From eoas-seminar at lists.fsu.edu Tue Dec 3 10:01:16 2019 From: eoas-seminar at lists.fsu.edu (eoas-seminar at lists.fsu.edu) Date: Tue, 3 Dec 2019 15:01:16 +0000 Subject: [Eoas-seminar] Meteorology PhD Defense for Sweta Das, December 5, 2019, 3:30 PM, Love 353 Message-ID: Meteorology Seminar Sweta Das PhD Meteorology Candidate Title: Understanding the evolution of Tropical Cyclones through the streamfunction-velocity potential framework Major Professor: Dr. Vasu Misra Co-Advisor: Dr. Guosheng Liu Date: December 5th, 2019 Time: 3.30 PM Location: Werner A. Baum Seminar Room (353 Love Building) (Please join us for refreshments served outside room 353 Love @ 3:00 PM) ABSTRACT The understanding of the evolution of a Tropical Cyclone (TC) has been a topic of research for several years. During the hurricane season not all thunderstorm events embedded in the African easterly waves or otherwise evolve into organized convection with a closed low pressure system, manifesting into TCs. In this work we suggest that one of the ways to objectively analyze the evolution of the TC is to understand the evolution of the conversion of the available potential energy into kinetic energy on the scale of the disturbance. This study explores the energetics of the interaction between Streamfunction (Psi[cid:image001.png at 01D5A9C0.99D202F0])- Velocity Potential (Chi: [cid:image002.png at 01D5A9C0.99D202F0] ) in the numerical simulations of the TCs. Using the output of separate 48-hour WRF simulations of three Atlantic TCs: Cindy and Irma of 2017, and Michael 2018, we analyze the time history of the conversion of their kinetic energy from the irrotational to the non-divergent components of the winds. All of these TCs had varied intensities with Cindy being the weakest and Irma being the strongest over the simulation period, which WRF simulated with reasonable fidelity in the evolution of their peak intensities. We show that at 850hPa, the fractional conversion of the kinetic energy from the irrotational to the non-divergent component of the wind increases as the TC intensifies and is higher for the stronger TCs than weaker TCs. Contrastingly, in the outflow level of the TC this transfer of kinetic energy is weaker for stronger TCs than the weaker TCs. Our analysis reveals that when the gradients of the streamfunction and velocity potential are large and oriented parallel to each other both in the large-scale TC environment and in the region of the primary circulation of the TC, then the TC is favored to intensify with robust conversion of the kinetic energy of the irrotational flow[cid:image003.png at 01D5A9C0.99D202F0] to kinetic energy of non-divergent flow ([cid:image004.png at 01D5A9C0.99D202F0] ) at 850hPa. In contrast, however in the outflow layer, we require a slower conversion of [cid:image005.png at 01D5A9C0.99D202F0] to [cid:image004.png at 01D5A9C0.99D202F0] for a TC to intensify otherwise it leads to increased inertial instability and weakening of the TC. We arrive at similar conclusions when we contrast the evolution of the tropical cyclones from its genesis to intensifying stages. Likewise, when we examine the sensitivity of the simulations of the tropical cyclones to the choice of microphysics, we find that parameterizations that engenders strong conversion of [cid:image005.png at 01D5A9C0.99D202F0] to [cid:image004.png at 01D5A9C0.99D202F0] at 850 hPa and weak conversion of [cid:image005.png at 01D5A9C0.99D202F0] to [cid:image004.png at 01D5A9C0.99D202F0] at the outflow level leads to the simulation of stronger TCs. Therefore, analyzing this conversion rate of kinetic energy of the flow field helps in understanding the evolution of the intensity of TCs. Shel McGuire Florida State University Academic Program Specialist Department of Earth, Ocean, & Atmospheric Science 1017 Academic Way, 410 Love Building (Meteorology) Tallahassee, FL 32306 850-644-8582 -------------- next part -------------- An HTML attachment was scrubbed... URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: image001.png Type: image/png Size: 336 bytes Desc: image001.png URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: image002.png Type: image/png Size: 315 bytes Desc: image002.png URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: image003.png Type: image/png Size: 492 bytes Desc: image003.png URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: image004.png Type: image/png Size: 405 bytes Desc: image004.png URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: image005.png Type: image/png Size: 395 bytes Desc: image005.png URL: From eoas-seminar at lists.fsu.edu Tue Dec 3 10:01:50 2019 From: eoas-seminar at lists.fsu.edu (eoas-seminar at lists.fsu.edu) Date: Tue, 3 Dec 2019 15:01:50 +0000 Subject: [Eoas-seminar] Meteorology MS Defense for Ethan Wright, December 10, 2019, 2:00 PM, Love 353 Message-ID: Meteorology Seminar Ethan Wright Master?s Meteorology Candidate Title: characterizing buoy wind speed error in extreme conditions through a comparison with scatterometers and era5 Reanalysis Major Professor: Dr. Mark Bourassa Date: December 10th, 2019 Time: 2:00 PM Location: Werner A. Baum Seminar Room (353 Love Building) (Please join us for refreshments served outside room 353 Love @ 1:30 PM) ABSTRACT Buoys are a common source of remote sensing validation data over the open ocean and are one of only a small number of in situ sources in this data sparse region. Previous studies have shown the presence of a low wind speed bias for buoys in extremely high wind conditions, but the data for the high wind speed ranges are limited. Therefore, it is important to test the validity of using buoys as an in situ source for satellite calibration in high winds and high seas using a relatively long record of buoy winds. Sub-setting scatterometer and buoy wind speed differences using wave parameters provides insight into the conditions under which wind speeds diverge between these wind sources. This study uses KNMI ASCAT and NASA QuikSCAT Ocean Vector Wind datasets to compare with buoy winds processed through the Global Telecommunications System and ECMWF ERA5 Reanalysis wave data from 1999 to 2018. The scatterometer, buoy and reanalysis data are triple collocated in space by less than 25 km, and time less than 30 minutes. A probability distribution function (PDF) analysis with wind speed differences sub-divided by wind speed ranges and wave characteristics is performed to test for the dependence of wind speed differences on changing sea states. Wind speed differences are further binned by anemometer height to investigate how physical buoy characteristics affect these differences. To account for buoy wind speed differences due to varying stability in the boundary layer, buoy winds at different anemometer heights are converted to 10 m equivalent neutral winds (U10EN) to compare with scatterometer winds. Comparisons show a difference between the high wind speed calibrations of QuikSCAT and ASCAT where QuikSCAT winds exceed buoy U10EN by nearly 4 m s-1 and ASCAT winds exceed buoy U10EN by 0.65 m s-1 on average in the 20 to 25 m s-1 buoy U10EN range. The PDFs of wind speed differences (Buoy U10EN ? Scatterometer) binned by wind speed ranges vary as a function of ERA5 significant wave height and buoy anemometer height. As significant wave height increases, buoy wind speed differences associated with low anemometers decrease further than wind speed differences measured with higher anemometers. This pattern is particularly apparent when significant wave heights exceeding 4 m are combined with wind speeds exceeding 12 m s-1. Therefore, it is important to consider modification of buoy winds by the wave profile in extreme conditions prior to their application to validate remotely sensed winds. Shel McGuire Florida State University Academic Program Specialist Department of Earth, Ocean, & Atmospheric Science 1017 Academic Way, 410 Love Building (Meteorology) Tallahassee, FL 32306 850-644-8582 -------------- next part -------------- An HTML attachment was scrubbed... URL: From eoas-seminar at lists.fsu.edu Thu Dec 5 13:10:36 2019 From: eoas-seminar at lists.fsu.edu (eoas-seminar at lists.fsu.edu) Date: Thu, 5 Dec 2019 18:10:36 +0000 Subject: [Eoas-seminar] TODAY: Meteorology PhD Defense for Sweta Das, December 5, 2019, 3:30 PM, Love 353 Message-ID: Meteorology Seminar Sweta Das PhD Meteorology Candidate Title: Understanding the evolution of Tropical Cyclones through the streamfunction-velocity potential framework Major Professor: Dr. Vasu Misra Co-Advisor: Dr. Guosheng Liu Date: December 5th, 2019 Time: 3.30 PM Location: Werner A. Baum Seminar Room (353 Love Building) (Please join us for refreshments served outside room 353 Love @ 3:00 PM) ABSTRACT The understanding of the evolution of a Tropical Cyclone (TC) has been a topic of research for several years. During the hurricane season not all thunderstorm events embedded in the African easterly waves or otherwise evolve into organized convection with a closed low pressure system, manifesting into TCs. In this work we suggest that one of the ways to objectively analyze the evolution of the TC is to understand the evolution of the conversion of the available potential energy into kinetic energy on the scale of the disturbance. This study explores the energetics of the interaction between Streamfunction (Psi[cid:image001.png at 01D5AB6D.60B2C050])- Velocity Potential (Chi: [cid:image002.png at 01D5AB6D.60B2C050] ) in the numerical simulations of the TCs. Using the output of separate 48-hour WRF simulations of three Atlantic TCs: Cindy and Irma of 2017, and Michael 2018, we analyze the time history of the conversion of their kinetic energy from the irrotational to the non-divergent components of the winds. All of these TCs had varied intensities with Cindy being the weakest and Irma being the strongest over the simulation period, which WRF simulated with reasonable fidelity in the evolution of their peak intensities. We show that at 850hPa, the fractional conversion of the kinetic energy from the irrotational to the non-divergent component of the wind increases as the TC intensifies and is higher for the stronger TCs than weaker TCs. Contrastingly, in the outflow level of the TC this transfer of kinetic energy is weaker for stronger TCs than the weaker TCs. Our analysis reveals that when the gradients of the streamfunction and velocity potential are large and oriented parallel to each other both in the large-scale TC environment and in the region of the primary circulation of the TC, then the TC is favored to intensify with robust conversion of the kinetic energy of the irrotational flow[cid:image003.png at 01D5AB6D.60B2C050] to kinetic energy of non-divergent flow ([cid:image004.png at 01D5AB6D.60B2C050] ) at 850hPa. In contrast, however in the outflow layer, we require a slower conversion of [cid:image005.png at 01D5AB6D.60B2C050] to [cid:image004.png at 01D5AB6D.60B2C050] for a TC to intensify otherwise it leads to increased inertial instability and weakening of the TC. We arrive at similar conclusions when we contrast the evolution of the tropical cyclones from its genesis to intensifying stages. Likewise, when we examine the sensitivity of the simulations of the tropical cyclones to the choice of microphysics, we find that parameterizations that engenders strong conversion of [cid:image005.png at 01D5AB6D.60B2C050] to [cid:image004.png at 01D5AB6D.60B2C050] at 850 hPa and weak conversion of [cid:image005.png at 01D5AB6D.60B2C050] to [cid:image004.png at 01D5AB6D.60B2C050] at the outflow level leads to the simulation of stronger TCs. Therefore, analyzing this conversion rate of kinetic energy of the flow field helps in understanding the evolution of the intensity of TCs. Shel McGuire Florida State University Academic Program Specialist Department of Earth, Ocean, & Atmospheric Science 1017 Academic Way, 410 Love Building (Meteorology) Tallahassee, FL 32306 850-644-8582 -------------- next part -------------- An HTML attachment was scrubbed... URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: image001.png Type: image/png Size: 336 bytes Desc: image001.png URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: image002.png Type: image/png Size: 315 bytes Desc: image002.png URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: image003.png Type: image/png Size: 492 bytes Desc: image003.png URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: image004.png Type: image/png Size: 405 bytes Desc: image004.png URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: image005.png Type: image/png Size: 395 bytes Desc: image005.png URL: From eoas-seminar at lists.fsu.edu Mon Dec 9 15:06:52 2019 From: eoas-seminar at lists.fsu.edu (eoas-seminar at lists.fsu.edu) Date: Mon, 9 Dec 2019 20:06:52 +0000 Subject: [Eoas-seminar] Meteorology MS Defense for Ethan Wright, December 10, 2019, 2:00 PM, Love 353 Message-ID: Meteorology Seminar Ethan Wright Master?s Meteorology Candidate Title: characterizing buoy wind speed error in extreme conditions through a comparison with scatterometers and era5 Reanalysis Major Professor: Dr. Mark Bourassa Date: December 10th, 2019 Time: 2:00 PM Location: Werner A. Baum Seminar Room (353 Love Building) (Please join us for refreshments served outside room 353 Love @ 1:30 PM) ABSTRACT Buoys are a common source of remote sensing validation data over the open ocean and are one of only a small number of in situ sources in this data sparse region. Previous studies have shown the presence of a low wind speed bias for buoys in extremely high wind conditions, but the data for the high wind speed ranges are limited. Therefore, it is important to test the validity of using buoys as an in situ source for satellite calibration in high winds and high seas using a relatively long record of buoy winds. Sub-setting scatterometer and buoy wind speed differences using wave parameters provides insight into the conditions under which wind speeds diverge between these wind sources. This study uses KNMI ASCAT and NASA QuikSCAT Ocean Vector Wind datasets to compare with buoy winds processed through the Global Telecommunications System and ECMWF ERA5 Reanalysis wave data from 1999 to 2018. The scatterometer, buoy and reanalysis data are triple collocated in space by less than 25 km, and time less than 30 minutes. A probability distribution function (PDF) analysis with wind speed differences sub-divided by wind speed ranges and wave characteristics is performed to test for the dependence of wind speed differences on changing sea states. Wind speed differences are further binned by anemometer height to investigate how physical buoy characteristics affect these differences. To account for buoy wind speed differences due to varying stability in the boundary layer, buoy winds at different anemometer heights are converted to 10 m equivalent neutral winds (U10EN) to compare with scatterometer winds. Comparisons show a difference between the high wind speed calibrations of QuikSCAT and ASCAT where QuikSCAT winds exceed buoy U10EN by nearly 4 m s-1 and ASCAT winds exceed buoy U10EN by 0.65 m s-1 on average in the 20 to 25 m s-1 buoy U10EN range. The PDFs of wind speed differences (Buoy U10EN ? Scatterometer) binned by wind speed ranges vary as a function of ERA5 significant wave height and buoy anemometer height. As significant wave height increases, buoy wind speed differences associated with low anemometers decrease further than wind speed differences measured with higher anemometers. This pattern is particularly apparent when significant wave heights exceeding 4 m are combined with wind speeds exceeding 12 m s-1. Therefore, it is important to consider modification of buoy winds by the wave profile in extreme conditions prior to their application to validate remotely sensed winds. Shel McGuire Florida State University Academic Program Specialist Department of Earth, Ocean, & Atmospheric Science 1017 Academic Way, 410 Love Building (Meteorology) Tallahassee, FL 32306 850-644-8582 -------------- next part -------------- An HTML attachment was scrubbed... URL: