2013 CIRA Seminars
Advanced precipitation sensors and numerical models track storms as they occur and forecast the likelihood of heavy rain for time frames ranging from 1 to 8 hours, 1 day, and extended outlooks out to 3 to 7 days. Forecast skill decreases at the extended time frames but the outlooks have been shown to provide "situational awareness" which aids in preparation for flood mitigation and water control operations.
With increasing use of high resolution (convection-permitting) models for numerical weather prediction and climate simulation, microphysics has moved to the forefront in terms of physical parameterizations. This is because without the use oftraditional convection parameterizations in these models, microphysicsis directly coupled to the convective dynamics. An overview of current approaches for representing microphysics will be given, as well asrecent efforts to improve parameterizations and some of the key remaining challenges.
A cumulus scheme developed in Chikira and Sugiyama (2010) is an offshoot of the prognostic Arakawa-Schubert scheme. But it is characterized by state-dependent entrainment rate based on Gregory (2001) and a spectral representation of cloud types according to cloud base updraft velocity. The scheme naturally represents the effect of free-tropospheric humidity on deep convection through the vertical variation of the entrainment rate without any empirical triggering schemes. A series of papers have been published on the impact of this scheme in one of Japanese GCM (MIROC5).
Future weather is inherently uncertain, and weather forecasts are received and used every day by millions of people. This makes weather forecasting a common form of environmental risk communication that isfamiliar to much of the public. Weather forecasts and warnings are also used by public officials, members of the public, and others to help reduce negative impacts of hazardous weather events such as hurricanes and flash floods.
Climate modeling began about 50 years ago, as a purely academic endeavor. Although things have changed considerably, especially during the past 20 years, universities have a continuing major role in model development and applications, and in training young modelers-to-be. I will discuss the history, comment on where we are now, and offer some thoughts about where the field is going.
Dual-polarization radar data provide great insight into the types and distribution of hydrometeors in storms. This information can be used to study a variety of precipitation processes. This talk will cover radar observations of warm-rain physics (collisional breakup, coalescence, evaporation, and size sorting), the lofting and freezing of raindrops in deep convective storms and the appearance of so-called "ZDR columns", and the refreezing of melted/melting hydrometeors in winter storms to form ice pellets.
Rossby wavebreaking is an important mechanism for the two-way exchange of air between the tropical upper troposphere and lower stratosphere and the extratropical lower stratosphere. We present a 30-year climatology (1981-2010) of anticyclonically and cyclonically sheared wavebreaking events along the boundary of the tropics in the 350-500 K potential temperature range from ECMWF ERA-Interim reanalyses. Lagrangian transport analyses show net equatorward transport from wavebreaking near 380 K and poleward transport at altitudes below and above the 370-390 K layer.
Over the last twenty years, a pioneering group of geomorphologists has developed processes for extracting information about prehistoric, landfalling hurricanes back through the last several millennia by studying sedimentary over-wash deposits in geologic cores. They have found active periods interspersed among long intervals with little or no trace of significant activity, which raises interesting questions about how the conditions supporting tropical cyclones change over time.
When studying the influence of microphysics on the near-surface buoyancy tendency in convective thunderstorms, in-situ measurements of microphysics near the surface are essential and those are currently not provided by most weather radars. In this study, the deployment of mobile microphysical probes in convective thunderstorms during the second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) is examined.
This talk will present high horizontal resolution solutions of an axisymmetric, constant depth, slab boundary layer model designed to simulate the radial inflow and boundary layer pumping of a hurricane. For intense vortices the u(partial u/partial r) term in the radial equation of motion produces a shock-like structure in the radial wind, i.e., near the radius of maximum tangential wind the boundary layer radial inflow decreases from approximately 20 or 30 m/s to zero over a radial distance of a few kilometers.
Ozone is a natural component of the stratosphere and a minor component in the lower atmosphere, but anthropogenic smog significantly enhances the concentrations in the troposphere. As a strong oxidizer, ozone will react with many substances including plant and animal tissues. Numerous health studies have demonstrated significant impacts on lung function from ozone exposure. As a result, over the last 40 years, the U.S. has made the ozone standard increasingly strict, in accordance with the available health data. But meeting this standard will be very challenging.
Observations reveal that long-lasting, mixed-phased stratiform clouds may be observed in all months of the year in the Arctic lower troposphere. These clouds have a large impact on radiative transfer through the atmosphere, and hence the surface energy budget. The ability of these clouds to persist for several days remains perplexing, because liquid-ice mixtures are inherently unstable and will glaciate. Modeling studies have suggested several processes operating on the local level that may contribute to their persistence.
The Northern Hemispheric maximum of the tropical rainfall is usually thought to be caused by properties of tropical landmasses, such as the size and shape of continents. However, a variety of recent studies have established that conditions even well outside the tropics also affect tropical circulation and rainfall. Using this new understanding, we demonstrate that the meridional overturning circulation of the oceans is instead the cause of the peak of zonal mean rainfall north of the equator, by causing a cross-equatorial ocean heat transport that heats the NH atmosphere more than the SH.
2012 CIRA Seminars
The Arctic is currently undergoing rapid environmental changes. Over the past few decades, the Arctic has warmed at about twice the rate as the rest of the planet. As a result, significant changes are happening in the Arctic sea ice cover, with potentially large implications not only regionally but also for the global climate. Arctic sea ice is an important regulator of the exchange of heat and moisture between the atmosphere and the ocean.
The ensemble Kalman method has shown potential for storm-scale data assimilation and ensemble forecasts. However, its computational cost is still a major issue for operational use of the EnKF. Recently, CAPS has developed an efficient parallel EnKF system that is capable of assimilating multi-scale observations. We applied this EnKF system to the May 10, 2010 Oklahoma-Kansas tornado outbreak case that spawned over 40 tornadoes to test the storm-scale, cycled EnKF DA, and ensemble forecasts.
CMMAP is one of 17 NSF Science and Technology Centers (STCs), developing and using multiscale models to better understand the climate system. A crucial part of every STC is to enhance education, engage external audiences about the research, and broaden participation in our field. We support an integrated effort to educate and engage diverse people from "K to Gray." The Little Shop of Physics is an exciting program that has worked with public schools to enagage over 200,000 kids and thousands of their teachers over 20 years.
We know that stratocumulus clouds (Sc) contribute significantly to the Earth's radiation budget and thus must be understood for predicting climate change. This talk looks at relatively recent Sc measurements (POST; Physics of Stratocumulus Top) off the California coast that follow multiple other such efforts. The POST field campaign is a direct result of learning from earlier studies including DYCOMS-II.
It has been widely noted that the anomalously extreme weather events of the recent winter seasons coincided with large-amplitude sub-seasonal to seasonal anomalies, particularly in the arctic modes of variability, i.e., Northern Annular Mode and North Atlantic Oscillation. We hypothesize that these low-frequency variations were sufficient to alter the breaking behavior of the extratropical storm-track synoptic eddies and their internal weather characteristics.
Reforecasts, or hindcasts, are retrospective numerical forecasts, ideally from the same model and data assimilation system that is used operationally. We have recently created a reforecast data set for the NCEP medium-range global ensemble forecast system (GEFS). For every day from 1985 to present, we have generated 11-member ensemble reforecasts for the 00Z cycle. The forecasts extend to 16 days lead.
Dr. Bruce Doddridge is Head of the Chemistry and Dynamics Branch in the Science Directorate at the NASA Langley Research Center located in Hampton, VA, where he leads a blended workforce of over 60 civil servant scientists, contract engineers and scientists, in addition to hosting visiting scientists, students and detailees from other organizations.
For over 20 years, COMET has engaged in a variety of educational activities in an effort to build a bridge between the academic and operational meteorology communities. With computer-based training, classroom courses, and support of operationally related research, COMET has worked with the university community to improve weather forecasting skill around the world. Originally formed to support the National Weather Service modernization efforts, we have expanded to develop training to support a wide range of international geoscience education.
For the past 20 years, Samaras has combined his technical expertise with his passion of chasing storms to collect first-ever data and images from tornadoes and lightning. He will share the techniques he uses, some of the data he has collected, and show some of the incredible imagery from logging 35,000 miles each year in Tornado Alley. He will briefly discuss what the future has in store for him.
In 1859, gold was discovered along Cherry Creek in Denver, and set in motion an epic transformation of Colorado and the West. The "Great American Desert" soon became an irrigated garden of abundance, in spite of climatic challenges. In 1870, the first large-scale community irrigation system in America was developed by settlers of the Union Colony - today Greeley, Colorado. An irrigation ditch was dug from the Cache la Poudre River to the new town, called the Greeley Irrigation Company Ditch. The first ditch rider was David Boyd, a graduate of the University of Michigan.
The Clouds from AVHRR Extended (CLAVR-x) is NOAA's operational cloud processing system for the AVHRR on the NOAA-POES and EUMETSAT-METOP series of polar orbiting satellites. The data set is comprised of the relevant cloud parameters, such as cloud height, cloud cover, optical depth, particle size and water content. The Pathfinder Atmospheres-extended (PATMOS-x) is a climate data record (CDR) based on CLAVR-x algorithms and includes the Essential Climate Variables (ECV) of cloud properties. The global PATMOS-x v5 data set is part of the National Climate Data Center of NOAA.
One of the most ambitious field projects organized to study tornadoes and tornadic storms occurred during the spring and summer of 2009/2010 (VORTEX2 - Verification of the Origins of Tornadoes Experiment). A number of mobile platforms were deployed in a coordinated manner in order to increase the number of intercepts of tornadic storms. This seminar presents an analysis of a tornado that developed west of LaGrange, Wyoming on 5 June 2009. The tornado was scanned by several radars while the evolution of the funnel was captured by a series of photographs.