Climate Change Research Letters
Vol. 08  No. 06 ( 2019 ), Article ID: 33172 , 10 pages
10.12677/CCRL.2019.86093

Soil Moisture in the Tibetan Plateau and Its Relationship with Summer Precipitation in Eastern China

Xin Liu

School of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu Sichuan

Received: Nov. 5th, 2019; accepted: Nov. 20th, 2019; published: Nov. 27th, 2019

ABSTRACT

In this paper, using the soil moisture data in the GLDAS dataset, the temporal and spatial distribution characteristics of soil moisture in the Qinghai-Tibet Plateau were analyzed by empirical orthogonal function (EOF) and related methods, and the soil moisture in the spring of the plateau and the summer precipitation in eastern China were further studied. The results show that the soil moisture in the different seasons of the Qinghai-Tibet Plateau is consistent in spatial distribution from 1981 to 2016, showing a decreasing distribution from the southeast to the northwest, and the soil moisture will increase with the depth of the soil. The soil moisture at all levels in the Qinghai-Tibet Plateau has a good correlation with the summer precipitation in eastern China. The specific performance is that the soil moisture in the spring plateau is negatively correlated with the summer precipitation in eastern China. From the typical area through the reliability test, the spring soil moisture in the plateau is negatively correlated with the precipitation in the southeast coastal areas in summer, and negatively correlated with the precipitation in the middle and lower reaches of the Yangtze River in June and July, and precipitation in the northeastern region in July and August. It was negatively correlated; it was also positively correlated with precipitation in the middle and lower reaches of the Yangtze River in August, and positively correlated with precipitation in Northeast China in June.

Keywords:Tibetan Plateau, Soil Moisture, Correlation, Eastern Of China, Summer Precipitation

Copyright © 2019 by author(s) and Hans Publishers Inc.

1. 引言

2. 方法

2.1. 数据介绍

2.2. 研究方法介绍

2.2.1. EOF分解

EOF称为经验正交函数(Empirical Orthogonal Function)。EOF分解法是根据气象资料场的主要特征值进行分解，分解的函数因此没有固定的函数形式但同时保有“正交性”的特点，与此同时取点也不受限制。

${M}_{i×j}={T}_{i×j}{X}_{i×j}$ (1)

2.2.2. 趋势系数及显著性检验

${r}_{xt}=\frac{{\sum }_{i=1}^{n}\left({x}_{i}-\stackrel{¯}{x}\right)\left(i-\stackrel{¯}{t}\right)}{\sqrt{{\sum }_{i=1}^{n}{\left({x}_{i}-\stackrel{¯}{x}\right)}^{2}{\sum }_{i=1}^{n}{\left(i-\stackrel{¯}{t}\right)}^{2}}}$ (2)

$rc=\frac{{r}_{xt}\sqrt{n-2}}{\sqrt{1-{r}_{xt}^{2}}}$ (3)

2.2.3. 趋势系数及显著性检验

$r=\frac{1}{n-1}\underset{i=1}{\overset{n}{\sum }}\left(\frac{{X}_{i}-\stackrel{¯}{X}}{\sigma X}\right)\left(\frac{{Y}_{i}-\stackrel{¯}{Y}}{\sigma Y}\right)$ (4)

3. 基于GLDAS的青藏高原土壤湿度的时空变化特征

3.1. 土壤湿度的空间分布特征

Figure 1. 1981-2016 Qinghai-Tibet Plateau 0 - 10 cm (Fig. a), 10 - 50 cm (Fig. b), 50 - 100 cm (Fig. c), annual average, spring, autumn, winter, summer spatial distribution of soil moisture (unit: m3m−3)

3.2. 土壤湿度的空间变化趋势

Figure 2. The first mode (EOF1) space type (left) of the soil moisture anomaly EOF developed in the 0 - 10 cm (top), 10 - 50 cm (middle), and 50 - 100 cm (lower) years of the Qinghai-Tibet Plateau from 1981 to 2016 Time factor (right)

Table 1. Statistical table of variance contributions of EOF characteristic vectors of soil moisture anomaly fields at different levels in the Qinghai-Tibet Plateau from 1981 to 2016 (Unit: %)

Figure 3. The first mode (EOF1) space type (left) of the soil moisture anomaly EOF developed in the 0 - 10 cm (top), 10 - 50 cm (middle), and 50 - 100 cm (lower) years of the Qinghai-Tibet Plateau from 1981 to 2016 Time factor (right)

4. 青藏高原土壤湿度与中国东部降水的联系

Figure 4. The variation curve of spring soil moisture anomaly index (I_M) in the Qinghai-Tibet Plateau from 1981 to 2013 and the standard sequence of precipitation in June in eastern China. In the figure, the change of the soil moisture anomaly index in the lower layer (0 - 10 cm) of the plateau is indicated by the red line, and the dotted line of the black dot indicates the middle layer (10 - 50 cm), the blue dotted line indicates the deep layer (50 - 100 cm). The precipitation sequence is represented by a column

Figure 5. From 1981 to 2013, the variation index of soil moisture anomaly index in the Qinghai-Tibet Plateau (I_M) shows the change of soil moisture anomaly index in the lower layer (0 - 10 cm) of the plateau by red line, the dotted line of black dot indicates the middle layer (10 - 50 cm), and the blue dotted line indicates Deep layer (50 - 100 cm)

Figure 6. The variation curve of soil moisture anomaly index (I_M) in the Qinghai-Tibet Plateau from 1981 to 2013 and the normalized sequence of precipitation in July and August in eastern China. In the figure, the change of soil moisture anomaly index in the lower layer (0 - 10 cm) of the plateau is indicated by the red line, and the dotted line of black dots indicates Middle layer (10 - 50 cm), blue dotted line indicates deep layer (50 - 100 cm). Precipitation sequence is represented by column

Figure 7. The correlation between the soil moisture anomaly index of the Qinghai-Tibet Plateau and the precipitation in July and August in eastern China (the area indicated by the 90% confidence level in the dot) is a shallow (0 - 10 cm) soil moisture anomaly index and precipitation in July and August. Correlation map, Figure b is the correlation map between the soil moisture anomaly index of the middle layer (10 - 50 cm) and the precipitation in July and August, and the correlation distribution of the soil moisture anomaly index in the deep layer (50 - 100 cm) and the precipitation in July and August

5. 结论

1) 1981~2016年青藏高原各层次、各季节的土壤湿度在空间分布特征上呈现一致性。土壤湿度从高原东南部至高原西北部逐渐递减，并且高原整体土壤湿度随着土壤深度的加深而逐渐变大。

2) 将青藏高原土壤湿度的距平场进行EOF分解，青藏高原各层次、各季节的第一模态在空间分布以及时间系数变化近乎相似。在第一模态中高原的西北部往往表现为正异常，而高原的东南部往往表现为负异常，即高原东南地区和西北地区的土壤湿度呈反相变化。结合时间系数分析，在1981~2001以前青藏高原东南部土壤较湿，西北部较干；而2001年~2016年，东南部减少，西北增加。

3) 青藏高原春季各层次土壤湿度与中国东部的降水呈负相关，即土壤湿度值越大，东部降水量越少。从通过90%显著性检验的典型区域来看，高原春季土壤湿度与6，7，8月(夏季)东南沿海地区降水呈明显的负相关。6、7月长江中下游地区的降水量与青藏高原春季各层次土壤湿度呈负相关；8月长江中下游地区的降水量与青藏高原春季土壤湿度呈正相关。东北和华北地区六月的降水量与青藏高原春季各层次土壤湿度呈正相关；到了七、八月与高原春季土壤湿度呈负相关。在六月，高原土壤湿度与淮河流域的降水量呈负相关；到了七、八月，淮河流域的降水量与青藏高原春季各层次土壤湿度呈正相关。

Soil Moisture in the Tibetan Plateau and Its Relationship with Summer Precipitation in Eastern China[J]. 气候变化研究快报, 2019, 08(06): 845-854. https://doi.org/10.12677/CCRL.2019.86093

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