太湖梅梁湾浊度对风值的时滞性响应研究

Time-lag responses of turbidity to wind values in Meiliang Bay,Taihu Lake

基于野外高频同步观测数据,采用风值来定量表征风向风速变化,并利用广义相加模型(GAM)揭示太湖表层和底层浊度对单独风速、综合风值的滞后效应.结果表明:小风状态下(风速<4m/s或风值<3),太湖梅梁湾的浊度较低,随着风速增加,浊度呈持续性增长;随着风值增加,前期浊度呈增长趋势后期逐渐呈平缓趋势;风向的短期变化对浊度的影响较小,单向风的长时间累积对浊度影响较大;表层浊度对单独风速的滞后响应时间是5h45min、对风值的滞后响应时间是1h;而底层浊度对风速和风值的滞后时间分别为7h和2h;说明浊度对风速和风向均存在一定的延迟效应,随着水深的增加,由于地形等其他因素的影响,湖流存在一定垂向切变,风向对浊度变化的影响逐渐减小.该研究结论揭示仅仅研究风速对浅水湖泊的生态系统的影响存在一定不足,风向的影响不容忽视.同时考虑风向和滞后效应的双重作用对富营养化模型精度的提高有着重要影响.

The wind values from the field high-frequency simultaneous observations were used to quantitatively characterize the wind direction and wind speed variations,and the generalized summation model(GAM)was used to evaluate the hysteresis effects of individual wind speeds and integrated wind values on surface and bottom turbidity of the Taihu Lake.The results show that:(1)the turbidity in the area of Meiliang Bay in the Taihu Lake was low under light wind conditions(wind speed<4m/s or wind value<3),and increased continuously with wind speed.With an increase in wind value,the turbidity showed an increasing trend in the early stage and a flat trend in the later stage;(2)the short-term change in wind direction had a small effect on the turbidity,while the long-term accumulation of one-way wind had a large effect;(3)the lag time of surface turbidity was 5h 45min to wind speed alone,and 1h to wind value,and the lag time of bottom turbidity to wind speed and wind value was 7h and 2h,respectively.Obviously,there was a specific time-lagged responses of turbidity to both wind speed and wind direction,becoming obvious with water depth.Due to the influence of other factors(e.g.,topography,etc.),the lake flow had a certain vertical shear,and the influence of wind direction on turbidity variation gradually became weak.Obviously,the dual effects of wind direction and the hysteresis effect determine the accuracy of the eutrophication model,and the studies on wind speed's effects on shallow lakes'ecosystems need to be further enhanced with no ignorance of the effects of wind direction.