Research On Drought Mechanism And Driving Factors Of The Luanhe River Basin

Along with the global climate change and social economic development,the problem of water resource shortage of Luanhe River basin was increasingly prominent and the frequency of drought disasters in drainage basin were obviously increases.The severe drought restricted the social and economic development and had a strong impact on the local people's normal life.This paper elaborates from two perspectives of meteorology and hydrological drought.On one hand,The meteorological drought driving factors in the Panjiakou Reservoir Catchment of the Luanhe River basin were identified in the paper,which was significant for the study of the evolution mechanism of meteorological drought;on the other hand,it constructs multi factor linear regression model,analyzing the correlation between the different land-use types and the runoff of drainage basins.The main research contents and results are as bellow:(1)Identification the large-scale driving factors of the drought.The time series of the precipitation anomaly percentage(Pa)was calculated based on the rainfall data of the Panjiakou Reservoir Catchment of the Luanhe River basin.Then the time series of large-scale climate factors were acquired and the main climate factors affecting basin precipitation were identified through the partial correlation analysis.The large scale climate data was downloaded from American Environmental Centre Website(NCEP/NCAR).It can be seen that the precipitation of the Luanhe River basin was mainly influenced by the large-scale climate factors including AO,WP,NINO 3.4 and EP-NP.What's more,AO is correlated significantly with precipitation change process at same period and the sea surface temperature anomaly(SSTA)of Pacific Ocean impacted the 12-month time lag precipitation of the Luanhe River basin.(2)Analysis of the drought driving factors and evolution of typical drought year.The severe droughts happened in Luanhe River basin were identified based on the precipitation anomaly percent(Pa)and drought grade division standard from 1965 to 2012.The drought driving mechanism was analyzed based on the reanalysis data from NCEP/NCAR.The 500 hPa geopotential height anomaly over the mid-latitude and Pacific Ocean are significantly related to the large-scale circulation.The relationship between AO/SSTA and precipitation were discussed in the paper.The result showed that the drought period of typical droughts were corresponding to negative phase of AO.The negative phase of AO caused the positive geopotential height anomaly center over the downstream of the Ural Mountains,the north of the Mongolian plateau and the Sea of Okhotsk,which caused the geopotential height over the mid and high latitude was much higher than that in the Luanhe River basin.The cold air from higher latitude to East Asia Continent was stronger than normal and the Luanhe River basin was mainly controlled by the cold air.The lower sea-surface temperature over the WP?EP-NP and NINO 3.4 area might weakened the Western Pacific Subtropical high in the next year through the complex air to sea interaction.(3)Based on the runoff and different phase of land-use types data,multiple linear regression models was constructed and identified the main driving factors of hydrological droughts happened in each sub-basin.The results showed that the hydrological droughts were mainly influenced by the meteorological drought.The runoff was affected by the different land-use types through the water circulation anomaly.When the cultivated land converted to the forest and grassland,the soil roughness was increased,which result in the increase of the capacity of soil infiltration.The decrease of the water area enhanced the capacity of soil infiltration,which leaded to the decrease of the runoff.