| NSF Org: |
AGS Division of Atmospheric and Geospace Sciences |
| Recipient: |
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| Initial Amendment Date: | February 11, 2014 |
| Latest Amendment Date: | February 11, 2014 |
| Award Number: | 1355567 |
| 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: | April 1, 2014 |
| End Date: | March 31, 2019 (Estimated) |
| Total Intended Award Amount: | $661,374.00 |
| Total Awarded Amount to Date: | $661,374.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
4333 BROOKLYN AVE NE SEATTLE WA US 98195-1016 (206)543-4043 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
4333 Brooklyn Ave NE Seattle WA US 98105-1016 |
| 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 |
| 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 project uses the National Center for Atmospheric Research S-PolKa radar to address a primary goal of the Dynamics of the Madden-Julian Oscillation (MJO) field experiment (DYNAMO): to document the evolution of the cloud population of the MJO throughout its cycle from suppressed to active and back to suppressed conditions. S-PolKa was uniquely capable of achieving this goal because of: (1) its ability to see not only the precipitating convection but also the nonprecipitating clouds; and (2) its dual-polarization technology that allowed determination of the microphysical as well as kinematic and precipitation structure of the precipitating convection. Working in concert with other radars, S-PolKa provided a wealth of information on the convective cloud evolution in the MJO, and this project determines the organization and structure of the cloud population at all of its stages of the MJO through analysis of the S-PolKa data and comparison with model output. The high sensitivity of the S-band S-PolKa radar provided observations of nonprecipitating clouds. In highly suppressed conditions, the MJO cloud population occurs initially in lines of small cumulus. When some of these clouds precipitate, the showers form cold pools, which take over the boundary layer structure. The cold pools trigger more and larger convection until the deep precipitating convection begins to dominate. The nonprecipitating clouds are seen by S-PolKa because they produce Bragg scattering, with identifiable dual-polarization signatures. Analysis of the S-PolKa scans will document the organization and evolution of the clouds into lines and cold pool patterns. A co-located vertically pointing Ka-band radar (the DOE KAZR) will add vertical structure information. The empirical characteristics of the shallow clouds will be compared to fine resolution numerical model output. S-PolKa?s dual-polarization data indicates the dominant microphysical characteristics of deeper convection and mesoscale convective systems (MCSs). Two types of MCSs occurred: squall-lines with trailing stratiform precipitation and non-squall systems in which stratiform precipitation formed from the dying of convective cells. The microphysical and kinematic structures of both types of MCS will be determined from S-PolKa. A nearly co-located C-band Doppler radar (SMART-R)will provide additional kinematic information. Comparison with regional model output will give insight into how the MCSs developed and how they were affected by wind shear and other environmental factors. Comparison of the DYNAMO observations with other NSF deployments (TiMREX and NAME) will indicate how the equatorial convection differs from MCSs in the subtropics near and over land and complex terrain.
The characteristics of shallow, deep, and mesoscale convective elements derived from S-PolKa and the other radars will facilitate understanding of the contributions of the individual components to the aggregated cloud ensemble of the MJO. It is also important to understand how the composition of the cloud population evolves. The DYNAMO S-PolKa data shows that the MJO cloud population development is multiscale. The convectively active period of an MJO lasts from 1-4 weeks. Within this period the convection is controlled by intermediate-scale equatorial waves, which concentrate the convective population into shorter 2-4 day periods in which the convective population goes through a similar cycle of growth and decline. This intermediate scale is important, lying between cloud scale and MJO scale. To study this intermediate-scale behavior, the S-PolKa data will be examined in light of Indian Ocean basin-wide simulations of the multiscale behavior of the MJO.
A primary goal of DYNAMO was to determine the details of the evolution of the cloud population of the MJO as it develops over the Indian Ocean. This project will be a major contribution toward the achievement of that aim.
Broader Impacts:
The MJO affects weather globally, from variations in the Asian monsoon to variations in winter weather over the U.S. The physical understanding provided by this project's analysis of the S-PolKa dataset underpins the development of better models to forecast the MJO. In addition, the project contributes to the training of women scientists.
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.
This project collected and analyzed data from the S-Polka radar located on Addu Atoll inthe equatorial Indian Ocean to better understand the population of convection in theMadden-Julian Oscillation (MJO), which becomes active every 30-60 days and affectsweather around the globe, especially in North America. This study showed how thepopulation of convective clouds evolves from undisturbed to highly disturbed weatherconditions. First, lines of small non-precipitating clouds form in the atmosphericboundary layer. When some of them begin to precipitate, downdrafts dramatically changethe nature of the boundary layer. As spreading downdrafts bump into each other, biggerconvective clouds form, with bigger downdrafts. Eventually some of the clouds becomegigantic mesoscale convective systems, which heat the upper tropospheric. Thesemesoscale systems dominate the cloud population during the most disturbed time periods.This study shows further that the convectively disturbed time periods are highlyintermittent within an active MJO phase. Convectively active times are controlled bysynoptic-scale events with 2-6 day periodicity. For the rest of the time in an active MJOperiod the convective clouds are small and suppressed. The study finds the diurnal cycleof convection is only evident in the convectively quiet stretches of time during an activeMJO phase. During the most active synoptic-scale time periods within an active MJOperiod the diurnal cycle is not evident in the convective cloudiness. The study shows thatthe microphysical structures of the clouds is determined by the nature of the convectiveelements and not directly controlled by diurnal, synoptic, or MJO scale processes.
Last Modified: 04/23/2019
Modified by: Robert A Houze
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