| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | December 3, 2008 |
| Latest Amendment Date: | January 7, 2014 |
| Award Number: | 0836518 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Sunanda Basu
AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | January 1, 2009 |
| End Date: | December 31, 2014 (Estimated) |
| Total Intended Award Amount: | $262,500.00 |
| Total Awarded Amount to Date: | $262,500.00 |
| Funds Obligated to Date: |
FY 2010 = $90,500.00 FY 2011 = $92,000.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
3100 MARINE ST Boulder CO US 80309-0001 (303)492-6221 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
3100 MARINE ST Boulder CO US 80309-0001 |
| 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: |
01001011DB NSF RESEARCH & RELATED ACTIVIT 01001112DB NSF RESEARCH & RELATED ACTIVIT |
| 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
This project focuses on trying to identify the sources of the short-term day-to-day variability in the migrating diurnal tides, with a specific focus on nonlinear wave-wave interactions between the migrating diurnal tide and both the westward propagating Rossby-gravity two-day wave and with ultra fast Kelvin waves. The migrating diurnal tide is a dominant and persistent feature of the mesosphere and lower thermosphere. It is forced in the troposphere through the absorption of solar radiation by water vapor and propagates vertically into the upper atmosphere. As the tide propagates vertically its structure is modified through interactions with the intervening mean wind field, planetary waves and dissipation. While observations clearly show significant day-to-day variations in the migrating diurnal tide, little modeling work has been conducted to date to understand the source and impact of these variations. The current hypothesis, to be tested in this project, is that the mechanism involves the nonlinear wave-wave interactions between the migrating diurnal tide and the global scale Rossby-gravity two day wave and the ultra fast Kelvin waves. This hypothesis will be investigated using the National Center for Atmospheric Research Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM). The TIME-GCM is a fully nonlinear three-dimensional global circulation model with a domain spanning from 35 to 500 km. By conducting controlled numerical studies and modifying the lower-boundary of the model to include the two-day wave and ultra fast Kelvin wave the potential for nonlinear interaction between the tide and these waves will be explored. This research will result in an improved understanding of the potential for nonlinear wave-wave interactions in the atmosphere and the impact of these interactions on both the migrating diurnal tide and global scale waves, such as the westward propagating Rossby-gravity two-day wave and eastward propagating ultra fast Kelvin waves. Additionally, because the migrating diurnal tide can affect the lower-boundary of the thermosphere and day-to-day variations will impact the weather of the thermosphere/ionosphere system, results from this research will be of interest for space weather.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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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.
Project Outcomes:
The migrating diurnal tide is a persistent feature of the atmosphere similar to the lunar ocean tides, however the migrating tide is excited by the absorption of solar radiation by water vapor in the lowest 10km of the atmosphere rather than the gravitational forcing of the moon. The migrating diurnal tide is constantly forced and propagates away from the lower atmosphere into the upper atmosphere. As the wave propagates vertically, the amplitude increases dramatically due to the decrease in atmosphere density. In the lower thermosphere, around 100km altitude, this wave can become unstable depositing heat and momentum thus impacting the overall global atmospheric flow in the thermosphere.
Observations have indicated that this migrating diurnal tide is highly variable, changing in amplitude by 100% from one day to the next. Additionally observations have shown periodic variations in tidal amplitude that reflect the periods of other waves such as the westward propagating Rossby-gravity quasi-two day planetary wave and the eastward propagating ultra-fast Kelvin planetary waves. These planetary waves are theorized to interact with the migrating diurnal tide creating a pathway for wave propagation deep into the upper atmosphere. These waves can impact the structure of the ionosphere and as a result disrupt high frequency communications and global positioning satellite systems.
Intellectual Merits:
This project has resulted in 10 scientific presentations and 5 peer reviewed publications addressing the key topic of short-term variability of the migrating diurnal tide and interaction with global planetary waves. The topics of the peer reviewed research publications are
- Comparison of diurnal tide in models and ground-based observations during the 2005 equinox CAWSES tidal campaign
- Propagating planetary wave coupling in SABER MLT temperatures and GPS TEC during the 2005/2006 austral summer
- Short?term variability in the migrating diurnal tide caused by interactions with the quasi 2 day wave
- A technique for estimating the short term variability of the diurnal tide utilizing multiple satellites
- Transmission of planetary wave effects to the upper atmosphere through eddy diffusion modulation
As a result of this NSF support we were able to make more contributions to understanding the short-term variability of the migrating diurnal tide. This was largely the results of having highly motivated students working on the project.
Broader Impacts:
This project has provided support for three aerospace engineering graduate students. Two were PhD students, one who has graduated and one who will graduate in the next 18 months. Both of these graduate students have gained valuable experience conducting independent research, presenting research at conferences and technical writing for publication. Both students have also learned how to run and modify the National Center for Atmospheric Research (NCAR) general circulation models such as the TIME-GCM and WACCM. The third student was a master’s student who's worked focused on the analysis of observational data in support of this project. He learned critical data analysis and software skills.
Last Modified: 06/18/2015
Modified by: Scott E Palo
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