Analysis on the Climate Characteristics of Summer Drought Frequency in Chongqing

By using daily meteorological data from 34 surface meteorological stations in Chongqing from 1960 to 2006,the climate characteristics of summer drought in recent 47 years were analyzed by means of Morlet wavelet analysis.The results revealed that summer drought in Chongqing showed obvious decrease trend on the whole,while extreme severe summer drought decreased firstly and then increased,especially since 1990s with obvious increase trend.Around 1995 or 2004,there existed obvious oscillation period of 2-3 years in summer drought in Chongqing,and extreme severe summer drought was very stable without evident oscillation in 1906s,while there was obvious strong oscillation period of 4-5 years in extreme severe summer drought in Chongqing from 1970 to 1978.

Analysis of Changes in Precipitation and Temperature over the Past 60 Years in East China

Based on the mean monthly temperature and precipitation data of East China from 1951 to 2006,we conducted the analysis.The results showed that the mean annual temperature tended to increase in the past 56 years while the variation trend of monthly average temperature was different from the annual one.The obvious increase in temperature happened in early spring and from late autumn to winter.The decrease in temperature happened in summer(August).The precipitation change was not as remarkable as the change in temperature.On the whole,the phase of precipitation change was slightly ahead of temperature change.Continuous wavelet transformation was used to analyze the time-frequency changes of precipitation and temperature in East China and the periodical vibration at different times was obtained.

Relationship between Precipitation Characteristics and Solar Activity in Fuxin from 1951 to 2019

Based on the monthly precipitation data in Fuxin from 1951 to 2019,the M-K and Pettitt mutation test,Morlet wavelet analysis,CWT,XWT and WTC methods were used to study the correlation between precipitation and sunspots in Fuxin in the past 69 years.The results show that from 1951 to 2019,only the spring precipitation in Fuxin showed an upward trend,and annual precipitation,the precipitation in the other three seasons and the annual number of sunspots all showed a relatively obvious downward trend.The first main cycles of annual precipitation,the annual number of sunspots,spring,summer,autumn and winter precipitation were quasi-28,quasi-16,quasi-51,quasi-51,quasi-27 and quasi-11 years,respectively.Annual precipitation,the annual number of sunspots,spring,summer,autumn and winter precipitation changed suddenly in 1980,2005,2005,1980,1992 and 1980,respectively.Both annual precipitation and seasonal precipitation had a relatively obvious resonance cycle of 5-15 years with sunspots,indicating that there was a good correlation between the annual number of sunspots and annual precipitation on an interannual scale.

Spatial-temporal Variation of Air Temperature for the Recent 40 Years in Lhasa

It was all known that Lhasa went through a high temperature of 30.8℃in late June 2019,which hit record highs.To better understand the reasons,based on observations recorded at automatic weather stations in Lhasa,the characteristics of temperature variation at multiple time scales were studied using the linear trend method,Mann-Kendall mutation test,Morlet wavelet analysis,R/S analysis and so on.The results showed that:(a)the annual mean temperature(AMT)is rising at a rate of 0.5℃/10 a,and the average temperature for different seasons also increased significantly,especially in winter.(b)Although there was an intersection in 1995,it was found that AMT,did not pass the reliability test of significance levelα=0.05,this means there are no abrupt changes for AMT,the values are 7.97 and 9.15℃respectively before and after the intersection point.(c)AMT has a periodic oscillation for 18-25 and 25-32 a based on a mass of data and the wavelet variance diagrams in Lhasa.AMT has a main cycle of 28 a,cyclic patterns of temperature changes in spring,summer and autumn is similar to AMT,but it is relatively complex in winter.(d)The Hurst index of AMT and different seasons demonstrates that the temperature is likely to continue to rise in the future in Lhasa.

Spatial Distribution and Temporal Variation of the Winter Wheat Late Frost Disaster in Henan,China

The winter wheat late frost disaster（WFD） occurs mainly in the Yellow and Huaihe River area,of which Henan Province covers the most part.Henan is the major area of wheat production in China,but it is severely hit by the WFD.In this study,we construct a WFD index based on the minimum temperature and the winter wheat development period（WDP）.The WFD degrees and days at 30 agrometeorological stations in Henan Province during the period of 1981-2004 are calculated.For the large-scale temporal variation analysis of WFD,the 24-yr WDP observation series is relatively short,so it is expanded by using the relation between the turning green date of winter wheat and the 5-day running mean temperature and that between the stem elongation phase and the effective cumulative temperature above a critical value of 2.5 ℃.The WFD data are also expanded for the last 50 years and are analyzed by using the empirical orthogonal function（EOF） and the Morlet wavelet methods.Characteristics in the spatial distribution and temporal variation of WFD are revealed.The results show that the frequency of WFD is generally high,exceeding 40% in parts of Henan,and exhibits a rising trend in the period of 1970-1990.The variation trend of WFD degrees is similar to that of WFD days,and the areas with higher WFD degrees coincide the areas with more WFD days.Moreover,the WFD degree has a greater impact on the winter wheat yield than the WFD days.The areas with high WFD degrees lie in the southeast and southwest of Henan,and the areas with low WFD degrees lie in the south of the Huaihe River and parts of western Henan.Temporal variations of the first and second EOF modes of the WFD degree display 16-and quasi-22-yr periodicities,respectively.The areas of high（low） WFD frequency are distributed in the northern Henan and the southwest border of Henan（the northeast Henan and the middle part of southwest Henan）.The temporal variation of the first（second） EOF mode of WFD days exhibits a periodicity（periodicities） of quasi-4 yr（quasi-3 and quasi-6-7 yr）.