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Chris Hostetler

Publications and source records attributed to Chris Hostetler.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2024

Brillouin Asymmetric Spatial Heterodyne Oceanographic Lidar Receiver for Profiling Temperature, Salinity, and Sound Velocity

A lidar receiver employing a proposed Brillouin asymmetric spatial heterodyne (BASH) spectrometer to measure depth resolved profiles of near surface ocean temperature, salinity, and sound velocity from aircraft is conceptualized. A BASH spectrometer can have high throughput, can be designed for any wavelength and, importantly, can be field widened, allowing accurate, high spectral resolution of the Brillouin spectrum within diffuse scatter from depth. Temperature and salinity are measured independently with no assumptions about one or the other and the measurements are unbiased by the presence of particulate or elastic scatter. A sensitivity analysis and lidar simulations show the expected performance.

John A Smith↗
NASA NTRS2022

An Evaluation of Biomass Burning Aerosol Mass, Extinction, and Size Distribution in Geos Using Observations From Camp2EX

Biomass burning aerosol impacts aspects of the atmosphere and Earth system through radiative forcing, serving as cloud condensation nuclei, and air quality. Despite its importance, the representation of biomass burning aerosol is not always accurate in numerical weather prediction and climate models or reanalysis products. Using observations collected as part of the Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex) in August through October of 2019, aerosol concentration and optical properties are evaluated within the Goddard Earth Observing System (GEOS) and its underlying aerosol module, GOCART. In the operational configuration, GEOS assimilates aerosol optical depth observations at 550 nm to constrain aerosol fields. Particularly for biomass burning aerosol, without the assimilation of aerosol optical depth, aerosol extinction is underestimated compared to observations collected in the Philippines region during the CAMP2Ex campaign. The assimilation process adds excessive amounts of carbon to account for the underestimated extinction, resulting in positive biases in the mass of black and organic carbon, especially within the boundary layer, relative to in situ observations from the Langley Aerosol Research Group Experiment. Counteracting this, GEOS is deficient in sulphate and nitrate aerosol just above the boundary layer. Aside from aerosol mass, extinction within GEOS is a function of ambient relative humidity and an assumed particle size distribution. The relationship between dry and ambient extinction in GEOS reveals that hygroscopic growth is too aggressive within the model for biomass burning aerosol. An additional concern lies in the assumed particle size distribution for GEOS, which has a mode radius that is too small for organic carbon. Variability in the observed particle size distribution for biomass burning aerosol within a single flight also illuminates the fact that a single assumed particle size distribution is not sufficient and that for a proper representation, a more advanced aerosol module with GEOS may be necessary.

Aerosol Mass↗
NASA NTRS2022

Vertical structure of biomass burning aerosol transported over the southeast Atlantic Ocean

Biomass burning in southwestern Africa produces smoke plumes that are transported over the Atlantic Ocean and overlie vast regions of stratocumulus clouds. This aerosol layer contributes to direct and indirect radiative forcing of the atmosphere in this region particularly during the months of August, September, and October. There was a multi-year international campaign to study this aerosol and its interactions with clouds. Here, we report on the evolution of aerosol distributions and properties as measured by the airborne high spectral resolution lidar (HSRL-2) during the ORACLES (Observations of Aerosols above Clouds and their intEractionS) campaign in September 2016. The NASA Langley HSRL-2 instrument was flown on the NASA ER-2 aircraft for several days in September 2016. Data were aggregated at two pairs of 2° × 2° grid boxes to examine the evolution of the vertical profile of aerosol properties during transport over the ocean. Results showed that the structure of the profile of aerosol extinction and microphysical properties is maintained over a 1 to 2 d timescale. In the 3–5 km altitude range, 95 % of the aerosol extinction was contributed by particles in the 0.05–0.50 µm radius size range with the aerosol in this size range having an average effective radius of 0.16 µm. This indicates that there is essentially no scavenging or dry deposition at these altitudes. Moreover, there is very little day-to-day variation in these properties, such that time sampling as happens in such campaigns may be representative of longer periods such as monthly means. Below 3 km, there is considerable mixing with larger aerosol, most likely continental source near land. Furthermore, these measurements indicated that there was often a distinct gap between the bottom of the aerosol layer and cloud tops at the selected locations as evidenced by a layer of several hundred meters that contained relatively low aerosol extinction values above the clouds.

lidar↗
NASA NTRS2022

An Evaluation of the Liquid Cloud Droplet Effective Radius Derived from MODIS, Airborne Remote Sensing, and in Situ Measurements from CAMP2Ex

The cloud drop effective radius (Re) of the drop size distribution derived from passive satellite sensors is a key variable used in climate research. Validation of these satellite products has often taken place under stratiform cloud conditions that favor the assumption of cloud horizontal homogeneity used by the retrieval techniques. However, many studies have noted concerns with respect to significant biases in retrieved Re arising from cloud heterogeneity, for example, in cumulus cloud fields. Here, we examine data collected during the 2019 “Cloud, Aerosol and Monsoon Processes Philippines Experiment” (CAMP2Ex), which, in part, targeted the objective of providing the first detailed evaluation of Re retrieved across multiple platforms and techniques in a cumulus and congestus cloud region. Our evaluation consists of cross-comparisons of Re between the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra satellite, the Research Scanning Polarimeter (RSP) onboard the NASA P-3 aircraft, and in situ measurements from both the NASA P-3 and Learjet aircraft that are all taken in close spatiotemporal proximity to the same cloud fields. A particular advantage of our approach lies in the capability of the RSP to retrieve Re using a bi-spectral MODIS approach and a polarimetric approach, which allows for the evaluation of bi-spectral and polarimetric Re retrievals from an airborne perspective using the same samples. Averaged over all P-3 flight segments examined here for warm clouds, the RSP polarimetric method, the in situ method, and the bias-adjusted MODIS method of Fu et al. (2019) show a comparable median (mean ± standard deviation) for the Re samples of 9.6 (10.2 ± 4.0) µm, 11.0 (13.6 ± 11.3) µm, and 10.4 (10.8 ± 3.8) µm, respectively. These values are far lower than the values of 15.1 (16.2 ± 5.5) µm and 17.2 (17.7 ± 5.7) µm from the bi-spectral retrievals of RSP and MODIS, respectively. Similar results are observed when Re is segregated by cloud-top height and in detailed case studies. The clouds sampled during CAMP2Ex consist of mostly small (mean transect length ∼ 1.4 km) and low clouds (mean cloud-top height ∼ 1 km), which had more numerous small clouds than the trade wind cumuli sampled in past field campaigns such as Rain in Shallow Cumulus over the Ocean (RICO) and the Indian Ocean Experiment (INDOEX). The overestimates of Re from the RSP bi-spectral technique compared with the polarimetric technique increased as cloud size and cloud optical depth decreased. Drizzle, cloud-top bumpiness, and solar zenith angle, however, are not closely correlated with the overestimate of bi-spectral Re. For shallow clouds that dominated the liquid cloud cover for the CAMP2Ex region and period, we show that 3-D radiative transfer and cloud heterogeneity, particularly for the optically thin and small clouds, appear to be the leading cause of the large positive biases in bi-spectral retrievals. Because this bias varies with the underlying structure of the cloud field, caution continues to be warranted in studies that use bi-spectral Re retrievals in cumulus cloud fields.

Cloud microphysics↗
NASA NTRS2020

The Aerosol Characterization from Polarimeter and Lidar (ACEPOL) airborne field campaign

In the fall of 2017, an airborne field campaign was conducted from the NASA Armstrong Flight Research Center in Palmdale, California, to advance the remote sensing of aerosols and clouds with multi-angle polarimeters (MAP) and lidars. The Aerosol Characterization from Polarimeter and Lidar (ACEPOL) campaign was jointly sponsored by NASA and the Netherlands Institute for Space Research (SRON). Six instruments were deployed on the ER-2 high-altitude aircraft. Four were MAPs: the Airborne Hyper Angular Rainbow Polarimeter (AirHARP), the Airborne Multiangle SpectroPolarimetric Imager (AirMSPI), the Airborne Spectrometer for Planetary EXploration (SPEX airborne), and the Research Scanning Polarimeter (RSP). The remainder were lidars, including the Cloud Physics Lidar (CPL) and the High Spectral Resolution Lidar 2 (HSRL-2). The southern California base of ACEPOL enabled observation of a wide variety of scene types, including urban, desert, forest, coastal ocean, and agricultural areas, with clear, cloudy, polluted, and pristine atmospheric conditions. Flights were performed in coordination with satellite overpasses and ground-based observations, including the Ground-based Multiangle SpectroPolarimetric Imager (GroundMSPI), sun photometers, and a surface reflectance spectrometer.

SPECTRAL-RESOLUTION LIDAR↗
NASA NTRS2019

Above-Cloud Aerosol Radiative Effects based on ORACLES 2016 and ORACLES 2017 Aircraft Experiments

Determining the direct aerosol radiative effect (DARE) of absorbing aerosols above clouds from satellite observations alone is a challenging task, in part because the radiative signal of the aerosol layer is not easily untangled from that of the clouds below. In this study, we use aircraft measurements from the NASA ObseRvations of CLouds above Aerosols and their intEractionS (ORACLES) project in the southeastern Atlantic to derive it with as few assumptions as possible. This is accomplished by using spectral irradiance measurements (Solar Spectral Flux Radiometer, SSFR) and aerosol optical depth (AOD) retrievals (Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research, 4STAR) during vertical profiles (spirals) that minimize the albedo variability of the underlying cloud field – thus isolating aerosol radiative effects from those of the cloud field below. For two representative cases, we retrieve spectral aerosol single scattering albedo (SSA) and the asymmetry parameter (g) from these profile measurements and calculate DARE given the albedo range measured by SSFR on horizontal legs above clouds. For mid-visible wavelengths, we find SSA values from 0.80 to 0.85 and a significant spectral dependence of g. As the cloud albedo increases, the aerosol increasingly warms the column. The transition from a cooling to a warming top-of-aerosol radiative effect occurs at an albedo value (critical albedo) just above 0.2 in the mid-visible wavelength range. In a companion paper, we use the techniques introduced here to generalize our findings to all 2016 and 2017 measurements and parameterize aerosol radiative effects.

Cloud aerosol↗
NASA NTRS2017

TPSAS-NF1676L-26989-DND

The NASA Langley Research Center airborne High Spectral Resolution Lidar (HSRL-2) provided extensive measurements of smoke above shallow marine clouds while deployed from the NASAER-2 aircraft during the NASAEV-S Observations of Aerosols above Clouds and their Interactions (ORACLES) mission. During the first ORACLES field campaign in September 2016, the ER-2 was deployed from Walvis Bay, Namibia and conducted flights over the south eastern Atlantic Ocean. HSRL-2 measured profiles of aerosol backscattering, extinction and aerosol optical depth (AOD) at 355 and 532 nm and aerosol backscattering and depolarization at 1064 nm and so provided an excellent characterization of the wide-spread smoke layers above shallow marine clouds. We use the HSRL-2 measurements to examine retrievals of AOD above clouds retrieved from A Train active (CALIOP) and passive (OMI, MODIS) sensors. We also present profiles of aerosol microphysical properties such as concentration and effective radius that are derived from the HSRL-2 multi wavelength measurements of backscatter and extinction.

Richard Ferrare↗
NASA NTRS2011

TPSAS-NF1676L-13040-DND

We examine the feasibility of using airborne lidar data to: 1) infer CRC Convair-580 profiles of submicrometer fraction (SMF) over land (which is the fraction of aerosols with diameters less than 1 micrometer and is closely related to FMF) and 2) provide a proxy for CCN. If these initial Aerosol Extinction Aerosol Effective Radius feasibility studies prove successful, we will then apply these methodologies in subsequent studies to examine the feasibility of using CALIPSO data in a similar manner. We use data acquired by the NASA Langley Research Center airborne High Spectral Resolution Lidar (HSRL) during several recent field missions conducted by NASA, the Department of Energy, and NOAA. The airborne HSRL, which has acquired over 300 hours of data coincident with CALIPSO overpasses, measures aerosol extinction (532 nm), backscatter (532 and 1064 nm), and depolarization (532 and 1064 nm) profiles and thereby provides a dataset directly applicable to the CALIPSO measurements. During several of these field campaigns, airborne in situ measurements were acquired simultaneously within the HSRL “curtains” thereby facilitating direct correlations of the lidar observables to in situ measurements of particle size and composition, including SMF and CCN concentration. Previous studies have used simultaneous in situ measurements of SMF and Angström exponents derived from in situ scattering (Anderson et al., 2005) and remote sensing extinction (Redemann et al. 2009) measurements to build empirical relationships between these parameters. We adopt a similar approach and investigate relationships between the lidar observables, such as backscatter and extinction Angström exponents, with the coincident airborne in situ measurements of SMF and CCN concentration.

Richard Ferrare↗
NASA NTRSDate not supplied

TPSAS-NF1676L-34796-DND

The recently completed 2015-2017 EVS-2 mission NAAMES (The North Atlantic Aerosols and Marine Ecosystems Study) provides a unique set of airborne remote sensing and ship-based in situ measurements in a remote and under-sampled region of the Earth?s ocean. The NASA SABOR (Ship-Aircraft Bio-Optical Research) campaign was conducted during the summer of 2014, also in the Atlantic Ocean, out of the Chesapeake Bay and in the eastern coastal region of the United States. For both campaigns, the NASA GISS Research Scanning Polarimeter, a multi-angle, multi-spectral polarimeter measured the upwelling polarized radiances from aircraft. And for both campaigns, ship-based in situ measurements of the ocean were collected jointly with the aircraft measurements. We present results from the new RSP-MAPP (1) that is based on optimal estimation and that can retrieve simultaneous aerosol microphysical properties (including effective radius, single-scattering albedo, and real refractive index) and ocean color products using accurate radiative transfer, Mie calculations, and the DP (Detritus Plankton) series of accurate, numerically efficient ocean bio-optical models. The RSP-MAPP algorithm was applied to data collected during SABOR and NAAMES to retrieve aerosol microphysics and ocean products for all Aerosols-Above-Ocean (AAO) scenes. The RSP-MAPP products are compared against i) collocated aerosol extinction and backscatter profiles collected by the NASA LaRC airborne High Spectral Resolution Lidar (HSRL-1), including lidar depth profiles of the ocean diffuse attenuation coefficient and the hemispherical backscatter coefficient, and ii) collocated ship-based in situ measurements of the ocean.

Snorre Stamnes↗
NASA NTRSDate not supplied

TPSAS-NF1676L-21952-DND

DISCOVER-AQ was a 4-year NASA project aimed to improve the interpretation of total column satellite observations to help diagnose near-surface conditions relating to air quality. During DISCOVER-AQ HSRL-2 was flown onboard the NASA Langley B200 King Air. A suite of in-situ instruments was flown onboard NASA Wallops P-3B aircraft which spiraled up and down over a number of ground stations. The two aircraft flew coordinated flight tracks, both flying over several designated ground stations with close time coincidence, allowing for colocation of measurements from the in situ instruments suite and the HSRL-2. HSRL-2 is the first multiwavelength airborne lidar system that provides profiles of 3β (backscatter)+2α(extinction),allowing the retrieval of microphysical parameters like number, surface-area, and volume concentrations, and effective radius.

Patricia Sawamura↗
NASA NTRSDate not supplied

HSRL-2 Observations of Aerosol Variability and Mixing During Boundary Layer Evolution in Houston

The NASA Langley airborne multi-wavelength High Spectral Resolution Lidar (HSRL-2) provides vertical distribution of aerosol optical properties as ?curtains? of aerosol extinction, backscatter and depolarization along the flight track, plus intensive properties that are used to infer aerosol type and external mixing of types. Deployed aboard the NASA Langley King Air on the DISCOVER-AQ field mission in Houston in September 2013, HSRL-2 flew a pattern that included 18 ground sites, repeated four times a day, coordinated with a suite of airborne in situ measurements. The horizontally and vertically resolved curtains of HSRL-2 measurements give an unparalleled view of the spatial and temporal variability of aerosol, which provide broad context for interpreting other measurements and models. In Houston, HSRL-2 generally observed significant variability with distinct layering: boundary layer, residual layer, and frequent upper layers of smoke transported from the Mississippi Valley. The period from Sep. 11-14 is notable for a large aerosol build-up and persistent layers in the free troposphere. We investigate the aerosol properties and evolution using the vertically resolved HSRL-2 measurements, typing and mixture analysis techniques, and boundary layer detection. Between morning and afternoon overpasses, as the boundary layer grows, many distinctions between the layers are lost as the aerosols become mixed. As the boundary layer collapses overnight, the aerosols are cut off and are observed in a distinct residual layer the following day. HSRL-2 measurements of the upper smoke layers suggest slightly different properties each day as new smoke enters the region, while the morning boundary layer indicates more similarity in local emissions day-to-day. HSRL-2 intensive variables (indicators of aerosol type) reflect complex yet predictable mixing. We will present the analysis of aerosol mixtures, and explore the WRF-Chem chemical transport model along the HSRL-2 flight path.

Sharon P Burton↗
NASA NTRSDate not supplied

TPSAS-NF1676L-23266-DND

Currently, near-surface air quality information (e.g. PM_2.5) must be inferred from column-integrated quantities (i.e. Aerosol Optical Thickness – AOT) obtained by passive remote sensing from downward-looking satellite instruments. Such retrievals must address the following questions: What do we use for the height of the aerosols? Mixed Layer (ML) height? Can we assume that near-surface aerosol extinction is about the same as the mean aerosol extinction in the ML? How well is near-surface extinction related to surface PM_2.5? How well can column AOT be used to infer near-surface aerosol extinction and PM_2.5?

Richard Ferrare↗
NASA NTRSDate not supplied

TPSAS-NF1676L-27314-DND

The NASA Langley Research Center airborne High Spectral Resolution Lidar (HSRL-2) provided extensive measurements of smoke above shallow marine clouds while deployed from the NASA ER-2 aircraft during the NASA EV-S Observations of Aerosols above Clouds and their Interactions (ORACLES) mission. During the first ORACLES field campaign in September 2016, the ER-2 was deployed from Walvis Bay, Namibia and conducted flights over the southeastern Atlantic Ocean. HSRL-2 measured profiles of aerosol backscattering, depolarization, extinction and aerosol optical depth (AOD) at 355 and 532 nm and aerosol backscattering and depolarization at 1064 nm and so provided an excellent characterization of the wide-spread smoke layers above shallow marine clouds. We present profiles of aerosol microphysical properties such as concentration and effective radius that are derived from the HSRL-2 multiwavelength measurements of backscatter and extinction.

Detlef Müller↗