The dependence of ecosystem water use partitioning on vegetation productivity at the inter‐annual time scale

2021 ◽  
Author(s):  
Zhaoxia Jing ◽  
Lei Cheng ◽  
Lu Zhang ◽  
Ying‐Ping Wang ◽  
Pan Liu ◽  
...  
Keyword(s):  
Water Use ◽  
Time Scale ◽  
Vegetation Productivity ◽  
Annual Time Scale ◽  
Annual Time

scholarly journals Attribution Analysis of Long-Term Trends of Aridity Index in the Huai River Basin, Eastern China

2020 ◽  
Vol 12 (5) ◽  
pp. 1743
Author(s):  
Meng Li ◽  
Ronghao Chu ◽  
Abu Reza Md. Towfiqul Islam ◽  
Yuelin Jiang ◽  
Shuanghe Shen
Keyword(s):  
River Basin ◽  
Time Scale ◽  
Aridity Index ◽  
Growing Season ◽  
Dominant Factor ◽  
Annual Time Scale ◽  
Huai River ◽  
Autumn And Winter ◽  
Annual Time ◽  
The Huai River Basin

This paper aims to combinedly investigate the spatiotemporal trends of precipitation (Pre), reference evapotranspiration (ET0), and aridity index (AI) by employing nonparametric methods based on daily datasets from 137 meteorological stations during 1961–2014 in the Huai River Basin (HRB). The dominant factors influencing ET0 and AI trends were also explored using the detrended and differential equation methods. Results show that (1) Pre, ET0, and AI were much larger in summer than in other seasons, and AI had a nonsignificant increasing trend in annual time scale, while Pre and ET0 exhibited decreasing trends, but AI showed a downward trend in spring and autumn (becoming drier) and an upward trend during summer and winter due to increased Pre (becoming wetter); (2) lower AI values were identified in north and higher in south, and lower ET0 was identified in south and higher in north in annual time scale, growing season and spring, while ET0 decreased from west to east in summer and winter, the spatial distribution of Pre was similar to that of AI; (3) for ET0 trends, in general, wind speed at two-meter height (u2) was the dominant factor in spring, autumn, winter, and annual time scale, while in other seasons, solar radiation (Rs) played a dominant role; (4) for AI trends, AI was mostly contributed by Pre in spring, autumn, and winter, the Rs contributed the most to AI trend in growing season and summer, then in annual time scale, u2 was the dominant factor; (5) overall, the contribution of Pre to AI trends was much larger than that of ET0 in spring, autumn, and winter, while AI was mostly contributed by ET0 in annual time scale, growing season and summer. The outcomes of the study may improve our scientific understanding of recent climate change effects on dry–wet variations in the HRB; moreover, this information may be utilized in other climatic regions for comparison analyses.

scholarly journals TWIG: A model to simulate the gravitropic response of a tree axis in the frame of elasticity and viscoelasticity, at intra-annual time scale

2011 ◽  
Vol 273 (1) ◽  
pp. 115-129 ◽  
Author(s):  
Catherine Coutand ◽  
Jean-Denis Mathias ◽  
Georges Jeronimidis ◽  
Jean-François Destrebecq
Keyword(s):  
Time Scale ◽  
Gravitropic Response ◽  
Annual Time Scale ◽  
Annual Time

scholarly journals Estimating the flood frequency distribution at seasonal and annual time scale

2012 ◽  
Vol 9 (6) ◽  
pp. 7947-7967 ◽  
Author(s):  
E. Baratti ◽  
A. Montanari ◽  
A. Castellarin ◽  
J. L. Salinas ◽  
A. Viglione ◽  
...  
Keyword(s):  
Objective Function ◽  
Frequency Analysis ◽  
Time Scale ◽  
Peak Flow ◽  
Flood Frequency ◽  
Cumulative Distribution ◽  
Annual Time Scale ◽  
Frequency Regime ◽  
Seasonal Flood ◽  
Annual Time

Abstract. We propose an original approach to infer the flood frequency distribution at seasonal and annual time scale. Our purpose is to estimate the peak flow that is expected for an assigned return period T, independently of the season in which it occurs (i.e. annual flood frequency regime), as well as in different selected sub-yearly periods (i.e. seasonal flood frequency regime). While a huge literature exists on annual flood frequency analysis, few studies have focused on the estimation of seasonal flood frequencies despite the relevance of the issue, for instance when scheduling along the months of the year the construction phases of river engineering works directly interacting with the active river bed, like for instance dams. An approximate method for joint frequency analysis is presented here that guarantees consistency between fitted annual and seasonal distributions, i.e. the annual cumulative distribution is the product of the seasonal cumulative distribution functions, under the assumption of independence among floods in different seasons. In our method the parameters of the seasonal frequency distributions are fitted by maximising an objective function that accounts for the likelihoods of both seasonal and annual peaks. Differently from previous studies, our procedure is conceived to allow the users to introduce subjective weights to the components of the objective function in order to emphasize the fitting of specific seasons or of the annual peak flow distribution. An application to the time series of the Blue Nile daily flows at Sudan-Ethiopia border is presented.

scholarly journals SPI-Based Spatiotemporal Drought over Sri Lanka

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
N. S. Abeysingha ◽  
U. R. L. N. Rajapaksha
Keyword(s):  
Sri Lanka ◽  
Time Scales ◽  
Time Scale ◽  
Standardized Precipitation Index ◽  
Annual Time Scale ◽  
Mk Test ◽  
Cropping Season ◽  
Thiessen Polygon ◽  
Slope Estimator ◽  
Annual Time

Drought is one of the most significant hazards in Sri Lanka. Status of drought in Sri Lanka was assessed using Standardized Precipitation Index (SPI) at 3, 6, and 12 months’ time scales using monthly rainfall (1970 to 2017) data of 54 weather stations. The frequency of drought events was evaluated using SPI, and trend of SPI was also detected using the Mann–Kendall (MK) test and Sen’s slope estimator. The result based on SPI identified hydrological years 1975-76, 1982-83, 1986-87, 1988-89, 2000-01, 2001-02, 2013-14, and 2016-17 as drought years for 52, 32, 35, 33, 33, 31, 31, and 31% of tested stations (54), respectively, at annual time scale. Comparison of the SPI at different time scales revealed that more drought events (SPI ≤ −1) occurred during Yala season than Maha cropping season. Considering the Thiessen polygon average rainfall, more frequent drought events occurred in the dry zone (57%) than the wet (49%) and intermediate zone (47%) at the annual time scale. SPI trend results showed greater increase in drought (59% of stations) during Yala seasons as compared to the Maha cropping season (15% of stations) in Sri Lanka.

Arctic Surface, Cloud, and Radiation Properties Based on the AVHRR Polar Pathfinder Dataset. Part II: Recent Trends

2005 ◽  
Vol 18 (14) ◽  
pp. 2575-2593 ◽  
Author(s):  
Xuanji Wang ◽  
Jeffrey R. Key
Keyword(s):  
Climate Change ◽  
Surface Temperature ◽  
Time Scale ◽  
Cloud Fraction ◽  
Annual Rate ◽  
The Arctic ◽  
Surface Temperature Change ◽  
Annual Time Scale ◽  
Annual Time ◽  
Arctic Surface

Abstract Over the past 20 yr, some Arctic surface and cloud properties have changed significantly. Results of an analysis of satellite data show that the Arctic has warmed and become cloudier in spring and summer but has cooled and become less cloudy in winter. The annual rate of surface temperature change is 0.057°C for the Arctic region north of 60°N. The surface broadband albedo has decreased significantly in autumn, especially over the Arctic Ocean, indicating a later freeze-up and snowfall. The surface albedo has decreased at an annual rate of −0.15% (absolute). Cloud fraction has decreased at an annual rate of −0.6% (absolute) in winter and increased at annual rates of 0.32% and 0.16% in spring and summer, respectively. On an annual time scale, there is no trend in cloud fraction. During spring and summer, changes in sea ice albedo that result from surface warming tend to modulate the radiative effect of increasing cloud cover. On an annual time scale, the all-wave cloud forcing at the surface has decreased at an annual rate of –0.335 W m−2, indicating an increased cooling by clouds. There are large correlations between surface temperature anomalies and climate indices such as the Arctic Oscillation (AO) index for some areas, implying linkages between global climate change and Arctic climate change.

Optimising fishery characteristics through control of an invasive species: strategies for redfin perch control in Lake Purrumbete, Australia

2018 ◽  
Vol 69 (9) ◽  
pp. 1333
Author(s):  
Daniel C. Gwinn ◽  
Brett A. Ingram
Keyword(s):  
Time Scale ◽  
Management Strategy ◽  
Annual Variation ◽  
Size Structure ◽  
Invasive Fish ◽  
Annual Time Scale ◽  
Recreational Value ◽  
Dependent Processes ◽  
Annual Time

Invasive fish species can present difficult management problems, particularly when the species has recreational value. One such case is redfin perch in Lake Purrumbete, Australia, which have recreational value but have become invasive in the lake. In this study we evaluated removal strategies for redfin perch in Lake Purrumbete with the aim of improving the quality of the recreational fishery. We evaluated removal scenarios for redfin perch with a population model and conducted a sensitivity analysis to determine the robustness of our general results. The results suggest that removal scenarios that direct exploitation, on an annual time scale, at fish ≤150-mm total length, with high levels of exploitation, will result in the greatest reduction in small undesirable fish and the greatest increase in large desirable fish in the lake. This was consistent across most assumptions about life-history characteristics, density-dependent processes and population dynamics rates, suggesting that this management strategy is robust to most relevant biological uncertainties. Furthermore, exploiting redfin perch on an annual time scale would result in the lowest annual variation in the population because of disruption of the age and size structure. These results can help managers choose strategies to manipulate the fishery of Lake Purrumbete to achieve more desirable characteristics.

scholarly journals Hydrometeorology of the Amazon in ERA-40

2005 ◽  
Vol 6 (5) ◽  
pp. 764-774 ◽  
Author(s):  
Alan K. Betts ◽  
John H. Ball ◽  
Pedro Viterbo ◽  
Aiguo Dai ◽  
José Marengo
Keyword(s):  
Water Vapor ◽  
Interannual Variability ◽  
Time Scale ◽  
Amazon Basin ◽  
Early Years ◽  
Atmospheric Water Vapor ◽  
Atmospheric Water ◽  
Temperature Bias ◽  
Annual Time Scale ◽  
Annual Time

Abstract The hydrometeorology of the Amazon basin in the ERA-40 reanalysis for 1958–2001 is compared with observations of precipitation, temperature, and streamflow. After 1979, the reanalysis over the Amazon has a small cool bias of the order of −0.35 K, and a small low bias of precipitation of the order of −0.3 mm day−1. In the early years (1958–72), there is a large upward drift in reanalysis precipitation and runoff associated with an upward drift in the atmospheric water vapor in the analysis, and a somewhat smaller downward drift of temperature as precipitation increases. In the presatellite data, there are inhomogeneities in the radiosonde and surface synoptic data, and there were problems with the variational analysis of humidity once satellite radiances were introduced. Approximate bias corrections can be made for precipitation and runoff on an annual basis, but this also removes some of the interannual variability. The reanalysis runoff–precipitation relationship is similar to the observed streamflow–precipitation relation, on an annual water-year basis. Compared to observations, ERA-40 precipitation for the Amazon is low by about 1.3 mm day−1 in the rainy season, and high by a smaller amount in the dry season. The precipitation bias produces a temperature bias in ERA-40 of the opposite sign on the annual time scale. The reanalysis has a small cold temperature bias after 1967, but on an annual time scale it reproduces the interannual variability of the observations. Although the biases in temperature and precipitation in recent decades are small, the difficulties with the analysis of atmospheric water vapor lead to large uncertainty in long-term trends of the water cycle.

scholarly journals A site-level comparison of lysimeter and eddy-covariance flux measurements of evapotranspiration

2016 ◽  
Author(s):  
Martin Hirschi ◽  
Dominik Michel ◽  
Irene Lehner ◽  
Sonia I. Seneviratne
Keyword(s):  
Eddy Covariance ◽  
Time Scale ◽  
Rainfall Events ◽  
Source Areas ◽  
Annual Time Scale ◽  
Time Period ◽  
Flux Measurements ◽  
A Site ◽  
Annual Time

Abstract. Accurate measurements of evapotranspiration are required for many meteorological, climatological, ecological, and hydrological research applications and developments. Here we examine and compare two well-established methods to determine evapotranspiration at the site level: lysimeter-based measurements (EL) and eddy-covariance (EC) flux measurements (EEC). The analyses are based on parallel measurements carried out with these two methods at the research catchment Rietholzbach in northeastern Switzerland, and cover the time period June 2009 to December 2015. The measurements are compared on various time scales, and with respect to a 40-year lysimeter-based evapotranspiration time series. Overall, the lysimeter and EC measurements agree well, especially on the annual time scale. On that time scale, the long-term lysimeter measurements also correspond well with catchment water-balance estimates of evapotranspiration. This highlights the representativeness of the site-level lysimeter and EC measurements for the entire catchment despite their comparatively small source areas and the heterogeneous land use and topography within the catchment. Furthermore, we identify that lack of reliable EC measurements during and following rainfall events (due to limitations of the measurement technique under these conditions) significantly contributes to an underestimation of EEC and to the overall energy balance gap at the site.

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