Seminars - Melbourne
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CAWCR SEMINARS 2013
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The venue is the seminar room (Floor 9, east side) at 700 Collins Street, Docklands
Seminars are run typically with duration of 30 to 45 minutes + questions. Dates and times are shown. If you are a vistor to the Bureau, you need to register at reception in the foyer.
For further details contact the seminar coordinators
ABSTRACTS
Dr. Emilie Dassie Lamont-Doherty Earth Observatory, Columbia University
TBA
Yoshimitsu Chikamoto International Pacific Research Center, University of Hawai‘i, USA
The potential decadal predictability of land hydrological variables in North America is examined using a 900-year-long pre-industrial control simulation, conducted with the NCAR Community Earth System Model (CESM) version 1.0.3. The leading modes of simulated North American precipitation and soil water storage are characterized by qualitatively similar meridional seesaw patterns. Whereas the corresponding precipitation variability can be described as a white noise stochastic process, power spectra of vertically integrated soil moisture exhibit significant redness on timescales of years to decades. This suggests that the predictability of soil water storage arises from the integration of precipitation variability. As a result, damped persistence hindcasts, following a 1st order Markov process, are skillful with lead times of up to several years. This skill estimate is consistent with ensemble hindcasts conducted with the CESM for various initial conditions. This predictive skill of moisture variations strongly depends on the soil depth, in particular for the Northern United States. Our control simulation suggests that decadal variations in total water storage affect wildfire frequency. These results demonstrate the feasibility decadal predictions of soil water storage in the Western US with potential benets for risk management related to water resources, forestry, and agriculture, which would also be applicable to Australian climate.
Matthew Wheeler and Hongyan Zhu CAWCR
TBA
Jonathan Overpeck University of Arizona
TBA
Toshiyuki Kurino Meteorological Satellite Center, Japanese Meteorological Agency
In 2014 the Japanese Meteorological Agency will launch its next generation geostationary satellite Himawari-8. The imager onboard is the Advanced Himawari Imager (AHI). This imager will provide a significant step change to the Australian region in terms of data acquisition, processing and archiving. The AHI will increase the Bureau’s capability for weather forecasting. The AHI improves over the current generation imager in three key areas: number of channels, spatial resolution and frequency of delivery. More channels signify an increase in the types of atmospheric phenomena that can be investigated and measured. The spatial resolution will increase by a factor of four and the temporal resolution by a factor of six. These will increase the likelihood of identifying changes in weather patterns and in the predictive capability of forecasters.
Julie Arblaster CAWCR
The climate of the Southern Hemisphere has undergone significant changes over recent decades with more changes expected under future emission scenarios. However, while temperature increases are robust across models there is more uncertainty around changes in rainfall, atmospheric circulation and extremes, all of which have a large impact on human society and ecosystems. This talk will discuss the relative importance of various drivers of Southern Hemisphere climate change, including sea surface temperatures (which may or may not be anthropogenically forced), greenhouse gases and stratospheric ozone. A hierarchy of model experiments are utilised, from idealised experiments to multimodel datasets, with a focus on changes in the SH mid-latitude jet and Southern Annular Mode. Insights are gained by exploring both the consistencies and spread across the model results.
Beth Ebert CAWCR
Verification of meteorological and oceanographic forecasts is essential for monitoring their accuracy, understanding their errors, and making improvements in forecasting systems. Recent years have seen a growing interest in new approaches for forecast verification, as evidenced by the rising number of publications on newly developed verification techniques. This has partly been driven by the need for new diagnostic methods to understand the strengths and limitations of high resolution of numerical models. Ensemble prediction has become widespread, calling for ways to assess not only their spread but also the probabilistic and scenario products that can be generated from ensembles. Prediction of extreme weather, while always of interest, has taken on new importance in light of our improved understanding of weather and climate variability and change, requiring verification methods that are targeted to extreme and rare events. Forecasting applications based on meteorological predictions, for example, continuous streamflow, wildfire behaviour, crop yields, and renewable energy prediction, call for new ways of evaluating these forecasts that are more relevant to the downstream application. This talk will review recent progress in methods for evaluating NWP forecasts and products making use of NWP output. There are many interesting challenges, including the improvement of methods to verify high resolution ensemble forecasts, seamless predictions spanning multiple spatial and temporal scales, and multivariate forecasts. More work is also needed to make best use of new observations, investigate issues and opportunities linking data assimilation and verification, and develop better and more intuitive forecast verification products for end-users.
Dusan Zrnic National Severe Storms Laboratory, NOAA Note: This is a 1.5 hour seminar followed by a 30 minute Q&A session.
Dusan Zrnic has visited us for a period of two weeks to help with our Ground-based Remote Sensing (GRS) strategic planning; more specifically, he will be assisting us with assessing our radar network and will be presenting comparisons with the NOAA and other international radar networks. This seminar is to allow Dusan to present his findings, and recommend changes that will be required to take us into the future and help achieve 'best practice' in the radar network arena.
Dusan Zrnic National Severe Storms Laboratory, NOAA Note: This is a 1 hour seminar followed by a 30 minute workshop and open forum. Radar Data Quality and Maintenance: Quality data does not guarantee quality information, but quality information is impossible without quality data
Traditionally data quality referred to statistical errors of estimates; however, the meaning has broadened to include almost any data feature that obscures proper interpretation of meteorological phenomena. Taking this broad definition as a backdrop the data flow in the radar system is examined and pointed are places where errors can occur and where these can be corrected. It is argued that elimination of the error’s source is the best strategy, otherwise mitigation is most effective closest to the source of error. The discussion focuses on ways data quality is maintained in the WSR-88D network. Threshold on the signal to noise ratios is the standard procedure and radial by radial noise measurements is being tested. Examples of this and other interferences are illustrated. The network has robust handling of ambiguities in range and velocity. These are reviewed as well as some aspects of radar calibration. Current and proposed ground clutter recognition/filtering procedure is also discussed. Continuous monitoring the system using returns off ground clutter and Sun is suggested. Oversampling in range is briefly mentioned because it can reduce statistical errors in estimates and is planed for inclusion in the near future.
Dusan Zrnic National Severe Storms Laboratory, NOAA Note: This is a 1 hour seminar followed by a 30 minute workshop and open forum. Radar and other Remote Sensing Technologies: The good, the bad and the beautiful
Dual polarization measurements capability on the USA WSR-88D radars is described and reasons for specific choices and specifications are explained. The essence of radar polarimetry is reviewed and related to physical properties of precipitation. Ample convincing evidence to recognize the type of precipitation and types of other scatterers in the fields of various polarimetric variables is presented. Emphasis is on the prevalent scatterers in Australia such as rain, hail, insects, birds, chaff, and smoke plumes. Polarimetric signatures are related to vertical motion in storms, can indicate location of tornadoes, are very good at discriminating the melting layer, and excel in differentiating between meteorological and non meteorological constituents of the atmosphere. Brief introduction to automatic classification scheme operational on the WSR-88D network is given. The scheme is routed in “fuzzy logic” principles and can be explained with elementary weighting functions. Examples of automatically classified echoes are provided to support our optimistic claims. Resent results on rainfall measurements and automatic compensation of partial beam blockage are shown. This is followed by comparison of the merits of the 3, 5 and 10 cm wavelengths for weather surveillance and polarimetric measurements.
Dusan Zrnic National Severe Storms Laboratory, NOAA Note: This is a 1 hour seminar followed by a 30 minute workshop and open forum. Us Vs Them: What sets our radar network apart from NOAA's radar network, and vice versa?
The government and private sector in the USA operate weather surveillance radars. This presentation starts with a brief description of the purpose of these radars. The government’s network of WSR-88D network is operated by the National Ocean and Atmospheric Administration (NOAA) and the network of terminal Doppler weather radars (TDWR) is operated by the Federal Aviation Administration (FAA). The FAA has also equipped its network of airport surveillance radars with weather processors to unable observation of Doppler winds and reflectivity. The emphasis of the talk is on the WSR-88D network. Specifics of the radars are reviewed and the evolution of the network to its present state is described as well as the organizational structure supporting it. The mechanism enabling change and evolution is explained and examples of the technology transfer process are given; the latest one is the upgrade to dual polarization. The network is approaching its design life of 25 years and the National Weather Service has initiated the Service Life Extension Program (SLEP) to maintain impeccable performance until a suitable replacement is ready. As good as it is, the network’s utility largely depends on data interpretation by its operators/forecasters. To that end a rigorous training program continuously evolves to keep forecasters abreast of the latest technological innovations. Several aspects of this training including organization are described
Dusan Zrnic National Severe Storms Laboratory, NOAA Note: This is a 1 hour seminar followed by a 30 minute Q&A session. Future of NOAA’s Weather Radar Enterprise: Latest Weather Radar Technologies
The NOAA National Weather Services’ strategic proposal for the future of weather surveillance radars is presented. It is an ongoing evolving plan aimed at improving warnings of tornadoes and flash floods, and providing data to numerical models for short term forecasts. Some quantitative metrics of the desirable capabilities are presented. A faster volume update rates are called for and justified through past experience of forecasters and by comparative study with numerical models. The radar that can achieve rapid scan and is therefore considered for future operation is a Multifunction Phased Array Radar (MPAR). It is agile beam radar aimed at satisfying the needs for weather observations as well as tracking airplanes. An introduction into electronic beam steering is given, potential benefits are listed, and ways to achieve rapid scan are suggested. Spectral moment fields obtained with such a radar at updates of about 30 s are compared to similar fields obtained with conventional radar at about 5 min intervals. Issues facing polarimetric agile beam radar are explained and possible solutions described.
Dr Christophe Maes Chargé de Recherche IRD/DER/LEGOS
The idea that salinity contributes to ocean dynamics is simply common sense in physical oceanography. Along with temperature, salinity determines the ocean mass and hence, through geostrophy, influences ocean dynamics and currents. But, in the tropics, salinity effects have generally been neglected. Nevertheless, observational studies of the western Pacific Ocean have suggested since the mid-1980s that the barrier layer resulting from the ocean salinity stratification within the mixed layer could influence significantly the ocean-atmosphere interactions. This appears to be especially sensitive near the eastern edge of the Pacific warm pool, the region where warm sea surface temperatures are permanently larger than 28C, and it could have important implications for the dynamics of the El Niño Southern Oscillation (ENSO) phenomenon. Understanding the relying physical processes and long-term variability remains a key point and represents a particular stringent test for coupled ocean models used in forecasts and climate projections. Another critical point to understand the low frequency variability of ENSO relies on the subtropical circulation of the thermocline waters that feeds the equatorial band. The source of these waters has to be found in the subtropical gyres of the north and south Pacific Ocean, but the proportion of the latter one dominates the system, but remains clearly less well observed. Endorsed by CLIVAR in 2008, the Southwest Pacific Ocean Circulation and Climate Experiment (SPICE) is an international research project which aims at comprehending the southwest Pacific Ocean circulation, its direct and indirect influence on both regional and basinscale climate, as well as the South Pacific Convergence Zone (SPCZ). SPICE was designed to measure and monitor the ocean circulation, and to validate and improve numerical models. South Pacific oceanic waters are carried from the subtropical gyre centre in the westward flowing South Equatorial Current (SEC), towards the southwest Pacific-a major circulation pathway that redistributes water from the subtropics to the equator and Southern Ocean. The transit in the Coral Sea is potentially of great importance to tropical climate prediction because changes in either the temperature or the amount of water arriving at the equator have the capability to modulate ENSO and produce basin-scale climate feedbacks. Nevertheless, the circulation, and its influence on remote and regional climate, is poorly understood due to the lack of appropriate measurements. In the eastern Coral Sea, the focus has been set on the observations of the jets resulting from the division of the broad SEC, and on the observation of the inflow toward the Solomon Sea.
David Smith CAWCR
A surface fitting approach has been implemented to estimate pressure centre locations for AGREPS regional ensemble tropical cyclone forecasts, comprising 24 members and 72 hours duration. This presentation will review the surface fitting methodology, subsequent track estimation, and various auxiliary calculations involving the track estimates, such as 120km strike maps and error-spread plots. Cyclones from the last 3 seasons will be considered, including the recent TC Rusty, TC Yasi from 2011, and several others in-between.
Isaac Ginis University of Rhode Island
This presentation has two parts. In Part 1, I will focus on the progress in developing a physically based coupled atmosphere-wave-ocean framework for atmosphere-ocean coupled models. This project has been conducted by a team of scientists from academia and government organizations under the auspices of the NOAA’s Hurricane Forecast Improvement Project (HFIP) and Navy’s National Ocean Partnership Program (NOPP). I will discuss scientific and technical challenges in designing the air-sea interface module in tropical cyclone conditions with particular emphasis on multiple theories of the sea state dependent wind stress. In Part 2, I will discuss a new methodology for explicit simulation of roll vortices in the hurricane boundary layer. Observations show that rolls can redistribute the momentum, mass, and energy throughout the HBL and therefore play an important role in determining the HBL structure. However, these features are not explicitly represented in existing hurricane models because of their small spatial scales. In this study, we have imbedded a two-dimensional LES model into an axisymmetric HBL model at various distances from the storm center to simulate the generation and evolution of roll vortices, as well as the interactions between rolls and the large-scale wind in the HBL. I will present numerical simulations of the formation, growth rate, and spatial scale of roll vortices due to the inflection point instability under various conditions in the HBL.
Dave Neudegg Ionospheric Prediction Service, BoM
The Ionospheric Prediction Service is the national space weather organisation and delivers services to technology affected by the solar-terrestrial environment; high-frequency radio, SATNAV, SATCOM, aeromagnetic surveys, power grids. IPSNET sensors collect data from ~1/8th the Earth's surface, complemented by space based observations. IPS operates the Australian Space Forecast Centre (ASFC) and a World Data Centre. Coupling between the troposphere-stratosphere and thermosphere-ionosphere-magnetosphere via the buffer of the mesosphere has been a topic of research for several decades. The neutral thermosphere above 80km altitude, in which the minority ionosphere is embedded, undergoes radical changes between solar max and min and the effect on the lower atmosphere in unresolved. GigaWatt energy deposition into the polar upper atmosphere occurs during auroral events caused by geomagnetic disturbances and there is evidence this affects NOx chemistry. The very small variability in solar VIS/UV across the 11 year cycle has been shown by modelling to affect Pacific decadal climate response. Travelling ionospheric disturbances are often caused by atmospheric gravity waves from sources in the lower atmosphere or higher neutral atmophere.
Greg Holland NCAR
Societal vulnerability to weather arises largely from relatively rare events at the extremes of the spectrum. Such high-impact weather includes: extended droughts, heat waves, major hurricanes, extreme local rainfall and snowfall, ice storms, European wind storms, and severe local storms and tornadoes. Somewhat paradoxically our vulnerability to property loss and societal disruption is increasing as society becomes more complex and interconnected, and as private, industrial and commercial development expands in high risk areas. Understanding and predicting variations and changes in weather extremes is thus a major societal issue, encompassing, for example, urban commercial and industrial planning, watershed maintenance and design, insurance types and premiums, and government policy. In this presentation I first examine the difficulties of differentiating climate change from variability and the question of when observable human-induced climate change commenced. I then discuss the impacts of recent past climate change on current severe weather and where this may project to in the future. This research suggests that weather extremes respond strongly to climate variability and change and, somewhat non-intuitively, that climate variability and change is best interpreted through weather extremes. The for some severe weather events the changes are initially quite rapid but then reach a saturation beyond which little or no response occurs. This will be illustrated from both observations and models and the underlying physics will be discussed.
http://www.springerlink.com/openurl.asp?genre=article&id=doi:10.1007/s00382-013-1713-0
Mojib Latif GEOMAR Helmholtz Centre for Ocean Research and University of Kiel, Germany
El Niño is a disruption of the global ocean-atmosphere system, which originates in the Equatorial Pacific and has important consequences for the weather, climate, ecology and economy of several countries around the globe. El Niño events are characterized by strong warming of the order of a few degrees Celsius of the eastern and central Equatorial Pacific with cooling over the western Equatorial Pacific and portions of the subtropical and mid-latitudinal Pacific. These sea surface temperature (SST) anomalies drive anomalous diabatic heating in the upper atmosphere thereby perturbing the global atmospheric circulation, giving rise to global teleconnections. Although El Niños considerably varied in strength during the 20th century, typical eastern Equatorial Pacific average SST anomalies in the annual mean did not exceed 2°C. Here we present an ensemble of greenhouse warming integrations of a global climate model, in which a number of El Niño events even exceed 4°C. These events, termed Super El Niños, are accompanied by extraordinary strong global teleconnections, with surface air temperature and precipitation anomalies about twice as strong as those observed in conjunction with the record El Niño events of 1982/1983 and 1997/1998. Model Super El Niños are not only characterized by their exceptional strength but also very large persistence. Most of these events occur during the second half of the greenhouse warming simulations, suggesting enhanced greenhouse warming is the cause. The occurrence of Super El Niños would have dramatic consequences for many countries around the globe.
Wojciech W. Grabowski NCAR
Shallow boundary layer clouds, such as tropical cumulus and subtropical stratocumulus, play an essential role in the climate system and seem to hold the key to the climate change. At the same time, such clouds will most likely remain parameterized in general circulation models (GCMs) for a foreseeable future. It follows that understanding macrophysical and microphysical factors controlling behavior of such clouds is important for the development of robust GCM parameterizations. This is especially true for the microphysical effects of turbulent entrainment and mixing that significantly affect the mean microphysical (and thus optical) properties of shallow convective clouds. This presentation will discuss large-eddy simulations (LES) of a field of shallow convective clouds applying either a double-moment or bin warm rain microphysics schemes. LES results show the critical role of entrainment-related above-the-cloud-base activation of cloud droplets that allows the mean droplet concentration to be approximately constant with height as documented in cloud observations. Another aspect is the homogeneity of the subgrid-scale turbulent mixing which was argued in the past to have a significant but poorly understood effect as well. The homogeneity of subgrid-scale mixing refers to the partitioning of the cloud water evaporation due to parameterized entrainment between changes of the mean droplet radius and changes of the mean droplet concentration. Homogeneous and extremely inhomogeneous mixing represent two limits of possible scenarios, where either the droplet concentration or the mean droplet radius remains unchanged during the microphysical adjustment, respectively. We developed an approach to predict the subgrid-scale mixing scenario and applied it to simulations of a field of shallow cumuli and to a case of midlatitude stratocumulus. Finally, we will also present results of numerical simulations where effects of turbulence on the warm-rain development are considered. Including turbulent effects on droplet collisions leads to dramatically larger surface precipitation rates from simulated fields of shallow cumuli. Implications of these results for GCM parameterizations of shallow convection will be discussed.
Rachel Stratton UK MetOffice
The Met Office annual cycle for development of its global NWP and climate models will be briefly explained. The changes going into GA5 will be listed, the major change being to ENDGame dynamics. GA5 is not yet defined but results will be shown from the latest GA5 candidate GA4.0#73.4.1. Emphasis will be on the impact of the convection changes going into GA5 and those which may go into GA6.
Dr. Raghu Ashrit NCMRWF
This presentation summarizes the performance of the three global models for medium range rainfall forecasting over India during summer monsoon (JJAS) of 2012. The three global forecast models are (i) GFS (T574L64) (ii) UKMO and (iii) NCUM. The evaluation is carried out for day-1, day-3 and day-5 forecasts based on the IMD-NCMRWF daily high resolution (0.5°) rainfall analysis. The verification is first presented in terms of the Mean and Root Mean Square Error (RMSE) followed by brief on the errors in the wind, temperature and humidity fields. Further the skill scores (ETS, HK and OR) are computed for forecast of rainy days (>=0.5 cm) at each grid and for the thresholds of rainfall exceeding 0.01, 1, 2, 3, 4, 5, 6 and 7 cm in 24 hours. The forecast mean rainfall over central India is overestimated in GFS model and is comparable with observations in the UKMO and NCUM models. Similarly along the west coast of India, the forecast mean rainfall in the UKMO and NCUM is realistic. GFS also overestimates (UKMO and NCUM underestimate) the observed rainfall hotspots (highest rain of the season) over central India. All three models completely fail to capture the rainfall hotspots along the west coast. The RMSE of predicted rainfall over central India shows lower magnitude in UKMO and NCUM over most parts of the India as compared with GFS forecasts. Equitable Threat Square (ETS) computed for different rainfall thresholds shows that NCUM has higher skill score as compared with UKMO and GFS for rainfall threshold >1.0 cm/day. For rainfall intensity of 0.01 cm/day all three models feature high ETS (>0.6) for all days forecast. GFS shows better skill score then UKMO for all the rainfall intensities for all days. The ‘odd ratio’ (ratio of the odds of a “yes” forecast being correct, to the odds of a “yes” forecast being wrong) also shows NCUM forecasts feature higher skill in all thresholds compared to UKMO and GFS model forecasts. The presentation also touches upon the forecasts of some of the case involving monsoon low pressure / depressions, wet/dry rainfall spells and very heavy rainfall events.
Tim Johns UK Met Office
The potential for enhanced medium-term predictability from including explicit air-sea interaction in initialized global forecasts has been explored via coupled (and uncoupled) NWP hindcast case studies using relatively high resolution (~60km atmosphere, ~25km ocean and sea ice) components of the Met Office Unified Model (MetUM). The experimental methodology and some key findings on the relative forecast skill of fully coupled versus atmosphere-only and ocean-only control hindcasts run in research mode out to 5-15 day lead time are described. Analysis focuses on objective verification of key atmospheric and oceanic fields plus an examination of some other phenomena in the coupled system, including the diurnal cycle of sea surface temperatures (SSTs) and characteristics of the Madden-Julian Oscillation. In it's research mode the coupled NWP hindcast setup performs promisingly well compared with atmosphere-only hindcasts in which initial SST anomalies are persisted. Indeed, some general improvements are apparent in tropical performance, consistent with the expectation of generally strong air-sea interaction in the Tropics influencing potential predictability there. Ocean performance improves in coupled relative to uncoupled (flux-forced) ocean forecasts in some respects. Post-initialization adjustments in the coupled system and associated uncorrected temporal drifts are an issue for both atmosphere and ocean performance. For some atmospheric variables and regions coupling the NWP forecast model nevertheless achieves a performance improvement comparable with that from purely increasing the atmospheric model resolution. Composite mean bias patterns in 15 day coupled NWP forecasts exhibit notable regional similarities to time-averaged bias patterns seen in corresponding climate model simulations (e.g. for SSTs), suggesting that some persistent climate model biases could be investigated and characterised via much shorter, verifiable coupled forecasts. Coupled NWP hindcasts are likely to prove an increasingly useful tool helping to inform future science development with the MetUM and contributing towards seamless prediction goals, playing an especially valuable role in process studies involving strong air-sea-ice interaction.
Prashant Goswami CSIR Center for Mathematical Modelling and Computer Simulation (C-MMACS), Bangalore
The limits in predictability, demonstrated by Lorenz, have played important roles in our overall scientific approach, and in particular, in our efforts at forecasting. There exists, however, a fundamental difference between many non-linear systems used for such investigations and a natural system with many scales and continuous dynamics in time. Since a forecast necessarily considers a finite and small segment of the continuous dynamics, there are processes that are not fully incorporated in the simulation in terms of phase and amplitude. As forecasting of a natural continuous system like the atmosphere or the ocean must start from initial states extracted from discrete observations, the nature of the (ensemble of) initial states, and hence the simulation, can be very different depending on how these initial states are extracted. This concept is applied to create a “monsoon ensemble” for long-range forecasting of monsoon rainfall, with forecasts from a conventional ensemble for comparison.
Prof. Simon Tett University of Edinburgh
A PDF copy of all the presented seminars can be found at the "Find Seminar Presentation Documents..." link at the top of the page (available to BoM staff only). Seminars for previous years can be found at the "Goto list of BMRC seminars for ..." site at the top of the page. In addition, a list of actual videos from some previous seminars is held in the library and can be found on the catalogue by entering Series: BMRC, Format: Video. If you would like to have a talk videotaped please contact the seminar coordinator. Note: as of 2005, it is standard practice for all seminars to be recorded as wmv movies, with the permission of the presenter.
If you would like to know more details of coordinating seminars (if, for example, you are hosting a visitor who will be giving a seminar and the regular seminar coordinator is not available), have a look at the document, "Instructions for CAWCR Seminar Coordinator"