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NASA NTRS2000

Time-Resolved Spectroscopy of Active Binary Stars

This NASA grant covered EUVE observing and data analysis programs during EUVE Cycle 5 GO observing. The research involved a single Guest Observer project 97-EUVE-061 "Time-Resolved Spectroscopy of Active Binary Stars". The grant provided funding that covered 1.25 months of the PI's salary. The activities undertaken included observation planning and data analysis (both temporal and spectral). This project was awarded 910 ksec of observing time to study seven active binary stars, all but one of which were actually observed. Lambda-And was observed on 1997 Jul 30 - Aug 3 and Aug 7-14 for a total of 297 ksec; these observations showed two large complex flares that were analyzed by Osten & Brown (1999). AR Psc, observed for 350 ksec on 1997 Aug 27 - Sep 13, showed only relatively small flares that were also discussed by Osten & Brown (1999). EUVE observations of El Eri were obtained on 1994 August 24-28, simultaneous with ASCA X-ray spectra. Four flares were detected by EUVE with one of these also observed simultaneously, by ASCA. The other three EUVE observations were of the stars BY Dra (1997 Sep 22-28), V478 Lyr (1998 May 18-27), and sigma Gem (1998 Dec 10-22). The first two stars showed a few small flares. The sigma Gem data shows a beautiful complete flare with a factor of ten peak brightness compared to quiescence. The flare rise and almost all the decay phase are observed. Unfortunately no observations in other spectral regions were obtained for these stars. Analysis of the lambda-And and AR Psc observations is complete and the results were published in Osten & Brown (1999). Analysis of the BY Dra, V478 Lyr and sigma Gem EUVE data is complete and will be published in Osten (2000, in prep.). The El Eri EUV analysis is also completed and the simultaneous EUV/X-ray study will be published in Osten et al. (2000, in prep.). Both these latter papers will be submitted in summer 2000. All these results will form part of Rachel Osten's PhD thesis.

Brown, Alexander↗
NASA NTRS1999

Origin, Bulk Chemical Composition and Physical Structure of the Galilean Satellites of Jupiter: A Post-Galileo Analysis

The origin of Jupiter and the Galilean satellite system is examined in the light of the new data that has been obtained by the NASA Galileo Project. In particular, special attention is given to a theory of satellite origin which was put forward at the start of the Galileo Mission and on the basis of which several predictions have now been proven successful. These predictions concern the chemical composition of Jupiter's atmosphere and the physical structure of the satellites. According to the proposed theory of satellite origin, each of the Galilean satellites formed by chemical condensation and gravitational accumulation of solid grains within a concentric family of orbiting gas rings. These rings were cast off equatorially by the rotating proto-Jovian cloud (PJC which contracted gravitationally to form Jupiter some 4 1/2 billion years ago. The PJC formed from the gas and grains left over from the gas ring that had been shed at Jupiter's orbit by the contracting proto-solar cloud (PSC Supersonic turbulent convection provides the means for shedding discrete gas rings. The temperatures T (sub n) of the system of gas rings shed by the PSC and PJC vary with their respective mean orbital radii R (sub n) (n = 0, 1,2,...) according as T (sub n) proportional to R (sub n) (exp -0.9). If the planet Mercury condenses at 1640 K, so accounting for the high density of that planet via a process of chemical fractionation between iron and silicates, then T (sub n) at Jupiter's orbit is 158 K. Only 35% of the water vapour condenses out. Thus fractionation between rock and ice, together with an enhancement in the abundance of solids relative to gas which takes place through gravitational sedimentation of solids onto the mean orbit of the gas ring, ensures nearly equal proportions of rock and ice in each of Ganymede and Callisto. Io and Europa condense above the H20 ice point and consist solely of hydrated rock (h-rock). The Ganymedan condensate consists of h-rock and H20 ice. For Callisto, NH3 ice makes up -5% of the condensate mass next to h-rock (approximately 50%) and H2O ice (approximately 45%). Detailed thermal and structural models for each of Europa, Ganymede and Callisto are constructed on the basis of the above initial bulk chemical compositions. For Europa (E), a predicted 2-zone model consisting of a dehydrated rock core of mass 0.912 M (sub E) and a 150 km thick frozen mantle of salty H2O yields a moment-of-inertia coefficient which matches the Galileo Orbiter gravity measurement. For Ganymede (G), a 3-zone model possessing an inner core of solid FeS and mass approximately 0.116 M (sub G), and an outer H2O ice mantle of mass approximately 0.502 M (sub G) is needed to explain the gravity data. Ganymede's native magnetic field was formed by thermoremanent magnetization of Fe3O4. A new Callisto (C) model is proposed consisting of a core of mass 0.826 M (sub C) containing a uniform mixture of h-rock (60% by mass) and H2O and NH3 ices, and capped by a mantle of pure ice. This model may have the capacity to yield a thin layer of liquid NH3 (raised dot) 2H2O at the core boundary, in line with Galileo's discovery of an induced magnetic field.

Prentice, A. J. R.↗
NASA NTRS1998

The Coronae of Moderate-Mass Giants in the Hertzsprung Gap and the Clump

We have used the Roentgensatellit (ROSAT), the Extreme Ultraviolet Explorer (EUVE), and the Hubble Space Telescope (HST) to measure X-ray and ultraviolet emissions of moderate-mass (APPROX. 2-3 solar mass) giants in the Hertzsprung gap (spectral types early F to mid-G) and the post-helium flash "clump" (approx. G8-K0). Our motivation was to document the evolution of hot coronae (T greater than 10(exp 6)K) along the post-main-sequence trajectories traveled by such stars in order to gain insight concerning the "X-ray deficiency" of the F-GO giants and the strong braking of stellar rotation at the red edge of the Hertzsprung gap. With few exceptions, Hertzsprung gap and clump giants observed by ROSAT PSPC show hot (T approx. 10(exp 7)K) coronal energy distributions, regardless of any X-ray deficiency, EUVE spectra of gap star 31 Com (G0 111) indicate a broad coronal emission measure hump at approx. 10(exp 7.2)K, while the active clump giant beta Ceti (K0 III) displays a sharp peak at approx. 10(exp 6.8)K, as seen previously in the mixed clump/gap binary Capella (alpha Aur: G8 III + G0 III). The gap giants upsilon Peg (F8 III) and 24 UMa (G4 III) have EUV emissions of intermediate temperature (approx. 10(exp 7.0)K). The stars 31 Com, psi(sup 3) Psc (G0 III), and beta Cet exhibit redshifted transition zone (TZ: approx. 10(exp 5)K) lines in HST GHRS spectra, as reported earlier in Procyon (alpha CMi: F5 IV-V) and Capella G0. Such redshifts on the Sun are thought to signify flows in magnetic loops. beta Cas (F2 III)-a rare soft coronal source among the gap stars-displays blueshifts of C iv and 0 iv], although emissions at cooler and hotter temperatures are near the photospheric velocity. The remarkably broad line profiles of the fastest rotating gap giants suggest that the 10(exp 5) K "subcoronal " emission zones extend to h approx. R(sub *) above the photosphere, about 50 scale heights. In contrast to the TZ line redshifts, the upper chromospheric emissions (e.g., Mg II and Si III) of 31 Com and upsilon(sup 3) Psc have blueshifted cores. Blue-asymmetric peaks in the solar Mg a lines are thought to indicate dynamical heating in the chromosphere. Observations of the H(sub I) Ly(alpha) feature of 31 Com taken 9 months apart reveal striking profile changes, reminiscent of those noted previously in the Ly(alpha) blue peak of the Capella G0 star. We used the far-ultraviolet diagnostics, in combination with ROSAT X-ray photometry and EUVE high-excitation line strengths, to constrain physical models of the stellar outer atmospheres. Quasi-static magnetic loops can simulate the empirical coronal emission measures of the giant stars, but the inferred pressures for sensible loop lengths conflict with direct measurements of subcoronal densities. Furthermore, the high rate of emission at approx. 10(exp 5) K cannot be explained by thermal conduction down the legs of hot quasi-static loops. On the other hand, the possible existence of elongated (l - R(sub *) emission structures on the gap giants leads to a speculative scenario to explain the X-ray deficiency. It is based on the increased importance of the dynamical filling phase ("explosive evaporation") of the loop life cycle; conductive cooling, yielding TZ emissions at the footpoints, when the heating is interrupted; and the possibility for transitions between " hot " and " cool " energy balance solutions owing to dynamical suspension and centrifugal trapping of the cooling gas. The long loops might represent a vestigial global " magnetosphere " inherited from the main-sequence phase, which ultimately is disrupted near approx. G0 by the deepening convective envelope and growth of a more solar-like dynamo. Coronal emissions might be boosted temporarily as the X-ray deficiency is removed but soon would be quenched by wind braking previously inhibited by the magnetospheric "dead zone."

Ayres, Thomas R.↗
NASA NTRS2000

Trajectory Hunting: A Case Study of Rapid Chlorine Activation in December 1992 as Seen by UARS

Trajectory hunting (i.e., a technique to find air parcels sampled at least twice over the course of a few days) is applied to analyze Upper Atmosphere Research Satellite (UARS) measurements in conjunction with the Atmospheric and Environmental Research, Inc. (AER) photochemical box model. As a case study, we investigate rapid chlorine activation in the Arctic lower stratosphere on December 29, 1992 associated with a polar stratospheric cloud (PSC) event. Eleven air parcels that have been sampled several times along five-day trajectories at the 465 K (approx. 46 hPa), 520 K (approx. 31 hPa), and 585 K (approx. 22 hPa) levels were investigated. For the first time, the latest versions of the Cryogenic Limb Array Etalon Spectrometer (CLAES, version 9) and Microwave Limb Sounder (MLS, version 5) data sets are analyzed, and their consistency is assessed. A detailed sensitivity study with the AER photochemical box model along these trajectories leads to the conclusion that for the December 24-29, 1992 episode: (1) the individual CLAES ClONO2 and MLS ClO measurements are self-consistent within their uncertainties; and (2) most of the time, UARS measurements of ClO, ClONO2, HNO3, and aerosol extinction at 780 cm(exp -1) agree within the range of their uncertainties with the model calculations. It appears that the HNO3 and aerosol extinction measurements for four parcels at 520 K look more supportive for the nitric acid trihydrate (NAT) scheme, However, the uncertainties in the individual UARS measurements and UK Meteorological Office temperature do not allow a definite discrimination between the NAT and supercooled ternary solution (STS) PSC schemes for this chlorine activation episode in December 1992.

Danilin, M. Y.↗
NASA NTRS2001

Simulation of MC-1 Engine on Real-Time Station

The MC-1 rocket engine is a new, 60,000-pound-thrust engine designed to boost small spacecraft carrying payloads weighing up to 500 pounds. The engine was designed in-house at NASA's Marshall Space Flight Center (MSFC) in Huntsville, Alabama, and built by SUMMA Technology, Inc. A vital part of the success of the engine development was the verification of the Propulsion System Controller (PSC) used to control the MC-1 engine during development testing at test facilities in Mississippi and California. The MC-1 engine simulation software was developed on the Applied Dynamics, Inc.'s Real-Time Station (RTS) computer system (ESL) to verify the PSC's hardware and software performance in the Marshall Avionics System Testbed's (MAST) Engine Simulation Lab at the MSFC. The engine model includes the simulation of pressure transducers, thermocouple sensors and valve-positions.

Ly, William↗
NASA NTRS2001

Comparison of ER-2 Aircraft and POAM-III, MLS, and SAGE-II Satellite Measurements During SOLVE Using Traditional Correlative Analysis and Trajectory Hunting Technique

We compared the version 5 Microwave Limb Sounder (MLS) aboard the Upper Atmosphere Research Satellite (UARS), version 3 Polar Ozone and Aerosol Measurement-III (POAM-111) aboard the French satellite SPOT-IV, version 6.0 Stratospheric Aerosol and Gas Experiment 11 (SAGE-II) aboard the Earth Radiation Budget Satellite, and NASA ER-2 aircraft measurements made in the northern hemisphere in January-February 2000 during the SAGE III Ozone Loss and Validation Experiment (SOLVE). This study addresses one of the key scientific objectives of the SOLVE campaign, namely, to validate multi-platform satellite measurements made in the polar stratosphere during winter. This intercomparison was performed using a traditional correlative analysis (TCA) and a trajectory hunting technique (THT). Launching backward and forward trajectories from the points of measurement, the THT identifies air parcels sampled at least twice within a prescribed match criterion during the course of 5 days. We found that the ozone measurements made by these four instruments agree most of the time within 110% in the stratosphere up to 1400 K (approximately 35 km). The water vapor measurements from POAM-III and the ER-2 Harvard Lyman-alpha hygrometer and JPL laser hygrometer agree to within 10.5 ppmv (or about +/-10%) in the lower stratosphere above 380 K. The MLS and ER-2 ClO measurements agree within their error bars for the TCA. The MLS and ER-2 nitric acid measurements near 17-20 km altitude agree within their uncertainties most of the time with a hint of a positive offset by MLS according to the TCA. We also applied the AER box model constrained by the ER-2 measurements for analysis of the ClO and HN03 measurements using the THT. We found that: (1) the model values of ClO are smaller by about 0.3-0.4 (0.2) ppbv below (above) 400 K than those by MLS and (2) the HN03 comparison shows a positive offset of MLS values by approximately 1 and 1-2 ppbv below 400 K and near 450 K, respectively. It is hard to quantify the HN03 offset in the 400-440 K range because of the high sensitivity of nitric acid to the PSC schemes. Our study shows that, with some limitations (like HN03 comparison under PSC conditions), the THT is a more powerful tool for validation studies than the TCA, making conclusions of the comparison statistically more robust.

Danilin, M. Y.↗
NASA NTRS2001

MHD Instability and Turbulence in the Tachocline

In this quarter we have begun simulations on the Cray T3E at PSC and we are debugging our code on the TSC. The PSC simulations are examining stratified shear turbulence with a flow-aligned magnetic field and passive tracer particles. We have conducted analysis of neutral simulations to establish a firm basis of comparison. Second-order structure functions have been computed, fit, and compared to theoretical expressions relating the dissipation fields and the structure-function-fit parameters. Agreement with high-Reynolds number observations is excellent, giving us confidence that the lower-Re simulations are relevant to higher-Re flows. We have also evaluated the neutral layer anisotropy.

Werne, Joseph↗
NASA NTRS2001

Composition of Hydrothermal Vent Microbial Communities as Revealed by Analyses of Signature Lipids, Stable Carbon Isotopes and Aquificales Cultures

Extremely thermophilic microbial communities associated with the siliceous vent walls and outflow channel of Octopus Spring, Yellowstone National Park, have been examined for lipid biomarker and carbon isotopic signatures. These data were compared with that obtained from representatives of three Aquificales genera. Thermocrinis ruber, Thermocrinis sp. HI, Hydrogenobacter thermophilus, Aquifex pyrophilus and Aquifex aeolicus all contained phospholipids composed not only of the usual ester-linked fatty acids, but also ether-linked alkyl moieties. The fatty acids of all cultured organisms were dominated by very distinct pattern of n-C-20:1 and cy-C-21 compounds. The alkyl glycerol ethers were present primarily as C-18:0 monoethers with the exception of the Aquifex spp. in which dialkyl glycerol ethers with a boarder carbon-number distribution were also present. These Aquificales biomarker lipids were the major constituents in the lipid extracts of the Octopus Spring microbial samples. Two natural samples, a microbial biofilm growing in association with deposition of amorphous silica on the vent walls at 92 C, and the well-known "pink-streamer community" (PSC), siliceous filaments of a microbial consortia growing in the outflow channel at 87 C were analyzed. Both the biofilm and PSC samples contained mono- and dialkyl glycerol ethers with a prevalence of C-18 and C-20 alkyls. Phospholipid fatty acids were comprised of both the characteristic. Additional information is contained in the original extended abstract.

Jahnke, Linda L.↗
NASA NTRS2001

Microphysical Modelling of the 1999-2000 Arctic Winter: Chlorine Activation and Ozone Depletion - 2

The effect of a range of assumptions about polar stratospheric clouds (PSCs) on ozone depletion has been assessed using at couple microphysical/photochemical model. The composition of the PSCs was varied (ternary solutions, nitric acid trihydrate, nitric acid dehydrate, or ice), as were parameters that affected the levels of denitrification and dehydration. Ozone depletion was affected by assumptions about PSC freezing because of the variability in resultant nitrification chlorine activation in all scenarios was similar despite the range of assumed PSC compositions. Vortex-average ozone loss exceeded 40% in the lower stratosphere for simulations without nitrification an additional ozone loss of 15-20% was possible in scenarios where vortex-average nitrification reached 60%. Ozone loss intensifies non-linearly with enhanced nitrification in air parcels with 90% nitrification 40% ozone loss in mid-April can be attributed to nitrification alone. However, these effects are sensitive to the stability of the vortex in springtime: nitrification only began to influence ozone depletion in mid-March.

Drdla, K.↗
NASA NTRS2001

Simulations of Polar Stratospheric Clouds and Denitrification Using Laboratory Freezing Rates

During the 1999-2000 Arctic winter, the SAGE (Stratospheric Aerosol and Gas Experiment) III Ozone Loss and Validation Experiment (SOLVE) provided evidence of widespread solid-phase polar stratospheric clouds (PSCs) accompanied by severe nitrification. Previous simulations have shown that a freezing process occurring at temperatures above the ice frost point is necessary to explain these observations. In this work, the nitric acid freezing rates measured by Salcedo et al. and discussed by Tabazadeh et al. have been examined. These freezing rates have been tested in winter-long microphysical simulations of the 1999-2000 Arctic vortex evolution in order to determine whether they can explain the observations. A range of cases have been explored, including whether the PSC particles are composed of nitric acid dihydrate or trihydrate, whether the freezing process is a bulk process or occurs only on the particle surfaces, and uncertainties in the derived freezing rates. Finally, the possibility that meteoritic debris enhances the freezing rate has also been examined. The results of these simulations have been compared with key PSC and denitrification measurements made by the SOLVE campaign. The cases that best reproduce the measurements will he highlighted, with a discussion of the implications for our understanding of PSCs.

Drdla, Katja↗
NASA NTRS2002

XTE Observations of Intermediate Polars: RXTE TOO Observations of Supernovae

Two Intermediate Mars were observed with XTE (X-Ray Timing Explorer): PQ Gem and AO Psc. A very preliminary analysis for PQ Gem was presented at the Annapolis Workshop on Magnetic Cataclysmic Variables. At about the same time, the XTE team created a new background estimator for faint sources. The PQ Gem data must be reanalyzed using the new background estimator. The data for AO Psc have been analyzed and await the analysis of PQ Gem.

Schlegel, E.↗
NASA NTRS2003

Comparing Model Ozone Loss during the SOLVE and SOLVE-2 Winters

Model simulations have been used to analyze the factors influencing ozone loss during the 1999-2000 and 2002-2003 js. For both winters, the evolution of the Arctic vortex from November to April has been simulated using a trajectory-based microphysical and photochemical model. Extensive PSC formation and strong ozone depletion are evident in both winters. However, the ozone loss begins earlier in the 2002-2003 winter, with significant ozone depletion by early January. Analysis of the model results shows that during December 2002 not only cold temperatures but also the vortex structure was critical, allowing PSC-processed air parcels to experience significant solar exposure. The resultant ozone loss can be differentiated from ozone loss that occurs in the springtime, in particular because of the continued exposure to PSCs. For example, chlorine reactivation by the PSCs causes ozone loss to be insensitive to denitrification. Therefore, diagnosing the extent of ozone loss early in the winter is critical In understanding the overall winter-long ozone depletion.

Drdla, K.↗
NASA NTRS2003

Microphysical Modelling of the 1999-2000 Arctic Winter: Impact of Homogeneous Freezing on PSCs - 3

Simulations of the 1999-2000 winter have tested the effect on polar stratospheric clouds (PSCs) of the homogeneous freezing of liquid ternary solutions into nitric acid trihydrate (NAT) and nitric acid dihydrate (NAD). Proposed laboratory-derived volume-based and surface-based homogeneous freezing rates have both been examined, including different assumptions about the extrapolation of laboratory measurements to atmospheric conditions. Widespread PSC formation and denitrification are possible in several of the scenarios examined. However, the simulations are all unable to explain the solid-phase PSCs observed early in the 1999-2000 winter, and are unable to reproduce the measured extent of vortex denitrification. These problems can both be attributed to the relatively cold temperatures, more than 5 K below the NAT condensation point, necessary for effective homogeneous freezing. Therefore synoptic-scale homogeneous freezing appears unlikely to be the primary mechanism responsible for solid-phase PSC formation.

Drdla, K.↗
NASA NTRS2004

Hot Structure Control Surface Progress for X-37 Technology Development Program

The NASA Marshall Space Flight Center (MSFC) has been leading the development of technologies that will enable the development, fabrication, and flight of the automated X-37 Orbital Vehicle (OV). With the Administration s recent announcement of the Vision for Space Exploration, NASA placed the X-37 OV design on hold while developing detailed requirements for a Crew Exploration Vehicle, but has continued funding the development of high-risk, critical technologies for potential future space exploration vehicle applications. Hot Structure Control Surfaces (HSCS) technology development is one of the high-priority areas being funded at this time. The goal of HSCS research is to mitigate risk by qualifying the lightest possible components that meet the stringent X-37 OV weight and performance requirements, including Shuttle-type reen- try environments with peak temperatures of 2800 OF. The small size of the X-37 OV (25.7-feet long and 14.9-foot wingspan) drives the need for advanced HSCS because the vehicle's two primary aerodynamic surfaces, the flaperons and ruddervators, have thicknesses ranging from approximately 5 in. down to 1 in. Traditional metallic or polymer-matrix composites covered with tile or blanket thermal protection system (TPS) materials cannot be used as there is insufficient volume to fabricate such multi-component structures. Therefore, carbon-carbon (C-C) and carbodsilicon-carbide (C-SiC) composite HSCS structures are being developed in parallel by two teams supporting the X-37 prime contractor (The Boeing Company). The Science Applications International Coy. (SAIC) and Carbon-Carbon Advanced Technologies, Inc. (C-CAT) team is developing the C-C HSCS, while the General Electric Energy Power Systems Composites (GE-PSC) and Materials Research and Design (MRD) team is developing the C-SiC HSCS. These two teams were selected to reduce the high level of risk associated with developing advanced control surface components. They have continued HSCS development work as part of the X-37 critical technology development contract. The SAIC/C-CAT team is using Advanced Carbon-Carbon (ACC) because its fabrication is very similar to the process used for Space Shuttle Reinforced Carbon-Carbon fabrication, including the Sic-based pack cementation conversion coating systems using with both materials. ACC was selected over RCC because it has much higher tension and compressions strengths, and because T-300 fiber is readily available, whereas RCC rayon fiber is no longer manufactured. The GE-PSC/MRD team is using a T-300 fiber-reinforced Sic matrix composite material densified by chemical vapor infiltration. The C-Sic material has an Sic-based environmental barrier coating. Major accomplishments have been made over the past year by both HSCS teams. C-C and C- SiC flaperon subcomponents, which are truncated full-scale versions of flight hardware, have been fabricated and are undergoing testing at the NASA Dryden Flight Research Center, NASA Langley Research Center, and U.S. Air Force Research Laboratory. By the end of 2004, ruddervator subcomponents also will be delivered and tested. As NASA moves forward in realizing the Vision for Space Exploration, it will continue to invest in advanced research and development aimed at making new generations of spacecraft safer, more reliable, and more affordable. The X-37 HSCS effort ultimately will benefit the Agency's vision and mission.

Valentine, P. G.↗
NASA NTRS2004

Quasi-Liquid Layer Formation on Ice under Stratospheric Conditions

Characterization of the interaction of hydrogen chloride (HCl) with ice is essential to understanding at a molecular level the processes responsible for ozone depletion involving polar stratospheric cloud (PSC) particles. To explain the catalytic role PSC particle surfaces play during chlorine activation, we proposed previously that HCl induces the formation of a disordered region on the ice surface, a quasi-liquid layer (QLL), at stratospheric conditions. The QLL is known to exist in pure ice crystals at temperatures near the melting point, but its existence at stratospheric temperatures (-85 C to -70 C) had not been reported yet. We studied the interaction of HCl with ice under stratospheric conditions using the complementary approach of a) ellipsometry to directly monitor the ice surface, using chemical ionization mass spectrometry (CIMS) to monitor the gas phase species present in the ellipsometry experiments, and b) flow-tube experiments with CIMS detection. Here we show that trace amounts of HCl induce QLL formation at stratospheric temperatures, and that the QLL enhances the chlorine-activation reaction of HCl with chlorine nitrate (ClONO2), and also enhances acetic acid (CH3COOH) adsorption.

McNeill, V. Faye↗
NASA NTRS2004

The Remarkable 2003-2004 Winter and Other Recent Warm Winters in the Arctic Stratosphere Since the Late 1990s

The 2003-2004 Arctic winter was remarkable in the 40-year record of meteorological analyses. A major warming beginning in early January 2004 led to nearly two months of vortex disruption with high-latitude easterlies in the middle to lower stratosphere. The upper stratospheric vortex broke up in late December, but began to recover by early January, and in February and March was the strongest since regular observations began in 1979. The lower stratospheric vortex broke up in late January. Comparison with two previous years, 1984-1985 and 1986-1987, with prolonged mid-winter warming periods shows unique characteristics of the 2003-2004 warming period: The length of the vortex disruption, the strong and rapid recovery in the upper stratosphere, and the slow progression of the warming from upper to lower stratosphere. January 2004 zonal mean winds in the middle and lower stratosphere were over two standard deviations below average. Examination of past variability shows that the recent frequency of major stratospheric warmings (seven in the past six years) is unprecedented. Lower stratospheric temperatures were unusually high during six of the past seven years, with five having much lower than usual potential for PSC formation and ozone loss (nearly none in 1998-1999, 2001-2002 and 2003-2004, and very little in 1997-1998 and 2000-2001). Middle and upper stratospheric temperatures, however, were unusually low during and after February. The pattern of five of the last seven years with very low PSC potential would be expected to occur randomly once every approximately 850 years. This cluster of warm winters, immediately following a period of unusually cold winters, may have important implications for possible changes in interannual variability and for determination and attribution of trends in stratospheric temperatures and ozone.

Manney, Gloria L.↗
NASA NTRS2005

Seasonal And Regional Differentiation Of Bio-Optical Properties Within The North Polar Atlantic

Using data collected during spring and summer seasons in the north polar Atlantic we examined the variability of the spectral absorption, a(lambda), and backscattering, b(sub b)(lambda), coefficients of surface waters and its relation to phytoplankton pigment concentration and composition. For a given chlorophyll a concentration (TChla), the concentrations of photosynthetic carotenoids (PSC), photoprotective carotenoids (PPC), and total accessory pigments (AP) were consistently lower in spring than in summer. The chlorophyll-specific absorption coefficients of phytoplankton and total particulate matter were also lower in spring, which can be partly attributed to lower proportions of PPC, PSC, and AP in spring. The spring values of the green-to-blue band ratio of the absorption coefficient were higher than the summer ratios. The blue-to-green ratios of backscattering coefficient were also higher in spring. The higher b(sub b) values and lower blue-to-green b(sub b) ratios in summer were likely associated with higher concentrations of detrital particles in summer compared to spring. Because the product of the green-to-blue absorption ratio and the blue-to-green backscattering ratio is a proxy for the blue-to-green ratio of remote-sensing reflectance, we conclude that the performance of ocean color band-ratio algorithms for estimating pigments in the north polar Atlantic is significantly affected by seasonal shifts in the relationships between absorption and TChla as well as between backscattering and TChla. Intriguingly, however, fairly good estimate of the particulate beam attenuation coefficient at 660 nm (potential measure of total particulate matter or particulate organic carbon concentration) can be obtained by applying a single blue-to-green band-ratio algorithm for both spring and summer seasons.

Stramska, Malgorzata↗
NASA NTRS2006

Chemical Observations of a Polar Vortex Intrusion

An intrusion of vortex edge air in D the interior of the Arctic polar vortex was observed on the January 31,2005 flight of the NASA DC-8 aircraft. This intrusion was identified as anomalously high values of ozone by the AROTAL and DIAL lidars. Our analysis shows that this intrusion formed when a blocking feature near Iceland collapsed, allowing edge air to sweep into the vortex interior. along the DC-8 flight track also shows the intrusion in both ozone and HNO3. Polar Stratospheric Clouds (PSCs) were observed by the DIAL lidar on the DC-8. The spatial variability of the PSCs can be explained using MLS HNO3 and H2O observations and meteorological analysis temperatures. We also estimate vortex denitrification using the relationship between N2O and HNO3. Reverse domain fill back trajectory calculations are used to focus on the features in the MLS data. The trajectory results improve the agreement between lidar measured ozone and MLS ozone and also improve the agreement between the HNO3 measurements PSC locations. The back trajectory calculations allow us to compute the local denitrification rate and reduction of HCl within the filament. We estimate a denitrification rate of about lO%/day after exposure to below PSC formation temperature. Analysis of Aura MLS observations made

Schoeberl, M. R.↗