林地最小生态环境需水量的研究

水对生态环境的重要影响已经引起了社会的广泛关注。作者分析并总结了当前生态环境需水方面的研究进展,包括生态需水的概念阐述,类型区分,生态需水量的相关计算方法,提出了目前生态环境需水研究中亟待解决的一些问题和展望了生态环境需水研究的发展趋势,并以山东东明、单县、夏津三地为代表,计算出黄河故道地区最小生态环境需水量,所得结果为区域生态建设提供依据。

Analysis on Temporal and Spatial Variation Characteristics of Potential Evapotranspiration in Guizhou Province

[Objective] The aim was to analyze temporal and spatial variation charac- teristics of potential evapotranspiration in Guizhou Province. [Method] According to information from 19 meteorological stations of Guizhou Province from 1960 to 2007, with the formulas of optimizational Penman-Monteith and SEBAL net radiation mod- el, the reference crop evapotranspiration ETo was calculated. Also with the spatial interpolation method of Arcgis 9.3, climate tendency rate statistics, K-M test, wavelet analysis and so on, the related regional differentiation and spatial and temporal change characteristics between meteorological factors from each monitoring station and ETo were analyzed. [Result] The results show that the correlation of potential evapotranspiration and meteorological factors in Guizhou Province demonstrates re- gional differentiation; there was no direct connection between the correlation of po- tential evapotranspiration and meteorological factors and the amount of meteorologi- cal factors in the year; there were 3 cycles in potential evapotranspiration, namely, 1 year, 5 years and 10 years, with 3 mutation points, respectively, in 1965, 1984 and 1999, mainly affected by air temperature, precipitation and solar radiation. [Conclusion] The research is of great significance in developing irrigation approach- es, adjusting agricultural structure and ecological construction.

Projected Changes of Palmer Drought Severity Index under an RCP8.5 Scenario

The potential change of drought measured by the Palmer Drought Severity Index （PDSI） is projected by using a coupled climate system model under a Representative Pathway 8.5 （RCP8.5） scenario.The PDSI changes calculated by two potential evapotranspiration algorithms are compared.The algorithm of Thomthwaite equation overestimates the impact of surface temperature on evaporation and leads to an unrealistic increasing of drought frequency.The PM algorithm based on the Penman-Monteith equation is physically reasonably and necessary for climate change projections.The Flexible Global Ocean-Atmosphere-Land System model,Spectral Version 2 （FGOALS-s2） projects an increasing trend of drought during 2051-2100 in tropical and subtropical areas of North and South America,North Africa,South Europe,Southeast Asia,and the Australian continent.Both the moderate drought （PDSI ＜-2） and extreme drought （PDSI ＜-4） areas show statistically significant increasing trends under an RCP8.5 scenario.The uncertainty in the model projection is also discussed.

Evapotranspiration and Removal Performance in the Treatment of High Salinity LandfilI-Leachate Using HSF

In this study, the water budget in the treatment of high salinity landfill-leachate was estimated and the influence of evapotranspiration （ET） on treatment performance was investigated. The salinity of the inside of horizontal subsurface flow constructed wetland （HSF） of the raw leachate inflow was 15.0± 3.4 g.Cl/L which was in the level of the salinity of the survival limit of reed, and that of the double diluted leachate inflow was 9.3 ± 1.9 g.CI7L. There were large differences in the vegetation between HSF of the raw leachate inflow and that of the double diluted leachate inflow. The dense vegetation bed of double diluted leachate inflow during the growing season （April-October） provided a high ET and a large water loss, which made great contributions to the reduction of the outflow load of COD and T-N. The HSF with die-back reeds in the non-growing season （November-March） provided a slight ET and a small water loss and made less of a contribution to pollutant removal compared to the HSF with dense vegetation bed during the growing season. However, the HSF with die-back reeds during the non-growing season exhibited higher removal performance than the unplanted HSF.

Spatio-temporal variation of the wet-dry conditions from 1961 to 2015 in China

As an important part of the regional environment, the wet-dry climate condition is determined by precipitation and potential evapotranspiration （expressed as ETo）. Based on weather station data, this study first calculated ETo by using the FAO56 Penrnan-Monteith model. Then, the dryness index K （ratio of ETo to precipitation） was used to study the spatio-temporal variation of the wet-dry condition in China from 1961 to 2015; moreover, dominant climatic factors of the wet-dry condition change were discussed. The annual precipitation and ETo of the Qinling-Huaihe line were close to a balance （K≈1.0）. The annual precipitation in most areas exceeded the ETo in the south of this line and the east of Hengduan Mountains （K〈0.0）, where the climate is wet. Furthermore, the precipitation in the northwest inland areas of China, where the climate is dry, was markedly lower than ETo （K≥4.0）. The overall annual K of China fluctuated around the 55-year mean and its linear trend was not significant. However, a relatively wet period of about 10 yr （1987-1996） was recorded. The overall annual K of China showed strong cyclicality on the time scale of 3, 7-8, 11 and 26-28 yr, and regional differences of the annual K trends and cyclicality were large. The degrees of wetness in the Northwest China and western Qinghai-Tibet Plateau were substantially increased, whereas the degrees of dryness in the Yunnan-Guizhou Plateau, Sichuan Basin, and Loess Plateau were markedly increased. The linear trend of the annual K in most regions of China was not significant, and the annual K of most areas in China showed strong cyclicality on the 8-14 yr time scale. Precipitation was the dominant factor of wet-dry condition change in most areas, especially in North China, where the annual K change was highly correlated with precipitation.

Regional applicability of seven meteorological drought indices in China

The definition of a drought index is the foundation of drought research.However,because of the complexity of drought,there is no a unified drought index appropriate for different drought types and objects at the same time.Therefore,it is crucial to determine the regional applicability of various drought indices.Using terrestrial water storage obtained from the Gravity Recovery And Climate Experiment,and the observed soil moisture and streamflow in China,we evaluated the regional applicability of seven meteorological drought indices:the Palmer Drought Severity Index(PDSI),modified PDSI(PDSI_CN) based on observations in China,self-calibrating PDSI(scPDSI),Surface Wetness Index(SWI),Standardized Precipitation Index(SPI),Standardized Precipitation Evapotranspiration Index(SPEI),and soil moisture simulations conducted using the community land model driven by observed atmospheric forcing(CLM3.5/ObsFC).The results showed that the scPDSI is most appropriate for China.However,it should be noted that the scPDSI reduces the value range slightly compared with the PDSI and PDSI_CN;thus,the classification of dry and wet conditions should be adjusted accordingly.Some problems might exist when using the PDSI and PDSI_CN in humid and arid areas because of the unsuitability of empiricalparameters.The SPI and SPEI are more appropriate for humid areas than arid and semiarid areas.This is because contributions of temperature variation to drought are neglected in the SPI,but overestimated in the SPEI,when potential evapotranspiration is estimated by the Thornthwaite method in these areas.Consequently,the SPI and SPEI tend to induce wetter and drier results,respectively.The CLM3.5/ObsFC is suitable for China before 2000,but not for arid and semiarid areas after 2000.Consistent with other drought indices,the SWI shows similar interannual and decadal change characteristics in detecting annual dry/wet variations.Although the long-term trends of drought areas in China detected by these seven drought indices during 1961-2013 are consistent,obvious differences exist among the values of drought areas,which might be attributable to the definitions of the drought indices in addition to climatic change.