| 摘要: |
| 青海湖是青藏高原上最大的咸水湖，研究该区域冬季湖泊冻融时间的变化趋势及其与气候变化之间的关系，可以为预测未来气候对青海湖水情变化提供重要的见解。根据冰的亮度温度值高于水的亮度温度值这一差异，使用2001—2018年MODIS MOD02QKM数据产品和Landsat TM/ETM+遥感影像分别提取了青海湖开始冻结、完成冻结、开始消融和完成消融四个时间点的数据，综合分析青海湖湖冰物候特征变化，并结合气象数据，得出湖冰物候变化对气候的响应。结果表明：青海湖每年11月左右进入冰期，12月开始形成稳定的冰盖，次年3月或4月开始消融。湖冰覆盖时长和封冻期的变化趋势基本相同，整体上呈现出缩短的趋势，湖冰消融期整体上呈现出先缩短后增加的趋势；2001—2018年，平均首日冻结面积为8.15%，平均冻结速率为192.02 km2∙d−1，开始冻结和完成冻结的日期略有延迟，开始消融和完成消融的日期已经大大提前；冬季温度越高，青海湖湖冰封冻时间越短，日照时数越长湖冰覆盖时长越短，对于湖冰消融期来说，降水量越多湖冰消融速度越慢，平均风速越大湖冰消融速度越快。初步认为，气温是湖冰冻融的主要因素，预测未来1—2 a青海湖冬季气温仍会呈现上升趋势，湖冰封冻时长也会出现缩短趋势。 |
| 关键词: 湖冰物候 气候变化 MODIS 青海湖 |
| DOI：10.7515/JEE192036 |
| CSTR：32259.14.JEE192036 |
| 分类号: |
| 基金项目:青海省科技厅应用基础研究项目（2019-ZJ-7021） |
| 英文基金项目:Applied Basic Research Program of Science and Technology Department of Qinghai Province (2019-ZJ-7021) |
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| Characteristics and influencing factors of phenological changes of Qinghai Lake ice based on MODIS remote sensing images from 2001 to 2018 |
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LIU Qiuman, SHA Zhanjiang, WANG Qiugui, MA Yifan
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1. College of Geography, Qinghai Normal University, Xining 810008, China
2. Qinghai Province Key Laboratory of Physical Geography and Environmental Process, Qinghai Normal University, Xining 810008, China
3. MOE Key Laboratory of Tibetan Plateau Land Surface Processes and Ecological Conservation, Xining 810008, China
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| Abstract: |
| Background, aim, and scope Qinghai Lake is the largest saltwater lake on the Qinghai-Tibet Plateau. Studying the trend of the lake’s freezing and thawing time and its relationship with climate change in this region can provide important insights for predicting future climate changes in the Qinghai Lake water regime. Materials and methods In this study, based on the difference between the brightness temperature value of ice and the brightness temperature value of water, the MODIS MOD02QKM data product and Landsat TM / ETM+ remote sensing images from 2001 to 2018 were used to respectively extract Qinghai Lake’s starting to freeze, finishing to freeze, starting to melt and finishing to melt, comprehensively analyze the changes in the ice phenology characteristics of Qinghai Lake, and combine the meteorological data to get the response of the lake ice phenology changes to the climate. Results Qinghai Lake enters the glacial period around November every year, and a stable ice sheet begins to form in December, and begins to melt in March or April in the following year. The changes in the length of the lake ice cover and the freezing period are basically the same, showing a trend of shortening as a whole, and the lake ice ablation period is showing a trend of first shortening and then increasing; from 2001 to 2018, the average first-day frozen area was 8.15%, the average freezing rate is 192.02 km2·d−1. The dates for starting freezing and completing freezing are slightly delayed. Discussion According to the correlation between the differences in the freezing and thawing time of Qinghai Lake and the climatic factors such as temperature, precipitation, average wind speed, and sunshine hours in the past 18 years, the main reason for the inference of the freezing and thawing of Qinghai Lake is calculated and drawn to reflect intuitively. Conclusions Air temperature is the main factor of lake freezing and thawing. The higher the temperature is in winter, the shorter the ice freezing time of Qinghai Lake and the longer the sunshine hours are. The slower the ablation rate is, the greater the average wind speed is and the faster the lake ice melts. Recommendations and perspectives It is preliminarily believed that in the next 1 to 2 years, the temperature of Qinghai Lake in winter will still show an upward trend, and the length of the frozen ice will also appear to shorten. |
| Key words: lake ice phenology climate change MODIS Qinghai Lake |
