Evaluation and Analysis of Soil Temperature Data over Poyang Lake Basin, China
Evaluation and Analysis of Soil Temperature Data over Poyang Lake Basin, China
Zhan, Ming-jin;Xia, Lingjun;Zhan, Longfei;Wang, Yuanhao
2020-12-08 00:00:00
Hindawi Advances in Meteorology Volume 2020, Article ID 8839111, 11 pages https://doi.org/10.1155/2020/8839111 Research Article Evaluation and Analysis of Soil Temperature Data over Poyang Lake Basin, China 1,2,3 1 2 4 Ming-jin Zhan , Lingjun Xia , Longfei Zhan , and Yuanhao Wang Jiangxi Eco-Meteorological Centre, Nanchang 330046, China Jiangxi Climate Change Centre, Nanchang 330046, China Institute for Disaster Risk Management (IDRM), School of Geographical Science, Nanjing University of Information Science & Technology, Nanjing 210044, China Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China Correspondence should be addressed to Yuanhao Wang; wyh1983@mail.iap.ac.cn Received 10 March 2020; Revised 22 October 2020; Accepted 2 November 2020; Published 8 December 2020 Academic Editor: Antonio Donateo Copyright © 2020 Ming-jin Zhan et al. -is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Soil temperature reflects the impact of local factors, such as the vegetation, soil, and atmosphere of a region. -erefore, it is important to understand the regional variation of soil temperature. However, given the lack of observations with adequate spatial and/or temporal coverage, it is often difficult to use observational data to study the regional variation. Based on the observational data from Nanchang and Ganzhou stations and ERA-Interim/Land reanalysis data, this study analyzed the spatiotemporal distribution characteristics of soil temperature over Poyang Lake Basin. Four soil depths were examined, 0–7, 7–28, 28–100, and 100–289 cm, recorded as ST1, ST2, ST3, and ST4, respectively. -e results showed close correlations between observation data and reanalysis data at different depths. Reanalysis data could reproduce the main spatiotemporal distributions of soil temperature over the Poyang Lake Basin but generally underestimated their magnitudes. Temporally, there was a clear warming trend in the basin. Seasonally, the temperature increase was the most rapid in spring and the slowest in summer, except for ST4, which increased the fastest in spring and the slowest in winter. -e temperature increase was faster for ST1 than the other depths. -e warming trend was almost the same for ST2, ST3, and ST4. An abrupt change of annual soil temperature at all depths occurred in 1997, and annual soil temperatures at all depths were abnormally low in 1984. Spatially, annual soil temperature decreased with latitude, except for the summer ST1. Because of the high temperature and precipitation in summer, the ST1 values were higher around the lake and the river. -e climatic trend of soil temperature generally increased from south to north, which was opposite to the distribution of soil temperature. -ese findings provide a basis for understanding and assessing the variation of soil temperature in the Poyang Lake Basin. result in variation of terrain and hydrological conditions, 1. Introduction alteration of the distribution and growth rate of vegetation, Soil temperature, an important parameter to characterize the enhancement of soil organic carbon decomposition, and thermal properties of soil, plays a key role in the land surface increased CO2 emissions from the soil to the atmosphere processes [1]. It can also affect climate change by affecting [6–11]. -ese effects could have major consequences both the energy distribution, exchange, and water budget on the locally and globally. surface. Moreover, it gradually acts on the upper atmosphere Under the influence of global warming, the mean surface through its influence on the surface boundary layer [2–5]. temperature around the world increased by an average of ° ° -erefore, soil temperature plays an important role in the 0.85 C (0.65–1.06 C) from 1880 to 2012 [12]. Between 1961 interaction between land and air [1, 2]. Soil temperature also and 2011, the mean temperature of China increased by 1.1 C, plays an important role in climate change [3–5]. Changes in which is greater than the global and the Northern Hemi- soil temperature associated with climate warming could sphere values [13]. Driven by the air temperature, the soil 2 Advances in Meteorology temperature in China has also shown a warming trend. Since climate change. However, owing to the lack of sufficient the 1990s, based on the monthly soil temperature data of 532 observation stations, it was not realistic to use observation data to study regional soil temperature variation. -erefore, stations in China, the annual mean soil temperature has remarkably increased. Regionally, the soil temperatures in we first evaluated the reanalysis data based on the obser- northeastern China have increased most significantly, vation data. Subsequently, we used the reanalysis data to whereas, in the eastern part of southwestern China, soil study the temporal and spatial variation characteristics of temperature has tended to decrease [14]. In Lhasa (Tibet), soil temperature in the Poyang Lake Basin. -e findings of from 1961 to 2005, the annual mean soil temperatures at this study will provide a scientific basis for improved un- shallow layers (0–40 cm) showed increasing trends, with derstanding and assessment of the impact of climate change increase rates of (0.45–0.66 C)/10a, which was greater than on terrestrial ecosystems. the increase trend of air temperature in the same period [15]. In Alxa Left Banner (Inner Mongolia Autonomous region, 2. Data northwestern China), from 1961 to 2005, the increase rates ° ° 2.1. Study Area. -e Poyang Lake Basin (28 22′–29 45′N, of annual soil temperatures at 0–80 cm soil depths were 5 2 ° ° 115 47′–116 45′E, area of 1.62 ×10 km ) is located in the (0.28–0.46 C)/10a, which was lower than that of the air middle–lower reaches of the Yangtze River, within the temperature (0.46 C/10a). Seasonally, the responses of sphere of the East Asian monsoon, and has a typical summer, autumn, and winter air temperature to climate monsoon climate (Figure 1). From 1961 to 2018, the annual change are more substantial than soil temperatures, while temperature is 18.1 C and annual precipitation is approxi- the responses of soil temperatures to climate change are mately 1650 mm. -e region has four distinct seasons: spring more significant than air temperature in spring [16]. Based (March–May), summer (June–August), autumn (Septem- on the analysis of the long-term changes (1961–2018) in soil ber–November), and winter (December–February). It plays temperature at Nanchang (the middle–lower reaches of the an important ecological and hydrological role in the middle Yangtze River, southern China), Zhan (2019) found that the and lower Yangtze River Region [20]. annual variation of air temperature correlated very well with ° ° -e Nanchang (28 36′N, 115 55′E; elevation: 46.9 m) soil temperatures at 0–320 cm soil depth [11]. -e increase ° ° and Ganzhou (28 52′N, 115 ; elevation: 58.6 m) weather rates of soil temperature were reported as 0.074–0.186 C/ station were selected for this study because they had 10a, lower than those of annual air temperature, 0.255 C/ remained at the same location since 1960. Nanchang station 10a. is located in the northern part of the basin and Ganzhou is To date, many studies have investigated the variations located in the southern, thus Nanchang and Ganzhou could of soil temperatures at specific research stations, but reflect the overall climate characteristics of the basin. examinations of the spatiotemporal variations of soil Moreover, the time series data of soil temperatures (depths temperature remain largely comparative. However, given of 0, 20, 80, and 320 cm) recorded at the two stations are long the lack of observations with adequate spatial and/or term, and the data integrity is considered satisfactory (i.e., temporal coverage, it is difficult to use the observation the amount of missing data annually is <5%). data of stations to study the regional variation. Because of the continuity and adequate spatial and temporal cov- erage, reanalysis data plays an important role in soil 2.2. Observed Data. -e soil temperature date (0, 20, 80, and temperature regional study. Yang and Zhang (2017) 320 cm soil depth) from Nanchang and Ganzhou National evaluated four reanalysis datasets of soil temperature, the Weather stations span from 1961 to the present (black circles land surface reanalysis of the European Centre for Me- in Figure 1). Prior to further analysis, these data were tested dium-Range Weather Forecasts (ERA-Interim/Land), the for homogeneity. -e missing data, less than 1%, have little second modern-era retrospective analysis for research and or no effect on the research results. applications (MERRA-2), the National Centre for Envi- ronmental Prediction Climate Forecast System Reanalysis (NCEP-CFSR), and version 2 of the Global Land Data 2.3. ERA-Interim/Land Reanalysis Data. ERA-Interim/Land Assimilation System (GLDAS-2.0) [17]. -ey found that is a global land surface reanalysis dataset covering the period reanalysis data could reproduce the main spatial distri- 1979 to the present. It describes the evolution of soil bution of soil temperature in summer and winter, espe- moisture, soil temperature, and snowpack. ERA-Interim/ cially over the east of China but generally underestimated Land is the result of a single 32-year simulation with the their magnitudes. Moreover, four reanalysis products (the latest ECMWF (European Centre for Medium-Range ERA-Interim reanalysis, ERA-Interim/Land, MERRA- Weather Forecasts) land surface model driven by meteo- Land, and NOAA-CIRES 20CR) were used to analyze the rological forcing from the ERA-Interim atmospheric re- soil temperature variation over middle and high latitudes analysis and precipitation adjustments based on the monthly of East Asia [18]. In addition, the ERA-Interim land GPCP v2.1 (Global Precipitation Climatology Project) surface temperature dataset has also been used in mapping [21, 22]. -ere are four soil depths 0–7, 7–28, 28–100, and the permafrost distribution over the Tibetan Plateau [19]. 100–289 cm, written as ST1, ST2, ST3, and ST4, respectively. ° ° In this study, soil temperatures at different depths were -e horizontal resolution is about 1 × 1 and the time fre- examined in the Poyang Lake Basin, located in the sub- quency is monthly (grid in Figure 1), from January 1979 to tropical monsoon region of China, a region sensitive to December 2018. Advances in Meteorology 3 114° E 115° E 116° E 117° E 118° E 119° E 2.4.2. Sen’s Slope Estimator. Sen (1968) developed the nonparametric procedure for estimating the long-term trend [23]. Compared with the least squares linear regression, Yangtze 30° N Sen’s slope estimator is not sensitive to outliers and thus the river estimated linear trend is significantly more accurate and robust for skewed data. -e slope of N pairs of data points 29° N can be estimated by the following relation: Nanchang x − x j l β � median , (j> l> 1), (2) 28° N j − l where x and x are data values at time l and time j, re- l j 27° N spectively. -is method is widely applied to hydrological and climatic time series because of its robustness for estimating the magnitude of a trend [24–28]. 26° N Ganzhou 2.4.3. Test of Abrupt Change. -e Mann–Kendall test was 25° N developed by Mann and Kendall [29, 30] and was originally used to detect trend changes in the sequence. Goossens and 0 100 200 km Berger (1986) improved and further developed the test, 24° N allowing it to determine the year of the abrupt change in the trend [31]. Weather station For time series x with n sample sizes, a rank series S is Grid constructed: River 1 x > x ⎧ ⎨ i j Figure 1: Location of the Nanchang and Guangzhou National S � r , r � , j � 1, 2, . . . , i, (3) i i Weather stations, China. 0 else i�1 S − E S k k ������� 2.4. Method UF � , k � 1, 2, . . . , n. (4) Var S 2.4.1. Applicability Evaluation of ERA-Interim/Land Re- analysis Data. -e evaluation of the ERA-Interim/Land In equation (4), UF � 0 and E(S ) and Var(S ) are the k k reanalysis data using the observed data focused on mean and variance of the S : monthly variations. -e correlation coefficients, mean n(n + 1) error (ME), mean absolute error (MAE), and root mean E S � , square error (RMSE) between ERA soil temperature and (5) observational soil temperature were calculated to in- n(n − 1)(2n + 5) Var S � . vestigate their agreement at monthly time scales. -e two k observed time series are from Nanchang and Ganzhou stations. -eir counterparts, the ERA-Interim/Land re- Arrange x in reverse chronological order, x , x , . . . , x . Repeat the process again to obtain UB: analysis data, are the average values of the two grid cells n n−1 1 closest to the weather stations (red grid cells in UB � −UF , k � n, n − 1, . . . , 1. (6) k k Figure 1). STERA represented the soil temperature series of the ERA-Interim/Land reanalysis data, while STobs UF is a standard normal distribution, which is in the represented the soil temperature series of the observa- time series x order x , x , . . . , x . Look up the normal 1 2 n tional data: distribution table at the given significance level α. If |UF |> U , it indicates that there is an obvious trend change i α in the sequence. If α � 0.05, U � ± 1.96. 0.05 ME � ST − ST /n , ERA obs. If the UF and UB intersect and |UF |> 1.96, x would i�1 change abruptly at the intersection. -e Mann–Kendall test has been frequently used to quantify the abrupt changes in MAE � ST − ST /n, ERA obs. hydrometeorological time series [32, 33]. . (1) i�1 ���� 2.4.4. Anomaly and Standard Deviation. Climate anomalies RMSE �