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All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Low frequency variability and tropical-extratropical interactions

In this investigation of relationships between mid-latitude 500 mb anomalies and tropical heating anomalies on the time scales of weeks to seasons are studied using outgoing IR to characterize the tropical convection heating. The data are first used to form 5-day means and the mean seasonal cycle and the interannual variability of seasonal means are then removed. The time scales considered are then between about 10 days and 90 days. By correlating the mid-latitude height anomalies with the tropical precipitation anomalies it can be shown that, on the time scales considered here, the predominant correlation patterns are those associated with Rossby waves propagating from mid-latitudes into the tropics and influencing the tropical convection. The mid-latitude Rossby waves can significantly influence convection to within 5 degrees of the equator.

Hartmann, D. L.↗
NASA NTRS1993

Springtime stratospheric water vapour in the Southern Hemisphere as measured by MLS

The effects of the break-up of the Antarctic vortex on the water vapor distribution are studied using MLS measurements of water vapor made during September 1991 and November 1991. In early November at 22 hPa a moist area is found within the polar vortex, consistent with an observed descent of order 10 km and strong radiative cooling. As the vortex erodes (beginning of November 1991), parcels of moist air become detached from the edge of the vortex and mix rapidly (within 2-3 days) with drier mid-latitude air. When the vortex breaks up (mid-November), larger parcels of moist air from both the edge and the inner vortex migrate to mid-latitudes. These parcels have a longer lifetime than those produced by vortex erosion, probably because they are correlated with higher potential vorticity gradients. The break-up of the vortex is accompanied by a mean adiabatic equatorward transport resulting in a significant increase in midstratospheric water vapor values at mid-latitudes in late spring.

Harwood, R. S.↗
NASA NTRS1994

Digital Linear Tape (DLT) technology and product family overview

The demand that began a couple of years ago for increased data storage capacity continues. Peripheral Strategies (a Santa Barbara, California, Storage Market Research Firm) projects the amount of data stored on the average enterprise network will grow by 50 percent to 100 percent per year. Furthermore, Peripheral Strategies says that a typical mid-range workstation system containing 30GB to 50GB of storage today will grow at the rate of 50 percent per year. Dan Friedlander, a Boulder, Colorado-based consultant specializing in PC-LAN backup, says, 'The average NetWare LAN is about 8GB, but there are many that have 30GB to 300GB.....' The substantial growth of storage requirements has created various tape technologies that seek to satisfy the needs of today's and, especially, the next generations's systems and applications. There are five leading tape technologies in the market today: QIC (Quarter Inch Cartridge), IBM 3480/90, 8mm, DAT (Digital Audio Tape) and DLT (Digital Linear Tape). Product performance specifications and user needs have combined to classify these technologies into low-end, mid-range, and high-end systems applications. Although the manufacturers may try to position their products differently, product specifications and market requirements have determined that QIC and DAT are primarily low-end systems products while 8mm and DLT are competing for mid-range systems applications and the high-end systems space, where IBM compatibility is not required. The 3480/90 products seem to be used primarily in the IBM market, for interchangeability purposes. There are advantages and disadvantages for each of the tape technologies in the market today. We believe that DLT technology offers a significant number of very important features and specifications that make it extremely attractive for most current as well as emerging new applications, such as Hierarchical Storage Management (HSM). This paper will demonstrate why we think that the DLT technology and family of DLT products will become the technology of choice for most new applications in the mid-range and high-end (non-IBM) markets.

Lignos, Demetrios↗
NASA NTRS1993

Voyager Photometry of Saturn's A Ring

Saturn's A Ring samples a wide range of dynamical environments, from the relatively unperturbed, optically thick inner region to the outer part of the ring, which contains numerous density waves. We analyze Voyager images of the A Ring to determine how the reflectivity of different radial regions varies with lighting and viewing geometry. We model our data with a classical radiative transfer code that includes the illumination of the rings by the Sun and Saturn. The particles in the inner and mid-A Ring have Bond albedos near 0.5 and are more backscattering than satellites of comparable albedo. The region outside the Encke Gap becomes progressively less backscattering with increasing radius. Particle properties change abruptly outside the Keeler Gap; particles here have an albedo near 0.6 and a Lambert-like phase function. In contrast with previous suggestions, the abundance of free, submicrometer "dust" is small throughout the entire A Ring; this conclusion holds even in the outermost A Ring, which is strongly perturbed by density waves. Models derived from low-phase data, assuming only macroscopic particles, correctly predict the highphase reflectivity of the outer A Ring and individual strong density waves in the mid-A Ring. However, the inner and mid-A Ring are typically darker at high phase by a factor of two than our models predict. This discrepancy may be due to the reduced multiple scattering from a layer in which the particles are more closely packed. We have also studied the quadrupole azimuthal brightness asymmetry of the A Ring. The asymmetry has a full amplitude of 35% in the mid-A Ring in low-phase Voyager 2 images. We present results on its behavior and possible implications for the structure of the rings. Finally, we compare our results with studies using other data sets to synthesize our current understanding of the nature of the A Ring.

Dones, Luke↗
NASA NTRS1998

Multiple GISS AGCM Hindcasts and MSU Versions of 1979-1998

Multiple realizations of the 1979-1998 time period have been simulated by the Goddard Institute for Space Studies Atmospheric General Circulation Model (GISS AGCM) to explore its responsiveness to accumulated forcings, particularly over sensitive agricultural regions. A microwave radiative transfer postprocessor has produced the AGCM's lower tropospheric, tropospheric and lower stratospheric brightness temperature (Tb) time series for correlations with the various Microwave Sounding Unit (MSU) time series available. MSU maps of monthly means and anomalies were also used to assess the AGCM's mean annual cycle and regional variability. Seven realizations by the AGCM were forced by observed sea surface temperatures (sst) through 1992 to gather rough standard deviations associated with internal model variability. Subsequent runs hindcast January 1979 through April 1998 with an accumulation of forcings: observed ssts, greenhouse gases, stratospheric volcanic aerosols. stratospheric and tropospheric ozone and tropospheric sulfate and black carbon aerosols. The goal of narrowing gaps between AGCM and MSU time series was complicated by MSU time series, by Tb simulation concerns and by unforced climatic variability in the AGCM and in the real world. Lower stratospheric Tb correlations between the AGCM and MSU for 1979-1998 reached as high as 0.91 +/-0.16 globally with sst, greenhouse gases, volcanic aerosol, stratospheric ozone forcings and tropospheric aerosols. Mid-tropospheric Tb correlations reached as high as 0.66 +/-.04 globally and 0.84 +/-.02 in the tropics. Oceanic lower tropospheric Tb correlations similarly reached 0.61 +/-.06 globally and 0.79 +/-.02 in the tropics. Of the sensitive agricultural areas considered, Nordeste in northeastern Brazil was simulated best with mid-tropospheric Tb correlations up to 0.75 +/- .03. The two other agricultural regions, in Africa and in the northern mid-latitudes, suffered from higher levels of non-sst variability. Zimbabwe had a maximum mid-tropospheric correlation of 0.54 +/- 0.11 while the U.S. Cornbelt had only 0.25 +/- .10. Precipitation and surface temperature performance are also examined over these regions. Correlations of MSU and AGCM time series mostly improved with addition of explicit atmospheric forcings in zonal bands but not in agricultural regional bins each encompassing only six AGCM gridcells.

Shah, Kathryn Pierce↗
NASA NTRS1998

Trends in the Annual Frequency of Atlantic Basin Intense Hurricanes: Implications for the Near-Term

During the interval of 1944-1997, 120 intense hurricanes (category 3, 4, or 5 on the Saffir-Simpson hurricane scale) have been observed in the Atlantic basin. These intense hurricanes have had an observed annual frequency of 0-7 events per year (having a mean, mode, and median equal to about 2 events per year), being preferentially lower during El Ninio years and higher during non-El Ninio years. Also, it has recently been established that a long-term downward trend in the annual frequency of intense hurricanes, spanning about five decades, has taken place, although this trend can, alternatively, be explained as a shift from a more active state prior to the mid 1960's to a less active state thereafter (rather than as a simple linear decline). In this paper, on the basis of 10-yr moving averages, the long4erm trend of the frequency of intense hurricanes is compared against one for the annual mean temperature at Armagh Observatory, Northern Ireland (which serves as a proxy for climatic change). Interestingly, the two sets of 10-yr moving averages correlate extremely well, especially, when incorporating a slight 6-yr lag between them (with temperature leading; r = 0.90). This suggests that the current leading trend of temperature, which had been downward, but now is upward, may portend a return to the more active state for intense hurricanes. Thus, the 1998 season (presuming the abatement of El Ninio prior to the start of the hurricane season), and for several years thereafter (at least, into the early years of the next millennium), may have an annual frequency of intense hurricanes that is commensurate with the previously observed active state that was seen prior to the mid 1960's. If true, then, the shift to the more active state, probably, occurred in the mid-to-late 1980's, apparently, having gone undetected because of the masking, or modulating, effect of El Ninio, which has been rampant since the mid-to-late 1980's.

Wilson, Robert M.↗
NASA NTRS1999

Satellite-Based Global Precipitation Data Sets at Monthly and Finer Time Scales

A new 20-year, monthly, globally complete precipitation analysis has been completed as part of the World Climate Research Program's (WCRP/GEWEX) Global Precipitation Climatology Project (GPCP). The global, monthly, 2.5 deg x 2.5 deg latitude-longitude product utilizes precipitation estimates from low-orbit microwave sensors (SSM/1) and geosynchronous IR sensors and raingauge information over land. The low-orbit microwave estimates are used to adjust or correct the geosynchronous IR estimates, thereby maximizing the utility of the more physically-based microwave estimates and the finer time sampling of the geosynchronous data. The 20-year climatology of the Version 2 GPCP analysis indicates the expected features of a very strong Pacific Ocean ITCZ and SPCZ with maximum 20-year means approaching 10 mm/day. A similar strength maximum over land is evident over Borneo. Weaker maxima in the tropics occur in the Atlantic ITCZ and over South America and Africa. In mid-latitudes of the Northern Hemisphere the Western Pacific and Western Atlantic maxima have values of approximately 7 mm/day, while in the Southern Hemisphere the mid-latitude maxima are located southeast of Africa, in mid-Pacific as an extension of the SPCZ and southeast of South America. In terms of global totals the GPCP analysis shows 2.7 mm/day (3.0 mm/day over ocean; 2.1 mm/day over land), similar to the Jaeger climatology, but not other climatologies. Zonal averages peak at 6 mm/day at 7 deg N with mid-latitude peaks of about 3 mm/day at 40-45 deg latitude. Poleward of 45 deg the GPCP analysis shows larger zonally-averaged values than most previous satellite-based estimates, although the values are similar to the Jaeger climatology.

Adler, Robert↗
NASA NTRS2000

What Controls the Temperature of the Arctic Stratosphere during the Spring?

Understanding the mechanisms that control the temperature of the polar lower stratosphere during spring is key to understanding ozone loss in the Arctic polar vortex. Spring ozone loss rates are directly tied to polar stratospheric temperatures by the formation of polar stratospheric clouds, and the conversion of chlorine species to reactive forms on these cloud particle surfaces. In this paper, we study those factors that control temperatures in the polar lower stratosphere. We use the National Centers for Environmental Prediction (NCEP)/NCAR reanalysis data covering the last two decades to investigate how planetary wave driving of the stratosphere is connected to polar temperatures. In particular, we show that planetary waves forced in the troposphere in mid- to late winter (January-February) are principally responsible for the mean polar temperature during the March period. These planetary waves are forced by both thermal and orographic processes in the troposphere, and propagate into the stratosphere in the mid and high latitudes. Strong mid-winter planetary wave forcing leads to a warmer Arctic lower stratosphere in early spring, while weak mid-winter forcing leads to cooler Arctic temperatures.

Newman, Paul A.↗
NASA NTRS2002

Interannual Variability of the Bimodal Distribution of Summertime Rainfall Over Central America and Tropical Storm Activity in the Far-Eastern Pacific

The summer climate of southern Mexico and Central America is characterized by a mid summer drought (MSD), where rainfall is reduced by 40% in July as compared to June and September. A mid-summer reduction in the climatological number of eastern Pacific tropical cyclones has also been noted. Little is understood about the climatology and interannual variability of these minima. The present study uses a novel approach to quantify the bimodal distribution of summertime rainfall for the globe and finds that this feature of the annual cycle is most extreme over Pan America and adjacent oceans. One dominant interannual signal in this region occurs the summer before a strong winter El Nino/Southern Oscillation ENSO. Before El Nino events the region is dry, the MSD is strong and centered over the ocean, and the mid-summer minimum in tropical cyclone frequency is most pronounced. This is significantly different from Neutral cases (non-El Nino and non-La Nina) when the MSD is weak and positioned over the land bridge. The MSD is highly variable for La Nina years, and there is not an obvious mid-summer minimum in the number of tropical cyclones.

Curtis, Scott↗
NASA NTRS2002

A Comparison of the Lower Stratospheric Age-Spectra Derived from a General Circulation Model and Two Data Assimilation Systems

We use kinematic and diabatic back trajectory calculations, driven by winds from a general circulation model (GCM) and two different data assimilation systems (DAS), to compute the age spectrum at three latitudes in the lower stratosphere. The age-spectra are compared to chemical transport model (CTM) calculations, and the mean ages from all of these studies are compared to observations. The age spectra computed using the GCM winds show a reasonably isolated tropics in good agreement with observations; however, the age spectra determined from the DAS differ from the GCM spectra. For the DAS diabatic trajectory calculations there is too much exchange between the tropics and mid-latitudes. The age spectrum is thus too broad and the tropical mean age is too old as a result of mixing older mid latitude air with tropical air. Likewise the mid latitude mean age is too young due to the in mixing of tropical air. The DAS kinematic trajectory calculations show excessive vertical dispersion of parcels in addition to excessive exchange between the tropics and mid latitudes. Because air is moved rapidly to the troposphere from the vertical dispersion, the age spectrum is shifted toward the young side. The excessive vertical and meridional dispersion compensate in the kinematic case giving a reasonable tropical mean age. The CTM calculation of the age spectrum using the DAS winds shows the same vertical and meridional dispersive characteristics of the kinematic trajectory calculation. These results suggest that the current DAS products will not give realistic trace gas distributions for long integrations; they also help explain why the extra tropical mean ages determined in a number of previous DAS driven CTM s are too young compared with observations. Finally, we note trajectory-generated age spectra . show significant age anomalies correlated with the seasonal cycles. These anomalies can be linked to year-to-year variations in the tropical heating rate. The anomalies are suppressed in the CTM spectra suggesting that the CTM transport scheme is too diffusive.

Schoeberl, Mark R.↗
NASA NTRS2003

Influence of Ice-phase of Hydrometeors on Moist-Convection

Climate models often ignore the influence of ice-phase physics (IPP) of hydrometeors as a second order effect. This has also been true for McRAS (Microphysics of clouds with Relaxed Arakawa Schubert Scheme) developed by the authors. Recognizing that the temperature sounding is critical for moist-convection, and, that IPP would modify it, we investigated the influence of introducing IPP into McRAS coupled to FvGCM (finite volume General Circulation Model with NCAR physics). We analyzed three 3-yr long simulations; the first called Control Case, CC and had no IPP; the other two called Experiments El and E2 had IPP introduced with two different in-cloud freezing assumptions. Simulation El assumed that all hydrometeors remain liquid in the updraft and freeze upon detrainment. Simulation E2 invoked the in-cloud freezing of new condensate generated at subfreezing temperatures in the updraft while old cloud water continued to ascend as liquid. Upon detrainment, this cloud water also froze like in E1. With these assumptions, about 50% of hydrometeors froze in the tower and the rest froze in the anvil. However, in both El and E2, the frozen hydrometeors melted during fall at the first encounter of above freezing ambient temperature. Comparative analysis revealed that El simulated far more mid-level and far less deep clouds while E2 had modified deep and more mid-level clouds as compared to CC along with some major changes around the melt-level. We infer that IPP produced a more realistic response in E2. At the basic level, the results show that ice-phase processes influence convective detrainment at mid- and deep levels in accord with TOGAGOARE observations. The results suggest that IPP can help to mitigate less-than-observed mid-level and over-abundance of deep convective clouds in McRAS.

Sud, Y. C.↗
NASA NTRS1999

Effects of CO2 on stomatal conductance: do stomata open at very high CO2 concentrations?

Potato and wheat plants were grown for 50 d at 400, 1000 and 10000 micromoles mol-1 carbon dioxide (CO2). and sweetpotato and soybean were grown at 1000 micromoles mol-1 CO2 in controlled environment chambers to study stomatal conductance and plant water use. Lighting was provided with fluorescent lamps as a 12 h photoperiod with 300 micromoles m-2 s-1 PAR. Mid-day stomatal conductances for potato were greatest at 400 and 10000 micromoles mol-1 and least at 1000 micromoles mol-1 CO2. Mid-day conductances for wheat were greatest at 400 micromoles mol-1 and least at 1000 and 10000 micromoles mol-1 CO2. Mid-dark period conductances for potato were significantly greater at 10000 micromoles mol-1 than at 400 or 1000 micromoles mol-1, whereas dark conductance for wheat was similar in all CO2 treatments. Temporarily changing the CO2 concentration from the native 1000 micromoles mol-1 to 400 micromoles mol-1 increased mid-day conductance for all species, while temporarily changing from 1000 to 10000 micromoles mol-1 also increased conductance for potato and sweetpotato. Temporarily changing the dark period CO2 from 1000 to 10000 micromoles mol-1 increased conductance for potato, soybean and sweetpotato. In all cases, the stomatal responses were reversible, i.e. conductances returned to original rates following temporary changes in CO2 concentration. Canopy water use for potato was greatest at 10000, intermediate at 400, and least at 1000 micromoles mol-1 CO2, whereas canopy water use for wheat was greatest at 400 and similar at 1000 and 10000 micromoles mol-1 CO2. Elevated CO2 treatments (i.e. 1000 and 10000 micromoles mol-1) resulted in increased plant biomass for both wheat and potato relative to 400 micromoles mol-1, and no injurious effects were apparent from the 10000 micromoles mol-1 treatment. Results indicate that super-elevated CO2 (i.e. 10000 micromoles mol-1) can increase stomatal conductance in some species, particularly during the dark period, resulting in increased water use and decreased water use efficiency.

NASA Discipline Life Support Systems↗
NASA NTRS2005

Entry, Descent, and Landing Technology Concept Trade Study for Increasing Payload Mass to the Surface of Mars

A trade study was conducted that compared various entry, descent, and landing technologies and concepts for placing an 1,800 kg payload on the surface of Mars. The purpose of this trade study was to provide data, and make recommendations, that could be used in making decisions regarding which new technologies and concepts should be pursued. Five concepts were investigated, each using a different combination of new technologies: 1) a Baseline concept using the least new technologies, 2) Aerocapture and Entry from Orbit, 3) Inflatable Aeroshell, 4) Mid L/D Aeroshell-A (high ballistic coefficient), and 5) Mid L/D Aeroshell-B (low ballistic coefficient). All concepts were optimized to minimize entry mass subject to a common set of key requirements. These key requirements were: A) landing a payload mass of 1,800 kg, B) landing at an altitude 2.5 km above the MOLA areoid, C) landing with a descent rate of 2.5 m/s, and D) using a single launch vehicle available within the NASA Expendable Launch Vehicle Contract without resorting to in-space assembly. Additional constraints were implemented, some common to all concepts and others specific to the new technologies used. Among the findings of this study are the following observations. Concepts using blunt-body aeroshells (1, 2, and 3 above) had entry masses between 4,028 kg and 4,123 kg. Concepts using mid L/D aeroshells (4 and 5 above) were significantly heavier with entry masses of 5,292 kg (concept 4) and 4,812 kg (concept 5). This increased weight was mainly due to the aeroshell. Based on a comparison of the concepts it was recommended that: 1) re-qualified and/or improved TPS materials be developed, 2) large subsonic parachutes be qualified. Aerocapture was identified as a promising concept, but system issues beyond the scope of this study need to be investigated. Inflatable aeroshells were identified as a promising new technology, but they require additional technology maturation work. For the class of missions investigated in this trade study, mid L/D aeroshells were not competitive on an entry mass basis as compared to blunt-body aeroshells.

Cruz, Juan R.↗
NASA NTRS2006

Civilian Aeronautical Futures - The Responsibly Imaginable

Since 1940 Aeronautics has had an immense impact upon Global Human lifestyles and affairs - in both the Civilian and Military arenas. During this period Long distance Train and Ship passenger transport were largely supplanted by Air Travel and Aviation assumed a dominant role in warfare. The early 1940 s to the mid 1970 s was a particularly productive period in terms of Aeronautical Technology. What is interesting is that, since the mid 1970 s, the rate of Aeronautical Technological Progress has been far slower, the basic technology in nearly all of our current Aero Systems dates from the mid 70 s or earlier. This is especially true in terms of Configuration Aerodynamics, Aeronautics appears to have "settled" on the 707, double delta and rotary wing as the approach of choice for Subsonic long haul, supersonic cruise and VTOL respectively. Obviously there have been variants and some niche digression from this/these but in the main Aeronautics, particularly civilian Aeronautics, has become a self-professed "mature", Increasingly "Commodity", Industry. The Industry is far along an existing/deployed technology curve and focused, now for decades, on incremental/evolutionary change - largely Appliers vs. developers of technology. This is, of course, in sharp contrast to the situation in the early-to-later 20th century where Aeronautics was viewed as A Major Technological Engine, much the way IT/Bio/Nano/Energetics/Quantum Technologies are viewed today. A search for Visionary Aeronautical "Futures" papers/projections indicates a decided dearth thereof over the last 20 plus years compared to the previous quarter Century. Aeronautics is part of Aerospace and Aerospace [including Aeronautics] has seen major cutbacks over the last decades. Some numbers for the U.S. Aerospace Industry serve as examples. Order of 600,000 jobs lost, with some 180,000 more on the block over the next 10 years. Approximately 25% of the Aerospace workforce is eligible to retire and the average Engineer age is in the mid-50 s. Firms such as Microsoft, Intel and Walmart are individually capitalized at a factor of 4 or more than the Aerospace industry as a whole. Aerospace Research levels are in the less than 5% range in terms of overall U.S. Research Investments.

Bushnell, Dennis M.↗
NASA NTRS2007

Highly Structured Plasma Density and Associated Electric and Magnetic Field Irregularities at Sub-Auroral, Middle, and Low Latitudes in the Topside Ionosphere Observed with the DEMETER and DMSP Satellites

Detailed observations of the plasma structure and irregularities that characterize the topside ionosphere at sub-auroral, middle, and low-latitudes are gathered with probes on the DEMETER and DMSP satellites. In particular, we present DEMETER observations near 700 km altitude that reveal: (1) the electric field irregularities and density depletions at mid-latitudes are remarkably similar to those associated with equatorial spread-F at low latitudes; (2) the mid-latitude density structures contain both depletions and enhancements with scale lengths along the spacecraft trajectory that typically vary from 10's to 100's of km; (3) in some cases, ELF magnetic field irregularities are observed in association with the electric field irregularities on the walls of the plasma density structures and appear to be related to finely-structured spatial currents and/or Alfven waves; (4) during severe geomagnetic storms, broad regions of nightside plasma density structures are typically present, in some instances extending from the equator to the subauroral regions; and (5) intense, broadband electric and magnetic field irregularities are observed at sub-auroral latitudes during geomagnetic storm periods that are typically associated with the trough region. Data from successive DEMETER orbits during storm periods in both the daytime and nighttime illustrate how enhancements of both the ambient plasma density, as well as sub-auroral and mid-latitude density structures, correlate and evolve with changes in the Dst. The DEMETER data are compared with near simultaneous observations gathered by the DMSP satellites near 840 km. The observations are related to theories of sub-auroral and mid-latitude plasma density structuring during geomagnetic storms and penetration electric fields and are highly germane to understanding space weather effects regarding disruption of communication and navigation signals in the near-space environment.

Pfaff, Robert F.↗
NASA NTRS2006

Long-term Evolution of Upper Stratospheric Ozone at Selected Stations of the Network for the Detection of Stratospheric Change (NDSC)

The long-term evolution of upper stratospheric ozone has been recorded by lidars and microwave radiometers within the ground-based Network for the Detection of Stratospheric Change (NDSC), and by the space-borne Solar Backscatter Ultra-Violet instruments (SBUV), Stratospheric Aerosol and Gas Experiment (SAGE), and Halogen Occultation Experiment (HALOE). Climatological mean differences between these instruments are typically smaller than 5% between 25 and 50 km. Ozone anomaly time series from all instruments, averaged from 35 to 45 km altitude, track each other very well and typically agree within 3 to 5%. SBUV seems to have a slight positive drift against the other instruments. The corresponding 1979 to 1999 period from a transient simulation by the fully coupled MAECHAM4-CHEM chemistry climate model reproduces many features of the observed anomalies. However, in the upper stratosphere the model shows too low ozone values and too negative ozone trends, probably due to an underestimation of methane and a consequent overestimation of ClO. The combination of all observational data sets provides a very consistent picture, with a long-term stability of 2% or better. Upper stratospheric ozone shows three main features: (1) a decline by 10 to 15% since 1980, due to chemical destruction by chlorine; (2) two to three year fluctuations by 5 to 10%, due to the Quasi-Biennial Oscillation (QBO); (3) an 11-year oscillation by about 5%, due to the 11-year solar cycle. The 1979 to 1997 ozone trends are larger at the southern mid-latitude station Lauder (45 S), reaching 8%/decade, compared to only about 6%/decade at Table Mountain (35 N), Haute Provence/Bordeaux (approximately equal to 45 N), and Hohenpeissenberg/Bern(approximately equal to 47 N). At Lauder, Hawaii (20 N), Table Mountain, and Haute Provence, ozone residuals after subtraction of QBO- and solar cycle effects have levelled off in recent years, or are even increasing. Assuming a turning point in January 1997, the change of trend is largest at southern mid-latitude Lauder, +11%/decade, compared to +7%/decade at northern mid-latitudes. This points to a beginning recovery of upper stratospheric ozone. However, chlorine levels are still very high and ozone will remain vulnerable. At this point the most northerly mid-latitude station, Hohenpeissenberg/Bern differs from the other stations, and shows much less clear evidence for a beginning recovery, with a change of trend in 1997 by only +3%/decade. In fact, record low upper stratospheric ozone values were observed at Hohenpeissenberg/Bern, and to a lesser degree at Table Mountain and Haute Provence, in the winters 2003/2004 and 2004/2005.

Steinbrecht, W.↗
NASA NTRS2009

Astronaut Thermal Exposure: Re-Entry After Low Earth Orbit Rescue Mission

The STS-125 mission, launched May 11, 2009, is the final servicing mission to the Hubble Space Telescope. The repair mission's EVA tasks are described, including: installing a new wide field camera; installing the Cosmic Origins Spectrograph; repairing the Space Telescope Imaging Spectrograph; installing a new outer blanket layer; adding a Soft Capture and Rendezvous System for eventual controlled deorbit in about 2014; replacing the 'A' side Science Instrument Command and Data Handling module; repairing the Advanced Camera for surveys; and, replacing the rate sensor unit gyroscopes, fine guidance sensors and 3 batteries. Additionally, the Shuttle crew cabin thermal environment is described. A CFD model of per person CO2 demonstrates a discrepancy between crew breathing volume and general mid-deck levels of CO2. A follow-on CFD analysis of the mid-deck temperature distribution is provided. Procedural and engineering mitigation plans are presented to counteract thermal exposure upon reentry to the Earth atmosphere. Some of the procedures include: full cold soak the night prior to deorbit; modifying deck stowage to reduce interference with air flow; and early securing of avionics post-landing to reduce cabin thermal load prior to hatch opening. Engineering mitigation activities include modifying the location of the aft starboard ICUs, eliminating the X3 stack and eliminating ICU exhaust air directed onto astronauts; improved engineering data of ICU performance; and, verifying the adequacy of mid-deck temperature control using CFD models in addition to lumped parameter models. Post-mitigation CFD models of mid-deck temperature profiles and distribution are provided.

Gillis, David B.↗
NASA NTRS2013

Declining Nutrient Concentrations in the Northeast Atlantic as a Result of a Weakening Subpolar Gyre

Between 1996 and the mid-2000s the upper waters (200-700 m) of the Rockall Trough became warmer (+0.72 C), saltier (+0.088) and reduced in nitrate and phosphate (-2.00 Micron and -0.14 Micron respectively). These changes, out-with calculated errors, can be explained by the varying influence of southern versus subpolar water masses in the basin as the Subpolar Gyre weakened and contracted. Upper water properties strongly correlate with a measure of the strength of the Subpolar Gyre (the first principal component of sea surface height over the Subpolar North Atlantic) prior to the mid-2000s. As the gyre weakens, the upper layers of the trough become warmer (r -0.85), more saline (r -0.86) and reduced in nitrate and phosphate (r +0.81 and r +0.87 respectively). Further the proportion of subpolar waters in the basin decreases from around 50% to less than 20% (r +0. 88). Since the mid-2000s the Subpolar Gyre has been particularly weak. During this period temperatures decreased slightly (-0.21 1C), salinities remained near constant (35.410 +/- 0.005) and phosphate levels low and stable (0.68 +/- 0.02 Micron). These relative lack of changes are thought to be related to the maximum proportion of southern water masses within the Rockall Trough having been reached. Thus the upper water properties are no longer controlled by changes in the relative importance of different water masses in the basin (as prior to the mid-2000s), but rather a different process. We suggest that when the gyre is particularly weak the interannual changes in upper water properties in the Rockall Trough reflect changes in the source properties of the southern water masses. Since the early-2000s the Subpolar Gyre has been weaker than observed since 1992, or modelled since 1960-1970. Hence upper waters within the Rockall Trough may be warmer, saltier and more depleted in nitrate and phosphate than at any time in the last half century.

nutrient↗