ULYANA DYUDINA Statement of research interests I believe that exploration of planets and their atmospheres is the most exciting topic in modern science because it is a key to understanding how our and other planetary systems formed and evolved. More than that, only now with modern computers and remote sensing a comprehensive description of the atmospheres becomes feasible. Many of my research projects have been related to the atmospheres of Earth and other planets. My approach to these projects has involved all the steps from data processing to constructing computer models and applying the models to important scientific questions. The topics I have addressed include mountain waves in Earth's atmosphere, clouds and lightning on Jupiter, and the behavior of the atmosphere and plasma torus of the Jovian satellite Io. I describe these projects below. RESEARCH EXPERIENCE Gravity waves in Earth's atmosphere are created by mountains. These waves generate lenticular clouds that make the waves visible. As a M.S. student, I studied stereophotographs of the lenticular clouds above the Crimean mountains to define the structure of the waves. I modeled these waves as a cylindrical flow over the nearly cylindrical ridge of the Crimean mountains. By comparing modeled and observed waves I showed that these waves can be well described as a 2-dimensional laminar flow above a turbulent layer several hundred meters thick. Being a graduate student at Caltech I used high resolution images of Jupiter taken by the Galileo orbiter to derive the distribution and optical properties of Jovian clouds (Dyudina et al., 2001). I studied simultaneous images taken at 26 different wavelengths by Galileo Near Infrared Mapping Spectrometer (NIMS) and Galileo camera. I used Principal Component Analysis (PCA), also known as the method of Empirical Orthogonal Functions, to analyze these data. PCA revealed a high correlation between the images and allowed me to create high resolution maps of cloud opacities. Another study of NIMS images taken at ~ 300 wavelengths (Irwin and Dyudina, 2001) proves the efficiency of PCA when this empirical method (my contribution to the study) is combined with the detailed radiative transfer model. In addition to filtering out most of the uncorrelated observational noise, PCA reduces the extensive computations needed for the detailed modeling and does that without loss of spatial resolution. As a result, we derived the cloud opacities and cloud particle sizes with unprecedented vertical and horizontal resolution. One of the important results of both studies (Dyudina et al., 2001;Irwin and Dyudina, 2001) is that the small-scale clouds that are usually thought to be convective penetrate the entire troposphere and are associated with large (several microns in size) particles above the tropopause. Another result is that the opacities in the middle troposphere and opacities near the tropopause are anticorrelated, suggesting that small convective clouds which exist in otherwise cloudless regions overshoot the tropopause and bring volatiles to the higher levels. Both results demonstrate a high energy associated with small-scale penetrative convection and importance of this convection for the global energy balance on Jupiter. Convective clouds are correlated with lightning flashes observed on Jupiter. With its unprecedented spatial resolution of 25 km/pixel Galileo's camera was able to resolve diffuse lightning spots on the night side of Jupiter. The brightness distribution at these spots is produced by the light scattered in the clouds above the lightning. To study lightning in these images I wrote a 3-D Monte Carlo model for the photons scattered in the clouds(Dyudina et al. 2002), which is the first model for 3-D clouds on Jupiter. Comparing the modeled lightning images to the data led me to the following conclusions. First, clouds above the lightning are not plane-parallel. Instead they resemble cumulus clouds on Earth. Therefore the storm clouds cannot be described by the well-established plane-parallel radiative transfer models. Full 3-D models should be used instead. Second, the lightning is surprisingly deep, perhaps below the expected water cloud base. Also, clouds above lightning are optically thick (optical depth > 5). This is an independent restriction obtained from transmitted lightning light instead of reflected solar light used by previous researchers. All these conclusions give more evidence for the convective origin of these clouds and their crucial role in the global energy transport on Jupiter. The study of jovian lightning led me to search for spacecraft imagery of terrestrial lightning. Indeed, a large amount of lightning images have been collected since the 1997 launch of the TRMM satellite with the Lightning Imaging Sensor (LIS) onboard. Comparison with these data shows that jovian lightning is smaller and much deeper than the largest terrestrial lightning. The 30-km-long horizontal lightning which we find in terrestrial images has no analogs on Jupiter. I also studied the atmosphere of the jovian satellite Io and the Io plasma torus in collaboration with Mike Brown. For this project, I made observations with Lick observatory's Echelle Spectrograph on coude auxiliary telescope. I constructed a computer model of the torus-atmosphere interaction. The results suggest that the interaction must include more complicated physical processes than direct sputtering from either Io's surface or atmosphere. Currently at NASA GISS I am studying lightning observed by the Cassini ISS camera through the H_alpha filter. Lightning seen on the night side of Jupiter always has a corresponding convective cloud on the day side. The repeated observation of powerful lightning in the wake of the Great Red Spot shows that the storm is electrically active for at least 20 hours. This time is a substantial fraction of the 2-8 days lifetime of the convective clouds. These results confirm that lightning and the lightning-producing strong updrafts expose themselves as easily-observable bright clouds. RESEARCH PLANS Below are some projects which I am especially enthusiastic to do. I am also interested in exploring new fields and ideas and will be glad to deviate from these projects when a good science can be done other way. This is especially true for analysing new observations. Cloud/radiation feedback on extrasolar planets This project is targeted to giant planets in our and other solar systems. I plan to predict cloud distribution on the giant planets. The lowest possible level at which cloud made of a particular volatile can exist is the equilibrium condensation level. This level is reasonably well known for different cloud layers on the giant planets of our Solar system. However, the actual clouds can form anywhere above the equilibrium condensation level. Their location is largely influenced by solar heating of the atmosphere which, in turn, depends on the clouds. I propose to create a coupled model for the clouds and the atmospheric heating/cooling. The model will be based on my radiative transfer simulation(Dyudina et al. 2002) and will include different mechanisms of convective and stratus cloud formation. I plan to verify my model with visible and IR images of the giant planets as well as with the wind velocity observations. Planned for the next 5 years phase light curve observations of the extrasolar planets will allow me to retrieve the clouds on these planets my model. Correlation analysis of multiwavelength images Principal component analysis (PCA) is a very efficient way to filter out noise from multiple images of the same object (Dyudina et al., 2001). When images in different wavelengths are interpreted with some model, PCA summarizes the data and reduces the computaional time by orders of magnitude (Irwin and Dyudina, 2001). I believe that PCA is a very efficient tool for data reduction, especially for large data arrays. I am eager to apply PCA to a wide range of imaging data, from astronomical to terrestrial spacecraft imaging. Combining Jovian data from different instruments for direct cloud retrieval Large number of high-resolution (25 to 300 km/pixel) multi-wavelength images of Jovian clouds is collected by the HST and spacecraft (Voyagers, Galileo, Cassini). Many of these observations were aimed to derive vertical distribution of the clouds. However, the conclusions from different observations are quite controversial even regarding the location of the main cloud deck. This is mainly because different observations are often taken at different times, in different parts of spectra, and at different geometries. When considered independently, these observations can only provide a robust restriction for the upper clouds but not for the optically thick tropospheric clouds. I propose to combine high-resolution observations taken by different instruments and to perform a cloud retrieval consistent with all of the observations. To do this I plan to perform extensive correlation analysis on the data and create a cloud retrieval model based on my Monte Carlo radiative transfer simulation. The retrieval is expected to restrict the cloud distribution better than the single-instrument studies because many independent observations will be brought together. Modeling of light scattering in broken clouds Thunder cloud clusters are believed to be one of the main mechanisms of radiative balance on Jupiter, which makes the cloud structure a key to understanding weather on Jupiter. These cloud clusters resemble a forest of individual cloud towers(Dyudina et al. 2002). In this geometry the cloud coverage cannot be treated in classical for Jovian models way, i. e., as plane-parallel cloud layers. I propose to model these broken clouds with my 3D radiative transfer simulation. I will verify the modeled scattering phase functions, spectra and visible-to-IR images with the observations. I hope to restrict such model parameters as spacing of the cloud towers, opacities of the clouds and the ``cloud-clear'' gaps between them. These results would lead to understanding convective energies, precipitation, and composition of the clouds. Teaching interests At both Moscow University and Caltech I have completed broad coursework in mathematics, physics, computer science, atmospheric science, planetary physics, space physics, geology , and geophysics. At Caltech I have assisted teaching courses on introductory and advanced Planetary Science, Global Environmental Science, and Geology. In addition to my research, it would be exciting for me to have an opportunity to teach planetary or atmospheric physics, or other related couses.