| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | January 28, 2020 |
| Latest Amendment Date: | January 28, 2020 |
| Award Number: | 1953791 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Nicholas Anderson
nanderso@nsf.gov (703)292-4715 AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | March 1, 2020 |
| End Date: | February 29, 2024 (Estimated) |
| Total Intended Award Amount: | $337,676.00 |
| Total Awarded Amount to Date: | $337,676.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
2301 S 3RD ST LOUISVILLE KY US 40208-1838 (502)852-3788 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
KY US 40292-0001 |
| 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): |
Physical & Dynamic Meteorology, EPSCoR Co-Funding |
| 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
Large cities can have significant impacts on local weather due to land-use characteristics. The Urban Heat Island is the most well-known consequence of cities, but prior research on precipitation and lightning has provided an indication that cities can also affect the location and strength of thunderstorms. This award provides funding for a numerical modeling study of the potential for urban storm modification with a specific focus on severe weather potential. The intent of the study is to determine which storm processes are most affected by an urban area and which urban features are most likely to modify significant storms. The output from this work will provide operational forecasters with additional information relevant to public safety. The award will also help to train the next generation of scientists through support of students and the development of learning modules for K-12 teachers.
This project intends to improve the understanding of interactions between deep convective storms and large urban areas. Most prior research in the area of storm-urban interactions has focused on weakly-forced events and/or the resultant precipitation from those storms, and the community has not coalesced around the dominant mechanism for storm modification (Urban Heat Island (UHI), flow obstruction, aerosols, moisture). This study will consist of a large parameter space study to investigate the cause-and-effect relationship between urban parameters and storm modification. The first step will be a CM1-based set of ~150 idealized sensitivity experiments, with grid sizes <250m. The WRF-ARW would then be used to examine instances of storm modification in real-data cases around Louisville, KY using a 10-member ensemble approach. The UHI will be adjusted by assimilating data from a network of 30 observation sites around the city. Finally, the observational network will be used to analyze the spatial variability in convective rainfall amounts. The overarching questions that the proposal would address are: 1) Which in-storm processes are most strongly affected by an encounter with a large urban area?, 2) What are the consequences of city-storm interactions as they relate to severe weather potential?, 3) How do different urban features impact the modification of deep convective storms?, and 4) What is the effect of environmental wind shear on urban modification?
This project is jointly funded by the Physical and Dynamic Meteorology program and the Established Program to Stimulate Competitive Research (EPSCoR).
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.
The purpose of this research was to 1) study interactions between urban areas and organized thunderstorms and 2) determine if Louisville, KY has a measurable impact on regional rainfall and/or thunderstorm activity. Objective (1) was completed via computer simulations of thunderstorms passing over a virtual city with defined properties. Objective (2) was completed by using real-world observations collected from platforms such as weather radar and surface weather stations. The results are summarized below.
-The updrafts in thunderstorms can strengthen when passing over an urban area. This effect is primarily caused by the urban heat island, which is defined as the temperature difference between an urban area and the surrounding rural region. Testing revealed that the larger surface roughness in urban areas compared to surrounding rural areas (due to wind flow obstructions such as tall buildings) has little impact on updraft evolution.
-Urban heat islands enhance squall line updrafts, resulting in more rainfall and hail downwind of the city. Stronger heat islands tend to produce larger rainfall/hail amounts downwind of the city. In the case of squall lines with updrafts that tilt back over the precipitation core, heat islands may also induce stronger surface wind gusts downwind of the city.
-Urban heat islands also influence supercells. Similar to squall lines, supercells experience enhanced precipitation downwind of a strong heat island. The urban heat island invigorates low level updraft of a supercell, which can strengthen near surface rotation and possibly have an impact on tornadogenesis.
-The urbanized area of Louisville, KY influences area precipitation in several notable ways. In the summer, strong, isolated thunderstorms are more common over Louisville than they are over nearby rural areas. The same is true for several other regional cities such as Cincinnati, OH, and Nashville, TN. In addition, Louisville experiences more precipitation on its eastern (i.e., downwind) side compared to its western (upwind) side. This downwind enhancement is largest during the peak summer months of June and July, but a smaller secondary peak occurs in September and October.
Last Modified: 05/14/2024
Modified by: Jason Naylor
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