| Temperature is an important weather indicator,and its abnormal changes will have an important impact on the local climate change.The change of regional extreme climate events related to severe weather events such as cold and heat waves are also important aspects of climate change.This study selected daily weather data from 169 meteorological stations in North China and surrounding areas from 1960 to 2018,and used national standards for high temperature heat waves and cold wave indicators applicable to the region to identify meteorological disasters caused by temperature anomalies in the past 59 years.Geostatistics and other methods were used to analyze the temporal and spatial evolution and explore the changing relationship between the heat waves and cold wave disasters.Analyze the impact of small-scale local meteorological factors and large-scale circulation factors on temperature anomalies,and explore the response relationship of temperature anomalies in North China to climate change.The main results were listed as follows:(1)In terms of spatial distribution,the cold wave at a single station in North China is greatly affected by latitude and altitude,and it gradually increases from south to north.The frequency of occurrence in the northern Mountain of Hebei and Liaodong hills is the highest,and the frequency in Shandong hills is lower.In terms of interannual changes,the cold wave at a single station at different degrees is decreasing.The interannual tendency rates of single-station cold wave,strong cold wave,and extra-strong cold wave decreased by 0.38,0.2 and 0.13 times per decade,respectively.In the 1960 s,the cold wave had the highest frequency and the largest impact area.In terms of occurrence time,the single-station cold wave occurred in November the most,followed by January and December,the cold wave showed a decreasing trend in each month;the seasonal distribution was more in winter than in autumn than in spring.In the past 59 years,the start time of the cold wave has been delayed and the end time has been advanced.The delay and advance trends have decreased by 1.7 days and 2.4 days per decade,respectively.Regional cold waves of different scales occurred most in the 1960 s,and the interannual changes showed a decreasing trend.In November,the number of large-scale cooling processes in North China was the largest.(2)In terms of spatial distribution,the high value area of single station heat wave in North China is distributed in the Huang-Huai-Hai Plain and the southeast of the Loess Plateau,and the number of days of occurrence is negatively correlated with latitude and altitude.In terms of inter-annual changes,the number of heat wave days generally shows an increasing trend.The inter-annual propensity rate increases by 0.41 days per decade.The northern Liaoning hills have the most significant increase,showing a more-less-more distribution trend in the inter-decadal period.After the 1990 s,the number of heat wave days has increased significantly,and the impact range has expanded significantly.In the time of occurrence,the heat wave mainly occurred in summer,and the most occurred in July,followed by June and August.The duration of the heat wave is the longest in the Huang-Huai-Hai Plain and the southeast of the Loess Plateau.The inter-annual variability was first reduced and then increased,and the duration increased significantly after 2000.The start and end dates are greatly affected by the latitude.The start order is delayed and then advanced,while the end order is changed first advanced and then delayed.Regional heat waves have the largest number of days in the middle and late July.After changing from less to more in the 1980 s,the range and frequency of regional heat waves have become larger and higher.(3)Comparing the climatic characteristics of the heat wave and cold wave in North China,the heat wave and cold wave have obvious phase characteristics in interannual variation.From the 1960 s to the early 1970 s,there were more heat waves and cold waves.From 1970 to the end of the 1980 s,there were more years with abnormally high cold waves and heat waves were abnormally less during this period.After the 1990 s,the frequency of cold waves was unusually low and the number of heat wave days was abnormally high in most years.The 5-year moving average change curve shows that before 1984,the heat wave and cold wave trends were similar and showed a very significant positive correlation,and after 1984,the change trends of the two showed a very significant negative correlation.(4)The cold wave is mostly negatively correlated with the temperature and positively correlated with the average wind speed.The changes in the average temperature,minimum temperature,and wind speed among the major meteorological elements have a greater impact on the cold wave.Correlation coefficients of various meteorological elements and cold waves are relatively high in the eastern and northern parts of North China,and the correlation between cold waves and various meteorological elements in the western Loess Plateau is poor.On the relationship between large-scale circulation factors and cold wave,AOI has increased in recent 59 years,and the interannual tendency rate has increased by 0.11 per decade.After 1990,the number of winter AOI positive phase years increased significantly.The frequency of cold wave at a single station was positively correlated with AOI,and the months with frequent cold waves were extremely significantly negatively correlated with AOI during the same period.The regional cold wave in North China is negatively correlated with AOI,and the AO in January and February has the greatest impact on the regional cold wave.(5)Heat waves are mostly positively correlated with air temperature and negatively correlated with changes in relative humidity.As an important index of heat wave,the change of relative humidity has a negative correlation with the number of heat wave days,indicating that the maximum temperature has a greater impact on the heat wave index than relative humidity.The number of heat wave days in the Huang-huai-hai Plain in the 1960 s was due to its high maximum temperature and relative humidity.After 2000,the relative humidity in the region decreased,but the number of heatwave days increased,indicating that the increase in heat waves in the Huang-huai-hai Plain after 2000 Impact of rising maximum temperatures.In terms of the correlation between the heat wave and large-scale circulation factors,the area of the WPSH in the summer has increased,the intensity has increased,and the western extension of the ridge point has moved westward.In summer,the WPSH has a relatively large impact on heat waves in the hills of Shandong and eastern Liaoning.In July,the correlation between the heat wave intensity and the WPSH intensity in the same and earlier periods is mostly positive in the western part of North China,negative in the eastern part of North China,with a significant positive correlation with the ridgeline location in the southern Huang-huai-hai Plain.The south of the plain is controlled by the sub-high,which increases the number of heat wave days.In August,the heat wave is mostly positively correlated with the location of the ridgeline.In August,when the ridgeline is north,it controls the North China area,which increases the number of days and intensity of heat waves.When the WPSH is in a negative phase,regional heat waves occur more days. |
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