湖泊蒸发观测与计算方法研究进展

湖泊蒸发是连接湖泊水分循环与能量平衡的关键纽带之一,认识湖泊蒸发过程对于理解湖-气间相互作用机制十分重要。然而,由于湖泊的形态结构、地理位置和气候背景不同,各湖泊在不同时间尺度上的蒸发特征不同。湖泊蒸发存在复杂的物理驱动过程、时间尺度相关的反馈以及空间异质性。准确地捕捉并量化湖泊蒸发过程,仍是湖沼学、水文学和气象学等学科的重要研究内容。本文首先介绍了湖泊蒸发的主要观测手段,然后概述了湖泊蒸发在日内、季节、年际、年代际四种不同时间尺度的变化特征;梳理了不同时间尺度各要素对湖泊蒸发的影响,以及湖泊蒸发与湖泊面积和深度等形态结构特性及纬度和海拔等地理因素之间的关系;对自涡度相关技术等高精度仪器应用以来的湖泊蒸发研究进展做出了总结。     

On the Distribution of Mineral Nitrogen Forms in Polluted River Reaches in Urban Territories

Statistical analysis of data collected in field observations of river water quality in an urban area was used to recognize characteristic features of the distribution and relationships between concentrations of mineral nitrogen forms in polluted surface waters. The distribution of the relative mole fraction of nitrites in water is always unimodal, while other N forms can have bimodal distributions. Significant correlations between the concentrations of nitrites, nitrates, ammonium, and the total mineral nitrogen were found to exist in waters heavily polluted with nitrogen compounds. These correlations are interpreted based on a simple kinetic model of nitrification and denitrification processes. Denitrification processes are shown to play an important role in nitrogen balance in polluted waters. An estimate is proposed for the admissible level of river water pollution by nitrogen-containing compounds.     

Prediction of hourly actual evapotranspiration using neural networks,genetic programming,and statistical models

The complexity of the evapotranspiration process and its variability in time and space have imposed some limitations on previously developed evapotranspiration models. In this study, two data‐driven models: genetic programming (GP) and artificial neural networks (ANNs), and statistical regression models were developed and compared for estimating the hourly eddy covariance (EC)‐measured actual evapotranspiration (AET) using meteorological variables. The utility of the investigated data‐driven models was also compared with that of HYDRUS‐1D model, which makes use of conventional Penman–Monteith (PM) model for the prediction of AET. The latent heat (LE), which is measured using the EC method, is modelled as a function of five climatic variables: net radiation, ground temperature, air temperature, relative humidity, and wind speed in a reconstructed landscape located in Northern Alberta, Canada. Several ANN models were evaluated using two training algorithms of Levenberg–Marquardt and Bayesian regularization. The GP technique was used to generate mathematical equations correlating AET to the five climatic variables. Furthermore, the climatic variables, as well as their two‐factor interactions, were statistically analysed to obtain a regression equation and to indicate the climatic factors having significant effect on the evapotranspiration process. HYDRUS‐1D model as an available physically based model was examined for estimating AET using climatic variables, leaf area index (LAI), and soil moisture information. The results indicated that all three proposed data‐driven models were able to approximate the AET reasonably well; however, GP and regression models had better generalization ability than the ANN model. The results of HYDRUS‐1D model exhibited that a physically based model, such as HYDRUS‐1D, might be comparable or even inferior to the data‐driven models in terms of the overall prediction accuracy. Based on the developed GP and regression models, net radiation and ground temperature had larger contribution to the AET process than other variables. Copyright © 2010 John Wiley & Sons, Ltd.     

The possible connection between ionization in the atmosphere by cosmic rays and low level clouds

Recent analysis of monthly mean cloud data from the International Satellite Cloud Climatology Project uncovered a strong correlation between low cloud and the cosmic ray flux for extensive regions of the Earth. Additional data have been recently released covering the period up to September 2001 with which we have made a new study of the geographical variation of the correlation between low cloud and predicted ionization level from cosmic rays at an altitude of 2 km. When analysed globally, we find that the correlations do not correspond to the latitude variation of cosmic ray flux and they are not field significant. Nonetheless they appear to be marginally field significant over broad latitude and longitude bands with a peak positive correlation at 50 degrees North and South and a tendency to negative correlation at lower latitudes. The correlation is strongest over the North and South Atlantic. Several of these features are consistent with the predictions of the electroscavenging process.We use a simple model to calculate the climatic impact should the correlation be confirmed. We show that, under the most favorable conditions, a reduction in low cloud cover since the late 19th century, combined with the direct forcing by solar irradiance can explain a significant part of the global warming over the past century, but not all. However, this computation assumes that there is no feedback or changes in cloud at other levels.     

Improved prediction of vegetation composition in NW European softwater lakes by combining location,water and sediment chemistry

Isoetids, as indicators of near-pristine softwater lakes, have a high priority in national and international (European Water Directive Framework) assessments of ecological lake quality. Our main goal was to identify the most important environmental factors that influence the composition of plant communities and specifically determine the presence and abundance of the isoetid Lobelia dortmanna in NW European softwater lakes. Geographical position and composition of surface water, porewater, sediment and plant communities were examined in 39 lakes in four regions (The Netherlands, Denmark, West Norway and East Norway) distributed over a 1,200-km long distance. We confirmed that lake location was accompanied by significant changes in environmental variables between NW European lakes. Lake location was the single most important determinant of vegetation composition and it had significant individual contributions independent of the coupling to environmental variables. This influence of location was supported by a significant decline of community similarity with geographical distance between pairs of lakes at regional, inter-regional and international scales. Combining the geographical position with environmental variables for surface water, porewater and sediment significantly improved prediction of vegetation composition. Specifically, the combination of latitude, surface water alkalinity, porewater phosphate and redox potential offered the highest correlation (BIO ENV correlation 0.66) to vegetation composition. This complex analysis can also account for high sediment variability in the littoral zone of individual lakes, by using site-specific physico-chemical sediment factors, and offer better predictions of vegetation composition when lake water chemistry is relatively homogeneous among lakes within regions.     

GIS技术在洪湖环境演变研究中的应用

本文运用GIS技术,探索了洪湖环境的近期变化及其机理,以空间的、定量的形式,展示了与修建隔堤、分割湖区、围湖垦殖及水位控制等人为活动因素相联系的湖泊环境变化效应和过程,分析了湖中挺水植物分布的动态变化与趋协。这项工作进一步表明了地理信息系统方法在湖泊环境变化的监测、评价和研究中具有独特的功效和实用价值。     

Effect of coastline configuration on precipitation distribution in coastal zones

The effects of coastline, together with the other geographical and topographical factors such as longitude, latitude, elevation and distance from sea, on mean annual precipitation are investigated for the coastal area of the eastern Black Sea region. In this location, mountains run parallel to the sea coast. The coastline configuration is represented by a new variable, the coastline angle. A multiple linear regression (MLR) analysis is performed on mean annual precipitation recorded in coastal and inland gauges. In the study area, three variables—longitude, latitude and coastline angle—can explain 81% of the spatial variability of precipitation for the coastal gauges and 93% of that for the inland gauges. When the entire study area considered, without grouping the gauges, 80% of the spatial variability is explained by these variables. Copyright © 2009 John Wiley & Sons, Ltd.     

中国大陆地区热流数据的分布及其初步分析

本文首次系统地收集整理了观测资料比较齐全、国内公开发表的热流数据167个,并对之进行了初步分析。这些数据的地理分布还很不均匀,热流值变化范围为25—245mWm-2,多种平均方法得到的结果表明,中国大陆区域代表性热流值范围为61—68mWm-2。作者所作的经纬度网格和条带统计还揭示,数据覆盖区内热流沿经、纬向的分布有明显的差异,纬向条带平均热流值看来具有波状起伏变化的规律。这一结果已经得到日本及其周围海域热流数据的初步印证,如果获得更广泛的证实,无疑具有深刻的地质和地球物理意义     

Spatial distribution of surface energy fluxes over the Loess Plateau in China and its relationship with climate and the environment

China's Loess Plateau is located at the edge of the Asian summer monsoon in a transition zone of climate and ecology. In the Loess Plateau, climate and environments change along with space, which has an obvious impact on the spatial distribution of surface energy fluxes. Because of scarce land-surface observation sites and short observation time in this area, previous studies have failed to fully understand the land-surface energy balance characteristics over the entire the Loess Plateau and their effect mechanisms. In this paper, we first test the simulation ability of the Community Land Model(CLM) model by comparing its simulated data with observed data. Based on the simulation data for the Loess Plateau over the past thirty years, we then analyze the spatial distribution of surface energy fluxes and compare the pattern differences between the area averages for the driest year and wettest year. Furthermore, we analyze the relationship between the spatial distribution of the components of the surface energy balance with longitude, latitude, altitude, precipitation and temperature. The main results are as follows: the spatial distribution of surface energy fluxes are significantly different, with the surface net radiation and sensible heat flux increasing from south to north and latent heat flux and soil heat flux decreasing from southeast to northwest. The sensible heat flux at the driest point is nearly twice as high as that at the wettest point, whereas the latent heat flux and soil heat flux at the driest point are half as much as that at the wettest point. The impact of variations of annual precipitation on the components of the surface energy balance is also obvious, and the maximum magnitude of the changes to the sensible heat flux and latent heat flux is nearly 30%. To a certain extent, geographical factors(including longitude, latitude, and altitude) and climate factors(including temperature and precipitation) affect the surface energy fluxes. However, the surface net radiation is more closely related to latitude and altitude, sensible heat flux is more closely related to the monsoon rainfall and latitude, and latent heat flux and soil heat flux are more closely related to the monsoon rainfall.     

Using entropy theory to improve the definition of homogeneous regions in the semi-arid region of Brazil

ABSTRACT

Although the semi-arid region of Brazil appears to be homogeneous due to drought conditions, there is a great deal of variability in climatic elements in the region, so that the definition of homogeneous regions will provide the deployment of measures appropriate for each locality. However, the limited information on climatic parameters in the region makes it difficult to define these regions. This problem can, however, be alleviated by the use of entropy theory. Therefore, this study aimed to investigate the potential of the theory to identify hydrologically homogeneous regions for conditions of the semi-arid region of Brazil. Entropy-based Disorder Index (DI) data were computed, based on monthly precipitation and monthly water balance (precipitation – reference evapotranspiration) for 290 gauge stations. For defining homogeneous regions, cluster analysis was utilized, using the data on geographical information about rain gauges (latitude and longitude), annual precipitation, annual water balance, coefficient of skewness, coefficient of kurtosis and DI. The identification of homogeneous regions in the Brazilian semi-arid region was only possible when the grouping of stations was performed, based on DI for precipitation and latitude. Results showed the definition of seven homogeneous regions in the semi-arid region of Brazil.     

Ecologically Tolerable Impact Levels of Abiotic Factors in Water Bodies in Russia and Neighboring Countries: Dependence on the Geographic and Climatic Conditions

Largest river basins in Russia, Lithuania, Ukraine, and Uzbekistan are compared with respect to the admissible levels of the environmental physicochemical factors, the violation of which entails ecological disturbance of hydrobiont communities. The determination analysis of data is used to study the dependence of the degree of adaptation of limnetic ecosystems to external impacts on the sampling site (water column or ground), the latitude, climate, distance from sea, and the density of population in the region under study. Geographical and climatic classifications of regions are proposed based on the variability in the limits of environmental tolerance to abiotic impacts.     

2003年11月超强磁暴热层大气密度扰动及其与焦耳加热和环电流指数的关系——CHAMP卫星观测

本文利用CHAMP卫星加速度仪测量数据，计算和分析2003年11月20～21日大磁暴期间大气质量密度扰动的全球分布特征；研究暴时变化与极区大尺度对流引起的全球焦耳加热总功率及环电流指数SYM H之间的关系.结果表明，磁暴期间400 km高度上热层大气质量密度大幅度上升， NRLMSISE 00模式预测值与此相比有很大差别；暴时大气密度的增大存在昼/夜半球不对称性：白天强于夜晚，且白天随纬度的分布呈现出比较复杂的图像，在赤道附近和南半球中低纬区（10°N ～50°S）大气密度增大较强，并呈双峰分布，两个峰分别位于0°和45°S，另外在极区也出现大气密度扰动的局部极大，而在夜晚，大气密度变化南北半球比较对称，在赤道低纬区大气密度增大较强；互相关分析表明，中低纬区大气密度变化滞后于全球焦耳加热总功率3～7 h，滞后于环电流指数（SYM H）0～3 h，与二者存在很强的相关，表明极区焦耳加热和赤道环电流过程对暴时热层大气密度扰动有重要影响.     

Investigation of the controlled factors influencing carbon isotope composition of foxtail and common millet on the Chinese Loess Plateau

To apply carbon isotope composition(? 13C) analyses of C4 plants to the quantitative reconstruction of paleoclimate, the functional mechanism linking plant ? 13C(? 13Cp) to the environment, which is based on the plants' physiological characteristics and morphological adaptability, must be thoroughly understood. Foxtail millet(Setaria italic) and common millet(Panicum miliaceum), as C4 plants, are representative crops of the rain-fed agriculture present in northern China. Fossil millets are ideal for paleoclimatic studies because of the ease of acquisition and identification to the species level. Modern seeds of foxtail and common millet collected from different habitats of the Chinese Loess Plateau, and their carbon isotope compositions, were analyzed and correlated with environmental factors, such as latitude, altitude, temperature, precipitation, water availability, and relative humidity. The results showed that the ? 13 C of foxtail millet had a significantly negative correlation with latitude(R=?0.46), which may indicate the influence of light. The effect of light on the ? 13 C of foxtail millet accounted for only 21% of variability, while other climatic factors did not exert significant influences. Thus, the ? 13 C of foxtail millet was not suitable for extracting climatic information. The ? 13 C of common millet was significantly and positively correlated with precipitation during the growing period(R=0.75), explaining 56% of variability. The functional mechanisms analyzed, using the plants' physiological characteristics and morphological adaptability, indicated that common millet can adapt to environmental changes because of stomatal sensitivity and some non-stomatal factors. Therefore, the ? 13 C of common millet can record precipitation during growth and is a promising factor for paleoclimatic reconstruction.     

Recognition method for mid‐ to long‐term runoff forecasting factors based on global sensitivity analysis in the Nenjiang River Basin

Mid‐ to long‐term runoff forecasting is important to China. Forecasting based on physical causes has become the trend of this field, and recognition of key factors is central to recent development. Here, global sensitivity analysis based on back‐propagation arithmetic was used to calculate the sensitivity of up to 24 factors that affect runoff in the Nenjiang River Basin. The following five indices were found to be key factors for mid‐ to long‐term runoff forecasting during flood season: Tibetan Plateau B, index of the strength of the East Asian trough, index of the area of the northern hemisphere polar vortex, zonal circulation index over the Eurasian continent and index of the strength of the subtropical high over the western Pacific. The hydrological climate of the study area and the rainfall–runoff laws were then analysed in conjunction with its geographical position and topographic condition. The rationality of the results can be demonstrated from the positive analysis point of view. The results of this study provide a general method for selection of mid‐ to long‐term runoff forecasting factors based on physical causes. Copyright © 2012 John Wiley & Sons, Ltd.     

Comparison of climatic threshold of geographical distribution between dominant plants and surface pollen in China

The geographical distribution of dominant plant species in China was georeferenced and climatic variables were interpolated into all grids.Accordingly,the percentage distributions of principal pollen taxa based on 1860 surface pollen sites in China were selected and the related climate values were interpolated with the same method. The geographical and climatic comparison between the two data-sets indicated that the climate threshold of most pollen taxa from surface pollen is coherent with plant distributions. The climatic envelopes of dominant plant are mostly accordant with those of pollen taxa at certain levels. However, some distinct offsets of the climate ranges exist between the two datasets for most pollen taxa identified at family level, such as Ericaceae,Asteraceae, Poaceae and Chenopodiaceae. The present study provides for the first time rich information on temperature and precipitation in relation to pollen and plant distribution based on the datasets on a continental scale useful for global ecological modeling and Quaternary palaeoclimate reconstruction.     

Statistical characteristics of detectable inhomogeneities in observed meteorological time series

Statistical characteristics of detectable inhomogeneities [IHs] in more than 600 observed meteorological time series have been investigated using 16 objective homogenisation methods. Forty and 100 year long series of monthly or annual characteristics of surface air temperature, precipitation total and relative air humidity from the Czech Republic and Hungary were examined. The area of the part of the Czech observing network used here is smaller, and the density of sites is larger, than in the Hungarian network, resulting in higher spatial correlations among data in the Czech dataset relative to the Hungarian dataset. Time series with low number of gaps were supplied with interpolated data. Before homogenisation relative time series were created, using weighted averages of time series from the same geographical region as reference series. For ease of comparison, the magnitudes of the detected IHs are normalised with the standard deviation of the noise in the relative time series. Results show that observed meteorological time series usually contain large number of small IHs, and that the magnitude distribution of IHs from different data segments are surprisingly similar. Effects of different spatial coherences on the results are discussed.     

Formation of Vertical Thermal Structure in Lakes in Northwestern Russia and Finland

Vertical distribution of average annual temperature of water in lakes in the period of maximum water heating is analyzed as a function of zonal climatic factors and lake morphometry. Regression analysis is applied to hydrometeorological data on water temperature measurements at standard horizons made from 1958 to 1989 in 58 lakes in northwester Russia and eight lakes in Finland. The temperature of the top five-meter layer is found to depend mainly on the latitude. The major factors at a depth of 10 and lower are the lake morphometry and river water inflow.     

The hydrological response of surface water to recent climate variability: A remote sensing case study from the central tropical Pacific

For small tropical islands with limited freshwater resources, understanding how island hydrology is influenced by regional climate is important, considering projected hydroclimate and sea level changes as well as growing populations dependent on limited groundwater resources. However, the relationship between climate variability and hydrologic variability for many tropical islands remains uncertain due to local hydroclimatic data scarcity. Here, we present a case study from Kiritimati, Republic of Kiribati (2°N, 157°W), utilizing the normalized difference vegetation index to investigate variability in island surface water area, an important link between climate variability and groundwater storage. Kiritimati surface water area varies seasonally, following wet and dry seasons, and interannually, due to hydroclimate variability associated with the El Niño/Southern Oscillation. The NIÑO3.4 sea surface temperature index, satellite‐derived precipitation, precipitation minus evaporation, and local sea level all had significant positive correlations with surface water area. Lagged correlations show sea level changes and precipitation influence surface water area up to 6 months later. Differences in the timing of surface water area changes and variable climate‐surface water area correlations in island subregions indicate that surface hydrology on Kiritimati is not uniform in response to climate variations. Rather, the magnitude of the ocean–atmosphere anomalies and island–ocean connectivity determine the extent to which sea level and precipitation control surface water area. The very strong 2015–2016 El Niño event led to the largest surface water area measured in the 18‐year data set. Surface water area decreased to pre‐event values in a similarly rapid manner (<6 months) after both the very strong 2015–2016 event and the 2009–2010 moderate El Niño event. Future changes in the frequency and amplitude of interannual hydroclimate variability as well as seasonal duration will thus alter surface water coverage on Kiritimati, with implications for freshwater resources, flooding, and drought.     

Correlations between tropospheric and ionospheric parameters

Summary This paper discusses the general aspects of troposphere-ionosphere relationships and a suggested mechanism of a possible coupling between lower and upper atmosphere. The presentation includes results of a correlation analysis surface pressure and electron density of the ionosphericF2 layer for Washington, D.C., covering a time interval of 23 months. The correlation is significant for only three months and the sign of the correlation is not consistent. The three significant correlations between surface pressure andF2 electron density occur at times of an «index cycle»; i.e., the periodic fluctuations in the zonal circulation of the atmosphere and for a month of heavy hurricane activity. The review of correlations obtained by other authors also indicates that their significant correlations occur at times when intensive changes in the tropospheric circulation occur, especially in winter and spring (the time favored by index cycles) and at the beginning and retreat of the summer monsoon in India. The variable sign of correlation between surface pressure and ionospheric characteristics is considered to be the result of the ambiguity of surface pressure as an indicator for dynamic changes in the lower atmosphere which may possibly initiate certain changes in the upper atmosphere. It is speculated that the observed correlations are the effect of upward propagation of strong disturbances from the troposphere to the ionosphere. At the present time, however, no definite conclusion can be drawn as to the reality of the suggested troposphere-ionosphere relationships.