Research On The Effects Of ENSO On Drought In Four Regions Of Liaoning Province Based On SPEI

With the occurrence of global warming,climate issues are also getting more and more attention.Precipitation in North China continues to decrease over the past decades,and extreme weather has significantly increased nearly ten years compared to the past 30 years,drought disasters occur more and more frequently.As a national agricultural province,Liaoning Province is also severely affected by the drought issue.ENSO is the strongest interannual change signal in the global marine steam system,and it is also an important factor affecting precipitation in Liaoning Province's spring and summer.Study on the influence of ENSO helps to understand the mechanism of drought in Liaoning Province.In this paper,we used monthly and yearly data of 52 meteorological observing stations with good quality and continuity are distributed evenly in Liaoning Province from 1961 to 2017,and the SSTA data of Nino3.4 in NOAA of the United States,then using climate statistics method to calculate the spatial distribution of temperature and precipitation,seasonal differences and interannual variations at average and every station in Liaoning Province first.to study the impact of ENSO incident on drought in different regions of Liaoning Province based on standardized precipitation evapotranspiration index SPEI.The main results are as follows:(1)The average temperature in Liaoning Province has shown a tendency of fluctuation and rise,its climate trend rate has reached 0.27?·10a-1 fluctuation,the Pearson correlation coefficient of ENSO warm and cold events and temperatures is 0.083,it didn't pass the significance test and there was no obvious connection.The annual average precipitation in the province has shown a tendency of fluctuation and decrease,its climate tendency is-6.8mm·a-1.The average annual precipitation in Liaoning Province is negatively correlated with ENSO intensity,the Pearson correlation coefficient is-0.313,P<0.05,it passed the significance test,so proves that ENSO cold and warm events have a direct compact on the annual average precipitation in Liaoning Province.(2)There is no significant correlation between the ENSO event and the annual average temperature in Liaoning Province,but there is a significant correlation with average annual precipitation.The stronger the intensity level of ENSO events,the greater the possibility of decreasing precipitation,the stronger the strength of ENSO cold event,the greater the possibility of increased precipitation.(3)According to the meaning of SPEI index,mild drought 12 times in 57 years,moderate drought 4 times in Liaoning Province.The most abnormal SPEI index year is 2014,the average value is-1.612.The intensity of ENSO events is negatively correlated with the yearly average SPEI index,when the ENSO warm event occurs,the probability of drought is higher,and the stronger the strength of warm events,the greater the possibility of serious drought.(4)The ENSO event has poor correlation with the annual mean temperature of the four regions and there is no significant correlation.This shows that the ENSO event has no significant effect on the temperature.However,ENSO has a significant negative correlation with precipitation and SPEI index in central and northern Liaoning.When the ENSO event occurs,warmer precipitation decrease,drought is mainly enhanced,cold precipitation increases,drought is mainly weaken or turns floods.The phenomenon of ENSO warm event drought in Western Liaoning is mainly enhanced,the impact of cold events is not obvious.There is a significant negative correlation between ENSO warm event intensity and annual precipitation and SPEI index,there is poor correlation with cold events.Annual precipitation in eastern Liaoning is weakly related to ENSO event ratings,ENSO event intensity has a weak influence on the annual precipitation and SPEI index in Eastern Liaoning,but not a significant factor.The annual precipitation in southern Liaoning is negatively correlated with the level of ENSO events,and there is no significant correlation with SPEI index,ENSO event has a weaker impact on southern Liaoning,so ENSO events are not a significant factor for drought in this area.(5)When the ENSO warm event occurs,the aggravating trend caused by the event was the best response in Anshan,Yingkou,Liaozhong and Heishan in the central and southern part of Liaoning province,Secondly,the response of Fuxin,Jinzhou,the east of Huludao,Liaoyang,Xinmin,Kangping,Xiuyan and other places was second.In the event of ENSO warming,the areas mentioned above should be strengthened in the prevention and preparation of drought to reduce the damage to agricultural production.(6)The main reason for the impact of the ENSO incident on precipitation and drought disasters in Liaoning is the impact of Abnormal Sea Surface Temperature in Nino3.4 on Atmospheric Circulation over the Western Pacific Ocean.When the ENSO warm event occurs,Western Pacific subtropical high southward weak,water vapor in the Western Pacific is difficult to reach the Liaoning region due to the subtropical high over the Western Pacific,so caused a decrease in rainfall in Liaoning Province;When an ENSO cold event occurs,Western Pacific subtropical high northward strong,water vapor in the Western Pacific rises along the subtropical high over the Western Pacific to reach precipitation in Liaoning leading to increased precipitation in Liaoning,drought turns weak and even disasters occur.