Staff Notes Daily Announcements

Please view the New Hires and Departures as of Friday, August 10, 2018 at this location:

https://www2.fin.ucar.edu/hr/new-hires-and-departures

Clouds and aerosols: linking aircraft measurements, satellite observations and model simulations

Clouds and aerosols are two key components in the Earth’s atmosphere. A key step towards an improved understanding of clouds and aerosols is linking observations with simulations. The first part of this seminar will compare cloud macro- and microphysical properties between in-situ aircraft observations and a hierarchy of models, including a cloud-resolving model, WRF model, and the NCAR CAM5 climate model. The types of clouds to be analyzed include continental anvil cirrus over the U.S. and mixed-phase clouds over the Southern Ocean. The second part of this seminar will showcase the applications of satellite observations of aerosol optical depth (AOD) for assisting air pollution management in the Bay Area in California. Surface-level PM2.5 concentrations will be derived from satellite AOD, which complement the existing ground-based monitor measurements.

Thursday, 16 August 2018, 11:00 AM Refreshments 10:45 AM NCAR-Foothills Laboratory • 3450 Mitchell Lane Bldg 2 Seminar Room (Rm1001) Webcast: https://ucarconnect.ucar.edu/live

RAL Seminar

Catalyzing Decision Services with Probability Forecasts on Demand

John K. Williams The Weather Company, An IBM Business

An “operations to decisions” divide is preventing much of the available societal value of the weather enterprise’s increasingly accurate forecasts from being fully realized. Existing weather decision support services often target high-impact events, government agencies and large businesses with tailored weather information, but there is also significant potential value in improving the ability of society at large to use weather information to make a broad spectrum of day-to-day decisions. Bridging the “O2D” divide requires an accessible framework that includes the requisite weather forecasts, methods for inferring impacts, techniques for determining optimal actions, compelling ways to communicate supporting evidence and effective means to execute decisions. An optimal decision is one that limits the risk of an unacceptable outcome, provides the greatest expected net benefit, is timely, and can be cogently described and explained.

While some domains may have more limited requirements, weather-based decision services generally require (1) forecasts of all possible future weather scenarios and their likelihoods; (2) a way to determine costs and benefits associated with prospective actions under each scenario; (3) predictions of the benefit versus opportunity cost of waiting for a more certain forecast before making a decision; and (4) tools and strategies for communicating and executing decisions.  Towards this end, The Weather Company has launched a new probability forecasting capability called Probability Forecasts on Demand (PFoD). PFoD builds on our 18-year evolution of the DICast-based automated multi-model consensus forecasting technology, which drives a broad array of business and consumer weather products including the Weather Channel website and mobile applications. PFoD provides probability distribution function (PDF) and related descriptions of forecast uncertainty for several weather variables at any global location.  In addition, it provides a user-specified number of calibrated ensemble “prototype” forecasts that provide the multivariate weather trajectories required to evaluate nonlinear weather impacts and spatiotemporal dependencies. The prototypes are calibrated and constructed to be “equally likely,” giving them an advantage over raw NWP ensembles that may exhibit biases, under- or over-dispersion and unequal skill among members. Coupled with machine-learned, heuristic or physically-based impact models, PFoD provides a basis for quantifying risks and estimating expected values for prospective actions or policies. The availability of PFoD via an API offers easy access to the weather information required to develop a broad array of decision services.  This talk will describe and illustrate PFoD’s capabilities, provide sample decision use cases, and highlight some of the many forecasting and decision service design challenges that remain to be addressed.

Tuesday, August 21, 2018 1:30-2:30 FL2 - 1001

ACOM SEMINAR

Title:  Impact of ozone depleting substances on the stratospheric Brewer-Dobson circulation

Presenter:  Marta Abalos, Universidad Complutense de Madrid

Abstract:  The Brewer-Dobson circulation (BDC), responsible for tracer and heat transport in the stratosphere, is expected to strengthen due to increasing greenhouse gas emissions. While this robust result has been supported by a large body of literature, substantially less attention has been paid to the impact of ozone depleting substances (ODS). Here we will present recent modeling evidence that anthropogenic ODS emissions are also key drivers of long-term trends in the BDC. It will be shown that ODS have contributed to about half of the BDC trends over the last decades of the 20th century, and that the phasing out of ODS emissions as a consequence of the Montreal Protocol will lead to a considerable reduction of the acceleration trends in the 21st century. A distinction will be made between two pathways for ODS impact on the BDC. In the chemical pathway, ODS cause Antarctic ozone depletion which then induces dynamical changes in the SH stratosphere. In the radiative pathway, ODS act as greenhouse gases and induce tropospheric warming, which in turn drives changes in the BDC. It will be argued that the radiative pathway is strongly coupled to the ocean response, while the chemical pathway is decoupled from the ocean and leads to interhemispheric asymmetry in BDC trends. Finally, a comparison of the BDC trends in the model with those obtained from reanalysis data will show that ODS have been the main driver of observed austral summer trends over the last decades of the 20th century. This is the case for the two components of the BDC: the residual circulation and isentropic mixing.

Friday, August 17, 2018, 3:30 p.m Refreshments 3:15 p.m FL-1022, Large Auditorium Live webcast: http://ucarconnect.ucar.edu/live