ASoP (v1.0): a set of methods for analyzing scales of precipitation in general circulation models

General circulation models (GCMs) have been criticized for their failure to represent the observed scales of precipitation, particularly in the tropics where simulated daily rainfall is too light, too frequent, and too persistent. Previous assessments have focused on temporally or spatially averaged precipitation, such as daily means or regional averages. These evaluations offer little actionable information for model developers, because the interactions between the resolved dynamics and parameterized physics that produce precipitation occur at the native gridscale and timestep. We introduce a set of diagnostics (ASoP1) to compare the spatial and temporal scales of precipitation across GCMs and observations, which can be applied to data ranging from the gridscale and timestep to regional and sub-monthly averages. ASoP1 measures the spectrum of precipitation intensity, temporal variability as a function of intensity, and spatial and temporal coherence. When applied to timestep, gridscale tropical precipitation from ten GCMs, the diagnostics reveal that far from the "dreary" persistent light rainfall implied by daily mean data, most models produce a broad range of timestep intensities that span 1-100 mm/day. Models show widely varying spatial and temporal scales of timestep precipitation. Several GCMs show concerning quasi-random behavior that may influence alter the spectrum of atmospheric waves. Averaging precipitation to a common spatial (~600 km) or temporal (3-hr) resolution substantially reduces variability among models, demonstrating that averaging hides a wealth of information about intrinsic model behavior. When compared against satellite-derived analyses at these scales, all models produce features that are too large and too persistent

Connecting spatial and temporal scales of tropical precipitation in observations and the MetUM-GA6

This study analyses tropical rainfall variability, on a range of temporal and spatial scales, in a set of parallel Met Office Unified Model (MetUM) simulations at a range of horizontal resolutions, compared with two satellite-derived rainfall datasets. We focus on the shorter scales i.e. from the native grid and time-step of the model through sub-daily to seasonal, since previous studies have paid relatively little attention to sub-daily rainfall variability and how this feeds through to longer scales. We find that the behaviour of the deep convection parametrization in this model on the native grid and time-step is largely independent of the grid-box size and time-step length over which it operates. There is also little difference in the rainfall variability on larger/longer spatial/temporal scales. Tropical convection in the model on the native grid/time-step is spatially and temporally intermittent, producing very large rainfall amounts interspersed with grid-boxes/time-steps of little or no rain. In contrast, switching off the deep convection parametrization, albeit at an unrealistic resolution for resolving tropical convection, results in very persistent (for limited periods), but very sporadic, rainfall. In both cases, spatial and temporal averaging smoothes out this intermittency. On the ~100 km scale, for oceanic regions, the spectra of 3-hourly and daily mean rainfall in the configurations with parametrized convection agree fairly well with those from satellite-derived rainfall estimates, while at ~10 day timescales the averages are overestimated, indicating a lack of intra-seasonal variability. Over tropical land the results are more varied, but the model often underestimates the daily mean rainfall (partly as a result of a poor diurnal cycle) but still lacks variability on intra-seasonal timescales. Ultimately, such work will shed light on how uncertainties in modelling the small/short scale processes relate to uncertainty in climate change projections of rainfall distribution and variability, with a view to reducing such uncertainty through improved modelling of the small/short scale processes

Functional food-related bioactive compounds: effect of sorghum phenolics on cancer cells in vivo and conversion of short- to long-chain omega-3 polyunsaturated fatty acids in duck liver in vivo

Doctor of PhilosophyDepartment of Human NutritionWeiqun WangMany functional food related bioactive compounds have been discovered and draw the attention of scientists. This dissertation focused on sorghum phenolic compounds and omega-3 polyunsaturated fatty acids. Study 1: phenolic agents in plant foods have been associated with chronic disease prevention, especially cancer. However, a direct evidence and the underlying mechanisms are mostly unknown. This study selected 13 sorghum accessions and was aim to investigate: (1) the effect of extracted sorghum phenolics on inhibiting cancer cell growth using hepatocarcinoma HepG2 and colorectal adenocarcinoma Caco-2 cell lines; (2) and the underlying mechanisms regarding cytotoxicity, cell cycle interruption, and apoptosis induction. Treatment of HepG2 and Caco-2 cells with the extracted phenolics at 0-200 M GAE (Gallic acid equivalent) up to 72 hrs resulted in a dose- and time-dependent reduction in cell number. The underlying mechanism of cell growth inhibition was examined by flow cytometry, significant inverse correlations were observed between the decreased cell number and increased cell cycle arrest at G2/M or induced apoptosis cells in both HepG2 and Caco-2 cells. The cytotoxic assay showed that the sorghum phenolic extracts were non-toxic. Although it was less sensitive, a similar inhibitory impact and underlying mechanisms were found in Caco-2 cells. These results indicated for the 1st time that a direct inhibition of either HepG2 or Caco-2 cell growth by phenolic extracts from13 selected sorghum accessions was due to cytostatic and apoptotic but not cytotoxic mechanisms. In addition, these findings suggested that sorghum be a valuable functional food by providing sustainable phenolics for potential cancer prevention. Study 2: omega-3 polyunsaturated fatty acids (ω-3 PUFAs) especially long-chain ω-3 PUFAs, have been associated with potential health benefits in chronic disease prevention. However, the conversion rate from short- to long-chain ω-3 PUFAs is limited in human body. This study was aim to assess the modification of fatty acid profiles as well as investigate the conversion of short- to long-chain ω-3 PUFAs in the liver of Shan Partridge duck after feeding various dietary fats. The experimental diets substituted the basal diet by 2% of flaxseed oil, rapeseed oil, beef tallow, or fish oil, respectively. As expected, the total ω-3 fatty acids and the ratio of total ω-3/ ω-6 significantly increased in both flaxseed and fish oil groups when compared with the control diet. No significant change of total saturated fatty acids or ω-3 fatty acids was found in both rapeseed and beef tallow groups. Short-chain ω-3 α-linolenic acid (ALA) in flaxseed oil-fed group was efficiently converted to long-chain ω-3 docosahexaenoic acid (DHA) in the duck liver. This study showed the fatty acid profiling in the duck liver after various dietary fat consumption, provided insight into a dose response change of ω-3 fatty acids, indicated an efficient conversion of short- to long-chain ω-3 fatty acid, and suggested alternative long-chain ω-3 fatty acid-enriched duck products for human health benefits. In conclusion, the two studies in this dissertation provided a fundamental understanding of anti-cancer activity by sorghum phenolic extracts and the conversion of short- to long-chain ω-3 PUFAs in duck liver, contribute to a long term goal of promoting sorghum and duck as sustainable phenolic and ω-3 PUFAs sources as well as healthy food products for human beings

Consensus on Twenty-First-Century Rainfall Projections in Climate Models More Widespread than Previously Thought

Under global warming, increases in precipitation are expected at high latitudes and near major tropical convergence zones in some seasons, while decreases are expected in many subtropical and midlatitude areas in between. In many other areas there is no consensus among models on the sign of the projected change. This is often assumed to indicate that precipitation projections in these regions are highly uncertain. Here, twenty-first century precipitation projections under the Special Report on Emissions Scenarios (SRES) A1B scenario using 24 World Climate Research Programme (WCRP)/Coupled Model Intercomparison Project phase 3 (CMIP3) climate models are examined. In areas with no consensus on the sign of projected change there are extensive subregions where the projected change is 'very likely' (i.e., probability. 0.90) to be small (relative to, e.g., the size of interannual variability during the late twentieth century) or zero. The statistical significance of and interrelationships between methods used to identify model consensus on projected change in the 2007 Intergovernmental Panel on Climate Change (IPCC) report are examined, and the impact of interdependency among model projections on statistical significance is investigated. Interdependency among projections is shown to be much weaker than interdependency among simulations of climatology. The results show that there ismore widespread consistency among the model projections than one might infer from the 2007 IPCC Fourth Assessment report. This discovery highlights the broader need to identify regions, variables, and phenomena that are expected to be little affected by anthropogenic climate change and to communicate this information to the wider community. This is especially important for projections of climate for the next 1-3 decades. © 2012 American Meteorological Society

ENSO-related rainfall changes over the New Guinea region

The large-scale nature of El Niño-Southern Oscillation (ENSO) impacts on rainfall in the western Pacific region is generally well known but in some regions, where there are relatively few observations and the terrain is mountainous, the details of the impacts are less obvious. Here we analyze rainfall data for the New Guinea region comprising station observations, reanalysis products, and satellite-based estimates in order to better understand some of these details. We find that most gridded products are limited due to their relatively coarse horizontal resolutions that fail to resolve topographic effects. However, the relatively fine resolution Tropical Rainfall Measurement Mission satellite-based product appears to provide reliable estimates and linear correlations between the data and the NINO34 sea surface temperature index provides an insight into the pattern of ENSO rainfall impacts. The first major finding is that the correlation patterns reveal that some highland regions are impacted differently to other surrounding regions, most likely because of the interaction between winds and topography. Second, we find that the association between ENSO and rainfall for stations in the New Ireland/New Britain region tends to be nonlinear, in the sense that warm (El Niño)/cool (La Niña) events cause a decrease in rainfall - the strong 2010-2011 La Niña event being a clear example. Both findings help explain why previous studies have tended not to identify a simple large-scale response of New Guinea rainfall to ENSO. Key Points Patterns of ENSO-related rainfall impacts over New Guinea are complex. Satellite-based rainfall estimates (TRMM)provide details about these impacts. There is evidence of non-linear relationships for some regions. ©2013. American Geophysical Union. All Rights Reserved

Climate projections for southern Australian cool-season rainfall: insights from a downscaling comparison

The projected drying of the extra-tropics under a warmer climate has large implications for natural systems and water security in southern Australia. The downscaling of global climate models can provide insight into regional patterns of rainfall change in the mid-latitudes in the typically wetter cool season. The comparison of statistical and dynamical downscaling model outputs reveals regions of consistent potential added value in the climate-change signal over the 21st century that are largely related to finer resolution. These differences include a stronger and more regionalised rainfall decrease on west coasts in response to a shift in westerly circulation and a different response further from the coast where other influences are important. These patterns have a plausible relationship with topography and regional drivers that are not resolved by coarse global models. However, the comparison of statistical and dynamical downscaling reveals where the method and the configuration of each method makes a difference to the projection. This is an important source of uncertainty for regional rainfall projections. In particular, the simulated change in atmospheric circulation over the century is different in the dynamical downscaling compared to the global climate model inputs, related in part to a different response to patterns of surface warming. The dynamical downscaling places the border between regions with rainfall increase and decrease further north in winter and spring compared to the global climate models and therefore has a different rainfall projection for southeast mainland Australia in winter and for Tasmania in spring

Evaluation of the South Pacific Convergence Zone in IPCC AR4 Climate Model Simulations of the Twentieth Century

Understanding how the South Pacific convergence zone (SPCZ) may change in the future requires the use of global coupled atmosphere-ocean models. It is therefore important to evaluate the ability of such models to realistically simulate the SPCZ. The simulation of the SPCZ in 24 coupled model simulations of the twentieth century is examined. The models and simulations are those used for the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC). The seasonal climatology and interannual variability of the SPCZ is evaluated using observed and model precipitation. Twenty models simulate a distinct SPCZ, while four models merge intertropical convergence zone and SPCZ precipitation. The majority of models simulate an SPCZ with an overly zonal orientation, rather than extending in a diagonal band into the southeast Pacific as observed. Two-thirds of models capture the observed meridional displacement of the SPCZ during El Niño and La Niña events. The four models that use ocean heat flux adjustments simulate a better tropical SPCZ pattern because of a better representation of the Pacific sea surface temperature pattern and absence of cold sea surface temperature biases on the equator. However, the flux-adjusted models do not show greater skill in simulating the interannual variability of the SPCZ. While a small subset of models does not adequately reproduce the climatology or variability of the SPCZ, the majority of models are able to capture the main features of SPCZ climatology and variability, and they can therefore be used with some confidence for future climate projections. © 2011 American Meteorological Society