| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | June 26, 2013 |
| Latest Amendment Date: | June 26, 2013 |
| Award Number: | 1301762 |
| Award Instrument: | Standard Grant |
| Program Manager: |
John Meriwether
AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | July 1, 2013 |
| End Date: | June 30, 2017 (Estimated) |
| Total Intended Award Amount: | $100,904.00 |
| Total Awarded Amount to Date: | $100,904.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
620 MICHIGAN AVE NE WASHINGTON DC US 20064-0001 (202)635-5000 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
Washington DC US 20064-0001 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | AERONOMY |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
The investigators will study various Infrared (IR) emission mechanisms in the Mesosphere and Lower Thermosphere (MLT), which may be responsible for a largely unexplained enhanced IR feature at ~90 km. The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER), one of four instruments on board of NASA's Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) mission, is a 10-channel broadband limb-scanning infrared radiometer covering the spectral range from 1.27 to 17 microns. SABER has already provided a decade worth of information about kinetic temperature, pressure, ozone, carbon dioxide, water vapor and atomic oxygen. The interpretation of these results, which are strongly affected by the quality of models of the IR emissions in the MLT, have crucial importance for understanding the physics and chemistry of this region. An IR limb emission feature that resembles a layer-like enhancement has been present since the beginnings of the satellite operations in SABER's 4.3 micron channel. This feature is localized at an altitude region that corresponds to tangent heights between 85-95 km and has a distinct spatial and temporal variability. Although the enhanced limb radiances are present at all latitudes and seasons, they appear to be stronger at the polar summer MLT. Preliminary analysis of observations from other spacecraft reveal similar features although those instruments operate significantly different, which indicate this is, at least in part, a real phenomena. This enhancement is not predicted by our current IR emission models in the MLT, in particular when compared to similar effects observed in additional channels. Due to a lack of understanding of its origins, this effect has been ignored for a decade and, as a result, is generally unknown by the aeronomy and space science communities. The investigators will study a number of radically different as well as interdisciplinary approaches, among them non-equilibrium chemistry of molecular, atomic and ionic compounds of MLT and their possible interactions with dust and ice particles, various potential mechanism of energy transfer from photolysis and chemical reaction products to molecular vibrations, non-LTE molecular emission, absorption, transformation and multiple scattering of radiation in various spectral regions, etc The investigation will address a feature that may alter the understanding of the CO2 characteristics in the MLT. As such, the results may have high impact on atmospheric chemistry and climate. Additionally, this study will provide a more robust analysis of IR radiances that can be later expanded to other space missions.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Since 2002, the SABER instrument on board the TIMED satellite has been continuously measuring the day- and night-time infrared limb
radiances of the atmosphere in ten broadband channels. Recently, revised daytime temperature/pressure and CO2 densities have been
obtained self-consistently from the SABER 15 μm and 4.3 μm emission observations. However, similar nighttime
data remain unprocessed due to a lack of understanding of the 4.3 μm emission generating mechanisms:
the models under-predicted the observed radiance by up to 80%. Recently
a new nighttime channel OH(ν)⇒O(1D)⇒N2(ν)⇒CO2(ν3)⇒4.3 μm of this emission generation was suggested. Using this new mechanisms
we developed the revised model of the CO2 and OH emissions of the MLT and performed detailed comparison of calculations with (a)
the SABER/TIMED nighttime 4.3 μm CO2 and OH 1.6 and 2.0 μm limb radiances of the MLT and (b) with ground and
space observations of OH(ν) densities in the nighttime mesosphere. We found that
for various latitudinal and seasonal scenarios new energy transfer channel brings
differences between simulated and measured nighttime SABER 4.3 μm limb radiances in the range of (-15, +15)%, making nighttime CO2
density retrieval now possible. The results of our study suggest that the important mechanism, which dominates the nighttime pumping of
CO2(ν3 ) and 4.3 μm CO2 emissions,
has finally been identified after nearly 30 years of efforts of various research groups.
The new model produces also OH(ν) density
distributions which are in good agreement with both SABER limb OH emission observations and ground and space
measurements. The latter allows retrieving from the OH emission measured by SABER both OH and atomic oxygen densities
in mesosphere-lower thermosphere.
The studies performed provided real "new look" at middle atmosphere infra-red emission formation and demonstrate
significant progress in understanding the mechanisms of the CO2 and OH emission generation in mesosphere-lower thermosphere.
Last Modified: 08/28/2017
Modified by: Alexander Kutepov
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