Langley Research Center

About: Langley Research Center is a facility organization based out in Hampton, Virginia, United States. It is known for research contribution in the topics: Mach number & Wind tunnel. The organization has 15945 authors who have published 37602 publications receiving 821623 citations. The organization is also known as: NASA Langley & NASA Langley Research Center.

Where did tropospheric ozone over southern Africa and the tropical Atlantic come from in October 1992? Insights from TOMS, GTE TRACE A, and SAFARI 1992

Abstract: The seasonal tropospheric ozone maximum in the tropical South Atlantic, first recognized from satellite observations (Fishman et al., 1986, 1991), gave rise to the IGAC/ STARE/SAFARI 1992/TRACE A campaigns (International Global Atmospheric Chemistry/South Tropical Atlantic Regional Experiment/Southern African Fire Atmospheric Research Initiative/Transport and Atmospheric Chemistry Near the Equator- Atlantic) in September and October 1992. Along with a new TOMS-based method for deriving tropospheric column ozone, we used the TRACE A/SAFARI 1992 data set to put together a regional picture of the 0 3 distribution during this period. Sondes and aircraft profiling showed a troposphere with layers of high O3 (->90 ppbv) all the way to the tropopause. These features extend in a band from 0 o to 25oS, over the SE Indian Ocean, Africa, the Atlantic, and eastern South America. A combination of trajectory and photochemical modeling (the Goddard (GSFC) isentropic trajectory and tropospheric point model, respectively) shows a strong connection between regions of high ozone and concentrated biomass burning, the latter identified using satellite-derived fire counts (Justice et al., this issue). Back trajectories from a high-O3 tropical Atlantic region (column ozone at Ascension averaged 50 Dobson units (DU)) and forward trajectories from fire- rich and convectively active areas show that the Atlantic and southern Africa are supplied with O3 and O3-forming trace gases by midlevel easterlies and/or recirculating air from Africa, with lesser contributions from South American burning and urban pollution. Limited sampling in the mixed layer over Namibia shows possible biogenic sources of NO. High-level westerlies from Brazil (following deep convective transport of ozone precursors to the upper troposphere) dominate the upper tropospheric 03 budget over Natal, Ascension, and Okaukuejo (Namibia), although most enhanced O3 (75% or more) equatorward of 10oS was from Africa. Deep convection may be responsible for the timing of the seasonal tropospheric 0 3 maximum: Natal and Ascension show a 1- to 2-month lag relative to the period of maximum burning (cf. Baldy et al., this issue; Olson et al., this issue). Photochemical model calculations constrained with TRACE A and SAFARI airborne observations of O3 and 03 precursors (NOx, CO, hydrocarbons) show robust ozone formation (up to 15 ppbv O3/d or several DU/d) in a widespread, persistent, and well-mixed layer to 4 km. Slower but still positive net 03 formation took place throughout the tropical upper troposphere (cf. Pickering et al., this issue (a); Jacob et al., this issue). Thus whether it is faster rates of 0 3 formation in source regions with higher turnover rates or slower 03 production in long-lived stable layers ubiquitous in the TRACE A region, 10-30 DU tropospheric 03 above a -25-DU background can be accounted for. In summary, the 03 maximum studied in October 1992 was caused by a coincidence of abundant 03 precursors from biomass fires, a long residence time of stable air parcels over the eastern Atlantic and southern Africa, and deep convective transport of biomass burning products, with additional NO from lightning and occasionally biogenic sources.

Evidence for slowdown in stratospheric ozone loss: First stage of ozone recovery

Abstract: Global ozone trends derived from the Stratospheric Aerosol and Gas Experiment I and II (SAGE I/II) combined with the more recent Halogen Occultation Experiment (HALOE) observations provide evidence of a slowdown in stratospheric ozone losses since 1997. This evidence is quantified by the cumulative sum of residual differences from the predicted linear trend. The cumulative residuals indicate that the rate of ozone loss at 35- 45 km altitudes globally has diminished. These changes in loss rates are consistent with the slowdown of total stratospheric chlorine increases characterized by HALOE HCI measurements. These changes in the ozone loss rates in the upper stratosphere are significant and constitute the first stage of a recovery of the ozone layer.

Climate-chemical interactions and effects of changing atmospheric trace gases

Abstract: The paper considers trace gas-climate effects including the greenhouse effect of polyatomic trace gases, the nature of the radiative-chemical interactions, and radiative-dynamical interactions in the stratosphere, and the role of these effects in governing stratospheric climate change. Special consideration is given to recent developments in the investigations of the role of oceans in governing the transient climate responses, and a time-dependent estimate of the potential trace gas warming from the preindustrial era to the early 21st century. The importance of interacting modeling and observational efforts is emphasized. One of the problems remaining on the observational front is the lack of certainty in current estimates of the rate of growth of CO, O3, and NOx; the primary challenge is the design of a strategy that will minimize the sampling errors.

Possible influences of Asian dust aerosols on cloud properties and radiative forcing observed from MODIS and CERES

Abstract: [1] The effects of dust storms on cloud properties and Radiative Forcing (RF) are analyzed over Northwestern China from April 2001 to June 2004 using data collected by the MODerate Resolution Imaging Spectroradiometer (MODIS) and Clouds and the Earth's Radiant Energy System (CERES) instruments on the Aqua and Terra satellites. On average, ice cloud effective particle diameter, optical depth and ice water path of cirrus clouds under dust polluted conditions are 11%, 32.8%, and 42% less, respectively, than those derived from ice clouds in dust-free atmospheric environments. Due to changes in cloud microphysics, the instantaneous net RF is increased from −161.6 W/m2 for dust-free clouds to −118.6 W/m2 for dust-contaminated clouds.