Engineering topics

Valero, Francisco P. J.

Publications and source records attributed to Valero, Francisco P. J..

At least 19 records

NASA NTRS2005

Radiation Studies in Support of the CRYSTAL-FACE Project

As proposed, we successfully completed radiometric observations aboard the ER-2 and WB-57 platforms during the field phase of the CRYSTAL-FACE campaign. Quick look plots of the data were immediately archived after the missions and quality-controlled and completely processed find data products were archived in a timely manner to the CRYSTAL-FACE data archive. The specific radiometric instrumentation operated aboard the two NASA airborne platforms is summarized.

Valero, Francisco P. J.↗

NASA NTRS2003

[Results for SHEBA/FIRE]

The Atmospheric Research Laboratory's Radiation Measurement System (RAMS) was on the NCAR C-130 aircraft in May and July 1998, collecting radiometric data on the science flights conducted in the vicinity of the Surface Heat Budget of the Arctic Ocean (SHEBA) ship. These measurements were part of the FIRE Arctic Cloud Experiment (FIRE ACE). Analysis of some of the data focused on the absorption, reflection, and transmittance of Arctic clouds, especially compared to model results. In order to assess the absorption of solar radiation by the clear and cloudy atmosphere in the Arctic the measurements from the radiometers were combined in pairs of above-cloud segments and below-cloud segments. To get these pairs, the data for all sixteen of the flights (8 in May and 8 in July) were examined for occurrences of low-altitude segments in proximity to high-altitude segments. The low-altitude data are then treated as measurements of the bottom of a layer and the high-altitude data are taken as measurements of the top of the layer. With measurements of the upwelling and downwelling irradiances above and below a layer one can determine the reflectance, transmittance, and absorptance of the layer. Attachment: Doelling, D.R., P. Minnis, D.A. Spangenberg, V. Chakrapani, A. Mahesh, S.K. Pope, and F.P.J. Valero, Cloud radiative forcing at the top of the atmosphere during FIRE ACE derived from AVHRR data, J. Geophys. Res. 106, 15,279-15,296,2001. Minnis, P., D.R. Doelling, D.A. Spangenberg, A. Mahesh, S.K. Pope, and F.P.J. Valero, AVHRR-derived cloud radiative forcing over the ARM NSA and SHEBA site during FIRE ACE, abstract submitted to the ARM Science Team Meeting, San Antonio, TX, M a . 13-17,2000. Pope, S.K., and F.P.J. Valero, Measured and modeled radiometric fluxes in the Arctic during FIRE-ACE, presented as a poster at the American Geophysical Union meeting, San Francisco, CA, Dec. 13-17, 1999. Pope, S.K., and F.P.J. Valero, Measured and modeled radiometric fluxes in the Arctic during FIRE-ACEy paper presented at SHEBA/FIRE Workshop, National Center for Atmospheric Research, Boulder, Colo., Apr. 17-20,2000.

Valero, Francisco P. J.↗

NASA NTRS2002

Comparison of ScaRaB, GOES 8, Aircraft, and Surface Observations of the Absorption of Solar Radiation by Clouds

Data obtained by the Scanner for Radiation Budget (ScaRaB) instrument on the Meteor 3 satellite have been analyzed and compared to satellite (GOES 8), aircraft (Radiation Measurement System, RAMS), and surface (Baseline Solar Radiation Network (BSRN), Solar and Infrared Observations System (SIROS), and RAMS) measurements of irradiance obtained during the Atmospheric Radiation Measurements Enhanced Shortwave Experiment (ARESE). It is found that the ScaRaB data covering the period from March 1994 to February 1995 (the instrument's operational lifetime) indicate excess absorption of solar radiation by the cloudy atmosphere in agreement with previous aircraft, surface, and GOES 8 results. The full ScaRaB data set combined with BSRN and SIROS surface observations gives an average all-sky absorptance of 0.28. The GOES 8 data set combined with RAMS surface observations gives an average all-sky absorptance of 0.26. The aircraft data set (RAMS) gives a mean all-sky absorptance of 0.24 (for the column between 0.5 and 13 km).

Pope, Shelly K.↗

NASA NTRS2002

Simulation and Correction of Triana-Viewed Earth Radiation Budget with ERBE/ISCCP Data

This paper describes the simulation of the earth radiation budget (ERB) as viewed by Triana and the development of correction models for converting Trianaviewed radiances into a complete ERB. A full range of Triana views and global radiation fields are simulated using a combination of datasets from ERBE (Earth Radiation Budget Experiment) and ISCCP (International Satellite Cloud Climatology Project) and analyzed with a set of empirical correction factors specific to the Triana views. The results show that the accuracy of global correction factors to estimate ERB from Triana radiances is a function of the Triana position relative to the Lagrange-1 (L1) or the Sun location. Spectral analysis of the global correction factor indicates that both shortwave (SW; 0.2 - 5.0 microns) and longwave (LW; 5 -50 microns) parameters undergo seasonal and diurnal cycles that dominate the periodic fluctuations. The diurnal cycle, especially its amplitude, is also strongly dependent on the seasonal cycle. Based on these results, models are developed to correct the radiances for unviewed areas and anisotropic emission and reflection. A preliminary assessment indicates that these correction models can be applied to Triana radiances to produce the most accurate global ERB to date.

Huang, Jian-Ping↗

NASA NTRS1998

Absorption of Solar Radiation by the Cloudy Atmosphere: Further Interpretations of Collocated Aircraft Measurements

We have extended the interpretations made in two prior studies of the aircraft shortwave radiation measurements that were obtained as part of the Atmospheric Radiation Measurements (ARM) Enhanced Shortwave Experiments (ARESE). These extended interpretations use the 500 nm (10 nm bandwidth) measurements to minimize sampling errors in the broadband measurements. It is indicated that the clouds present during this experiment absorb more shortwave radiation than predicted by clear skies and thus by theoretical models, that at least some (less than or equal to 20%) of this enhanced cloud absorption occurs at wavelengths less than 680 nm, and that the observed cloud absorption does not appear to be an artifact of sampling errors nor of instrument calibration errors.

Cess, R. D.↗

NASA NTRS1997

Absorption of Solar Radiation by the Cloudy Atmosphere Interpretations of Collocated Aircraft Measurements

As part of the Atmospheric Radiation Measurement (ARM) Enhanced Shortwave Experiment (ARESE), we have obtained and analyzed measurements made from collocated aircraft of the absorption of solar radiation within the atmospheric column between the two aircraft. The measurements were taken during October 1995 at the ARM site in Oklahoma. Relative to a theoretical radiative transfer model, we find no evidence for excess solar absorption in the clear atmosphere and significant evidence for its existence in the cloudy atmosphere. This excess cloud solar absorption appears to occur in both visible (0.224-0.68 microns) and near-infrared (0.68-3.30 microns) spectral regions, although not at 0.5 microns for the visible contribution, and it is shown to be true absorption rather than an artifact of sampling errors caused by measuring three-dimensional clouds.

Valero, Francisco P. J.↗

NASA NTRS1997

Radiative Effects of Aerosols

Valero, Francisco P. J.↗

NASA NTRS1996

Radiative Effects of Aerosols

During the Atlantic Stratocumulus Transition Experiment (ASTEX) in June 1992, two descents in cloud-free regions allowed comparison of the change in aerosol optical depth as determined by an onboard total-direct-diffuse radiometer (TDDR) to the change calculated from measured size-resolved aerosol microphysics and chemistry. Both profiles included a pollution haze from Europe but the second also included the effect of a Saharan dust layer above the haze. The separate contributions of supermicrometer (coarse) and submicrometer (fine) aerosol were determined and thermal analysis of the pollution haze indicated that the fine aerosol was composed primarily of a sulfate/water mixture with a refractory soot-like core. The soot core increased the calculated extinction by about 10% in the most polluted drier layer relative to a pure sulfate aerosol but had significantly less effect at higher humidities. A 3 km descent through a boundary layer air mass dominated by pollutant aerosol with relative humidities (RH) 10-77% yielded a close agreement between the measured and calculated aerosol optical depths (550 nm) of 0.160 (+/- 0.07) and 0. 157 (+/- 0.034) respectively. During descent the aerosol mass scattering coefficient per unit sulfate mass varied from about 5 to 16 m(exp 2)/g and primarily dependent upon ambient RH. However, the total scattering coefficient per total fine mass was far less variable at about 4+/- 0.7 m(exp 2)/g. A subsequent descent through a Saharan dust layer located above the pollution aerosol layer revealed that both layers contributed similarly to aerosol optical depth. The scattering per unit mass of the coarse aged dust was estimated at 1.1 +/- 0.2 m(exp 2)/g. The large difference (50%) in measured and calculated optical depth for the dust layer exceeded measurements.

Valero, Francisco P. J.↗

NASA NTRS1995

Direct Observations of Excess Solar Absorption by Clouds

Aircraft measurements of solar flux in the cloudy tropical atmosphere reveal that solar absorption by clouds is anomalously large when compared to theoretical estimates. The ratio of cloud forcing at an altitude of 20 kilometers to that at the surface is 1.58 rather than 1.0 as predicted by models. These results were derived from a cloud radiation experiment in which identical instrumentation was deployed on coordinated stacked aircraft. These findings indicate a significant difference between measurements and theory and imply that the interaction between clouds and solar radiation is poorly understood.

Pilewskie, Peter↗

NASA NTRS1993

Optical properties of cirrus derived from airborne measurements during FIRE IFO 2

The Radiation Measurement System (RAMS) on board the NASA ER-2 was used to acquire several optical parameters of interest during the FIRE Cirrus IFO 2. In this abstract we present results from the 26 Nov. IFO when the ER-2 flew over the Coffeyville airport hub site. We show retrieved optical thickness and cloud temperature, along with optical thickness obtained from RAMS instruments on the NCAR Sabreliner and at the surface site B. Independent retrieval of optical thickness, from the ER-2 and at the surface, are in agreement during the overpasses. Cirrus optical depths, derived from each platform, ranged between 1 and 2.

Valero, Francisco P. J.↗

NASA NTRS1993

Ground-based passive remote sensing during FIRE IFO 2

During the FIRE Cirrus IFO II, a set of passive radiometers were deployed at the Coffeyville, Kansas, Hub, site B, to compliment the Radiation Measurement System (RAMS) on board the NASA ER-2 and NCAR Sabreliner. The following three instruments were used at the surface: Narrow-field-of View IR Radiometer (NFOV); Total-Direct-Diffuse Radiometer (TDDR); and Near-Infrared Spectroradiometer (NIRS).

Pilewskie, Peter↗

NASA NTRS1993

Airborne brightness temperature measurements of the polar winter troposphere as part of the Airborne Arctic Stratosphere Experiment 2 and the effect of brightness temperature variations on the diabatic heating in the lower stratosphere

In this paper we report radiometric measurements of tropospheric brightness temperatures obtained during the AASE 2 experiment. These measurements represent the first attempt to characterize effective radiative temperatures as seen from above the troposphere during the Arctic winter. The reported measurements include brightness temperatures at 6.7 and 10.5 microns as seen from the NASA DC-8 aircraft flying at about 11 km altitude. We also present radiative transfer calculations to estimate the effect of tropospheric brightness temperature on the lower stratospheric heating rates. Because of the recent massive eruption of the Pinatubo volcano, we also discuss the effects of a volcanic aerosol layer. It is concluded that small particles like the volcanic aerosol or polar stratospheric clouds (PSCs) type 1 do not affect stratospheric heating rates by much; on the other hand, larger particles, PSCs types 2 and 3, may have significant effects on heating rates and consequently on dynamics of the lower stratosphere. The dynamical effects of local stratospheric temperature variations are briefly discussed.

Valero, Francisco P. J.↗

NASA NTRS1993

The radiative budgets of a tropical mesoscale convective system during the EMEX-STEP-AMEX experiment. I - Observations. II - Model results

The spatial radiation heating budget associated with tropical mesoscale convective systems (MCSs) is studied and the change of this heating/budget throughout the life cycle of such a cloud system is investigated. The movements of an EMEX 9 cloud cluster are described. The vertical structure of the cluster contains two types of imbedded convection: an upright vertical structure and a pronounced rearward slope with vertical extent of 14.5 km or more and a horizontal scale of about 40 km. The cloud base and cloud top altitude in the stratiform region are of the order of 4.8 km and 15-16 km, respectively. The upward and downward solar flux profiles suggest very little solar heating in these regions. A tropical MCS that occurred during the EMEX Mission 9 is simulated, and the simulation is shown to broadly agree with the observations. The simulation results, which are reported in detail, show how tropical mesoscale cloud systems provide an effective radiative heat source for the tropical atmosphere.

Wong, Takmeng↗

NASA NTRS1993

An Imaging Interferometer for Terrestrial Remote Sensing

A prototype imaging interferometer called DASI (digital array scanned interferometer) is under development at our laboratories. Our objective is to design an instrument for remote sensing of Earth's atmosphere and surface. This paper describes the unusual characteristics of DASIs which make them promising candidates for ground and aircraft-based terrestrial measurements. These characteristics include superior signal-to-noise, design simplicity and compactness, relative to dispersion based imaging spectrometers. Perhaps one of the most notable features of DASIs is their ability to acquire an entire interferogram simultaneously without any moving optical elements. We also describe selected laboratory and ground based field measurements using the prototype DASI. A CCD detector array was placed at the DASI detector plane for wavelength coverage from 0.4 to 1.0 micron. A NICMOS MCT detector was used for coverage from 1.1 to 2.2 micron. The DASI was configured to have a spectral resolution of about 300 1/cm, a spatial field of view of 5 degrees, and a constant number of transverse spatial elements (detector dependent) for each exposure frame. Frame exposure rates were up to 0.6 Hz with the potential to achieve 5 Hz. Image cube measurements of laboratory targets and terrestrial scenes were obtained by multiple frame scanning over the field of view. These data sets reveal the potential science yields from obtaining simultaneous high resolution spatial and spectral information.

Hammer, Philip D.↗

NASA NTRS1992

Radiative effects of the smoke clouds from the Kuwait oil fires

The radiative effects of the smoke from the Kuwait oil fires were assessed by measuring downwelling and upwelling solar flux, as well as spectral solar extinction beneath, above, and within the smoke plume. Seven radiation flight missions were undertaken between May 16 and June 2, 1991, to characterize the plume between the source region in Kuwait and approximately 200 km south, near Manama, Bahrain. Results are presented from one flight representative of conditions of the composite plume. On May 18, 1991, in a homogeneous, well-mixed region of smoke approximately 100 km downstream of the fires, visible optical depths as high as 2 were measured, at which time transmission to the surface was 8 percent, while 78 percent of the solar radiation was absorbed by the smoke. The calculated instantaneous heating rate inside the plume reached 24 K/d. While these effects are probably typical of those regions in the Persian Gulf area directly covered by the smoke, there is no evidence to suggest significant climatic effects in other regions.

Pilewskie, Peter↗

NASA NTRS1992

Cirrus microphysics and radiative transfer - Cloud field study on 28 October 1986

An analysis of remote-sensing measurements which had detected an inhomogeneous cloud structure, at 6-11 km altitude, in the data acquired during the FIRE 86 experiment in a 75 x 50 km cirrus cloud field, has derived fluxes whose comparison with modeled fluxes imply a modeling-based underestimation of both solar reflectivity/attenuation and downward IR fluxes. Reconciliation of model results with measurements can be achieved either by adding large concentrations of ice crystals or by altering the backscattering properties of ice crystals.

Kinne, Stefan↗

NASA NTRS1992

Latitudinal survey of spectral optical depths of the Pinatubo volcanic cloud - Derived particle sizes, columnar mass loadings, and effects on planetary albedo

Airborne measurements are examined of spectral optical depths, radiative fluxes, and scattered radiation fields during the NASA Caribbean mission (July 7-14, 1991) to characterize the Pinatubo volcanic cloud. The latitudinal and spectral dependence are reported of the volcanic cloud's optical depth. From these measurements moments of the particle-size distribution are determined. The change in planetary albedo induced by the volcanic cloud is calculated for the range of measured optical depths with the objective of assessing the impact on the solar radiation budget. Mid-visible optical depths higher than 0.4 were observed, placing the Pinatubo stratospheric cloud among the thickest ever measured. The latitudinal distribution of extinction shows that by July 7, 1991 the volcanic cloud had extended to 30 deg N. The effective particle radius was determined to be between 0.18 and 0.35 micron with a corresponding columnar mass loading between 35 and 80 mag/sq m.

Valero, Francisco P. J.↗

NASA NTRS1991

The 27-28 October 1986 FIRE Cirrus case study - Retrieval of cloud particle sizes and optical depths from comparative analyses of aircraft and satellite-based infrared measurements

Infrared radiance measurements were acquired from a narrow-field nadir-viewing radiometer based on the NASA ER-2 aircraft during a coincident Landsat 5 overpass on October 28, 1986 as part of the FIRE Cirrus IFO in the vicinity of Lake Michigan. The spectral bandpasses are 9.90-10.87 microns for the ER-2-based radiometer and 10.40-12.50 microns for the Landsat thematic mapper band. After adjusting for spatial and temporal differences, a comparative study using data from these two instruments is undertaken in order to retrieve cirrus cloud ice-crystal sizes and optical depths. Retrieval is achieved by analysis of measurement correlations between the two spectral bands and comparison to multistream radiative transfer model calculations. The results indicate that the equivalent sphere radii of the cirrus ice crystals were typically less than 30 microns. Such particles were too small to be measured by the available in situ instrumentation. Cloud optical depths at a reference wavelength of 11.4 microns ranged from 0.3 to 2.0 for this case study. Supplemental results in support of this study are described using radiation measurements from the King Air aircraft, which was also in near coincidence with the Landsat overpass.

Hammer, Philip D.↗