Gaoyuan qixiang (Aug 2023)
The Multi-Time Scale Characteristics and Impacts on Ecological Vegetation of Warming and Humidification in the Upper Yellow River
Abstract
The upper Yellow River are located at the intersection of the Qinghai-Xizang Plateau， the Loess Plateau， and the Mongolian Plateau， it is sensitive to climate change and the ecological environment is fragile， it is the main flow-producing area and water conservation area in the Yellow River Basin， the ecological location is very important for the water resources and ecological security of the Yellow River Basin.The upper Yellow River have shown significant warming and humidification characteristics since the beginning of this century， but they are unclear that the multi-time scale characteristics， causes and effects on ecological vegetation of warming and humidification.So， based on various data such as observation， reanalysis， satellite remote sensing and future scenario prediction， using EOF， EEMD and other statistical methods， this paper systematically analyzed the warming and dry-wet characteristics of the upper Yellow River for more than half a century， and discussed the causes of current warming and humidification and its impact on ecological vegetation.It is found that the upper reaches of the Yellow River average temperature have increased at a rate of 0.37 °C·（10a）-1 since 1961， which is more obvious than that of the whole world， the whole country and even the whole northwest.Precipitation shows obvious interdecadal changes， which has increased significantly at a rate of 32 mm·（10a）-1 since 1997.Therefore， the upper reaches of the Yellow River have shown an obvious warming-wetting trend since 1997.From the perspective of spatial anomaly distribution characteristics， temperature and precipitation are mainly dominated by regional consistent modal changes.From the point of view of multi-time scale changes， the average temperature is mainly dominated by long-term trend changes， followed by inter-annual changes， and precipitation is mainly dominated by inter-annual changes， followed by multi-decadal changes.The reason for the continuous warming since 1961 is mainly the result of an increase of the average temperature trend component.The obvious humidification trend since 1997 is mainly due to the humidifying channel at the multi-decadal weight of precipitation over 30 years.From the perspective of spatial dynamic changes， the upper reaches of the Yellow River in each climatic period from 1961 to 2010 showed overall warming and drying， but the drying trend slowed down by climatic period， and the region showed consistent warming and drying from 1991 to 2020.The variation of precipitation in the upper reaches of the Yellow River is mainly affected by the westerly， East Asian summer monsoon and South Asian summer monsoon.However， the circulation factors affected are quite different at multi time scales.The interannual scale is mainly affected by the single circulation factor of the South Asian summer monsoon， the interdecadal scale is mainly affected by the westerly and South Asian summer monsoon， and the multi-decadal scale is mainly affected by the westerly and South Asian summer monsoon circulation.The wetting trend since 1997 is mainly the result of the enhancement of the westerly and South Asian summer monsoon circulation.It is expected that the upper reaches of the Yellow River will continue to show a warming and wetting trend in the next 80 years， and the warming trend is basically the same as that at present， while the wetting trend is significantly weaker than that at present.Water and heat conditions is insufficient in the upper reaches of the Yellow River， and ecological vegetation has a certain dependence on the average temperature and precipitation in the past three months， and the stronger dependence on precipitation in the same period.In addition， the average temperature has a longer lag effect on ecological vegetation than precipitation， Average temperature and precipitation have a synergistic effect on ecological vegetation.A warm and wet climate is the most conducive to vegetation growth， while a cold and dry climate is not.The warming and wetting climate makes the ecological vegetation in the upper reaches of the Yellow River tend to be good in the recent 20 years， and warming and wetting trend may make ecological vegetation continue to improve in the next years.
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