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Max Loewenstein, H. F. Savage, and R. C. Whitten

Abstract

Nitric oxide and ozone concentrations have been measured in situ from a high-altitude research aircraft based at the NASA Ames Research Center. Data which show the variations of NO and 03 with the time of year are presented for altitudes of 18.3 and 21.3 km. The extreme values of the observed NO concentrations at 21.3 km are 1.2×109 cm−3 in summer and 2×108 cm−3 in winter. At 18.3 km the extreme values are 1.6×109 cm−3 in summer and 1×108 cm−3 in winter. The smoothed NO seasonal data show a variation of about a factor of 2.5 at 21.3 km and a factor of 4 at 18.3 km. The ozone data show the generally expected magnitude and seasonal variation.

We have used a photochemical model employing the measured ozone concentrations, the mean solar zenith angle, and seasonal HNO3 data reported by others to predict the seasonal NO variation at 20 km. The result is a summer-to-winter NO ratio of 2.5 which is in fair agreement with the observed ratios.

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Leonhard Pfister, Walter Starr, Roger Craig, Max Loewenstein, and Marion Legg

Abstract

Measurments of temperature and ozone from instrumental aircraft in the tropical lower stratosphere show the presence of small-scale disturbances generated by 1) underlying cumulus convection and 2) Kelvin-Helmholtz instability. The disturbances associated with underlying convection have peak-to-peak vertical parcel excursions of ∼300 m. Flying conditions were smooth, suggesting an ensemble of gravity waves and little or no turbulent mixing. It is nevertheless possible that these waves break at other altitudes, leading to turbulent mixing and net fluxes of vertically stratified tracers.

Disturbances attributed to KH instability implied vertical parcel excursions of 300–400 m. The disturbances coincided with rough flying conditions, suggesting turbulent mixing. A linear stability analysis of the atmospheric basic state defined by high-resolution radiosondes shows fastest growing waves with horizontal wavelengths of 1.4–1.8 km, consistent with the aircraft observations. The strong shears responsible for the KH instability are due to large-scale waves propagating into a region of small intrinsic frequency. Radiosonde observations show that the zonal length scale of them waves is ∼1000 km.

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Leonhard Pfister, Stanley Scott, Max Loewenstein, Stuart Bowen, and Marion Legg

Abstract

The importance of the momentum flux of topographically generated mesoscale gravity waves to the extratropical middle atmosphere circulation has been well established for over a decade. Estimates of the zonal forcing due to tropical mesoscale gravity waves, however, are hampered by lack of data on their primarily convective sources. The advent of aircraft measurements over tropical convective systems now makes such estimates possible without the use of ad hoc assumptions about amplitudes and phase speeds.

Aircraft measurements from NASA's 1980 Panama and 1987 STEP/Australia Missions show that convectively generated disturbances observed just above the tropopause have horizontal scales comparable to those of the underlying anvils (about 50–100 km) with peak-to-peak isentropic surface variations of about 300–400 m. Satellite imagery of tropical anvil evolution indicates a typical lifetime of about five hours. Assuming that each convective system's impact on the stratosphere can be modeled as a time-dependent “mountain” with the preceding spatial and time scales, the excited spectrum of gravity waves can be calculated. A suitable quasilinear wave-mean flow interaction parameterization and satellite-derived cloud area statistics can then be used to evaluate the zonal acceleration as a function of altitude induced by gravity waves from mesoscale convective systems.

The results indicate maximum westerly accelerations due to breaking mesoscale gravity waves of almost 0.4 m s−1/day in the upper stratosphere (in the region of the semiannual oscillation) during September, comparable to but probably smaller than the accelerations induced by planetary-scale Kelvin waves. Calculated easterly accelerations due to breaking mesoscale gravity waves in the QBO region below 35 km are smaller, accounting for about 10% of the required zonal acceleration.

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Patrick Hamill, Laura T. Iraci, Emma L. Yates, Warren Gore, T. Paul Bui, Tomoaki Tanaka, and Max Loewenstein

Abstract

The NASA Ames Research Center operates a new research platform for atmospheric studies: an instrumented Alpha Jet. The present complement of instruments allows for the determination of carbon dioxide, ozone, water vapor, and methane concentrations as well as measurements of three-dimensional wind speeds, temperature, and pressure. Planned future instrumentation includes an Air-Core sampler and an instrument to measure formaldehyde. We give examples of measurements that have been made, including measurements carried out during a downward spiral over an expected methane source. An attractive property of this airborne system is its ability to respond rapidly to unexpected atmospheric events such as large forest fires or severe air quality events.

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Cynthia Rosenzweig, Radley M. Horton, Daniel A. Bader, Molly E. Brown, Russell DeYoung, Olga Dominguez, Merrilee Fellows, Lawrence Friedl, William Graham, Carlton Hall, Sam Higuchi, Laura Iraci, Gary Jedlovec, Jack Kaye, Max Loewenstein, Thomas Mace, Cristina Milesi, William Patzert, Paul W. Stackhouse Jr., and Kim Toufectis

A partnership between Earth scientists and institutional stewards is helping the National Aeronautics and Space Administration (NASA) prepare for a changing climate and growing climate-related vulnerabilities. An important part of this partnership is an agency-wide Climate Adaptation Science Investigator (CASI) Workgroup. CASI has thus far initiated 1) local workshops to introduce and improve planning for climate risks, 2) analysis of climate data and projections for each NASA Center, 3) climate impact and adaptation toolsets, and 4) Center-specific research and engagement.

Partnering scientists with managers aligns climate expertise with operations, leveraging research capabilities to improve decision-making and to tailor risk assessment at the local level. NASA has begun to institutionalize this ongoing process for climate risk management across the entire agency, and specific adaptation strategies are already being implemented.

A case study from Kennedy Space Center illustrates the CASI and workshop process, highlighting the need to protect launch infrastructure of strategic importance to the United States, as well as critical natural habitat. Unique research capabilities and a culture of risk management at NASA may offer a pathway for other organizations facing climate risks, promoting their resilience as part of community, regional, and national strategies.

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