Analysis of Climate Change and Circulation Features of Frost Days in Hunan Province, China in Recent 67 Years

This paper provides a basis for crop structure adjustment and selection of suitable growth period varieties in Hunan Province of China, and improves the predictive capacity of Hunan’s abnormal frost disasters to defend against frost disasters effectively. Using the frost date data of 97 meteorological monitoring stations in Hunan Province from 1951 to 2017, statistical analysis was carried out on the variable characteristics of frost days, initial and final frost days and frost-free periods. The NCEP/NCAR data were used to study the circulation characteristics of the province’s frosty weather by linear and polynomial fitting methods to show that: 1) The frost days decrease −0.1 d/a from December to January. 2) The inter-annual rate of change in the initial and final frost days and frost-free period is large, and the average first frost day showed a delayed trend (0.13 d/a). The average final frost day showed an early change trend (−0.12 d/a), and the average frost-free period showed an extended trend (0.22 d/a). 3) The frosty weather in Hunan Province has obvious geographical distribution characteristics. The first frost day showed distribution characteristics of “early in the east and later in the west”, and the final frost day showed the distribution characteristics of “early in the south and later in the north”. The frost-free period showed the distribution pattern of “long in the south and short in the north”. 4) The circulation characteristic values of the frosty days are as follows: 500 hPa East Asian trough is stable, and the temperature field has a cold tongue of −40°C. The −12°C line is located in south part of Hunan and the 0°C line of 850 hPa is stretched to Hubei. Meanwhile, the ground has cold high pressure, and the center pressure is greater than 1025 hPa. These findings could be used for adjusting crop structure, select suitable varieties for growth in Hunan and predicted abnormal frost disasters for effective prevention.

The Variation of Extreme Temperature and Precipitation in Shandong Province during 1961-2008

We drew on data of daily average temperature,average maximum temperature,average minimum temperature and precipitation from 78 meteorological stations during 1961-2008 of Shandong Province,analyzed the variation of extreme temperature and precipitation events.The results showed that although extreme cold days decreased by 0.23 d/a on average,after the average temperature steadily passed 10 ℃ in spring,it would still appear 1-2 days of frost,wheat and fruit trees would still suffer frozen injury every year in the central Shandong and the inland of Shandong Peninsula.Although the number of annual extreme hot days has an increasing trend obviously in Shandong and increased by 0.19 days a year.After 2000,aimed at the days of daily maximum temperature ≥ 35 ℃,the mean value and standard deviation of daily maximum temperature in summer decreased comparing with the normal year in West Shandong,and decreased by 1-3 days.In recent 50 years,the extreme precipitation trend increased,but not statistically significant.The number of light rain days has a decreasing trend and decreased by 0.17 days every year,in contrast,the frequency of downpour has an increasing trend.

Trend and Periodicity of Temperature Time Series in Ontario

The trends and periodicities in the annual and seasonal temperature time series at fifteen weather stations within Ontario Great Lakes Basins have been analyzed, for the period 1941-2005, using the statistical analyses (Fourier series analysis, t-test, and Mann-Kendall test). The stations were spatially divided into three regions: northwest (NW), southwest (SW), and southeast (SE) to evaluate spatial variability in temperature. The results of the study reveal that the annual maximum mean temperature showed increasing trend for NW, and mixed trends for SW and SE regions. The variability was found to be more for northern stations as compared to southern stations for annual extreme minimum temperature. In addition, the trend slope per 100 years for the average annual extreme minimum temperature increased within the range of -0.8°C (Stratford) to 15°C (Porcupine). The seasonal analysis demonstrated that extreme maximum temperature has an increasing trend and maximum mean temperature has a decreasing trend during summer and winter. The extreme minimum temperature for winter illustrated an increasing trend (90%) with 22% statistically significant for NW region. For the SW region, the trend is also increasing (80%) for most of the temperature variables and 25% of temperature data were significantly increased in the SW region. The SE region stations showed overall very clear increasing trends (95%) for all the temperature variables. The data also showed that 47% of data were statistically significant in the SE region. The analysis of variance accounted for by trend, significant periodicities, and random component show that the pattern is similar for the percent of variance accounted for periodicities, and random component contribute dominantly for the four temperature variables and frost free days (FFD) for all three regions. Overall, the study reveals that the extreme minimum temperature is increasing annually and seasonally, with statistically significant at many stations.

我国江淮流域近40年异常初终霜冻的分析

该文用地面最低温度资料，以≤０℃作为霜冻指标，定量地确定出现异常霜冻的判别标准，研究了近４０年初终霜冻异常的气候特征。结果表明：初终霜冻的异常明显存在地区差异。其变化周期以２～３年和准１２年最普遍。其偏离均值大致有两种波型：反向变化和同向变化；前者在淮河流域较突出，后者在长江流域较普遍。当其出现反向变化趋势，且二者偏离均值达最大时，该时期为初霜冻异常偏早（偏晚），终霜冻异常偏晚（偏早）的活跃期。同样，当初、终霜冻出现同向变化时，初、终霜冻异常活跃期亦呈现同向变化。

气候变暖背景下太原市霜冻发生特征及其对农业的影响

基于太原市1951—2008年逐日最低气温资料，按轻微、中度和重度3级霜冻强度，分析了太原市霜冻发生的基本特征；采用累积滤波器法结合非参数统计检验方法分析了太原市霜冻的变化趋势；利用异常霜冻指标，分析了太原市霜冻的异常发生情况。结果表明：1）太原市轻微霜冻平均初霜冻日为10月14日、终霜冻日为4月15日，平均无霜冻期为182d。与轻微霜冻相比，中度、重度霜冻平均初霜冻日分别推后9d和23d，平均终霜冻日分别提前11d和24d，平均无霜冻期分别延长20d和47d。2）各级霜冻强度下，初霜冻日在年代际间的变化较为复杂，终霜冻日则表现为20世纪50—70年代偏晚、80年代之后偏早，无霜冻期表现为50-70年代缩短、80年代之后延长为主的变化特点。3）在d：0．05显著水平下，太原市各级霜冻的初霜冻日呈现显著的推后趋势、终霜冻日呈现显著的提前趋势以及无霜冻期呈现显著的延长趋势，以重度终霜冻日提前趋势最显著。4）太原市轻微偏早初霜冻、中度偏晚终霜冻和重度偏早初霜冻发生频率达15％以上，其余各级异常霜冻的发生频率在5％～10％；大多数异常霜冻发生在50—70年代。5）太原市轻微异常初霜冻对秋粮作物的产量影响较小，中度和重度异常初霜冻会使大白菜遭受不同程度的冻害；春播幼苗主要受到特晚终霜冻的影响；冬小麦遭受终霜冻危害的平均频率为5年一遇，尤以拔节后5d内发生的频率最大。