Climate and Vegetation Drivers of Terrestrial Carbon Fluxes:A Global Data Synthesis

The terrestrial carbon(C) cycle plays an important role in global climate change, but the vegetation and environmental drivers of C fluxes are poorly understood. We established a global dataset with 1194 available data across site-years including gross primary productivity(GPP), ecosystem respiration(ER), net ecosystem productivity(NEP), and relevant environmental factors to investigate the variability in GPP, ER and NEP, as well as their covariability with climate and vegetation drivers.The results indicated that both GPP and ER increased exponentially with the increase in mean annual temperature(MAT)for all biomes. Besides MAT, annual precipitation(AP) had a strong correlation with GPP(or ER) for non-wetland biomes.Maximum leaf area index(LAI) was an important factor determining C fluxes for all biomes. The variations in both GPP and ER were also associated with variations in vegetation characteristics. The model including MAT, AP and LAI explained 53%of the annual GPP variations and 48% of the annual ER variations across all biomes. The model based on MAT and LAI explained 91% of the annual GPP variations and 92.9% of the annual ER variations for the wetland sites. The effects of LAI on GPP, ER or NEP highlighted that canopy-level measurement is critical for accurately estimating ecosystem–atmosphere exchange of carbon dioxide. The present study suggests a significance of the combined effects of climate and vegetation(e.g.,LAI) drivers on C fluxes and shows that climate and LAI might influence C flux components differently in different climate regions.

Climatic Characteristics of Hail and Risk Zoning of Its Disaster Factor in Anhui Province

[ Objective] The research aimed to study climatic characteristics of hail and dsk zoning of its disaster factor in Anhui Province. [Method] Based on the hail-day records from 82 weather stations in Anhui Province, Chinese Meteorologica/Disaster Dictionary （1951 to 2005） and The Yearbook of Meteorological Disaster in Anhui Province （2006 to 2009）, we discussed the climatic characteristic and dsk zoning of hail disaster in Anhui Province. [Result] The hail days exhibited significant interdecadal variability, and it had a significant negative correlation with annual mean minimum temperature. The hail usually occurred from March to August, most frequently in June but less in autumn and winter. It most likely took place from aftemoon to sunset. The spatial distribution showed that the hail occurred more in northeast of Huaibei, south of Dabie Mountain and some areas of Huangshan Mountain, but less in Jianghuai region. The index of hail intensity was defined by three factors, the diameter, duration and gust grade, and the percentile method was used to grade the intensity of the hail disaster. This work provided a possibility for quantitative assessment of the intensity of hail disaster. The results of hail disaster risk zoning in Anhui Province showed that high dsk zones were concentrated in northeast of Huaibei, and low risk zones were mainly in south of Huaihe River. Finally, vedfied by historic disaster, it showed that the results of risk zoning had a certain rationality and feasibility. Conclusion The research could provide reference basis for hail disaster defense and assessment.

Zoning strategy of zonal modeling for thermally stratified large spaces

Large space buildings play a significant role in modern society because of their environmental advantages and market value.While the zonal model is promising for the efficient and rapid evaluation of the stratified thermal environment,there is a lack of a reasonable and convenient zoning strategy with the advent of modern computing.This paper presents a universal and practical zonal model,in which a simplified momentum equation is applied to consider air momentum preservation,transformation,and dissipation.Hence,the zoning structure is generalized and flexible.Moreover,limiting the dimensionless temperature constraint between adjacent zones establishes the connection between thermal nonuniformity and zoning results automatically.Simultaneously,the dimension and number of zones should be restricted within reasonable ranges to satisfy the characteristics of zonal simulation and reach the criteria of convergence.To further explore and validate the zonal model,a reduced-scale experimental model was constructed to replicate the thermal stratification in a mechanically ventilated large space by considering many crucial realistic factors.A particle image velocimetry(PIV)measurement was then conducted to visualize the airflow pattern and support the partition of zones.The results showed that the zonal simulation with adaptive zoning method can realize a similar accuracy with fewer zones and exhibit a better tolerance for zoning results compared to the conventional empirical zoning method.Furthermore,a case study of an atrium was performed to demonstrate the practicality and efficiency of the method for long-term dynamic simulations of complex thermal environments and building energy use.