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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Rethinking the Susceptibility-Based Strategy for Marine Cloud Brightening Climate Intervention: Experiment With CESM2 and Its Implications

Previous modeling studies indicate that even though marine cloud brightening under a susceptibility-based strategy is effective in reducing the global average surface temperature, it triggers a La Niña-like sea-surface temperature response with cooling mostly confined within lower latitudes. Here we explore a different cloud seeding strategy involving seeding of regions with low susceptibility, primarily over the ocean in midlatitudes during the winter. Simulations with the Community Earth System Model, version 2 reveal that because the regional forcing is weaker and more widespread, cooling is more evenly distributed over the globe. This new strategy also does not result in the La Niña-like state seen in the other strategies.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1972

The Nimbus 4 infrared spectroscopy experiment. I - Calibrated thermal emission spectra.

Measurement of the infrared spectrum of the earth and atmosphere between 400 and 1600/cm. In an effort to obtain spectra with high absolute accuracy, it was necessary to incorporate many factors into the calibration, including small departures from unity in the emissivity of the on-board calibration source, imbalance between cold and warm calibration ports, and effects due to orbital variations in instrument temperature. The inclusion of such higher order corrections, along with careful data screening processes, has ensured a high quality data set that can be used in a variety of geophysical and meteorological investigations. Representative samples of data are presented that illustrate the behavior of the thermal emission spectra under a variety of conditions encountered in a typical orbit, including extremes in temperature, surface reststrahlung (or residual ray) effects, and various types of cloud conditions.

Hanel, R. A.↗
NASA NTRS1989

The geological record of life 3500 Ma ago: Coping with the rigors of a young earth during late accretion

Thin cherty sedimentary layers within the volcanic portions of the 3,500 to 3,300 Ma-old Onverwacht and Fig Tree Groups, Barberton Greenstone belt, South Africa, and Warrawoona Group, eastern Pilbara Block, Western Australia, contain an abundant record of early Archean life. Five principal types of organic and probably biogenic remains and or structures can be identifed: stromatolites, stromatolite detritus, carbonaceous laminite or flat stromalite, carbonaceous detrital particles, and microfossils. Early Archean stromatolites were reported from both the Barberton and eastern Pilbara greenstone belts. Systematic studies are lacking, but two main morphological types of stromatolites appear to be represented by these occurrences. Morphology of the stromalites is described. Preserved early Archean stromatolites and carbonaceous matter appear to reflect communities of photosynthetic cyanobacteria inhabiting shallow, probably marine environments developed over the surfaces of low-relief, rapidly subsiding, simatic volcanic platforms. The overall environmental and tectonic conditions were those that probably prevailed at Earth's surface since the simatic crust and oceans formed sometime before 3,800 Ma. Recent studies also suggest that these early Archean sequences contain layers of debris formed by large-body impacts on early Earth. If so, then these early bacterial communities had developed strategies for coping with the disruptive effects of possibly globe-encircling high-temperature impact vapor clouds, dust blankets, and impact-generated tsunamis. It is probable that these early Archean biogenic materials represent organic communities that evolved long before the beginning of the preserved geological record and were well adapted to the rigors of life on a young, volcanically active Earth during late bombardment. These conditions may have had parallels on Mars during its early evolution.

Lowe, Donald R.↗
NASA NTRS2010

Cryogenic Storage Tank Non-Destructive Evaluation

This slide presentation reviews the work in non-destructive evaluation (NDE) of cryogenic storage tanks. Four large cryogenic tanks, constructed in 1965 with perlite insulation in the annular regions, are of concern. The construction of the tanks, two Liquid Oxygen (LOX) and two Liquid Hydrogen (LH2), are described. The loss rate for the LOX tank at Pad A is slightly higher than that for the one at Pad B. The concerns for the LH2 tank at Pad B are that there is a significantly higher boil-off rate than that at Pad A, that there is mold growth, indicative of increased heat flow, that there is a long down-time needed for repairs, and that 3 of 5 full thermal cycles have been used on the Pad B LH2 tank. The advantages and disadvantages of thermal imaging are given. A detailed description of what is visible of the structures in the infra-red is given and views of the thermal images are included. Missing Perlite is given as the probable cause of the cold spot on the Pad B LH2 tank. There is no indications of problematic cold regions on the Pad A LH2 tank, as shown by the thermal images given in the presentation. There is definite indication of a cold region on the Pad A LOX tank. There is however concerns with thermal imaging, as thermal images can be significantly effected by environmental conditions, image differences on similar days but with different wind speeds. Other effects that must be considered include ambient temperature, humidity levels/dew, and cloud reflections

Arens, Ellen↗
NASA NTRS2013

Vertical Structure of Ice Cloud Layers From CloudSat and CALIPSO Measurements and Comparison to NICAM Simulations

The shape of the vertical profile of ice cloud layers is examined using 4 months of CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) global measurements taken on January, April, July, and October 2007. Ice clouds are selected using temperature profiles when the cloud base is located above the 253K temperature level. The obtained ice water content (IWC), effective radius, or extinction coefficient profiles are normalized by their layer mean values and are expressed in the normalized vertical coordinate, which is defined as 0 and 1 at the cloud base and top heights, respectively. Both CloudSat and CALIPSO observations show that the maximum in the IWC and extinction profiles shifts toward the cloud bottom, as the cloud depth increases. In addition, clouds with a base reaching the surface in a high-latitude region show that the maximum peak of the IWC and extinction profiles occurs near the surface, which is presumably due to snow precipitation. CloudSat measurements show that the seasonal difference in normalized cloud vertical profiles is not significant, whereas the normalized cloud vertical profile significantly varies depending on the cloud type and the presence of precipitation. It is further examined if the 7 day Nonhydrostatic Icosahedral Atmospheric Model (NICAM) simulation results from 25 December 2006 to 1 January 2007 generate similar cloud profile shapes. NICAM IWC profiles also show maximum peaks near the cloud bottom for thick cloud layers and maximum peaks at the cloud bottom for low-level clouds near the surface. It is inferred that oversized snow particles in the NICAM cloud scheme produce a more vertically inhomogeneous IWC profile than observations due to quick sedimentation.

Ham, Seung-Hee↗
NASA NTRS1992

Atmospheric effects on SMMR and SSM/I 37 GHz polarization difference over the Sahel

The atmospheric effects on the difference of vertically and horizontally polarized brightness temperatures, Delta(T) observed at 37 GHz frequency of the SMMR on board the Nimbus-7 satellite and SSM/I on board the DMSP-F8 satellite are studied over two 2.5 by 2.5 deg regions within the Sahel and Sudan zones of Africa from January 1985 to December 1986 through radiative transfer analysis using surface temperature, atmospheric water vapor, and cloud optical thickness. It is found that atmospheric effects alone cannot explain the observed temporal variation of Delta(T), although the atmosphere introduces important modulations on the observed seasonal variations of Delta(T) due to rather significant seasonal variation of precipitable water vapor. These Delta(T) data should be corrected for atmospheric effects before any quantitative analysis of land surface change over the Sahel and Sudan zones.

Choudhury, B. J.↗
NASA NTRS2014

Modeling the Influences of Aerosols on Pre-Monsoon Circulation and Rainfall over Southeast Asia

We conduct several sets of simulations with a version of NASA's Goddard Earth Observing System, version 5, (GEOS-5) Atmospheric Global Climate Model (AGCM) equipped with a two-moment cloud microphysical scheme to understand the role of biomass burning aerosol (BBA) emissions in Southeast Asia (SEA) in the pre-monsoon period of February-May. Our experiments are designed so that both direct and indirect aerosol effects can be evaluated. For climatologically prescribed monthly sea surface temperatures, we conduct sets of model integrations with and without biomass burning emissions in the area of peak burning activity, and with direct aerosol radiative effects either active or inactive. Taking appropriate differences between AGCM experiment sets, we find that BBA affects liquid clouds in statistically significantly ways, increasing cloud droplet number concentrations, decreasing droplet effective radii (i.e., a classic aerosol indirect effect), and locally suppressing precipitation due to a deceleration of the autoconversion process, with the latter effect apparently also leading to cloud condensate increases. Geographical re-arrangements of precipitation patterns, with precipitation increases downwind of aerosol sources are also seen, most likely because of advection of weakly precipitating cloud fields. Somewhat unexpectedly, the change in cloud radiative effect (cloud forcing) at surface is in the direction of lesser cooling because of decreases in cloud fraction. Overall, however, because of direct radiative effect contributions, aerosols exert a net negative forcing at both the top of the atmosphere and, perhaps most importantly, the surface, where decreased evaporation triggers feedbacks that further reduce precipitation. Invoking the approximation that direct and indirect aerosol effects are additive, we estimate that the overall precipitation reduction is about 40% due to the direct effects of absorbing aerosols, which stabilize the atmosphere and reduce surface latent heat fluxes via cooler land surface temperatures. Further refinements of our two-moment cloud microphysics scheme are needed for a more complete examination of the role of aerosol-convection interactions in the seasonal development of the SEA monsoon.

SE Asia Monsoon↗
NASA NTRS2010

Atmospheric CO2: Principal Control Knob Governing Earth's Temperature

Ample physical evidence shows that carbon dioxide (CO2) is the single most important climate-relevant greenhouse gas in Earth s atmosphere. This is because CO2, like ozone, N2O, CH4, and chlorofluorocarbons, does not condense and precipitate from the atmosphere at current climate temperatures, whereas water vapor can and does. Noncondensing greenhouse gases, which account for 25% of the total terrestrial greenhouse effect, thus serve to provide the stable temperature structure that sustains the current levels of atmospheric water vapor and clouds via feedback processes that account for the remaining 75% of the greenhouse effect. Without the radiative forcing supplied by CO2 and the other noncondensing greenhouse gases, the terrestrial greenhouse would collapse, plunging the global climate into an icebound Earth state.

Lacis, Andrew A.↗
NASA NTRS2006

The Sensitivity of Arctic Ozone Loss to Polar Stratospheric Cloud Volume and Chlorine and Bromine Loading in a Chemistry and Transport Model

The sensitivity of Arctic ozone loss to polar stratospheric cloud volume (V(sub PSC)) and chlorine and bromine loading is explored using chemistry and transport models (CTMs). A simulation using multi-decadal output from a general circulation model (GCM) in the Goddard Space Flight Center (GSFC) CTM complements one recycling a single year s GCM output in the Global Modeling Initiative (GMI) CTM. Winter polar ozone loss in the GSFC CTM depends on equivalent effective stratospheric chlorine (EESC) and polar vortex characteristics (temperatures, descent, isolation, polar stratospheric cloud amount). Polar ozone loss in the GMI CTM depends only on changes in EESC as the dynamics repeat annually. The GSFC CTM simulation reproduces a linear relationship between ozone loss and Vpsc derived from observations for 1992 - 2003 which holds for EESC within approx.85% of its maximum (approx.1990 - 2020). The GMI simulation shows that ozone loss varies linearly with EESC for constant, high V(sub PSC).

Douglass, A. R.↗
NASA NTRS1982

Determination of semi-transparent cirrus cloud temperature from infrared radiances - Application to Meteosat

A bispectral technique was employed to determine the cirrus cloud-top temperature. Data were gathered from aircraft equipped with the ARIES radiometer, which on sixteen flights provided IR readings at 6.5 and 11.5 microns of cirrus tops. The flights were made on a NASA Convair to a maximum ceiling of 12,500 m. The brightness temperatures above the cirrus were found to be consistently colder, by up to 40 K, than the 11.5 microns window channel, and good spatial correlations were displayed over whole clouds. Effective emissivities are calculated for both channels and applied to Meteosat digital imagery. The subsequent derived temperatures were significantly colder than black-body temperatures, which is explained by taking into account the absorption of emitted radiation by water vapor.

Szejwach, G.↗
NASA NTRS2012

SRT Evaluation of AIRS Version-6.02 and Version-6.02 AIRS Only (6.02 AO) Products

Version-6 contains a number of significant improvements over Version-5. This report compares Version-6 products resulting from the advances listed below to those from Version-5. 1. Improved methodology to determine skin temperature (T(sub s)) and spectral emissivity (Epsilon(sub v)). 2. Use of Neural-net start-up state. 3. Improvements which decrease the spurious negative Version-5 trend in tropospheric temperatures. 4. Improved QC methodology. Version-6 uses separate QC thresholds optimized for Data Assimilation (QC=0) and Climate applications (QC=0,1) respectively. 5. Channel-by-channel clear-column radiances R-hat(sub tau) QC flags. 6. Improved cloud parameter retrieval algorithm. 7. Improved OLR RTA. Our evaluation compared V6.02 and V6.02 AIRS Only (V6.02 AO) Quality Controlled products with those of Version-5.0. In particular we evaluated surface skin temperature T(sub s), surface spectral emissivity Epsilon(sub v), temperature profile T(p), water vapor profile q(p), OLR, OLR(sub CLR), effective cloud fraction alpha-Epsilon, and cloud cleared radiances R-hat(sub tau) . We conducted two types of evaluations. The first compared results on 7 focus days to collocated ECMWF truth. The seven focus days are: September 6, 2002; January 25, 2003; September 29, 2004; August 5, 2005; February 24, 2007; August 10, 2007; and May 30, 2010. In these evaluations, we show results for T(sub s), Epsilon(sub v), T(p), and q(p) in terms of yields, and RMS differences and biases with regard to ECMWF. We also show yield trends as well as bias trends of these quantities relative to ECMWF truth. We also show yields and accuracy of channel by channel QC d values of R-hat(sub tau) for V6.02 and V6.02 AO. Version-5 did not contain channel by channel QC d values of R-hat(sub tau). In the second type of evaluation, we compared V6.03 monthly mean Level-3 products to those of Version-5.0, for four different months: January, April, July, and October; in 3 different years 2003, 2007, and 2011. In particular, we compared V6.03 and V5.0 trends of T(p), q(p), alpha-Epsilon, OLR, and OLR(sub CLR) computed based on results for these 12 time periods

Susskind, Joel↗
NASA NTRS1995

The 5-6 December 1991 FIRE IFO II jet stream cirrus case study: Possible influences of Volcanic Aerosols

In presenting an overview of the cirus clouds comprehensively studied by ground-based and airborne sensors from Coffeyville, Kansas, during the 5-6 December 1992 Project First ISCCP Region Experiment (FIRE) Intensive Fields Observation (IFO) II case study period, evidence is provided that volcanic aerosols friom the June 1991 Pinatubo eruptions may have significantly influenced the formation and maintenance of the cirrus. Following the local appearance of a spur of stratospheric volcanic debris from the subtropics, a series of jet streaks subsequently conditioned the troposphere through tropopause foldings with sulfur-based particles that became effective cloud-forming nuclei in cirrus clouds. Aerosol and ozone measurements suggest a complicated history of stratospheric-tropospheric exchanges embedded within the upper-level flow, and cirrus cloud formation was noted to occur locally at the boundaries of stratospheric aerosol-enriched layers that became humidified through diffusion, precipitation, or advective processes. Apparent cirrus cloud alterations include abnormally high ice crystal concentrations (up to approximately 600/L), complex radial ice crystal types, and relatively large haze particles in cirrus uncinus cell heads at temperatures between -40 and -50 C. Implications for volcanic-cirrus cloud climate effects and usual (nonvolcanic aerosol) jet stream cirrus cloud formation are discussed.

Sassen, Kenneth↗
NASA NTRS1982

The global distribution of water vapor in the middle atmosphere of Venus

Near-IR measurements are presented of the mean vertical and horizontal distribution of water vapor in the Venus clouds as measured by the Pioneer Venus Orbiter IR radiometer, and comparisons are made with previous data. Six thermal channels were used to generate several hundred thousand readings for determination of the mean mixing ratio. Averaging was performed as a function of the solar zenith angle, with profiles retrieved with a relaxation method applied to radiance data at 45 microns. Consideration was given to mean cloud models and temperature profiles obtained from the five temperature sounding channels scanning from 11.5-15 microns. Laboratory tests were effected to validate the transmission functions. The results included a maximum column abundances above the cloud optical depth in the early afternoon in the equatorial regions. Mixing ratio enhancement was highest on the dayside and at high altitudes, with a mean ratio of 0.0001 at a 40% uncertainty level. Day-to-day fluctuations in the pressure level at 11.5 microns was larger than 10%, far below the factors of 2-3 determined by other investigators.

Schofield, J. T.↗
NASA NTRS1993

The 5-6 December 1991 FIRE IFO 2 jet stream cirrus case study: The influence of volcanic aerosols

In presenting an overview of the cirrus clouds comprehensively studied by ground-based and airborne sensors from Coffeyville, KS, during the 5-6 Dec. 1992 Project FIRE (First International Satellite Cloud Climatology Project Regional Experiment) IFO II case study period, evidence is provided that volcanic aerosols from the June 1991 Pinatubo eruptions significantly influenced the formation and maintenance of the cirrus. Following the local appearance of a spur of stratospheric volcanic debris from the subtropics, a series of jet streaks subsequently conditioned the troposphere through tropopause foldings with sulfur-based particles that became effective cirrus cloud-forming nuclei. Aerosol and ozone measurements suggest a complicated history of stratospheric-tropospheric exchanges embedded within the upper level flow, and cirrus cloud formation was noted to occur locally at the boundaries of stratospheric aerosol-enriched layers that became humidified through diffusion, precipitation, or advective processes. Apparent cirrus cloud alterations include abnormally high ice crystal concentrations (up to approximately 600 l(sup -1), small but complex radial ice crystal types, and relatively large haze particles in cirrus uncinus cell heads at temperatures between -40 to -50 C. Implications for volcanic-cirrus cloud climate effects, and usual (non-volcanic aerosol) jet stream cirrus cloud formation are discussed.

Sassen, Kenneth↗
DOE OSTI2021

Arctic Ice Nucleation Sampling during MOSAiC (INPMOSAIC2) Field Campaign Report

The accelerated rate of warming in the Arctic is of great concern due to potential impacts that include release of greenhouse gases from permafrost, melting glacial ice contributing to sea level rise, and declining sea ice cover exposing the darker ocean surface. These processes induce positive feedbacks and contribute to further warming that affects climate globally. Clouds play a crucial role in regulating the energy reaching the sea ice and snow surfaces, but the magnitude of their effects on surface temperature is not well constrained in the Arctic. Aerosols are an important contributor by serving as seeds for cloud particle formation, but even less is known about their overall impact and origin. In particular, aerosols that serve as ice nucleating particles (INPs) are vastly understudied, especially above the central Arctic Ocean. However, INPs likely play a significant role in arctic mixed-phase cloud (AMPC) microphysics and the resulting impacts of such clouds on the surface energy budget over the sea ice.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1990

Global, seasonal cloud variations from satellite radiance measurements. II - Cloud properties and radiative effects

Cloud and surface radiative properties and their effects on the earth and surface radiation budgets are obtained based on global daily visible and IR radiance measurements. The magnitude of cloud property variations and their effects on radiation increase strongly with decreasing space/time scales. Cloud properties are systematically different between land and ocean, with ocean having larger cloud cover with somewhat larger optical thicknesses and lower cloud top altitudes. Although cloud variations appear to be the primary cause of regional radiation budget variability at 5-30 daytime scales, the effects of their seasonal variations at larger spatial scales are less important than the changes associated with changes in solar declination and atmospheric/surface temperatures. The largest seasonal variations in radiation occur in the 30-60 deg latitude band in each hemisphere. Although clouds have a net cooling effect on the global, annual mean radiation balance at both the top of the atmosphere and the surface, their net effect on regional, seasonal balances is much more varied.

Rossow, William B.↗