Statistical Data Analysis, PhD in Physics

Tihomir S. Hristov, Ph.D.

Department of Mechanical Engineering, Johns Hopkins University

443-***-**** (C); *******.*******@***.***, ****************@*****.*** Citizenship: US Citizen

Education: Space Research Institute

Bulgarian Academy of Sciences, So a, Bulgaria

Ph.D. in Physics, 1993

A study on plasma

ow instabilities, regarding the problem of accretion onto compact objects.

Sofia University, Bulgaria

Department of Physics, So a, Bulgaria

Master of Science in Physics, 1988

Major in High Energy Physics

Scientific

Accomplishments:

First to: (i) Experimentally detect the wave-induced elds in the atmospheric surface layer over the ocean, the key to understanding the physics of wind-wave interaction and wave generation by wind. (ii) Find experimental support for the critical layer theory of wind-wave interaction. (iii) Propose a statistically rigorous model for scattering from the ocean surface. (iv) Develop a physical phase-resolved description for the dynamic and statistical structure of a wavy boundary layer suitable for operational use.

Academic

Positions:

Johns Hopkins University, School of Engineering

Associate Research Scientist, (2005 - present)

Johns Hopkins University, School of Arts and Sciences Associate Research Scientist, (2001 - 2005)

Univ. California, Irvine, Dept. Mechanical & Aerospace Eng. Assistant Research Professor, (1994 - 2001)

Teaching: 1999 University of California Irvine, Engineering Mechanics 2016 Johns Hopkins University, Engineering Fluid Mechanics ONR Supported

Projects:

Marine Boundary Layers (MBL) Experiment

Rough Evaporation Duct (RED) Experiment

Coupled Boundary Layers Air-Sea Transfers (CBLAST) Experiment High Resolution Air-Sea Interaction (HiRes) Experiment An Outline of Work and Teaching Experience

Working at the Johns Hopkins University has been a great experience including research and teaching responsibilities. My background in Physics, Astrophysics, and Geophysical Fluid mechanics has been accumulated from my education and science practice and has been very helpful in entering new research areas.

My research has been focused on planning, organizing, executing, and interpreting large scale field projects in geophysical fluid dynamics, with experimental, analytical and compu- tational components. The field experiments took place in the challenging environment of the high seas in atmospheric conditions and sea states that test the limits of the equipment as well as the scientists dedication and endurance. The projects involved supervising students and engineers and presented the opportunity to work with people with diverse expertise and work styles, from US and international academic institutions, tech companies, and Govern- ment laboratories. The projects have been supported by the Office of Naval Research and addressed unsolved problems of great basic science and applied interest and related of air- sea interaction, micrometeorological and mechanistic description of the marine atmospheric boundary layer, models of climate, weather and wave forecasting, waves in random media, tropospheric propagation of electro-magnetic and electro-optical signals. A matter of pride has been the opportunity to use unique and remarkable scientific instruments such as the FLoating Instrument Platform (FLIP) (which, when not used in experiments is stationed at the Scripps Institution of Oceanography) as well as the Air-Sea Interaction Tower, located off the coast of Marthas Vineyard in Massachusetts. In the preparation stage of these projects I have done organizational and technical work, the latter including building deployment gear and integrating a multitude of sensors, for point measurements and remote sensing, in an automated experiment control and data collection system that was used in the field. Among the measurements performed were fluid-mechanical fields of atmospheric and oceanic turbu- lence, motion of the ocean surface, inertial navigation measurements, particle size spectra, characteristics of electro-magnetic and electro-optical transmission, etc. I have felt a particular responsibility and interest in the phase of interpreting experimental results, where new science is distilled from data. Papers I have written as first and corre- sponding author have appeared in journals such as Nature, Physical Review Letters, Physics of Plasmas, Journal of Physical Oceanography, Transactions of Antennas and Propagation, Boundary-Layer Meteorology, etc.

A specific unanswered scientific question of great interest for me has been how the wind generates the surface waves in the ocean. Accomplished scientists such as Lord Kelvin and Richard Feynman have worked on this longstanding and challenging problem, the latter describing the experience as We put our foot in a swamp and we pulled it up muddy. Thanks to the support from ONR, to the access to unique instruments like FLIP, and to constructive input from multiple colleagues, the research summarized above has produced a persuasive and conclusive answer identifying the physical mechanism responsible for the wind generation of ocean waves. The combination of analytic work and interpretation of experimental data has revealed existence and the essential role of an organized motion in the air, commonly masked by the much more intense turbulence that carries and embodies the wind wave interaction. Furthermore, the work has proven the dynamic significance of in Fig. 4 for the R/P

of five 3-axis sonic ane-

tum and buoyancy fluxes

3 and 17mabove

on either

of the R/P ’s port boom were excluded from

orms used to directly measure flux–profile relationships during the CBLAST, MBL, and The ASIT tower used in CBLASTwheretheprofilingmastisatfarleftandthemastholding r the platform. (middle) The R/P in MBL and (right) the tower used in the et al. (2001). The setup shown in Fig. 4 for the R/P of a vertical array of five 3-axis soni

to measure momentum and buoyancy

IG. 4. The three platforms used to directly m

s. (left) The ASIT tower used in

is nearer the platform. (midd

Figure 1: The Floating Instrument Platform (FLIP) during the Marine Boundary Layers experiment (left) and the Air-Sea Interaction Tower (ASIT) during the Coupled Boundary Layers Air-Sea Transfers experiment (right).

a particular location in the flow, where the mean speed of the airflow matches the phase speed of the underlying wave, known as the critical layer. The analysis of experimental data for the first time demonstrated that the critical layer is observable in field data, a fact that uniquely pointed to the physical mechanism responsible for the wave generation. Also for the first time, relationship between mechanistic, empirical and numerical description of the wind-wave interaction has been established, thus unifying the knowledge on the problem of wind-wave interaction available from different approaches. Another decades-old problem the solution of which gave me a great satisfaction was reconciling the discrepancy between models and measurements regarding the propagation patterns in evaporative ducts over the ocean. A statistically rigorous model for scattering from the rough ocean surface substantially reduced the discrepancy in frequency bands of interest for the US Navy.

I found teaching and advising students as rewarding and enjoyable. Both at the University of California, Irvine and at Johns Hopkins University I have taught classes on Engineering Mechanics and Engineering Fluid Mechanics.

Representative

Publications:

1. L. Mahrt, S. Miller, T. Hristov, J. Edson, On estimating the surface wind stress over the sea, J. Phys. Oceanography, Published Online: 30 May 2018, https://doi.org/10.1175/JPO-D-17-0267.1 .

2. T. Hristov, Mechanistic, empirical and numerical perspectives on wind-waves interaction. Proceedings of the 2017 IUTAM Symposium on Wind Waves held at the University College of London, UK, September 4{10, 2017. Elsevier. DOI: https://doi.org/10.1016/j.piutam.2018.03.010, http://www.sciencedirect.com/science/article/pii/S2210983818300105 . 3. L Wu, A. Rutgerson, T. Hristov. Vertical Pro les of Wave-Coherent Momen- tum Flux and Velocity Variances in the Marine Atmospheric Boundary Layer. J. Phys. Oceanography March 2018, Vol. 48, No. 3.

4. T Hristov. Generation of Waves by Wind. Chapter in Wiley Encyclopedia of Maritime and O shore Engineering, John Wiley & Sons, Ltd, 2017. doi: 10.1002/978**********.emoe081.

URL http://dx.doi.org/10.1002/978**********.emoe081. 5. L. Mahrt, T. Hristov, Is the In

uence of Stability on the Sea Surface Heat Flux Important? J. Phys. Oceanography 47(3), pp. 689-699. 6. T. Hristov and J. Ruiz-Plancarte. Dynamic balances in a wavy boundary layer. J. Phys. Oceanography, 44(12), December 2014, pp. 3185{3194. 7. Hogstro m U., T. Hristov et al., Air-Sea Interaction Features in the Baltic Sea and at a Paci c Trade-Wind Site: An Inter-comparison Study. Boundary- Layer Meteorology, 147, 2013, pp. 139{163.

8. Z. D. Dimitrov, Y. G. Maneva, T. S. Hristov, and T. M. Mishonov, Over- re

ection of slow magnetosonic waves by homogeneous shear

ow: Analytical solution. Phys. Plasmas 18, 2011.

9. Z. D. Dimitrov, Y. G. Maneva, T. S. Hristov and T. M. Mishonov, Non- linear Terms of MHD Equations for Homogeneous Magnetized Shear Flow, arXiv:1103.4999 [physics.plasm-ph], 2011.

10. P. P. Sullivan, J.C. McWilliams, T. Hristov, Large eddy simulation of high wind marine boundary layers above a spectrum of resolved moving waves. AMS 19th Symposium on Boundary Layers and Turbulence, 1-6 August 2010, Keystone, CO,

https://ams.confex.com/ams/19Ag19BLT9Urban/techprogram/paper_172658.htm. 11. T. M. Mishonov, Z. D. Dimitrov, Y. G. Maneva, T. S. Hristov, Ampli cation of Slow Magnetosonic Waves by Shear Flow: Heating and Friction Mechanisms of Accretion Disks,

http://proceedings.aip.org/resource/2/apcpcs/1121/1/28_1. 12. T. Hristov. Compensation of Signal Distortions in Measurements of Turbulent Atmospheric Pressure. Boundary-Layer Meteorology, 129, 2008, pp. 497{507. 13. S. D. Miller, T.S. Hristov, J.B. Edson, and C.A. Friehe, Platform Motion E ects on Measurements of Turbulence and Air-Sea Exchange Over the Open Ocean. Journal of Atmospheric and Oceanic Technology, 25, September 2008, pp. 1683{1694.

14. P. Sullivan, J. Edson, T. Hristov, J. McWilliams. Large eddy simulations and observations of atmospheric marine boundary layers above non-equilibrium surface waves. Journal of Atmospheric Sciences, 65, April 2008, pp. 1225{ 1245.

15. T. Hristov, K.D. Anderson, and C. Friehe. Scattering properties of the ocean surface: The Miller-Brown model revisited. IEEE Transactions of Antennas and Propagation. 56, No. 4, April 2008, pp. 1103{1109. 16. T. Hristov and J. Edson. Surface Wave Modulation of Atmospheric Refrac- tivity and Remote Sensing over the Ocean. American Meteorological Society, 15th Conference on Air-Sea Interaction, 20 { 23 August 2007, Portland, Ore- gon.

17. J. Edson, T. Hristov et al., The Coupled Boundary Layers and Air-Sea Trans- fer Experiment in Low Winds (CBLAST-LOW). Bulletin of the American Meteorological Society, 88, March 2007, pp. 341{356. 18. P. P. Sullivan, J. B. Edson, and T. Hristov. 7C.6, Momentum Flux Structures and Statistics in Low-Wind Marine Surface Layers: Observations and Large- Eddy Simulations. 27th Conference on Hurricanes and Tropical Meteorology, 24{28 April 2006, Monterey, CA.

19. T. Hristov, K. Anderson, J. Edson and C. Friehe. P8.3 Dynamics of the Surface Layer Over the Ocean as Revealed from Field Measurements of the Atmospheric Pressure, American Meteorological Society, 16th Symposium on Boundary Layers and Turbulence, 9-13 August 2004, Portland, Maine. 20. K. Anderson, T. Hristov, et al. The Rough Evaporation Duct (RED) Experi- ment; An Assessment of Boundary Layer E ects in a Trade Winds Regime on Microwave and Infrared Propagation over the Sea. Bulletin of the American Meteorological Society, 85, September 2004, pp. 1355{1365. 21. T. Hristov, S. Miller, and C. Friehe. Dynamical coupling of wind and ocean waves through wave-induced air

ow. Nature 422:55{58 (06 March 2003). 22. C. A. Friehe and T. Hristov. Scalar Flux-Pro le Relations Over the Open Ocean. 83rd Annual Meeting of the American Meteorological Society, 9{13 February, 2003, Long Beach, California.

23. T. Hristov, C. A. Friehe. EM Propagation Over the Ocean: Analysis of RED Experiment Data. 83rd Annual Meeting of the American Meteorological Society, 9{13 February, 2003, Long Beach, California. 24. G. D. Chagelishvili, R. G. Chanishvili, T. S. Hristov, and J. G. Lominadze. A Turbulence Model in Unbounded Smooth Shear Flows: The Weak Turbulence Approach. Journal of Experimental and Theoretical Physics, 94, No. 2, pp. 434-445, 2002.

25. T. Hristov, S. Miller, and C. Friehe. Linear time-invariant compensation of cup anemometer and vane inertia. Boundary-Layer Meteorology, 97(2):293- 307, November 2000.

26. P. L. Fuehrer, C. A. Friehe, T. S. Hristov, D. I. Cooper, and W. E. Eichinger. Statistical uncertainty-based adaptive ltering of lidar signals. Applied Op- tics, 39(5):850-859, February 2000.

27. T. Hristov, C. Friehe, and S. Miller. Wave-coherent elds in air

ow over ocean waves: Identi cation of cooperative behavior buried in turbulence. Phys. Rev. Letters, 81:5245-5248, December 1998.

28. T. Hristov, C. Friehe, S. Miller, J. Edson, S. Wetzel. Structure in the Atmo- spheric Surface Layer over Open Ocean Waves: Representation in Terms of Phase Averages. Wind-Over-Waves Couplings: Perspectives and Prospects, Southend-on-sea, Essex, UK, 1997.

29. Miller, S.D., Friehe, C.A., Hristov, T.S., and Edson, J.B. (1997) Wind and turbulence pro les in the surface layer over ocean waves. Wind-Over-Waves Couplings: Perspectives and Prospects, Southend-on-sea, Essex, UK, 1997. 30. A. Rogers, Hampton N. Shirer, George S. Young, Laurentia Suciu, Robert Wells, James Edson, Suzanne W. Wetzel, Carl Friehe, Tihomir Hristov, Scott Miller. Using the Chaotic Behavior of the Time Series Observed on FLIP to Identify MABL Coherent Structures 12th Symposium on Boundary Layers and Turbulence Vancouver, Canada, July 28 { August 1, 1997. 31. T. Hristov, C. Friehe, S. Miller, J. Edson, S. Wetzel. Structure of the At- mospheric Surface Layer Over the Ocean Waves Phase Averaging via the Hilbert Transform 12th Symposium on Boundary Layers and Turbulence Van- couver, Canada, July 28 { August 1, 1997.

32. S. Miller, C. Friehe, T. Hristov, J. Edson. Wind and Turbulence Pro les in the Surface Layer Over the Ocean. 12th Symposium on Boundary Layers and Turbulence Vancouver, Canada, July 28 { August 1, 1997. 33. J. Edson, S. Wetzel, C. Friehe, S. Miller, T. Hristov. Energy Flux and Dissi- pation Pro les in the Marine Surface Layer. 12th Symposium on Boundary Layers and Turbulence Vancouver, Canada, July 28 { August 1, 1997. Other

Publications:

34. Chagelishvili G., T. Hristov, R. Chanishvili. A mechanism of energy transfor- mations in shear magnetohydrodynamic

ows. Phys. Rev. E, 47:342, 1993. 35. N.I.Karchev, T.S.Hristov. Spin-Wave Theory of the Spiral Phase of the t-J Model. Phys. Rev. B. 47, No 14, p.8613, 1993.

36. Chagelishvili G., T. Hristov, R. Chanishvili. Ampli cation of Alfven waves in free shear

ows. Advances in Space Research, ISSN 0273-1177, Pergamon Press, 1991.

37. T. Mishonov, T. Hristov. Noise in superconducting magnets. Commun. JINR

{ Dubna. E17-90-563, 1990.

38. A. Proykova, K. Hristova, T. Hristov, N.Nenov, D. Kolev. Radiation from a large Cylindrical Source. Applied Radiation and Isotopes. 42, No.3:279, 1991. 39. T. Hristov, A. Groshev. Coupled Josephson and piezo oscillators the e ects of quality, capacitance and noise. Physica C, 175:600, 1991. 40. Groshev A., T. Hristov. Shapiro steps without RF source by coupling of Josephson and piezo oscillators. Physica C, 160:317, 1989. 41. V. Detcheva, M. Metodieva, T. Hristov, B. D. Kandilarov. One dimensional Dirac equation approach to the e ective mass concept in diatomic crystals. Phys. stat. sol. (b), 152:163, 1989.

42. T. Mishonov, T. Hristov, A. Groshev. Physics problems for students. Narodna prosveta, So a 1983. (in bulgarian)

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