Heat storage change (HSC) is a crucial component of lake's thermal energy budget. Conventional temperature profile based models of HSC require location specific parameters such as lakebed topography. Based on the half-order time-derivative formula of heat fluxes, an analytical model was formulated for estimating HSC from water surface temperature and solar radiation without using geography dependent parameters. The proposed model was tested against field measurements at Poyang Lake, a shallow inland lake, which has pronounced seasonal variations in water level and lake area. Our analysis indicates that the model accurately simulates diurnal HSC with a coefficient of determination of 0.94 and a root mean squared error (RMSE) of 77.5 +/- 21.6 Wm-2 for the study period. Larger nighttime RMSE (75.0 +/- 26.8 Wm-2) than the daytime value (55.1 +/- 19.7 W m-2) is attributable to larger measurement errors of nighttime turbulent fluxes. The estimation of HSC independent of temperature profile and lake-specific parameters by the proposed model facilitates remote sensing monitoring the HSC of global water bodies.

Riverine dissolved organic matter (DOM) is crucial to global carbon cycling and aquatic ecosystems. However, the geographical patterns and environmental drivers of DOM chemodiversity remain elusive especially in the waters and sediments of continental rivers. Here, we systematically analyzed DOM molecular diversity and composition in surface waters and sediments across 97 broadly distributed rivers using data from the Worldwide Hydrobiogeochemistry Observation Network for Dynamic River Systems (WHONDRS) consortium. We further examined the associations of molecular richness and composition with geographical, climatic, physicochemical variables, as well as the watershed characteristics. We found that molecular richness significantly decreased toward higher latitudes, but only in sediments (r = -0.24, p < 0.001). The environmental variables like precipitation and non-purgeable organic carbon showed strong associations with DOM molecular richness and composition. Interestingly, we identified that less-documented factors like watershed characteristics were also related to DOM molecular richness and composition. For instance, DOM molecular richness was positively correlated with the soil sand fraction for waters, while with the percentage of forest for sediments. Importantly, the effects of watershed characteristics on DOM molecular richness and composition were generally stronger in waters than sediments. This phenomenon was further supported by the fact that 11 out of 13 watershed characteristics (e.g., the percentages of impervious area and cropland) showed more positive than negative correlations with molecular abundance especially in waters. As the percentage of forest increased, there was a continuous accumulation of the compounds with higher molecular weight, aromaticity, and degree of unsaturation. In contrast, human activities accumulated the compounds with lower molecular weight and oxygenation, and higher bioavailability. Our findings imply that it may be possible to use a small set of broadly available data types to predict DOM molecular richness and composition across diverse river systems. Elucidation of mechanisms underlying these relationships will provide further enhancements to such predictions, especially when extrapolating to unsampled systems.

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.

Fossil pollen data can provide important information of past vegetation diversity, on the basis of established relationship between modern palynological and floristic diversity. However, current studies on modern pollen assemblages in China have not examined this relationship yet. Herein, we report a case study from Northeast China, aiming to investigate the representation of modern palynological diversity to regional floristic diversity. A total of 87 sets of modern pollen and vegetation data from various vegetation types were applied to assess modern palynological diversity and floristic diversity in Northeast China, and the relationship between palynological and floristic diversity was studied using spatial pattern comparison and correlation analysis. Moreover, to reduce representation bias related to pollen production and dispersal, we calibrated pollen data using the Regional Estimates of Vegetation Abundance from Large Sites (REVEALS) model with Pollen Productivity Estimates (PPEs) and Fall Speeds of Pollen (FSP). The results show that the spatial variations of palynological and floristic richness among vegetation types are similar, and have a good positive correlation ( r =0.41, p <0.01). However, palynological evenness presents a different spatial pattern from floristic evenness, with a weaker positive correlation ( r =0.21, p >0.05). The calibration on pollen data using REVEALS model minimized the differences in spatial patterns between palynological and floristic diversity, and improved the correlations between them (richness, r =0.50, p <0.01; evenness, r =0.33, p <0.01). Our study indicates that palynological richness in Northeast China could reflect regional floristic richness in general, and the calibration with REVEALS model is recommended for reconstructing past floristic diversity from pollen data.

蒸散是地球水分循环与能量转换的关键环节. 陆域蒸散的精准测算是地球物理、生物乃至环境过程研究的共同科学难题. 以英国Dalton和Penman等人为代表的开创性工作, 以及大气边界层湍流交换理论与实验的不断发展, 奠基了现代主流的蒸散测算方法. 20世纪90年代以来技术趋于成熟的涡动相关系统和卫星遥感等观测手段, 跨越寒带到热带、干旱区到湿润地区, 涵盖水体、湿地、森林、农田、草地、裸地、城市等不同下垫面类型, 极大地拓展了对蒸散过程认知的深度和广度; 捕捉了诸如地表夜间蒸散、蒸散迟滞现象、非均匀下垫面的湍流间歇、平流关联的岛屿效应、下垫面转捩效应等新的现象和事实, 对经典相似性理论和蒸散测算理论等提出了新的挑战; 最大熵增蒸散模型和非参数化蒸散模型等新方法和新理论的萌芽已经出现. 与此同时, 点位高频观测和航空航天遥感技术构筑了从植物气孔到叶片、植株、冠层、景观、流域等跨尺度测算手段, 在地表蒸散过程观测及机理解析上, 形成纵向深化及横向综合的新进展. 陆域蒸散新理念、新模型、新技术的综合性发展, 成为突破蒸散精准测算难题的基础条件, 这将为揭示地球系统的水-热-碳循环机理等全球性重大基础理论问题, 为满足农业灌溉与粮食安全、水资源精细化管理与生态环境保护、城市热环境调控与全球升温适应对策等国家重大需求, 提供更为严谨坚实的科学理论依据和实验支撑.

Amplification of biosynthetic gene clusters is important to increase secondary metabolite production. However, the copy number of amplified gene clusters is difficult to control precisely. In this study, the tandem amplification of a 70 kb bleomycin biosynthetic gene cluster was precisely regulated through the combined strategy of a ZouA-dependent DNA amplification system and double-reporter-guided recombinant selection in Streptomyces verticillus ATCC15003. The production of bleomycin in the recombinant strain containing six copies of the bleomycin gene cluster was 9.59-fold higher than that in the wild-type strain. The combined strategy used in this study is powerful and applicable for precisely regulating the amplification of gene clusters and improving the corresponding secondary metabolite production.

Rice serves as the staple food for over 50% of the global population. Remotely-sensed based estimation of the gross primary production (GPP) and evapotranspiration (ET) of rice paddy fields is essential to assess global food security. In this study, we tested the application of a recently proposed remotely-sensed based water-carbon coupled model (PML-V2) in the lower reaches of the Poyang Lake plain, which is one of the nine production bases for crops in China. Evaluation using the eddy covariance measurements showed that, after parameter localization, the model reproduced the seasonal variations of GPP and ET for both the early rice and the late rice. The model performed reasonably well in the validation period because the key parameters (e.g., the quantum efficiency and the stomatal conductance coefficient) exhibited predictable seasonal variations. At the regional scale, the spatial distribution in multi-year GPP of rice (1365 ± 326 gCm−2year−1) can be explained by the vegetation cover fraction (R2 > 0.9); in comparison, the multi-year ET (1003 ± 65 mm/year) exhibits smaller spatial variations due to the high evaporation rate of the saturated soil surface of paddy fields. The water use efficiency of rice in this region varies around 1.35 gC/kgH2O with a standard deviation of 0.30. Our study shows that GPP and ET of rice can be estimated by remote sensing models without detailed crop management information, which is usually unavailable at regional scales.

Abstract Water surface‐atmosphere interactions play an important role in the climate system on regional and even global scale. Yet, it remains unclear whether radiative or aerodynamic forces contribute more to water surface evaporation, which may lead to different strategies in model parameterization. This study compared the eddy covariance observations taken at two contrasting lakes in China: Poyang Lake (subtropical, plain, and warm) in 2018 and Yamzhog Yum Co (alpine, plateau, and cold) in 2016. Both lakes of similar latitude have similar solar radiation, and Yamzhog Yum Co has a lower atmospheric pressure and air density and a larger temperature difference between water surface and air. Poyang Lake had a total evaporation of 741 mm from 6 May to 31 December 2018, relatively higher than that of Yamzhog Yum Co (677 mm) for the same season in 2016. Evaporation peaked in August for Poyang Lake but in October for Yamzhog Yum Co. The Penman equation disclosed that radiative forces contributed more than aerodynamic forces in both lakes. Evaporation was found to be most sensitive to air temperature in Poyang Lake but to surface net radiation in Yamzhog Yum Co, attributable to their sensitivity differences in iso‐radiative and isothermal conditions. Higher elevation reduced the aerodynamic contribution with lower air temperature and atmospheric pressure in Yamzhog Yum Co. The findings should be useful for understanding different behaviors of lake evaporation under common mechanisms.

The rapid development of the Integrated Multisatellite Retrievals for Global Precipitation Measurement (IMERG) precipitation product provides new opportunities for a wide range of Earth system and natural hazard applications. Spatiotemporal averaging is a common method for IMERG users to acquire suitable resolutions specific to their research or application purpose and has a direct impact on the overall quality of IMERG precipitation estimates. Here, three different IMERG, version 06 (V06), latency run products (i.e., early, late, and final) are assessed against a ground-based benchmark along a continuous series of spatiotemporal resolutions over the Huai River basin (HuaiRB) between June 2014 and May 2017. In general, IMERG products better capture the spatial pattern of precipitation, and demonstrate better reliability, in the southern portion of the HuaiRB relative to its northern region. Furthermore, the degradation of spatiotemporal resolution is associated with better rain/no-rain determination and the consistent improvement of rainfall product performance metrics. This improvement is more pronounced for IMERG products at fine spatiotemporal resolution. However, due to the presence of autocorrelated errors, the performance improvement associated with the degradation of spatiotemporal resolution is less than theoretical expectations assuming purely uncorrelated errors. Component analysis indicates that while both temporal and spatial aggregation do not mitigate temporally autocorrelated errors, temporal averaging can remove spatially autocorrelated error. Hence, temporal averaging is found to be more effective than spatial averaging for improving the quality of IMERG products. These results will inform users of the reliability of IMERG products at different spatiotemporal scales and assist in unifying former disparate validation assessments applied at different scales within the literature.

21世纪以来,水文遥感得到长足发展并成为当前地球科学的研究热点之一,同时也在流域生态水文过程研究中发挥了不可替代的作用,成为当前流域生态水文研究的重要手段.流域水文遥感在研究内容、研究方法、实际应用等方面具有流域整体性要求,涉及流域水量收支的闭合约束、要素反演检验的流域有效性以及流域水文模型的数据同化,指出流域尺度的反演检验、反演结果的不确定性和数据同化的误差溯源是当前面临的科学挑战.

大孔隙流是土壤优先流的一种,在植被发育区土壤大孔隙比较常见,对径流形成过程产生重要的影响.介绍了大孔隙流的研究方法,系统总结了近50年植被发育区土壤大孔隙对降雨入渗过程及径流形成过程的影响:从水分入渗的角度,大孔隙可以加快降雨入渗过程;由土壤大孔隙流与山坡产流的关系,大孔隙促进了边坡雨水的运动进而引起了快速产流;世界范围内的研究都表明土壤管流或大孔隙流是径流组分重要贡献者.

Surface heat fluxes are crucial to the energy and water exchanges between surface and the atmosphere. Hysteresis effect poses a challenge in model simulation of evaporation (latent heat flux, LE) at hourly or intradaily scales. The hidden mechanisms behind the hysteresis remain unclear, given the diverse reports in various climates, geographical locations, and underlying surfaces. This study took advantage of eddy covariance flux observation over Poyang Lake of China, an ephemeral lake experiencing seasonal shifts from land to water. It depicted the hysteresis behavior of LE to environmental forces for the period from May to July in 2018, a hydrologic transition period from land to water surface. Our results showed obvious clockwise hysteresis loops between LE and water vapor pressure deficit (VPD), surface temperature (Ts), and air temperature (Ta). Counterclockwise loops exhibited between LE and surface net radiation (Rn), wind speed (WS), and temperature difference (Ts-Ta). Rn, WS, and Ts-Ta dominants control the hysteresis effects and regulate LE variations. The hysteresis loops changed in direction, shape, and area when the surface shifted from land to water. It was primarily related to the lengthened lag time between LE and other variables except for WS, which was attributable to enhanced impacts from WS and VPD, and weakened impacts from Rn and Ts-Ta. The findings should help to improve our understanding of the complicated water-atmosphere interactions at the intradaily scale.

With increasing spatiotemporal resolution and accuracy, satellite-based precipitation estimations (SPEs) have become critical data sources for hydrological applications. Their global scale coverage and short latency perfectly fit the requirements of flood forecasting. However, the comprehensive evaluation of the latest generation of SPEs is an essential step before the confident use of these indirect precipitation estimators. Therefore, the latest releases of the Integrated MultisatellitE Retrievals for Global Precipitation Measurement (IMERG) Version 5 products, including the near-real-time "Early" run and "Later" run products (IMERG-E and IMERG-L, respectively), and the post-real-time "Final" run IMERG product (IMERG-F), are employed in this paper. Through the hydrometeorological assessment of these three IMERG products against dense gauge observations during the period from April 2014 to December 2015 over the Upper Huaihe River Basin (UHRB), the usability of IMERG products in hydrological application is explored via the Variable Infiltration Capacity model. The results indicate that, irrespective of a slight positive bias, the post-real-time IMERG-F product presents the best performance among the three IMERG products at both the grid scale and basin scale. Although all three IMERG products show remarkably high probability of detection (POD, approximately 0.82), the IMERG-E presents a relatively higher false alarm ratio (FAR = 0.37) in comparison with IMERG-L (FAR = 0.32) and IMERG-F (FAR = 0.31), which is primarily due to the significant overestimation in light rain events. In terms of hydrological simulations of streamflow, the dense gauge observations exhibit very good performance for both entire simulation period and flood events, as expected. IMERG-F demonstrates acceptable performance in entire simulation, while both IMERG-E and IMERG-L demonstrate poor performance. Given the clear overestimation in short-terms flooding and the notable underestimation in long-terms flooding, all three IMERG products should be used with caution in flood simulation over UHRB. Overall, this is a systematic assessment of IMERG products. We hope this study can provide useful guidelines for potential hydrologists of IMERG products and further IMERG algorithm development. Also, given the scope of on-going efforts to improve the IMERG products, we believe the subsequent versions of IMERG can be widely used in global or regional hydrological application, particularly in the field of flood forecasting.

小流域山洪预报一直是水文学研究的热点和难点问题之一.考虑到土壤大孔隙在径流形成过程中的重要作用,采用变动面积法为HBV模型增添大孔隙模块,并以黄泥庄小流域为研究区,使用改进后的HBV模型模拟分析了2010-2015年间6次洪水事件.结果表明:改进后的HBV模型在黄泥庄流域洪水模拟中模拟效果较好,预报精度均在乙级以上,可用于模拟类似小流域短历时高强度的洪水,从而为淮河流域上游山区的防汛决策提供重要参考.