增雨天气系统云水资源转化特征分析

利用水汽辐合法和水汽凝结法 ,对山东省 1997～ 1999年春秋季 18个降水过程的水汽辐合率、凝结率及降水效率等表征云水资源及其转化的特征量进行计算。分析了南方气旋、西北冷锋等主要降水天气系统以上特征量的地域分布和差别。

天山及周边地区空中水资源的稳定性及可开发性研究

利用计算的天山及周边地区大气含水量序列的方差值和降水转化率,分析了天山地区空中水资源的稳定性和可开发性。结果表明:空中水资源的稳定性与大气含水量的多少有密切关系,大气含水量低的地区,空中水资源稳定,而大气含水量高的地区,空中水资源不稳定。夏季是四季中方差最大的季节,稳定性较差;冬季是大气含水量方差最低的季节,特别是山区大气含水量稳定,秋季略高于春季。天山东部和西部地区的大气含水量方差明显要小,而中部地区较大。大气含水量的稳定性与海拔高度呈反相关。降水转化率与海拔高度密切相关,随着海拔高度上升,降水转化率增大。天山山区年降水转化率最大,伊犁河谷冬季降水转化率最大。

罗茨水蒸气压缩机性能实验研究

压缩机是蒸气压缩蒸发系统的核心设备,会显著影响系统的能耗和运行稳定性。本文搭建了基于罗茨压缩机驱动的蒸气压缩蒸发实验台,蒸发温度为80~100℃,蒸发压力为46.60~101.64 kPa,压缩机压升为17.86~36.03 kPa,蒸发量为125.72~424.85 kg/h,实验研究了吸气流量、压缩比功、容积效率和等熵效率随蒸发温度的变化规律。结果表明:随着蒸发温度的升高,吸气流量(7.10~11.74 m^(3)/min)逐渐升高,压缩比功(310.69~158.54 kJ/kg)逐渐降低,容积效率(52.21%~71.54%)和等熵效率(16.48%~36.15%)均逐渐升高,提高工作频率有助于提高压缩机效率,实测容积效率和压缩比功与相关文献数据较为吻合。压缩机容积效率和等熵效率实测值与理论值存在一定误差,但该误差随蒸发温度的升高而减小,罗茨水蒸气压缩机在蒸发温度为90~100℃范围内运行较为稳定、效率较高。

环境因子对冬小麦水分利用效率的影响

对干湿两种水分处理下农田冬小麦群体水分利用效率与环境因子的关系进行分析。结果表明：（１）各环境因子以综合复杂的方式影响水分利用效率。（２）由土壤干旱和大气高蒸发势迭加而成的水分亏缺所引起的气孔阻力上升有利于提高水分利用效率，但水分亏缺同时引起的叶－气水汽压梯度增大则会降低水分利用效率。在水分亏缺最强的午后１２：００～１６：００时，水分利用效率最低。

近二十年内蒙古地区空中水资源的分布及变化趋势

根据内蒙古自治区12个探空站1980-2000年的每日两个时次的探空资料,计算了每个探空站的可降水量,分析了内蒙古地区可降水量的时空分布和多年的变化趋势。另外利用这12个站的实际降水资料分别计算了它们每个月的降水效率、年平均降水效率。结果表明:可降水量从1-7月逐渐增加,7月后逐渐减少,且从东到西依次减少。1980-2000年12个站的可降水量均呈现出增加的趋势。降水效率在7、8月份最大。年平均降水效率最少的是额济纳,最大的是索伦。内蒙古地区的降水效率较低,即使是降水效率最大的索伦站7月份的降水效率也只有21.02%,因此,可以说内蒙古地区的空中水资源的开发潜力是较大的。

火电厂烟气水分及余热陶瓷膜法回收实验

火力发电是高耗能、高耗水行业,回收火电厂烟气中水分及余热能起到显著的节能、节水效果。通过单根20 nm孔径陶瓷膜进行烟气中水分及余热回收实验,研究不同烟气流量(4～18L/min)、烟气温度(50～70℃)、烟气相对湿度(40%～100%)和冷却水流量(0.5～2.0 L/min)对回收性能的影响。结果表明:水回收速率随烟气流量、烟气温度、烟气相对湿度增加而上升;水回收效率随烟气温度、烟气相对湿度增加而上升,随烟气流量增加而下降;冷却水流量变化对水回收速率和效率没有影响;烟气对流凝结努塞尔数(Nuf)用于评价烟气在陶瓷膜内的传热性能,其随烟气流量、烟气相对湿度、冷却水流量增加而升高;大烟气流量工况时Nuf随烟气温度增加而升高,小烟气流量时Nuf随烟气温度增加呈先升高后降低趋势。研究结果对于陶瓷膜在火电厂烟气中实际应用具有理论指导意义。