Study On Typical Drought Events Reconstruction Based On Rainfall And Snow Archives

Extreme droughts refer to the drought disaster events characterized with large spatial extent,long term duration,and severe impacts.In Chinese history,there had been several typical extreme drought events,such as the extreme drought occurred in the last period of Emperor Chongzhen of the Ming dynasty and early years of Emperor Guangxu of the Qing Dynasty.Extreme droughts usually result in serious crop yield reduction in large-area,severe economic losses and social conflicts.In recent years,due to the influence of global climate change,the occurrence of large-scale extreme drought events that latest for several seasons and multiple years will increase.However,the occurrence of extreme drought events with large-scale and long-duration have not been involved in the existing drought relicense and relief laws and regulations,plans,standards and policies and drought resistance in China.Under the current social-economic development situation,the emergence of an extreme drought event that similar to the historical extreme drought,may have a more catastrophic impacts on food security,drinking water and ecological security than that in history period.Therefore,it is of great significance to reconstruct the historical typical extreme drought event and explore its spatial-temporal evolutions.This will largely benefit us to cope with the present or future drought disasters by making disaster prevention and preparedness strategies and policies in advance.In order to explore and make full use of the rainfall and snow archives from the Qing dynasty,the improved Green-Ampt method(hereinafter referred to as "the improved Green-Ampt infiltration model")and the large-scale distribution Land-based hydrological model VIC(hereinafter referred to as"VIC model")was introduced in this study.The precipitation reconstruction method of historical typical drought events which is based on rainfall and snow archives combining with the runoff and soil water reconstruction methods of historical typical drought events based on VIC model were employed.Taking the extreme drought in Shanxi province in the early years of Emperor Guangxu of the Qing Dynasty(1875-1879)as a case study,the precipitation,runoff and soil water sequences of this typical drought event were reconstructed.The panoramc view of this typical extreme drought in Shanxi province was restored from the perspectives of meteorological drought,hydrological drought and soil water drought.The main conclusions of the paper are as follows:(1)The reconstruction method of historical typical drought events based on the Rainfall and Snow Archives has been put forward.Based on the high-resolution and high-precision rainfall and snow archives from Qing dynasty,measured soil moisture,meteorology,hydrology data in the past decades,Soil parameters and vegetation cover data,we analyzed the feasibility of the historical typical drought events reconstruction.The principle of the improved Green-Ampt infiltration model was introduced in company with the precipitation reconstruction method of historical typical drought events were carry out to analyze the model applicability.The large-scale land surface hydrological model VIC is employed to construct a land surface hydrological simulation framework.Taking the reconstructed precipitation sequence as input,this study discussed the reconstruction method of runoff and soil water of historical typical drought events based on the VIC model.Based on the reconstruction of precipitation,runoff and soil water sequences,the precipitation anomaly percentage,runoff anomaly percentage and soil water percentile were used to reconstruct the typical historical drought events.Taking the extreme drought in Shanxi in early years of Emperor Guangxu of the Qing Dynasty as a case study,the spatial-temporal evolution of meteorological drought,hydrological drought and soil water drought in Shanxi province during a typical drought in history was analyzed comprehensively.(2)The precipitation sequence from 1875 to 1879 in Shanxi province in the early years of Emperor Guangxu of the Qing Dynasty has been reconstructed quantitatively.The spatial and temporal evolution of meteorological drought in Shanxi Province has been analyzed.The results showed that severe drought occurred in Shanxi Province from 1875 to 1879 for five consecutive years.Among them,extremely drought occurred from 1875 to 1877 with a provincial coverage.The annual rainfall anomalies from 1875-1877 were-65%,-64%and-70%respectively.The drought was lighter in 1878,and the northern region was more severe than the southern region in Shanxi.Compared with 1878,the drought in occurred in 1879 was more sever.The central and northern regions were more severe than the southern region.From 1875 to 1879,there was severe seasonal drought,of which 1875 drought duration was from summer to winter,while drought occurred in summer and autumn from 1876 to 1877.(3)The runoff sequence of Shanxi province from 1875 to 1879 in the early years of Emperor Guangxu of the Qing Dynasty based on the VIC model has been reconstructed quantitatively.The spatial and temporal evolution of hydrological drought in Shanxi province has been analyzed.The results showed that there were large-scale,continuous severe drought and extreme hydrology drought for five consecutive years from 1875 to 1879.The annual average annual runoff depth was 11.38,11.58,9.88,29.79 and 19.10mm,and the runoff anomaly percentages were-84%,respectively.-85%,-87%,-61%,-74%.Severe hydrology drought occurred from 1875 to 1877 with a 95%drought area coverage of the province.Among them,the most severe drought occurred in 1877.The province of Shanxi has reached a severe drought level,and the drought severity decreased from 1878 to 1879.During the five consecutive years of drought,the runoff in Shanxi has generally decreased by 80%.The runoff depth in all areas within the territory does not exceed 30mm,especially in the northern region,where the hydrological drought is severe and the runoff depth is below 10mm.(4)The soil water sequence of Shanxi Province from 1875 to 1879 in the early years of Emperor Guangxu of the Qing Dynasty based on the VIC model has been quantitatively reconstructed.The spatial-temporal evolution of soil water drought in Shanxi Province has been analyzed.In general,most parts of Shanxi Province from 1875 to 1879 showed obvious soil water drought in each month,of which the droughts in 1875,1876 and 1877 were particularly severe,especially in the winter and spring of 1877.Severe droughts occurred with an area coverage more than 90%of the regions.Extreme drought were occurred in the southern regions.Compared with 1877,the severity of drought was relatively mild from 1878 to 1879,and the drought coverage was correspondingly reduced.This paper studies the reconstruction method of the historical typical drought events based on the rainfall and snow archives,which has a great significance for the current understanding of the historical typical extreme drought events,and provides strong support for coping with the present or future drought risk,so enabling formulate the disaster prevention strategy and policy in advance.