Spooner C.M.,NorthWest Research |
Mody A.N.,BAE Systems |
Chuang J.,BAE Systems |
Anthony M.P.,BAE Systems
Proceedings - IEEE Military Communications Conference MILCOM | Year: 2013
We present novel tunnelized second- and higher-order cyclostationary signal processing algorithms to simultaneously detect and characterize RF signals. Techniques that exploit second- and higher-order cyclostationary features to detect and classify signals possess many desirable properties. However, their pervasive use and hardware implementation have been hampered because such features are highly complex, and consume substantial processor energy. In this paper we present a novel concept, where we observe that severe but purposeful under-sampling of the signals through tunneling preserves sufficient exploitable cyclostationarity, even when the tunnel bandwidth is much smaller than the signal bandwidth. This phenomenon is then exploited to create a low complexity and flexible suite of algorithms to simultaneously detect and characterize signals using their tunneling-distorted cyclostationary features. We also demonstrate that such algorithms can detect and characterize signals for a highly adverse signal-to-interference-plus-noise ratio, even when multiple signals completely overlap in time and frequency. © 2013 IEEE. Source
Miyagawa K.,Japan Meteorological Agency |
Petropavlovskikh I.,University of Colorado at Boulder |
Evans R.D.,National Oceanic and Atmospheric Administration |
Long C.,National Oceanic and Atmospheric Administration |
And 5 more authors.
Atmospheric Chemistry and Physics | Year: 2014
Analyses of stratospheric ozone data determined from Dobson-Umkehr measurements since 1977 at the Syowa (69.0° S, 39.6° E), Antarctica, station show a significant decrease in ozone at altitudes higher than that of the 4 hPa pressure level during the 1980s and 1990s. Ozone values over Syowa have remained low since 2001. The time series of upper stratospheric ozone from the homogenized NOAA SBUV (Solar Backscatter Ultraviolet Instrument)(/2) 8.6 overpass data (±4°, 24 h) are in qualitative agreement with those from the Syowa station data. Ozone recovery during the austral spring over the Syowa station appears to be slower than predicted by the equivalent effective stratospheric chlorine (EESC) curve. The long-term changes in the station's equivalent latitude (indicative of vortex size/position in winter and spring) are derived from MERRA (Modern Era Retrospective-analysis for Research and Applications) reanalyses at ∼ 2 and ∼ 50 hPa. These data are used to attribute some of the upper and middle stratospheric ozone changes to the changes in vortex position relative to the station's location. In addition, high correlation of the Southern Hemisphere annular mode (SAM) with polar upper stratospheric ozone during years of maximum solar activity points toward a strong relationship between the strength of the Brewer-Dobson circulation and the polar stratospheric ozone recovery. In the lower stratosphere, ozone recovery attributable to CFCs (chlorofluorocarbons) is still not definitive, whereas the recovery of the upper stratosphere is slower than predicted. Further research indicates that dynamical and other chemical changes in the atmosphere are delaying detection of recovery over this station. © Author(s) 2014. Source
Schirber S.,Max Planck Institute for Meteorology |
Manzini E.,Max Planck Institute for Meteorology |
Alexander M.J.,NorthWest Research
Journal of Advances in Modeling Earth Systems | Year: 2014
In order to simulate stratospheric phenomena, such as the Quasi-Biennial Oscillation (QBO), atmospheric general circulation models (GCM) require parameterizations of small-scale gravity waves (GW). In the tropics, the main source of GWs is convection, showing high spatial and temporal variability in occurrence and strength. In this study, we implement in the GCM ECHAM6 a source parameterization for GWs forced by convection. The GW source parameterization is based on the convective heating depth, convective heating rate, and the background wind. First, we show that the heating depth distribution of convective properties strongly influences the waves' source spectra. The strong sensitivity of spectral wave characteristics on heating property distributions highlights the importance of a realistic parameterization of convective processes in a GCM. Second, with the convection-based GW scheme as the unique source of GWs, the GCM simulates a QBO with realistic features. While the vertical extent of the easterly jet shows deficiencies, the wind speeds of the jet maxima and the variance of wind alteration show a clear improvement, compared to the standard model which employs a parameterization with constant, prescribed GW sources. Furthermore, the seasonality of the QBO jets downward progression is modeled more realistically due to the seasonality of physically based gravity wave sources. Key Points Implementation of a convection-based GW source parameterization into a GCM Explore physical aspects of convection-based GW source parameterization Physical GW parameterization improves QBO © 2014. American Geophysical Union. All Rights Reserved. Source
Agency: Department of Commerce | Branch: | Program: SBIR | Phase: Phase II | Award Amount: 200.00K | Year: 1998
Accurate and timely information about space weather has become essential for managing many technologies on which our lives depend (e.g., radio communications, Global Positioning Systems). A major limitation to accessing this information from NOAA and private vendors is the lack of well-defined, standardized methods for accessing data or running models remotely over the Internet. Northwest Research Associates proposes to develop both an open- architecture Space-Weather Model/Application Programming Interface (SWxMAPI) and a proprietary set of software tools that will allow users to provide and request Space Weather Data via this Interface. In Phase 1 of this SBIR proposal, we will develop an initial design of the SWxMAPI. We will then create prototypes of three of four modules in the envisioned system: A Space Weather Model Server (SWxMS) that accepts and serves client requests for data and model-run output; a client-side agent that can be used by non-expert personnel to formulate data requests compliant with SWxMAPI and receive data products; and a Space Weather Remote Database Agent that serves as an interface between the SWxMS and local and remote databases. The prototype system will build a generalized interface to SCINTMOD, our existing Web implementation (http://www.nwra.co/nwra/scintpred/) of a space weather model.
Agency: Department of Commerce | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 49.95K | Year: 1995
We propose a unified front end (UFE) for placing NOAA's databases on the Internet. The UFE uses a combination of existing World-Wide Web technology along with custom-written elements to present the user with an efficient, content-oriented data search. The goal of the UFE is to allow data seekers to concentrate on the measurements they seek rather than on which NOAA database contains them. A second goal of this work is to reduce loading on NOAA's databases and network connections as well as to minimize the modifications required to put those databases on-line. A third goal is to improve data access for users with low-bandwidth Internet connections. The proposed solution includes a "state engine" to remember prior user requests. The user is therefore not required to repeatedly enter the same search parameters during an iterative data request. By implementing the state engine at the UFE level, the interface with individual databases is simplified. This overcomes a major impediment of applying WWW technology to database access. The proposed solution also includes a real-time bandwidth-sensing feature to optimize the transfer mode for the output data set.