Climate change inevitably leads to changes in hydrothermal circulation. However, thermal-hydrologic exchanging caused by land cover change has also undergone ineligible changes. Therefore, studying the comprehensive effects of climate and land cover changes on land surface water and heat exchanges enables us to well understand the formation mechanism of regional climate and predict climate change with fewer uncertainties. This study investigated the land surface thermal-hydrologic exchange across southern China for the next 40 years using a land surface model (ecosystem-atmosphere simulation scheme (EASS)). Our findings are summarized as follows. (i) Spatiotemporal variation patterns of sensible heat flux (
Global climate change characterized by global warming has put significant impacts on natural ecosystems and human society [
Climate warming intensifies hydrothermal circulation as well and causes temporal-spatial variations of water and heat resources. It will further increase the frequency of hydrological extreme events and change the regional water and heat balances. In turn, water circulation and heat transport are important processes of each circle in the entire climate system. They directly affect the local climate, environments, and ecosystems and therefore play very important roles in climatic change and abnormity. Only detailed studies on their individual physical characteristics are carried out, can we recognize the formation mechanism of regional climates. Sensible heat flux (
Climatic change is a direct driving force of land surface thermal-hydrologic cycle. Many studies have assessed the impacts of climate change on energy transferring during historical periods [
The majority of the previous related researches for history periods and future projections focused on the impact of water and heat exchange resulted from either climate change [
On the underlying surface characterized by diverse composition, complex nature, and heterogeneous distribution like Southern China, the land-atmosphere interactions, as the key physical processes affecting climate anomalies, are even more comprehensive. Moreover, Southern China had experienced land cover change process of deforestation-reforestation-reforestation in the past 30 years. With such a complex change process, only the analysis of land-atmosphere interaction processes from the mechanism level can improve our capability of modeling and predicting the future climate change in the Asian monsoon region.
In this study, the future spatiotemporal changes of
The paper is organized as follows. The subsequent section describes the study area and methodology. Section
The study area, with various geomorphic types, is located between 104.42°E, 21.12°N and 120.59°E, 31.25°N, which covers the majority of Southern China, covering most parts of the Yangtze River and Pearl River (Figure
The location and land cover map in the year 2005 in Southern China.
An integrated land surface model, named ecosystem atmosphere simulation scheme (EASS), [
EASS can be run pixel by pixel over a defined domain, so it can be adopted at different scales based on available input data. Besides, EASS has flexible spatial and temporal resolutions, as long as the input data of each pixel is defined.
The typical characteristics of the model are briefly described as follows. (i) Energy, water, and carbon are simulated simultaneously based on explicit link among photosynthesis, evapotranspiration, and stomatal conductance. (ii) Vegetation cover is treated as a single layer and the model stratified the vegetation canopy as sunlit and shaded leaves according to the solar zenith angle and a foliage clumping index (
For future land cover scenarios, land cover classification system mainly includes cultivated land, woodland, grass land, build-up land, water area, wetland, nival area, desert, bare rock, and desertification land. This is a relative rough classification, making it impossible to correspond to the International Geosphere-Biosphere Program (IGBP) classification acquired in EASS model. Therefore, the model needs to be improved and parameter optimization is required to match the existing land cover classification system for the future scenarios. Given that only one flux observation tower (QYZ) locates in this study area, we used the measured data from FLUXNET to optimize EASS model parameters over various plant function types and carried out model validation and evaluation.
The model driving meteorological data, including incoming shortwave radiation, air temperature, relative humidity, precipitation, and wind speed, were obtained from GCM-HadCM3, Hadley Centre for Climate Prediction and Research.
The critical parameters were optimized in the model to improve the model’s capacity and applicability to varied land surface conditions. Employing the available global EC flux observation network data, the EASS model has been further validated and parameterized among a number of flux towers worldwide covering various plant functional types. The coefficient of determination (
This study used five-year time series (2010–2050) daily IPCC SRES A1B (medium emissions scenario) climate scenario data from the PRECIS forced by GCM-HadCM3 and two future land cover scenarios data (A2a_version2, B2a_version2), analyzed spatial-temporal variability of land surface thermal-hydrologic exchange in the next 40 years through two group experiment runs: (i) A1B climate scenario data and A2a_version2 land cover scenario data and (ii) A1B climate scenario data and B2a_version2 land cover scenario data. Then land surface water and heat flux changes were analyzed for the regions suffering from land cover conversion to further explore the impact of land cover changes on the water and heat fluxes.
Land cover scenario data used in this study were developed by Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences. Combined with observational data of 735 meteorological stations in China and based on the climate change data of HadCM3 A1FI, A2a, and B2a, temporal-spatial variable raster data series of China HLZ (Holdridge life zone) ecosystem were obtained. Then, the marginal conversion model was established and run with these data and then China’s future land cover change scenarios temporal series data were simulated. Detailed description of the production process can refer to Yue et al. [
Spatial dynamics of A2a land cover change scenario in the next 40 years.
Interannual change of cultivated land and woodland area percentage in the next 40 years under A2a and B2a land cover change scenarios.
The atmospheric drivers for EASS included air temperature, relative humidity, precipitation, wind speed, and incoming shortwave radiation. The Providing Regional Climates for Impacts Studies (PRECIS) dataset was acquired from GCM-HadCM3 in Hadley Centre for Climate Prediction and Research with high resolution at
Interannual change of precipitation and air temperature in the next 40 years under A2a scenario.
1 : 1,000,000 China soil database used in this study was built by Institute of Soil Science, Chinese Academy of Sciences [
All the driving data were unified at the same scale through rational scaling methods because the simulated experiments were based on spatial resolution of
We chose the measured data in 2003 at QYZ (26.733°N, 115.050°W), FR-Pue (43.741°N, 3.596°W), AT-Neu (47.116°N, 11.320°W), CA-NS6 (55.917°N, −98.964°E), FI-Kaa (69.141°N, 27.295°W), and US-Bo1 (40.006°N, −88.290°W) (Table
EASS validation results for
Station name | Longitude | Latitude | Elevation ( |
PFTs |
|
ET (mm day−1) | ||||
---|---|---|---|---|---|---|---|---|---|---|
|
RMSE |
|
|
RMSE |
| |||||
FR-Pue | 3.59 | 43.74 | 270 | EBF | 0.83 | 49.96 | 0.91 | 0.57 | 66.60 | 0.83 |
AT-Neu | 47.12 | 11.32 | 970 | Grassland | 0.76 | 85.93 | 0.55 | 0.91 | 16.87 | 0.96 |
FI-Kaa | 27.30 | 69.14 | 155 | Wetland | 0.76 | 21.93 | 0.95 | 0.71 | 19.58 | 0.83 |
US-bo1 | −88.29 | 40.01 | 219 | Crop | 0.65 | 68.27 | 0.82 | 0.91 | 37.55 | 0.87 |
QYZ | 115.05 | 26.73 | 111 | ENF | 0.94 | 36.18 | 0.88 | 0.83 | 29.16 | 0.86 |
CA-NS6 | −98.96 | 55.92 | 244 | Shrub | 0.57 | 24.49 | 0.89 | 0.81 | 29.57 | 0.92 |
The meteorological variables for model inputs including incoming shortwave radiation, air temperature, and relative humidity, were measured in 2003 with eddy covariance (EC) systems at the towers, and all of them were recorded at 30 minute intervals. Precipitation above the canopy was recorded with a rain gauge. 3D wind speed was measured with a 3D sonic anemometer, and the half-hourly surface fluxes were measured simultaneously with the EC system. More detailed descriptions on observation of these sites can be found online at
In order to validate the model, land surface experiments were performed at the tower sites mentioned above. Simulated
We analyzed regional change of
Interannual spatial dynamic of
Similarly, Figure
Interannual spatial dynamic of ET (mm year−1) in the next 40 years under A2a scenario.
In addition, seasonal variability of
Seasonal variability of
Interannual average areal
In order to explore the impact of land cover changes on land surface water and heat fluxes, we chose a region where significant change occurred locates in Guizhou province (red circle area in Figure
Analysis of the impact of land cover scenario process on water and heat exchange for the year 2040 located in the east of Guizhou province.
Just concerned with climate change itself, air temperature and precipitation would increase in the next 40 years (Figure
As we all know, not only net radiation includes short-wave radiation balance but also long-wave radiation which is proportional to the fourth power of the temperature. Net radiation is equal to the sum of
The results also could be explained from the view of plant physiology. Forest vegetation has a high photosynthetic capacity. Absorbed solar energy would be converted to H2O vapor through photosynthesis process and dissipated into atmosphere from plants (canopy and leaf). This process needs to absorb heat, and consequently plants will reduce their surface temperature. With the leaf temperature decreasing and air temperature increasing,
In this study we addressed the comprehensive impact of climate change scenario and land cover change scenario on future land surface water and heat fluxes with a material circulation and energy flow coupled land surface model EASS and obtained the following preliminary conclusions through the above two simulation experiments.
(i) The simulated results under the two land cover scenarios show that spatial variation of
This research is supported by the National Basic Research Program of China (973 Program) (no. 2010CB950904 and no. 2010CB950902), by the research Grant (2012ZD010) of Key Project for the Strategic Science Plan in IGSNRR of CAS, a Research Plan of LREIS (O88RA900KA), CAS, the research Grants (41071059 and 41271116) funded by the National Science Foundation of China, a research grant named “Adaptation of Asia-Pacific Forests to Climate Change” (Project no. APFNet/2010/PPF/001) founded by the Asia-Pacific Network for Sustainable Forest Management and Rehabilitation, and “One Hundred Talents” program funded by the Chinese Academy of Sciences. The authors are grateful to data from FLUXNET and ChinaFLUX. The authors also thank Xiangzheng Deng and three reviewers for their useful comments and suggestions which significantly improved this paper.