| Hydrological drought is a serious natural disaster that affects people's normal production and life.Changes in regional meteorological elements often directly affect the occurrence of hydrological drought.Simultaneously,in the context of global climate change,drought events occur frequently,changes in global large-scale climate models directly or indirectly influence the formation of hydrological drought.It is necessary to propose new theories and methods to explore the response of hydrological drought to regional meteorological elements and global large scale climate models.The research results are of great significance for the formation mechanism analysis and forecasting of hydrological drought.In this paper,the standardized runoff index(SRI)for 6 time scales(1,3,6,12,24,48 months)of each hydrological station was established according to the1956-2000 monthly runoff data of the 4 hydrological stations(Shangjingyou,Fenhe Reservoir,Zhaishang,Lancun)in the upper reaches of Fenhe River basin,the trend analysis of the above indexes was carried out.Principal component analysis(PCA)was used to extract regional SRI to characterize regionalhydrological drought from all stations SRI for 1 month time scale.Spatial and temporal evolution of hydrological drought was analyzed on basis of the SRI.Wavelet analysis was applied to explore regional hydrological drought response to regional meteorological elements.Based on the monthly meteorological data of 4 meteorological stations in the upper reaches of Fenhe River basin from1956 to 2000,the basin standardized precipitation index(SPI)and the standardized precipitation evapotranspiration index(SPEI)were established.The 6 time scale SRI of 4 hydrological stations was respectively done correlation analysis with SPI and SPEI of the basin for the same scale during the same time.The time-shift cross-correlation analysis and regression analysis were used to study the response of hydrological drought to meteorological drought.At the same time,wavelet analysis was applied to research the relationship between regional hydrological drought and global climatic factors such as ENSO events,atmospheric oscillations,sunspots,monsoons,atmospheric circulation and so on,to explore influence of global large scale climate changes on hydrological drought.Finally,it was to compare the differences of impacts for climate change and human activities on regional hydrological drought.Main conclusions are as follows:(1)Analysis of the temporal and spatial evolution of hydrological drought in the upper reaches of Fenhe River basin.There is an drought trend during the research period in the upper reaches of Fenhe River basin.The cycle characteristics of the drought are mainly occurredaround the early 1970 s,which shows 32-month and 128-month oscillation cycles.The drought mutation mainly occurs in the early 1970 s and is related with precipitation mutation.There is the strong consistency between spatial distribution of hydrological drought and the spatial distribution of precipitation,the drought in the northwest has relieved,the drought in the southeast has intensified,and the hydrological drought has spread to the southeast.The temporal and spatial variation of hydrological drought at different stations has a strong consistency.(2)Impacts of regional meteorological elements on hydrological drought in the upper reaches of Fenhe River basin.Among many regional meteorological factors,such as precipitation,temperature,evaporation,sunshine,solar radiation,meteorological drought,wind speed,atmospheric pressure,water vapor pressure,precipitation and meteorological drought are the main driving forces for hydrological drought in the upper reaches of Fenhe River basin.There is a 16-128 month resonance period between precipitation and regional hydrological drought SRI,and it shows a strong positive correlation.On the whole,the precipitation is around 1-1.5 months ahead of the drought.At time scale below 12 months,there are also resonance characteristics and positive phase relationships,but the duration is shorter.The precipitation and drought index also exhibit an intermittent quasi-12 month scale resonance period on the12-month time scale.The SPEI and the regional SRI show a strong positive phase relationship.The SPEI leads SRI about 1-1.5 months.In 1956-1969,there are two resonance periods for 12-48 months and 60-72 months.After 1970,the resonance period reachs 128 months,and then resonance period begin to become shorter,mainly distribute in the range of 6-24 and 64-128 months by 1986.The SPEI and the regional SRI also exhibits a 6-24 month resonance period in 1972-1984.The correlation coefficients between hydrological drought and meteorological drought at each station rise first and then decrease with the increase of time scale.On the scale of 12-24 months,the correlation coefficients reach the maximum,and all correlation coefficients pass the significance test;for the same time scale,the correlation coefficients between hydrological drought and meteorological drought at four hydrological stations have a slight difference.Under the 12-month scale,the correlation between SRI and SPEI is closer than that of SRI and SPI,however,the law is opposite above 12 months.The hydrological drought of Fenhe Reservoir,Zhaishang and Lancun station lags behind the meteorological drought about 1 month.(3)Influences of global large-scale climate models on hydrological drought in the upper reaches of Fenhe River basin.ENSO has a stronger impact on regional hydrological drought than other factors,such as AO,NAO,sunspots,PDO,and East Asian monsoons.During the whole study period,there is an negative correlation and resonance cycle between Nino3.4 Index/MEI and the regional SRI.ENSO for El Ni?o eventsprone to trigger drought disaster,ENSO for La Ni?a events mitigate drought,but strong La Ni?a events may also intensify drought.It is prone to induce drought when AO,NAO and PDO are in the positive phase.Large-scale atmospheric circulation factors,especially subtropical high,have an important time frequency impact on hydrological drought in the upper reaches of Fenhe River basin.(4)Comparative analysis for impacts of climate change and human activities on hydrological drought shows that although climate change has an important impact on hydrological drought,the impact of human activities including underlying surface changes,engineering measures,and water consumption on hydrological drought is greater,climate change and human activities are the main driving factors of hydrological drought in the upper reaches of Fenhe River basin. |
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