1953—2011年信江流域径流量变化特征及归因分析

利用信江流域梅港水文控制站1953—2011年径流量观测资料和11个气象站同期气象观测资料,采用统计方法、Mann-Kendall非参数检验方法、Morlet小波分析法,对信江流域径流量年内、年际变化的不均匀性、长期趋势、周期变化,及其与气候因素的相关性等进行分析。结果显示,信江流域多年平均径流量呈缓慢增大趋势,但具有显著的年际和年代际变化特征,振荡周期明显,年际变化的主要周期为6—8 a,年代际变化的主要周期为准22 a,在20世纪70—90年代最明显。年流量以主汛期(4—6月)为最多,春、夏季(3—8月)径流变差系数小,水量稳定,冬季变差系数大,水量不稳定。流域径流量与气候因素中的降水、蒸发具有显著的相关性,而人类活动中的城镇化、经济、人口等因素对径流变化起到了一定的辅助作用。     

菏泽市紫外线辐射变化特征及月预报方程

利用2008年4月至2012年12月菏泽市紫外线观测资料以及地面常规气象观测资料和空气质量资料,分析了该地区太阳紫外线辐射的变化特征及其与各因子的相关关系,并建立逐月预报方程。结果表明:菏泽紫外线辐射年总量达到187.98 W/m2,春夏两季明显高于秋冬两季,5月达到全年的最大值,1月为全年的最小值;3~9月紫外线辐射极大值均可达到5级,其他月份均可达到4级。不同天气条件下紫外线辐射强度存在明显差异,其中晴天紫外线辐射强且稳定,呈抛物线变化;多云天紫外线辐射波动较大,时强时弱;阴天紫外线辐射相对较弱。紫外线辐射强度与风速、能见度、气温呈正相关,与总云量、低云量、相对湿度呈负相关,与SO2、PM10、NO2、PM2.5多呈负相关。基于多元线性回归分析向后剔除变量方法得出的逐月预报方程,经检验总体预报效果较好,对当地紫外线等级预报工作具有参考意义。     

高寒地区日光温室地温变化及预报

利用2012年4月至2013年3月青海大通县日光温室内外地温、气温资料和大通县气象站人工观测资料,分析了高寒冷凉地区不同天气类型下日光温室地温变化规律。结果表明;研究区日光温室内日地温呈正弦曲线变化,晴天变化幅度最明显,阴天最小,地温变幅为地表〉5 cm〉10 cm〉15cm〉20 cm;室内地表、10 cm和20 cm平均地温月变化呈波形变化,最大值出现在7月,最小值在12月;随着深度增加,平均地温年较差逐渐减小;晴天、多云天、阴天不同深度地温平均日较差分别为9.6、8.3、6.1℃;地温日垂直变化仅在14时随着深度增加逐渐下降;除晴天室内最高温度外,其余温度要素与地温之间存在极显著正相关关系;建立的日光温室内10 cm最低温度预报方程和地表最低温度预报模型,可以在业务服务中应用。     

渤海表层悬沙的时空分布特征及其动力成因

针对目前渤海整个海域悬浮泥沙分布全貌的研究不充分。根据2000—2004年渤海表层悬浮泥沙分布特征选取7个典型海区,通过利用长时间序列悬沙质量浓度和风场遥感反演资料,在分析悬沙质量浓度与局地风速、物质来源等关系的基础上,定量研究风浪和潮流共同作用下、随季节显著变化的沉积物再悬浮过程,从而揭示整个渤海海域代表性海区悬沙质量浓度时空分布的动力成因。渤海不同海区表层悬沙质量浓度绝对值差别很大,多年平均最高质量浓度在20~450mg/L变化,高质量浓度集中在近岸河口区及其邻近海域,如黄河口和辽河口地区,低质量浓度区位于渤海中部、渤海海峡以及秦皇岛外海(属于近岸海域却质量浓度常年偏低的特殊海区)。渤海表层悬沙质量浓度具有明显的季节变化特征,风场的季节变化是主要影响因子,各代表性海区悬沙质量浓度与风速之间具有显著正相关关系。悬沙质量浓度与风速之间存在一定时间段的滞后相关。沉积物再悬浮的定量研究表明,除渤海海峡外,渤海其它典型海区表层悬沙质量浓度及其季节变化,均与各自海区风浪和潮流共同作用产生的最大底流速及其季节变化相对应。在渤海,底层沉积物再悬浮的季节变化是影响悬沙质量浓度季节变化最关键的动力过程。     

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Seasonal Variations in Phytoplankton Community Structure in the Sanggou,Ailian, and Lidao Bays

The seasonal variations in phytoplankton community structure were investigated for the Sanggou Bay （SGB） and the adjacent Ailian Bay （ALB） and Lidao Bay （LDB） in Shandong Peninsula,eastern China.The species composition and cell abundance of phytoplankton in the bay waters in spring （April 2011）,summer （August 2011）,autumn （October 2011）,and winter （January 2012） were examined using the Uterm6hl method.A total of 80 taxa of phytoplankton that belong to 39 genera of 3 phyla were identified.These included 64 species of 30 genera in the Phylum Bacillariophyta,13 species of 8 genera in the Phylum Dinophyta,and 3 species of 1 genus in the Phylum Chrysophyta.During the four seasons,the number of phytoplankton species （43） was the highest in spring,followed by summer and autumn （40）,and the lowest number ofphytoplankton species （35） was found in winter.Diatoms,especially Paralia sulcata （Ehrenberg） Cleve and Coscinodiscus oculus-iridis Ehrenberg,were predominant in the phytoplankton community throughout the study period,whereas the dominance of dinoflagellate appeared in summer only.The maximum cell abundance of phytoplankton was detected in summer （average 8.08 × 103 cells L-1） whereas their minimum abundance was found in autumn （average 2.60 x 103 cellsL-1）.The phytoplankton abundance was generally higher in the outer bay than in the inner bay in spring and autumn.In summer,the phytoplankton cells were mainly concentrated in the south of inner SGB,with peak abundance observed along the western coast.In winter,the distribution of phytoplankton cells showed 3 patches,with peak abundance along the western coast as well.On seasonal average,the Shannon-Wiener diversity indices of phytoplankton community ranged from 1.17 to 1.78 （autumn 〉 summer 〉 spring 〉 winter）,and the Pielou＇s evenness indices of phytoplankton ranged from 0.45 to 0.65 （autumn 〉 spring 〉 summer〉 winter）.According to the results of canonical correspondence analysis,phosphate level w     

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Modeling seasonal variations of subsurface chlorophyll maximum in South China Sea

In the South China Sea(SCS), the subsurface chlorophyll maximum(SCM) is frequently observed while the mechanisms of SCM occurrence have not been well understood. In this study, a 1-D physical-biochemical coupled model was used to study the seasonal variations of vertical profiles of chlorophyll-a(Chl-a) in the SCS. Three parameters(i.e., SCM layer(SCML) depth, thickness, and intensity) were defined to characterize the vertical distribution of Chl-a in SCML and were obtained by fitting the vertical profile of Chl-a in the subsurface layer using a Gaussian function. The seasonal variations of SCMs are reproduced reasonably well compared to the observations. The annual averages of SCML depth, thickness, and intensity are 75 ± 10 m, 31 ± 6.7 m, and 0.37 ± 0.11 mg m-3, respectively. A thick, close to surface SCML together with a higher intensity occurs during the northeastern monsoon. Both the SCML thickness and intensity are sensitive to the changes of surface wind speed in winter and summer, but the surface wind speed exerts a minor influence on the SCML depth; for example, double strengthening of the southwestern monsoon in summer can lead to the thickening of SCML by 46%, the intensity decreasing by 30%, and the shoaling by 6%. This is because part of nutrients are pumped from the upper nutricline to the surface mixed layer by strong vertical mixing. Increasing initial nutrient concentrations by two times will increase the intensity of SCML by over 80% in winter and spring. The sensitivity analysis indicates that light attenuation is critical to the three parameters of SCM. Decreasing background light attenuation by 20% extends the euphotic zone, makes SCML deeper(~20%) and thicker(12% – 41%), and increases the intensity by over 16%. Overall, the depth of SCML is mainly controlled by light attenuation, and the SCML thickness and intensity are closely associated with wind and initial nitrate concentration in the SCS.     

江苏南部汛期降水日变化特征分析

利用江苏南部20个气象观测站2008—2012年汛期(5—10月)逐小时降水资料,应用降水频率来分析了江苏南部地区降水日变化基本特征和区域差异。研究表明:降水日变化特征地域性差异较强,西部站、东部站和东北沿海站都存在一定的特征差异。东部站降水量的最大值主要出现在下午和傍晚;西部站降水量主峰值出现在下午,并且在清晨和夜间还有两个次峰值;东北沿海站呈现出午前、午后的双峰值形式。2008—2011年降水量下午高值区有先减弱后增强并提前的趋势,而上午的高值区有总体减弱并推迟的特征。2011年后有明显减弱的趋势。江苏南部总体来说,短时强降水(大于20和25 mm/h)在16—19时出现主峰值,07—09时也有相对较小的次峰值。     

绵阳市度日数特征及其变化趋势分析

从20世纪50年代以来,度日数一直作为气候变化与供暖关系的一个综合评价指标。基于全球变暖可能对我国供暖天数和温度产生深刻的影响,本文采用绵阳市1946~2005年共49年的日最低、最高气温资料,分析了绵阳市度日数年变化特征,并对其进行了趋势分析。结果表明:绵阳市历年供暖度日数最小值处于1998年,比1976年最大值低93.5%,10a年均供暖度日数变化趋势为二次曲线;制冷度日数波动性很大,1960~1979年在1500℃·d左右波动,1979~1990年在1400℃·d左右波动,1990年以后基本处于1500℃·d以上,10a年均制冷度日数拟合趋势曲线为三次曲线。基于Mann-Kendall(M-K)检验法,在α=0.05水平下,对绵阳市供暖和制冷度日数进行检验,研究发现:供暖度日数明显减少,1992年为突变起始年份;制冷度日数波动增长,且自1997年起突变。