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Prof. Isztar Zawadzki

Isztar Zawadzki

Cloud Physics and Radar Meteorology

Office: Burnside Hall 824 | 825
Tel.: (514) 398-1034
Fax.: (514) 398-6115
Website
isztar [dot] zawadzki [at] mcgill [dot] ca (E-mail)


Research interests

Doppler radars are highly sophisticated instruments for the remote sensing of the atmosphere. Operational scanning radars provide, every five minutes or so, a volume scan of the atmosphere. Radar echoes from this volume give information on the spatial distribution of precipitation content and the scatterers velocity in the radar beam direction (radial velocity component in spherical coordinates). These observations are made with a resolution and area coverage sufficient to study most of the severe weather phenomena and the mesoscale organization of precipitation systems. This direct sounding of nature, however, is insufficient for unambiguous physical interpretation of the measurements. The radial velocity is but one component out of three. The interpretation of the radar received power is ambiguous due to the variety of scatterers (rain, snow, hail, graupel, etc.), each with its own electromagnetic properties.

Numerical models of atmospheric phenomena, on the other hand, give an approximation to a complete phenomenological description of the atmosphere. However, for a model to reproduce a particular weather event on the mesoscale, sufficient information on the event must be introduced into the model. This may take the form of a time series of measurements such as those provided by the radar. Thus, radar and models have complementary features and the recent advances in both fields are such that we are ready to attempt the integration of radar.

Several radar related projects are underway. We are perfecting techniques, based on variational analysis, for the retrieval of the three dimensional wind field as well as the pressure and temperature perturbations from single Doppler radar observations of storms. The processes leading to the formation of precipitation are studied with the help of radar observations leading to a better understanding and improved representation in numerical models

The extraction of hydrological information contained in radar data is refined and results are compared to gages and hydrological information.

Radar information and the numerical modelling of air flow is combined to study phenomena such as icing conditions (presence of supercooled water) and severe wind shear conditions with applications to aviation meteorology.

Very short term forecasting of precipitation are developed and continuously perfected.

At the same time we are continuously perfecting our instruments and data processing techniques.

For more information on the variety of our instruments and research: http://www.radar.mcgill.ca


Winter Atlantic Storm Thumb

Click image for larger version

Distribution in space of the indicated types of hydrometeores in a winter Atlantic storm. These distributions were obtained by simulating the development of precipitacion with a microphysical model driven by an air flow derived from radar observations. The figure was produced for a study on air craft icing conditions in winter storms.


Some recent publications

Chung, K-S., I. Zawadzki, M.K. Yau, and L. Fillion, 2009: Short-term forecasting of a midlatitude convective storm by the assimilation of single Doppler radar observations. Mon. Wea. Rev., In print

Berenguer, M. and I. Zawadzki, 2009: A study of the error covariance matrix of radar rainfall estimates in stratiform rain. Part II: scale dependence. Weather and Forecasting, 24, 800-811.

Lee, Ch. K., G. W. Lee, I. Zawadzki, and K. E. Kim, 2008: Spatial Variability of Rain Drop Size Distributions During Stratiform Rain Events. J. App. Met. Clim., 48, 270-283.

Berenguer, M. and I. Zawadzki, 2008: A study of the error covariance matrix of radar rainfall estimates in stratiform rain, Weather nad Forecasting, 23, 1085-1101.

Heyraud, C., W. Szyrmer, S. Laroche and I. Zawadzki, 2008: Modeling of the melting layer. Part IV: Brightband Bulk Parametrization. J. Atmos. Sci. 65, 1991-2001.

Bellon, A., Lee, G. W., Kilambi, A. and I. Zawadzki, 2007: Real-time comparison of VPR-corrected daily rainfall estimates with gage mesonet. J. of Appl. Meteorology. 46, 726-741.

Hocking, W. K., T. Carey-Smith, D. W. Tarasick, P. S. Argall, K. Strong, Y. Rochon, I. Zawadzki and P. A. Taylor, 2007: Detection of stratospheric ozone intrusions by windprofiler radars. Nature, 450, 281-284.

S. Vasić, Charles A. Lin, Ch. A., Zawadzki, I., Bousquet, O. and Chaumont, D., 2007: Evaluation of Precipitation from Numerical Weather Prediction Models using Values Retrieved from Radars and Satellites. Monthly Weather Review, 135, 3750-3766.

Bousquet, O., Charles A. Lin, Ch. A. and I. Zawadzki, 2006: Analysis of scale dependence of quantitative precipitation forecast verification: A case-study over the Mackenzie river basin, Q. J. Roy. Met. Soc.. 132, 2107-2125

Lee, G. W., and I. Zawadzki, 2006: Radar calibration by gage, disdrometer, and polarimetry: theoretical limit caused by the variability of drop size distribution and application to fast scanning operational radar data. Journal of Hydrology, 328, 83-97.

Campos, E., I. Zawadzki, Petitdidier, M. and Fernández, W., 2006: Measurements of drop size distribution in tropical rain at Costa Rica. Journal of Hydrology, 328, 98-109.

Lee, G. W., A. Seed and I. Zawadzki, 2006: Modeling the variability of drop size distribution in space and time. J. of Appl. Meteorology. Accepted.

Cho, Y., K. Kim. G. Lee and I. Zawadzki, 2006: Identification and removal of ground echoes and anomalous propagation using the characteristics of radar echoes. J. Atmos. Oceanic Technol., 23, 1206-1222.

Germann, U., I. Zawadzki and B. Turner, 2006: Scale dependence of predictability of precipitation from continental radar images. Part IV: Limits to prediction. J. Atmos. Sci. 63, 2092-2108.

Bellon, A., Lee, G. W. and I. Zawadzki, 2005: Error Statistics of VPR Corrections In Stratiform Precipitation. J. of Appl. Meteorology, 44, 998-1015.

Szyrmer, W., S. Laroche and I. Zawadzki, 2005: A Microphysical Bulk Formulation Based on Scaling Normalization. Part I: Description. J. Atmos. Sci. 62, 4206-4221.

Laroche, S., W. Szyrmer and I. Zawadzki, 2005: A microphysical bulk formulation based on scaling normalization. Part II: Data assimilation into physical processes. J. Atmos. Sci. 62, 4222-4247.

Zawadzki, I., W. Szyrmer, C. Bell and F. Fabry, 2005: Modeling of the melting layer. Part III: The density effect. Journal of Atmospheric Sciences, 62, 3705–3723.

Bellon, A., Lee, G. and I. Zawadzki, 2005: Error Statistics of VPR Corrections In Stratiform Precipitation. Journal of Applied Meteorology, 44, 998-1015.

Lin, Ch., S. Vasić, A. Kilambi, B. Turner, I. Zawadzki, 2005: Precipitation Forecast Skill of Numerical Weather Prediction Models and Radar Nowcasts. Geophysical Research Letters. 32, No. 14.

Lee, G. and I. Zawadzki, 2005: Variability of drop size distributions: Noise and Noise filtering in disdrometric data. Journal of Applied Meteorology, 44, 634-652.

Lee, G. and I. Zawadzki, 2005: Variability of drop size distributions: Time scale dependence of the variability and its effects on rain estimation. Journal of Applied Meteorology, 44, 241-255.

Lee, G., I. Zawadzki, W. Szyrmer, D. Sempere-Torres, and R. Uijlenhoet, 2004. A general approach to double-moment normalization of drop size distributions. J. Applied Meteorology, 43, 264-281.

Turner, B., I. Zawadzki and U. Germann, 2004: Scale dependence of predictability of precipitation from continental radar images. Part 3: Operational implementation. J. of Appl. Meteorology, 43, 231–248.

Germann, U. and I. Zawadzki, 2004: Scale dependence of predictability of precipitation from continental radar images. Part 2: Probability Forcasts. J. of Appl. Meteorology, 43, 74-89.

Miriovsky, Benjamin J., Bradley, A. Allen, Eichinger, William E., Krajewski, Witold F., Kruger, Anton, Nelson, Brian R., Creutin, Jean-Dominique, Lapetite, Jean-Marc, Lee, Gyu Won, Zawadzki, I., Ogden, F. L., 2004: An Experimental Study of Small-Scale Variability of Radar Reflectivity Using Disdrometer Observations. J. of Appl. Meteorology, 43, 106–118.

Chandrasekar, V, R. Meneghini and I. Zawadzki, 2003: Global and Local Precipitation Measurements By Radar, Invited paper for the AMS Meteorological Monographs, 30, pp. 215–215.

Fabry, F., and I. Zawadzki, 2002: New observational technologies: scientific and societal impacts. Meteorology at the millennium, Academic Press, ISBN 0 12 548035 0, 72 82 (invited contribution).