Spatio-Temporal Characteristics Of Meteorological Drought Using NSPEI In Qinghai Province Based On GAMLSS Model

Meteorological drought is related to human production and life,the stability of the whole society and economy and the sustainable development of the natural ecosystem.At present,under the environment of climate change,the statistical parameters of precipitation and temperature series change with time,and the stationarity characteristics of meteorological series no longer exist.If the traditional hydrological analysis method based on stationarity assumption is still used to construct meteorological drought index,the monitoring and identification results will have errors or even errors.In order to cope with the non-stationarity of precipitation and temperature series under the influence of climate change,this paper identifies the non-stationarity of 12-month scale precipitation and temperature series based on the measured data of 30 meteorological stations in Qinghai Province from 1961 to 2020,and analyzes the time-delay correlation between precipitation and air circulation.Generalized Additive Models for Location,Scale and Shape,Generalized additive models for location,scale and shape,GAMLSS)constructed the nonstationary Precipitation Evapotranspiration Index(NSPEI)with climate factors as covariable,and compared NSPEI and traditional SPEI based on the actual historical disaster situation.To select a more suitable meteorological drought index for Qinghai province.The Copula theory was used to reveal the temporal and spatial evolution of drought characteristics in Qinghai Province,analyze the distribution characteristics of drought characteristics in different scenarios and evaluate the prediction performance of non-stationary model.The results show that:(1)The annual precipitation of Qinghai Province showed an insignificant upward trend from 1961 to 2020,and the decline rate was the fastest in the 1980s and 1990s.The precipitation series had an insignificant mutation in 2001,and the precipitation changed from a decreasing trend to an increasing trend.In the past 60 years,the average annual temperature in Qinghai Province was 1.03°C,showing a significant upward trend,and the temperature series had a sudden change in 1998.There is a time-lag correlation between annual precipitation in Qinghai Province and five atmospheric circulation factors,and a strong correlation with PDO(-),NAO(+),AMO(+),and a significant resonance period.The annual mean temperature in Qinghai Province was mainly correlated with PDO(-),NAO(-)and AO(+).(2)Considering the non-stationary model with climate factor as covariable,it can simulate the non-stationary dynamic changes of the descending water and temperature series in changing environment.Moreover,NSPEI has certain advantages in revealing the spatialtemporal variation trend of drought and can accurately identify drought conditions of different degrees,especially for severe drought events.Based on the NSPEI index,the drought frequency in Qinghai Province from 1961 to 2020 showed a decreasing trend,with moderate and mild drought mainly occurring.The drought station ratio was the largest in 1991 and the smallest in 1983.In the past 60 years,the major regional and regional droughts occurred in Qinghai Province,and there was no obvious drought.(3)The average duration of drought from 1961 to 2020 was consistent with the overall trend of drought intensity,which showed a decreasing trend at the rates of-0.0189/a and-0.0166/a,respectively.The average duration of drought in the whole region was 5.98 months,and the average intensity of drought was 6.74.The duration of drought decreased from northwest to northeast,and the spatial distribution of drought intensity was basically consistent with the duration of drought.The co-occurrence recurrence period of drought duration and drought intensity was larger than the joint recurrence period,and the NSPEI was larger and more concentrated than the estimated recurrence period of SPEI.In the middle drought condition,the average joint recurrence period was 2.79 years,and the average co-occurrence recurrence period was 7.52 years.Under the severe drought scenario,the average joint recurrence period was 4.11 years,and the average co-occurrence recurrence period was 16.22 years.The southwest of Qinghai Province is a high risk area of medium and severe drought,while the eastern agricultural area is a high risk area of medium and low risk.The risk of severe drought in the whole region is relatively small.The NSPEI index and PDF value of drought characteristics of non-stationary model are both greater than 0.52,and the prediction effect is better than that of drought characteristics.Among them,the arid areas of Qaidam Basin and the Yellow River basin in the headwaters of three rivers have the best prediction effect,which can be used to predict the change of meteorological drought in Qinghai Province in the future.