Microphysical and kinematic processes associated with anomalous charge structures in isolated convection.

Microphysical and kinematic characteristics of two storm populations, based on their macroscale charge structures, are investigated in an effort to increase our understanding of the processes that lead to anomalous (or inverted charge) structures. Nine normal polarity cases (mid-level negative charge) with dual-Doppler and polarimetric coverage that occurred in northern Alabama, and six anomalous polarity cases (mid-level positive charge) that occurred in northeastern Colorado are included in this study. The results show that even though anomalous polarity storms formed in environments with similar instability, they had significantly larger and stronger updrafts. Moreover, the anomalous polarity storms evidently have more robust mixed-phase microphysics, based on a variety of metrics. Anomalous polarity storms in Colorado have much higher cloud base heights and shallower warm cloud depths in this study, leading us to hypothesize that anomalous polarity storms have lower amounts of dilution and entrainment. We infer positively charged graupel, and therefore high supercooled water contents, in the mid-levels of the anomalous storms based on the relationship between colocations of graupel and inferred positive charge from Lightning Mapping Array data. Using representative updraft speeds and warm cloud depths, the time required for a parcel to traverse from cloud base to the freezing level was estimated for each storm observation. We suggest this metric is the key discriminator between the two storm populations and leads us to hypothesize that it strongly influences the amount of supercooled water and the probability of positive charge in the midlevels, leading to an anomalous charge structure.

THE OLYMPIC MOUNTAINS EXPERIMENT (OLYMPEX).

OLYMPEX is a comprehensive field campaign to study how precipitation in Pacific storms is modified by passage over coastal mountains.

Etch-free patterning of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) for optoelectronics.

Spatial control of the conductivity of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is demonstrated through the use of ultraviolet (UV) exposure. With appropriate UV exposure, electrical characterization shows that the in-plane sheet resistance of PEDOT:PSS films is increased by 4 orders of magnitude compared to unexposed regions. Characterization of the films using Raman spectroscopy identifies a significant reduction of the inter-ring stretching modes between PEDOT monomers and a morphological shift from the quinoid to benzoid form of PEDOT. Additional analysis using Fourier transform infrared spectroscopy indicates a reduction in film doping and a decrease in C═C vibrational modes that are associated with PEDOT oligomer length. Height and phase images of these films obtained from atomic force microscopy exhibit a loss of phase segregation in the film between the PEDOT grains and PSS regions. Spectroscopic ellipsometry highlights an increase in both the real and imaginary components of the index upon UV exposure. This broad range of analysis consistently suggests that the increased resistivity can be attributed to a significant reduction in material doping caused by scission-driven decomposition of the conductive PEDOT chains. When flood exposure is combined with the use of an appropriate UV blocking mask, patterning in the conductivity of PEDOT:PSS films can be realized. In contrast to other patterning approaches, no resist development or etching is required for the electrical isolation of certain regions. To demonstrate the efficacy of this process, an organic light emitting diode was fabricated with UV-patterned PEDOT:PSS as a hole transport layer. The regions of unexposed PEDOT:PSS produced electroluminescence, whereas those exposed to UV remained unlit, enabling the realization of pixelated illumination with no removal of material.