“7.21”山西北部罕见区域暴雨的诊断分析

为了更好地认识山西省北部区域暴雨形成机制,为防灾减灾提供精细化的预报信息,利用常规地面和高空探测资料、NCEP/NCAR 1°×1°再分析资料、加密自动气象站资料以及FY-2E卫星TBB资料,对2012年7月20日20时—21日20时山西北部区域暴雨过程进行诊断分析。结果表明：（1）这次暴雨发生在200 hPa高空西风急流稳定加强、500 hPa阻塞背景下,低空低涡切变线是其主要影响系统,低空西南急流偏西偏北是其重要原因之一。（2）雨区上空对流层低层大气处于强对流不稳定状态,高层强的干侵入和低层弱北风的侵入是触发不稳定能量释放的重要机制。（3）地面自动站风场信息显示主要触发系统有中尺度涡旋、辐合和切变3种类型,3种类型造成的降水强度和持续时间均不同。（4）500 hPa垂直螺旋度的变化可表征强降水系统的发展和移动,而考虑水汽因子后的水汽垂直螺旋度能更好地反映雨区上空对流层中低层的动力场结构特征,对预报强降水落区和移动有很好的指示意义。     

雷达资料同化在安徽暴雨个例中的应用

为了研究雷达资料同化对安徽暴雨预报的作用,使用WRFV3.4模式对2012年7月12日—14日安徽的一次暴雨个例,选取Eta微物理方案和GD积云参数化方案组合,利用WRFVAR3.4三维变分同化系统进行了直接循环同化雷达径向风资料。将同化试验和控制试验模拟的降水与实况比较,结果表明,同化了雷达径向风后在一定时间范围内能明显地提高降水预报,同化雷达资料后的前12 h内降水的同化试验较控制试验有一定的改进,特别是前6 h,可以看到,在小雨、中雨及暴雨量级上,都较控制试验有明显改进,在加入雷达径向风资料同化后,降水区的风场辐合特征更为明显,风速也有一定增强,降水强度和中心更接近实际值。在同化雷达资料后的后12 h,可以发现同化试验的优势逐渐不明显。     

Cropping system effects of maize on infiltration,runoff and erosion on loess soils in South-Limbourg (The Netherlands): A comparison of two rainfall events

Two natural rainfall events are compared to evaluate the effects of three cropping systems of silage maize on soil moisture content, infiltration, runoff and erosion. Both rainfall events took place in early summer. One was a low intensity event with 27.6 mm of rain in 9 hours, and the other a high intensity event with 33.4 mm in 42 minutes. Cropping systems were:

• 1.(I) a spring tilled system (conventional),
• 2.(II) an autumn and spring tilled system with summer barley as spring cover crop, and
• 3.(III) an autumn tilled system with winter rye as winter cover crop and direct drilling of silage maize.

During the low intensity event, soil moisture content of the top 5 cm rose to field capacity on all three cropping systems. No runoff was generated. During the high intensity event, soil moisture content rose to field capacity on the two spring tilled cropping systems but was only slightly raised in the direct drill system, in spite of 17.7 mm of infiltrated rain. Runoff coefficients of the high intensity event were 41.7% (conventional system), 14.9% (autumn and spring tilled system) and 47.0% (direct drill system). The direct drill system showed a severely slaked soil surface in early summer, caused by winter rain.The response to rainfall of soil moisture content is ascribed to:

• 1.(I) a predominance of matrix infiltration on all cropping systems during the low intensity event and on the spring tilled systems during the high intensity event, and
• 2.(II) a predominance of infiltration via continuous macropores, open to the surface (of biologic origin), by-passing the soil matrix, on the direct drill system during the high intensity event.

The presence of continuous, vertical macropores on the direct drill system explains its surprisingly high infiltration capacity, considering its strongly slaked appearance. The smooth soil surface of the direct drill cropping system may have delayed infiltration during the flooded stage of the high intensity event by not providing vent points for the escape of soil air. Soil loss from the direct drill system during the high intensity event was only 15.6% of that from the conventional system. This is ascribed to low detachment rates of soil material by drop impact and/or overland flow, due to the presence of winter rye remains and, especially, the relatively high soil surface shear strength of the direct drill cropping system in early summer.     

Chemical amelioration of surface crusting to reduce runoff and erosion on highly weathered soils

Because of the very low soil solution ionic strengths in highly weathered soils, clay particles can be readily dispersed under the impact of raindrops. The clay fraction of many soils is dispersible under the combined effects of mechanical disturbance and low electrolyte concentration. This clay dispersion results in fine particle segregation at the soil surface, with clay particles moving into and blocking soil pores resulting in the formation of a highly impervious crust which reduces infiltration. Because the clay is dispersed, the particles usually orient themselves in a laminar fashion as they settle. As a result, runoff is substantially increased, giving rise to soil erosion. The crusts formed in this manner often have very high strengths which prevent or substantially reduce crop emergence. The formation of such crusts can be prevented by the application of relatively low rates of by-product gypsum such as phosphogypsum on the soil surface which produces sufficient electrolyte in solution during raindrop impact to maintain the clay particles in a flocculated condition. The results of a number of experiments in which different soils were treated with phosphogypsum are discussed to illustrate the effects of electrolyte concentration, level of sodium and other factors on the formation of surface crusts and the consequent runoff and erosion. As a result of the application of phosphogypsum to the soil surface, a laminar orientation of clay particles at the surface is prevented, which allows a much greater proportion of the rainfall to enter the soil. Any crusts formed are thus much weaker and do not reduce seedling emergence. This type of crust formation can also be prevented by reducing raindrop impact through the use of mulches. This phenomenon occurs on many soils not normally considered to suffer from chemically-induced physical problems, which points to the importance of considering chemical as well as physical processes in the evaluation of potential runoff and erosion.     

日照市酸雨气候特征及影响因子研究

为了能够有效减少酸雨对日照市生态系统、建筑物和人体健康的危害,加强和开展对酸雨的控制提供决策依据,利用日照市2006—2012年酸雨观测资料、污染物排放量资料,统计分析了酸雨气候变化特征,研究了降水、风、大雾、海洋气溶胶、污染物等条件对降水pH值和酸雨频率的影响。研究表明：（1）近年来日照市酸雨出现次数整体呈上升趋势,强度和频率有明显的年、季变化,夏、冬季酸雨污染较重。（2）降水量、风向、风速、大雾对酸雨的频率影响较大。（3）酸雨pH值与SO2、NO2 的排放量呈现出明显负相关关系,特别是沿海地区海洋气溶胶对pH值影响显著。     

Seasonal and crop effects on soil loss and rainfall retention probabilities: An example from the U.S. Southern Piedmont

Soil loss from and rainfall retention on cropland during individual seasons vary from year to year. To quantify this variability for evaluation of soil and water related risks for different seasons and crops, probability distributions of soil loss and rain water retention are needed. In this study, probability distributions of soil loss and rainfall retention rates were computed using rainfall, runoff, and soil loss data from three field watersheds with Cecil-Pacolet soil (Typic Hapludults) in the Southern Piedmont of the United States. Long-term (34-year) rainfall records from a nearby gage were included in the computations. Resulting probability distributions were compared to evaluate risks of soil loss and low rainfall retention for different seasons and crops. Risks due to watershed differences in slope and in terrace and waterway conservation practices were also compared. These comparisons showed that soil loss risks are greater for the summer than for the winter crop season and greater for soybean (Glycine max. L. Merr.) than for corn (Zea mays L.). Considerable soil loss risk reduction was also observed for watersheds with less land slope and with terrace and grassed waterway installation. Risk of low rainfall retention was found to be less for the winter crop season than for the summer season. Rainfall retention risks for the winter crop season appeared to be unaffected by crop and watershed differences. For the summer crop season, however, risk of low rainfall retention was observed to be slightly higher for soybean than for corn and slightly lower for fields with terraces, grassed waterways, and lesser slopes. Soil loss and rainfall retention risks computed in this study can be coupled with economic costs for crop production and conservation planning.     

砾石覆盖层截留降雨的模拟实验研究

砾石覆盖技术可减少土壤水分蒸发,在世界的一些干旱半干旱地区得到了不同程度的应用。但在降雨时,雨水通过覆盖层进入土壤的过程中,覆盖层也会截留一定的降雨量。此文通过模拟降雨实验,表明：在降雨强度、降雨历时和铺设方式等相同的条件下,烘干砾石的吸水量随着降雨历时的延长而增大,并逐渐达到饱和吸水量;烘干砾石达到吸水饱和所需的降雨历时随着砾石平均等效粒径的减小而缩短;随着砾石平均等效粒径的增加,覆盖层砾石颗粒间的滞留水量逐渐减少;饱和砾石覆盖层的截留水量也逐渐减小,用指数衰减拟合模型进行拟合,具有高度的显著性。     

一次锋前暖区暴雨成因分析

利用常规气象观测、自动站、区域雨量站、卫星、雷达、再分析等资料,对2015年8月发生的一次锋前暖区暴雨进行了综合分析,结果表明：此次暴雨发生在西风槽东移和副高东退南压的环流背景下,以热力条件为主导引发的锋前暖区强对流性降水是此次暴雨产生的主要贡献者;暴雨发生在高空急流右后侧的显著辐散区,700hPa暖式切变线、850hPa冷式切变线、地面干线以及SI<-2℃相重叠的区域;850hPa切变线上的中尺度气旋性涡旋、自动站极大风速风场切变线以及中尺度涡旋是本次暴雨的直接触发系统;由于数值模式850hPa切变线位置预报的偏差,使得中低层流型配置由前倾误导为后倾结构,直接影响了模式热力条件预报的准确性,其结果是增强了西部动力条件而弱化了东部热力条件,最终导致暴雨落区预报偏差;锋前暖区暴雨预报的关键是触发不稳定能量释放的条件,对于此类暴雨应多关注边界层风场的变化,加强新型监测资料的综合分析和应用。     

Yield-rainfall relationships in cereal cropping systems in the Ebro river valley of Spain

Wheat and barley yields from three farms in the Ebro river valley are shown to be strongly dependent on seasonal rainfall, particularly that during November-January and March-May of the cropping season. In the driest farm, in Monegrillo, Zaragoza province (seasonal rainfall, 251 mm), yields increased by c. 5.9 (wheat) and 9.4 (barley) kg ha⁻¹ per mm of extra rain during the entire cropping season, taken as October-May inclusive. The other farms, at El Canós and Selvanera in Lleida province, had seasonal rainfalls of 364 and 334 mm, and yields of barley increased by 4.3 and 9.0 kg ha⁻¹, respectively, per mm of extra rain in the cropping season, taken as September to May inclusive.

In Monegrillo, cereals are grown in a cereal-fallow rotation. Normal fallowing (duration 17 months) compared to minimum fallowing (5 months) increased the calculated water content of the top 100 cm of the dominant soils by 19 mm. This extra water was estimated to benefit yield by 7.0% (wheat) and 6.2% (barley), raising the average yields of crops greater than 300 kg ha⁻¹ to 1222 and 1522 kg ha⁻¹, respectively. Agronomic practices in Monegrillo during the fallow should focus on means of increasing the proportion of the rain stored in the profile during the fallow. At all three locations, decreasing water evaporation from the soil during the cropping season would likely benefit yield.     

离散元法在农业工程领域的应用进展

简述了离散元法在农业工程领域方面的研究成果,根据离散元法在农业工程领域的不同应用,分别讨论了离散元法在土壤散体颗粒、农业物料颗粒、多相流中单相介质的应用研究现状,指出了存在数量级受限,颗粒模型不精准,复杂工况制约等问题。提出今后离散元法的研究趋势:开发农业工程领域的专用离散元软件,提高颗粒群的运算效率;通过准确获取物料的细观参数,从理论基础上完善接触模型,使仿真颗粒与真实颗粒更为接近;通过离散元法软件与其他软件耦合,结合API的二次开发,拓宽离散元法在复杂散体颗粒运动仿真的应用。     

基于季节性降雨的双季稻生育后期干湿交替灌溉对稻谷产量及品质的影响

为明确依靠季节性降雨实现干湿交替灌溉对双季稻生育后期的影响,研究了双季稻齐穗后0、7、14和21d（对照）停止灌溉对叶绿素含量、干物质转化、产量及品质的影响。结果显示,早稻灌浆期降雨多且雨量大,齐穗后早停止灌溉延长干湿交替灌溉时间,可显著提高叶片、茎鞘干物质转化、穗粒数和结实率,叶绿素含量降低,无效分蘖成穗减少;与对照相比,齐穗后0d停止灌溉,实收产量提高16.0%,整精米率提高8.2%。晚稻灌浆期间降雨相对偏少,适期延迟停止灌溉,可提高叶片、茎鞘干物质转化、穗粒数、结实率、千粒重及整精米率;与对照相比,齐穗后7d停止灌溉,实收产量提高11.0%,整精米率提高6.1%;垩白度、垩白粒率及透明度随停止灌溉时间提前和干湿交替灌溉时间延长而增加,胶稠度以早稻齐穗后7d和14d、晚稻齐穗后14d停止灌溉最高,所有处理对双季稻米整体品质指标等级无影响。     

辽西雨养玉米农田土壤水分变化特征及其模拟

土壤含水量是作物生长发育的关键影响因子之一,确定土壤含水量变化及预测土壤含水量变化趋势,对于雨养农业更加有效地保墒、提高作物水分利用效率和增强抗旱防灾能力有着重要的现实意义。利用2008-2011年锦州玉米生长季逢三逢八土壤湿度观测数据,日气温降水数据和2008年玉米生长发育期数据资料,结合CERES-MAIZE土壤水分模块,分析了雨养玉米农田土壤水分时空变化特征和模拟了土壤水分时空变化特征。结果表明：生长季降水并不能反映土壤水分条件的好坏,生长季中雨以下的降水量和降水频次与土壤水分条件的好坏较好的一致性;土壤水分随土层深度而增加,0-40cm土壤含水量平均值和最低值分别是田间持水量的69%-82%和49%-64%;玉米根系生物量与生长时间呈二次曲线关系,所建根系生物量模型解释率达89.7%;耦合根系生物量模型和叶面积指数模型的CERES-MAIZE中的土壤水分模块能够较好的模拟雨养玉米生态系统土壤水分的时空变化特征。     

“7.21”特大暴雨的地形影响分析

为了深入研究地形对暴雨的影响,提高暴雨预报的精准度,本研究利用NCEP资料和WRF模式对“7.21”特大暴雨进行了数值模拟和分析。结果显示：“7.21”特大暴雨是在有利的环境场以及这一地区特殊地形作用下发生;强降水中心主要出现在山谷、山区与平原交界区域,与地形的影响密切相关。地形的影响主要表现热力和动力2个方面：风顺山谷而吹,形成明显的高温、高湿的水汽输送,同时形成辐合、上升运动;山区和平原交界地带温度梯度大,加上迎风坡作用,有利于对流的发生、发展。     

不同农田管理措施旱地玉米土壤水分特征分析

试验研究了不同农田管理措施下旱地玉米的土壤水分特征。结果表明,秸秆整秆全覆盖、微孔地膜覆盖较秸秆粉碎还田和常规种植能提高土壤水分,增加降水的入渗深度,减少土壤耗水量,其顺序为秸秆整秆全覆盖>微孔地膜覆盖>秸秆粉碎还田>常规种植。受基础土壤水分不同和降雨较少的影响,玉米生育前期不同农田管理措施土壤水分差异不大,8月份充足的降水后,各措施充分显示了其蓄水保墒的作用,其中,9月份秸秆整秆全覆盖0~120 cm土壤贮水量为248.2 mm,较常规种植增加32.1 mm;降水入渗深度为120 cm,较常规种植增加25 cm。     

Changes in microrelief and their effects on infiltration and erosion during simulated rainfall

The erosivity of soils under a given rainfall energy appears to vary greatly among soil orders, probably reflecting differences in clay composition and organic matter content. This study was conducted to quantify microrelief, infiltration, and sediment yield changes during three consecutive simulated rain events on a Udic Haploboroll and a Typic Hapludalf from Minnesota, and a Mollic Kandiudalf, and Typic Palehumult from Uganda. Air dry aggregates (< 5 mm) were packed in 19 1 containers tilted to a 5% slope and were subjected to three consecutive high energy rain storms (63 mm h⁻¹) for a duration of 1 h. Runoff and sediment were continuously monitored during a storm. Infiltration was measured by continued weighing of the soil and containers. An automated non-contact laser relief meter was used to measure changes in soil roughness initially and after each storm. Soil surface roughness decreased during the rain events indicating that aggregate breakdown was the dominant process in seal formation. For example, random roughness decreased form 5.9 to 4.0 mm on Barnes loam and from 9.7 to 6.9 mm on Renova silt loam with cumulative rainfall of 0 and 126 mm. These infiltration rates indicated that the Barnes Loam (Haploboroll) and Kabanyolo clay (Kandiudalf) were unstable soils while Kachwekano clay (Palehumult) and Renova silt loam (Hapludalf) were quite stable. Final infiltration rates after 3 consecutive rainfalls on Kachwekano clay (15 mm h⁻¹) and Renova silt loam (13 mm h⁻¹) [the stable aggregate soils] were significantly higher than those of Barnes loam (4 mm h⁻¹) and Kabanyolo clay (3 mm h⁻¹). For the two stable soils a high infiltration rate on a rough surface was maintained until aggregate breakdown occurred and runoff began. Sediment yield from Barnes loam (29 kg m⁻²) and Kabanyolo clay (28 kg m⁻²) was significantly greater than soil loss from Kachwekano clay (0 kg m⁻²) and Renova silt loam (6 kg m⁻²). The microrelief method to quantify aggregate stability is an improvement over wet sieving and other related measurements because of its rapidity and because the statistical quantification can be linked to physical processes.     

Landscape Position and Precipitation Effects on Spatial Variability of Wheat Yield and Grain Protein in Southern Italy

Wheat yield and protein content are spatially variable because of inherent spatial variability of factors affecting the yield at field scale. In Mediterranean environments, yield variability is often caused by the irregular weather pattern, particularly rainfall and by position on the landscape. The objective of this study was to determine the effects of landscape position and rainfall on spatial variability of wheat yield and protein in a rolling terrain field of Southern Italy, and to propose stable management areas through simulation modelling and georesistivity imaging in rolling landscape. The study was carried out in Southern Italy, during 2 years of wheat monoculture; extensive soil properties and in-season plant measurements were measured. This study showed that soil water content was the main factor affecting spatial variation of yield for both years. The interactions between rainfall, topography and soil attributes increase the chances to observe yield variability among years. The principal component analysis demonstrated that for both years, soil water content explained most of the variability. The crop simulation model provided excellent results when compared with measured data with root mean square error of 0.2 t ha⁻¹. The simulated cumulative probability function showed that the model was able to confirm the yield temporal stability of three different zones.     

Influence of a polyacrylamide soil conditioner on runoff generation and soil erosion: Field tests in Baringo District,Kenya

Following promising laboratory results the effect of low concentration applications of a polyacrylamide soil conditioner SEPARAN AP30 on soil properties was tested under field conditions in a severely degraded semi-arid region in northern Kenya. Tests of conditioner performance on tilled and undisturbed soils were carried out under simulated rainfall on crusting Eutric or Calcaric Fluvisols at two sites on alluviolacustrine flats adjacent to Lake Baringo. Tests were carried out in two series separated by up to six weeks of sunshine and natural rainfall, to determine the longevity and residual effects of conditioner application.Runoff generation and soil loss were significantly reduced on all runoff plots during the first rainfall simulation, but the most dramatic results occurred when conditioner application was combined with raking. This inhibited crust development and virtually eliminated runoff and soil loss. Under natural weathering, surface crust had developed on all plots before the second rainfall simulations. Some residual effects of the conditioner on infiltration rates were still noted, but the residual effect on soil loss was greatly diminished.The tests indicate that low concentration applications of SEPARAN are not useful on undisturbed soils, but can provide useful temporary reductions in sheet and rillwash hazard when combined with tillage and could be effectively combined with grass re-seeding for more permanent reclamation.     

辽宁春播期首场透雨时空分布特征及天气形势分析

利用1960-2014年4-5月辽宁省49个气象站逐日降水资料和NCEP再分析资料,对辽宁春播期首场透雨的时空分布特征及天气形势进行分析。结果表明：（1）单站透雨平均出现日期、无透雨次数和平均透雨量的空间分布都存在明显的地区差异,如透雨平均出现日期自东向西逐渐偏晚,辽东南部最早,辽西最晚;（2）区域性透雨近55a平均出现日期为4月19日。从周期变化来看,区域性透雨初日存在14、9、5 和3 a左右的变化周期。区域性透雨量空间分布最多的是在总体一致的背景下呈现自东南向西北递减的分布规律,其次是中东部与西部相反的空间分布,即中东部有（没）透雨,而西部没（有）透雨;（3）辽宁区域性透雨高空环流可分为深槽型、东亚倒Ω型和短波槽型三类天气学模型。     

渤海西岸一次副热带高压边缘暴雨特征分析

为探究夏季西太平洋副热带高压边缘暴雨特征,改进暴雨天气预报模型和可预报因子,提高暴雨预报准确率。利用micaps、高低空风场、T639L60 物理量资料,对2010 年8 月4—5 日发生在渤海西岸的暴雨天气过程的环流形势、高低空急流、垂直速度、相对湿度特征进行分析。结果表明：副热带高压、西风槽和中低层切变线以及地面气旋是造成此次暴雨天气过程的影响系统,高空冷空气和低空暖湿空气在渤海西岸地区交汇触发了此次天气过程;高层辐散、低层辐合为空气上升运动提供了有力的动力条件,中低层的西南风急流和近地面层持续的偏东风为降水区提供了充沛的水汽;此次暴雨出现在副高588 dagpm 等值线与584 dagpm 等值线之间中低层存在切变线的位置和200 hPa 高空急流入口处的右侧、850 hPa 低空急流的左侧所对应区域;高低空急流增强、上干下湿的对流不稳定层结发展、空气上升运动增强、高层有干冷空气侵入、低层有较强暖湿空气输送预示将出现强降水天气;高低空急流减弱消失、低层暖湿空气输送减弱消失及干冷空气侵入低层预示强降水将减弱停止。     

武威市雨日的变化趋势及特征分析

为了更好地开发利用气候资源,合理指导各行业生产,科学利用水资源和保护生态环境,利用1961—2013年武威市5个观测站的逐日降水资料,运用线性趋势系数法系统分析武威市雨日的时空分布特征。结果表明：武威市年总雨日及各量级雨日的空间分布从西南向东北呈递减趋势。武威市月雨日的变化比较一致,高峰值在7月,低谷值在11—12月;除古浪外,全市及各地各季节雨日总体上呈减少趋势。年及年代雨日也呈减少趋势,年雨日时间序列存在4~5年的准周期变化。小雨是武威市降水的主体,小雨日出现的几率占总雨日的92.7%~96.9%,随着降雨量级的增大,雨日迅速减少。雨量为 0.0 mm的小雨日均呈减少趋势,雨量大于0.0 mm的小雨日和雨量大于10.0 mm的中雨及以上的降雨日全市及各地变化趋势不太一致。