Estimating groundwater storage changes in the Mississippi River basin (USA) using GRACE

Based on satellite observations of Earth’s time variable gravity field from the Gravity Recovery and Climate Experiment (GRACE), it is possible to derive variations in terrestrial water storage, which includes groundwater, soil moisture, and snow. Given auxiliary information on the latter two, one can estimate groundwater storage variations. GRACE may be the only hope for groundwater depletion assessments in data-poor regions of the world. In this study, soil moisture and snow were simulated by the Global Land Data Assimilation System (GLDAS) and used to isolate groundwater storage anomalies from GRACE water storage data for the Mississippi River basin and its four major sub-basins. Results were evaluated using water level records from 58 wells set in the unconfined aquifers of the basin. Uncertainty in the technique was also assessed. The GRACE-GLDAS estimates compared favorably with the well based time series for the Mississippi River basin and the two sub-basins that are larger than 900,000 km². The technique performed poorly for the two sub-basins that have areas of approximately 500,000 km². Continuing enhancement of the GRACE processing methods is likely to improve the skill of the technique in the future, while also increasing the temporal resolution.     

Comparison of observed gale radius statistics

Summary Forecasts of tropical cyclone track and intensity have long been used to characterize the evolution and expected threat from a tropical storm. However, in recent years, recognition of the contributions of subtropical cyclogenesis to tropical storm formation and the process of extratropical transition to latter stages of the once-tropical storm’s lifecycle have raised awareness about the importance of storm structure. Indeed, the structure of a cyclone determines the distribution and intensity of the significant weather associated with that storm. In this study, storm structure is characterized in terms of significant wind radii. The radii of tropical storm, damaging, and hurricane-force winds, as well as the radius of maximum winds are all analyzed. These wind radii are objectively derived from the H^*Wind surface wind analysis system. Initially, six years of these data are examined for consistency with previous studies. Having ascertained that the H^*Wind radii are realistic, detailed comparisons are performed between the H^*Wind and NHC Best Track wind radii for two years (2004 and 2005) of North Atlantic tropical storm and hurricane cases. This intercomparison reveals an unexpected bias: the H^*Wind radii are consistently larger than the NHC Best Track for all but the smallest and least intense storms. Further examination of the objectively-determined H^*Wind tropical storm force wind radius data compared to subjectively-determined radii for the same storm times demonstrates that the objective wind radii are underestimating the extent of the tropical storm force wind area. Since the objective H^*Wind radii are large compared to the NHC Best Track – and yet underestimate the area of tropical storm force winds – this argues for further examination of the methods used to ascertain these significant wind radii.     

A review of acid sulfate soil impacts, actions and policies that impact on water quality in Great Barrier Reef catchments, including a case study on remediation at East Trinity

An estimated 666,000 ha of acid sulfate soils (ASS) occur within the Great Barrier Reef (GBR) catchments of Queensland, Australia. Extensive areas have been drained causing acidification, metal contamination, deoxygenation and iron precipitation in reef receiving waters. The close proximity of ASS to reef waters makes them a substantial threat to water quality. Another important issue linked with ASS is their release of soluble iron, which is known to stimulate nuisance marine algal blooms, in particular Lyngbya majuscula. Known blooms of the cyanobacteria in reef waters have been confirmed at Shoalwater Bay, Corio Bay, the Whitsunday area and Hinchinbrook Channel. Acid sulfate soils are intimately related to coastal wetland landscapes. Where landscapes containing ASS have been disturbed (such as for agriculture, aquaculture, marinas, etc.) the biodiversity of adjacent wetlands can be adversely affected. However, there is no clear knowledge of the real extent of the so-called "hotspot" ASS areas that occur within the GBR catchments. Management of ASS in reef catchments has benefited from the implementation of the Queensland Acid Sulfate Soils Management Strategy through policy development, mapping, training programs, an advisory service, research and community participation. However, major gaps remain in mapping the extent and nature of ASS. Areas of significant acidification (i.e. hotspots) need to be identified and policies developed for their remediation. Research has a critical role to play in understanding ASS risk and finding solutions, to prevent the adverse impacts that may be caused by ASS disturbance. A case study is presented of the East Trinity site near Cairns, a failed sugar cane development that episodically discharges large amounts of acid into Trinity Inlet, resulting in periodic fish kills. Details are presented of scientific investigations, and a lime-assisted tidal exchange strategy that are being undertaken to remediate a serious ASS problem.     

Hydration of eclogite, Pam Peninsula, New Caledonia

Garnet glaucophanite and greenschist facies assemblages were formed by the recrystallization of barroisite-bearing eclogite facies metabasites in northern New Caledonia. The mineralogical evolution can be modelled by calculated P–T and P–X _H2O diagrams for appropriate bulk rock compositions in the model system CaO–Na₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O. The eclogites, having developed in a clockwise P–T path that reached P ≈19 kbar and T  ≈590 °C, underwent decompression with the consumption of free H₂O as the volume of hydrous minerals increased. Eclogite is preserved in domains that experienced no fluid influx following the loss of this fluid. Garnet glaucophanite formed at P ≈16 kbar during semi-pervasive fluid influx. Fluid influx, after further isothermal decompression, was focused in shear zones, and resulted in chlorite–albite-bearing greenschist facies mineral assemblages that reflect P ≈9 kbar.     

A new assessment of the mid-1970s abrupt atmospheric temperature change in the NCEP/NCAR reanalysis and associated solar forcing implications

Based on the reanalysis data from the National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP?CNCAR) and solar radio irradiance (SRI) at 10.7?cm wavelength obtained from the National Oceanic and Atmospheric Administration??s Space Weather Prediction center, the abrupt temperature change in the mid-1970s and its possible association with solar irradiance variability have been investigated. The results show that a discontinuous abrupt change in the mid-1970s in the NCEP?CNCAR reanalysis was observed in the tropical lower and middle stratospheric temperature. The shift in temperature and its timing agrees well with the climate regime shift discovered in the radiosonde observations (HadAT), European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40), and many previous studies and manifests a statistically significant change at the 95% confidence level. A corresponding change of the SRI was identified in the mid 1970s although the statistical t test value is not very high. The running correlation with a 21-year moving time window exhibits a strong positive correlation between the solar cycle and atmospheric temperature in the tropical stratosphere during the period of 1948?C2007. However, the positive correlation was broken at the time of the mid-1970s abrupt change and two peak positive correlation points were observed in 1972 and 1982, respectively.     

Possible solar forcing of interannual and decadal stratospheric planetary wave variability in the northern hemisphere: An observational study

The variability of stratospheric planetary waves and their possible connection with the 11-year solar cycle forcing have been investigated using annual-mean temperatures for the period of 1958–2001 derived from two reanalysis data sets. The significant planetary waves (wavenumbers 1–3) can be identified in the northern mid-high latitudes (55–75°N) in the stratosphere using this data. Comparisons with satellite-retrieved products from the Microwave Sounding Unit (MSU) confirm the significant planetary wave variability seen in the reanalyses. A planetary wave amplitude index (PWAI) is defined to indicate the strength of the stratospheric planetary waves. The PWAI is derived from Fourier analysis of the temperature field for wavenumbers 1–3 and averaged over 55–75°N latitude and the 70–20 hPa layers. The results include two meaningful inter-annual oscillations (2- and 8-year) and one decadal trend (16-year) that was derived from wavelet analysis. The stratospheric temperature structure of the wave amplitudes appear associated with the Arctic Oscillation (AO) which explicitly changed with the PWAI. The temperature gradients between the polar and mid-high latitudes show opposite tendencies between the top-10 strong and weak wave regimes.The variation of the planetary wave amplitude appears closely related to the solar forcing during the recent four solar cycles (20–23). The peak of the 2-year oscillation occurs synchronously with solar minimum, and is consistent with the negative correlation between the PWAI and the observed solar UV irradiance. The UV changes between the maxima and minima of the 11-year solar cycle impact the temperature structure in the middle-lower stratosphere in the mid-high latitudes and hence influence the planetary waves. During solar maximum, the dominant influence appears to be exerted through changes in static stability, leading to a reduction in planetary wave amplitude. During solar minimum, the dominant influence appears to be exerted through changes in the meridional temperature gradient and vertical wind shear, leading to an enhancement of planetary wave amplitude.     

Influence of gusset plate connections and braces on the seismic performance of X‐braced frames

Braced frames are one of the most economical and efficient seismic resisting systems yet few full‐scale tests exist. A recent research project, funded by the National Science Foundation (NSF), seeks to fill this gap by developing high‐resolution data of improved seismic resisting braced frame systems. As part of this study, three full‐scale, two‐story concentrically braced frames in the multi‐story X‐braced configuration were tested. The experiments examined all levels of system performance, up to and including fracture of multiple braces in the frame. Although the past research suggests very limited ductility of SCBFs with HSS rectangular tubes for braces recent one‐story tests with improved gusset plate designs suggest otherwise. The frame designs used AISC SCBF standards and two of these frames designs also employed new concepts developed for gusset plate connection design. Two specimens employed HSS rectangular tubes for bracing, and the third specimen had wide flange braces. Two specimens had rectangular gusset plates and the third had tapered gusset plates. The HSS tubes achieved multiple cycles at maximum story drift ratios greater than 2% before brace fracture with the improved connection design methods. Frames with wide flange braces achieved multiple cycles at maximum story drift greater than 2.5% before brace fracture. Inelastic deformation was distributed between the two stories with the multi‐story X‐brace configuration and top story loading. Copyright © 2010 John Wiley & Sons, Ltd.