Paper cuts (April-June 2013)

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A digest of papers of potential interest to OzEWEX members, published between April-June 2013.

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Observational Data

  • Chappell et al. find that blending gauge data with satellite precipitation estimates does not increase accuracy across Australia but does reduce the uncertainty of resulting rainfall estimates.
  • Peña-Arancibia et al. used rainfall gauge analyses for Australia and Asia to evaluate six reanalyses and satellite-based precipitation products, finding that the ensemble provides more information than any of the members.
  • Vreugdenhil et al. demonstrate a new method to map the distribution of clay pan soils from massive microwave remote sensing over Australia.
  • Flood demonstrates that MODIS BRDF parameters can effectively characterize the BRDF of Landsat imagery over large areas but do not capture BRDF of more local regions.

Model Evaluation and Benchmarking 

  • Chiew et al. review non-stationarity in hydrological response in south-eastern Australia. The non-stationarity observed during the Millennium drought can be used to improve models, but longer-term predictions are uncertain due to unpredictable temperature and CO2 effects
  • Zhao et al. show that spatial rainfall variability affects accuracy of water balance modelling and that ignoring this variability produced underestimates of streamflow.
  • Peeters et al. use Monte Carlo sensitivity analysis and Self Organising Maps to perform a pre-calibration sensitivity analysis of groundwater behaviour in the land-surface model AWRA-L.

Data Assimilation 

  • Su et al. evaluate soil moisture products from AMSR-E, ASCAT and SMOS against in-situ observations from southeast Australia. The products show similar error on average but with different error structures. Normalising the data was beneficial, but CDF matching was only marginally better than mean/standard-deviation matching.
  • Li et al. analyse the issue of routing time lags when assimilating stream discharge for flood forecasting, and conclude that the Ensemble Kalman Smoother is better able to account for these lags than the Ensemble Kalman Filter.
  • Emelyanova et al. evaluate four algorithms that blend highly resolved spatial data from one satellite sensor with highly resolved temporal data from another and find that their relative performance depends on the spatial and temporal variance structures.

Trends and Extremes 

  • Pepler et al. analyse the influence of East Coast Lows on rainfall on Australia’s Eastern seaboard and conclude that they are responsible for 23% of overall rainfall and 40% of large rain events.
  • Ishak et al. analyse annual maximum flood data for 491 Australian catchments and find significant decreasing trends in southeast and southwest Australia, that can largely be attributed to trends in ocean circulation modes (SAM, ENSO and IPO).

Vegetation Processes 

  • Medlyn et al. compare two recently published alternative models derived from optimal stomatal theory and show that stomatal behaviour clearly departs from that predicted when Rubisco activity is limiting to photosynthesis.
  • Using satellite observations, Donohue et al.provide evidence that CO2 fertilisation effect is now a significant global land surface process.
  • Meng et al. perform WARF regional climate model simulations with satellite observed albedo over south-east Australia to demonstrate that the effect of drought on albedo reduces turbulent heat fluxes and a decrease in moist static energy density in the boundary layer.
  • Brookhouse et al.re-evaluate streamflow measurements from several catchments with mountain ash. They conclude that the general shape of the ‘Kuczera curve’, if not its parameters, are supported and also appear to apply to other ash species.
  • Feikema et al. used the Macaque model to examine the relative importance of rainfall, fire severity and forest type on post-fire streamflow patterns, and conclude that for high rainfall, forest age dominates streamflow response, whereas annual rainfall is the best predictor in low rainfall environments.
  • Smettem et al. analyse satellite-derived LAI time series over southwest Western Australia and conclude that the response of forest LAI to rainfall variations is buffered, which was attributed to the availability of deep soil moisture and groundwater.
  • Poot and Veneklaas compared water relations of four eucalypt species in southwestern Australia and found strong interaction with soil properties. The observed differences were consistent with declines that have been observed in recent decades.
  • Using satellite data, Holmgren et al. show that higher climatic variability is associated with reduced tree cover in the wet tropics globally. In Australia, greater wet extremes help to establish new cohorts of trees, but this is overwhelmed by mortality in extreme dry years.
  • Mackay et al. demonstrate that considering carbon storage on land as a means to ‘offset’ CO2 emissions from burning fossil fuels (an idea with wide currency) is scientifically flawed.

Hydrological Prediction

  • Van Dijk et al. evaluate a global seasonal streamflow forecasting system. The ensemble prediction system could realise 54% of theoretical skill; further enhancement will require improvement in the observation of precipitation and catchment condition.
  • Zaman et al. analyse streamflow data from 429 small catchments in eastern Australia and propose a method to account for the effect of catchment size on flood quantile predictions.
  • Using data for 6 catchments in NSW, Caballero and Rahman present a method to regionalise the parameters of the Joint Probability Approach/Monte Carlo Simulation Technique used for estimating design floods in ungauged catchments.

 

 

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