季节变动的测定和季节预测

一、开展商情预测必须研究季节变动季节变动是指某些社会经济现象受自然因素和社会因素的影响,在一年内随着季节的更换而引起的比较有规律性的变动。市场上大部分商品属于常年生产,常年消费,但是,粮、棉、茶、麻等多数农产品,由于受自然条件的影响,是季节生产,常年消费。如蛋类、乳类春秋两季产量较高,夏冬两季产量较低。瓜果蔬菜多是季节生产,季节消费,如西瓜只在夏季生产,夏季消费。有些商品,如汗衫、背心、绒线等,由于季节变化的影响,属于常年生产,季节消费。有些即使是常年生产、常年消费的日用商品,也由于社会条件的影响。

电力市场环境下的典型产业月用电负荷预测分析

将市场竞争引入电力系统,企业竞争性得到提高,资源利用效率将得到改善。准确的月负荷预测可以提高电力系统的社会效益和经济效益,而负荷预测误差风险直接影响供电的安全性和稳定性。本文考虑到季节成分对月负荷预测的影响,基于季节变差以及季节比例理论建立短期负荷预测的指数平滑模型,并对月负荷原始数据进行预测。通过对蒙东电力的算例分析验证了本文所提出方法的合理性和可行性。

利用移动平均剔除趋势法测定因特网业务受季节变动的影响

以因特网业务为例，利用移动平均剔除趋势法，剔除业务正常增长因素的影响，算出季节或月份变差值，分析因特网业务随着季节或月份的变化业务量变化的情况，从而找出因特网业务随季节或月份变化的规律，以供管理和营销人员针对该业务在不同的季度和月份，制定不同的营销策略，达到充分营销的目的。可以利用文中对业务分析的方法，对具体的电信产品进行细致深入的分析。

Trends in Temperature and Precipitation Extremes over Circum-Bohai-Sea Region,China

Trends in temperature and precipitation extremes from 1961 to 2008 have been investigated over Circum-Bohai-Sea region, China using daily temperature and precipitation data of 63 meteorological stations. The re- suits show that at most stations, there is a significant increase in the annual frequency of warm days and warm nights, as well as a significant decrease in the annual frequency of cold days, cold nights, frost days, and annual diurnal tem- perature range （DTR）. Their regional averaged changes are 2.06 d/1 0yr, 3.95 d/10yr, -1.88 d/10yr, -4.27 d/10yr, -4.21 d/10yr and -0.20℃/10yr, respectively. Seasonal changes display similar patterns to the annual results, but there is a large seasonal difference. A significant warming trend is detected at both annual and seasonal scales, which is more contributed by changes of indices defined by daily minimum temperature than those defined by daily maximum tem- perature. For precipitation indices, the regional annual extreme precipitation displays a weak decrease in terms of magnitude and frequency, i.e. extreme precipitation days （RD95p）, intensity （RINTEN）, proportion （RPROP） and maximum consecutive wet days （CWD）, but a slight increase in the maximum consecutive dry days （CDD）, which are consistent with changes of annual total precipitation （PRCPTOT）. Seasonally, PRCPTOT and RD95p both exhibit an increase in spring and a decrease in other seasons with the largest decrease in summer, but generally not significant. In summary, this study shows a pronounced warming tendency at the less rainy period over Circum-Bohai-Sea region, which may affect regional economic development and ecological protection to some extent.

Variability of Surface Sensible Heat Flux over Northwest China

The present study documents the variability of surface sensible heat flux over Northwest China using station observations for the period 1961 2000.It is found that the afternoon and nighttime sensible heat flux variations are remarkably different.The variability of the instant flux in the afternoon is much larger than in the nighttime.The afternoon and nighttime flux anomalies tend to be opposite.The diurnal and seasonal dependence of sensible heat flux variations is closely related to the diurnal cycle of mean land-air temperature difference.The relationship of sensible heat flux with land-air temperature difference based on the instant value differs from that based on the daily mean.The present study indicates the importance for the models to properly simulate mean land-air temperature difference and its diurnal and seasonal variations in order to capture surface sensible heat flux variability over Northwest China and predicts its plausible impacts on climate.

Decadal Variability of Global Ocean Significant Wave Height

This paper presents the long-term climate changes of significant wave height(Hs) in 1958–2001 over the entire global ocean using the 45-year European Centre for Medium-Range Weather Forecasts(ECMWF) Reanalysis(ERA-40) wave data. The linear trends in Hs and regional and seasonal differences of the linear trends for Hs were calculated. Results show that the Hs exhibits a significant increasing trend of about 4.6 cm decade-1 in the global ocean as a whole over the last 44 years. The Hs changes slowly during the periods 1958–1974 and 1980–1991, while it increases consistently during the periods 1975–1980 and 1995–1998. The Hs reaches its lowest magnitude in 1975, with annual average wave height about 2 m. In 1992, the Hs has the maximum value of nearly 2.60 m. The Hs in most ocean waters has a significant increasing trend of 2–14 cm decade-1 over the last 44 years. The linear trend exhibits great regional differences. Areas with strong increasing trend of Hs are mainly distributed in the westerlies of the southern Hemisphere and the northern Hemisphere. Only some small areas show obvious decreasing in Hs. The long-term trend of Hs in DJF(December, January, February) and MAM(March, April, May) is much more stronger than that in JJA(June, July, August) and SON(September, October, November). The linear trends of the Hs in different areas are different in different seasons; for instance, the increasing trend of Hs in the westerlies of the Pacific Ocean mainly appears in MAM and DJF.

浅谈税收预测(二)——介绍几种税收预测的方法

税收预测是经济预测理论和方法在税收管理中的具体运用。税收预测按预测的范围,可分为宏观预测和微观预测。宏观预测一般是指国家根据国民经济发展变化和税收收入本身的发展趋势,对国家税收收入进行的预测,包括地方性的税收收入的综合预测;微观预测一般指对一个税种、一个品目、一个行业、一个企业进行的税收预测。按预测期长短,可分为短期预测、中期预测、长期预测。短期预测一般指一年以内的预测,如年,季、月、旬的预测;中期预测通常指三至五年的预测;长期预测一般指五年以上的预测。按其性质和方式不同,可分为探索性预测和目标性预测。探索性预测是依据过去和现在的发展状况预见和推断未来;目标性预测是先提出税收收入发展的目标,然后再预测实现目标的时间。