| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | March 24, 2017 |
| Latest Amendment Date: | June 27, 2017 |
| Award Number: | 1660049 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Eric DeWeaver
edeweave@nsf.gov (703)292-8527 AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | April 1, 2017 |
| End Date: | March 31, 2022 (Estimated) |
| Total Intended Award Amount: | $446,104.00 |
| Total Awarded Amount to Date: | $446,104.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
1000 E 5TH ST GREENVILLE NC US 27858-2502 (252)328-9530 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
2200 S Charles Blvd Ste 2900 Greenville NC US 27858-4353 |
| 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): | Climate & Large-Scale Dynamics |
| Primary Program Source: |
01001819DB NSF RESEARCH & RELATED ACTIVIT 01001920DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
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The Southeastern United States (SE US) owes its ample water resources to many forms of precipitation, from the large-scale precipitation associated with frontal weather systems to sea-breeze convection associated with the adjacent Atlantic, to tropical cyclones, mesoscale convective systems and afternoon thunderstorms. These precipitation types differ in important ways including their predictability and their sensitivity to changes in regional climate, thus an understanding of their behavior and relative contributions to mean precipitation and precipitation change over the SE US is desirable. The PIs have developed a simple characterization of precipitating cloud systems into mesoscale precipitation features (MPFs), which consist of a contiguous region of precipitation of at least 100 km length, and smaller and shorter-lived isolated precipitation features (IPFs). Despite the simplicity of the classification scheme, it has proven effective for understanding the geographical and temporal behavior of SE US precipitation.
A key result of the PIs' previous research is that while MPFs (which include frontal precipitation and mesoscale convective systems) do not exhibit a strong seasonal cycle, the seasonal cycle of IPFs is characterized by a relatively abrupt spring onset occurring between May and June and concentrated over Florida, the adjacent coastline of the Gulf of Mexico, and the Atlantic coast as far north as Cape Hatteras. The onset of IPF rainfall over the SE US is somewhat reminiscent of the abrupt transition to the rainy season in monsoon regions such as West Africa and East Asia, which have been more extensively studied than the SE US.
Work conducted here explores the springtime IPF onset using a combination of observational data and numerical model simulations. Observational data come from the National Mosaic and Multi-sensor Quantitative Precipitation Estimation (NMQ) dataset, a precipitation dataset constructed from the NEXRAD network of radar stations that covers nearly all of the continental US. The PIs have developed an automated precipitation organization classification algorithm to identify MPFs and IPFs, and they apply the algorithm to 11 years (2002-2012) of NMQ data on an hourly basis to capture statistics of the spring IPF onset. These data will be used in conjunction with the North American Regional Reanalysis to assess contributions to the onset from thermodynamic factors such as convective available potential energy and convective inhibition, and circulation changes such as the seasonal movement of the North American subtropical high (NASH) and low-level jets in the region.
A further goal is to understand how IPF seasonality may change in a changing climate. The PIs hypothesize that the IPF onset should occur earlier in a warmer climate, as the relevant thermodynamic conditions would likely occur earlier in the year. Research on IPF sensitivity to background warming is conducted using the Weather Research and Forecasting (WRF) model, which is used to simulate weather and climate over a regional domain given meteorological conditions at the boundaries. The simulations use the pseudo global warming (PGW) method, in which meteorological conditions are taken from operational meteorological analysis to simulate the seasonal transition in recent years of record, and simulations are then repeated using boundary conditions to which differences between future and present-day climate simulations are added to represent anticipated climate change.
The seasonal transition of precipitation types over the SE US is of interest for practical as well as scientific reasons, as decision makers rely on weather and climate forecasts for agricultural planning as well as guidance on precipitation-related hazards and urban development. The PIs engage with local communities from Raleigh to the Outer Banks through venues including presentations at public libraries. Results of the project are used in courses taught by the PIs, in part through a WRF-based teaching laboratory for weather forecasting, which serves an educational purpose and also enhances the success of students pursuing careers in weather prediction.
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.
Forecasting trends in long-term regional precipitation across the southeastern United States, whether for the coming season or the coming decades, is critical information to plan water resource management, agriculture strategies, and public safety. Improving these forecasts requires significant advances in our understanding of how the climate system controls the seasonal and year-to-year variation of precipitation. Our project focuses on this connection for the southeastern United States.
Though our region receives precipitation year-round, we have limited understanding of how the atmosphere controls the transition from winter precipitation to heavy summer thunderstorms. This knowledge gap holds back our ability to forecast changes in precipitation for the upcoming season, and to forecast general trends of precipitation in the southeastern United States over the next several decades as the Earth warms.
In our previous NSF funded research we developed a novel automated method that uses weather radar data to distinguish between locally generated isolated thunderstorms and larger organized precipitation systems. This allowed us to discover that although seasonal springtime warming is gradual, the summer local thunderstorm regime begins quite abruptly, while large organized precipitation systems occur year-round.
In this project we built on our earlier discovery to investigate 1) the geographic extent and variability of the summertime thunderstorm precipitation regime in the continental United States, 2) the large-scale mechanisms for the abrupt onset of the summertime thunderstorm precipitation regime in the southeastern United States, and finally 3) how climate change may affect the transition to the summertime precipitation regime in the southeastern United States.
Our research confirmed that the onset of the summertime thunderstorm precipitation regime in the southeastern United States extends across the eastern United States but does not reach into the Great Plains. This abrupt onset of the summertime precipitation season occurs when the steady seasonal temperature increase combines with an abrupt change in the jet stream, the strong winds in the upper atmosphere that steer storm systems and control their organization. This rapid seasonal onset of locally generated afternoon thunderstorms after warm, moist air gets established is somewhat analogous to how a car’s engine quickly sparks to life after it is primed and cranked.
The second part of the project applied this knowledge to the challenging problem of forecasting future changes in regional precipitation due to climate change. The springtime transition to the local thunderstorm regime may act as a marker that we can use to assess and improve our ability to forecast future changes in precipitation trends. We used a series of computer model simulations to study how the timing and mechanisms for the start of the summer thunderstorm regime across the southeastern United States may change as the planet warms. We found that the model simulations not only capture the abrupt onset of the thunderstorm precipitation regime in the southeastern United States, but also that the onset occurs earlier in the future, warmer climate simulation. This is a first step toward better understanting how the seasonal pattern of precipitation is changing. The results from this project can be applied to other subtropical land regions of the world. and may ultimately help guide local communities to build resiliency in the face of a changing climate.
Last Modified: 08/25/2022
Modified by: Rosana Nieto-Ferreira
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