The Statistical Laws And Symmetrical Structures Of Major Meteorological Disasters In Guangxi

The global warming is intensifying in recent decades,it is urgent to have a clear understanding of regional natural disasters in order to protect human wellbeing.Guangxi province is located in the southern coastal areas in China.Influenced by the South Asian monsoon and the East Asian monsoon double impact,this region suffers drought and floods frequently.In addition,the district also under serious attack of typhoon,leading to heavy losses every year.In this paper,we analyzed the spatiotemporal characters of drought,flood and typhoon in Guangxi based on meteorological data,Z index of drought and flood,trend analysis,Mann-Kendall method and commensurability symmetry method.We also investigated the statistical regularity of these natural disasters,and explored the possibility trend of recurrence.Besides,we also analyzed the correlation between natural disasters(i.e.,drought and flood and typhoon)and macroscale driving factors(i.e.,ENSO events and sunspots),aiming to provide scientific reference for the disaster management and helping reduce regional disaster losses.The main conclusions are as follows:(1)The temperature in Guangxi and its sub-regions all showed an increasing trend during 1960 to 2015.The temperature had an abrupt change in the 1990s,after then increasing trend became more significant.The spatial pattern of annual average temperature in Guangxi has an obvious latitude zonality,while the climate tendency rate of temperature reduced from southeast to northwest,and also decreased from central to the north and south.Seen from the change in each season,the climate tendency rate of temperatures reduced from east to west in the spring and winter overall;and the distribution pattern of the tendency rate in summer and autumn look like a stripe.In addition,the tendency rates of four seasonal temperature presented as:autumn>summer>spring>winter.(2)The annual precipitation in the east of Guangxi showed an increasing tendency from 1960 to 2015.The precipitation decreased in the west,and the increasing rate of precipitation in the east was higher than the decreasing rate precipitation in the west.The climate in Guangxi tend to be wetter and warmer.The seasonal precipitation all showed an increasing trend except the spring.In space,the spatial distribution of precipitation in spring and winter were similar to the annual precipitation:decreasing from southeast to northwest gradually;The spatial distribution of precipitation in summer and autumn decreased gradually as a whole from south to north.The change rate of annual and summer precipitation declined gradually from southeast to northwest.The change rate of precipitation in the Winter all showed a increasing trend.(3)From 1470 to 1959,the frequency and scope of drought and flood in Guangxi region presented an increasing tendency.The increasing rates of flood and drought coverage were 0.30%/10 a,0.27%/10 a,and the annual mean values were 24.2%and 19.79%,respectively.Since 1960,the western Guangxi showed a dry trend,while in the east,it tended to be wetter,which was consistent with the trend of precipitation in east and west of Guangxi.In space,the frequency of annual drought and flood in Guangxi was higher in the west while lower in the east.The frequency of flood in spring,summer and winter were stripped,while in autumn the spatial pattern looks like a circle.The frequency of drought in the spring was high in the southeast and was low in the northwest,while in summer it showed the opposite tendency;The frequency of drought in winter was low in the northeast and high in the southwest.Overall,the differences among locations was small.(4)In the past 56 years,there were obvious seasonal differences in the four seasons of Guangxi.The spring and autumn tended to be drier and summer and winter tended to be wetter.The intensity of drought and flood in spring was small and the frequency was lower.The intensity of drought and flood in summer,autumn and winter was large,and also the frequency was high.(5)According to the calculation,the butterfly structure and the commensurability structure,there is a significant temporal symmetry of flood and drought in the whole region and in each district of Guangxi.In the next 10 years,serious autumn flood and winter drought are likely to occur in 2016 in Guangxi,and wide range of autumn drought are likely to occur in 2017.Besides,serious summer drought may occur in 2018.In the northeastern part of Guangxi in 2016,severe spring floods and autumn drought may occur.In 2017,the occurrence possibility of winter drought and autumn floods may be high.In the southeastern part of Guangxi,there may be serious autumn floods and winter drought in 2016,and summer and winter floods in 2017.In the northwest of Guangxi,severe summer floods may occur in 2016.In addition,severe spring drought,summer floods and winter floods are more likely to occur in 2017.In the southwest of Guangxi,there may be serious floods in the autumn and winter,and the possibility of severe autumn droughtis large in 2017,and it may occur serious summer flood in 2018.(6)The number of typhoons in Guangxi was decreasing from 1960 to 2015.Influenced by the subtropical high pressure in the northwest Pacific and the cold air,the type of typhoon affecting Guangxi was dominated by the class-?-path,while the class-I-path and the class-III-path is the least.The typhoon frequency was single-peaked and presented as normal distribution.The occurrence of typhoon mainly concentrated in the June and September,accounting for 90.1%of the total number of typhoons.The visit of typhoon in Guangxi led to intensive tropical depression and tropical storms,accounting for 30%of the total number of visit.The 10-above-typhoon visiting Guangxi has a good commensurability,and in the next 10 years,the signal of 10-above-typhoon attacking Guangxi was strongest in 2017,followed by 2018.(7)The were good correlations between the natural disasters(such as severe drought,flood and typhoon events)and driving forces(i.e.,the ENSO events and sunspots)in Guangxi.In the case of drought and flood,severe drought and flooding mostly occurred in EL Nino years,while seldom occurred in LA Nino year.The correlation between severe flood and ENSO event was higher than the correlation between drought and ENSO event,and serious drought were more likely occur in years when sunspot number were decreasing.In the case of typhoon,the 10-above-typhoon in Guangxi were more active in years when EL Nino came.In addition,the typhoon mainly occurred in the descending phase of sun sunspots.What's more,near the years when sunspots reached the peak,the number of typhoon were more likely to visit Guangxi compared with the years when sunspots reached the valley.Based on the Z-index and the commensurability theory,this paper explored the symmetry and future tendency of severe drought,flood and typhoon since 1960.Besides,we also examined correlation between natural disasters and ENSO events,sunspots.In addition,this study worked on the butterfly structure according to the random probability.This study has the potential of enriching the method of predicting natural disasters,and strengthening the practical application of the commensurability theory.Furthermore,the results will help inform disaster prevention and government decision-making.