Article
Agronomy
Qun Du, HuiZhi Liu, Yang Liu, LuJun Xu, Jihua Sun
Summary: The study found that in the wet season, total evapotranspiration accounted for 60% of the annual total with an amount of 762.3 mm in 2016, much lower than the annual total precipitation (1780.2 mm). Photosynthetic active radiation (PAR) was the main controller of half-hourly net ecosystem exchange (NEE), while air temperature (T-a) mainly controlled seasonal variations in NEE. In 2016, the annual total NEE, gross primary production (GPP) and ecosystem respiration (RE) were -233.8, 796.6, and 562.8 g C m(-2) yr(-1), respectively.
AGRICULTURAL AND FOREST METEOROLOGY
(2021)
Article
Agronomy
Antje M. Lucas-Moffat, Frederik Schrader, Mathias Herbst, Christian Brummer
Summary: With the advancements in technology, eddy covariance flux measurements can now be conducted for a variety of trace gases. However, while statistical properties and gap-filling strategies have been well-studied for carbon dioxide, they are not as well-understood for other gases. In this study, a universal methodology was proposed to evaluate the performance of multiple gap-filling techniques and fill the gaps in eddy covariance datasets for any trace gas. The methodology was applied to datasets of three different trace gases, providing ensemble results and uncertainties. The study suggests using multiple gap-filling techniques to improve the robustness of flux aggregation.
AGRICULTURAL AND FOREST METEOROLOGY
(2022)
Article
Environmental Sciences
Wenhui Cui, Ting Fong May Chui
Summary: This study assessed surface energy fluxes and investigated energy balance closure in a complex urban area in Hong Kong. The results helped fill a gap in understanding surface energy and turbulent fluxes in compact cities with high-rise buildings, and shed insights into the future installation of eddy covariance towers in similar areas. The study found that the required height of eddy covariance towers in such urban sites might not be as restrictive as in other urban areas with low-rise buildings or low building density, making it more feasible to set up observation towers.
SCIENCE OF THE TOTAL ENVIRONMENT
(2021)
Article
Agronomy
Yazhen Jiang, Ronglin Tang, Zhao-Liang Li
Summary: This study proposes a physics-based full-factorial scheme for filling gaps in surface evapotranspiration (ET) observations, which outperforms four typical methods. The validation results show that the full-factorial scheme performs well for both hourly and daily gap-filling, with the best performance at grass sites and the worst performance at forest sites.
AGRICULTURAL AND FOREST METEOROLOGY
(2022)
Article
Green & Sustainable Science & Technology
Xiuying Wang, Yuancang Ma, Fu Li, Qi Chen, Shujiao Sun, Honglu Ma, Rui Zhang
Summary: Through infrared wetland research and machine learning, we constructed a predictive model for net ecosystem CO2 exchange (NEE) and studied the effect of outlier treatments in different seasons on the model. The results showed that outlier treatments improved the interpolation accuracy and data quality of NEE, and the multilayer perceptron (MLP) model was the most stable with the best interpolation effect. Additionally, there were seasonal differences in the prediction of NEE.
Article
Water Resources
Lucas Emilio B. Hoeltgebaum, Nelson Luis Dias, Marcelo Azevedo Costa
Summary: Practically all records of eddy-covariance flux measurements are affected by gaps, and this study proposes analog period methods for gap-filling, which outperform mean diurnal variation method and simple/multiple linear regression techniques. The proposed methods also perform better than REddyProc and evaporative fraction method for filling missing data.
HYDROLOGICAL PROCESSES
(2021)
Article
Agronomy
Songyan Zhu, Jon McCalmont, Laura M. Cardenas, Andrew M. Cunliffe, Louise Olde, Caroline Signori-Muller, Marcy E. Litvak, Timothy Hill
Summary: Eddy covariance is an effective technique for monitoring ecosystem fluxes, but complete timeseries are necessary for long-term data analysis, requiring reliable gap-filling methods. Random forest regression (RFR) has shown stability and superiority in mature ecosystems, but its performance in challenging ecosystems remains uncertain. This study assessed RFR for gap filling methane fluxes globally and explored other methodologies for filling gaps in carbon dioxide, water, energy, and methane fluxes in challenging ecosystems.
AGRICULTURAL AND FOREST METEOROLOGY
(2023)
Article
Environmental Sciences
Stuart L. Joy, Jose L. Chavez
Summary: The study focused on estimating ET in different agricultural fields using EC systems. The results indicate that footprint models can effectively adjust EC-measured ET data, improving the accuracy of the estimates.
Article
Agronomy
Weijie Zhang, Martin Jung, Mirco Migliavacca, Rafael Poyatos, Diego G. Miralles, Tarek S. El-Madany, Marta Galvagno, Arnaud Carrara, Nicola Arriga, Andreas Ibrom, Ivan Mammarella, Dario Papale, Jamie R. Cleverly, Michael Liddell, Georg Wohlfahrt, Christian Markwitz, Matthias Mauder, Eugenie Paul -Limoges, Marius Schmidt, Sebastian Wolf, Christian Bruemmer, M. Altaf Arain, Silvano Fares, Tomomichi Kato, Jonas Ardo, Walter Oechel, Chad Hanson, Mika Korkiakoski, Sebastien Biraud, Rainer Steinbrecher, Dave Billesbach, Leonardo Montagnani, William Woodgate, Changliang Shao, Nuno Carvalhais, Markus Reichstein, Jacob A. Nelson
Summary: We evaluated the underestimation of latent heat flux (LE) associated with high relative humidity (RH) for different eddy covariance (EC) systems using the FLUXNET2015 dataset. We found that closed-path EC systems showed the most significant underestimation when RH was above 70%, and the extent of underestimation varied among sites. We proposed a machine learning-based method to correct this underestimation and compared it with two energy balance closure-based LE correction approaches. Our results highlight the importance of considering the high RH bias in water fluxes when estimating ecosystem T/ET and WUE.
AGRICULTURAL AND FOREST METEOROLOGY
(2023)
Article
Agronomy
Oluwakemi Dare-Idowu, Aurore Brut, Joan Cuxart, Tiphaine Tallec, Vincent Rivalland, Bartosz Zawilski, Eric Ceschia, Lionel Jarlan
Summary: This study analyzed the impact of different vegetation types and climatic variables on energy balance closure and flux partitioning using a unique database of EC flux measurements in two agricultural sites in southwestern France. The results indicated that site location had a stronger effect on energy balance closure than crop type and stage, while rainfall and phenological stages were found to influence energy partitioning.
AGRICULTURAL AND FOREST METEOROLOGY
(2021)
Article
Plant Sciences
Hu Yao, Haijun Peng, Bing Hong, Qian Guo, Hanwei Ding, Yetang Hong, Yongxuan Zhu, Cheng Cai, Jinshu Chi
Summary: The study found that the Hongyuan alpine peatland acted as a CO2 sink in 2014 and 2015, with significant carbon uptake during both growing and non-growing seasons. The research also showed that non-growing season carbon emissions should not be overlooked, and that the CO2 flux in the non-growing season was more sensitive to warming than in the growing season. The importance of continuous eddy covariance measurements and time series analysis approaches for understanding the temporal variability in NEE and its correlation with environmental factors was emphasized.
FRONTIERS IN PLANT SCIENCE
(2022)
Article
Agronomy
John M. Frank, William J. Massman
Summary: This study compares different calibration methods for fast-response hygrometers and their influence on the flux measurements. The results show that the choice of calibration method and the sensor technology can significantly affect the flux differences. The piecewise calibration method resulted in the smallest differences, but the Lyman-alpha and KH2O sensors experienced severe drifts. Oxygen correction and tube attenuation spectral correction were found to be influential factors. The impact of hygrometers on energy balance closure was minor compared to the choice of sonic anemometer.
AGRICULTURAL AND FOREST METEOROLOGY
(2023)
Article
Agronomy
Nan Li, Junjiong Shao, Guiyao Zhou, Lingyan Zhou, Zhenggang Du, Xuhui Zhou
Summary: Accurately quantifying ecosystem respiration (ER) is crucial for understanding the feedback between the terrestrial carbon (C) cycle and climate change, but current estimations face challenges due to response differences of daytime and nighttime respiration to temperature and the effects of air humidity. This study modified daytime flux partitioning methods to estimate ER by integrating different temperature sensitivities of ER and relative humidity, showing that diurnal variations in temperature sensitivity and humidity are crucial for accurate ER estimation and should be incorporated into regional and global models.
AGRICULTURAL AND FOREST METEOROLOGY
(2022)
Article
Agronomy
Songyan Zhu, Robert Clement, Jon McCalmont, Christian A. Davies, Timothy Hill
Summary: This study proposes a novel method, Random Forest Robust (RFR), for filling data gaps in time series of CO2, water, and energy fluxes. The RFR method outperforms the standard marginal distribution sampling (MDS) method, improving R2 values by 15% (RFR3) and 30% (RFR10) and reducing uncertainty by 70%. The RFR method shows significant improvements in filling gaps for heat and water fluxes compared to CO2 fluxes, and performs well for longer gaps.
AGRICULTURAL AND FOREST METEOROLOGY
(2022)
Article
Geosciences, Multidisciplinary
Ramesh Dhungel, Robert Aiken, Steven R. Evett, Paul D. Colaizzi, Gary Marek, Jerry E. Moorhead, R. Louis Baumhardt, David Brauer, Seth Kutikoff, Xiaomao Lin
Summary: This study explores surface energy fluxes using three different approaches in the sorghum and corn crop seasons in Bushland, Texas. Results indicate that energy imbalance in the EC system is associated with two opposite ET hysteresis patterns, revealing insights into advective conditions and turbulent flux dynamics.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Ying Li, Annmarie G. Carlton, Manabu Shiraiwa
Summary: SOA's glass transition temperature and viscosity play important roles in the formation and evolution of atmospheric particulate matter; the Tg and viscosity of dry SOA are mainly influenced by different species at different locations and seasons; significant vertical variations exist in SOA, with winter exhibiting glass transition at lower altitudes.
ACS EARTH AND SPACE CHEMISTRY
(2021)
Article
Meteorology & Atmospheric Sciences
Cailing Zhao, Xianhong Meng, Yueqing Li, Shihua Lyu, Jianping Guo, Huizhi Liu
Summary: This study investigates the impact of soil moisture conditions on the triggering of afternoon convection over the Tibetan Plateau. The results show that the Tibetan Plateau has a higher potential for convection triggering compared to other regions, and convection over the plateau is mainly influenced by atmospheric background. Soil moisture is identified as the most critical factor in precipitation triggering in soil moisture-precipitation feedback.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2022)
Article
Chemistry, Multidisciplinary
Adrian M. Maclean, Ying Li, Giuseppe Crescenzo, Natalie R. Smith, Vlassis A. Karydis, Alexandra P. Tsimpidi, Christopher L. Butenhoff, Celia L. Faiola, Jos Lelieveld, Sergey A. Nizkorodov, Manabu Shiraiwa, Allan K. Bertram
Summary: This study successfully predicted the phase state and mixing times of water and organic molecules within aerosol particles in the atmosphere by developing viscosity parameterizations based on room-temperature viscosity data for simulated pine tree SOA and toluene SOA.
ACS EARTH AND SPACE CHEMISTRY
(2021)
Article
Biophysics
Yingqi Zheng, Huizhi Liu, Qun Du, Yang Liu, Jihua Sun, Huancai Cun, Leena Jarvi
Summary: The variability of seasonal precipitation distribution under global climate change can affect the carbon balance of ecosystems. Research conducted on the Lijiang alpine meadow in the southeastern Tibetan Plateau showed that during the wet season, the meadow acted as a carbon sink, while it varied between a weak carbon source and sink during the dry season. The monthly CO2 fluxes were mostly controlled by air temperature and soil water content. The study observed a large annual variation of CO2 uptake, which was influenced by the distribution of precipitation.
INTERNATIONAL JOURNAL OF BIOMETEOROLOGY
(2022)
Article
Environmental Sciences
Hongyi Li, Libo Zhou, Ge Wang
Summary: The land-atmosphere heat transfers over different regions of the Tibetan Plateau and their responses to the South Asian summer monsoon (SASM) were investigated. It was found that there were inhomogeneities in the land-atmosphere heat transfers over the plateau, with large differences among plateau stations. The heat transfers were strongly affected by the SASM evolution, with more significant impacts observed in southern station locations. Further investigations are needed to fully understand the complexities of the SASM impacts on the plateau.
Article
Engineering, Chemical
Catherine G. Masoud, Ying Li, Dongyu S. Wang, Erin F. Katz, Peter F. DeCarlo, Delphine K. Farmer, Marina E. Vance, Manabu Shiraiwa, Lea Hildebrandt Ruiz
Summary: Organic aerosol emitted from cooking is a major concern for indoor air quality, highlighting the importance of understanding aerosol emissions and partitioning in indoor spaces.
AEROSOL SCIENCE AND TECHNOLOGY
(2022)
Article
Meteorology & Atmospheric Sciences
Yang Liu, Huizhi Liu, Fengquan Li, Qun Du, Lujun Xu, Yaohui Li
Summary: This study investigates the water and carbon exchanges between grassland and the atmosphere in a semiarid alpine steppe ecosystem in Bange on the Tibetan Plateau. The results show that soil water content and vegetation index are important factors influencing water evaporation and plant growth. Additionally, the study reveals the variability of carbon exchanges across different years and seasons, with soil water content affecting photosynthesis and respiration processes.
ADVANCES IN METEOROLOGY
(2022)
Article
Meteorology & Atmospheric Sciences
Anlun Xu, Jian Li, Qun Du, Baoju Dong
Summary: Long-term eddy covariance flux observations in the Dali agriculture ecosystem on the southeastern margin of the Tibetan Plateau from 2007 to 2018 revealed similarities in diurnal and seasonal variations between sensible heat flux (Hs) and latent heat flux (LE), with LE exhibiting a larger amplitude. Fluctuations in turbulent fluxes were observed on an annual scale, with notable increases in annual average Hs, LE, and net CO2 ecosystem exchange (NEE) from 2007-2013 to 2014-2018. Surface energy and CO2 fluxes were significantly influenced by surrounding vegetation cover.
ADVANCES IN METEOROLOGY
(2022)
Article
Meteorology & Atmospheric Sciences
Cailing Zhao, Xianhong Meng, Lin Zhao, Jianping Guo, Yueqing Li, Huizhi Liu, Zhaoguo Li, Bo Han, Shihua Lyu
Summary: In this study, the energy mechanism of atmospheric boundary layer (ABL) development over the Tibetan Plateau (TP) was analyzed using intensive sounding observation data. The results showed that surface sensible heat flux, boundary layer entrainment energy, and heat flux at the top of the ABL affected ABL growth. The accumulated sensible heat flux played the most crucial role in ABL development.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2023)
Article
Meteorology & Atmospheric Sciences
Jingshu Zhu, Huizhi Liu, Yaohui Li, Lujun Xu, Qun Du, Xianhong Meng, Yang Liu
Summary: This study investigates the precipitation variations in the Three-River Headwater Region (TRHR) using multiple observational and reanalysis datasets. The results show a significant increasing trend in precipitation, mainly driven by southwestern moisture influxes. The atmospheric circulation over the Tibetan Plateau plays a key role in regulating the moisture transport towards the TRHR. These findings are important for optimizing water resources management in the face of global climate change.
Article
Environmental Sciences
Yu Morino, Ying Li, Yuji Fujitani, Kei Sato, Satoshi Inomata, Kiyoshi Tanabe, Shantanu H. Jathar, Yoshinori Kondo, Tomoki Nakayama, Akihiro Fushimi, Akinori Takami, Shinji Kobayashi
Summary: Secondary organic aerosol (SOA) formed from vehicle exhaust is a significant contributor to urban particulate matter in the atmosphere. However, there are uncertainties in the simulation of SOA by air quality models due to differences in SOA formation between vehicle types, exhaust aftertreatment devices, and oxidation conditions. This study conducted smog chamber experiments to investigate the formation of SOA from different vehicles under different conditions. The results showed that there are differences in the formation of SOA and its precursors under different conditions, highlighting the need for further examination of the characteristics of SOA.
ENVIRONMENTAL SCIENCE-ATMOSPHERES
(2022)
Article
Chemistry, Analytical
Rachel E. O'Brien, Ying Li, Kristian J. Kiland, Erin F. Katz, Victor W. Or, Emily Legaard, Emma Q. Walhout, Corey Thrasher, Vicki H. Grassian, Peter F. DeCarlo, Allan K. Bertram, Manabu Shiraiwa
Summary: Organic films on indoor surfaces play a crucial role in indoor chemistry, serving as a medium for reactions and partitioning of semi-volatile organic compounds. The chemical composition of these films remains poorly characterized, with studies showing similarities to cooking organic aerosols but with larger and more oxidized molecules. Viscosity measurements of the film material suggest low viscosity, although inclusion of unsaturation can explain discrepancies. Further research is needed to better understand viscosity measurements and parameterizations for modeled viscosity of indoor organic films.
ENVIRONMENTAL SCIENCE-PROCESSES & IMPACTS
(2021)
Article
Environmental Sciences
Weiqi Xu, Chun Chen, Yanmei Qiu, Ying Li, Zhiqiang Zhang, Eleni Karnezi, Spyros N. Pandis, Conghui Xie, Zhijie Li, Jiaxing Sun, Nan Ma, Wanyun Xu, Pingqing Fu, Zifa Wang, Jiang Zhu, Douglas R. Worsnop, Nga Lee Ng, Yele Sun
Summary: The study reveals that volatility and viscosity of aerosols in the North China Plain are significantly impacted by various factors, leading to differences in composition and formation pathways among different organic aerosol factors. The results suggest that kinetically limited gas-particle partitioning may play a crucial role in simulating secondary organic aerosol formation in the region.
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2021)
Article
Environmental Sciences
Natalie R. Smith, Giuseppe Crescenzo, Yuanzhou Huang, Anusha P. S. Hettiyadura, Kyla Siemens, Ying Li, Celia L. Faiola, Alexander Laskin, Manabu Shiraiwa, Allan K. Bertram, Sergey A. Nizkorodov
Summary: This study investigated the molecular composition, viscosity, and liquid-liquid phase separation of secondary organic aerosol (SOA) derived from synthetic mixtures of volatile organic compounds (VOCs) representing emission profiles for Scots pine trees under healthy and aphid-herbivory stress conditions. The results showed that stressed plant SOA exhibited phase separation over a broader humidity range than healthy plant SOA, with higher viscosity and increased abundance of higher molecular weight species. Additionally, the study highlighted the importance of studying properties of SOA generated from realistic multi-component VOC mixtures.
ENVIRONMENTAL SCIENCE-ATMOSPHERES
(2021)
Article
Environmental Sciences
Sabin Kasparoglu, Ying Li, Manabu Shiraiwa, Markus D. Petters
Summary: This study compares predicted and observed viscosities of sucrose and citric acid, using literature data on viscosity and glass transition temperature as a function of water content to constrain fragility parameterization. Measurements of sub-100 nm particle viscosities using the dimer relaxation method extend the available data to -28 degrees C. Predicted relationships align well with observations at room temperature and temperatures warmer than -28 degrees C, but discrepancies are observed at colder temperatures for sucrose particles. Simulations suggest that these deviations may be due to kinetic limitations associated with water uptake at dimer relaxation timescales. Equilibrium phase-state diagrams for sucrose and citric acid have been updated based on available information.
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2021)