鄂东地区人工影响天气应急作业基地建设探讨

人工影响天气工作是气象部门防灾减灾的重要技术手段,而人工影响天气作业应急基地建设又是人工影响天气工作的基础。在鄂东地区人工影响天气应急作业基地建设需求分析的基础上,介绍了鄂东地区人工影响天气应急作业基地的建设目标及建设内容,并阐述了相应的保障措施。     

2012年2月青海省天气特征分析

2012年2月,青海省平均降水量为5.1 mm,比常年同期偏多60%,为近10年来历史同期最多;月平均气温为-6.8℃,较常年同期温度偏高0.3℃;共有3次冷空气过程。对2月青海天气特征进行了分析,探讨了此次天气过程形成的气候背景、成因等。     

影响烟幕现象的成因分析

文章从影响冬季满洲里地区能见度的天气现象烟幕的成因分析出发,利用1957-2009年烟幕出现的次数进行分析,找出烟幕冬季的月年变化规律。统计发现,满洲里地区烟幕日主要集中在冬季的11月至次年的2月。并通过满洲里地区近10年烟幕资料详细分析,结合烟幕发生时的天气特征,以及烟幕与各种天气要素之间的关系,找出烟幕现象的气象预报着眼点。发现烟幕日多产生在高压系统控制下,冬季烟尘排放量多于其他季节、风速较小、大气层结稳定(常有逆温层存在)是多烟幕的主要原因。     

2010、2012年白山红土崖冰雹天气多普勒雷达资料特征分析

通过对2010、2012年白山红土崖两场冰雹天气的多普勒雷达资料分析,可通过实时监控冰雹特征资料,对预报员提早做出提醒,有利于冰雹天气预报预警.     

Detection of Windthrow in Mountainous Regions with Different Remote Sensing Data and Classification Methods

After a disastrous storm event, quick and reliable information on the extent of forest damage is required. This study evaluated different remote sensing data and methods to detect windthrown forests in mountainous regions as an alternative to the manual analysis of aerial images or terrestrial methods. To this end, both optical satellite sensors (Landsat-7, Spot-4 and Ikonos) and synthetic aperture radar (SAR) data at various frequencies (X-, L-, P- and C-band) were evaluated, and classifications of the windthrown forests were performed. This study was designed to state the advantages and disadvantages of the investigated data and methods. Classification results were compared with aerial images which were interpreted manually on a stereoscopic base. The study showed that the manual interpretation of Ikonos data revealed the most accurate results, followed by an automatic classification of Spot-4 data. Except for ERS-1/2 data, which are too inaccurate in mountainous regions, and SAR P-band data, all sensors and methods investigated have different advantages, so the choice of a specific sensor and method will depend on the question being answered.     

News and Views

New forest inventory methods must be developed in order to create good conditions for decision‐making regarding ecological and economical issues in forestry. There are good field measurement methods to use, but they are often very expensive. Coherent all radio band sensing (CARABAS) is a newly developed synthetic aperture radar (SAR) sensor. It differs significantly from the earlier SARs by using longer wavelengths. The CARABAS sensor is more adapted to the scatterers of interest in the forest, due to its longer wavelengths. In this study, CARABAS imagery is compared with forest tree volume. Regression analysis was used to relate radar backscattering to forest tree volume. Due to the large range of incidence angle (45°‐68°), the CARABAS image had to be radiometrically relative‐calibrated. Radar backscattering from five forest stands with similar volume contents were plotted against the distance from the sensor. The plot revealed a linear relationship between these variables. By linear regression on that material the other pixels were relative‐calibrated in the image. Finally, radar backscattering was related to forest stand volumes by using linear regression. The results showed that the backscattering component of the CARABAS imagery is highly correlated to forest tree volume (R² = 74.9%). In this material, there seemed to be no saturation level of the backscattering component up to 300 m³ ha^?1.     

The effect of weather on the occurrence and magnitude of periparturient rise in trichostronglyid nematode egg output in Dorper ewes in a semi-arid area of Kajiado District of Kenya

An investigation was carried out to assess the effects of weather on the occurrence and magnitude of the periparturient rise (PPR) in trichostrongylid nematode egg output in breeding Dorper ewes. The study was conducted over three breeding seasons on a ranch in the semi-arid area of Kajiado District in Kenya between June 1999 and December 2001. During each breeding season 20 ewes randomly selected from the breeding stock and 20 others selected from the unmated yearlings were monitored for faecal strongyle egg counts every 3 weeks. The lambing seasons were timed to coincide with the onset of the short rains (October–November 1999), the mid-short rains (November–December 2000) and the end of the dry season (September–October 2001). In each season higher egg outputs were recorded in the peri-parturient ewes compared to the unmated yearlings. The highest PPR occurred in September 2001, when lambing coincided with the end of the dry season, possibly as a result of maturation of hypobiotic larvae. The lowest PPR occurred in November 2000 when the onset of lambing coincided with the mid-short rains, possibly owing to low pasture infectivity associated with a long dry spell between January and October of the same year. The results of this study indicate that PPR occurred when lambing coincided with both the wet and the dry seasons. However, the magnitude was greatly influenced by the season when lambing occurred. It was also influenced by resumption of development of hypobiotic larvae and the nutritional status of the ewes. Not only should control of gastrointestinal nematode parasites in this area aim at preventing the occurrence of PPR by treating ewes 2–3 weeks before they are to lamb and during lactation, but the anthelmintic used must also eliminate hypobiotic larvae. In addition, the animals must be given supplementary feeding during this period.     

内蒙古奈曼旗土地沙漠化及灾害性天气与农业生产的关系

本文简要论述了奈曼旗沙漠化现状与成因，以及在沙漠化环境下风沙、干旱等天气灾害发生的气候特点、根据奈曼旗多年产量资料，气象资料、农业受害记录，并运用干旱型的划分方法，探讨了风沙、干旱对农业生产的影响，针对天气灾害的气候特点及本区的自然环境条件，提出了一些减轻灾害、提高农业生产的有效措施。     

Characteristic ‘fingerprints’ of crop model responses to weather input data at different spatial resolutions

Crop growth simulation models are increasingly used for regionally assessing the effects of climate change and variability on crop yields. These models require spatially and temporally detailed, location-specific, environmental (weather and soil) and management data as inputs, which are often difficult to obtain consistently for larger regions. Aggregating the resolution of input data for crop model applications may increase the uncertainty of simulations to an extent that is not well understood. The present study aims to systematically analyse the effect of changes in the spatial resolution of weather input data on yields simulated by four crop models (LINTUL-SLIM, DSSAT-CSM, EPIC and WOFOST) which were utilized to test possible interactions between weather input data resolution and specific modelling approaches representing different degrees of complexity. The models were applied to simulate grain yield of spring barley in Finland for 12 years between 1994 and 2005 considering five spatial resolutions of daily weather data: weather station (point) and grid-based interpolated data at resolutions of 10 km × 10 km; 20 km × 20 km; 50 km × 50 km and 100 km × 100 km. Our results show that the differences between models were larger than the effect of the chosen spatial resolution of weather data for the considered years and region. When displaying model results graphically, each model exhibits a characteristic ‘fingerprint’ of simulated yield frequency distributions. These characteristic distributions in response to the inter-annual weather variability were independent of the spatial resolution of weather input data. Using one model (LINTUL-SLIM), we analysed how the aggregation strategy, i.e. aggregating model input versus model output data, influences the simulated yield frequency distribution. Results show that aggregating weather data has a smaller effect on the yield distribution than aggregating simulated yields which causes a deformation of the model fingerprint. We conclude that changes in the spatial resolution of weather input data introduce less uncertainty to the simulations than the use of different crop models but that more evaluation is required for other regions with a higher spatial heterogeneity in weather conditions, and for other input data related to soil and crop management to substantiate our findings. Our results provide further evidence to support other studies stressing the importance of using not just one, but different crop models in climate assessment studies.     

用扫频成像法探测浅层管道

针对超宽带雷达探测浅层管道存在的困难，依据时频变换方法，提出了用扫频成像法，探测深度在２．５ｍ以上内地埋地管道。采用矢量风络分析对不同间距的两条管道进行了伪彩色成像，经信号处理得到了准确的三维立体图像。