ABSTRACTBecause of the high elevation and complex topography of the Tibetan Plateau (TP), the role of lakes in the climate system over the Tibetan Plateau is not well understood. For this study, we investigated the impact of lake processes on local and regional climate using the Weather Research and Forecasting (WRF) model, which includes a one-dimensional physically based lake model. The first simulation with the WRF model was performed for the TP over the 2000–2010 period, and the second was carried out during the same period but with the lakes filled with nearby land-use types. Results with the lake simulation show that the model captures the spatial and temporal patterns of annual mean precipitation and temperature well over the TP. Through comparison of the two simulations, we found that the TP lakes mainly cool the near-surface air, inducing a decreasing sensible heat flux for the entire year. Meanwhile, stronger evaporation produced by the lakes is found in the fall. During the summer, the cooling effect of the lakes decreases precipitation in the surrounding area and generates anomalous circulation patterns. In conclusion, the TP lakes cool the near-surface atmosphere most of the time, weaken the sensible heat flux, and strengthen the latent heat flux, resulting in changes in mesoscale precipitation and regional-scale circulation. 相似文献
Forests are important parts of terrestrial ecosystems and play a leading role in regional and global nitrogen(N) cycles.Detailed assessment of N storage and allocation in China's forests is critical to improve the accuracy of regional or global N estimates and to guide policy-makers in the formulation of scientific and effective N management measures. However, the fore stN storage at national scale remains unclear. Based on 4420 forest field-investigated data, we investigated the N storage allocation in China's forests, explored the spatial patterns and influence factors. The data included vegetation information on various organs(i.e., leaf, branch, stem, and root) and soil information at different depths(0-30 cm and 0-100 cm). The total N storage in China's forest ecosystems was 14.45±8.42 tN hm~(–2); 0.86±0.51 tN hm~(–2)(5.95%) in vegetation and 13.59±8.40 tN hm~(–2)(94.05%) in soil(0–100 cm). The storage and allocation of N varied significantly across various regions and forest types. For different ecological regions, N storage varied from 10.34 to 23.11 tN hm~(–2), and the allocation ratio of N storage between vegetation and soil(0–100 cm) varied from 0.03 to 0.16. For different forest types, the N storage varied from 12.87 to 18.32 tN hm~(–2), and the allocation ratio of N storage between vegetation and soil(0–100 cm) varied from 0.03 to 0.09. The spatial patterns relative to N storage and allocation in forests were different. Climate was the primary factor influencing the spatial variation in forestN storage, while soil texture was the main factor influencing the spatial variation in N allocation. These first estimates of N storage and allocation ratio in China's forests are keys for improving the fitting accuracy of regional N cycle models and provide a reference for regional management of forestN. 相似文献
A model integrating geo-information and self-organizing map (SOM) for exploring the database of soil environmental surveys was established. The dataset of 5 heavy metals (As, Cd, Cr, Hg, and Pb) was built by the regular grid sampling in Hechi, Guangxi Zhuang Autonomous Region in southern China. Auxiliary datasets were collected throughout the study area to help interpret the potential causes of pollution. The main findings are as follows: (1) Soil samples of 5 elements exhibited strong variation and high skewness. High pollution risk existed in the case study area, especially Hg and Cd. (2) As and Pb had a similar topo-logical distribution pattern, meaning they behaved similarly in the soil environment. Cr had behaviours in soil different from those of the other 4 elements. (3) From the U-matrix of SOM networks, 3 levels of SEQ were identified, and 11 high risk areas of soil heavy metal-contaminated were found throughout the study area, which were basically near rivers, factories, and ore zones. (4) The variations of contamination index (CI) followed the trend of construction land (1.353) > forestland (1.267) > cropland (1.175) > grassland (1.056), which suggest that decision makers should focus more on the problem of soil pollution surrounding industrial and mining enterprises and farmland.
Journal of Geographical Sciences - The terrestrial hydrological process is an essential but weak link in global/regional climate models. In this paper, the development status, research hotspots and... 相似文献