25 research outputs found

    Multiepoch Detections of the Extended Atmosphere and Transmission Spectra of KELT-9b with a 1.5 m Telescope

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    Irradiated Jovian atmospheres are complex and dynamic and can undergo temporal variations due to the close proximity of their parent stars. Of the Jovian planets that have been cataloged to date, KELT-9b is the hottest gas giant known, with an equilibrium temperature of 4050 K. We probe the temporal variability of transmission spectroscopic signatures from KELT-9b via a set of archival multiyear ground-based transit observations, performed with the TRES facility on the 1.5 m reflector at the Fred Lawrence Whipple Observatory. Our observations confirm past detections of Fe i , Fe ii , and Mg i over multiple epochs, in addition to excess absorption at H α , which is an indicator for ongoing mass loss. From our multiyear data set, the H α light curve consistently deviates from a standard transit and follows a “W” shape that is deeper near ingress and egress and shallower midtransit. To search for and quantify any seasonal variations that may be present, we parameterize a “cometary tail” model to fit for the H α transit. We find no detectable variations between the different observed epochs. Though a “cometary tail” describes the H α flux variations well, we note that such a scenario requires a high density of neutral hydrogen in the n = 2 excited state far beyond the planetary atmosphere. Other scenarios, such as center-to-limb variations larger than that expected from 1D atmosphere models, may also contribute to the observed H α transit shape. These multiepoch observations highlight the capabilities of small telescopes to provide temporal monitoring of the dynamics of exoplanet atmospheres

    Wet season rainfall onset and flash drought: The case of the northern Australian wet season

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    In this paper, we report on the frequency of false onsets of wet season rainfall in the case of the Northern Australian wet season and investigate the role of large-scale tropical climate processes such as the El Nino–Southern Oscillation, Indian Ocean Dipole (IOD) and Madden–Julian Oscillation. A false onset occurs when a wet season rainfall onset criterion is met, but follow-up rainfall is not received for weeks or months later. Our analysis of wet season rainfall data from 1950 through 2020 shows a false onset occurs, on average, between 20 and 30% of wet seasons across all of northern Australia. This increases at a regional and local level such as at Darwin, the Northern Territory (NT), and parts of Queensland's north coast to over 50%. Seasonal climate influences, such as a La Niña pattern and a negative IOD that typically expedite the wet season rainfall onset, also increase the likelihood of a false onset over northern Australia. Our analysis also finds that periods of false onsets can sometimes, but not always, coincide with periods of rapid soil moisture depletion. The false rainfall onsets that develop into flash drought can be potentially disruptive and costly and are of potential significance for agriculture and fire management in northern Australia, and in other monsoonal climates that also typically experience a slow build-up to the seasonal monsoon. In conclusion, effective rainfall indicates that many seasons experience ‘false onsets’ with dry conditions after early rainfall. We propose that false onsets are a physical characteristic of the climate of northern Australia which occurs with relatively high frequency. In addition, these false onsets may sometimes co-occur with a flash drought

    The Influence of Interannual and Decadal Indo-Pacific Sea Surface Temperature Variability on Australian Monsoon Rainfall

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    Monsoonal rainfall in northern Australia (AUMR) varies substantially on interannual, decadal, and longer time scales, profoundly impacting natural systems and agricultural communities. Some of this variability arises in response to sea surface temperature (SST) variability in the Indo-Pacific linked to both El Niño–Southern Oscillation (ENSO) and the interdecadal Pacific oscillation (IPO). Here we use observations to investigate unresolved issues regarding the influence of the IPO and ENSO on AUMR. Specifically, we show that during negative IPO phases, central Pacific (CP) El Niño events are associated with below-average rainfall over northeast Australia, an anomalous anticyclonic pattern to the northwest of Australia, and eastward moisture advection toward the date line. In contrast, CP La Niña events (distinct from eastern Pacific La Niña events) during negative IPO phases drive significantly wet conditions over much of northern Australia, a strengthened Walker circulation, and large-scale moisture flux convergence. During positive IPO phases, the impact of CP El Niño and CP La Niña events on AUMR is weaker. The influence of central Pacific SSTs on AUMR has been stronger during the recent (post-1999) negative IPO phase. The extent to which this strengthening is associated with climate change or merely natural internal variability is not known

    Formalizing Trust in Historical Weather Data

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    Historical instrumental weather observations are vital to understanding past, present, and future climate variability and change. However, the quantity of historical weather observations to be rescued globally far exceeds the resources available to do the rescuing. Which observations should be prioritized? Here we formalize guidelines help make decisions on rescuing historical data. Rather than wait until resource-intensive digitization is done to assess the data’s value, insights can be gleaned from the context in which the observations were made and the history of the ob-servers. Further insights can be gained from the transcription platforms used and the transcribers involved in the data rescue process, without which even the best historical observations can be mishandled. We use the concept of trust to help integrate and formalize the guidelines across the life cycle of data rescue, from the original observation source to the transcribed data element. Five cases of citizen science-based historical data rescue, two from Canada and three from Australia, guide us in constructing a trust checklist. The checklist assembles information from the original observers and their observations to the current transcribers and transcription approaches they use. Nineteen elements are generated to help future data rescue projects answer the question of whether resources should be devoted to rescuing historical meteorological material under consideration

    Toowoomba Region Design : Warm Temperate Climate Building Design Guidelines

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    These guidelines help homeowners, commercial property owners andrenters, in rural and central Toowoomba, to design new buildings thatcomplement our climate. Ours is warm and temperate — a climate unlikeany other in Southeast Queensland. Good design celebrates these conditionsas well as our rich history and distinctive character. Here, you’ll also finddesign tips to improve energy efficiency and prepare your new building forchanging climate conditions. Toowoomba Regional Council is committedto a sustainable built environment that is designed for our unique climateand celebrates our legacy as the ‘Garden City’. Council has invested in theseguidelines to promote great design outcomes for the Toowoomba Region.The Warm Temperate Climate Building Design Guidelines is the first outputfrom the Toowoomba Region Design series

    Northern Australia Climate Program: supporting adaptation in rangeland grazing systems through more targeted climate forecasts, improved drought information and an innovative extension program

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    The Northern Australia Climate Program (NACP) is a fully integrated research, development and extension (RDandE) program operating across extensive pastoral regions of northern Australia. The NACP aims to improve existing climate models and forecast tools, develop new products to meet user needs and build the capacity of rangeland producers to manage the challenges posed by droughts (or failed wet seasons) and climate variability. Climate information gaps identified through earlier surveys of graziers and communities in rural and remote Australia informed the design of the research component of the NACP, which aims to address the low and variable accuracy of seasonal climate forecasts in many regions, the need for proof of value of forecasts and relevance of existing forecast systems and technologies, and perceived lack of effective support from climate experts for the use of climate resources and technologies in agricultural decision making. The development and extension components of the program aim to improve climate literacy and the use of climate information. Building on the research program, they deliver a climate service that provides local extension and technical support, with a focus on building trust in climate information through locally sourced, industry connected NACP trained and supported extension advisers called Climate Mates. Two-way information flow between decision makers and researchers, facilitated by the Climate Mates, ensures that forecasts and decision- A nd discussion-support tools developed through the program are regionally relevant and targeted to the needs of end users. Monitoring and evaluation of the program indicates that this approach is contributing to positive outcomes in terms of awareness and knowledge of climate forecasting and products, and their adoption and use in decision making (i.e. practice change). In the longer term, the Climate Mates have potential for enduring impact beyond the program, leaving a knowledgeable and trusted climate resource across regional northern Australia

    Methodology for producing the Drought Monitor

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    Drought is one of the most severe natural disasters Australia faces, inflicting serious impacts on the agricultural industry. An Australia-wide drought monitor has been developed to provide detailed and timely data regarding drought conditions that will aid producers and policy makers alike. The Drought Monitor development was an integral part of the Northern Australia Climate Program (NACP), a major partnership between Meat & Livestock Australia, the Queensland Government and the University of Southern Queensland. This document explains the methodology used to produce the monthly Drought Monitor

    Insights into the value of seasonal climate forecasts to agriculture

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    Seasonal climate forecasts (forecasts) aim to reduce climate-related productivity risk by helping farmers make decisions that minimise losses in poor years and maximise profits in good years. Most Australian forecast valuations have focused on fertiliser decisions to wheat operations, and few assessments have evaluated the benefit of incremental improvements of forecast skill. These gaps have limited our understanding of forecast value to the broader agriculture sector and the benefit of investments to improve forecast skill. To address these gaps, we consistently assessed forecast value for seven Australian case studies (southern grains, northern grains, southern beef, northern beef, lamb, cotton, and sugar). We implemented a three-stage methodology which consisted of engagement with industry practitioners; modelling production under different climatic and environmental conditions; and economic modelling to evaluate forecast value for eleven levels of forecast skill. Our results show that forecast value was often low and highly variable. Value was found to vary based on forecast attributes (forecast skill, resolution and state), industry application and prevailing conditions (environmental and market). This is the first Australian valuation study where the same methodological approach was applied across multiple industries, incremental improvements in skill were valued, and prevailing conditions were explicitly evaluated for impact on value
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