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冬小麦土壤墒情预报及优化灌溉技术的计算机模型 总被引：7，自引：1，他引：7
利用土壤水分平衡方程，根据我省冬小麦的生长规律及冬小麦优化灌溉技术推广经验，建立了冬小麦土壤墒情预报及优化灌溉技术的计算机模型，利用该模型，可以较准确地预报未来1个月的土壤墒情变化，并可根据我省小麦的不同发育期给出以最高产量和最佳经济效益为目标的两种灌溉建议。 相似文献
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河南省土壤湿度年变化规律 总被引：1，自引：0，他引：1
利用河南省土壤墒情预报模型中建立的河南省台站土壤墒情数据库资料，对不同类型土壤湿度进行分析，从而确定不同类型土壤湿度差异、地下水对土壤湿度的影响及河南省土壤湿度的年变化规律。 相似文献
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利用土壤水分平衡方程，结合河南省冬小麦和夏玉米的生长规律和1994～2000年冬小麦、夏玉米田实测土壤湿度资料，建立了河南省冬小麦、夏玉米土壤水分预报及优化灌溉的计算机模型。用1998～1999年郑州市麦田实测土壤湿度资料验证该模型模拟结果，未来10、20、30天土壤湿度相对误差分别为-7．3％～7．7％、-8．3％～6．8％、-7．6％～7．7％，表明利用该模型，可以较为准确地预报未来1个月的土壤水分变化，并可根据小麦、玉米不同发育期特点，给出以最高产量和最佳经济效益为目标的灌溉建议。 相似文献
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基于自动土壤水分观测站数据建立本地土壤水分变化模型,通过人工取土烘干法观测的实际土壤湿度数值对自动土壤水分观测站数据进行修正和校订,再由修正过的自动土壤水分观测站数据作为当日的初始湿度,通过天气预报中无降水日数或降水日期及雨量大小做出未来一段时间内的失墒或增墒的模型,再通过不同的气象条件对增、失墒进行相关订正,做出相应的土壤墒情的预报,最后根据土壤墒情预报结果对照本地的土壤干旱量级指标,从而随时做出快速准确的本地旱情预报,为各级领导组织指挥农业生产、开展人影作业、指导农民进行田间管理等活动提供及时可靠的决策依据。本文通过此模型对2012年松原地区夏季干旱情况进行预报,再通过实际土壤墒情实况进行对比,预报结果基本正确。由于人工测值有一定随机性,所以人工观测值与自动站观测数据的对比只能做为参考而不可能完全吻合。但从长期数据应用情况来看,基于土壤自动水分观测站的土壤墒情监测及干旱预报模型方便稳定,反应水分变化趋势更有连续性。 相似文献
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利用吉林省西部10个自动土壤水分观测站数据与人工取土烘干法实测土壤湿度数据,制作吉林省西部土壤墒情监测及干旱预报模型.结果表明:不同气候背景下在作物不同生育期、土壤不同深度、不同初始湿度下的土壤湿度的变化趋势大致相同,但在相同的无降水日数或降水量时,不同台站不同深度的土壤湿度变化率却有一定的差异.各站农田土壤初始湿度越大,无降水时初期墒情下降速率越明显;而土壤湿度初始值越低,则失墒速率越慢.土壤不同深度均是开始时间失墒较快,后期变化逐渐趋于减弱状态.土壤深度越深则水分变化速率越缓,降水量越大,0～50 cm土壤湿度变化曲线整体越接近一致,直到从上而下几层土壤湿度全部达到饱和.通过对2017—2019年吉林省西部玉米农田土壤湿度预报结果和实测值进行对比检验,基于自动土壤水分观测数据的吉林省西部干旱模型预报的准确率超过80％. 相似文献
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春季麦播期土壤墒情预报方法 总被引：2，自引：0，他引：2
运用相关系数和逐步回归等统计分析方法 ,建立佳木斯市春季麦播期土壤墒情预报方程 ,试作春季麦播期土壤墒情预报 ,经检验方程合理可用 相似文献
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This research is supported by the Research Grants Council of the University Grants Committee of Hong Kong Grant . C. H. So Johnny C. L. Chan Department of Physics Materials Science City University of Hong Kong 《大气科学进展》1997,(2)
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东北地区水稻障碍型低温冷害变化对区域气候增暖的响应 总被引：2，自引：0，他引：2
利用东北地区153个气象站1961—2010年逐日气温资料,采用统计学方法分析了水稻障碍型低温冷害的气候变化特征及其对区域气候变暖的响应情况。结果表明,东北大部地区水稻障碍型低温冷害事件呈减少趋势,但区域性较为明显;障碍型低温冷害对关键发育期气温变化响应较为敏感,二者呈显著的负相关关系,表现为气温每升高1 ℃,东北地区冷害减少35个站次。东北地区关键发育期气温均呈上升趋势,但吉林西部地区障碍型冷害却随之增加,分析了关键发育期气温变率和气候变率,将其解释为局地障碍型冷害增加主要受气候变率增大的影响,逐日气温变率对其影响不大。 相似文献
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以FY-3可见光与红外辐射计（VIRR）为主要数据,利用FY3\VIRR 1、6、10通道数据,以指数法和光谱阈值相结合的多光谱积雪监测算法对2013年阿勒泰地区卫星数据进行积雪监测处理。处理结果与MODIS积雪监测业务产品对比分析得出：利用FY3\VIRR可以实现对研究区的积雪遥感监测,监测结果与现有MODIS积雪监测业务产品较一致,具有可比性。 相似文献
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利用NCEP再分析资料及实况资料,分析四川地区1951~2007年1月典型冷、暖年及2008年1月四川低温雨雪冰冻天气的大气环流特征,发现:东亚冬季风异常偏强(偏弱)与四川隆冬季节气温偏低多阴雨雪天气(气温偏高晴少雨雪天气)明显相关,冷年表现为500hPa极涡在亚欧地区强度显著偏南(偏强),南支低槽活跃,西伯利亚~蒙古地面冷高压偏强,四川地区850hPa气温偏低,0℃线偏南,为明显的反气旋距平风场,低层湿度增加,暖年则与之相反。 相似文献
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The limited-length-scale k-e{k-\varepsilon} model proposed by Apsley and Castro for the atmospheric boundary layer (Boundary-Layer Meteorol 83(1):75–98, 1997) is revisited with special attention given to its predictions in the constant-stress surface layer. The original model proposes a modification to the length-scale-governing e{\varepsilon} equation that ensures consistency with surface-layer scaling in the limit of small ℓ m/ℓ max (where ℓ m is the mixing length and ℓ max its maximum) and yet imposes a limit on ℓ m as ℓ m/ℓ max approaches one. However, within the equilibrium surface layer and for moderate values of z/ℓ max, the predicted profiles of velocity, mixing length, and dissipation rate using the Apsley and Castro model do not coincide with analytical solutions. In view of this, a general e{\varepsilon} transport equation is derived herein in terms of an arbitrary desired mixing-length expression that ensures exact agreement with corresponding analytical solutions for both neutral and stable stability. From this result, a new expression for Ce3{C_{\varepsilon3}} can be inferred that shows this coefficient tends to a constant only for limiting values of z/L; and, furthermore, that the values of Ce3{C_{\varepsilon3}} for z/L → 0 and z/L →∞ differ by a factor of exactly two. 相似文献
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Bruce B. Hicks William R. Pendergrass Barry D. Baker Rick D. Saylor Debra L. O’Dell Neal S. Eash Jeffrey T. McQueen 《Boundary-Layer Meteorology》2018,167(2):285-301
The assumption that the roughness Reynolds number \(( Re_{*})\) can be used as a basis for quantifying the boundary-layer property \({ kB}^{-1} (= \ln (z_{0}/z_{0T}))\) as in some modern numerical models is questioned. While \({ Re}_{*}\) is a useful property in studies of pipe flow, it appears to have only marginal applicability in the case of treeless terrain, as studied in the two experimental situations presented here. For both the daytime and night-time cases there appears to be little correlation between \({ kB}^{-1}\) and \({ Re}_{*}\). For daytime, the present studies indicate that the assumption \({ kB}^{-1} \approx 2\) is acceptable, while for night-time, the scatter involved in relating \({ kB}^{-1}\) to \({ Re}_{*}\) suggests there is little reason to assume a direct relationship. However, while the scatter affecting all of the night-time results is large, there remains a significant correlation between the heat and momentum fluxes upon which an alternative methodology for describing bulk air–surface exchange at night could be constructed. The friction coefficient (\(C_{f}\)) and the turbulent Stanton number \(({ St}_{*})\) are discussed as possible alternatives for describing bulk properties of the air layer adjacent to the surface. While describing the surface roughness in terms of the friction coefficient provides an attractive simplification relative to the conventional methodologies based on roughness length and stability considerations, use of the Stanton number shares many of uncertainties that affect \({ kB}^{-1}\). The transitions at dawn and dusk remain demanding situations to address. 相似文献
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Ivan Kovalets Rodolfo Avila Meelis Mölder Sophia Kovalets Anders Lindroth 《Boundary-Layer Meteorology》2018,168(1):103-126
A model of \(\hbox {CO}_{2}\) atmospheric transport in vegetated canopies is tested against measurements of the flow, as well as \(\hbox {CO}_{2}\) concentrations at the Norunda research station located inside a mixed pine–spruce forest. We present the results of simulations of wind-speed profiles and \(\hbox {CO}_{2}\) concentrations inside and above the forest canopy with a one-dimensional model of profiles of the turbulent diffusion coefficient above the canopy accounting for the influence of the roughness sub-layer on turbulent mixing according to Harman and Finnigan (Boundary-Layer Meteorol 129:323–351, 2008; hereafter HF08). Different modelling approaches are used to define the turbulent exchange coefficients for momentum and concentration inside the canopy: (1) the modified HF08 theory—numerical solution of the momentum and concentration equations with a non-constant distribution of leaf area per unit volume; (2) empirical parametrization of the turbulent diffusion coefficient using empirical data concerning the vertical profiles of the Lagrangian time scale and root-mean-square deviation of the vertical velocity component. For neutral, daytime conditions, the second-order turbulence model is also used. The flexibility of the empirical model enables the best fit of the simulated \(\hbox {CO}_{2}\) concentrations inside the canopy to the observations, with the results of simulations for daytime conditions inside the canopy layer only successful provided the respiration fluxes are properly considered. The application of the developed model for radiocarbon atmospheric transport released in the form of \(^{14}\hbox {CO}_{2}\) is presented and discussed. 相似文献
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Mountaintop trace-gas mixing ratios are often assumed to represent free atmospheric values, but are affected by valley planetary boundary-layer (PBL) air at certain times. We hypothesize that the afternoon valley–PBL height relative to the ridgetop is important in the diurnal cycle of mountaintop trace-gas mixing ratios. To investigate this, we use, (1) 4-years (1 January 2009–31 December 2012) of CO and \(\hbox {CO}_{2}\) mixing-ratio measurements and supporting meteorological observations from Pinnacles (\(38.61^{\circ }\hbox {N}\), \(78.35^{\circ }\hbox {W}\), 1017 m a.s.l.), which is a monitoring site in the Appalachian Mountains, (2) regional \(\hbox {O}_{3}\) mixing-ratio measurements, and (3) PBL heights determined from a nearby sounding station. Results reveal that the amplitudes of the diurnal cycles of CO and \(\hbox {CO}_{2}\) mixing ratios vary as a function of the daytime maximum valley–PBL height relative to the ridgetop. The mean diurnal cycle for the subset of days when the afternoon valley–PBL height is at least 400 m below the ridgetop shows a daytime CO mixing-ratio increase, implying the transport of PBL air from the valley to the mountaintop. During the daytime, on days when the PBL heights exceed the mountaintop, PBL dilution and entrainment cause CO mixing ratios to decrease. This decrease in CO mixing ratio, especially on days when PBL heights are at least 400 m above the ridgetop, suggests that measurements from these days can be used as with afternoon measurements from flat terrain in applications requiring regionally-representative measurements. 相似文献