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Yao S.-R.,Meteorological Institute of Hebei Province | Yao S.-R.,Hebei Provincial Key Laboratory for Meteorological and Eco Environment | Huo Z.-G.,Chinese Academy of Meteorological Sciences | Dong Z.-Q.,Handan Meteorological Bureau | And 2 more authors.
Chinese Journal of Ecology | Year: 2013

In order to explore the dynamic relations between wheat powdery epidemic and meteorological conditions, the hourly canopy air temperature and humidity in a representative winter wheat field were measured by a field monitoring system in the wheat powdery mildew season in 2010-2012. Meanwhile, the daily wheat powdery mildew density was also investigated in the same field. By using these measured data and the standard weather station data, the correlations of the wheat powdery mildew epidemic speed with the canopy's and ambient air temperature and humidity and their diurnal variations up to five days ahead of the powdery mildew epidemic were analyzed. The conception of 'daily accumulated critical high air temperature hours' was proposed to present the favorability of weather conditions to powdery mildew epidemic speed, and a set of meteorological grade indices was developed to classify the wheat powdery mildew epidemic speed. The powdery mildew epidemic forecast model based on the relationship analysis of air temperature and humidity was established, with the validation accuracy of 88%. The validation accuracy of the indices in 2009 and 2010 was 67% and 84%, respectively, and the forecasting accuracy in 2012 was 87%. It was suggested that the established meteorological grade indices and forecast model were applicable to the monitoring, forecasting, and assessment of winter wheat powdery mildew epidemic. This study could provide references to the plant pathology research and crop epidemics forecast.

Chai D.-H.,Hebei Meteorological Observatory | Chai D.-H.,Hebei Eco Environmental Monitoring Laboratory | Yang X.-L.,Hebei Meteorological Observatory | Li J.-B.,Hebei Meteorological Observatory | And 4 more authors.
Journal of Natural Disasters | Year: 2010

In the late December 2007, the greenhouse vegetables underwent serious damage over the central and southern plains of Hebei Province, leading to a considerable reduction of vegetable production. The main weather environment causing this disaster is the persistent heavy frog, which resulted from the long-duration of high humidity , lack of sunshine and low temperature. The high level westerly wind, preventing the cold air from high latitude intruding the plain, and the cold air spreading from the surface high pressure are suitable for the formation of heavy fog. In the early stage of the heavy fog, the low - level southerly wind, the water vapor convergence and the lowlevel shear provided good water vapor condition for the fog. The formation and maintenance of the temperature inversion produce the favorable stratification condition. Small northerly wind at night and little cloud are suitable for the formation of droplet. The strong cold air intrusion is the main cause for the persistent heavy fog. This work presents key points for persistent fog prediction and the disaster prevention measures for greenhouses vegetables.

Yao S.-R.,Meteorological Institute of Hebei Province | Yao S.-R.,Hebei Provincial Key Laboratory for Meteorological and Eco Environment | Huo Z.-G.,Chinese Academy of Meteorological Sciences | Si L.-L.,Baoding Meteorological Bureau
Chinese Journal of Ecology | Year: 2013

Temperature and humidity are the most important meteorological elements affecting the epidemics of wheat powdery mildew. Based on the wheat powdery mildew epidemics data in the main wheat production areas in Hebei Province in 1987-2010 and the related meteorological data, and by the methods of composite analysis and rank correlation analysis, the key meteorological factors affecting the wheat powdery mildew epidemics were set up. According to the rule of thumb, the epidemic degree of the powdery mildew was distinguished by the anomaly of temperature and the anomaly of humidity climate at different epidemic stages of the powdery mildew, and the year types and controlling factors of the powdery mildew epidemics were determined. From the validation of historical data, the general accordance ratio was 84%. By using the extrapolated controlling factors values of the powdery mildew epidemics in 2011 and 2012, the forecast accuracy was 100%. When integrated with the climate year types, the forecast accuracy was above 85%. Our results could provide scientific references for the assessment and long-term forecast of wheat powdery mildew epidemics.

Zhang J.,Chinese Academy of Meteorological Sciences | Yao F.,University of Chinese Academy of Sciences | Li L.,Chinese Academy of Meteorological Sciences | Li L.,Meteorology Research Institute of Guangxi Zhuang Autonomous Region | Zhang W.,Meteorological Institute of Hebei Province
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2010

The controlling experiment of soil moisture was carried out for the study of crop water spectral features affected by the drought in crop early growth and development stages. The spectra of winter wheat were measured using field spectral radiometer in Gucheng Experiment Station of Heibei Province, and normalized difference water index (NDWI) and simple radio water index (SRWI) were calculated, respectively. Meanwhile, the canopy physiological indexes including chlorophyll concentration (Chl), leaf area index (LAI), plant height (H), leaf relative water content (LRWC) and soil moisture (SM) were measured. The results show that there were significant correlations between canopy physiological indexes of winter wheat and SM, the largest correlation coefficient is 0.657, which indicated that crop early photosynthetic and growth were directly affected by the soil moisture. The correlation coefficient is 0.545 among NDWI/SRWI and SM, which show a weak correlation; whereas, there are not obvious between physiological indexes of winter wheat and WI; especially, the correlation coefficient is just equal to 0.175 among NDWI/SRWI and LRWC. The conclusion was that the water index implied the soil moisture condition instead of crop water content in the low coverage crop growing period.

Li H.,Chinese Academy of Sciences | Li C.,Meteorological Institute of Hebei Province | Lin Y.,State Oceanic Administration | Lei Y.,Chinese Academy of Sciences
Journal of Food, Agriculture and Environment | Year: 2010

The Temperature-Vegetation Dryness Index (TVDI), based on an empirical relationship between land surface temperature (LST) and vegetation index (VI), has been widely used in large area drought monitoring. Temporal and spatial variations of LST and VI (NDVI) over a large area in southern Hebei Plain of China that covers five degrees North latitude are analyzed in this paper. We show that there were significant changes in crop phenological stages and VI in different latitudes giving rise to a parabolic relationship between LST and latitude. The lower LST in the northern area caused by lower air temperature leads to some errors in the use of TVDI. After removal of the influence of lower air temperature on LST, the accuracy of soil moisture monitoring by TVDI is improved compared with observations of soil moisture.

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