Air-sea Coupling During the Tropical Cyclones in the Indian Ocean: A Case Study Using Satellite Observations

In the years 1999 and 2001, three intense tropical cyclones formed over the northern Indian Ocean—two over the Bay of Bengal during 15–19 and 25–29 October, 1999 and one over the Arabian Sea during 21–28 May, 2001. We examined the thermal, salinity and circulation responses at the sea surface due to these severe cyclones in order to understand the air-sea coupling using data from satellite measurements and model simulations. It is found that the Sea Surface Temperature (SST) cooled by about 0.5 °–0.8 °C in the Bay of Bengal and 2 °C in the Arabian Sea. In the Bay of Bengal, this cooling took place beneath the cyclone center whereas in the Arabian Sea, the cooling occurred behind the cyclone only a few days later. This contrasting oceanic response resulted mainly from the salinity stratification in the Bay of Bengal and thermal stratification in the Arabian Sea and the associated mixing processes. In particular, the cyclones moved over the region of low salinity and smaller mixed layer depth with a distinct mixed layer deepening to the left side of the cyclone track. It is envisaged that daily satellite estimates of SST and Sea Surface Salinity (SSS) using Outgoing Longwave Radiation (OLR) and model simulated mixed layer depth would be useful for the study of tropical cyclones and prediction of their path over the northern Indian Ocean.     

Evaluation of past,present and future tools for radar-based flash-flood prediction in the USA

Abstract

The societal impacts of flash floods are more significant than any other weather-related hazard. They are often manifested in the form of damage to infrastructure, flooding of roadways and bridges, creating deadly hazards to motorists and inundation of crops and pasture. Some of these hazards can be anticipated and thus mitigated given effective warning systems. This study describes the tools proposed over recent decades in the USA to predict flash flooding and evaluates them using a common observational data set. Design recommendations for flash-flood forecasting systems are provided, taking into account today's availability of high-resolution rainfall data at scales commensurate with flash flooding, their archives, spatial data sets to describe physiographic properties, and ever-increasing computational resources.

Editor D. Koutsoyiannis; Guest editor R.J. Moore

Citation Gourley, J.J., Flamig, Z.L., Hong, Y., and Howard, K.W., 2014. Evaluation of past, present and future tools for radar-based flash-flood prediction in the USA. Hydrological Sciences Journal, 59 (7), 1377–1389. http://dx.doi.org/10.1080/02626667.2014.919391     

Identifying and Quantifying Disjunctions at Multiple Taxonomic Levels in Western Hemisphere Mammals

I surveyed more than 1,700 Western Hemisphere mammal species ranges to identify, quantify, and examine patterns of disjunction at multiple taxonomic levels. Species that had disjunct populations (isolated by at least 500 km from other parts of the species range) were further analyzed using novel measures of disjunction by determining the distance to the disjunction and the relative area of disjunctions compared to the primary range area. Disjunction at this scale is rare (6.4 percent) in all terrestrial mammals but more common in bats (14.6 percent) than nonvolant mammals. Disjunctions are concentrated in six families, specifically Molossidae (31.5 percent disjunct), Didelphidae (24.7 percent disjunct), Felidae (28.6 percent disjunct), Vespertilionidae (15.3 percent disjunct), Emballonuridae (10.5 percent disjunct), and Phyllostomidae (10.4 percent disjunct). Geographically, 85 percent of disjunct mammal species have ranges that occur entirely or partially in South America. Geographic information systems analysis of species range maps is capable of identifying disjunct species and evaluating the severity of disjunctions. When compiled at the family level, these data suggest that species in certain families are more susceptible to disjunction. In some cases (e.g., species ranges separated by the Amazon rainforest), species-level data offer insight into the causes of disjunction. Study of species identified as disjunct in this study can inform conservation efforts by providing an opportunity to determine the characteristics that enable them to survive as isolated populations.     

Antiphase hydrogen and oxygen isotope periodicity in chert nodules

Oxygen and hydrogen isotope analyses were made of Jurassic-age chert nodules from the Holy Cross Mountains, SE Poland, along radial transects at high spatial resolution. There is a radial “sigmoidal” periodicity for both isotope ratios, but the two are out of phase, with high δD values corresponding to low δ¹⁸O values. Periodicity for a 100- to 120-mm diameter nodule is approximately 16 mm, increasing slightly toward the rim, with amplitudes approaching 20 and 3.0‰ for hydrogen and oxygen, respectively. The combined hydrogen-oxygen isotope data for one nodule fall on a published curve for chert forming in equilibrium with seawater (Knauth and Epstein, 1976); the range of delta values corresponds to temperature variations of ∼10°C. Data for a second chert fall on a subparallel δD-δ¹⁸O line with δD values that are almost 50‰ lower. The δD-δ¹⁸O patterns for the nodules cannot be explained by periodic mixing of meteoric and ocean water because the hydrogen and oxygen isotope data are out of phase. Two possible explanations for the antiphase periodicity are (a) cyclical temperature variations, perhaps related to an unstable convection system (e.g., Bolton et al., 1999), and (b) self-organizing catalytic precipitation (e.g., Wang and Merino, 1990). The systematic isotopic variations are difficult to explain by diagenesis and strongly suggest that primary isotopic compositions are preserved. The isotopic data provide important information on the thermal history of the sedimentary basin, if temperature variations are the cause of the isotopic periodicity.     

A pilot survey for KX QSOs in the UKIDSS Ultra Deep Survey Field

We have undertaken a pilot survey for faint quasi-stellar objects (QSOs) in the UKIRT Infrared Deep Survey (UKIDSS) Ultra Deep Survey (UDS) Field using the KX selection technique. These observations exploit the very deep near-infrared and optical imaging of this field from United Kingdom Infrared Telescope (UKIRT) and Subaru to select candidate QSOs based on their VJK colours and morphologies. We determined redshifts for 426 candidates using the AAOmega spectrograph on the Anglo-Australian Telescope in service time. We identify 17 QSOs  ( M _B ≲−23)  in this pilot survey at z = 1.57–3.29. We combine our sample with an X-ray-selected sample of QSOs in the same field (a large fraction of which also comply with our KX selection) to constrain the surface density of QSOs with K ≤ 20, deriving limits on the likely surface density of 85–150 deg⁻². We use the good image quality available from our near-infrared imaging to detect a spatially extended component of the QSO light which probably represents the host galaxies. We also use our sample to investigate routes to improve the selection of KX QSOs at faint limits in the face of the significant contamination by compact, foreground galaxies. The brightest examples from our combined QSO sample will be used in conjunction with a large Very Large Telescope VIMOS spectroscopic survey of high-redshift galaxies in this region to study the structures inhabited by gas, galaxies and growing supermassive black holes at high redshifts in the UKIDSS UDS.     

Apparent stable isotope heterogeneities in gangue carbonates of the Mississippi Valley-type Zn-Pb deposit of San Vicente,central Peru

The aim of the present communication is to emphasize that some variations of the measured ¹³C and ¹⁸O values are apparent, and due to analytical interferences caused by the presence of sulfur and organosulfur compounds in the analyzed carbonates. This is particularly relevant for isotopic studies on carbonate-hosted mineral deposits, where the nearly ubiquitous association of the host carbonates with organic matter and sulfides can certainly affect the metallogenetic interpretations. In this work two methods were used to overcome the disturbing effects of sulfides and organic matter: (1) sample pretreatment following the method proposed by Charef and Sheppard (1984), combining the oxidation of organic matter with sodium hypochlorite and trapping of the sulfur species with silver phosphate; and (2) laser-based microprobe extraction. Apparent isotopic variations in sparry dolomite from a single hand sample of zebra ore from the MVT Zn-Pb deposit, San Vicente, central Peru, are as large as 6 ¹³C and 4 ¹⁸O. These variations are reduced to several tenths of a per mil when the samples are pretreated. A careful examination of the effects of treatment with NaOCl and/or Ag₃PO₄ in relation to the concentration of sulfide inclusions indicates that the main disturbing effects for ¹³C values are the presence of sulfur species and organic matter, whereas the ¹⁸O values are mainly affected by the presence of sulfides. Fine- and medium-grained replacement carbonates from MVT and other sediment-hosted base metal deposits are potentially the most affected during isotope analysis, due to the common presence of organic matter and sulfides. Using in situ laser microprobe techniques, it is possible to determine isotopic variations at a sub-millimeter scale. Our results show that laser extraction analysis allows a more precise sampling of the carbonate minerals, and minimizes contamination of the sample with sulfides and to some extent with intergrown organic matter. However, there is an isotopic shift associated with the laser extraction technique, of the order of 0.5–1 for ¹³C and ¹⁸O values.     

Optimal Decision Making Algorithm for Managed Aquifer Recharge and Recovery Operation Using Near Real‐Time Data: Benchtop Scale Laboratory Demonstration

Aquifers show troubling signs of irreversible depletion as climate change, population growth, and urbanization lead to reduced natural recharge rates and overuse. One strategy to sustain the groundwater supply is to recharge aquifers artificially with reclaimed water or stormwater via managed aquifer recharge and recovery (MAR) systems. Unfortunately, MAR systems remain wrought with operational challenges related to the quality and quantity of recharged and recovered water stemming from a lack of data‐driven, real‐time control. This paper presents a laboratory scale proof‐of‐concept study that demonstrates the capability of a real‐time, simulation‐based control optimization algorithm to ease the operational challenges of MAR systems. Central to the algorithm is a model that simulates water flow and transport of dissolved chemical constituents in the aquifer. The algorithm compensates for model parameter uncertainty by continually collecting data from a network of sensors embedded within the aquifer. At regular intervals the sensor data is fed into an inversion algorithm, which calibrates the uncertain parameters and generates the initial conditions required to model the system behavior. The calibrated model is then incorporated into a genetic algorithm that executes simulations and determines the best management action, for example, the optimal pumping policy for current aquifer management goals. Experiments to calibrate and validate the simulation‐optimization algorithm were conducted in a small two‐dimensional synthetic aquifer under both homogeneous and heterogeneous packing configurations. Results from initial experiments validated the feasibility of the approach and suggested that our system could improve the operation of full‐scale MAR facilities.     

Evaluation of turbulent Prandtl (Schmidt) number parameterizations for stably stratified environmental flows

In this study, we evaluate four different parameterizations of the turbulent Prandtl (Schmidt) number Pr_t = ν_t/Γ_t where ν_t is the eddy viscosity and Γ_t is the scalar eddy diffusivity, for stably stratified flows. All four formulations of Pr_t are strictly functions of the gradient Richardson number Ri, which provides a measure of the strength of the stratification. A zero-equation (i.e. no extra transport equations are required) turbulence model for ν_t in a one-dimensional, turbulent channel flow is considered to evaluate the behavior of the different formulations of Pr_t. Both uni-directional and oscillatory flows are considered to simulate conditions representative of practical flow problems such as atmospheric boundary layer flows and tidally driven estuarine flows, to quantify the behavior of each of the four formulations of Pr_t. We perform model-to-model comparisons to highlight which of the models of Pr_t allow for a higher rate of turbulent mixing and which models significantly inhibit turbulent mixing in the presence of buoyancy forces resulting from linear (continuous) stratification as well as two-layer stratification. The basis underlying the formulation of each model in conjunction with the simulation results are used to emphasize the considerable variability in the different formulations and the importance of choosing an appropriate parameterization of Pr_t given a model for ν_t in stably stratified flows.     

40Ar/39Ar Geochronology and stable isotope geochemistry of Late-Hercynian intrusions from north-eastern Iberia with implications for argon loss in K-feldspar

The cooling history of Hercynian calc-alkalic, post-kinematic plutonic intrusions of the Montnegre massif (NE Spain) has been determined by ⁴⁰Ar/³⁹Ar analysis of two hornblendes, four biotites and eight K-feldspars (Kfs). The hornblendes have ⁴⁰Ar/³⁹Ar total fusion ages of 291Dž Ma and define the magmatic cooling of the basic and oldest structural intrusions. The biotites from the acid and intermediate rocks have ⁴⁰Ar/³⁹Ar plateau ages of 285Dž Ma, which date cooling of the intrusions through argon closure in biotite. The ⁴⁰Ar/³⁹Ar ages of the K-feldspars vary widely, ranging from 276-191 Ma. A correlation between K-feldspar ⁴⁰Ar/³⁹Ar total fusion age and several other features such as structural state, microstructures indicated by obliquity and, to some degree, optically visible perthites, is consistent with post-crystallisation partial argon loss in the K-feldspars. The 'D values of the biotites also correlate with age and chlorite contents, but this is not so for the '¹⁸O values of either feldspar or quartz. We infer that most microtextural changes occurred during cooling of the batholith, but a possibly Mesozoic, late disturbing hydrothermal event of weak intensity and with only minor fluid circulation must have occurred. This event provoked significant argon loss in the most structurally complex K-feldspars and is recorded in the hydrogen, but not oxygen, isotope data.