INTRUSION OF RECENT AIR IN POLAR STRATOSPHERE DURING SUMMER 2009 REVEALED BY BALLOON-BORNE IN SITU CO MEASUREMENTS

International audienceThe SPIRALE (Spectroscopie Infa-Rouge par Absorption de Lasers Embarqués) balloon-borne instrument has been launched twice within 17 days in the polar region (Kiruna, Sweden, 67.9°N-21.1°E) during summer, at the beginning and at the end of August 2009. In situ measurements of several trace gases have been performed including CO and O 3 between 10 and 34 km height, with very high vertical resolution (~5 m). The both flight results are compared and the CO stratospheric profile of the first flight presents specific structures associated with mid-latitude intrusion in the lowest stratospheric levels. Their interpretation is made with the help of results from several modeling tools (MIMOSA and FLEXTRA) and available satellite data (IASI). We also used the O 3 profile correlated with CO to calculate the proportion of recent air in the polar stratosphere. The results indicate the impact of East Asia urban pollution on the chemistry of polar stratosphere in summer

Tailored algorithms for the detection of the atmospheric boundary layer height from common automatic lidars and ceilometers (ALC)

A detailed understanding of atmospheric boundary layer (ABL) processes is key to improve forecasting of pollution dispersion and cloud dynamics in the context of future climate scenarios. International networks of automatic lidars and ceilometers (ALC) are gathering valuable data that allow for the height of the ABL and its sublayers to be derived in near real time. A new generation of advanced methods to automatically detect the ABL heights now exist. However, diversity in ALC models means these algorithms need to be tailored to instrument-specific capabilities. Here, the advanced algorithm STRATfinder is presented for application to high signal-to-noise ratio (SNR) ALC observations, and results are compared to an automatic algorithm designed for low-SNR measurements (CABAM). The two algorithms are evaluated for application in an operational network setting. Results indicate that the ABL heights derived from low-SNR ALC have increased uncertainty during daytime deep convection, while high-SNR observations can have slightly reduced capabilities in detecting shallow nocturnal layers. Agreement between the ALC-based methods is similar when either is compared to the ABL heights derived from temperature profile data. The two independent methods describe very similar average diurnal and seasonal variations. Hence, high-quality products of ABL heights may soon become possible at national and continental scales

Deconvolution-Based Structured Light System with Geometrically Plausible Regularization

This paper presents a new deconvolution-based energy formulation for segmenting the image of stripe-based patterns projected by structured light systems. Our framework features an explicit modeling of the blurring introduced by the lens of a structured light system. This allows a significant improvement when working out of focus, a situation which occurs when performing depth measurement. The proposed iterative algorithm includes two steps: a deconvolution and a segmentation. For both steps, a geometrically plausible regularization term is used. It considers the projected displacement induced by the camera, projector and scene configuration. We validate our method using real imagery acquired using off-the-shelf equipment.Le pr\ue9sent document propose une nouvelle formulation \ue9nerg\ue9tique bas\ue9e sur la d\ue9convolution visant \ue0 segmenter l'image form\ue9e par des bandes lumineuses projet\ue9es par des syst\ue8mes lumineux structur\ue9s. Notre m\ue9thode comporte une mod\ue9lisation explicite du flou cr\ue9\ue9 par la lentille d'un syst\ue8me lumineux structur\ue9. Elle permet d'am\ue9liorer l'image obtenue lorsque l'on travaille hors foyer, situation qui se produit lorsque l'on effectue des mesures de la profondeur de champ. L'algorithme it\ue9ratif propos\ue9 comprend deux \ue9tapes : d\ue9convolution et segmentation. Dans les deux \ue9tapes, une restauration g\ue9om\ue9triquement plausible est effectu\ue9e. Elle tient compte du d\ue9placement projet\ue9 induit par la cam\ue9ra, le projecteur et la configuration de la sc\ue8ne. Nous validons notre m\ue9thode en ayant recours \ue0 l'imagerie en temps r\ue9el obtenue avec de l'\ue9quipement commercial.NRC publication: Ye

Abstract Non-Uniform Hierarchical Pyramid Stereo for Large Images

This paper addresses the stereo correspondence problem where the images are large enough to make stereo matching difficult. In order to reduce the problem size, we propose a new non-uniform hierarchical scheme with the ability to handle different coarseness levels simultaneously. Our framework, based on a maximum flow formulation, allows a much better localization of object boundaries where large depth discontinuities are present. The uniform decomposition fails to localize precisely such borders because it makes the assumption that surfaces are smooth in order to correct the errors from one coarseness level to the next. Our disparity estimation accurately localizes large depth discontinuities and then focus on increasing the resolution of smooth surfaces. Results on synthetic and real images demonstrate the validity of our framework.

Active 3D imaging systems

Active 3D imaging systems use artificial illumination in order to capture and record digital representations of objects. The use of artificial illumination allows the acquisition of dense and accurate range images of textureless objects that are difficult to acquire using passive vision systems. An active 3D imaging system can be based on different measurement principles that include time-of-flight, triangulation and interferometry. While time-of-flight and interferometry systems are briefly discussed, an in-depth description of triangulation-based systems is provided. The characterization of triangulation-based systems is discussed using both an error propagation framework and experimental protocols.Peer reviewed: YesNRC publication: Ye