Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN. / Includes bibliographical references. / by Joel Berman. / M.S.

Approved for public release, distribution is unlimited / A study of the performance of the Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS) was performed based on collected METOC properties affecting radar propagation during the Roughness and Evaporation Duct (RED) experiment conducted off the windward coast of Oahu, HI. The measured refractivity influencing parameters (SST, air temperature, humidity, and wind speed) were compared to COAMPS predicted values. Using the NPS bulk evaporation duct model, profiles of the modified refractivity were computed from the buoy data and compared to profiles computed from the COAMPS data. The profiles were obtained concurrently with S-Band propagation measurements along a 26-km path. The radar propagation predictions created by APM from the modified refractivity profiles, derived from the measured METOC values and COAMPS modeled values, were compared to the in situ measured propagation losses. The mean RMS error of the prop loss predictions derived from the COAMPS forecasted METOC values was <4 dB compared to a mean RMS error of <3 dB from the in situ measurement derived prop loss predictions. Significantly larger errors occurred at the COAMPS analysis times. Overall, the results are very promising for this trade wind region, where the air is cooler than the relatively warm sea surface. / Lieutenant, United States Navy

Thesis (M.S. in Systems Engineering (Electronic Warfare))--Naval Postgraduate School, September 1990. / Thesis Advisor(s): Davidson, Kenneth L. Second Reader: Hershey, Scott H. "September 1990." Description based on title screen as viewed on December 29, 2009. Author(s) subject terms: Retractive conditions, prongation, Central America, radar, microwave. Includes bibliographical references (p. 60-61). Also available in print.

L'observation de la variabilité de l'humidité dans les basses couches de l'atmosphère peut être réalisée en passant par la mesure du paramètre thermodynamique appelé réfractivité. Les radars météorologiques peuvent mesurer les changements de réfractivité dans la couche limite de l'atmosphère en exploitant la phase des signaux de retour des cibles fixes situées aux alentours. La cartographie de ce paramètre a été mise en place à plusieurs reprises lors de campagne de mesures aux Etats-Unis et en Europe, ce qui a démontré qu'elle est maintenant possible dans un rayon de 30 km autour du radar, avec une résolution temporelle de 15 minutes et une résolution spatiale de 5 km. . Un travail de simulation fait par Besson et al. 2012, à l'origine fait pour étudier les sources d'erreur de repliement de la phase, a permis de montrer que la variabilité de la réfractivité augmente considérablement notamment pendant les après-midi et l'été. Depuis trois ans, le travail mené au LATMOS et à Météo-France a consisté à étudier la possibilité de mesurer les fluctuations à l'échelle hectométrique dans l'atmosphère en utilisant la variabilité de la réfractivité. La première étape de ce travail, basée sur un jeu de données issues des réseaux opérationnels de Météo-France (stations automatiques et radar de Trappes) a permis d'établir un lien clair entre les variabilités à 5 minutes, de la réfractivité radar, et de la réfractivité in-situ.La deuxième étape du travail a consisté à regarder la nature de ce lien à plus petite échelle pour comprendre les limites éventuelles de la mesure. Ainsi, une campagne de mesure, TeMeRAiRE (Test de la Mesure de Réfractivité Atmosphérique par Radar à l'Echelle hectométrique) a été menée durant l'été 2014 sur le site instrumenté du SIRTA. Afin de se placer en conditions contrôlées, deux radars ont été placés en visée fixe et horizontale vers 4 réflecteurs connus. L'échantillonnage temporel était de 0,25s pour BASTA et de 1,5ms pour CURIE. Des stations de mesures in-situ ont également été placées à côtés des cibles. Les premiers résultats montrent que la mesure de réfractivité, et de sa variabilité, est possible aux fréquences utilisées (bande X et bande W), ce qui constitue en soi une première. Nous avons aussi pu démontrer que la différentiation spatiale conduit à une résolution spatiale de l'ordre de 100m, et proposer une explication pour un comportement spécifique, et très localisé, de la réfractivité sur le site du SIRTA. e but est maintenant de regarder, par le biais de comparaisons entre les différents instruments, si la mesure radar de la variabilité de la réfractivité dans un volume d'atmosphère constitue effectivement une mesure locale, et si cette dernière peut donner une information sur l'état turbulent de l'atmosphère et son évolution. / Weather radars can retrieve refractivity changes based on phase variations of stationary targets. These retrievals provide valuable information of moisture in the atmospheric boundary layer along the radar path. Recent work on errors associated with these retrievals has shown that the refractivity variability is stronger during the afternoon and the summer season. This observation has led us to study further the link between the refractivity variability measured by radar and the small scales atmospheric fluctuations. First, we compared the variability of the refractivity retrieved from operational weather radars operating at C-band (5.6 GHz) to the variability of the refractivity directly measured by Automatic Weather Stations (AWS). A strong correlation between the two measurements was shown with a negative bias increasing with range from the radar. The bias is well explained when the variability signal is strong if one considers the model of a frozen turbulence transported by the wind. In winter, the measured variability was weaker and close to quantization noise of the AWS measurements, so it was more difficult to draw thesame conclusions. Overall, we were able to demonstrate qualitatively and quantitatively that the refractivity variability retrieved using the radar observations and measured by AWS stations is due to low-level coherent turbulent structures. Next, in order to obtain information at hectometre’s scales, a dedicated field campaign was conducted at SIRTA atmospheric observatory, near Paris. From June to September 2014 two radars (a 94 GHz W-band and a 9.5 GHz X-band radar) were pointing horizontally toward four corner reflectors aligned along a 700 meters line. Two wind and humidity high frequency measurement towers were deployed near the targets. Inter-comparisons between radar and in-situ refractivity measurement also showed a very good correlation. We finally demonstrated the possibility to compute radar refractivity on the path between two targets separated by 50 to 350 m and used this measure of the local variability of the refractivity to identify boundary processes linked to low level atmospheric turbulence.

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Approved for public release; distribution in unlimited. / In Littoral Warfare (LW), naval operations face a whole new range of missions and types of threats. In such situations, Electronic Warfare (EW) systems are extremely important, yet constantly challenged to perform faster and more accurate detection and recognition of potential threats. However, meteorological and oceanographic (METOC) factors can severely modify the effectiveness of EW systems, particularly against low detectable targets in warm waters. Therefore, this thesis analyzes the effects of tropical littoral environments in the expected performance of generic RF and IR systems when used under these scenarios. It analyzes the outputs of propagation models included in the software suites AREPS and TAWS when using actual data from different sources in the Yucatan Channel. The results of this study demonstrated how radically the environmental conditions can change, clearly modifying the efficiency of surveillance and detection systems in shipborne platforms. Further, several issues related to the need of valuable data and additional research are addressed, while providing useful insights to operational commanders and decision makers for the use of EW systems and available Tactical Decision Aids (TDAs) at the typical scenarios of Littoral Warfare in tropical waters. / Lieutenant Commander, Mexican Navy