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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1993

A carbon dioxide/methane greenhouse atmosphere on early Mars

One explanation for the formation of fluvial surface features on early Mars is that the global average surface temperature was maintained at or above the freezing point of water by the greenhouse warming of a dense CO2 atmosphere; however, Kasting has shown that CO2 alone is insufficient because the formation of CO2 clouds reduces the magnitude of the greenhouse effect. It is possible that other gases, such as NH3 and CH4, were present in the early atmosphere of Mars and contributed to the greenhouse effect. Kasting et al. investigated the effect of NH3 in a CO2 atmosphere and calculated that an NH3 mixing ratio of approximately 5 x 10 (exp -4) by volume, combined with a CO2 partial pressure of 4-5 bar, could generate a global average surface temperature of 273 K near 3.8 b.y. ago when the fluvial features are believed to have formed. Atmospheric NH3 is photochemically converted to N2 by ultraviolet radiation at wavelengths shortward of 230 nm; maintenance of sufficient NH3 concentrations would therefore require a source of NH3 to balance the photolytic destruction. We have used a one-dimensional photochemical model to estimate the magnitude of the NH3 source required to maintain a given NH3 concentration in a dense CO2 atmosphere. We calculate that an NH3 mixing ratio of 10(exp -4) requires a flux of NH3 on the order of 10(exp 12) molecules /cm-s. This figure is several orders of magnitude greater than estimates of the NH3 flux on early Mars; thus it appears that NH3 with CO2 is not enough to keep early Mars warm.

Brown, L. L.↗
NASA NTRS2004

Mass and Ozone Fluxes from the Lowermost Stratosphere

Net mass flux from the stratosphere to the troposphere can be computed from the heating rate along the 380K isentropic surface and the time rate of change of the mass of the lowermost stratosphere (the region between the tropopause and the 380K isentrope). Given this net mass flux and the cross tropopause diabatic mass flux, the residual adiabatic mass flux across the tropopause can also be estimated. These fluxes have been computed using meteorological fields from a free-running general circulation model (FVGCM) and two assimilation data sets, FVDAS, and UKMO. The data sets tend to agree that the annual average net mass flux for the Northern Hemisphere is about 1P10 kg/s. There is less agreement on the southern Hemisphere flux that might be half as large. For all three data sets, the adiabatic mass flux is computed to be from the upper troposphere into the lowermost stratosphere. This flux will dilute air entering from higher stratospheric altitudes. The mass fluxes are convolved with ozone mixing ratios from the Goddard 3D CTM (which uses the FVGCM) to estimate the cross-tropopause transport of ozone. A relatively large adiabatic flux of tropospheric ozone from the tropical upper troposphere into the extratropical lowermost stratosphere dilutes the stratospheric air in the lowermost stratosphere. Thus, a significant fraction of any measured ozone STE may not be ozone produced in the higher Stratosphere. The results also illustrate that the annual cycle of ozone concentration in the lowermost stratosphere has as much of a role as the transport in the seasonal ozone flux cycle. This implies that a simplified calculation of ozone STE mass from air mass and a mean ozone mixing ratio may have a large uncertainty.

Schoeberl, Mark R.↗
NASA NTRS1982

Periodic and aperiodic ozone variations in the middle and upper stratosphere

Umkehr, ozonesonde and satellite observations are used to determine the height/latitude distribution of the amplitude and phase of the periodic components of the variation in the ozone mixing ratio in the middle and upper stratosphere. The amplitude of the first (annual) harmonic is found to be small in the subtropics and to increase to a maximum at polar latitudes. In addition, it increases with height in the mid and upper stratosphere to an apparent maximum just below the stratosphere. The second (semi-annual) harmonic possesses an amplitude that is largest in tropical regions and in subpolar regions at a level of about 40 km. Very little ozone variation is seen above 30 km with dominant periods close to the quasi-biennial period of total ozone observed in the tropics. The percentage of the total variance of the ozone mixing ratio accounted for by the first harmonic is found to be larger than 60 percent at all heights from 20 deg to 60 deg latitude in both hemispheres (except near 40 km in the Northern Hemisphere).

London, J.↗
NASA NTRS2019

An Automated Detection Methodology for Dry Well-Mixed Layers

The intense surface heating over arid land surfaces produces dry well-mixed layers (WML) via dry convection. These layers are characterized by nearly constant potential temperature and low, nearly constant water vapor mixing ratio. To further the study of dry WMLs, we created a detection methodology and supporting software to automate the identification and characterization of dry WMLs from multiple data sources including rawinsondes, remote sensing platforms, and model products. The software is a modular code written in Python, an open source language. Radiosondes from a network of synoptic stations in North Africa were used to develop and test the WML detection process. The detection involves an iterative decision tree that ingests a vertical profile from an input data file, performs a quality check for sufficient data density, and then searches upward through the column for successive points where the simultaneous changes in water vapor mixing ratio and potential temperature are less than the specified maxima. If points in the vertical profile meet the dry WML identification criteria, statistics are generated detailing the characteristics of each layer in the profile. At the end of the vertical profile analysis, there is an option to plot analyzed profiles in a variety of file formats. Initial results show that the detection methodology can be successfully applied across a wide variety of input data and North African environments and for all seasons. It is sensitive enough to identify dry WMLs from other types of isentropic phenomena such as subsidence layers and distinguish the current day’s dry WML from previous days.

Stephen D. Nicholls↗
NASA NTRS1987

Airborne intercomparison of nitric oxide measurement techniques

Results from an airborne intercomparison of techniques to measure tropospheric levels of nitric oxide (NO) are discussed. The intercomparison was part of the National Aeronautics and Space Administration's Global Tropospheric Experiment and was conducted during missions flown in the fall of 1983 and spring of 1984. Instruments intercompared included a laser-induced fluorescence (LIF) system and two chemiluminescence instruments (CL). NO mixing ratios from below 5 pptv (parts per trillion by volume) to greater than 100 pptv were reported, with the majority less than 20 pptv. Good correlation was observed between the measurements reported by the CL and LIF techniques. The general level of agreement observed for the ensemble of measurements obtained during the two missions provides the basis from which one can conclude that equally 'valid' measurements of background levels of NO can be expected from either CL or LIF instruments. At the same time the periods of disagreement that were observed between the CL and LIF instruments as well as between the two CL instruments highlight the difficulty of obtaining reliable measurements with NO mixing ratios in the 5-20 pptv range and emphasize the vigilance that should be maintained in future NO measurements.

Hoell, James M., Jr.↗
NASA NTRS1991

Temperature sensitivity of differential absorption lidar measurements of water vapor in the 720-nm region

Recently measured properties of water vapor (H2O) absorption lines have been used in calculations to evalute the temperature sensitivity of differential absorption lidar (Dial) H2O measurements. This paper estimates the temperature sensitivity of H2O lines in the 717-733-nm region for both H2O mixing ratio and number density measurements, and discusses the influence of the H2O line ground state energies E-double-prime, the H2O absorption linewidths, the linewidth temperature dependence parameter, and the atmospheric temperature and pressure variations with altitude and location on the temperature sensitivity calculations. Line parameters and temperature sensitivity calculations for 67 H2O lines in the 720-nm band are given which can be directly used in field experiments. Water vapor lines with E-double-prime values in the 100-300/cm range were found to be optimum for Dial measurements of H2O number densities, while E-double-prime values in the 250-500/cm range were found to be optimum for H2O mixing ratio measurements.

Browell, Edward V.↗
NASA NTRS2015

Formaldehyde Production from Isoprene Oxidation Across NOx Regimes

The chemical link between isoprene and formaldehyde (HCHO) is a strong, non-linear function of NOx (= 27 NO + NO2). This relationship is a linchpin for top-down isoprene emission inventory verification from orbital HCHO column observations. It is also a benchmark for overall mechanism performance with regard to VOC oxidation. Using a comprehensive suite of airborne in situ observations over the Southeast U.S., we quantify HCHO production across the urban-rural spectrum. Analysis of isoprene and its major first-generation oxidation products allows us to define both a "prompt" yield of HCHO (molecules of HCHO produced per molecule of freshly-emitted isoprene) and the background HCHO mixing ratio (from oxidation of longer-lived hydrocarbons). Over the range of observed NOx values (roughly 0.1 - 2 ppbv), the prompt yield increases by a factor of 3 (from 0.3 to 0.9), while background HCHO increases by more than a factor of 2 (from 1.5 to 3.3 ppbv). We apply the same method to evaluate the performance of both a global chemical transport model (AM3) and a measurement-constrained 0-D chemical box model. Both models reproduce the NOx dependence of the prompt HCHO yield, illustrating that models with updated isoprene oxidation mechanisms can adequately capture the link between HCHO and recent isoprene emissions. On the other hand, both models under-estimate background HCHO mixing ratios, suggesting missing HCHO precursors, inadequate representation of later-generation isoprene degradation and/or under-estimated hydroxyl radical concentrations. Moreover, we find that the total organic peroxy radical production rate is essentially independent of NOx, as the increase in oxidizing capacity with NOx is largely balanced by a decrease in VOC reactivity. Thus, the observed NOx dependence of HCHO mainly reflects the changing fate of organic peroxy radicals.

VOC↗
NASA NTRS1981

Comparison of the Nimbus-4 BUV ozone data with the Ames two-dimensional model

Predictions by the Ames two-dimensional model of altitude, latitude and seasonal variations in ozone distribution are compared with the first two years of Nimbus 4 backscattered ultraviolet (BUV) measurements in a preliminary attempt at model verification. The ozone observations consist of mixing ratios on the 1-, 2-, 5-, and 10-mbar pressure surfaces zonally and time averaged to obtain seasonal means for 1970 and 1971. The model is based on chemical reaction and photolysis rate constants recommended by the NASA Panel for Data Evaluation (1979), diurnally averaged for latitudes from 80 deg N to 80 deg S and altitudes from 0 to 60 km with 5 deg horizontal and 2.5 km vertical grid spacings. The large altitude, latitude and seasonal variations observed in the data are found to agree well with model predictions. Examination of the sensitivity of the model predictions to various assumed parameters indicates that improvements in agreement may be obtained by variations of the odd chlorine mixing ratio, odd-nitrogen level and transport parameters.

Borucki, W. J.↗
NASA NTRS2020

Characterizing 15 Years of Saharan-like, Dry, Well-Mixed Air Layers in North Africa

The Saharan Air Layer (SAL) is a dry, well-mixed layer (WML) of warm and sometimes dusty air of nearly constant water vapor mixing ratio generated by the intense surface heating and strong, dry convection in the Sahara Desert, which has notable downstream impacts on the surface energy balance, organized convective system development, seasonal precipitation, and air quality. Characterizing both WMLs and SALs from the existing rawinsonde network has proven challenging because of its sparseness and inconsistent data reporting. Spurred on by this challenge, we previously created a detection methodology and supporting software to automate the identification and characterization of WMLs from multiple data sources including rawinsondes, remote sensing platforms, and model products. We applied our algorithm to each dataset at both its native and at a common (most coarse data product) vertical resolution to detect WMLs and their characteristics (temperature, mixing ratio, AOD, etc.) at each of the 53 rawinsonde launch sites in north Africa.

Nicholls, Stephen D.↗
NASA NTRS2011

Analysis of Oxygen Spectral Lines in the 1.27 Micron Band for the ASCENDS Mission

The ASCENDS mission requires simultaneous laser remote sensing of CO2 and O2 in order to convert CO2 column number densities to average column CO2 mixing ratios (XCO2). As such, the CO2 column number density and the O2 column number density will be utilized to derive the average XCO2 column. NASA Langley Research Center, working with its partners, is developing O2 lidar technology in the 1.26-1.27- m band for surface pressure measurements. The O2 model optical depth calculation is very sensitive to knowledge of the transmitted wavelengths and to the choice of Voigt input parameters. Modeling using the HITRAN database is being carried out to establish the evolution of candidate O2 absorption lines as a function of atmospheric parameters such as altitude, temperature, and pressure. Preliminary results indicate limitations of the Voigt profile and the need to utilize more advanced models which take into account line mixing, line narrowing, and speed dependence. In this paper, we evaluate alternative lineshape models to establish the optimum lineshapes which better account for the variability of individual O2 absorption lines at various atmospheric conditions. The combination of our modeling efforts with accurate laboratory measurements is anticipated to aid in achieving the desired CO2 mixing ratio measurement accuracy requirement of for the ASCENDS mission.

Pliutau, Denis↗
NASA NTRS1980

Comparison of the Nimbus-4 BUV ozone data with the Ames two-dimensional model

A comparison is made of the first two years of Nimbus 4 backscattered ultraviolet (BUV) ozone measurements with the predictions of the Ames two dimensional model. The ozone observations used consist of the mixing ratio on the 1, 2, 5, and 10 mb pressure surfaces. The data are zone and time averaged to obtain seasonal means for 1970 and 1971 and are found to show strong and repeatable meridional and seasonal dependencies. The model used for comparison with the observations extends from 80 N to 80 S latitude and from altitudes of 0 to 60 km with 5 deg horizontal grid spacing and 2.5 km vertical grid spacing. Chemical reaction and photolysis rates are diurnally averaged and the photodissociation rates are corrected for the effects of scattering. The large altitude, latitude, and seasonal changes in the ozone data agree with the model predictions. Model predictions of the sensitivity of the comparisons to changes in the assumed mixing ratios of water vapor, odd nitrogen, and odd chlorine, as well as to changes in the ambient temperature and transport parameters are also shown.

Borucki, W. J.↗
NASA NTRS2009

Turbulent CO2 Flux Measurements by Lidar: Length Scales, Results and Comparison with In-Situ Sensors

The vertical CO2 flux in the atmospheric boundary layer (ABL) is investigated with a Doppler differential absorption lidar (DIAL). The instrument was operated next to the WLEF instrumented tall tower in Park Falls, Wisconsin during three days and nights in June 2007. Profiles of turbulent CO2 mixing ratio and vertical velocity fluctuations are measured by in-situ sensors and Doppler DIAL. Time and space scales of turbulence are precisely defined in the ABL. The eddy-covariance method is applied to calculate turbulent CO2 flux both by lidar and in-situ sensors. We show preliminary mean lidar CO2 flux measurements in the ABL with a time and space resolution of 6 h and 1500 m respectively. The flux instrumental errors decrease linearly with the standard deviation of the CO2 data, as expected. Although turbulent fluctuations of CO2 are negligible with respect to the mean (0.1 %), we show that the eddy-covariance method can provide 2-h, 150-m range resolved CO2 flux estimates as long as the CO2 mixing ratio instrumental error is no greater than 10 ppm and the vertical velocity error is lower than the natural fluctuations over a time resolution of 10 s.

Gilbert, Fabien↗
NASA NTRS2003

Factors Affecting the Evolution of Hurricane Erin and the Distributions of Hydrometeors: Role of Microphysical Processes

Fine-resolution simulations of Hurricane Erin 2001 are conducted using the Penn State University/National Center for Atmospheric Research mesoscale model version 3.5 to investigate the role of thermodynamic, boundary layer and microphysical processes in Erin's growth and maintenance, and their effects on the horizontal and vertical distributions of hydrometeors. Through comparison against radar, radiometer, and dropsonde data collected during the Convection and Moisture Experiment 4, it is seen that realistic simulations of Erin are obtained provided that fine resolution simulations with detailed representations of physical processes are conducted. The principle findings of the study are as follows: 1) a new iterative condensation scheme, which limits the unphysical increase of equivalent potential temperature associated with most condensation schemes, increases the horizontal size of the hurricane, decreases its maximum rainfall rate, reduces its intensity, and makes its eye more moist; 2) in general, microphysical parameterization schemes with more categories of hydrometeors produce more intense hurricanes, larger hydrometeor mixing ratios, and more intense updrafts and downdrafts; 3) the choice of coefficients describing hydrometeor fall velocities has as big of an impact on the hurricane simulations as does choice of microphysical parameterization scheme with no clear relationship between fall velocity and hurricane intensity; and 4) in order for a tropical cyclone to adequately intensify, an advanced boundary layer scheme (e.g., Burk-Thompson scheme) must be used to represent boundary layer processes. The impacts of varying simulations on the horizontal and vertical distributions of different categories of hydrometeor species, on equivalent potential temperature, and on storm updrafts and downdrafts are examined to determine how the release of latent heat feedbacks upon the structure of Erin. In general, all simulations tend to overpredict precipitation rate and hydrometeor mixing ratios. The ramifications of these findings for quantitative precipitation forecasts (QPFs) of tropical cyclones are discussed.

McFarquhar, Greg M.↗
NASA NTRS1994

Uniqueness of a solution of a steady state photochemical problem: Applications to Mars

Based on the conservation of chemical elements in chemical reactions, a rule is proved that the number of boundary conditions given by densities and/or non-zero velocities should not be less than the number of chemical elements in the system, and the components given by densities and velocities should include all elements in the system. Applications of this rule to Mars are considered. It is proved that a problem of CO2-H2O chemistry in the lower and middle atmosphere of Mars, say, in the range of 0-80 km does not have an unique solution, if only CO2 and H2O densities are given at the lower boundary, while all other boundary conditions are fluxes. Two models of this type are discussed. These models fit the same boundary conditions, are balanced with a relative uncertainty of 10(exp -4) for H2, and predict the O2, CO, and H2 mixing ratios which differ by order of magnitude. One more species density, e.g. that of O2, should be specified at the boundary to obtain the unique solution. The situation is better if the upper boundary is extended to the exobase where thermal escape velocities of H and H2 can be specified. However, in this case, either oxygen nonthermal escape rate or the O2 density at the surface should be given as the boundary condition. Two models of Mars' photochemistry, with and without nitrogen chemistry, are considered. The oxygen nonthermal escape rate of 1.2 x 10(exp 8) cm(exp -2) s(exp -1) is given at 240 km and is balanced with the total hydrogen escape rate within uncertainty of 1 percent for both models. Both models fit the measured O2 and CO mixing ratios, the O3 line absorption at 9.6 microns, and the O2 1.27 microns dayglow within the uncertainties of the measured values; although, the model without nitrogen chemistry fits better.

Krasnopolsky, V. A.↗
NASA NTRS2017

Surface Ozone in the Colorado Northern Front Range and the Influence of Oil and Gas Development During FRAPPE/DISCOVER-AQ in Summer 2014

High mixing ratios of ozone (O3) in the northern Front Range (NFR) of Colorado are not limited to the urban Denver area but were also observed in rural areas where oil and gas activity is the primary source of O3 precursors. On individual days, oil and gas O3 precursors can contribute in excess of 30 ppb to O3 growth and can lead to exceedances of the EPA O3 National Ambient Air Quality Standard. Data used in this study were gathered from continuous surface O3 monitors for June-August 2013-2015 as well as additional flask measurements and mobile laboratories that were part of the FRAPPE/DISCOVER-AQ field campaign of July-August 2014. Overall observed O3 levels during the summer of 2014 were lower than in 2013, likely due to cooler and damper weather than an average summer. This study determined the median hourly surface O3 mixing ratio in the NFR on summer days with limited photochemical production to be approximately 45-55 ppb. Mobile laboratory and flask data collected on three days provide representative case studies of different O3 formation environments in and around Greeley, Colorado. Observations of several gases (including methane, ethane, CO, nitrous oxide) along with O3 are used to identify sources of O3 precursor emissions. A July 23 survey demonstrated low O3 (45-60 ppb) while August 3 and August 13 surveys recorded O3 levels of 75-80 ppb or more. August 3 exemplifies influence of moderate urban and high oil and gas O3 precursor emissions. August 13 demonstrates high oil and gas emissions, low agricultural emissions, and CO measurements that were well correlated with ethane from oil and gas, suggesting an oil and gas related activity as a NOx and O3 precursor source. Low isoprene levels indicated that they were not a significant contributor to O3 precursors measured during the case studies.

Pollution↗
NASA NTRS2001

Stratospheric Age Spectra and Mean Ages from In Situ Observations of Carbon Dioxide

In situ observations of CO2 obtained from 1992 through 2000 using the NASA ER-2 aircraft and high-altitude balloons show that seasonal and interannual variations in CO2 mixing ratios propagate from the troposphere into the lower stratosphere via the tropical tropopause, along with the long-term trend due to fossil fuel combustion. These signals spread laterally and vertically, providing detailed quantitative information about the transport history of sampled air. We have used these data to derive age spectra and mean ages that can be compared with results from models of the stratospheric circulation. For an air parcel at a point in the stratosphere, the age spectrum is defined as the probability distribution function for transit times from the tropical tropopause for each fluid element comprising the parcel. The mean age is the average transit time, corresponding to the first moment of the age spectrum. Age spectra have been derived for altitudes below approximately 20 km for the tropics and for northern midlatitudes where there is sufficient data and where the amplitudes of the seasonal and interannual oscillations in CO2 mixing ratios are large enough to be detected. Tropical age spectra are narrow, with seasonal variation indicating faster ascent during northern winter, consistent with a circulation driven by breaking of extratropical waves. The midlatitude CO2 data are consistent with bimodal age spectra, which could result from a subtropical "barrier" to horizontal exchange over a substantial altitude region. Seasonally resolved mean ages are available with nearly pole-to-pole coverage below 20 km and in the tropics and at middle and high northern latitudes up to the maximum altitude reached by the balloons (approximately 30 km). At ER-2 altitudes, steep meridional gradients in mean age are observed in the subtropics. Between 20 and 30 km, midlatitude air is approximately 2 years older than tropical air at the same altitude. The oldest air sampled was in the Arctic polar vortex with a mean age of .5 plus or minus 0.5 years. This value is much younger than mean ages inferred from simultaneous and previous observations of SF6 in the Arctic vortex, providing evidence for a mesospheric sink for SF6. The mean age in the midlatitude middle stratosphere (approximately 25-32 km) is nearly constant with respect to altitude at 5 plus or minus 0.5 years. Comparison with earlier balloon observations of CO2 dating back to the 1970s shows that the mean age of air in this region has been relatively invariant over the last 25 years.

Andrews, Arlyn E.↗
NASA NTRS2019

Global seasonal variations of the near-surface relative humidity levels on present-day Mars

We investigate the global seasonal variations of near-surface relative humidity and relevant attributes, like temperature and water vapor volume mixing ratio on Mars using calculations from modelled and measurement data. We focus on 2 AM local time snapshots to eliminate daily effects related to differences in insolation, and to be able to compare calculations based on modelling data from the Laboratoire de Météorologie Dynamique Mars General Circulation Model with the observations of Mars Global Surveyor Thermal Emission Spectrometer. We study the seasonal effects by examining four specific dates in the Martian year, the northern spring equinox, summer solstice, autumn equinox, and winter solstice. We identify three specific zones, where the near-surface relative humidity levels are systematically higher than in their vicinity regardless of season. We find that these areas coincide with low thermal inertia features, which control surface temperatures on the planet, and are most likely covered with unconsolidated fine dust with grain sizes smaller than ∼ 40 μm. By comparing the data of relative humidity, temperature and water vapor volume mixing ratio at three different heights (near-surface, ∼ 4m and ∼ 23m above the surface), we demonstrate that the thermal inertia could play an important role in determining near-surface humidity levels. We also notice that during the night the water vapor levels drop at ∼ 4m above the surface. This, together with the temperature and thermal inertia values, shows that water vapor likely condenses in the near-surface atmosphere and on the ground during the night at the three aforementioned regions. This condensation may be in the form of brines, wettening of the fine grains by adsorption or deliquescence. This study specifies areas of interest on the surface of present day Mars for the proposed condensation, which may be examined by in-situ measurements in the future.

Bernadett Pál↗
NASA NTRS1982

Mars water vapor, near-surface

In a previous paper we concluded that the temperature sensors aboard the Viking landers (VL-1 and VL-2) were detecting the water vapor frost point. Analysis of one Mars year of data at both lander sites substantiates this conclusion. At VL-1 it is found that the water vapor mixing ratio is constant with height through the bulk of the atmosphere, most of the time. Exceptions are during the onset phases of the two major dust storms when temporary enhancement of near-surface vapor occurs (the same phenomenon is observed at VL-2), and some depletion of near-surface vapor during the decay phase of the first storm, possibly the second storm as well. The former suggests near-surface, northward transport of water vapor with the storms. The latter suggests adsorption of vapor on dust particles followed by surface deposition. At VL-2, severe near-surface depletion of water vapor occurs during northern autumn and winter. The residual vapor is in equilibrium with the surface condensate observed at the site during this period, indicating that the source region for the condensate must be aloft with downward transport by dust fall-out. Since the near-surface water vapor mixing ratio and concentration at VL-1 generally parallels the column abundance over VL-1 obtained by the orbiters, this suggests that VL-1 can be used to give a measure of column abundance for as long as the temperature sensors remain operational.

Ryan, J. A.↗