| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | August 4, 2021 |
| Latest Amendment Date: | August 4, 2021 |
| Award Number: | 2129223 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Yu Gu
ygu@nsf.gov (703)292-8796 AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | October 1, 2021 |
| End Date: | September 30, 2024 (Estimated) |
| Total Intended Award Amount: | $72,321.00 |
| Total Awarded Amount to Date: | $72,321.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
615 W 131ST ST NEW YORK NY US 10027-7922 (212)854-6851 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
2880 Broadway, Armstrong Hall (NASA/GISS), sixth floor, room 650 NEW YORK NY US 10025-7886 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| NSF Program(s): | Physical & Dynamic Meteorology |
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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 research seeks to answer a number of questions that have arisen from recent observations of unstable layers at various altitudes in the atmosphere; that is, these layers are characterized with air temperature decreasing with height. Unstable layers have been identified by examining a fast meteorological sensor attached to meteorological balloons launched from stations operated by the United States (US) Weather Service. The fast meteorological sensor can take air temperature at every second, which is at every 5 meters as a balloon rises. Unstable layers are commonly associated with turbulence. Within each turbulent layer, air motions cascade from large eddies to small ones due to kinetic energy dissipation. Atmospheric turbulence is dangerous for aircraft operations and has impacts on remote sensing atmospheric phenomena. The researchers for the project will investigate what causes these unstable layers. Understanding of the origin of these unstable layers could improve safety of aircraft operations. Recently global observations using this type of fast meteorological balloon sensors become available. The investigators also plan to organize an international workshop to stimulate international research for using this dataset.
The research team will answer two principal questions: 1) Why are there more unstable layers in the lower stratosphere at midnight Greenwich Mean Time (GMT) in the western contiguous US than at noon GMT, with the opposite being true in the eastern US? 2) Is the observed phenomenon of a great number of thick unstable layers and a relative paucity of thinner layers at near 12 km altitude at Koror (7.3 N, 134.5 E), which is also called ?notch?, present at other near equatorial stations? In what way might this ?notch? be related to the minimum in atmospheric stability that has been noted earlier by other authors in the same general atmospheric region? The research plan to address question 1 is to try to identify differences in the times and locations of atmospheric gravity buoyancy waves that lead to the lower stratospheric unstable layers. This is planned to be done using a ray-tracing methodology. The research plan to address question 2 is to compare the geographical and temporal variation of the ?notch? feature to that of the stability minimum. The investigators also plan to identify the ?notch? feature with in-cloud and cloud-outflow turbulence.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
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.
While we carried out the project “Processes determining the climatology of atmospheric unstable layers”, we explored the mechanism how atmospheric unstable layers are generated.
We found that atmospheric unstable layers can arise from the breakings of gravity waves, which have propagated from their source regions. For example, an unstable layer that occurred at 00UTC, January 10, 2007 over Riverton, WY is depicted in Figure 1. The Richardson number, Ri, shown in Figure 1(a) clearly indicates the dynamically unstable altitudes near 19 km, where Ri < 0.25. Figures 1(b) and 1(c) show the Thorpe displacements and the cumulative Thorpe displacements. Applying the theory of order statistics to the Thorpe displacements depicted in Figure 1(b), only the overturn near 19 km is statistically significant at the 99% percentile level. The Thorpe length of the overturn is 110 m as shown in Figure 1(d).
Then we further used the hodograph analysis and Stokes-parameter analysis to estimate the gravity wave parameters around the overturn. Obtained from the GROGRAT model, figure 2 shows the trajectory of reverse 4-D ray-tracing of the gravity wave back to its source, which was located in the frontal cyclone that was causing a cold wave in the Northwestern United States and spawning various trains of gravity waves in that region.
We also verified that that atmospheric unstable layers can arise from the in-situ Kelvin-Helmholtz Instabilities, which have been pointed out by various previous literatures.
Last Modified: 03/03/2025
Modified by: Tiehan Zhou
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