scholarly journals Evaluation of a MODIS-Based Potential Evapotranspiration Product at the Point Scale

2008 ◽  
Vol 9 (3) ◽  
pp. 444-460 ◽  
Author(s):  
Jongyoun Kim ◽  
Terri S. Hogue
Keyword(s):  
Potential Evapotranspiration ◽  
Simple Algorithm ◽  
Sensor Data ◽  
Net Radiation ◽  
Point Scale ◽  
Time Step ◽  
Satellite Platform ◽  
Daily Time Step ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Daily Time

Abstract This paper outlines the development of a continuous, daily time series of potential evapotranspiration (PET) using Moderate Resolution Imaging Spectroradiometer (MODIS) sensor data from the Terra satellite platform. The approach is based on the Priestley–Taylor equation, incorporating a daily net radiation model during cloudless days. A simple algorithm using “theoretical clear-sky” net radiation (incorporating daily cloud fraction and cloud optical thickness) and PET is then used to estimate net radiation and PET under cloudy conditions. The method requires minimal ground-based observations for initial calibration of regional radiation algorithm coefficients. Point-scale comparisons are undertaken at four flux-tower sites in North America covering a range of hydroclimatic conditions and biomes. Preliminary results at the daily time step for a 4-yr period (2001–04) show good correlation (R2 = 0.89) and low bias (0.34 mm day−1) for three of the more humid sites. Results are further improved when aggregated to the monthly time scale (R2 = 0.95, bias = 0.31 mm day−1). Performance at the semiarid site is less satisfactory (R2 = 0.95, bias = 2.05 mm day−1 at the daily time step). In general, the MODIS-based daily PET estimates derived in this study are promising and show the potential for use in theoretical and operational water resource studies in both gauged and ungauged basins.

Alternative climate data sources for distributed hydrological modelling on a daily time step

2010 ◽  
Vol 25 (10) ◽  
pp. 1542-1557 ◽  
Author(s):  
Ashraf El-Sadek ◽  
Max Bleiweiss ◽  
Manoj Shukla ◽  
Steve Guldan ◽  
Alexander Fernald
Keyword(s):  
Hydrological Modelling ◽  
Data Sources ◽  
Climate Data ◽  
Time Step ◽  
Daily Time Step ◽  
Distributed Hydrological Modelling ◽  
Daily Time

A model of expansion and senescence of individual leaves of field-grown maize (Zea mays L.)

1994 ◽  
Vol 74 (1) ◽  
pp. 37-42 ◽  
Author(s):  
D. W. Stewart ◽  
L M. Dwyer
Keyword(s):  
Leaf Area ◽  
Zea Mays L ◽  
Growth Models ◽  
Time Step ◽  
Leaf Area Expansion ◽  
Daily Time Step ◽  
Area Expansion ◽  
Area Development ◽  
Leaf Area Development ◽  
Daily Time

Estimation of leaf area is a major component of plant growth models. In this study, a model was developed to calculate field-grown maize leaf area expansion and senescence on an individual leaf basis. The model began with an equation, based on cumulative growing degree-days from emergence, to initiate leaf area development. The model required daily values of maximum and minimum air temperature, solar radiation and precipitation, had essentially a daily time step with day and night modes, and could be run on commonly accessible computers (micros to mainframes). The objective of the development of the model was to assist plant breeders in optimizing leaf number and shape for adaptation to specific environments. Key words: Leaf area and number, temperature, phenological development

Simulation of the water and isotopic balance of a closed tropical lake at a daily time step (Lake Ihotry, South-West of Madagascar)

2006 ◽  
Vol 88 (1-3) ◽  
pp. 153-156 ◽  
Author(s):  
Christine Vallet-Coulomb ◽  
Françoise Gasse ◽  
Laurent Robison ◽  
Luc Ferry
Keyword(s):  
Tropical Lake ◽  
Time Step ◽  
South West ◽  
Daily Time Step ◽  
Daily Time

Population dynamics of rainbow smelt (Osmerus mordax) in Lakes Ontario and Erie: a modeling analysis of cannibalism effects

2000 ◽  
Vol 57 (8) ◽  
pp. 1594-1606 ◽  
Author(s):  
Brian F Lantry ◽  
Donald J Stewart
Keyword(s):  
Population Dynamics ◽  
Lake Erie ◽  
Lake Ontario ◽  
Osmerus Mordax ◽  
Time Step ◽  
Rainbow Smelt ◽  
Modeling Analysis ◽  
Daily Time Step ◽  
Annual Time ◽  
Daily Time

We used a stochastic stage-based matrix model (annual time step) and a bioenergetics model (daily time step) to simulate population dynamics, production, consumption, and conversion efficiency for rainbow smelt (Osmerus mordax) populations in Lakes Ontario and Erie. Cannibalism on young-of the-year (YOY) smelt by yearlings was the only scenario that reproduced alternate-year recruitment cycles observed in Lakes Ontario and Erie. Assuming constant survivorship and 5% variation in cannibalism, less than one YOY consumed per yearling smelt per year in both lakes could produce fluctuations greater than those observed. We found that at estimated daily mortality rates and during the pelagic phase of larvae only, 2% of the yearling smelt in Lake Erie and 5.1% in Lake Ontario need to consume one YOY per day to induce the observed abundance fluctuations. Bioenergetics simulations of alternating recruitment produced fluctuations in simulated values for annual gross production of approximately 6-7 and 31-59% for the Lake Ontario and Lake Erie smelt populations, respectively.

scholarly journals Mapping of water-related ecosystem services in the uMngeni catchment using a daily time-step hydrological model for prioritisation of ecological infrastructure investment – Part 1: Context and modelling approach

Water SA ◽  
2018 ◽  
Vol 44 (4 October) ◽  
Author(s):  
CJ Hughes ◽  
G De Winnaar ◽  
RE Schulze ◽  
M Mander ◽  
GPW Jewitt
Keyword(s):  
Ecosystem Services ◽  
Hydrological Model ◽  
Severe Drought ◽  
Water Shortages ◽  
Time Step ◽  
Ecological Infrastructure ◽  
High Assurance ◽  
Daily Time Step ◽  
Daily Time

South Africa is a semi-arid country which frequently faces water shortages, and experienced a severe drought in the 2016 and 2017 rainfall seasons. Government is under pressure to continue to deliver clean water to the growing population at a high assurance of supply. Studies now show that the delivery of water may be sustained not only through built infrastructure such as dams and pipelines, but also through investment in ecological infrastructure (EI). A daily time-step hydrological model was used to map areas which should be prioritised for protection or rehabilitation to sustain the delivery of water-related ecosystem services within the uMngeni catchment. We focused on three water-related ecosystem services, i.e.: water supply, sustained baseflow, erosion control/avoidance of excessive sediment losses. The two key types of degradation were modelled, namely, overgrazing and the invasion of upland areas by Black Wattle (Acacia mearnsii). This, Part 1 of a paper in 2 parts, provides a discussion on the role of EI in delivering water-related ecosystem services, describes the motivation for the study, and the methods used in modelling and mapping the catchment. The results of this modelling exercise are presented in Part 2, which also explores and illustrates the potential hydrological benefits of rehabilitation and protection of EI in the uMngeni Catchment.

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