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1.
识别影响流感流行强度的关键气象因子有助于提高流感疫情预警、预测能力。基于2010—2018年上海市冬、春季周流感样病例数(ILI)和气象观测资料,采用分布滞后非线性模型(DLNM)和广义相加回归模型(GAM)系统分析了ILI与多种气象因子的关联,在此基础上使用多元逐步回归模型识别调控流感流行强度的关键气象因子。结果表明,冬、春季平均气温和相对湿度与ILI呈反向关系,低温和低湿效应的滞后持续时间较长,5℃和50%环境下滞后3周的累积风险分别为2.16(95%CI:1.18—3.95)和2.51(95%CI:1.96—3.23),且气温与相对湿度对ILI存在交互影响,干燥环境会显著加强冷效应。此外,与气温有关的不稳定天气要素也与ILI具有显著关联,其中气温日较差对ILI的影响在当周最大,每升高1℃,ILI风险增加1.8%(95%CI:0.2%—3.4%), ILI流行早期的冷空气活动频次与ILI呈单调递增线性关系,冷空气活动频次每增加1次,ILI风险增大6.8%(95%CI:2.1%—11.7%)。其中,流行早期阶段的频繁冷空气活动和流行期内的干燥环境为严重流感事件的爆发提供了合适的外界环... 相似文献
2.
周智翔 《热带气象学报(英文版)》2009,15(1):1-12
On the basis of a comprehensive literature review and data analysis of global influenza surveillance, a transmission theory based numerical model is developed to understand the causative factors of influenza seasonality and the biodynamical mechanisms of seasonal flu. The model is applied to simulate the seasonality and weekly activity of influenza in different areas across all continents and climate zones around the world. Model solution and the good matches between model output and actual influenza indexes affirm that influenza activity is highly auto-correlative and relies on determinants of a broad spectrum. Internal dynamic resonance; variations of meteorological elements (solar radiation, precipitation and dewpoint); socio-behavioral influences and herd immunity to circulating strains prove to be the critical explanatory factors of the seasonality and weekly activity of influenza. In all climate regions, influenza activity is proportional to the exponential of the number of days with precipitation and to the negative exponential of quarter power of sunny hours. Influenza activity is a negative exponential function of dewpoint in temperate and arctic regions and an exponential function of the absolute deviation of dewpoint from its annual mean in the tropics. Epidemics of seasonal influenza could be deemed as the consequence of the dynamic resonance and interactions of determinants. Early interventions (such as opportune vaccination, prompt social distancing, and maintaining incidence well below a baseline) are key to the control and prevention of seasonal influenza. Moderate amount of sunlight exposure or Vitamin D supplementation during rainy and short-day photoperiod seasons, more outdoor activities, and appropriate indoor dewpoint deserve great attention in influenza prevention. To a considerable degree, the study reveals the mechanism of influenza seasonality, demonstrating a potential for influenza activity projection. The concept and algorithm can be explored for further applications. 相似文献
3.
青藏高原中部闪电活动与相关气象要素季节变化的相关分析 总被引:14,自引:5,他引:14
利用 1995年 4月至 2 0 0 2年 12月间卫星观测的闪电资料与NCEP再分析资料中的地表降水率、云功函数和热通量 ,分析了青藏高原中部闪电活动与相关气象要素季节变化之间的关系。研究发现 :青藏高原中部闪电活动的峰值出现在 7月份 ,并在春季表现出明显的闪电活动 ;相关气象要素中 ,最能够准确描述闪电活动的季节变化及其春季异常特征的仅有地表总热通量 ;降水 (或云功函数 )与鲍恩比 (感热通量和潜热通量之比 )的乘积能够较好地反映闪电活动的季节分布特征与春季的“异常”。结果表明 ,感热通量或鲍恩比可能在对流有效位能向对流上升动能的转化过程中起着重要的作用 ,鲍恩比可作为修正闪电产生效率的一个重要参量。 相似文献
4.
MIXED-PHASE STRATIFORM CLOUD SYSTEM MODEL AND CASE MODELING ON TWO LOW-LEVEL MESOSCALE VORTICES 下载免费PDF全文
We introduced the two-parameter stratiform cloud model of Hu and Yan (1986) into the mesoscale model of Anthes et al.(1987),and reprogramed the latter,then constructed a three-dimensional stratiform cloud system model which includes three phases of water and detailed cloud physical processes.For the stability and accuracy of calculation in a larger time step,we accepted a set of hybrid-schemes for all and the time split scheme for some of the cloud physical processes,and proposed a parameterized method which calculates different types of phase change processes simultaneously,and designed the falling schemes of particles following the Lagrangian method.We used a dry model,a cumulus parameterization model,a two-phase explicit scheme model,and the model presented here to simulate two low-level mesoscale vortices,compared and analysed the simulating capability of these models.The results show that in simulation of the circulation structure of meso-vortex,the structure of cloud system,and surface precipitation,the model presented here is more reasonable and closer to the observations than other models. 相似文献
5.
WANG Shourong HUANG Ronghui DING Yihui LEUNG. L. R WIGMOSTA M. S. VAIL. L. W. 《Acta Meteorologica Sinica》2002,16(3):374-387
The advanced distributed hydrology-soil-vegetation model DHSVM,developed by Wigmostaet al.(1994)is introduced from US Pacific Northwest National Laboratory.To apply DHSVM inChina for the first time some improvements have been made in terms of the basin characteristics:1)to change evapotranspiration model,using the improved Penman-Monteith approach in place ofthe original one;2)to change the model structure,inserting datasets from 4 stations to grid cellsfor each river basin,instead of datasets from one or two stations;3)to develop new hydrology,vegetation and soil parameterization schemes for improving the simulated results,with focus oncalculation and adjustment of 11 parameters,such as soil porosity (?),field capacity θ_(fc),leaf areaindex LAI,stochastic resistance γ_s,among the total 33 parameters.Then the improved DHSVM isdriven by observed datasets for Luanhe River Basin and Sanggan River Basin,respectively.Thesimulated evapotranspiration(ET),runoff,snow water equivalent,water table,soil moisture andpercolation are then gained as DHSVM outputs.The simulated ET shows that the highest peakappears in May or June instead of July or August.This is consistent with the real situations,owing to the improvement of ET model.The simulated runoff process and flood peak are quiteconsistent with the observed ones.The model efficiency values for Luanhe River and SangganRiver Basins are 0.89 and 0.82,respectively,which shows high simulating ability of the modelsystem for both relatively humid and dry basins. 相似文献
6.
分布式水文-土壤-植被模式的改进及气候水文Off-line模拟试验 总被引:12,自引:3,他引:12
文中对引进的高分辨率 (94 2 .5m× 94 2 .5m)分布式水文 土壤 植被模式 (DHSVM) ,针对海、滦河流域的特点进行了改进 ,主要包括 :(1)改变蒸散发模拟方法 ,用改进的Penman Monteith模式模拟海滦河流域的蒸发 ,较好地模拟出 1a内的两个峰值 ,最大值出现在 4~ 6月 ,次大值出现在 7~ 8月 ;(2 )改变水文模式结构 ,用多站点气候观测资料内插到模式网格点 ,充分实现了分布式水文模拟 ;(3)发展新的水文、植被、土壤参数化方案 ,对 33个参数分区计算和确定 ,并重点对土壤孔隙度 φ、土壤蓄水能力θfc、叶面指数LAI、随机阻抗γs 等 11个参数进行调试和修订 ,提高了水文模拟精度。用改进的DHSVM模式分别对滦河、桑干河流域蒸散发、地下水位、土壤湿度、土壤水下渗、产流、汇流与径流等水文过程进行Off line模拟试验 ,模拟结果与实测值一致性较好 ,滦河流域 1979~ 1991年、桑干河流域 1979~ 1987年水文模拟效率系数分别为 0 .89和 0 .82 ,均高于国内其他相关研究 相似文献
7.
通过一年的试验,初步得出参试各变量x_1(灌溉定额)、x_2(灌溉次数)、x_3(头水叶龄)和x_4(保苗株数)对产量y的多元回归模型。利用这一模型分析了各参试因子对产量的作用,并通过频数分析,筛选了地膜覆盖条件下玉米高于某一产量指标,同时限制灌溉定额或灌水次数的节水增产的优化措施组合。本文还分析了参试因子对玉米产量构成因素的影响,评价了地膜的节水效果和增温增产效果,初步探索了地膜玉米的节水增产机理。 相似文献