基于MODIS-NDVI的河南省冬小麦产量遥感估测

粮食产量估测对于国家粮食生产宏观调控具有重要意义。以河南省为例, 利用区域 NDVI数据进行冬小麦产量监测研究。基于2000～2010年冬小麦生长关键期3～5月的MODIS～ NDVI数据集, 结合河南省18地市冬小麦生产数据, 分析了研究区小麦产量和播种面 积的时间动态变化特征, 建立了基于区域NDVI的冬小麦产量估算模型。结果表明:自2000 至2010年, 研究区冬小麦产量呈上升趋势, 播种面积基本保持稳定;利用单月NDVI建立的 冬小麦产量线性模型, 平均相对误差分别为12.02%、10.70%和9.27%;利用不同月份组合 的NDVI累积和建立的冬小麦产量模型, 平均相对误差分别为11.13%、10.38%、8.37%和 9.41%;利用多个月份组合的NDVI建立的多元线性回归模型, 平均相对误差分别为 11.00%、9.32%、9.04%和9.58%;将小麦播种面积作为限制因素引入多元线性模型后, 估 算精度得到了很大提升, 平均相对误差分别为5.65%、5.34%、6.76%和5.47%.通过误差 对比后发现, 在模型中引入播种面积后, 利用区域NDVI可以有效、快速、准确地对冬小麦 进行估产。     

Optically stimulated luminescence dating as a tool for calculating sedimentation rates in Chinese loess: comparisons with grain-size records

Understanding loess sedimentation rates is crucial for constraining past atmospheric dust dynamics, regional climatic change and local depositional environments. However, the derivation of loess sedimentation rates is complicated by the lack of available methods for independent calculation; this limits interpretation of the environmental changes revealed by the loess record. In particular, while the Quaternary/Neogene Chinese loess and Red Clay sequences have the potential to provide detailed records of past sedimentation and climate change, there is great uncertainty concerning: (i) the influences on sediment grain‐size and accumulation; and (ii) their relationship through time and across the depositional region. This uncertainty has led to the widespread use of assumptions concerning the relationship between sedimentation rate and grain‐size in order to derive age models and climate reconstructions. To address this uncertainty, detailed independent age models, based on optically stimulated luminescence dating, undertaken at 10 to 40 cm intervals at five sections across the Loess Plateau in China, have been used to calculate sedimentation rates and make comparisons with grain‐size changes over the late Pleistocene and Holocene. The results demonstrate that sedimentation rates are site specific, extremely variable over millennial timescales and that this variation is often not reflected in grain‐size changes. In the central part of the Loess Plateau, the relationship between grain‐size and sedimentation rate appears most complex, suggesting an interplay between local conditions at source and sink and a changing emplacement mechanism. This observation further undermines the common use of loess sedimentation age models that rely on a derived relationship between grain‐size and sedimentation rate from a type section. The results also highlight the difficulty in assigning specific environmental causes to sedimentation rate changes and, to a lesser extent, grain‐size shifts.     

土壤水分胁迫对冬小麦旗叶光合特性的影响

以土壤水分适宜做对照(CK),轻度水分胁迫(50%～70%)、中度水分胁迫(小于50%)3种处理在河北固城可控式土壤水分试验场,选择冬小麦灌浆初期的晴朗天气,采用Li-Cor 6400便携式光合作用仪,观测了3种处理的冬小麦旗叶光合作用参数的日变化。试验结果表明:土壤水分适宜时冬小麦旗叶净光合速率的日变化为"单峰型",未出现明显的"午休"现象,水分胁迫的处理都呈"双峰型",中度胁迫反而比轻度胁迫光合"午休"要短2h;3种处理的蒸腾速率日变化都呈"双峰型",气孔导度是反映叶片气体交换的重要指标,蒸腾速率与气孔导度成极显著正相关;土壤水分适宜或土壤干旱时冬小麦旗叶对环境变化的应变性较迟钝;轻度水分胁迫时冬小麦旗叶净光合速率比CK高2.8%～9.0%,蒸腾速率与CK基本相近,水分利用效率(WUE)比CK高10.6%～12.9%,这可能是一定程度的水分胁迫下冬小麦节水增产的生理调节机理。     

VARIATION OF PRECIPITATION DURING WINTER AS A CAUSE OF SUSTAINED DROUGHT IN GUANGDONG DURING THE PAST 50 YEARS

The variation characteristics of precipitation during the winter (between October and the following March, to be referred to as just “the winter” hereafter) in Guangdong province during the past 50 years (from 1957 to 2006) and the relationship with Pacific SST are studied using the methods of Empirical Orthogonal Function (EOF) analysis, wavelet analysis, and correlation analysis. The results show that The Guangdong precipitation during the winter exhibits quasi-periodic significant oscillations of 40 years and 2 years; rainfall is less from the end of the 1950s to the start of the 1970s and from the end of the 1990s to the present than from the mid 1970s to the mid 1990s. The frequency of sustained drought is more than sustained flooding during the winter. The Guangdong precipitation during this time period is in significantly positive correlation to the equatorial central and eastern Pacific SST, but in a significantly negative correlation with the western and northern Pacific SST east of the Philippine Sea. 61.5% of the sustained drought occurred in the phase of negative anomalies of the Ni?o3.4 index and 38.5% in the phase of positive ones. A composite analysis of atmospheric circulation is performed for the positive and negative phases of the Ni?o3.4 region associated with the sustained drought. The results showed that a weak polar vortex, a strong trough in Europe and a ridge near Balkhash Lake, active cold air and consistent northerly wind anomalies controlling Guangdong at low levels, an inactive westerly low disturbance in the low-mid latitude of the Asian continent, and a weak southern branch westerly trough, are all mutual causes for the sustained drought.     

北半球大气环流及其冬季风的年代际变化对青藏高原冬季降雪的影响

对1961~2010年间北半球大气环流背景异常变化及其东亚冬季风指数(东亚大槽位置指数-CW、西伯利亚高压指数-SH)与青藏高原降雪之间在年代际尺度上的相关关系进行了分析,结果表明:北半球冬季行星波年代际尺度上的异常导致了青藏高原地区冬季降雪在年代际尺度上的变化,北半球行星波"冬三(波)"流型的年代际尺度变化是青藏高原地区冬季降雪年代际尺度上增加/减少的环流背景;青藏高原冬季降雪与东亚冬季风之间也存在着年代际尺度上的显著相关。相对于1961~1986年间的冬季风减弱,青藏高原地区冬季降雪量呈现出增加趋势。结果也指出,青藏高原地区的冬季降雪、CW和SH在1986年前后存在一次显著的突变;突变后北半球冬季三波流型明显增强,青藏高原地区的降雪也相应发生了由多到少的变化。     

菏泽市冬季采暖期气候特征分析

利用菏泽地区1954—2005年气温观测资料,分析了菏泽地区近50a的气温变化趋势,探讨了该地区冬季采暖初日、终日及采暖天数的统计规律。结果表明:20世纪80年代中期以来,菏泽地区冬季气温变暖已成为事实,1986年是冬季气候变暖的突变年;采暖初日、终日及采暖天数年际变化较大;1986年以来多暖冬,与1986年以前相比,采暖初日后移,采暖终日前移,采暖天数减少。对确定冬季采暖初日、终日,实施科学供暖有一定的参考价值。     

洪泽湖地区冬季温度与ENSO事件关系

对洪泽湖地区冬季平均温度分析得出:洪泽湖地区冬季平均温度46a里上升了2℃,1986-2006年冬季平均温度一直维持在2℃以上;2006年冬季平均温度显著偏高;2007年2月平均温度创有记录以来历史最高,属于异常偏高年;中等以上ENSO事件对洪泽湖地区冬季平均温度的影响结果是正常年居多.     

吉林省冬季逆温天气特征分析

吉林省的三个探空站即长春、临江和延吉分别位于该省的中部平原、南部山区和东部盆地之中.利用三站探空资料,分析了吉林省冬季发生逆温的时空分布特征、逆温的统计特征、逆温属性以及逆温的天气气候特征.结果表明:逆温的发生频率平原最多、山区次之,盆地较少,强逆温的发生频率恰好与之相反;逆温底高平原多发生在近地面附近,山区多在400m以下,盆地多在200m以下;发生在近地面的强逆温层厚度一般多发生在1000m以下;逆温属性,平原和山区以辐射或下沉逆温为主,盆地则以辐射或下沉和平流逆温为主,同时指出了不同属性逆温的地面形势场特征.     

冬季南海北行航线分析

利用多个卫星高度计融合资料,分析了南海冬季（1月）3年（2006～2008年）平均的风场特征和海况条件。结果显示：南海东北部和台湾海峡、巴士海峡的风力和浪高都最大,其次是南海西南部海域的风力和浪高较大,其余海域的风力和浪高较小。根据这些特点,从船舶航行的安全性和经济性上考虑,设计了南海冬季北行的4条航线：从马六甲海峡直接行驶到台湾海峡的最短航线、躲避南海西南部大风大浪区和台湾以南的大浪区的航线、躲避台湾海峡的大风而绕行台湾以东的航线以及比较安全但是航线很长的航线。船长可以根据南海冬季大风大浪的情况选择避风航行的最佳航线。H轮在2005年1月行驶到南海时躲避大风大浪的实例说明大风大浪对船舶安全性的影响非常显著。     

小麦发育期对冬季积温变化的响应分析

利用沁阳站1980-2007年冬季积温和小麦发育期资料,分析了冬季积温和小麦发育期的变化规律,用相关分析和典型年份对比方法探讨了冬季积温对小麦发育期的影响.结果表明:1980-2007年冬季积温增加率为6.8(℃·d)/a,1995年以后小麦发育期基本持续提前;冬季积温与冬小麦各发育期呈负相关,最显著的是起身期,其次是抽穗、开花、返青期;冬季积温典型偏高年份作物平均发育期比典型偏低年份的早,最明显的是起身期,提前了26 d,其次是返青期为21 d,再次是全生育期为16 d.