G. Levy

G. Levy
NWRA - NorthWest Research Associates/Pan Ocean Remote Sensing Asssociation

PhD

About

79
Publications
8,496
Reads
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590
Citations
Introduction
Experienced in meteorological, climate, mathematical/statistical, Bayesian & fuzzy methodology & applications; Technical & non-technical writing, I have served on Science Steering Committees of the US Climate Variability & Predictability program, as co-chair of its Process Studies & Model Implementation panel; as VP & President of the Pan Ocean Remote Sensing (PORSEC) association; associate-editor of the Int'l J. Remote Sensing & as PI, reviewer, professor, invited speaker & affiliate for US & int'l agencies & universities, National science academies (Chinese, Israel, Netherlands, Russian, US) & journals
Additional affiliations
June 2014 - February 2015
Chinese Academy of Sciences
Position
  • Sr. Visiting Professor
April 2002 - present
University of Phoenix
Position
  • Affiliate faculty
September 2001 - January 2003
The Boeing Company
Position
  • Statistician

Publications

Publications (79)
Article
In the Bay of Bengal, the warm, dry boreal spring concludes with the onset of the summer monsoon and accompanying southwesterly winds, heavy rains, and variable air-sea fluxes. Here, we summarize the 2018 monsoon onset using observations collected through the multinational Monsoon Intraseasonal Oscillations in the Bay of Bengal (MISO-BoB) program b...
Article
The research presented in this special issue provides a much-needed integration of satellite remote sensing observations into the ocean and climate science and will continue. It coincided with the beginning of, and provides an introduction to, two major international projects: Years of the Maritime Continent (YMC), and the United Nations Decade of...
Book
This is a special issue featuring a selection of research papers presented at the 14th Biennial Pan Ocean Remote Sensing Conference (PORSEC) in November 2018, in Jeju Island, South Korea. The 21 research papers in this issue, published online Sept., 2019 - April, 2020 cover the broad range of research work carried out using remote sensing technique...
Article
The Inter-Tropical Convergence Zone (ITCZ) is a persistent band of organized convection in the tropics that arises due to the surface convergence of the Hadley cells. The location and intensity of the ITCZ is heavily influenced by sea surface temperature and low-level latent heat transport. The ITCZ undergoes an annual march across the equator, and...
Book
This is a special issue featuring a selection of research papers presented at the 13th Biennial Pan Ocean Remote Sensing Conference (PORSEC) in November 2016, held in Fortaleza, state of Ceará, Brazil. The 17 research papers in this issue, published online Aug. 2017-April, 2018, cover the broad range of problems in satellite observations of the oce...
Article
This is a special issue featuring a selection of research papers presented at the 13th Biennial Pan Ocean Remote Sensing Conference (PORSEC) in November 2016. All 18 papers in this issue have been published on line as they have been accepted, and are tabulated in the order they appear in the special issue in the table. A reprint of the preface is a...
Article
The variability of aerosol optical thickness (AOT) in the tropical Indian Ocean (IO) and South China Sea (SCS) during the intermonsoon (February–May) is investigated using shipboard and satellite data from 2011 to 2014, in order to understand the mechanism controlling AOT production and transport. Overall AOT in tropical IO is significantly smaller...
Article
Full-text available
At the beginning of 2008, disastrous weather with snowstorms truck South China. Analysis of satellite and in situ data revealed obvious changes in ecological environments in the northern South China Sea after snowstorms. The sea surface temperature (SST) data from NOAA and Moderate Resolution Imaging Spectroradiometer (MODIS) from 2000 to 2013, and...
Conference Paper
There are limited ocean surface vector wind observations in the Tropical Atlantic. These are mainly the sixteen PIRATA buoys along with some observations from volunteer ship observations, which are largely constrained to a few narrow shipping tracks that themselves have seasonalvariability. Because satellite scatterometers provide very high quality...
Conference Paper
Full-text available
Since 1992 The Pan Ocean Remote Sensing Conference Association, PORSEC Ass., has sponsored a short course or tutorial in association with its bi-annual conferences in several different countries, that were looking to develop their use of remotely sensed data for operations or research in meteorology or oceanography. The goal was to enhance scientif...
Article
This is a special issue featuring a selection of research papers presented at the 12th Biennial Pan Ocean Remote Sensing Conference (PORSEC) in November 2014. Since its establishment in 1990 as the Pacific Ocean Remote Sensing Conference, PORSEC has rapidly gained global status as one of the most prestigious oceanic remote-sensing conferences in th...
Article
Full-text available
This study investigates the capability of high-spatial resolution Landsat Thematic Mapper (TM) data to sense and document suspended particulate matter concentration (SPMC) variability resulting from the influence of large structures in coastal waters. Two bridges, located in the coastal waters of the Yangtze River delta, are used as examples. A new...
Presentation
Full-text available
Plenary talk to Fuzzy Information Processing Society (NAFIPS) meeting held jointly with 2015 5th World Conference on Soft Computing (WConSC)
Presentation
Plenary talk to Fuzzy Information Processing Society (NAFIPS) meeting held jointly with 2015 5th World Conference on Soft Computing (WConSC)
Presentation
Full-text available
Plenary talk to Fuzzy Information Processing Society (NAFIPS) meeting held jointly with 2015 5th World Conference on Soft Computing (WConSC)
Book
Full-text available
The proceedings of the 12th Biennial conference of the Pan Ocean Remote Sensing Conference, PORSEC2014, “Ocean Remote Sensing for Sustainable Resources”, ISBN 978-602-72335-0-8 have been published, and files of cover page, preface and contents of the proceeding, as well as papers (organized in two groups of papers, oral and poster presentation) in...
Conference Paper
Full-text available
Ship-measured Aerosol Optical Thickness (AOT) data collected in 2011, are correlated with collocated MODIS AOT observations over the Indian Ocean in the present study. A good correlation (r = 0.87) is found between the MODIS Aqua estimates and the ship-measured data at 550nm, and the results show a clear spatial difference. Correlation of datasets...
Conference Paper
Full-text available
This study focuses on improving the three-dimensional rain rate retrieval from backscattering coefficients measured by a space-borne X-SAR sensor using tomography. The use of tomography, combined with the use of an inversion model, will permit retrieval of new information about the distribution of very large perturbation events thanks to the high s...
Conference Paper
Following common practice in data assimilation schemes, most diagnostic tools and metrics for intercomparison of reanalyses, correct a model forecast (hincast) or background field of continuous variables based on optimal minimization of the model variable with respect to observed values, summed over some or all grid points in a discretization. Eval...
Chapter
Full-text available
This chapter introduces a numerical simulation and forecasting technique for tropical cyclones in the South China Sea, and describes a technique to initialize model simulation of typhoons that improves typhoon formation and forecasting in the simulation. It includes three-dimensional variational data assimilation and the curvature-modification line...
Chapter
Full-text available
This chapter introduces a numerical simulation and forecasting technique for tropical cyclones in the South China Sea, and describes a technique to initialize model simulation of typhoons that improves typhoon formation and forecasting in the simulation., It includes three-dimensional variational data assimilation and the curvature-modification lin...
Article
[1] A space-time interpolator for creating average geophysical fields from satellite measurements is presented and tested. It is designed for optimal spatiotemporal averaging of heterogeneous data. While it is illustrated with satellite surface wind measurements in the tropics, the methodology can be useful for interpolating, analyzing, and merging...
Conference Paper
Full-text available
The European Remote-sensing Satellite (ERS)-2 scatterometer provides wind retrievals over Ocean. To satisfy the needs of high quality and homogeneous set of scatterometer measurements, the European Space Agency (ESA) has developed the project Advanced Scatterometer Processing System (ASPS) with which a long-term dataset of new ERS-2 wind products,...
Article
Full-text available
TerraSAR-X TS-X is a new, fully polarized X-band synthetic aperture radar SAR satellite, which is a successor of the Spaceborne Imaging Radar X-band Synthetic Aperture Radar SIR-X-SAR and the SRTM. TS-X has provided high-quality image products over land ...
Article
We develop an automated and user-trained algorithm that spatially analyzes satellite data and detects the presence of double inter-tropical convergence zones (DITCZ) and apply it to 30 years worth of satellite collected outgoing long-wave radiation data. The analysis of the data via vertical wavelet transform identifies DITCZ occurrences over the I...
Article
Full-text available
We characterize the climatological features of the double inter-tropical convergence zones (DITCZs) over the western Indian Ocean during November–December by a synergistic analysis of the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite (HOAPS III) data (1988–2005) and the National Aeronautics and Space Administration's (NASA's) A-Trai...
Conference Paper
As mesoscale models improve, they require input data with higher spatial resolution, including rainfall measurements with spatial resolution < 2km, such as those that can be obtained from synthetic aperture radars (SAR). Such measurements are now available from at least half a dozen satellite-borne X-band SARs. These include the TerraSAR-X (TSX) an...
Conference Paper
As mesoscale models improve, they require input data with higher spatial resolution, including rainfall measurements with spatial resolution < 2km, such as those that can be obtained from synthetic aperture radars (SAR). Such measurements are now available from at least half a dozen satellite-borne X-band SARs. These include the TerraSAR-X (TSX) an...
Chapter
We examine the organization and temporal evolution of deep convection in relation to the low level flow over the Indian Ocean by a synergistic analysis of several satellite datasets for wind, rainfall, Outgoing Longwave Radiation (OLR) and cloud liquid water. We show that during the active Indian monsoon season, symmetric instability is present and...
Article
The ITCZ can be regarded as a marker of the meteorological equator, and its convective organization determines to a large extent the tropical belt. We examine the organization and temporal evolution of deep convection in relation to the low level flow over the western Indian Ocean by a synergistic analysis of several satellite datasets for wind, ra...
Article
Ideally, a verification and validation scheme should be able to evaluate and incorporate lower dimensional features (e.g., discontinuities) contained within a bulk simulation even when not directly observed or represented by model variables. Nonetheless, lower dimensional features are often ignored. Conversely, models that resolve such features and...
Article
Full-text available
Ideally, a validation and assimilation scheme should maintain the physical principles embodied in the model and be able to evaluate and assimilate lower dimensional features (e.g., discontinuities) contained within a bulk simulation, even when these features are not directly observed or represented by model variables. We present such a scheme and s...
Article
Full-text available
The north–south symmetry of the low level near-equatorial atmospheric flow is examined in relation to the position of the Intertropical Convergence Zone (ITCZ) over the Indian Ocean with the aid of satellite and reanalysis data. Absolute vorticity (AV) and convergence fields on temporal scales of 10 days are derived from 7 years of Quick Scatterome...
Article
Full-text available
The spatio-temporal relationship between sea surface features and squid catch rates in the north-west Pacific Ocean were studied. Thermal-colour features were extracted from long-term Advanced Very High Resolution Radiometer (AVHRR) (1995-2001) and Sea-viewing ...
Article
Full-text available
Ideally, a validation and assimilation scheme should maintain the physical principles embodied in the model and be able to evaluate and assimilate lower dimensional features (e.g., discontinuities) contained within a bulk simulation, even when these features are not directly observed or represented by model variables. We present such a scheme and s...
Article
Full-text available
We examine the organization and temporal evolution of deep convection in relation to the low level flow over the Indian Ocean by a synergistic analysis of several satellite datasets for wind, rainfall, Outgoing Longwave Radiation (OLR) and cloud liquid water. We show that during the active Indian monsoon season, symmetric instability is present and...
Article
Full-text available
Novel metrics designed to evaluate the skill of geophysical models in simulating discontinuities and linear features are introduced and tested using a sea-ice model and remotely sensed observations of leads. The metrics are formulated as frequency-based indices of agreement, thus maintaining the simplicity desired in model development and operation...
Article
Full-text available
1] This paper revisits the Arctic Ice Dynamics Joint Experiment (AIDJEX) assumptions about pack ice behavior with an eye to modeling sea ice dynamics. The AIDJEX assumptions were that (1) enough leads were present in a 100 km by 100 km region to make the ice isotropic on that scale; (2) the ice had no tensile strength; and (3) the ice behavior coul...
Article
The treatment of leads as cracks or discontinuities (see Coon et al. presentation) requires some shift in the procedure of evaluation and comparison of lead-resolving models and their validation against observations. Common metrics used to evaluate ice model skills are by and large an adaptation of a least square "metric" adopted from operational n...
Article
Full-text available
We are developing, testing, and validating a new sea ice dynamics model that treats the ice cover as an elastic/decohesive material in the permanent pack and includes the correct frazil/pancake behavior in the marginal zone. Two salient features of present ice dynamics models are that they do not: 1) reproduce the oriented fracture patterns of open...
Article
Full-text available
Non-equilibrium wind-wave conditions exist where the surface wave field adjusts to sudden wind accelerations. Analyses of surface fluxes from wind burst events in non-equilibrium conditions in the equatorial western Pacific region are presented. The analyses establish a relationship between the momentum flux and the wind tendency in non-equilibrium...
Article
Full-text available
The Atmospheric Boundary Layer (ABL) mean flow frequently consists of an organized secondary circulation in the form of counter rotating rolls embedded in it. Theory predicts this is the case for a range of thermodynamic conditions. Although generally associated with the formation of “cloud streets”, numerical and theoretical studies suggest that r...
Article
Full-text available
The atmospheric boundary layer (ABL) response to surface fluxes and prescribed advective and radiative forcings is tested in a column ABL model. Observations are used to run an ABL model in a marine tropical convective regime. The influence of surface fluxes and prescribed advective and radiative forcings potential temperature and specific humidity...
Article
Full-text available
A number of spaceborne microwave sensors have been launched in the last decade, significantly increasing the quantity and quality of observations over the oceans that can be used to study air-sea interactions. These observations, when combined with conventional in-situ observations and model output, can be used to improve air-sea flux estimates and...
Article
Full-text available
Scatterometer and buoy observations are collocated at different locations spanning a range of climatic regimes in order to (1) develop a spatiotemporal conversion method that allows synergistic use of satellite and in situ data to estimate flux enhancement due to unresolved wind variability, and (2) formulate a resolution-dependent velocity-scale t...
Article
The goals and procedures of the most data-intensive operations in atmospheric sciences, including data assimilation and fusion, are introduced. We explore specific problems that result from the expansion in observing systems from conventional to satellite borne and the corresponding transition from small, medium, and large datasets to massive datas...
Article
Full-text available
Eight years (1980–1987) of Wake Island rawinsonde data are used to derive atmospheric boundary layer (ABL) depth, integrated boundary-layer moisture, and a measure of boundary-layer ageostrophy. The variability in these processes controls the accumulation of moisture and heat in the tradewind regions and their transport to regions of intense convec...
Article
Full-text available
This report describes work on the Oregon State University (OSU) atmospheric boundary-layer (ABL) model under AFOSR Grant NO. F49620-96-1-0058. This model was developed to provide ABL and land-surface parameterization schemes for large-scale numerical weather prediction models. We address five classes of model development and testing: (1) A simple t...
Conference Paper
The planetary boundary layer (PBL) mean flow frequently consists of an organized secondary circulation in the form of counter rotating rolls embedded in the mean flow. Theory predicts this is the case in unstable, neutral and slightly stable stratification and for a range of baroclinic conditions. Although generally associated with the formation of...
Article
Full-text available
Observations show that, for a given geostrophic forcing, baroclinity acting on the planetary boundary layer produces a nearly sinusoidal modification of the near-surface wind. Compared to barotropic conditions the speed is enhanced in the direction of the thermal wind and the cross-isobar angle increases (decreases) in cold (warm) advection. These...
Article
The spatial and temporal sampling of polar-orbiting satellites results in errors in some level 3 data products of mean global fields. The problem has been identified in data from the Special Sensor Microwave Imager, Active Microwave Instrument, and the Microwave Sounding Unit and therefore is believed to be ubiquitous to many global data sets from...
Chapter
The goals and procedures of the most data intensive operations in atmospheric sciences-data assimilation and fusion-are introduced. We explore specific problems which result due to the expansion in observing systems from conventional to satellite borne and the corresponding transition from small, medium, and large data sets to massive data sets. Th...
Article
Full-text available
Monthly mean wind fields from the European Remote Sensing Satellite (ERS1) scatterometer are presented. A banded structure which resembles the satellite subtrack is clearly and consistently apparent in the isotachs as well as the u and v components of the routinely produced fields. The structure also appears in the means of data from other polar-or...
Article
Full-text available
The north-south symmetry of the low level near-equatorial atmospheric flow is examined over the equatorial oceans with the aid of conventional and satellite observations and is compared to the output of a climate model. The qualitative agreement between the observations and the symulations at low levels is very good. For the month to seasonal time...
Conference Paper
Full-text available
Monthly mean wind fields from the European Remote Sensing Satellite (ERS-1) scatterometer are calculated and presented. A banded structure which resembles the satellite subtrack is clearly and consistently apparent in the isotachs as well as the u- and v-components of the wind with a typical variation (amplitude) of 4 ms<sup>-1</sup>. An experiment...
Article
Analyses of remotely sensed low-level wind vector data over the Southern Ocean are performed. Five-day averages and monthly means are created and the month-to-month variability during the winter (July-September) of 1978 is investigated. The remotely sensed winds are compared to the Australian Bureau of Meteorology (ABM) and the National Meteorologi...
Article
Full-text available
Analyses of remotely sensed wind vector data from six satellite passes over parts of the Southern Ocean during September 1978 are shown. Winds are input to a planetary boundary layer model to produce sea level pressure fields. These are compared to the Australian Bureau of Meteorology conventional mean sea level pressure and to the European Centre...
Article
Full-text available
The ability to determine surface pressure fields from satellite scatterometer data was shown by Brown and Levy (1986). The surface winds are used to calculate the gradient winds above the planetary boundary layer, and these are directly related to the pressure gradients. There are corrections for variable stratification, variable surface roughness,...
Article
Full-text available
The effects of thermal advection and atmospheric stratification are statistically evaluated using Seasat scatterometer observations as a data base. The results indicate that, whenever the surface winds or wind stress are related to the atmospheric pressure field, the appropriate stratification and baroclinic corrections should be applied. Without s...
Article
Full-text available
Statistical tests are performed on the Seasat scatterometer observations to examine if and to what degree thermal advection and stratification effects manifest themselves in these remotely sensed measurements of mean wind and wind stress over the ocean. On the basis of a two layer baroclinic boundary layer model which is presented, it is shown that...
Article
Full-text available
The importance of various dynamical processes in the surface fronts over the ocean is investigated using the unique data set supplied by the Seasat-A satellite scatterometer, in conjunction with a planetary boundary layer model. The governing equations are presented, and a similarity model that includes the effects of shear and the effects of shear...
Article
Full-text available
The governing vorticity and divergence equations in the surface layer are derived and the roles of the different terms and feedback mechanisms are investigated in semigeostrophic and nongeostrophic cold-frontal systems. A planetary boundary layer model is used to perform sensitivity tests to determine that in a cold front the ageostrophic feedback...
Article
Full-text available
Fields of divergence calculated from the Seasat-A Satellite Scatterometer winds and fields of integrated water vapor and rainrate from the Scanning Multichannel Microwave Radiometer on Seasat are constructed for three different midlatitude cyclones. These storms include an explosively deepening cyclone that occurred in the North Atlantic (also know...
Article
The satellite scatterometer data open unprecedented opportunities to look at maritime storms and fronts. They are combined with observations, modeling efforts, and theory to study five cases. These provide the data to investigate frontal behavior in terms of its vorticity and divergence. The appropriate momentum, divergence and vorticity equations...
Article
Full-text available
The University of Washington's planetary boundary layer model is inverted to use remotely sensed satellite scatterometer-derived surface winds as input to calculate maritime surface pressure fields. The analysis of three different synoptic storm situations is performed using the model and is then compared to conventional National Weather Service an...
Article
Full-text available
A simple economical objective analysis scheme is devised and tested on real scatterometer data. It is designed to treat dense data such as those of the Seasat A Satellite Scatterometer (SASS) for individual or multiple passes, and preserves subsynoptic scale features. Errors are evaluated with the aid of sampling ('bootstrap') statistical methods....
Article
Full-text available
Nine clouds are simulated by perturbing Florida Area Cumulus Experiment (FACE) field soundings employing the Colorado State University cloud model. After a cloud similar in size to the one observed is initiated, glaciation is simulated in experiments designed to study the mechanisms by which glaciation is communicated to the subcloud boundary layer...
Article
Full-text available
Includes bibliographical references. Sponsored by National Oceanic and Atmospheric Administration Sponsored by the National Science Foundation FACFATMS100207BLUE
Article
Full-text available
Analyses of remotely sensed low-level wind vector data over the Southern Ocean are performed. Five-day averages and monthly means are created and the month-to-month variability during the winter (July-September) of 1978 is investigated. The remotely sensed winds are compared to the Australian Bureau of Meteorology (ABM) and the National Meteorologi...