| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | October 25, 2017 |
| Latest Amendment Date: | October 25, 2017 |
| Award Number: | 1763277 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Eric DeWeaver
edeweave@nsf.gov (703)292-8527 AGS Division of Atmospheric and Geospace Sciences GEO Directorate for Geosciences |
| Start Date: | July 1, 2017 |
| End Date: | September 30, 2019 (Estimated) |
| Total Intended Award Amount: | $241,536.00 |
| Total Awarded Amount to Date: | $241,536.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
1608 4TH ST STE 201 BERKELEY CA US 94710-1749 (510)643-3891 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
CA US 94704-5940 |
| 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: |
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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
This is a Faculty Early Career Development (CAREER) project to support a junior faculty member in developing and conducting an integrated 5-year program of research and education in atmospheric science. The research component examines the connection between monsoons and the deserts typically found adjacent to monsoon regions on the poleward side (as, for instance, the Sahara is poleward of and adjacent to the Sahel). Previous work by the PI shows that variations in precipitation in several monsoon regions including the Sahel, South Asia, and Australia, are positively correlated with equivalent potential temperature below the cloud layer over adjacent poleward deserts. One hypothesis for this relationship is that desert heat lows produce shallow overturning circulations in which outflow near the 700mb level has an equatorward component which reduces monsoon precipitation by warming and drying the mid-troposphere over the region of monsoonal deep convection. To advance understanding of such monsoon-desert relationships, work under this award will address three main questions: 1) Does shallow flow in desert heat lows alter monsoon precipitation primarily through horizontal advection of moisture and dry static energy? 2) How important are low-level transient eddies in interactions between desert heat lows and monsoons? 3) Do heat lows interact with monsoon precipitation in fundamentally the same way in West Africa, South Asia, and Australia? These research questions are addressed through a three-part research agenda in which the tasks are 1) characterize the monsoon-desert relationships found in observations, based on a combination of in situ, satellite, and reanalysis datasets; 2) explore these relationships using a simple theoretical model; and 3) conduct process studies using a state-of-the-art numerical model.
The educational component of this CAREER proposal involves the development of a monsoon forecasting contest with three goals: 1) fostering education on weather, climate, and relevant basic science; 2) enhancing recruitment and retention of high-promise, underrepresented high school students in science, technology, engineering, and math (STEM) fields; and 3) creating an international community for disseminating and discussing monsoon forecasts and research. The monsoon forecasting contest is held through a website which allows participants to enter forecasts of onset date and total seasonal precipitation for the monsoon regions of West Africa, India, Australia, and North America. Participants are asked to submit a rationale along with their predictions, and the website also contains educational materials on monsoons, along with basic science explanations for convection, generation of wind from pressure gradients, and other relevant topics. Guidance for forecasters, including climatological monsoon onset date and precipitation amount, the state of El Nino, and links to operational products. As part of the forecasting contest, the project seeks the participation of inhabitants of monsoon regions as forecasters and as bloggers, to provide a real-world perspective on monsoons and their human impacts. The forecasting contest is accompanied by an educational outreach effort to the New Haven Public School system. The outreach is conducted through the Science Collaborative Hands-On Learning And Research (SCHOLAR) program, in which students take part in a three-week residential summer science program at Yale. The PI is working with SCHOLAR staff to develop a short science module on weather, climate, and monsoons. In addition, in the last three years of the project, two students will be selected to attend a field trip organized by the PI's department.
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.
Monsoons are continental-scale atmospheric circulations that deliver water to billions of people in Africa, Asia, Australia, and the Americas, and monsoonal winds constitute an important part of the global circulation of Earth’s atmosphere. Yet the mechanisms that govern the variability of monsoons are poorly understood, poorly predicted, and poorly simulated by many global climate models. For decades, research has focused on ocean surface temperatures as a leading cause of monsoon variability; this project shifted attention back to land regions as a possible control on monsoon rainfall. Specifically, a large desert lies poleward of nearly every monsoon region on Earth, and this project investigated evidence for the influence of those desert regions on monsoon rainfall.
The project showed that desert regions can affect rainfall in nearby monsoon climates through mechanisms that were previously unknown or little explored. Shallow overturning circulations exist over deserts, with hot and dry desert air rising and then flowing horizontally into the neighboring humid monsoon region. This project showed that rainfall in the West African monsoon is weaker when the shallow desert circulation is stronger, contradicting the old idea that a stronger desert heat low driven by land-sea temperature contrast will “pull” more moisture inland and enhance rainfall. Transient vortices also form frequently over deserts and transport dry air into nearby monsoon regions, and this project showed that the net drying effect of those vortices on monsoons can be represented in terms of a diffusive approximation, with an eddy diffusivity acting on time-mean moisture gradients. This project also showed the important influence that mountains can have on interactions between deserts and monsoons, with the high and narrow mountain ranges west of Tibet preventing mixing of dry air from the desert regions of far western Asia into the Indian monsoon region. This mechanism was shown to be important in climate models, which due to their coarse resolution underrepresent the height of those mountain ranges and thereby allow too much dry air to penetrate into the South Asian monsoon. Finally, this project created several quantitative frameworks that can be used to assess the influence of the surface albedo of a desert on rainfall in an adjacent monsoon. A theory was created to show how a positive feedback between rainfall and local surface albedo over the Sahara in the mid-Holocene (about 6,000 years ago) dominated changes in the West African monsoon, thus providing theoretical quantification of the Sahara-Sahel interaction originally posited by Jule Charney in 1975. An idealized, one-dimensional energy budget model was also developed that allowed for exploration of feedbacks on an imposed radiative forcing, such as that associated with a change in desert surface albedo. Through a formal feedback analysis, this one-dimensional model was used to show that darkening of a desert surface would cause monsoon rainfall to shift toward the desert, but that the Planck, water vapor, and lapse-rate feedbacks all act to modify the response.
Science education and training were advanced in numerous ways by this project. During five summers, the principal investigator worked with over 100 high school students, most of whom were underrepresented minorities or who would be the first in their family to attend college. These students were introduced to the science of weather and climate and to related foundational concepts from physics and fluid dynamics. The project developed a science outreach website, https://WorldMonsoons.org, that displays current information on rainfall in monsoons around the planet together with educational web pages on monsoons targeted at a high school-level audience. Those educational webpages were also incorporated into the science education materials of the University Corporation for Atmospheric Research. About 15 undergraduate and master’s degree students participated in research and/or science-writing internships in the principal investigator’s group as part of this project. The project also trained two graduate students, who completed their Ph.D. dissertations as part of the project, and two postdoctoral scientists.
Last Modified: 01/06/2020
Modified by: William R Boos
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