Research On The Influence Of ENSO Event On The Change Of Water Level Of Qinghai Lake

Qinghai Lake is located at the intersection of the alpine region on the Tibetan Plateau,the arid region in the northwest and the monsoon region in the east.It is a sensitive region of global climate change and a typical vulnerable region of the ecosystem.The change of lake water level is of great significance to the ecological construction and sustainable development of the Qinghai-Tibet and Northwest regions.This article uses the National Climate Center,Qinghai Lake Water Resources Information Network,NCEP / NCAR-?reanalysis data and the SST data of the Hadley Center to focus on the analysis of the impact of ENSO events on lake water level changes in the past 31 years.Correlation analysis,synthetic analysis,regression analysis,EOF decomposition and other methods are used to discuss the variation characteristics and overall trends of precipitation,temperature and water level in the Qinghai Lake area.The following conclusions are drawn:1.In the past 31 years,the temperature change trend of the Qinghai Lake Basin is generally consistent with global warming,and precipitation has undergone a transition from decreasing to increasing,especially since the 21 st century,the increasing trend of precipitation has become increasingly significant,and the climate of the Qinghai Lake Basin has gradually become warmer.Development of humidification.2.The water level of Qinghai Lake has changed significantly in the past 31 years.From the late 1980 s to the beginning of the 21 st century,the water level of Qinghai Lake showed a downward trend,but from 2003,the water level showed an upward trend.Through the Mann-Kendall mutation test,it has been found that since 2005,the water level of Qinghai Lake has increased significantly,and the water level of Qinghai Lake has increased.3.The interannual change of the water level of Qinghai Lake is significantly positively correlated with the change of precipitation in the watershed at the 0.05 confidence level.The abnormal precipitation in the watershed caused the fluctuation of the lake water level.4.According to the time,intensity and distribution of ENSO events in the past 31 years,the analysis shows that the frequency and intensity of ENSO events have shown an overall upward trend,and statistics show that the frequency and intensity of El Ni?o events in recent years are greater than the frequency and intensity of La Ni?a events.5.There is a significant correlation between ENSO events of moderate intensity and above and precipitation.Studies have shown that the greater the intensity of the El Ni?o event,the more obvious the decrease in precipitation in the Qinghai Lake basin at the peak of the event in the following year.As the intensity of the La Ni?a event increases,the precipitation in the Qinghai Lake basin at the peak of the event increases significantly in the following year.6.The analysis shows that there is a correlation between ENSO events and changes in the water level of Qinghai Lake.Medium-energy and above ENSO events are significantly related to changes in the water level of Qinghai Lake,while weak ENSO events are not significantly related to the changes in water level.7.The ENSO event has a significant effect on the distribution of the 100 hpa height field over the Qinghai-Tibet Plateau.In the summer of the following year,the peak of the La Ni?a event above medium intensity,the location of the South Asian high pressure is east and north,and the 200hpa-100 hpa high pressure over the Qinghai Lake basin is increasing.;At 600 hpa altitude,the air pressure shows negative anomalies,cyclonic updrafts strengthen,summer precipitation increases significantly,and lake water levels rise.8.The ENSO event has a significant correlation with the time and intensity of the plateau summer monsoon.In April of the following year,the peak of the La Ni?a event with moderate intensity or higher strengthened the westerly anomalies in the upper equatorial Pacific,the anomalous easterly anomalies in the lower layers,the prevailing easterly anomalies in the upper equatorial Indian Ocean,and the strengthened summer monsoon.At 600 hpa in the Qinghai Lake Basin,the anomalies of east and south winds increased,atmospheric water vapor transport increased,precipitation increased,and the water level of Qinghai Lake increased.Correspondingly,the plateau monsoon weakened in the following year due to the strong El Ni?o event.The rising trend of the water level of Qinghai Lake slowed down or even showed a downward trend.