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At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS2022

Analysis and Impact of the Hunga Tonga-Hunga Ha’apai Stratospheric Water Vapor Plume

On Jan. 15, 2022, the Hunga Tonga-Hunga Ha’apai eruption injected SO2 and H2O into the 31 middle stratosphere. The eruption produced a persistent mid-stratospheric sulfate aerosol and H2O layer mostly confined to Southern Hemisphere (SH) tropics (Eq. to 30°S). These layers are still present in the tropics 5 ½ months after the eruption. The SH tropical confinement is simulated using a trajectory model. Measurements following the eruption show that the H2O layer is slowly rising while the aerosol layer is descending. The H2O layer’s upward movement is consistent with the residual vertical velocity. Gravitationally settling explains the descent of the aerosol layer. A -4K temperature anomaly coincident with the H2O enhancement is observed and is caused by thermal adjustment to the additional H2O IR cooling. A simple model of volcanic water injection at the time of the eruption simulates the observed vertical distribution H2O.

Atmospheric science↗
NASA NTRS2022

Tracking the 2022 Hunga Tonga-Hunga Ha'Apai Aerosol Cloud in the Upper and Middle Stratosphere Using Space-Based Observations

On 15 January 2022, the submarine Hunga Tonga volcanic eruption lofted materials high into the upper stratosphere, reaching a record-breaking altitude of ~58 km, unprecedented in the satellite observations era. Within two weeks, the bulk of the injected material circulated the globe between 20 – 30 km altitude, as observed by satellite instruments. We estimate that the stratospheric aerosol optical depth (sAOD) is the largest since the Pinatubo eruption and is at least twice as great as the sAOD after the 2015 Calbubo eruption despite the similar SO 2 injection from that eruption. We use space-based observations to monitor the Hunga-Tonga volcanic plume evolution and transport at different altitudes as it circulates the globe. While the main aerosol layer remains trapped in the tropical pipe, small parts have already made it to both the northern and southern hemisphere poles by April, which is almost certain to influence this year's ozone hole.

Atmospheric science↗
NASA NTRSDate not supplied

Monitoring the 2022 Hunga Tonga-Hunga Ha'apai Aerosol Cloud Using Space-Based Observations

- We will analyze the volcanic plume progression, spread and properties using space-based observations - OMPS LP, SAGE III/ISS, CALIPSO, TROPOMI - OMPS LP and SAGE III/ISS are limb instruments that measure the aerosol vertical profiles globally, while CALIPSO is a LIDAR that measures the backscatter and depolarization ratio of the aerosol profiles. -TROPOMI is a UV instrument that measures SO2 and absorbing aerosol total column - Volcanic plume in the upper stratosphere - The main plume in middle stratosphere - Volcanic aerosol transport to SH/NH - Volcanic aerosol optical properties

Atmospheric Science↗
NASA NTRS2022

Near Space Demonstration of A Compact LWIR Spectro-Polarimeter for Ice Cloud Measurements

In the summer of 2021, an InfraRed Channeled Spectro-Polarimeter (IRCSP) was demonstrated in the near space environment aboard a NASA Columbia Scientific Ballooning Facility high-altitude balloon out of Fort Sumner, NM. The compact IRCSP is sensitive to linearly polarized long-wave infrared (LWIR) light between 7-12 micron and targets cloud micro-physical properties. Post landing the instrument was retrieved with no damage to the optical payload and collected over 150 minutes of flight data at altitudes above 30 km. The results collected both demonstrate the application of uncooled microbolometers in the low pressure environment and represent the first know field evidence of a polarized signal from clouds in the LWIR. During deployment, the IRCSP reported brightness temperatures between 250-285K with uncertainty of < 1.5K. In addition, multiple intervals of statistically significant polarization with degrees of linear polarization (DoLP) between 1−20% were detected. These results support the hypothesis that the LWIR polarimetry has the potential to add new sensitivity to existing remote sensing platforms.

remote sensing↗
NASA NTRS2023

The Cross Equatorial Transport of the Hunga Tonga-Hunga Ha’apai Eruption Plume

On 15 January 2022, the Hunga Tonga-Hunga Ha'apai (HT) eruption injected SO 2 and water into the middle stratosphere. Shortly after the eruption, the water vapor anomaly moved northward toward and across the equator. This northward movement appears to be due to equatorial Rossby waves forced by the excessive infrared water vapor cooling. Following the early eruption stage, persistent mid-stratospheric water vapor and aerosol layers were mostly confined to Southern Hemisphere tropics (Eq. to 30°S). However, during the spring of 2022, the westerly phase of the tropical quasi-biennial oscillation (QBO) descended through the tropics. The HT water vapor and aerosol anomalies were observed to again move across the equator coincident with the shift in the Brewer-Dobson circulation and the descent of the QBO shear zone.

Atmospheric Science↗
NASA NTRS2023

Virus Infection of Phytoplankton Increases Average Molar Mass and Reduces Hygroscopicity of Aerosolized Organic Matter

Viral infection of phytoplankton is a pervasive mechanism of cell death and bloom termination, which leads to the production of dissolved and colloidal organic matter that can be aerosolized into the atmosphere. Earth-observing satellites can track the growth and death of phytoplankton blooms on weekly time scales but the impact of viral infection on the cloud forming potential of associated aerosols is largely unknown. Here, we determine the influence of viral-derived organic matter, purified viruses, and marine hydrogels on the cloud condensation nuclei activity of their aerosolized solutions, compared to organic exudates from healthy phytoplankton. Dissolved organic material derived from exponentially growing and infected cells of well-characterized eukaryotic phytoplankton host-virus systems, including viruses from diatoms, coccolithophores and chlorophytes, was concentrated, desalted, and nebulized to form aerosol particles composed of primarily of organic matter. Aerosols from infected phytoplankton cultures resulted in an increase in critical activation diameter and average molar mass in three out of five combinations evaluated, along with a decrease in organic kappa (hygroscopicity) compared to healthy cultures and seawater controls. The infected samples also displayed evidence of increased surface tension depression at realistic cloud water vapor supersaturations. Amending the samples with xanthan gum to simulate marine hydrogels increased variability in organic kappa and surface tension in aerosols with high organic to salt ratios. Our findings suggest that the pulses of increased dissolved organic matter associated with viral infection in surface waters may increase the molar mass of dissolved organic compounds relative to surface waters occupied by healthy phytoplankton or low phytoplankton biomass.

Atmospheric science↗
NASA NTRS2023

Observations Suggest That North African Dust Absorbs Less Solar Radiation Than Models Estimate

Desert dust accounts for a large fraction of shortwave radiation absorbed by aerosols, which adds to the climate warming produced by greenhouse gases. However, it remains uncertain exactly how much shortwave radiation dust absorbs. Here, we leverage in-situ measurements of dust single-scattering albedo to constrain absorption at mid-visible wavelength by North African dust, which accounts for approximately half of the global dust. We find that climate and chemical transport models overestimate North African dust absorption aerosol optical depth (AAOD) by up to a factor of two. This occurs primarily because models overestimate the dust imaginary refractive index, the effect of which is partially masked by an underestimation of large dust particles. Similar factors might contribute to an overestimation of AAOD retrieved by the Aerosol Robotic Network, which is commonly used to evaluate climate and chemical transport models. The overestimation of dust absorption by models could lead to substantial biases in simulated dust impacts on the Earth system, including warm biases in dust radiative effects.

Atmospheric science↗
NASA NTRSDate not supplied

Validation of OMPS LP Ozone Profile Retrievals Using Solar Occultation Satellite Measurements

The OMPS Limb Profiler (OMPS LP) satellite instrument, launched in October 2011, performs limb measurements of scattered solar radiation in the ultraviolet and visible wavelengths, which allow for the retrieval of ozone profiles from the top of clouds up to 55km. In this study we utilize ozone retrievals from two solar occultation satellite instruments, SAGE III/ISS and ACE-FTS, to validate OMPS LP profile measurements processed with the new NASA GSFC version 2.6 retrieval algorithm. OMPS LP started operational observations in April 2012, whereas ACE-FTS observations started in February 2004, therefore, there are currently 12 years of data overlap to exploit for validation. SAGE III/ISS observations started in June 2017, which provides 7 years of data overlap with OMPS LP. The OMPS LP is a solar scattering instrument that makes observations in the sunlit portion of the Earth, whilst ACE-FTS and SAGE III/ISS are solar occultation instruments that measure ozone only at sunrise and sunset. To account for these differences in measurement times we use the Goddard Diurnal Ozone Climatology (GDOC). Diurnal adjustments using this climatology have been shown to help reduce biases above 30 km. Our analysis shows that biases between OMPS LP v2.6, ACE-FTS, and SAGE III/ISS are <10% between 18 and 45 km, and increase above and below these altitudes, which are comparable to the previous version of OMPS LP ozone retrievals (v2.5). The vertical patterns of the differences are similar across different latitudes and seasons, with larger seasonal variations observed in the Northern Hemisphere.

Atmospheric Science↗
NASA NTRSDate not supplied

Comparisons of ozone profile retrievals from the OMPS Limb Profiler and ACE-FTS

The OMPS Limb Profiler (OMPS LP) was launched in October 2011, and has more than 10 years of overlap with ACE-FTS. Therefore, ACE-FTS offers an excellent opportunity to obtain independent ozone profile data with which to validate OMPS LP ozone retrievals. In this study we utilize ACE-FTS ozone retrievals to evaluate 10 years of OMPS LP profile measurements processed with the new NASA GSFC version 2.6 retrieval algorithm. The OMPS LP is a solar scattering instrument that makes observations in the sunlit portion of the Earth, whilst ACE-FTS is a solar occultation instrument that measures ozone only at sunrise and sunset. To account for these differences in measurement times we use the Goddard Diurnal Ozone Climatology (GDOC). Diurnal adjustments using this climatology have been shown to help reduce biases above 30 km. Our analysis shows that biases between OMPS LP v2.6 and ACE-FTS v5.2 are <10% between 18 and 45 km, and increase above and below these altitudes. The vertical patterns of the differences are similar across different latitudes and seasons, with larger seasonal variations observed in the Northern Hemisphere. We also analyze ozone time series from the two instruments.

Atmospheric Science, Stratospheric Ozone↗
NASA NTRS2024

Substantial Cooling Effect From Aerosol-Induced Increase in Tropical Marine Cloud Cover

With global warming currently standing at approximately +1.2 °C since preindustrial times, climate change is a pressing global issue. Marine cloud brightening is one proposed method to tackle warming through injecting aerosols into marine clouds to enhance their reflectivity and thereby planetary albedo. However, because it is unclear how aerosols influence clouds, especially cloud cover, both climate projections and the effectiveness of marine cloud brightening remain uncertain. Here, we use satellite observations of volcanic eruptions in Hawaii to quantify the aerosol fingerprint on tropical marine clouds. We observe a large enhancement in reflected sunlight, mainly due to an aerosol-induced increase in cloud cover. This observed strong negative aerosol forcing suggests that the current level of global warming is driven by a weaker net radiative forcing than previously thought, arising from the competing effects of greenhouse gases and aerosols. This implies a greater sensitivity of Earth’s climate to radiative forcing and therefore a larger warming response to both rising greenhouse gas concentrations and reductions in atmospheric aerosols due to air quality measures. However, our findings also indicate that mitigation of global warming via marine cloud brightening is plausible and is most effective in humid and stable conditions in the tropics where solar radiation is strong.

Atmospheric science↗
NASA NTRS2024

Observational Constraint on A Feedback From Supercooled Clouds Reduces Projected Warming Uncertainty

The increase of carbon-dioxide-doubling-induced warming (climate sensitivity) in the latest climate models is primarily attributed to a larger extratropical cloud feedback. This is thought to be partly driven by a greater ratio of supercooled liquid-phase clouds to all clouds, termed liquid phase ratio. We use an instrument simulator approach to show that this ratio has increased in the latest climate models and is overestimated rather than underestimated as previously thought. In our analysis of multiple models, a greater ratio corresponds to stronger negative cloud feedback, in contradiction with single-model-based studies. We trace this unexpected result to a cloud feedback involving a shift from supercooled to warm clouds as climate warms, which corresponds to greater cloud amount and optical depth and weakens the extratropical cloud feedback. Better constraining this ratio in climate models – and thus this supercooled cloud feedback – impacts their climate sensitivities by up to 1 ˚C and reduces inter-model spread.

Climate and Earth system modelling↗
NASA NTRS1994

Solar fine scale structures in the corona, transition region, and lower atmosphere

The American Science and Engineering Soft X-ray Imaging Payload and the Naval Research Laboratory High Resolution Telescope and Spectrograph (HRTS) were launched from White Sands on 1987 December 11 in coordinated sounding rocket flights. The goal was to investigate the correspondence of fine-scale structures from different temperature regimes in the solar atmosphere, and particularly the relationship between X-ray bright points (XBPs) and transition region explosive events. We present results of the analysis of co-aligned X-ray images, maps of sites of transition region explosive events observed in C IV 10(exp 5), HRTS 1600 A spectroheliograms of the T(sub min) region, and ground-based magnetogram and He I 10830 A images. We examined the relationship of He I 10830 A dark features and evolving magnetic features which correspond to XBPs. We note a frequent double ribbon pattern of the He I dark feature counterparts to XBPs. We discuss an analysis of the relationship of XBPs to evolving magnetic features by Webb et al., which shows that converging magnetic features of opposite polarity are the most significant magnetic field counterparts to XBPs. The magnetic bipolar features associated with XBPs appear as prominent network elements in chromospheric and transition region images. The features in C IV observations corresponding to XBP sites are in general bright, larger scale (approximately 10 arcsec) regions of complex velocity fields of order 40 km/s, which is typical of brighter C IV network elements. These C IV features do not reach the approximately 100 km/s velocities seen in the C IV explosive events. Also, there are many similar C IV bright network features without a corresponding XBP in the X-ray image. The transition region explosive events do not correspond directly to XBPs. The explosive events appear to be concentrated in the quiet Sun at the edges of strong network, or within weaker field strength network regions. We find a greater number of C IV events than expected from the results of a previous Spacelab 2 HRTS disk survey. We attribute this at least partly to better spatial resolution with the newer HRTS data. The full-disk X-ray image shows a pattern of dark lanes in quiet Sun areas. The number density of C IV events is twice as large inside as outside a dark lane (4.6 x 10(exp -3) vs. 2.3 x 10(exp -3) explosive events per arcsec (exp 2)). The dark lane corresponds to an old decaying magnetic neutral line. We suggest that this provides an increased opportunity for small-scale convergence and reconnection of opposite polarity magnetic field features, in analogy with the results of Webb et al. for XBPs but at a reduced scale of reconnection.

Moses, Dan↗
NASA NTRS2024

Enhancing Global Food Security: Opportunities for the American Meteorological Society

Food security is a key pillar of environmental security yet remains one of the world’s greatest challenges. Its obverse, food insecurity, negatively impacts health and well-being, drives mass migration, and undermines national security and global sustainable development. Ensuring food security is a delicate balance of myriad concerns within the atmospheric and Earth sciences, agronomy and agriculture engineering, social sciences, economics, monitoring, and policymaking. A Food Security Presidential Session at the American Meteorological Society’s (AMS) 2022 Annual Meeting brought together experts across disciplines to tackle issues at the nexus of weather, climate, and food security. The starkest takeaway was the realization that, despite its importance and clear roles for the atmospheric and climate sciences, food security has not been a focus for the AMS community. The aim of this paper is to build on the perspectives shared by this expert panel and to identify overlapping issues and key points of intersection between the food-security community and AMS. We examine 1) the interactions between weather, climate, and the food system and how they influence food security; 2) the time and spatial scales of food security decision support that match weather and climate phenomena; 3) the role of both providers and users of information as well as decision-makers in improving research to operations for food security; and 4) the opportunities for the AMS community to address food security. We conclude that, moving forward, the AMS community is well-positioned to scale up its engagement across the global food system to address existing scientific needs and technology gaps to improve global food security.

Food security↗
NASA NTRS2012

Navigation Challenges in the MAVEN Science Phase

The MAVEN spacecraft will explore Mars' upper atmosphere. The primary science phase will last one (Earth) year, during which the spacecraft will be in an elliptical 4.5 hour orbit at an inclination of 75 degrees. The 75 degree inclination results in the orbit periapsis oscillating between +/-75 degrees latitude, thus naturally covering most Mars latitudes during the primary mission. The orbit will be controlled via maneuvers so that the maximum orbit density remains in a density corridor. This results in the MAVEN science phase being in a light aerobraking type orbit of around 160 km for an extended period. In addition, the mission has significantly less tracking data than aerobraking phases of other missions, and even less than other NASA Mars orbiter primary phases. This results in significant challenges for the Navigation Team. They can be summarized as a difficulty in determining the current density profile, which maps into degraded trajectory predictions and less accurate control over the spacecraft location in the targeted density corridor via maneuvers. This paper describes these challenges and the Navigation Team's plans to meet them.

MAVEN↗