Engineering topics

Gille, J. C.

Publications and source records attributed to Gille, J. C..

At least 19 records

NASA NTRS2010

Southern Hemisphere Carbon Monoxide Inferannual Variability Observed by Terra/Measurement of Pollution in the Troposphere (MOPITT)

Biomass burning is an annual occurrence in the tropical southern hemisphere (SH) and represents a major source of regional pollution. Vegetation fires emit carbon monoxide (CO), which due to its medium lifetime is an excellent tracer of tropospheric transport. CO is also one of the few tropospheric trace gases currently observed from satellite and this provides long-term global measurements. In this paper, we use the 5 year CO data record from the Measurement Of Pollution In The Troposphere (MOPITT) instrument to examine the inter-annual variability of the SH CO loading and show how this relates to climate conditions which determine the intensity of fire sources. The MOPITT observations show an annual austral springtime peak in the SH zonal CO loading each year with dry-season biomass burning emissions in S. America, southern Africa, the Maritime Continent, and northwestern Australia. Although fires in southern Africa and S. America typically produce the greatest amount of CO, the most significant inter-annual variation is due to varying fire activity and emissions from the Maritime Continent and northern Australia. We find that this variation in turn correlates well with the El Nino Southern Oscillation precipitation index. Between 2000 and 2005, emissions were greatest in late 2002 and an inverse modeling of the MOPITT data using the MOZART chemical transport model estimates the southeast Asia regional fire source for the year August 2002 to September 2003 to be 52 Tg CO. Comparison of the MOPITT retrievals and NOAA surface network measurements indicate that the latter do not fully capture the inter-annual variability or the seasonal range of the CO zonal average concentration due to biases associated with atmospheric and geographic sampling.

Edwards, D. P.↗

NASA NTRS2009

Measurements of Pollution In The Troposphere (MOPITT) Validation through 2006

Comparisons of aircraft measurements of carbon monoxide (CO) to the retrievals of CO using observations from the Measurements of Pollution in The Troposphere (MOPITT) instrument onboard the Terra satellite are presented. Observations made as part of the NASA INTEX-B and NSF MIRAGE field campaigns during March May 2006 are used to validate the MOPITT CO retrievals, along with routine samples from 2001 through 2006 from NOAA and the MOZAIC measurements from commercial aircraft. A significant positive bias, around 20% for total column CO, in MOPITT CO was found in the comparison to in situ measurements during 2006. Comparisons to the long-term records of measurements from NOAA and MOZAIC revealed an increasing bias in the V3 MOPITT CO retrievals over time. The impact of an instrumental drift is illustrated through retrieval simulations.

Emmons, L. K.↗

NASA NTRS2007

Measurements of Pollution in the Troposphere (MOPITT) Validation Exercises During Summer 2004 Field Campaigns over North America

Measurements of carbon monoxide (CO) made as part of three aircraft experiments during the summer of 2004 over North America have been used for the continued validation of the CO retrievals from the Measurements of Pollution in the Troposphere (MOPITT) instrument on board the Terra satellite. Vertical profiles measured during the NASA INTEX-A campaign, designed to be coincident with MOPITT overpasses, as well as measurements made during the COBRA-2004 and MOZAIC experiments, provided valuable validation comparisons. On average, the MOPITT CO retrievals are biased slightly high for these North America locations. While the mean bias differs between the different aircraft experiments (e.g., 7.0 ppbv for MOZAIC to 18.4 ppbv for COBRA at 700 hPa), the standard deviations are quite large, so the results for the three data sets can be considered consistent. On average, it is estimated that MOPITT is 7- 14% high at 700 hPa and 03% high at 350 hPa. These results are consistent with the validation results for the Carr, Colorado, Harvard Forest, Massachusetts, and Poker Flats, Alaska, aircraft profiles for "phase 2" presented by Emmons et al. (2004) and are generally within the design criteria of 10% accuracy.

Emmons, L. K.↗

NASA NTRS2005

TERRA/MOPITT Measurements of Tropospheric Carbon Monoxide Distributions in Support of INTEX

Interaction with the ongoing satellite measurements programs was an important goal of INTEX- A. The Terra/MOPITT instrument had been making global measurements of the tropospheric carbon monoxide (CO) distribution for 4 years, and was in a unique position to provide valuable support during the field campaign. Remote sensing of CO directly addressed the scientific questions motivating the IXTEX-A strategy and deployment, and measurement of this gas was rated as being mission critical. CO is an important trace gas in tropospheric chemistry due to its role in determining the atmospheric oxidizing capacity, as an ozone precursor, and as an indicator and tracer of both natural and anthropogenic pollution arising from incomplete combustion. The satellite perspective provided the more general temporal and spatial context to the aircraft and ground-based measurements during the subsequent scientific analysis. We proposed to build on the experience of supplying MOPITT data to previous field campaigns, such as TRACE-P. We provided expedited MOPITT data processing in near real-time, along with basic analysis of the measurements to indicate, where possible, the origin of the CO plumes that impacted the regions of flight operations and other in situ measurement activities. To ensure maximum exploitation of the satellite information, we will also had a scientist in the field to present and interpret the MOPITT data for the INTEX team, and to help ensure its utility in flight planning.

Edwards, D. P.↗

NASA NTRS2001

The aura mission: measurements, validation plan, and synergies with NDSC

Explore the source record for details and available documents.

atmospheric measurements aura mission validation N↗

NASA NTRS1994

Spectral signatures of polar stratospheric clouds and sulfate aerosol

Multiwavelength observations of Antarctic and midlatitude aerosol by the Cryogenic Limb Array Etalon Spectrometer (CLAES) experiment on the Upper Atmosphere Research Satellite (UARS) are used to demonstrate a technique that identifies the location of polar stratospheric clouds. The technique discussed uses the normalized area of the triangle formed by the aerosol extinctions at 925, 1257, and 1605/cm (10.8, 8.0, and 6.2 micrometers) to derive a spectral aerosol measure M of the aerosol spectrum. Mie calculations for spherical particles and T-matrix calculations for spheriodal particles are used to generate theoretical spectral extinction curves for sulfate and polar stratospheric cloud particles. The values of the spectral aerosol measure M for the sulfate and polar stratospheric cloud particles are shown to be different. Aerosol extinction data, corresponding to temperatures between 180 and 220 K at a pressure of 46 hPa (near 21-km altitude) for 18 August 1992, are used to demonstrate the technique. Thermodynamic calculations, based upon frost-point calculations and laboratory phase-equilibrium studies of nitric acid trihydrate, are used to predict the location of nitric acid trihydrate cloud particles.

Massie, S. T.↗

NASA NTRS1993

Revised reference model for nitric acid

A nearly global set of data on the nitric acid distribution was obtained for seven months by the Limb Infrared Monitor of the Stratosphere (LIMS) experiment on the Nimbus 7 spacecraft. The evaluation of the accuracy, precision, and resolution of these data is described, and a description of the major features of the nitric acid distributions is presented. The zonal mean for nitric acid is distributed in a stratospheric layer that peaks near 30 mb, with the largest mixing ratios occurring in polar regions, especially in winter.

Gille, J. C.↗

NASA NTRS1992

Concept for obtaining geostationary limb infrared measurements (GEOLIM) and their application

The scientific value and utility of including the capability for spectral earthlimb emission measurements in an advanced geostationary mission is discussed. These measurements are expected to support improved scientific understanding of the atmospheric region extending from the tropospheric cloud tops up to the thermosphere. Specific topics in the science of this region that are addressed by geostationary observations of spectral earthlimb emission are discussed. For many of these topics, nadir sounding measurements are either at great disadvantage or completely inappropriate. A promising approach for acquiring the earthlimb measurements, and a preliminary instrument concept are discussed.

Kumer, J. B.↗

NASA NTRS1992

The high resoultion dynamics limb sounder (HIRDLS): An instrument for the study of global change

Two groups, in the Unites States and the United Kingdom, proposed to further develop and use infrared limb scanning instruments in atmospheric studies from Earth Observing System (EOS). Subsequent review showed that the scientific objectives and basic measurement approaches were very similar, although there were differences in the proposed instrumentation. Their teams agreed to merge the two investigations into the High Resolution Dynamics Limb Sounder (HIRDLS). Under the resulting understanding, the two teams have combined, and will produce a single design to satisfy the scientific requirements of their investigations. The characteristics of limb scanning and earlier experiments are reviewed. The HIRDLS scientific objectives and requirements on the derived geophysical quantities are presented, and the way in which they drive the design of HIRDLS is indicated. A brief description of the HIRDLS instrument and a summary of HIRDLS capabilities follow.

Gille, J. C.↗

NASA NTRS1990

Validation of parameterization scheme for eddy diffusion from satellite data

The eddy diffusion coefficient K(yy) has been calculated usign LIMS for the months of December 1978 and January and February 1979. Two methods have been used. The first implements the suggestion made by Tung (1987) to parameterize the eddy transport as a diffusive process along isentropes. The second method integrates the equation relating the parcel displacements to the eddy velocity fields. The latter method uses a filtering on both space and time domains to isolate transients and is referred to as the 'spectral method'. Results from the first method are shown to be reliable only for quiescent periods, breaking down when the meridional gradient of potential vorticity is negligible. Results from the two methods are in agreement only for very disturbed conditions, when transience is readily isolated. It is concluded that the parameterizations suggested for eddy transport and calculated in this paper may be meaningful for quiet periods, but are not reliable for unsteady and very large amplitude disturbances.

Sassi, F.↗

NASA NTRS1990

Global trends

Measuring trends in ozone, and most other geophysical variables, requires that a small systematic change with time be determined from signals that have large periodic and aperiodic variations. Their time scales range from the day-to-day changes due to atmospheric motions through seasonal and annual variations to 11 year cycles resulting from changes in the sun UV output. Because of the magnitude of all of these variations is not well known and highly variable, it is necessary to measure over more than one period of the variations to remove their effects. This means that at least 2 or more times the 11 year sunspot cycle. Thus, the first requirement is for a long term data record. The second related requirement is that the record be consistent. A third requirement is for reasonable global sampling, to ensure that the effects are representative of the entire Earth. The various observational methods relevant to trend detection are reviewed to characterize their quality and time and space coverage. Available data are then examined for long term trends or recent changes in ozone total content and vertical distribution, as well as related parameters such as stratospheric temperature, source gases and aerosols.

Megie, G.↗

NASA NTRS1989

Revised reference model for nitric acid

Gille, J. C.↗

NASA NTRS1989

Spacecraft instrument calibration and stability

The following topics are covered: instrument degradation; the Solar Backscatter Ultraviolet (SBUV) Experiment; the Total Ozone Mapping Spectrometer (TOMS); the Stratospheric Aerosol and Gas Experiment 1 (SAGE-1) and SAGE-2 instruments; the Solar Mesosphere Explorer (SME) UV ozone and near infrared airglow instruments; and the Limb Infrared Monitor of the Stratosphere (LIMS).

Gille, J. C.↗

NASA NTRS1989

Information content of ozone retrieval algorithms

The algorithms are characterized that were used for production processing by the major suppliers of ozone data to show quantitatively: how the retrieved profile is related to the actual profile (This characterizes the altitude range and vertical resolution of the data); the nature of systematic errors in the retrieved profiles, including their vertical structure and relation to uncertain instrumental parameters; how trends in the real ozone are reflected in trends in the retrieved ozone profile; and how trends in other quantities (both instrumental and atmospheric) might appear as trends in the ozone profile. No serious deficiencies were found in the algorithms used in generating the major available ozone data sets. As the measurements are all indirect in someway, and the retrieved profiles have different characteristics, data from different instruments are not directly comparable.

Rodgers, C.↗

NASA NTRS1989

Trends in ozone profile measurements

From an examination of the agreements and differences between different satellite instruments, it is difficult to believe that existing satellite instruments determine upper stratospheric ozone much better than 4 pct.; by extension, it probably would require at least a 4 pct. change to be reliably detected as a change. The best estimates of the vertical profiles of ozone change in the upper stratosphere between 1979 and 1986 are judged to be those given by the two SAGE satellite instruments. SAGE-2 minus SAGE-1 gives a much lower ozone reduction than that given by the archived Solar Backscatter UV data. The average SAGE profiles of ozone changes between 20 and 50 degs north and between 20 and 50 degs south are given. The SAGE-1 and SAGE-2 comparison gives an ozone reduction of about 4 pct. at 25 km over temperate latitudes. Five ground based Umkehr stations between 36 and 52 degs north, corrected for the effects of volcanic aerosols, report an ozone reduction between 1979 and 1987 at Umkehr layer 8 of 9 + or - 5 pct. The central estimate of upper stratospheric ozone reduction given by SAGE at 40 km is less than the central value estimated by the Umkehr method at layer 8.

Johnston, H.↗

NASA NTRS1987

Atmospheric infrared emission of ClONO2 observed by a balloon-borne Fourier spectrometer

ClONO2 was observed in high-resolution infrared emission spectra obtained on Nov. 6, 1984, by a balloon-borne Fourier spectrometer. The observations took place near 0300 LT at a latitude of 35 N. Spectral simulations are used to determine the mixing ratios of ClONO2. This analysis incorporates line by line calculations and new ClONO2 cross sections measured in the laboratory at 223 K. The inferred mixing ratios of ClONO2 are 1.3 + or - 0.45 ppb and 0.98 + or - 0.35 ppb at 14 and 34 mbar. One-dimensional photochemical model predictions are compared to the observations. The ClONO2 mixing ratio at 34 mbar appears to be larger than theory, while there is agreement at 14 mbar.

Massie, S. T.↗

NASA NTRS1986

Inversion of limb radiance measurements - An operational algorithm

The limb radiance inversion radiometer (LRIR) and limb infrared monitor of the stratosphere (LIMS) experiments aboard the Nimbus 6 and 7 spacecraft have made observations of infrared emission by CO2, O3, H2O, HNO3, and NO2 at the earth's limb. This paper describes a method by which such measurements can be inverted to give vertical distributions of temperature and mixing ratios as functions of pressure. The simple and efficient approach was successfully applied to the LRIR data and subsequently in the initial assessment of the LIMS data. Inversion of synthetic data indicates the size of the errors to be expected as a result of the assumptions and instrumental errors. Retrievals of measured LIMS radiances are shown as examples and compared to in situ observations. The differences are comparable to those obtained with the more complex retrieval scheme used to process the LIMS archival products. Some problems are noted.

Bailey, P. L.↗

NASA NTRS1985

Transport of trace species deduced from LIMS observations

One of the critical problems in the middle atmosphere at this time is understanding the interaction between atmospheric motions and photochemistry, and the way in which these two processes maintain the distributions of photochemically active species such as ozone. Recent work has shown that a great deal can be learned by considering the zonally averaged distributions and transports, i.e., working in the latitude-altitude plane. This 2-dimensional approach has been used in the past in Eulerian formation. Recent work (DUNKERTON, 1978) has shown that formulating the transport problems in terms of the residual mean circulation, which has similarity to the Lagrangian mean motion, results in a more physical picture of the way in which the transport takes place. Here, data from the Limb Infrared Monitor of the Stratosphere (LIMB) experiment are used to investigate how well the residual mean formulation works with real data, in the sense of asking how well the predicted ozone changes match those in regions of the lower stratosphere in which chemical changes may be neglected. This allows a test of the approximations that are made, and of the strengths and weaknesses of this approach to transport calculation.

Gille, J. C.↗