Infrared Radiometer Research Articles

High-Resolution Airborne Infrared Measurements of Ocean Skin Temperature

Airborne measurements of ocean skin temperature T/sub s/ are presented from the Coupled Boundary Layers, Air-Sea Transfer in Low Winds (CBLAST-Low) Pilot Experiment in August 2001 off Martha's Vineyard, MA. We used an infrared (IR) camera with a spatial resolution of 1 m or less and temperature resolution of roughly 0.02/spl deg/C. Using subframe sampling of the IR imagery, we achieve lower noise and higher spatial resolution than reported by previous investigators using IR radiometers. Fine-scale maps of T/sub s/ exhibit horizontal variability over spatial scales ranging from O(10 km) down to O(1 m) that are related to atmospheric and subsurface phenomena under low to moderate wind conditions. Based on supporting measurements of wind and waves, we identify coherent ramp-like structures in T/sub s/ with stratification breakdown and meandering streaky features with internal waves. Regional maps of T/sub s/ show the standard deviation for the region is /spl plusmn/1.04/spl deg/C, while the meridional and zonal variability is 0.23/spl deg/C /spl middot/ km/sup -1/ and 0.27/spl deg/C /spl middot/ km/sup -1/, respectively. This temperature variability results in meridional and zonal scalar heat flux variability of 7.0 W /spl middot/ m/sup -2/ /spl middot/ km/sup -1/ and 7.6 W /spl middot/ m/sup -2/ /spl middot/ km/sup -1/, respectively. Our results demonstrate the potential for airborne IR imagery accompanied by high-quality ocean data to identify T/sub s/ features produced by subsurface circulation.

D313 運動する人体の動的特性とその解析

A visual digital recorder system (DVR) is widely used to visualize and analyze the dynamic image of moving body. The simultaneous instrumentation system of the DVR and infrared radiometer (IR) was applied to study two-dimensional moving images of the human body under walking and Gymnastic training. Dynamic behaviors of human body segments like location velocity and force are measured and analyzed by DVR, IR and the personal computer. Single-and multi-flash imaging methods of the human body were visualized and evaluated by using the multi flash motion recorder. Lastly, a fluctuation performance of the moving human body was quantitatively obtained and expressed in form of frequency, power spectrum density and coherence coefficient

On the distribution and variability of water vapour in the middle atmosphere of Venus

Water is a key constituent of every planetary environment, and on Venus its abundance, distribution and temporal behaviour are crucial for understanding greenhouse warming, cloud formation and dissipation, volcanism, and atmospheric evolution. Many telescopic and spacecraft-based observations of atmospheric water vapour on Venus have been made, but are inconclusive about its role as a component of the current climate system on the planet. The data suggest that H 2O may be well mixed in the lower atmosphere, but highly variable in and near the cloud layers, and probably also at the thermospheric levels where dissociation and loss occur. The details of the middle atmosphere variability, how significant it is, and the processes responsible, remain controversial. In particular, the Pioneer Venus Infrared Radiometer found a large ‘wet patch’, a localized region where the water vapour mixing ratio is generally enhanced by one to two orders of magnitude over the global mean, occurring at low latitudes in the mid-afternoon, that has not been confirmed by other observations. If it is real, the presently unknown mechanism that produces it may be an important part of the water cycle in the Venusian atmosphere. Here we reconsider this problem, and some of the possible processes that may be involved, prior to the expected acquisition of relevant new data by Venus Express and the Venus Climate Orbiter.

Water vapor abundance in Venus' middle atmosphere from Pioneer Venus OIR and Venera 15 FTS measurements

The Pioneer Venus Orbiter Infrared Radiometer and Venera 15 Fourier Transform Spectrometer observations of thermal emission from Venus' middle atmosphere between 10° S and 50° N have been independently re-analyzed using a common method to determine global maps of temperature, cloud optical depth, and water vapor abundance. The spectral regions observed include the strong 15 μm carbon dioxide band and the 45 μm fundamental rotational water band. The different spatial and spectral resolutions of the two instruments have necessitated the development of flexible analysis tools. New radiative transfer and retrieval models have been developed for this purpose based on correlated- k absorption tables calculated with up-to-date spectral line data. The common analysis of these two sets of observations has hence been possible for the first time. From the PV OIR observations, the cloud-top unit optical depth pressure showed a minimum of ∼ 110 ± 10 mbars in the evening equatorial region and a maximum of ∼ 160 ± 12 mbars in the morning mid-latitude regions. From the Venera 15 FTS spectra, the cloud-top pressure was found to increase from morning values of ∼ 120 ± 10 to 200 ± 30 mbars in the late afternoon/early evening region. The cloud-top water vapor abundances observed by the PV OIR instrument were found to fluctuate from 10 ± 5 ppm at night up to 90 ± 15 ppm in the equatorial cloud-top region shortly after the sub-solar point. The mean Venera 15 FTS water vapor abundances were found to be 12 ± 5 ppm with only a slight enhancement over the equatorial latitude bands and no clear day–night distinction. The common analysis of these two sets of observations broadly validates previously published individual findings. The differences in the retrieved atmospheric state can no longer be attributed to radiative transfer modeling bias and suggest significant temporal variability in the middle atmosphere of Venus.

Experimental infrared-radiometric investigations of stress variations on a borehole face in a model of the soil mass

A procedure for, and results of experimental investigations performed to substantiate the effectiveness of the method of infrared (IR) radiation in diagnosing changes in the stress state of soils over time are presented. The construction of a “large-scale” bench is described for the alternating loading of a relatively large (of the order of 0.35 m3) volume of soil. Variations in the stress state over time in the near-face zone of a “borehole,” which is arranged in a model of the soil mass, are recorded using synchronous recordings of signals from an IR radiometer and load-cell strain gages. The elastic nature of stress variations on the face of the borehole in an unsaturated sandy soil is revealed during alternating-sign stress variations “at infinity.” It is indicated that data derived from noncontact IR measurements will make it possible to record accurately moments of jumpwise stress variations in the soil “mass,” and evaluate their intensity.

Spatial and angular responsivity measurements of photoconductive HgCdTe LWIR radiometers

Several newly developed large area photoconductive (PC) mercury cadmium telluride (HgCdTe) radiometers have been tested for spatial and angular responsivity for the purpose of determining what mode of operation (or radiometric quantity) could provide the lowest measurement uncertainty. An infrared (IR) test facility has been developed for the characterization of long wavelength IR (LWIR) detectors and radiometers for spatial response uniformity in power measurement mode and angular responsivity in both power and irradiance measurement modes. We have measured 34% to 53% spatial response non-uniformities and 1.5% to 10.5% changes in angular power reponsivity at different beam positions within the f/4 field-of-view (FOV) of the PC HgCdTe radiometers. The lowest responsivity uncertainty is achieved when these non-uniform radiometers are operated in irradiance measurement mode, where the incident uniform field of radiation averages out the detector's non-uniformity related uncertainties. The angular response deviation from the cosine function within the 16° FOV of the radiometers dominates the uncertainty budget for irradiance responsivity measurements in the 3 µm to 20 µm sensitivity range of these working standard devices.

Sulfur dioxide flux estimation from volcanoes using Advanced Spaceborne Thermal Emission and Reflection Radiometer—a case study of Miyakejima volcano, Japan

A method is described for estimating the two-dimensional spatial distribution of volcanic SO 2 using thermal infrared image data acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). The author proposes a new method to estimate wind velocity and plume height using an along-track stereoscopic pair image. Volcanic SO 2 flux can be estimated from the spatial distribution of SO 2 and wind velocity. Since ASTER has both the Thermal Infrared Radiometer (TIR) and stereoscopic viewing function in the along-track direction, the volcanic SO 2 flux can be estimated from the ASTER data alone. These methods are applied to the Miyakejima volcano, Japan. The SO 2 flux derived from ASTER is around 5×10 4 ton/day (580 kg s −1), which is slightly larger than the value derived from COSPEC. The plume height estimation error may cause this disagreement because the SO 2 estimation procedure is very sensitive to the plume height.

Occurrence of ozone anomalies over cloudy areas in TOMS version-7 level-2 data

Abstract. This study investigates anomalous ozone distributions over cloudy areas in Nimbus-7 (N7) and Earth-Probe (EP) TOMS version-7 data and analyzes the causes for ozone anomaly formation. A 5°-longitude by 5°-latitude region is defined to contain a Positive Ozone Anomaly (POA) or Negative Ozone Anomaly (NOA) if the correlation coefficient between total ozone and reflectivity is > 0.5 or < -0.5. The average fractions of ozone anomalies among all cloud fields are 31.8 ± 7.7% and 35.8 ± 7.7% in the N7 and EP TOMS data, respectively. Some ozone anomalies are caused by ozone retrieval errors, and others are caused by actual geophysical phenomena. Large cloud-height errors are found in the TOMS version-7 algorithm in comparison to the Temperature Humidity Infrared Radiometer (THIR) cloud data. On average, cloud-top pressures are overestimated by ~200 hPa (THIR cloud-top pressure < 200 hPa) for high-altitude clouds and underestimated by ~150 hPa for low-altitude clouds (THIR cloud-top pressure > 750 hPa). Most tropical NOAs result from negative errors induced by large cloud-height errors, and most tropical POAs are caused by positive errors due to intra-cloud ozone absorption enhancement. However, positive and negative errors offset each other, reducing the ozone anomaly occurrence in TOMS data. Large ozone/reflectivity slopes for mid-latitude POAs show seasonal variation consistent with total ozone fluctuation, indicating that they result mainly from synoptic and planetary wave disturbances. POAs with an occurrence fraction of 30--60% occur in regions of marine stratocumulus off the west coast of South Africa and off the west coast of South America. Both fractions and ozone/reflectivity slopes of these POAs show seasonal variations consistent with that in the tropospheric ozone. About half the ozone/reflectivity slope can be explained by ozone retrieval errors over clear and cloudy areas. The remaining slope may result from there being more ozone production because of rich ozone precursors and higher photolysis rates over high-frequency, low-altitude clouds than in clear areas. Ozone anomalies due to ozone retrieval errors have important implications in TOMS applications such as tropospheric ozone derivation and analysis of ozone seasonal variation.

Upper tropospheric ozone derived from the cloud slicing technique: Implications for large‐scale convection

This study evaluates the spatial distributions and seasonal cycles in upper tropospheric ozone (pressure range 200–500 hPa) from low to high latitudes (60°S to 60°N) derived from the satellite retrieval method called “cloud slicing.” The cloud slicing method determines ozone profile information in the troposphere by combining colocated measurements of cloud top pressure and above‐cloud column ozone. Measurements of Nimbus 7 Total Ozone Mapping Spectrometer (TOMS) above‐cloud column ozone and Nimbus 7 Temperature Humidity Infrared Radiometer (THIR) cloud top pressure during 1979–1984 were merged to derive upper tropospheric ozone. Because of large footprint measurements from TOMS (∼100 km diameter on average), upper tropospheric ozone derived from cloud slicing coincides with large‐scale convection events. These events are not necessarily representative of average atmospheric conditions in regions near and poleward of the tropospheric wind jets (around ±30° latitude), especially in winter and spring seasons when dynamical wave activity in the troposphere and lower stratosphere is most intense. The cloud slicing method with Nimbus 7 geometry in any case provides a unique opportunity to investigate the behavior of upper tropospheric ozone under condition of intense broad‐scale convection. In the tropics the measured upper tropospheric ozone shows year‐round enhancement in the Atlantic region and evidence of a possible semiannual variability. Outside the tropics, upper tropospheric ozone from cloud slicing shows greatest abundance in winter and spring seasons in both hemispheres with largest variance and largest amounts in the northern hemisphere. This seasonal cycle behavior under conditions of intense convection is different from general ozonesonde climatology which shows instead upper tropospheric ozone maximizing around early to middle summer months. The seasonal cycles and spatial characteristics in upper tropospheric ozone from cloud slicing are similar to lower stratospheric ozone. It is suggested that the large‐scale convection events with cloud slicing coincide with an occurrence of stratosphere‐troposphere exchange (STE).

A Field Intercomparison Technique to Improve the Relative Accuracy of Longwave Radiation Measurements and an Evaluation of CASES-99 Pyrgeometer Data Quality

Abstract Techniques for improving the relative accuracy of longwave radiation measurements by a set of pyrgeometers [the Eppley Laboratory Precision Infrared Radiometer (Model PIR)] are presented using 10 PIRs from the 1999 Cooperative Atmosphere–Surface Exchange Study (CASES-99). The least squares–based optimization technique uses a field intercomparison (i.e., a time period during which all the PIRs were upward looking and set up side by side) to determine a set of optimization coefficients for each PIR. For the 10 CASES-99 PIRs, the optimization technique improved the standard deviation of the difference of downwelling irradiance between the PIRs from ±0.75 to ±0.4 W m−2 (for nighttime data). In addition to presenting the optimization method, various PIR data quality checks are outlined and applied to the PIR data. Based on these quality checks, the measured case and dome temperatures of the CASES-99 PIRs were all reasonable. Using the 10 CASES-99 PIRs, simple estimates of the average nighttime net rad...

AIRS/AMSU/HSB on the aqua mission: design, science objectives, data products, and processing systems

The Atmospheric Infrared Sounder (AIRS), the Advanced Microwave Sounding Unit (AMSU), and the Humidity Sounder for Brazil (HSB) form an integrated cross-track scanning temperature and humidity sounding system on the Aqua satellite of the Earth Observing System (EOS). AIRS is an infrared spectrometer/radiometer that covers the 3.7-15.4-/spl mu/m spectral range with 2378 spectral channels. AMSU is a 15-channel microwave radiometer operating between 23 and 89 GHz. HSB is a four-channel microwave radiometer that makes measurements between 150 and 190 GHz. In addition to supporting the National Aeronautics and Space Administration's interest in process study and climate research, AIRS is the first hyperspectral infrared radiometer designed to support the operational requirements for medium-range weather forecasting of the National Ocean and Atmospheric Administration's National Centers for Environmental Prediction (NCEP) and other numerical weather forecasting centers. AIRS, together with the AMSU and HSB microwave radiometers, will achieve global retrieval accuracy of better than 1 K in the lower troposphere under clear and partly cloudy conditions. This paper presents an overview of the science objectives, AIRS/AMSU/HSB data products, retrieval algorithms, and the ground-data processing concepts. The EOS Aqua was launched on May 4, 2002 from Vandenberg AFB, CA, into a 705-km-high, sun-synchronous orbit. Based on the excellent radiometric and spectral performance demonstrated by AIRS during prelaunch testing, which has by now been verified during on-orbit testing, we expect the assimilation of AIRS data into the numerical weather forecast to result in significant forecast range and reliability improvements.

Component level prediction versus system level measurement of SABER relative spectral response

A 10-channel infrared (1.25-17.24 µm wavelength) radiometer known as SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) is one of four experiments that will fly on the TIMED (Thermosphere, Ionosphere, Mesosphere, Energetics, and Dynamics) mission that was successfully launched on 7 December 2001. Theoretical models of the relative spectral response (RSR) for each SABER channel were developed during the design and build of the instrument. The RSR calculations were then refined using a component level technique where theoretical predictions of filter transmittance were replaced with measurements from filter witness samples. During SABER ground calibration, full system measurements of RSR were performed using a Michelson step-scan interferometer to present an interferometrically modulated infrared source to the instrument with the resultant interferogram recorded by the instrument detectors. Fourier transform of this interferogram and correction of the resulting spectrum for the spectral output of the interferometer and the transmittance of any intervening optics provide a measurement of the system level RSR. We compare the full system level measurements with the theoretical and component level RSR predictions for both in-band and out-of-band spectral regions. Our results show that the system level method for determining RSR provides the clearest picture of the instrument's spectral properties.

Study on variation of thermal image by infrared radiometer influenced by fluctuations of environmental factors

The infrared radiometer (IR) displays the radiation temperature distribution. Frequently, thermal images on a CRT display fluctuate and those radiation temperatures cannot be measured correctly. Therefore, we are frequently faced with the difficult problem of evaluating the detection limits on surface and internal flaws in construction and underground structures, and so on. Those difficulties are considered to be due to fluctuations of the meteorological and environmental factors, mainly influenced by solar radiation, wind velocity, atmospheric temperature, and so on. Our experimental study clarifies the relation between variations of the thermal images on the CRT of IR display and the environmental factors using an analysis of power spectral density.

A System for Routinely Monitoring Radiometric Sea Surface Temperature

A fully self contained, automated thermal infrared radiometer system is presented. The unit is mounted on a tourist ferry (the MV 2001), which travels between Townsville (Queensland, Australia) and Kelso Reef, on the Great Barrier Reef (a distance of about 80 km). The system collects a mid-morning and a mid-afternoon transect of radiometric sea surface temperature for ground truthing satellite data. The system was rigorously calibrated to a standard deviation of 0.1°C, using a novel technique.

Proposal of quantitative temperature measurement using two-color technique combined with several infrared radiometers having different detection wavelength bands

Infrared thermography has been widely used to visualize a two-dimensional temperature field for various engineering applications. However, in general, conventional infrared thermography cannot directly be applied to quantitative temperature measurement on glossy metal surfaces under near-ambient conditions, because of the severe influ- ence of the reflected energy incident from the surroundings on the mea- surement. When it is necessary to measure the temperature quantita- tively, an appropriate calibration involving complicated procedures must be performed. In this paper, therefore, a new technique of measuring temperature is proposed for near-ambient conditions, by combining si- multaneously several infrared radiometers having different detection wavelength bands to enable a two-color technique, which does not re- quire any temperature calibrations. The sensors concerned have a se- lective wavelength band of several micrometers in width in the range of 2 to 13 mm. The applicability of the method, including a series of proposed equations, has been confirmed by an investigation; the numerical simu- lation presented merely allows a parametric study of how the result var- ies for different values of emissivity corresponding to a pair of infrared radiometers. An experimental investigation is also performed to estimate or correct the measurement error pertaining to the present technique. This technique has the feature that a two-dimensional temperature field can be evaluated quantitatively, nondestructively, and simultaneously at each picture element without presuming any emissivity and reflectivity, even though the object has a complicated shape; so that it may be useful in various medical or engineering applications. © 2001 Society of Photo-

反射率に基づく衛星搭載可視近赤外放射計の代替校正のオンサイト機器校正による精度向上

反射率に基づく衛星搭載可視近赤外放射計の代替校正のオンサイト機器校正による精度向上

Early results from the vicarious calibration of Terra/ASTER/SWIR

Abstract A preliminary vicarious calibration with field campaigns is conducted together with an evaluation of noise equivalent reflectance and stripe noise with a homogeneous scene of SWIR(Shortwave Infrared Radiometer) onboard Terra satellite. A few percent of difference between the estimated and the actual radiance is confirmed through the vicarious calibration and several abnormal detectors were found together with a small amount of horizontal stripe.

On the proposal of quantitative temperature measurement by using three-color technique combined with several infrared sensors having different detection wavelength bands

We developed the previous infrared sensing technique, the two-color technique, to establish further a more general technique to measure the temperature quantitatively under near-ambient conditions. The quantitative temperature measurement, three-color technique, was newly proposed by combining three kinds of infrared radiometers having different detection wavelength bands. The measurement can also be done by adding three infrared filters to one infrared radiometer. The radiometers have a selective detection wavelength band of several μm in width which is in the range of 2–13 μ m. The method was confirmed using numerical simulation to allow a parametric study of how the result varies for different values of emissivity corresponding to the respective infrared radiometers. An experimental investigation was also performed to evaluate the measurement error and the adaptability of the technique. As this technique has a feature that can perform quantitative temperature measurement for objective surfaces at each picture element without presuming any emissivity, reflectivity and ambient conditions, there is a possibility that the technique will be useful for various medical or engineering disciplines.

Short-wave infrared transfer radiometer for the calibration of the Moderate-Resolution Imaging Spectrometer and the Advanced Spaceborne Thermal Emission and Reflection Radiometer

A short-wave infrared (700-2500-nm) radiometer has been designed and built to calibrate and cross calibrate spherical-integrating sources used in the calibration of satellite sensors residing on NASA's Earth Observing System platforms. We describe the design, predicted and measured performance, and calibration of the transfer radiometer.

A Detection of Water Ice on Jupiter with Voyager IRIS

Possible water ice spectral signatures have been detected on Jupiter using Voyager Infrared Interferometer Spectrometer and Radiometer (IRIS) spectra taken near closest approach of the Voyager 1 and 2 missions. Comparison with simultaneous imaging data shows that these IRIS footprints approximately correspond to locations on the planet where deep convection is suspected. Of the sample of 7500+ spectra, approximately 1% show a water ice absorption feature near 44 μm. The infrared optical depths of the absorption features, between 0.18 and 0.44, indicate that large amounts of ice particles need not be present to produce the observed spectral signature. The water ice clouds would have visible optical depths on the order of unity and would not be distinguishable above a thick ammonia cloud deck, which can have much larger visible optical depths. These thin clouds yield about 1 precipitable micrometer of water, comparable to Martian Tharsis Ridge clouds.