Approved for public release, distribution is unlimited / Vertically propagating waves (VPWs) generated by prominent mountain ridges are a severe hazard to military aircraft operations. Properly forecasting the initiation and duration of such a phenomenon is critical, yet quite often missed by turbulence forecasters. A primary reason for poor forecast skill is vague VPW forecasting guidelines at the Air Force operational centers, focusing a majority of attention on the less severe, more common trapped lee wave response. The United States Air Forces in Europe Operational Weather Squadron (USAFE OWS) has requested a tool to aid in improving forecast ability of VPW events. Satellite analysis from October 2003 through March 2004 indicated an occurrence of six major VPW events to the lee of the Alps. Actual verification of turbulence in each VPW was unavailable due to the minimal pilot report (PIREP) database kept for military flights over Europe, therefore, a subjective assessment of turbulent conditions was determined depending on the resulting cloud signature. Using NCEP GFS model analysis and upstream upper air soundings during these events, an average synoptic condition and critical weather parameters were created. These developed tools were then tested from October 2004 through March 2005 to prove their reliability. In a limited data set these tools identified all VPW events, with only a 25% false alarm rate. This is compared to a 6% forecast ability with 0% false alarm rate determined during the 2003-2004 winter season by USAFE OWS forecasters. These new rules should be valuable in that they will provide a much needed capability for synoptic scale turbulence forecasters to better determine hazardous aviation conditions associated with VPWs. / Captain, United States Air Force

Data are presented from an automatic weather station on the Brintnell-Bologna Icefield that operated from August 2014 to August 2016 in Nahanni National Park Reserve. This location is notable for being the northernmost mass balance alpine study location of the federal government’s glaciology program (NRCan/GSC). The link between atmospheric forcing at the synoptic scale and response at the glacier surface has been shown to be strongly dependent on continentality and latitude. In this region, however, many aspects of the physical processes controlling the interaction between atmospheric forcing and snowpack response are virtually unknown, especially at the daily to hourly timescale. The character of snowfalls during the accumulation seasons for this icefield are investigated using high resolution time series from two acoustic snow depth sensors and other relevant meteorological parameters. It is found that the most drastic changes in snow depth occur from infrequent large snowfalls. Using an adaption of an Environment Canada snow depth algorithm, snowfall events are identified and their timing is quantified based on a system of thresholds, running averages and ratios between the snow depth sensors. Synoptic conditions are examined using meteorological reanalysis data and trajectory analysis to determine the moisture origin and pathway. / Graduate

No description available.

Thesis (M.Sc.)(Meteorology)--University of Pretoria, 2007. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1980. / Microfiche copy available in Archives and Science. / Bibliography: leaf 134. / by Geoffrey Shepherd Domm. / M.S.

The aim of this thesis is to understand spatiotemporal temperature variability in southern South America by identifying overarching temperature variability states and their associated synoptic-scale meteorological patterns. Further, the temporal frequency of occurrence of those temperature variability states is investigated as is the role of recurrent low-frequency modes of climate variability (El Niño Southern Oscillation and the Southern Annular Mode) on temperature variability. K-means cluster analysis is used to group all months during the period 1980-2015 into four primary categories for summer and winter separately. Monthly maps of temperature anomalies are provided as input to the k-means algorithm and the resulting temperature variability states are the composites of temperature anomaly maps for months assigned to each cluster, illustrating the primary spatial patterns of temperature variability over Southern South America. Composites of synoptic-scale meteorological patterns (wind, geopotential height, and moisture fields) are calculated for months assigned to each cluster to better diagnose the driving meteorology associated with these patterns of temperature variability. Results show that in summer surface wind direction and geopotential height are robust indicators of temperature variability patterns, while in winter jet stream winds are important for diagnosing equatorward excursions of cold air and poleward excursions of warm air. According to the results the El Niño Southern Oscillation and the Southern Annular Mode exhibit some relationship with temperature variability state frequency, with some states more associated with these two modes than others, however they do not appear to be primary drivers of any of the temperature variability states.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Meteorology and Physical Oceanography, 1982. / Microfiche copy available in Archives and Science. / Bibliography: leaves 159-163. / by Brian Bennett Reinhold. / Ph.D.

The statistical analysis of the daily maximum winds was accomplished for the city of Maceió and for the days with wind starting from strong Breeze. The analysis synoptic was elaborated with objective of identifying the patterns of the circulation atmospheric associates to the strong wind. For that it was used data of wind of Maceió-Al's Airport, for the period of 2003-2006. For the analysis synoptic data of reanalysis of the global model were used NCEP / NCAR and images of satellites in the infrared channel. The maximum daily wind had the largest frequency during the day and it presented a sazonalidade, where the most intense winds were in the spring stations and summer. The variation interanual of the wind presented smaller magnitude values for the anomalies trimestrais of the temperature of the surface of the larger (El Niño) sea. They were found four patterns presented in agreement with the order of the found frequencies. In the standard I and II the front systems are located in the areas southeast and south with a dug in Brazilian northeast (NEB). In the Pattern III there is a front prolongation in the northeast area. In the Pattern IV no there is any front system and the strong wind was associated with the development of the intense convection in the area. With the objective of facilitating the operational meteorology a software was created with synoptic focus. The software allows the obtaining of the products generated by the numeric model ETA and groups of the fields for better identification and attendance of the systems synoptic. A page was developed in code HTML to turn more I practice the visualization of those fields. And knowing about the difficulty or inexistence in the obtaining of images of satellites with projection of Mercator (projection type that facilitates the analysis synoptic) grew up a bank of images of satellites with projection of Mercator and with the tops more colds of the enhanced clouds. / Foi realizada a análise estatística dos ventos máximos diários para a cidade de Maceió e para os dias com vento a partir de Brisa forte. A análise sinótica foi elaborada com objetivo de identificar os padrões da circulação atmosférica associados ao vento forte. Para isso utilizou-se dados de vento do Aeroporto de Maceió-AL, para o período de 2003-2006. Para a análise sinótica foram utilizados dados de reanálise do modelo global NCEP/NCAR e imagens de satélites no canal infravermelho. O vento máximo diário teve a maior frequência durante o dia e apresentou uma sazonalidade, onde os ventos mais intensos foram nas estações de primavera e verão. A variação interanual do vento apresentou valores de magnitude menores para as anomalias trimestrais da temperatura da superfície do mar maiores (El Niño). Foram encontrados quatro padrões apresentados de acordo com a ordem das frequências encontradas. Nos Padrões I e II os sistemas frontais estão localizados nas regiões sudeste e sul com um cavado no Nordeste Brasileiro (NEB). No Padrão III há um prolongamento frontal na região nordeste. No Padrão IV não há nenhum sistema frontal e o vento forte foi associado com o desenvolvimento da convecção intensa na região. Com o objetivo de facilitar a meteorologia operacional foi criado um software com enfoque de sinótica. O software permite a obtenção dos produtos gerados pelo modelo numérico ETA e conjuntos dos campos para melhor identificação e acompanhamento dos sistemas sinóticos. Foi desenvolvida uma página em código HTML para tornar mais pratico a visualização desses campos. E sabendo da dificuldade ou inexistência na obtenção de imagens de satélites com projeção de Mercator (tipo de projeção que facilita a análise sinótica) criou-se um banco de imagens de satélites com projeção de Mercator e com os topos mais frios das nuvens realçadas.

The connection between Upper Tropospheric Cyclonic Vortex (UTCV) and Brazilian Northeast Jet Stream (BNEJS) was analyzed for 9 years between 1988 and 2000, separated by El Niño, La Niña and Neutral years. Through the reanalysis products from NCEP, and METEOSAT satellite images in the infrared channel, were observed 167 UTCVs, most of them originated over the Atlantic Ocean with an average last of 4 days and showed no significant variability in years of El Niño and La Niña. Approximately 54% of the observed UTCVs were associated to air currents superior than 20m.s-1 in its periphery, these currents are called BNEJS. In El Niño years was observed an increase of BNEJS cases associated to UTCV, while in La Niña years, the number of occurrences was practically the same as in neutral years. The BNEJS showed intensitity up to 40 m.s-1, and the most observed wind directions were from south, southeast, northwest and west. Thus, 3 patterns of occurrence of BNEJS were identified, named Meridional, Zonal and Transversal. The Meridional BNEJS occurs in the UTCVs west periphery, usually over the continent, showing the upward movements between the BNEJS and the Northern Subtropical Jet Stream (NSJS). And finally, the transversal BNEJS, showed two kinds of currents, one from southeast and another from northwest. In these cases, the UTCVs axis showed an inclination to west and the upward movements were observed in the UTCVs periphery, where the winds were weaker. Thus, three cases were chosen to represent the observed patterns and investigate the vertical movements, comparing to the cloudiness in the satellite images, where was observed, in both cases, that the upward movements doesn t exists or are too weak in the jet streak BNEJS area. / Conselho Nacional de Desenvolvimento Científico e Tecnológico / A ligação entre Vórtice Ciclônico em Altos Níveis (VCAN) e a Corrente de Jato do Nordeste Brasileiro (CJNEB), foi analisada durante 9 anos entre 1988-2000, divididos em períodos de El Niño, La Niña e Neutro. Através dos produtos de reanálise do NCEP, e imagens do satélite METEOSAT no canal infravermelho, foram observados 167 VCAN s, em grande maioria originados sobre o oceano Atlântico, com uma duração média de 4 dias, não apresentando variabilidade significativa em anos de El Niño e La Niña. Dos VCAN s observados, aproximadamente 54%, estavam associados a correntes de ar superiores a 20m.s-1 em sua periferia, essas correntes são chamadas de CJNEB. Em anos de El Niño, foi observado um aumento dos casos de CJNEB associados à VCAN, enquanto que em anos de La Niña, o número de ocorrências foi praticamente o mesmo que em anos neutros. As CJNEB apresentaram intensidade de até 40 m.s-1, e as direções mais observadas foram de sul, sudeste, noroeste e oeste. Assim, foram identificados 3 padrões de ocorrência de CJNEB, denominadas de Meridional, Zonal e Transversal. A CJNEB Meridional ocorre na periferia oeste do VCAN, geralmente sobre o continente, apresentando os movimentos ascendentes no lado oeste da corrente. A CJNEB Zonal ocorreu sobre a periferia norte do VCAN, apresentando movimentos ascendentes entre a CJNEB e o Jato Subtropical do Hemisfério Norte (JSTHN). E finalmente, a CJNEB Transversal, que apresentou dois tipos de correntes, uma de sudeste e outra de noroeste. Nesses casos, o eixo do VCAN apresentou uma inclinação para oeste, e os movimentos ascendentes foram observados na periferia do VCAN, onde os ventos foram mais fracos. Assim, três casos foram escolhidos a fim de representar os padrões observados e investigar os movimentos verticais, comparando com a nebulosidade nas imagens de satélites, onde foi observado em ambos os casos, que os movimentos ascendentes inexistem ou são muito fracos na região mais intensa da CJNEB ( Jet Streak ).

The objective of this work is to identify the factors that favors the movement of frontal systems over South America (SA) and their influences in the state of Alagoas (AL), Brazil and determine the synoptic patterns characteristic of the penetration events of fronts into the Tropics, besides testing new diagnostic tools to describe these systems and others. Twenty six frontal systems that direct or indirectly influenced the weather conditions over AL for the 2004 2006 period were analyzed. The cases were sorted out in four groups (G) according to the similar characteristics among the events. They were: G1 passage of the frontal system or its extremity over AL; G2 cloud band over AL, organized by the frontal tip over the Southern Tropical Atlantic (STA); G3 convective activity over AL, due to the frontal tip over STA and G4 passage of the frontal system or its tip over STA at the same latitude of the AL coast. The fronts were identified using different methods: classical, satellite imagery, equivalent potential temperature (θe) fields and advection of equivalent potential temperature (Aθe). The global model NCEP/NCAR Reanalysis data and infra-red images were used. In general, the fronts that reach AL are not associated with friagem events. The G1 events were found in all seasons of the year. The G2 cases were concentrated during Southern Hemisphere (SH) winter and onset of the transition to warmer months. The G3 events occur during the end of the transition to warmer months, SH summer and onset of the transition to colder months. No event fell in G4. The superposition of several factors is important to characterize the frontal influences in AL: frontal regeneration ahead of the main front, development of secondary fronts and possible instantaneous occlusion, interaction of the analyzed frontal with other frontal waves, interaction of the frontal tip with cyclonic perturbations over the continent (of baraclinic nature during winter months and of barotropic nature during summer months) and jet stream positioned to the north of its climatological position. The fronts responsible for convecdtive activity over AL, from November to March, are associated with the interaction of the Southern America Convergence Zone and one Upper Air Cyclonic Vortex. The presence of warm cored barotropic high pressure over SA inhibits the development of the frontal tip over the Brazilian coast during the winter months. The coupling between the upper air wave train of synoptic scale (identified by the meridional flux linking the exit of Polar Jet Stream to the entrance of the Subtropical Jet Stream) allows the merging of different frontal waves in low levels and the incursion of cold air equatorward, being responsible for the frontal regeneration and the formation of new cyclones in the family. The θe and Aθe fields are sufficient for the analyses and identification of the frontal systems, and should be part of an operational weather forecast suite. Based on these fields a conceptual model for the development of baroclinic cyclone in the Tropics is presented. / Fundação de Amparo a Pesquisa do Estado de Alagoas / Este trabalho teve o objetivo de identificar os fatores que favorecem o deslocamento dos sistemas frontais sobre a América do Sul (AS) e suas influências sobre o Estado de Alagoas (AL). Procurou-se encontrar padrões sinóticos que expliquem os mecanismos e processos atmosféricos que comandam o deslocamento das frentes para regiões tropicais, além de testar novas ferramentas que possibilitem a melhor identificação dos sistemas envolvidos nesses processos. Assim, foi feita a analise de 26 sistemas frontais que influenciaram direta ou indiretamente as condições de tempo sobre o Estado de AL, para três anos (2004 a 2006). Os casos foram divididos em 4 grupos (G), de acordo com as características similares encontradas entre os eventos. G1 - passagem do sistema frontal, ou de sua extremidade, sobre o estado de AL; G2 - banda de nebulosidade sobre o Estado de AL, organizada pela extremidade frontal sobre o Atlântico Tropical Sul (ATS); G3 atividades convectivas sobre o Estado de AL, organizadas pela extremidade frontal sobre o ATS e G4 - passagem do sistema frontal, ou de sua extremidade, sobre o ATS, na mesma latitude da costa alagoana. As frentes foram identificadas por diversos métodos: sinótico clássico, dados de satélite e campos horizontais de temperatura potencial equivalente (θe) e advecção de temperatura potencial equivalente (Aθe). Foram utilizados dados de reanálise do modelo global NCEP/NCAR e imagens de satélite no canal infravermelho. Em geral, as frentes que chegaram até AL não estiveram associadas a eventos de friagem . Os eventos do G1foram encontrados em todas as estações do ano. Os casos do G2 se concentraram durante as estações de inverno austral e inicio da transição quente. Os eventos do G3 tenderam a ocorrer durante o fim da transição quente, verão austral e início da transição fria. Não houve eventos que satisfizessem as condições do G4. A sobreposição de vários fatores se torna importantes para as influências frontais em AL: regenerações frontais, novas ciclogêneses na frente principal, surgimento de frentes secundárias e possíveis oclusões instantâneas, interação da onda frontal analisada com outras ondas frontais, interação da extremidade frontal com perturbações ciclônicas sobre o continente (baroclínica nos meses de inverno e barotropica no verão) e corrente de jato posicionada ao norte da sua climatologia. De novembro a março, as frentes que organizaram atividades convectivas sobre AL estiveram associadas à interação da ZCAS e VCAN s. A atuação de uma Alta Barotrópica de Núcleo Quente sobre a AS oferece restrição para o desenvolvimento da extremidade frontal na costa do Brasil, durante os meses de inverno. O acoplamento entre os trens de onda de escala sinótica em altos níveis, identificado por um fluxo meridional que conecta a saída da Corrente de Jato Polar com a entrada da Corrente de Jato Subtropical, permite a fusão de ondas frontais distintas em baixos níveis e a incursão de ar frio em direção ao equador, podendo provocar a regeneração das frentes e a formação de novos ciclones na família. Os campos de θe e Aθe são eficientes para analise e identificação de sistemas frontais, devendo ser incorporados a previsão operacional do tempo. Com base nesses campos, foi proposto o modelo conceitual de desenvolvimento do ciclone baroclínico na região tropical.