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Tim R. McVicar  - - - 
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Wei Liang

122 shared publications

Graeme Newell

98 shared publications

Huade Guan

80 shared publications

Christian Körner

66 shared publications

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Publication Record
Distribution of Articles published per year 
(2007 - 2016)
Total number of journals
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11
 
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Article 1 Read 1 Citation Advantages of Using Microwave Satellite Soil Moisture over Gridded Precipitation Products and Land Surface Model Output ... Tiexi Chen, Tim R. McVicar, Guojie Wang, Richard A. M. de Je... Published: 20 May 2016
Remote Sensing, doi: 10.3390/rs8050428
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To improve the understanding of water–vegetation relationships, direct comparative studies assessing the utility of satellite remotely sensed soil moisture, gridded precipitation products, and land surface model output are needed. A case study was investigated for a water-limited, lateral inflow receiving area in northeastern Australia during December 2008 to May 2009. In January 2009, monthly precipitation showed strong positive anomalies, which led to strong positive soil moisture anomalies. The precipitation anomalies disappeared within a month. In contrast, the soil moisture anomalies persisted for months. Positive anomalies of Normalized Difference Vegetation Index (NDVI) appeared in February, in response to water supply, and then persisted for several months. In addition to these temporal characteristics, the spatial patterns of NDVI anomalies were more similar to soil moisture patterns than to those of precipitation and land surface model output. The long memory of soil moisture mainly relates to the presence of clay-rich soils. Modeled soil moisture from four of five global land surface models failed to capture the memory length of soil moisture and all five models failed to present the influence of lateral inflow. This case study indicates that satellite-based soil moisture is a better predictor of vegetation water availability than precipitation in environments having a memory of several months and thus is able to persistently affect vegetation dynamics. These results illustrate the usefulness of satellite remotely sensed soil moisture in ecohydrology studies. This case study has the potential to be used as a benchmark for global land surface model evaluations. The advantages of using satellite remotely sensed soil moisture over gridded precipitation products are mainly expected in lateral-inflow and/or clay-rich regions worldwide.
Article 0 Reads 0 Citations HCAS: A new way to assess the condition of natural habitats for terrestrial biodiversity across whole regions using remo... Tom D. Harwood, Randall J. Donohue, Kristen J. Williams, Sim... Published: 18 May 2016
Methods in Ecology and Evolution, doi: 10.1111/2041-210x.12579
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1.Consistent and repeatable estimation of habitat condition for biodiversity assessment across large areas (i.e. regional to global) with limited field observations presents a major challenge for remote sensing (RS). RS can describe what a site looks like and how it behaves (using time series), but is unable to distinguish anthropogenic impacts from natural dynamics. Consequently, it is possible to mistake a heavily degraded habitat for a natural habitat, e.g. a logged forest may appear identical to an intact open woodland. This problem is compounded by the existence of multiple natural states in any given environment, and spatial variation in the natural composition and structure of vegetation as a function of variation in environment. Uncertainty in assessing habitat condition from RS is often further exacerbated by sparseness in the spatial coverage of training data.2.We describe a novel generic, remote-sensing-based algorithm called HCAS (Habitat Condition Assessment System), designed to address the above sources of uncertainty and to be highly flexible in its application. It allows for variability in the definition of condition, and in the type and quantity of input data employed. Here we demonstrate the mechanics of the new algorithm in a simple worked example and its practical application in a case study using inferred “natural-only” reference data, reflective remotely sensed data, and associated environmental data, to map condition for Australia at a 0.01° resolution.3.We assess the behaviour and shortcomings of the method, and compare the national case study with estimates from two existing national datasets, and field measured condition data observed at 16,967 sites across the State of Victoria. The modelled predictions outperform both of the existing national datasets, explaining 52% of the variability in field observations for well-sampled cells (relative to 8 and 12% for the existing products).4.The methodology can potentially address some of the key pitfalls of condition modelling, and could be applied in other regions with sufficient coverage of reference data. The approach also has good potential to be extended to work with reference data for which condition is measured on a continuous scale, e.g. from field-based condition assessment initiatives.This article is protected by copyright. All rights reserved.
Article 1 Read 14 Citations Global-scale regionalization of hydrologic model parameters Hylke E. Beck, Albert I. J. M. van Dijk, Ad de Roo, Diego G.... Published: 01 May 2016
Water Resources Research, doi: 10.1002/2015wr018247
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Current state-of-the-art models typically applied at continental to global scales (hereafter called macro-scale) tend to use a priori parameters, resulting in suboptimal streamflow (Q) simulation. For the first time, a scheme for regionalization of model parameters at the global scale was developed. We used data from a diverse set of 1787 small-to-medium sized catchments (10-10000 km2) and the simple conceptual HBV model to set up and test the scheme. Each catchment was calibrated against observed daily Q, after which 674 catchments with high calibration and validation scores, and thus presumably good-quality observed Q and forcing data, were selected to serve as donor catchments. The calibrated parameter sets for the donors were subsequently transferred to 0.5° grid cells with similar climatic and physiographic characteristics, resulting in parameter maps for HBV with global coverage. For each grid cell, we used the ten most similar donor catchments, rather than the single most similar donor, and averaged the resulting simulated Q, which enhanced model performance. The 1113 catchments not used as donors were used to independently evaluate the scheme. The regionalized parameters outperformed spatially-uniform (i.e., averaged calibrated) parameters for 79% of the evaluation catchments. Substantial improvements were evident for all major Köppen-Geiger climate types and even for evaluation catchments > 5000 km distant from the donors. The median improvement was about half of the performance increase achieved through calibration. HBV with regionalized parameters outperformed nine state-of-the-art macro-scale models, suggesting these might also benefit from the new regionalization scheme. The produced HBV parameter maps including ancillary data are available via http://water.jrc.ec.europa.eu/HBV/. This article is protected by copyright. All rights reserved.
Article 1 Read 3 Citations Assessing the impact of measurement time interval when calculating wind speed means and trends under the stilling phenom... Cesar Azorin-Molina, Sergio M. Vicente-Serrano, Tim R. McVic... Published: 15 April 2016
International Journal of Climatology, doi: 10.1002/joc.4720
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In a globally warming climate, a weakening in observed near-surface wind speed has been recently termed as ‘global stilling’, showing a worldwide average trend of −0.140 m s−1 dec−1. The precise cause(s) of the land-surface stilling remains uncertain and led to this first assessment of how the two most common measurement time intervals of daily mean data averaged wind speed being either: (1) four-synoptic times (0000, 0700, 1300 and 1800 UTC; WS) or (2) 24-h wind run measurements (WR) can affect the estimation of wind speed averages and trends. This was performed across Spain for 1961–2011 (12 stations) and 1979–2008 (19 stations), where WS and WR daily wind speed observations were simultaneously recorded. Results indicate that mean wind speed is 0.24 m s−1 statistically greater for WS than WR measurements annually, being seasonally dependent with major differences in July (0.49 m s−1) and minor in December (−0.01 m s−1); that WS (−0.057 m s−1 dec−1) shows a more negative wind speed trend when compared with WR (−0.011 m s−1 dec−1) annually (and seasonally) for 1979–2008, but few trend differences are statistically significant; and that the percentage of stations showing stilling is greater for WS (63.2%) than WR (36.8%) annually (and seasonally) for the shortest period. In contrast, differences are almost negligible for 1961–2011. These findings may have direct implications for interdisciplinary areas such as agriculture and hydrology and wind renewable energy, and highlight the need of improving our understanding on the causes associated with wind speed declines under a climate change scenario.
BOOK-CHAPTER 1 Read 0 Citations Assessing the Characteristics of Required and Available Earth Observation Data Juan P. Guerschman, Randall J. Donohue, Tom G. Van Niel, Lui... Published: 07 April 2016
Earth Observation for Water Resources Management: Current Use and Future Opportunities for the Water Sector, doi: 10.1596/978-1-4648-0475-5_ch7
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BOOK-CHAPTER 1 Read 0 Citations Earth Observations and Water Issues Juan P. Guerschman, Randall J. Donohue, Tom G. Van Niel, Lui... Published: 07 April 2016
Earth Observation for Water Resources Management: Current Use and Future Opportunities for the Water Sector, doi: 10.1596/978-1-4648-0475-5_ch5
DOI See at publisher website