Lidar remote sensing and co-operative observations: Processing methods and aerosol radiative transfer

This Ph.D. thesis focuses on: (i) the design and integration of a polarimetric channel for the multi-spectral Raman lidar station of the Universitat Politècnica de Catalunya (UPC), Remote Sensing, Antennas, Microwaves and Superconductivity Group (CommSensLab), (ii) the study of the temporal and spatial evolution of atmospheric aerosol optical, microphysical and radiative properties by means of active and passive remote sensing in the context of ACTRIS and Spanish National projects, and (iii) rainfall rate retrieval by means of a vertically-pointed ceilometer in the context of the Verification of the Origins of Rotation in Tornadoes Experiment Southeast (VORTEX-SE). The first goal of this Ph.D., tested on the UPC multi-spectral Raman lidar station, consists of developing a secondary optical receiving chain, installed next to the laser source. The secondary telescope, mounted in the optical chain, allows retrieving the cross-polarized return signal separately from the total-power signal, avoiding the need of a very precise characterization of the crosstalk parameters of the beam-splitters. The first experimental results, corresponding to a collection of atmospheric conditions over the city of Barcelona, are also presented. The second goal of this Ph.D. deals first with the GAME (Global Atmospheric Model) code, necessary to retrieve the aerosol radiative properties. The radiative fluxes estimated in the short-wave and long-wave spectral ranges at the bottom and the top of the atmosphere by GAME are compared to the ones retrieved by a different radiative transfer model, namely Two-Stream, in order to know the importance of the spectral parameterization of a radiative transfer code. Then, GAME code, in both configurations, is fed by means of three different datasets to evaluate the parameterization of the vertically-resolved properties and to assess the uncertainty of GAME when is tuned with input parameters from different sources. Afterwards, an evaluation of the seasonal variability of the aerosol background optical and radiative properties in the Western Mediterranean Basin (WMB) is performed by means of AERONET (Aerosol Robotic Network) sun-photometers data from two background sites, Ersa (Corsica Island, France) and Palma de Mallorca (Mallorca Island, Spain). In addition, in order to detect possible northeast-southwest gradients in the aerosol properties, a third site located at Abolrán (Alborán Island, Spain) is considered. Finally, during 15-24 June 2013 a moderate Saharan dust multi-intrusion was detected by some EARLINET/ACTRIS (Granada, Barcelona, Naples, Potenza and Serra la Nave (Italy)) and ADRIMED/ChArMEx (Cap d’en Font, (Minorca Island, Spain) and Ersa) stations. This Ph.D. uses this event to study the spatio-temporal evolution of the mineral dust properties, since the lidar stations were supported during the multi-intrusion by collocated AERONET sun-photometers and the Falcon 20 aircraft. Also the GAME code is used to estimate the aerosol radiaite effect during the Saharan dust event. Besides, air- and space-borne lidar measurements, satellite images and back-trajectories are used to confirm the multi-intrusion aspect of the event. The last goal of this Ph.D. pursues estimation of the rain rate (RR) from ceilometer measurements. In VORTEX-SE, a Vaisala CL-31 ceilometer, a S-band radar, and a disdrometer were deployed in Alabama during March-April 2016. First, rain-extinction coefficients from ceilometer attenuated backscatter measurements are derived by means of a modified form of the well-known slope-method. These coefficients are compared with the RRs measured by a collocated S-band radar and a disdrometer in order to get the RR-to-extinction models. Advanced covariance-weighted techniques are used to best assess and validate the estimated models. These models can be used to estimate the RR from the ceilometer in similar situations without need to have a collocated cooperative instrument permanently deployed.Este Ph.D. se centra en: (i) en el diseño e integración de un canal polarimétrico para la estación lidar multi espectral del grupo de teledetección, antenas, microondas y superconductividad (CommSensLab) de la Universitat Politècnica de Catalunya (UPC), (ii) en el estudio de la evolución temporal y espacial de las propiedades ópticas, microfísicas y radiativas de los aerosoles por medio de teledetección activa y pasiva en el contexto de ACTRIS y proyectos estatales, y (iii) en la recuperación de intensidad de lluvia por medio de un ceilómetro en configuración vertical en el contexto del proyecto Verification of the Origins of Rotation in Tornadoes Experiment Southeast (VORTEX-SE). El primer objetivo, realizado en la estación lidar de UPC, consiste en el desarrollo de una cadena óptica secundaria instalada junto al láser. El telescopio secundario, montado en la cadena óptica, permite recuperar la componente cross-polarized de la señal total por separado, evitando la necesidad de conocer con precisión los parámetros de los beam-splitters. Se presentan también los primeros resultados obtenidos en Barcelona durante diferentes situaciones atmosféricas. El segundo objetivo de este Ph.D. se centra en el código GAME (Global Atmospheric Model), necesario para recuperar las propiedades radiativas de los aerosoles. Los flujos radiativos estimados tanto en onda larga como en onda corta en la base y en la parte superior de la atmósfera son comparados con los estimados por otro código de transferencia radiativa, Two-Stream, para conocer la importancia de la parametrización espectral. Después, el código GAME es alimentado con 3 bases de datos diferentes para evaluar la parametrización de las propiedades resueltas en altura y conocer la incertidumbre de GAME cuando es alimentado con parámetros con diferentes orígenes. Por otro lado, se presenta una evaluación de la variabilidad estacional de las propiedades ópticas y radiativas del aerosol de fondo en la cuenca oeste mediterránea (WMB) realizada con datos de fotómetros solares de la red AERONET (Aerosol Robotic Network) situados en dos puntos considerados libres de contaminación: Ersa (isla de Córcega, Francia) y Palma de Mallorca. Además, para detectar posibles gradientes noreste-suroeste en las propiedades delos aerosoles, se considera un tercer punto ubicado en la isla de Alborán. Por último, en este Ph.D. se aprovecha una multi intrusión moderada de polvo sahariano, detectada entre los días 15 y 24 de junio de 2013 por algunas estaciones EARLINET/ACTRIS (Granada, Barcelona, Nápoles, Potenza y Serra la Nave (Italia)) y ADRIMED/ChArMEx (Cap d'en Font (Menorca) y Ersa), para estudiar la evolución espacio-temporal de las propiedades del polvo mineral, ya que las estaciones lidar estaban apoyadas durante el evento por fotómetros solares pertenecientes a la red AERONET, situados junto a las estaciones lidar, y por vuelos del Falcon 20. GAME es usado para obtener también el efecto radiativo de los aerosoles durante el evento de polvo sahariano. Para confirmar el aspecto de multi intrusión se utilizan medidas lidar tomadas a bordo de aviones y satélites, imágenes satelitales y retro trayectorias. El último objetivo del Ph.D. persigue la estimación de la RR utilizando medidas de un ceilómetro. En VORTEX-SE, se desplegaron (Alabama, marzo-abril 2016) un ceilómetro Vaisala CL-31, un radar de banda S y un disdrómetro. Se han estimado los coeficientes de extinción debida a la lluvia a partir del retorno atenuado medido por el ceilómetro, utilizando una versión modificada del método de la pendiente. Estos coeficientes se comparan con las intensidades de lluvia (RR) estimadas con el radar y el disdrómetro para obtener modelos de RR-extinción. Para validarlos se utilizan técnicas avanzadas de covarianza ponderada. Dichos modelos pueden usarse para estimar la RR con un ceilómetro, en situaciones similares, sin necesidad de tener desplegado permanentemente un instrumento cooperativo.Postprint (published version

Variability of the boundary layer over an urban continental site based on 10 years of active remote sensing observations in Warsaw

Atmospheric boundary layer height (ABLH) was observed by the CHM15k ceilometer (January 2008 to October 2013) and the PollyXT lidar (July 2013 to December 2018) over the European Aerosol Research LIdar NETwork to Establish an Aerosol Climatology (EARLINET) site at the Remote Sensing Laboratory (RS-Lab) in Warsaw, Poland. Out of a maximum number of 4017 observational days within this period, a subset of quasi-continuous measurements conducted with these instruments at the same wavelength (1064 nm) was carefully chosen. This provided a data sample of 1841 diurnal cycle ABLH observations. The ABLHs were derived from ceilometer and lidar signals using the wavelet covariance transform method (WCT), gradient method (GDT), and standard deviation method (STD). For comparisons, the rawinsondes of the World Meteorological Organization (WMO 12374 site in Legionowo, 25 km distance to the RS-Lab) were used. The ABLHs derived from rawinsondes by the skew-T-log-p method and the bulk Richardson (bulk-Ri) method had a linear correlation coefficient (R2) of 0.9 and standard deviation (SD) of 0.32 km. A comparison of the ABLHs obtained for different methods and instruments indicated a relatively good agreement. The ABLHs estimated from the rawinsondes with the bulk-Ri method had the highest correlations, R2 of 0.80 and 0.70 with the ABLHs determined using the WCT method on ceilometer and lidar signals, respectively. The three methods applied to the simultaneous, collocated lidar, and ceilometer observations (July to October 2013) showed good agreement, especially for the WCT method (R2 of 0.94, SD of 0.19 km). A scaling threshold-based algorithm was proposed to homogenize ceilometer and lidar datasets, which were applied on the lidar data, and significantly improved the coherence of the results (R2 of 0.98, SD of 0.11 km). The difference of ABLH between clear-sky and cloudy conditions was on average below 230 m for the ceilometer and below 70 m for the lidar retrievals. The statistical analysis of the long-term observations indicated that the monthly mean ABLHs varied throughout the year between 0.6 and 1.8 km. The seasonal mean ABLH was of 1.16 ± 0.16 km in spring, 1.34 ± 0.15 km in summer, 0.99 ± 0.11 km in autumn, and 0.73 ± 0.08 km in winter. In spring and summer, the daytime and nighttime ABLHs appeared mainly in a frequency distribution range of 0.6 to 1.0 km. In winter, the distribution was common between 0.2 and 0.6 km. In autumn, it was relatively balanced between 0.2 and 1.2 km. The annual mean ABLHs maintained between 0.77 and 1.16 km, whereby the mean heights of the well-mixed, residual, and nocturnal layer were 1.14 ± 0.11, 1.27 ± 0.09, and 0.71 ± 0.06 km, respectively (for clear-sky conditions). For the whole observation period, the ABLHs below 1 km constituted more than 60% of the retrievals. A strong seasonal change of the monthly mean ABLH diurnal cycle was evident; a mild weakly defined autumn diurnal cycle, followed by a somewhat flat winter diurnal cycle, then a sharp transition to a spring diurnal cycle, and a high bell-like summer diurnal cycle. A prolonged summertime was manifested by the September cycle being more similar to the summer than autumn cycles

Lidar remote sensing and co-operative observations: Processing methods and aerosol radiative transfer

This Ph.D. thesis focuses on: (i) the design and integration of a polarimetric channel for the multi-spectral Raman lidar station of the Universitat Politècnica de Catalunya (UPC), Remote Sensing, Antennas, Microwaves and Superconductivity Group (CommSensLab), (ii) the study of the temporal and spatial evolution of atmospheric aerosol optical, microphysical and radiative properties by means of active and passive remote sensing in the context of ACTRIS and Spanish National projects, and (iii) rainfall rate retrieval by means of a vertically-pointed ceilometer in the context of the Verification of the Origins of Rotation in Tornadoes Experiment Southeast (VORTEX-SE). The first goal of this Ph.D., tested on the UPC multi-spectral Raman lidar station, consists of developing a secondary optical receiving chain, installed next to the laser source. The secondary telescope, mounted in the optical chain, allows retrieving the cross-polarized return signal separately from the total-power signal, avoiding the need of a very precise characterization of the crosstalk parameters of the beam-splitters. The first experimental results, corresponding to a collection of atmospheric conditions over the city of Barcelona, are also presented. The second goal of this Ph.D. deals first with the GAME (Global Atmospheric Model) code, necessary to retrieve the aerosol radiative properties. The radiative fluxes estimated in the short-wave and long-wave spectral ranges at the bottom and the top of the atmosphere by GAME are compared to the ones retrieved by a different radiative transfer model, namely Two-Stream, in order to know the importance of the spectral parameterization of a radiative transfer code. Then, GAME code, in both configurations, is fed by means of three different datasets to evaluate the parameterization of the vertically-resolved properties and to assess the uncertainty of GAME when is tuned with input parameters from different sources. Afterwards, an evaluation of the seasonal variability of the aerosol background optical and radiative properties in the Western Mediterranean Basin (WMB) is performed by means of AERONET (Aerosol Robotic Network) sun-photometers data from two background sites, Ersa (Corsica Island, France) and Palma de Mallorca (Mallorca Island, Spain). In addition, in order to detect possible northeast-southwest gradients in the aerosol properties, a third site located at Abolrán (Alborán Island, Spain) is considered. Finally, during 15-24 June 2013 a moderate Saharan dust multi-intrusion was detected by some EARLINET/ACTRIS (Granada, Barcelona, Naples, Potenza and Serra la Nave (Italy)) and ADRIMED/ChArMEx (Cap d’en Font, (Minorca Island, Spain) and Ersa) stations. This Ph.D. uses this event to study the spatio-temporal evolution of the mineral dust properties, since the lidar stations were supported during the multi-intrusion by collocated AERONET sun-photometers and the Falcon 20 aircraft. Also the GAME code is used to estimate the aerosol radiaite effect during the Saharan dust event. Besides, air- and space-borne lidar measurements, satellite images and back-trajectories are used to confirm the multi-intrusion aspect of the event. The last goal of this Ph.D. pursues estimation of the rain rate (RR) from ceilometer measurements. In VORTEX-SE, a Vaisala CL-31 ceilometer, a S-band radar, and a disdrometer were deployed in Alabama during March-April 2016. First, rain-extinction coefficients from ceilometer attenuated backscatter measurements are derived by means of a modified form of the well-known slope-method. These coefficients are compared with the RRs measured by a collocated S-band radar and a disdrometer in order to get the RR-to-extinction models. Advanced covariance-weighted techniques are used to best assess and validate the estimated models. These models can be used to estimate the RR from the ceilometer in similar situations without need to have a collocated cooperative instrument permanently deployed.Este Ph.D. se centra en: (i) en el diseño e integración de un canal polarimétrico para la estación lidar multi espectral del grupo de teledetección, antenas, microondas y superconductividad (CommSensLab) de la Universitat Politècnica de Catalunya (UPC), (ii) en el estudio de la evolución temporal y espacial de las propiedades ópticas, microfísicas y radiativas de los aerosoles por medio de teledetección activa y pasiva en el contexto de ACTRIS y proyectos estatales, y (iii) en la recuperación de intensidad de lluvia por medio de un ceilómetro en configuración vertical en el contexto del proyecto Verification of the Origins of Rotation in Tornadoes Experiment Southeast (VORTEX-SE). El primer objetivo, realizado en la estación lidar de UPC, consiste en el desarrollo de una cadena óptica secundaria instalada junto al láser. El telescopio secundario, montado en la cadena óptica, permite recuperar la componente cross-polarized de la señal total por separado, evitando la necesidad de conocer con precisión los parámetros de los beam-splitters. Se presentan también los primeros resultados obtenidos en Barcelona durante diferentes situaciones atmosféricas. El segundo objetivo de este Ph.D. se centra en el código GAME (Global Atmospheric Model), necesario para recuperar las propiedades radiativas de los aerosoles. Los flujos radiativos estimados tanto en onda larga como en onda corta en la base y en la parte superior de la atmósfera son comparados con los estimados por otro código de transferencia radiativa, Two-Stream, para conocer la importancia de la parametrización espectral. Después, el código GAME es alimentado con 3 bases de datos diferentes para evaluar la parametrización de las propiedades resueltas en altura y conocer la incertidumbre de GAME cuando es alimentado con parámetros con diferentes orígenes. Por otro lado, se presenta una evaluación de la variabilidad estacional de las propiedades ópticas y radiativas del aerosol de fondo en la cuenca oeste mediterránea (WMB) realizada con datos de fotómetros solares de la red AERONET (Aerosol Robotic Network) situados en dos puntos considerados libres de contaminación: Ersa (isla de Córcega, Francia) y Palma de Mallorca. Además, para detectar posibles gradientes noreste-suroeste en las propiedades delos aerosoles, se considera un tercer punto ubicado en la isla de Alborán. Por último, en este Ph.D. se aprovecha una multi intrusión moderada de polvo sahariano, detectada entre los días 15 y 24 de junio de 2013 por algunas estaciones EARLINET/ACTRIS (Granada, Barcelona, Nápoles, Potenza y Serra la Nave (Italia)) y ADRIMED/ChArMEx (Cap d'en Font (Menorca) y Ersa), para estudiar la evolución espacio-temporal de las propiedades del polvo mineral, ya que las estaciones lidar estaban apoyadas durante el evento por fotómetros solares pertenecientes a la red AERONET, situados junto a las estaciones lidar, y por vuelos del Falcon 20. GAME es usado para obtener también el efecto radiativo de los aerosoles durante el evento de polvo sahariano. Para confirmar el aspecto de multi intrusión se utilizan medidas lidar tomadas a bordo de aviones y satélites, imágenes satelitales y retro trayectorias. El último objetivo del Ph.D. persigue la estimación de la RR utilizando medidas de un ceilómetro. En VORTEX-SE, se desplegaron (Alabama, marzo-abril 2016) un ceilómetro Vaisala CL-31, un radar de banda S y un disdrómetro. Se han estimado los coeficientes de extinción debida a la lluvia a partir del retorno atenuado medido por el ceilómetro, utilizando una versión modificada del método de la pendiente. Estos coeficientes se comparan con las intensidades de lluvia (RR) estimadas con el radar y el disdrómetro para obtener modelos de RR-extinción. Para validarlos se utilizan técnicas avanzadas de covarianza ponderada. Dichos modelos pueden usarse para estimar la RR con un ceilómetro, en situaciones similares, sin necesidad de tener desplegado permanentemente un instrumento cooperativo

Processament de perfils de precipitació obtinguts amb radar Doppler

[cat] En la actualitat les dades obtingudes amb instruments de teledetecció (mesures obtingudes a distància) formen una part essencial en l’àmbit de la meteorologia. Aquestes dades s’obtenen amb diversos sensors de tipus passiu (com els radiòmetres) o actiu (com els radars meteorològics) instal·lats a la superfície terrestre, en avions o en satèl·lits. Els radars meteorològics destinats a observar precipitació operen típicament en longituds d’ona de 3 a 10 cm (bandes X, C i S), realitzen escombrats d’antena en el pla horitzontal i proporcionen una valuosa informació del camp de precipitació en un radi de l’ordre de 100 km, de gran importància en la vigilància i predicció meteorològica a curt termini. La seva posta a punt i manteniment té associat un cost no negligible. També existeixen radars perfiladors, amb antena fixa apuntant el zenit, que proporcionen perfils verticals de precipitació amb gran resolució temporal i espacial. Aquests equips sovint són portables i més econòmics, i permeten realitzar estudis dels processos microfísics que donen lloc a la precipitació, complementant la informació dels radars meteorològics tradicionals. Aquesta tesi es centra en el processament d’observacions de radars perfiladors, concretament en dos tipus d’equips diferents que mitjançant l’efecte Doppler, poden observar la velocitat terminal de caiguda de les partícules de precipitació. La tesi s’estructura en tres blocs i es presenta com a compendi de quatre articles científics. El primer i segon bloc de la tesi es dediquen al perfilador Doppler conegut com Micro Rain Rada, que opera en banda K (longitud d’ona de 1.2 cm) i permet observar precipitació. Al primer bloc es proposa un processament de les dades brutes (reflectivitat espectral) del MRR que contempla diferents algoritmes per detectar pics meteorològics en el senyal, reducció del soroll, i diverses millores per detectar de forma robusta moviments ascendents. A partir d’aquest processament inicial es calculen diversos paràmetres derivats, que permeten estudiar la banda de fusió o “banda brillant” amb una metodologia innovadora. Es presenta un estudi concret, aplicat a un MRR instal·lat a la Facultat de Física de la Universitat de Barcelona al costat de l’estació de radiosondatge del Servei Meteorològic de Catalunya, que s’utilitza com a referència per a la caracterització de la banda brillant. La segona part és un altre estudi aplicat a observacions de MRR durant la campanya Cerdanya-2017 on es proposa una nova metodologia per a classificar diferents tipus de precipitació (com ara pluja, plugim, neu o calamarsa). La metodologia es verifica amb observacions independents de disdròmetre, model Parsivel, (instal·lat al costat del MRR), que proporciona una classificació automàtica de tipus de precipitació. El tercer i darrer bloc de la tesi es centra en el processament d’observacions d’un perfilador de vent Doppler polsat de banda UHF (longitud d’ona d’uns 20 cm), model PCL1300 del fabricant francès Degreane. L’equip està configurat per a funcionar amb cinc feixos per a optimitzar l’estimació de perfils de vent (components horitzontal i vertical). En aquest cas, com en els altres dos blocs anteriors, també es proposa un processat de les dades brutes, però atenent la freqüència de treball, l’equip detecta tant moviments de l’aire com la presència de partícules de precipitació. El processament, a banda d’obtenir el perfil de vent, també és capaç de detectar la precipitació i estimar el tipus de precipitació. Es presenta un estudi amb observacions d’un PCL1300 de Météo- France durant la campanya Cerdanya-2017, on també s’usen dades de MRR i disdròmetre (Parsivel) per a contrastar la nova metodologia proposada. El resultat de cada bloc abordat en aquesta tesis és un programari d’accés lliure, disponible al repositori GitHub, perquè la comunitat científica pugui reutilitzar-lo fàcilment en estudis posteriors.[eng] The first and second blocks of the thesis are devoted to the frequency modulated continuous wave (FMCW) vertically pointing Doppler radar profiler known as Micro Rain Radar from the German manufacturer Metek, which operates in K-band (wavelength of 1.2 cm) and allows precipitation observation. The first block proposes a processing of the raw data (spectral reflectivity) of the MRR that includes different algorithms to detect meteorological peaks in the signal, noise reduction, and several improvements to robustly detect upward movements of the air. From this initial processing, several derived parameters are calculated, which allow the study of the melting band or "bright band" with an innovative methodology. A specific study is presented, applied to a MRR installed at the Faculty of Physics of the University of Barcelona next to the radiosounding station of the Meteorological Service of Catalonia, which is used as a reference for the characterisation of the bright band. The second block is another study applied to MRR observations during the Cerdanya-2017 campaign. The third and last block of the thesis focuses on the processing of observations from a UHF- band pulsed Doppler wind profiler (wavelength about 20 cm), model PCL1300 from the French manufacturer Degreane. The equipment is configured to operate with five beams to optimise the estimation of wind profiles (horizontal and vertical components). In this case, as in the other two previous blocks, processing of the raw data is also proposed, but taking into account the operating frequency, the equipment detects both air movements and the presence of precipitation. The processing, in addition to obtaining the wind profile, is also capable of detecting precipitation and estimating the type of precipitation. A study with observations from a PCL1300 wind profiler of Météo-France, during the Cerdagne-2017 campaign is presented, where MRR and disdrometer (Parsivel) data are also used to validate the new proposed methodology and also it has been used to validate the methodology in the first and second block. The result of each block addressed in this thesis is an open access software, available in the GitHub repository

Remote Sensing of Precipitation: Volume 2

Precipitation is a well-recognized pillar in global water and energy balances. An accurate and timely understanding of its characteristics at the global, regional, and local scales is indispensable for a clearer understanding of the mechanisms underlying the Earth’s atmosphere–ocean complex system. Precipitation is one of the elements that is documented to be greatly affected by climate change. In its various forms, precipitation comprises a primary source of freshwater, which is vital for the sustainability of almost all human activities. Its socio-economic significance is fundamental in managing this natural resource effectively, in applications ranging from irrigation to industrial and household usage. Remote sensing of precipitation is pursued through a broad spectrum of continuously enriched and upgraded instrumentation, embracing sensors which can be ground-based (e.g., weather radars), satellite-borne (e.g., passive or active space-borne sensors), underwater (e.g., hydrophones), aerial, or ship-borne

Lower Atmosphere Meteorology

The Atmosphere Special Issue “Lower Atmosphere Meteorology” deals with the meteorological processes that occur in the layer of the atmosphere close to the surface. The interaction between the biosphere and the atmosphere is made through the lower layer and can greatly influence living beings and materials. The analysis of the meteorological parameters provides a better understanding of processes within the lower atmosphere and involved in air pollution, climate, and weather. The mixed layer height, the wind speed, and the air parcel trajectory have a relevant interest due to their marked impact on population and energy production. The research also comprises aerosols, clouds, and precipitation, analysing their spatiotemporal variations. This issue addresses features of gases in the atmosphere and anthropogenic greenhouse emission estimates, which are also conditioned by the lower atmosphere meteorology

Atmospheric Research 2016 Technical Highlights

Atmospheric research in the Earth Sciences Division (610) consists of research and technology development programs dedicated to advancing knowledge and understanding of the atmosphere and its interaction with the climate of Earth. The Divisions goals are to improve understanding of the dynamics and physical properties of precipitation, clouds, and aerosols; atmospheric chemistry, including the role of natural and anthropogenic trace species on the ozone balance in the stratosphere and the troposphere; and radiative properties of Earth's atmosphere and the influence of solar variability on the Earth's climate. Major research activities are carried out in the Mesoscale Atmospheric Processes Laboratory, the Climate and Radiation Laboratory, the Atmospheric Chemistry and Dynamics Laboratory, and the Wallops Field Support Office. The overall scope of the research covers an end-to-end process, starting with the identification of scientific problems, leading to observation requirements for remote-sensing platforms, technology and retrieval algorithm development; followed by flight projects and satellite missions; and eventually, resulting in data processing, analyses of measurements, and dissemination from flight projects and missions. Instrument scientists conceive, design, develop, and implement ultraviolet, infrared, optical, radar, laser, and lidar technology to remotely sense the atmosphere. Members of the various laboratories conduct field measurements for satellite sensor calibration and data validation, and carry out numerous modeling activities. These modeling activities include climate model simulations, modeling the chemistry and transport of trace species on regional-to-global scales, cloud resolving models, and developing the next-generation Earth system models. Satellite missions, field campaigns, peer-reviewed publications, and successful proposals are essential at every stage of the research process to meeting our goals and maintaining leadership of the Earth Sciences Division in atmospheric science research. Figure 1.1 shows the 22-year record of peer-reviewed publications and proposals among the various laboratories

Large scale dynamics of the atmosphere: Planetary waves

Planetary waves (PW) are global scale waves in the atmosphere, which are known to considerably impact weather patterns in the midlatitudes in the troposphere and the ozone distribution in the stratosphere. PW play an important role in coupling middle atmosphere dynamics. Due to the fact that climate change causes a decrease of the meridional temperature gradient, the strength of the zonal wind might decrease. This should, in turn, change the planetary wave activity (PWA). In order to quantify possible changes in the PWA we analyze ERA–Interim temperature data (10 m to 65 km height) on the Northern Hemisphere and calculate the so-called dynamical activity index (DAI) as measure for the PWA. We analyze the PWA to find indications for PWA changes and variability. We also use rotational temperature data from hydroxyl airglow measurements at UFS Schneefernerhaus (Germany) embedded in the international Network for the Detection of Mesospheric Change (NDMC) in the upper mesosphere/lower thermosphere (UMLT). We find an indication for a significant increase of the PWA in the stratosphere. The change of the PWA with higher zonal wavenumbers turns out to be strongest. This finding is in agreement with the expectation that a weakening of the meridional temperature gradient leads to improved vertical propagation conditions for planetary waves. With the empirical mode decomposition (EMD) we are able to extract non-stationary signals of the PWA time series. We further find that longer-term oscillations (QBO, ENSO and solar cycles) have a noticeable impact on the PW variability in all considered heights. Next to the 11-year cycle that is related to the sunspot-cycle in many studies, we also find a pronounced quasi-22-year signal. We tentatively interpret this signal as being due to the solar-magnetic-field (“Hale cycle”)