Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5749971 | Science of The Total Environment | 2017 | 12 Pages |
â¢SMMR & SSM/I data are capable of extracting lake ice freeze-thaw dates of Qinghai Lake.â¢The freezing dates have been delayed and the ablation dates have advanced.â¢Ice coverage duration of Qinghai Lake has shortened by 21.21 days from 1979 to 2016.â¢Ice coverage duration is significantly negatively correlated with air temperature in winter.
Lake ice is a sensitive indicator of climate change. Based on the disparities between the brightness temperatures of lake ice and water, passive microwave data can be used to monitor the ice variations of a lake. With focus on the analysis of long time series variability of lake ice, this study extracts four characteristic dates related to lake ice (the annual freeze start, freeze completion, ablation start and ablation completion dates) for Qinghai Lake from 1979 to 2016 using Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave Imager (SSM/I) passive microwave brightness temperature data. The corresponding freezing duration, ablation duration, complete freezing duration and ice coverage duration are calculated. Applying Moderate Resolution Imaging Spectroradiometer (MODIS) daily snow products, the accuracy of the results derived from passive microwave data is validated. The validation analysis shows a strong agreement (R2 ranges from 0.70 to 0.85, mean absolute error (MAE) ranges from 2.25 to 3.94Â days) in the freeze start, ablation start, and ablation completion dates derived from the MODIS data and passive microwave data; the ice coverage duration also has a small error (relative error (RE)Â =Â 2.95%, MAEÂ =Â 3.13Â days), suggesting that the results obtained from passive microwave data are reliable. The results show that the freezing dates of Qinghai Lake have been delayed and the ablation dates have advanced. Over 38Â years, the freeze start date and freeze completion date have been pushed back by 6.16Â days and 2.27Â days, respectively, while the ablation start date and ablation completion date have advanced by 11.24Â days and 14.09Â days, respectively. The freezing duration and ablation duration have shortened by 3.89Â days and 2.85Â days, respectively, and the complete freezing duration and ice coverage duration have shortened by 14.84Â days and 21.21Â days, respectively. There is a significant negative correlation between the ice coverage duration and the mean air temperature in winter.
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