NASA Scientific and Technical Aerospace Reports

(FL-1016) (Salottolo 1994; Phillips 1994). The inbound DC-9 unexpectedly encountered a rapidly intensifying rainshaft just
seconds before it was to touchdown on runway 18R. The aircraft crashed after encountering strong windshear, killing 37 of
the 57 souls on board. The pilots did not recognize the windshear condition in time to prevent the accident and received no
warning from the aircraft’s Honeywell in-situ windshear detection system or from ground-based systems (Charlotte maintains
both an ASR-9 weather radar and a Phase-2 LLWAS). Also two other aircraft landed ahead of FL-1016 without incident and
reported smooth approaches to 18R. Section-2 of this paper reports briefly on the reconstruction of the event based on
numerical results generated by the Terminal Area Simulation System (TASS) as presented at the National Transportation
Safety Board (NTSB) public hearing (Proctor 1994). Section-3 discusses the simulation of this event with a look-ahead
windshear radar.
Derived from text
Microbursts (Meteorology); Wind Shear; Radar; Computerized Simulation; Weather; Airborne Radar; North Carolina
20040111283 California Univ., Berkeley, CA, USA
Modeling of Isotope Fractionation in Stratospheric CO2, N2O, CH4, and O3: Investigations of Stratospheric
Chemistry and Transport, Stratosphere-Troposphere Exchange, and Their Influence on Global Isotope Budgets
Boering, Kristie A.; Connell, Peter; Rotman, Douglas; [2004]; 4 pp.; In English
Contract(s)/Grant(s): NAG1-2191; NAG1-02083; No Copyright; Avail: CASI; A01, Hardcopy
We investigated the isotopic fractionation of CH4 and hydrogen (H2) in the stratosphere by incorporating isotope-specific
rate coefficients into the Lawrence Livermore National Laboratory (LLNL) 2D model and comparing the model results with
new observations from the NASA ER-2 aircraft (funded through a separate task under the Upper Atmosphere Research
Program). The model results reveal that fractionation which occurs in the stratosphere has a significant influence on isotope
compositions in the free troposphere, an important point which had previously been ignored, unrecognized or unquantified for
many long-lived trace gases, including CH4 and H2 which we have focused our efforts on to date. Our analyses of the model
results and new isotope observations have also been used to test how well the kinetic isotope effects are known, at least to
within the uncertainties in model chemistry and transport. Overall, these results represent an important step forward in our
understanding of isotope fractionation in the atmosphere and demonstrate that stratospheric isotope fractionation cannot be
ignored in modeling studies which use isotope observations in the troposphere to infer the global budgets of CH4 (an important
greenhouse gas) and of H2 (a gas whose atmospheric budget must be better quantified, particularly before a large human
perturbation from fuel cell use is realized). Our analyses of model results and observations from the NASA ER-2 aircraft are
briefly summarized separately below for CH4, H2, and H2O and for the contribution of these modeling studies to date to our
understanding of isotope fractionation for N2O, CO2, and O3 as well.
Derived from text
Stratosphere; Atmospheric Composition; Trace Elements; Hydrogen; Methane; Water Vapor
20040111392 Harvard Univ., Cambridge, MA, USA
Global Modeling of Tropospheric Chemistry with Assimilated Meteorology: Model Description and Evaluation
Bey, Isabelle; Jacob, Daniel J.; Yantosca, Robert M.; Logan, Jennifer A.; Field, Brendan D.; Fiore, Arlene M.; Li, Qin-Bin;
Liu, Hong-Yu; Mickley, Loretta J.; Schultz, Martin G.; October 16, 2001; ISSN 0148-0227; 23 pp.; In English
Contract(s)/Grant(s): NAG1-2307
Report No.(s): Paper 2001JD000807; Copyright; Avail: Other Sources
We present a first description and evaluation of GEOS-CHEM, a global three-dimensional (3-D) model of tropospheric
chemistry driven by assimilated meteorological observations from the Goddard Earth Observing System (GEOS) of the NASA
Data Assimilation Office (DAO). The model is applied to a 1-year simulation of tropospheric ozone-NOx-hydrocarbon
chemistry for 1994, and is evaluated with observations both for 1994 and for other years. It reproduces usually to within 10
ppb the concentrations of ozone observed from the worldwide ozonesonde data network. It simulates correctly the seasonal
phases and amplitudes of ozone concentrations for different regions and altitudes, but tends to underestimate the seasonal
amplitude at northern midlatitudes. Observed concentrations of NO and peroxyacetylnitrate (PAN) observed in aircraft
campaigns are generally reproduced to within a factor of 2 and often much better. Concentrations of HNO3 in the remote
troposphere are overestimated typically by a factor of 2-3, a common problem in global models that may reflect a combination
of insufficient precipitation scavenging and gas-aerosol partitioning not resolved by the model. The model yields an
atmospheric lifetime of methylchloroform (proxy for global OH) of 5.1 years, as compared to a best estimate from
observations of 5.5 plus or minus 0.8 years, and simulates H2O2 concentrations observed from aircraft with significant
regional disagreements but no global bias. The OH concentrations are approximately 20% higher than in our previous global
3-D model which included an UV-absorbing aerosol. Concentrations of CO tend to be underestimated by the model, often by
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