| 摘要: |
| 基于黄土高原111个气象站点1961—2018年逐日气温（最低气温、最高气温、平均气温）和降水数据，采用Mann-Kendall趋势分析、Sen’s斜率估计和小波周期等方法分析了气温和降水的时空变化特征，并采用小波交叉功率谱分析方法对影响区域气候的环流因素进行了分析。研究结果显示：（1）黄土高原1961—2018年平均气温以0.35℃·(10a) −1速率呈显著增加趋势，进一步分析显示气温的上升主要来自于年均最低气温的显著上升（0.39℃·(10a) −1，P＜0.01）；在季节变化上，平均气温、平均最低气温、平均最高气温在冬季的上升速率最为显著；研究区降水的年际、季节上的变化均不明显。（2）年均气温的突变在1995年，年均最高气温和年均最低气温分别在1995年和1994年存在突变；年降水量不存在突变。年降水量变化的主周期2—3 a和4—6 a，气温变化的周期主要为2—4 a、6—8 a、12—16 a。（3）平均气温变化主要受北大西洋年代际涛动（AMO）影响、受北大西洋涛动指数（NAO）影响较小；年降水量主要受太平洋海温指数（Nino3.4）和北极涛动（AO）影响。 |
| 关键词: 气温 降水 时空差异 黄土高原 |
| DOI：10.7515/JEE212018 |
| CSTR：32259.14.JEE212018 |
| 分类号: |
| 基金项目:国家重点研发计划项目（2017YFC1502401）；国家自然科学基金项目（41901094） |
| 英文基金项目:National Key R&D Program of China (2017YFC1502401); National Natural Science Foundation of China (41901094) |
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| Analysis of climate change characteristics and circulation factors in the Loess Plateau |
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LIU Liyun, LU Ruijie, DING Zhiyong, WANG Leixin, LIU Xiaokang
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1. Key Laboratory of Environmental Change and Natural Disaster of Ministry of Education, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China
2. Engineering Center of Desertification and Blown-Sand Control of Ministry of Education, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China
3. Beijing No.161 High School, Beijing 100053, China
4. School of Geography and Tourism, Shaanxi Normal University, Xi’an 710119, China
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| Abstract: |
| Background, aim, and scope Climate change is an important global concern issue. According to the Third National Assessment Report on Climate Change, the average temperature of inland China increased by 0.9—1.5℃ from 1909 to 2011, thereby affecting the local natural ecosystems and even the human life seriously. Moreover, the warming rate of inland China is slightly higher than that of the global average in the same period. In addition, the climate change in recent decades has varied in different regions of China, which is attributed to various factors including vast territory, regional climate, climate driving force and other factors. As a transition zone connecting northwest China and North China Plain, the temperature of the Loess Plateau has risen by nearly 2℃ from 1961 to 2010, which is higher than the average warming range in China, indicating that this region is extremely sensitive to the climate change. In view of the lack of previous studies on the Loess Plateau climate change, we carried out the climate change research on the Loess Plateau in the past 60 years, and tried to discuss the main circulation factors affecting the climate change in this region. Materials and methods Based on the daily temperature (the minimum, the maximum and the average temperature) and precipitation data from 111 weather stations in the Loess Plateau during 1961—2018, the Mann-Kendall trend analysis, Sen’s slope estimation and wavelet period were applied to analyze the spatial and temporal characteristics of temperature and precipitation, and the circulation factors affecting regional climate are investigated by using wavelet cross power spectrum analysis method. Results The results show that the annual average temperature, average minimum temperature and average maximum temperature all increased significantly, especially in winter, while the annual average temperature increased slowly in summer. It shows the phenomenon of “warm in winter and hot in summer”, and the change of precipitation is non-significant. The change of the mean temperature was abrupt at the end of the 20th century, and then the warming rate of the average temperature slowed significantly in the early 21st century. The annual average maximum and minimum temperature also presented abrupt changes at the end of the 20th century. The average maximum temperature kept a high growth rate. Discussion In recent 60 years, the continuous and rapid warming of the Loess Plateau located in the northwest, which may be related to the effect of vegetation cover. Although the correlation between NDVI and temperature is not as obvious as that of precipitation, vegetation growth is affected by temperature and constitutes underlying surface reaction to climate. There is a significant negative correlation between latitude and precipitation, and a significant positive correlation between latitude and annual precipitation variability. That is, the higher the latitude, the less precipitation and the greater the precipitation variability. The correlation between AMO and annual mean temperature was 0.734 (P＜0.01). Although there is no linear relationship between mean temperature and NAO, the coherent wavelet analysis shows that AMO influences the temperature of the Loess Plateau through the modulation of East Asian monsoon climate, while NAO influences the temperature of the Loess Plateau in some periods. ENSO (El Niño-Southern Oscillation) events and Arctic Oscillation also have influence on precipitation in the Loess Plateau. Conclusions The research results show that: (1) The temperature of the Loess Plateau during 1961—2018 showed a significant increasing trend with the rate of 0.35℃·(10a) −1 (P＜0.01). In terms of seasonal variation, the rising of the average temperature, average minimum temperature, and average maximum temperature was most significantly in winter. The annual variation trend of precipitation in the study area is not obvious, only 1.81 mm·(10a) −1, and the seasonal variation is not obvious. (2) The mutation of the annual average temperature was appeared around 1955, and the annual average maximum temperature and the annual average minimum temperature were abrupt change in 1995 and 1994, respectively. However, the annual precipitation did not vary from year to year. The main periods for the annual precipitation change are 2—3 a and 4—6 a, and the temperature change cycles are mainly 2—4 a, 6—8 a, and 12—16 a. (3) AMO played a key role in the average temperature change, while the North Atlantic Oscillation Index (NAO) showed a limited influence on the average temperature change. Also, the annual precipitation is mainly affected by Nino3.4 and AO. Recommendations and perspectives Data used in this paper were obtained from China Meteorological Data Sharing Service Centre (http://data.cma.cn/). Daily mean temperature, mean maximum temperature, mean minimum temperature, and precipitation data collected from 126 meteorological stations in the Loess Plateau region during 1961—2018, as well as circulation data got from the NOAA were studied. More climate data, such as the extreme temperature, the wind speed and pressure, can be collected to make a further detailed discussion. |
| Key words: temperature precipitation spatial and temporal variation Loess Plateau |
