Search Results

You are looking at 1 - 7 of 7 items for

  • Author or Editor: J. F. Newman x
  • All content x
Clear All Modify Search
Andrew J. Newman, Paul A. Kucera, and Larry F. Bliven

Abstract

Herein the authors introduce the Snowflake Video Imager (SVI), which is a new instrument for characterizing frozen precipitation. An SVI utilizes a video camera with sufficient frame rate, pixels, and shutter speed to record thousands of snowflake images. The camera housing and lighting produce little airflow distortion, so SVI data are quite representative of natural conditions, which is important for volumetric data products such as snowflake size distributions. Long-duration, unattended operation of an SVI is feasible because datalogging software provides data compression and the hardware can operate for months in harsh winter conditions. Details of SVI hardware and field operation are given. Snowflake size distributions (SSDs) from a storm near Boulder, Colorado, are computed. An SVI is an imaging system, so SVI data can be utilized to compute diverse data products for various applications. In this paper, the authors present visualizations of frozen particles (i.e., snowflake aggregates as well as individual crystals), which provide insight into the weather conditions such as temperature, humidity, and winds.

Full access
Andrew J. Newman, Paul A. Kucera, Christopher R. Williams, and Larry F. Bliven

Abstract

This paper develops a technique for retrieving snowflake size distributions (SSDs) from a vertically pointing 915-MHz vertical profiler. Drop size distributions (DSDs) have been retrieved from 915-MHz profilers for several years using least squares minimization to determine the best-fit DSD to the observed Doppler spectra. This same premise is used to attempt the retrieval of SSDs. A nonlinear search, the Levenberg–Marquardt (LM) method, is used to search the physically realistic solution space and arrive at a best-fit SSD from the Doppler spectra of the profiler. The best fit is assumed to be the minimum of the squared difference of the log of the observed and modeled spectrum power over the precipitation portion of the spectrum. A snowflake video imager (SVI) disdrometer was collocated with the profiler and provided surface estimates of the SSDs. The SVI also provided estimates of crystal type, which is critical in attempting to estimate the density–size relationship. A method to vary the density–size relationship during the event was developed as well. This was necessary to correctly scale the SVI SSDs for comparison to the profiler-estimated distributions. Five events were examined for this study, and good overall agreement was found between the profiler and SVI for the lowest profiler gate (225 m AGL). Vertical profiles of SSDs were also produced and appear to be physically reasonable. Uncertainty estimates using simulated Doppler spectra show that the retrieval uncertainties are larger than that for rainfall and can approach and exceed 100% for situations with large spectral broadening as a result of atmospheric turbulence. The larger uncertainties are attributed to the lack of unique Doppler spectra for quite different SSDs, resulting in a less well-behaved solution space than that of rainfall retrievals.

Full access
W. M. Wendland, L. D. Bark, D. R. Clark, R. B. Curry, J. W. Enz, K. G. Hubbard, V. Jones, E. L. Kuehnast, W. Lytle, J. Newman, F. V. Nurnberger, and P. Waite

Climatologists from the climate centers of 12 states of the upper Midwest contributed temperature, precipitation, and related data for December 1982, January and February 1983. Analyses present the month-to-month spatial anomaly patterns of these parameters. Mean monthly temperatures were much above normal (30-year means) during the three months in virtually the entire region, with maximum magnitudes (+4 to +9°C) extending from the Dakotas to Iowa, and to Indiana (December) and Missouri (January and February).

December precipitation was also above normal with anomalies of + 100 mm in much of Missouri, Illinois, extreme southwest Michigan, and Indiana. The maximum anomaly was over +250 mm in southern Illinois. January and February precipitation anomalies showed only little deviation from normal.

Impacts of the mild winter were generally favorable to consumers in that heating demand was reduced from normal, and particularly reduced from that of the previous year. Costs for urban snow removal were much under budget, as well. The only potentially negative impact was a relatively high survival rate of insect larvae, which is usually controlled by normally colder winter temperatures.

The 1982 peach crop of southern Illinois was essentially lost during the 1981–82 winter due to record cold temperatures. The 1983 crop was also lost largely by a late spring frost, even though the winter was one of the warmest on record.

Full access
W. M. Wendland, L. D. Bark, D. R. Clark, R. B. Curry, J. W. Enz, K. G. Hubbard, V. Jones, E. L. Kuehnast, W. Lytle, J. Newman, F. V. Nurnberger, and P. Waite

The review of the climate of the summer of 1983 and associated economic impacts were collated by the state climatologists of 12 states of the Upper Midwest. Their data archives and facilities permitted relatively fast analysis of cooperative station data.

Whereas June temperature was near normal across the region, July and August temperatures were generally higher than the 1951-80 normal, with anomalies of +2°C common, and some August anomalies representing a departure greater than 4σ. Cooling degree days were 50% greater than normal over about 1/3 of the 12- state area.

Precipitation was mixed over the area in June, with the greatest anomalies (ca. 200% of normal) in Illinois, Iowa, Minnesota, and Nebraska. July and August precipitation anomalies were similar to each other, and generally negative. Twenty-five percent of normal precipitation was not uncommon. Indeed, two stations in Nebraska and Missouri recorded no precipitation in August.

The impact of high temperatures and low rainfall resulted in substantially less corn and bean yields than expected, but yields of wheat in Kansas, and corn in Wisconsin were greater than last summer. Electrical demand was generally higher than one year earlier, with increases of +15% to +25% common, and 60% greater this July than July 1982 in South Dakota.

New climatological records of high temperatures, low rainfall, and number of days with high temperatures were established and re-established during the summer, primarily in the southwestern Upper Midwest.

Full access
V. Eyring, N. R. P. Harris, M. Rex, T. G. Shepherd, D. W. Fahey, G. T. Amanatidis, J. Austin, M. P. Chipperfield, M. Dameris, P. M. De F. Forster, A. Gettelman, H. F. Graf, T. Nagashima, P. A. Newman, S. Pawson, M. J. Prather, J. A. Pyle, R. J. Salawitch, B. D. Santer, and D. W. Waugh

Accurate and reliable predictions and an understanding of future changes in the stratosphere are major aspects of the subject of climate change. Simulating the interaction between chemistry and climate is of particular importance, because continued increases in greenhouse gases and a slow decrease in halogen loading are expected. These both influence the abundance of stratospheric ozone. In recent years a number of coupled chemistry–climate models (CCMs) with different levels of complexity have been developed. They produce a wide range of results concerning the timing and extent of ozone-layer recovery. Interest in reducing this range has created a need to address how the main dynamical, chemical, and physical processes that determine the long-term behavior of ozone are represented in the models and to validate these model processes through comparisons with observations and other models. A set of core validation processes structured around four major topics (transport, dynamics, radiation, and stratospheric chemistry and microphysics) has been developed. Each process is associated with one or more model diagnostics and with relevant datasets that can be used for validation. This approach provides a coherent framework for validating CCMs and can be used as a basis for future assessments. Similar efforts may benefit other modeling communities with a focus on earth science research as their models increase in complexity.

Full access
P. Klein, T. A. Bonin, J. F. Newman, D. D. Turner, P. B. Chilson, C. E. Wainwright, W. G. Blumberg, S. Mishra, M. Carney, E. P. Jacobsen, S. Wharton, and R. K. Newsom

Abstract

This paper presents an overview of the Lower Atmospheric Boundary Layer Experiment (LABLE), which included two measurement campaigns conducted at the Atmospheric Radiation Measurement (ARM) Program Southern Great Plains site in Oklahoma during 2012 and 2013. LABLE was conducted as a collaborative effort between the University of Oklahoma (OU), the National Severe Storms Laboratory, Lawrence Livermore National Laboratory (LLNL), and the ARM program. LABLE can be considered unique in that it was designed as a multiphase, low-cost, multiagency collaboration. Graduate students served as principal investigators and took the lead in designing and conducting experiments aimed at examining boundary layer processes.

The main objective of LABLE was to study turbulent phenomena in the lowest 2 km of the atmosphere over heterogeneous terrain using a variety of novel atmospheric profiling techniques. Several instruments from OU and LLNL were deployed to augment the suite of in situ and remote sensing instruments at the ARM site. The complementary nature of the deployed instruments with respect to resolution and height coverage provides a near-complete picture of the dynamic and thermodynamic structure of the atmospheric boundary layer. This paper provides an overview of the experiment including 1) instruments deployed, 2) sampling strategies, 3) parameters observed, and 4) student involvement. To illustrate these components, the presented results focus on one particular aspect of LABLE: namely, the study of the nocturnal boundary layer and the formation and structure of nocturnal low-level jets. During LABLE, low-level jets were frequently observed and they often interacted with mesoscale atmospheric disturbances such as frontal passages.

Full access
J. P. Taylor, W. L Smith, V. Cuomo, A. M. Larar, D. K. Zhou, C. Serio, T. Maestri, R. Rizzi, S. Newman, P. Antonelli, S. Mango, P. Di Girolamo, F. Esposito, G. Grieco, D. Summa, R. Restieri, G. Masiello, F. Romano, G. Pappalardo, G. Pavese, L. Mona, A. Amodeo, and G. Pisani

The international experiment called the European Aqua Thermodynamic Experiment (EAQUATE) was held in September 2004 in Italy and the United Kingdom to validate Aqua satellite Atmospheric Infrared Sounder (AIRS) radiance measurements and derived products with certain groundbased and airborne systems useful for validating hyperspectral satellite sounding observations. A range of flights over land and marine surfaces were conducted to coincide with overpasses of the AIRS instrument on the Earth Observing System Aqua platform. Direct radiance evaluation of AIRS using National Polar-Orbiting Operational Environmental Satellite System (NPOESS) Airborne Sounder Testbed-Interferometer (NAST-I) and the Scanning High-Resolution Infrared Sounder has shown excellent agreement. Comparisons of level-2 retrievals of temperature and water vapor from AIRS and NAST-I validated against high-quality lidar and dropsonde data show that the 1-K/l-km and 10%/1-km requirements for temperature and water vapor (respectively) are generally being met. The EAQUATE campaign has proven the need for synergistic measurements from a range of observing systems for satellite calibration/validation and has paved the way for future calibration/validation activities in support of the Infrared Atmospheric Sounding Interferometer on the European Meteorological Operational platform and Cross-Track Infrared Sounder on the U.S. NPOESS Prepatory Project platform.

Full access