黄土高原PM_(2.5)质量浓度与微雨事件的权衡−协同关系演化

Trade-offs and synergistic evolution between PM_(2.5)concentration shrinkage and light rain events in the Loess Plateau

基于权衡−协同关系视角,从长时间序列和多层次空间尺度探讨1998—2017年黄土高原PM_(2.5)质量浓度与微雨事件的作用关系、时空演化及地域分异。结果表明:①黄土高原PM_(2.5)质量浓度和微雨事件均表现出以5 a或4 a为周期的“三峰三谷”波动小幅上升趋势。②PM_(2.5)质量浓度和微雨事件间的作用关系呈现出“过程上的协同性+增量上的权衡性”特征;从过程演化来看,协同关系是研究期内黄土高原PM_(2.5)质量浓度和微雨事件的主导关系,但从基于倾斜率的增量变化上看,二者以异向的权衡关系为主导,表明微雨事件的强化在黄土高原未来的雾霾治理中具有重要意义。③不同微雨事件指标与PM_(2.5)质量浓度的空间关系和演化趋势存在差异;冬春季节微雨事件,尤其是冬春微雨天数与PM_(2.5)质量浓度的作用关系明显强于年尺度。④PM_(2.5)质量浓度和微雨事件权衡−协同关系及演化在不同治理分区差异显著,城镇化和工业化水平较高的河谷平原区和土石山区是二者关系敏感区。

Based on the trade-offs and synergistic relationship perspective,the relationships,spatial and temporal evolution,and geographic variations of PM_(2.5)concentration and light rain events in the Loess Plateau were investigated from a long time series and a multi-level spatial scale from 1998 to 2017.The results show that:1)The PM_(2.5)concentration and light rain events in the Loess Plateau show a slight upward trend in the fluctuation of‘three peaks and three valleys’with a circle of 5 or 4 years;2)The relationship between PM_(2.5)concentration and light rain events is characterised by“process synergy+incremental trade-off”.In terms of process evolution,synergy is the dominant relationship between PM_(2.5)concentration and light rain events in the Loess Plateau during the study period,but in terms of incremental changes based on tilt rate,the two are dominated by an anisotropic trade-off,indicating that the light rain events have been increasing in anisotropic direction.Trade-off relationship is dominant,suggesting that the enhancement of light rain events is important in the future haze management in the Loess Plateau;3)The spatial relationships and evolutionary trends of different indicators of light rain events and PM_(2.5)concentration are significantly different;the role of light rain events in winter and spring seasons,especially the number of light rain days in winter and spring,in relation to PM_(2.5)concentration is significantly stronger than that on an annual scale;4)The trade-offs and synergistic relationship between PM_(2.5)concentration and light rain events and their evolutionary characteristics show significant spatial and temporal heterogeneity in different management zones,and the river valley plains and the soil and rocky mountainous areas with higher levels of urbanisation and industrialisation are the areas with the most significant changes in the trade-off-synergistic relationship between PM_(2.5)concentration and light rain events in the Loess Plateau,and are the sensitive areas for the relationship between the two.