Polarimetric Retrievals of Cloud Droplet Number Concentration: Towards a Better Understanding of Aerosol-Cloud Interactions

A longstanding source of uncertainty within the climate system is our understanding of clouds and their response to aerosols. The resulting cloud optical property changes constitute the largest uncertainty in our understanding of 20th century climate change. Central to being able to monitor and better understand the effects aerosols composition, size and concentration have on cloud reflectivity are accurate observations of the cloud droplet number concentration. Cloud droplet number concentrations couple aerosol properties to changes in cloud brightness. In the first portion of this dissertation, I present the development and evaluation of two techniques for observing cloud properties. The first is a new method of observing cloud droplet number concentration that uses polarimetric measurements and requires relatively few assumptions. The theoretical derivation is first presented followed by a method of implementation using NASA’s airborne Research Scanning Polarimeter (RSP). I use data obtained during the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES). Comparing cloud droplet number concentration retrievals with in situ measurements made by a cloud droplet probe during NAAMES shows strong agreement between measurements over a range of meteorological conditions and cloud types. Multilayered clouds are ubiquitous within Earth’s atmosphere, yet detecting their presence and height has been a longstanding challenge for passive remote sensing instruments. Retrieving the cloud top height is also an important part of the droplet concentration retrieval, and detecting the presence of multilayered clouds supports interpreting results. For this second technique, I present an assessment of RSP cloud top height retrievals, which are based on the concept of parallax. By comparing RSP cloud top height retrievals to the Cloud Physics Lidar (CPL), the technique is found to be capable of determining the presence and heights of up to three cloud layers, which is innovative for a passive remote sensing instrument. A second element essential to addressing the uncertainty in cloud’s response to aerosols is to better understand processes and drivers of cloud properties. Air-campaign studies offer opportunities to study high temporal and spatial resolution measurements that are needed to better understand the complex processes between aerosols, clouds and meteorological properties. My final investigation uses the two developed cloud property retrievals, in conjunction with other in situ and remotely sensed data, to undertake a broad investigation quantifying connections observed between aerosols, clouds and meteorology. I find a well- defined link between cloud microphysical property changes and marine biogenic aerosol concentrations. Changes in cloud properties are consistent with the Twomey effect, whereby an increase in cloud condensation nuclei is associated with increases in droplet concentrations and decreased droplet sizes. I also observe complex, non-linear secondary effects of aerosols on clouds such as cloud thinning and decreased droplet distribution width. I conclude this study by integrating my findings and discussing plausible linkages between aerosol, cloud and meteorological properties within the context of existing concepts

Laboratory for Atmospheres: Instrument Systems Report

Studies of the atmospheres of our solar system's planets including our own require a comprehensive set of observations, relying on instruments on spacecraft, aircraft, balloons, and on the surface. Laboratory personnel define requirements, conceive concepts, and develop instrument systems for spaceflight missions, and for balloon, aircraft, and ground-based observations. Laboratory scientists also participate in the design of data processing algorithms, calibration techniques, and data processing systems. The instrument sections of this report are organized by measurement technique: lidar, passive, in situ and microwave. A number of instruments in various stages of development or modification are also described. This report will be updated as instruments evolve

Multi-View Polarimetric Scattering Cloud Tomography and Retrieval of Droplet Size

Tomography aims to recover a three-dimensional (3D) density map of a medium or an object. In medical imaging, it is extensively used for diagnostics via X-ray computed tomography (CT). We define and derive a tomography of cloud droplet distributions via passive remote sensing. We use multi-view polarimetric images to fit a 3D polarized radiative transfer (RT) forward model. Our motivation is 3D volumetric probing of vertically-developed convectively-driven clouds that are ill-served by current methods in operational passive remote sensing. Current techniques are based on strictly 1D RT modeling and applied to a single cloudy pixel, where cloud geometry defaults to that of a plane-parallel slab. Incident unpolarized sunlight, once scattered by cloud-droplets, changes its polarization state according to droplet size. Therefore, polarimetric measurements in the rainbow and glory angular regions can be used to infer the droplet size distribution. This work defines and derives a framework for a full 3D tomography of cloud droplets for both their mass concentration in space and their distribution across a range of sizes. This 3D retrieval of key microphysical properties is made tractable by our novel approach that involves a restructuring and differentiation of an open-source polarized 3D RT code to accommodate a special two-step optimization technique. Physically-realistic synthetic clouds are used to demonstrate the methodology with rigorous uncertainty quantification

Laboratory for Atmospheres: 2006 Technical Highlights

The 2006 Technical Highlights describes the efforts of all members of the Laboratory for Atmospheres. Their dedication to advancing Earth science through conducting research, developing and running models, designing instruments, managing projects, running field campaigns, and numerous other activities, are highlighted in this report

Pre-Aerosol, Clouds, and Ocean Ecosystem (PACE) Mission Science Definition Team Report

We live in an era in which increasing climate variability is having measurable impact on marine ecosystems within our own lifespans. At the same time, an ever-growing human population requires increased access to and use of marine resources. To understand and be better prepared to respond to these challenges, we must expand our capabilities to investigate and monitor ecological and bio geo chemical processes in the oceans. In response to this imperative, the National Aeronautics and Space Administration (NASA) conceived the Pre-Aerosol, Clouds, and ocean Ecosystem (PACE) mission to provide new information for understanding the living ocean and for improving forecasts of Earth System variability. The PACE mission will achieve these objectives by making global ocean color measurements that are essential for understanding the carbon cycle and its inter-relationship with climate change, and by expanding our understanding about ocean ecology and biogeochemistry. PACE measurements will also extend ocean climate data records collected since the 1990s to document changes in the function of aquatic ecosystems as they respond to human activities and natural processes over short and long periods of time. These measurements are pivotal for differentiating natural variability from anthropogenic climate change effects and for understanding the interactions between these processes and various human uses of the ocean. PACE ocean science goals and measurement capabilities greatly exceed those of our heritage ocean color sensors, and are needed to address the many outstanding science questions developed by the oceanographic community over the past 40 years

Investigation of Warm Convective Cloud Fields with Meteosat Observations and High Resolution Models

Die hohe raumzeitliche Variabilität von konvektiven Wolken hat erhebliche Auswirkungen auf die Quantifizierung des Wolkenstrahlungseffektes. Da konvektive Wolken in atmosphärischen Modellen üblicherweise parametrisiert werden müssen, sind Beobachtungsdaten notwendig, um deren Variabilität sowie Modellunsicherheiten zu quantifizieren. Das Ziel der vorliegenden Dissertation ist die Charakterisierung der raumzeitlichen Variabilität von warmen konvektiven Wolkenfeldern mithilfe von Meteosat Beobachtungen sowie deren Anwendbarkeit für die Modellevaluierung. Verschiedene Metriken wurden untersucht, um Unsicherheiten in Modell- und Satellitendaten sowie ihre Limitierungen zu quantifizieren. Mithilfe des hochaufgelösten sichtbaren (HRV) Kanals von Meteosat wurde eine Wolkenmaske entwickelt, welche mit 1×2 km² die Auflösung der operationellen Wolkenmaske von 3×6 km² deutlich übertrifft. Diese ermöglicht eine verbesserte Charakterisierung von kleinskaligen Wolken und bietet eine wichtige Grundlage für die Weiterentwicklung von satellitengestützten Wolkenalgorithmen. Für die Untersuchung der Lebenszyklen konvektiver Wolkenfelder wurde ein Tracking-Algorithmus entwickelt. Die raumzeitliche Entwicklung des Flüssigwasserpfads (LWP) wurde sowohl in einer Eulerschen Betrachtungsweise als auch entlang Lagrange’scher Trajektorien analysiert. Für die Wolkenfelder ergab sich eine charakteristische Längenskala von 7 km. Als Maß für die Wolkenlebenszeit ergab sich eine Lagrange’sche Dekorrelationszeit von 31 min. Unter Berücksichtigung des HRV Kanals verringern sich die Dekorrelationsskalen signifikant, was auf eine Sensitivität gegenüber der räumlichen Auflösung hindeutet. Für eine Quantifizierung dieser Sensitivität wurden Simulationen des ICON-LEM Modells mit einer Auflösung von bis zu 156 m berücksichtigt. Verbunden mit einem zwei- bis vierfach geringeren konvektiven Bedeckungsgrad besitzen die simulierten Wolken bei dieser hohen Auflösung deutlich größere LWP Werte. Diese Unterschiede verschwinden im Wesentlichen, wenn die simulierten Wolkenfelder auf die optische Auflösung von Meteosat gemittelt werden. Die Verteilungen der Wolkengrößen zeigen einen deutlichen Abfall für Größen unterhalb der 8- bis 10-fachen Modellauflösung, was der effektive Auflösung des Modells entspricht. Dies impliziert, dass eine noch höhere Auflösung wünschenswert wäre, damit mit ICON-LEM Wolkenprozesse unterhalb der 1 km-Skala realistisch simuliert werden können. Diese Skala wird zukünftig erfreulicherweise vom Meteosat der dritten Generation abgedeckt. Dies wird ein entscheidender Schritt für ein verbessertes Verständnis von kleinskaligen Wolkeneffekten sowie für die Parametrisierung von Konvektion in NWP und Klimamodellen sein

Deep Space Gateway Concept Science Workshop : February 27–March 1, 2018, Denver, Colorado

The purpose of this workshop is to discuss what science could be leveraged from a deep space gateway, as well as first-order determination of what instruments are required to acquire the scientific data.Institutional Support, National Aeronautics and Space Administration, Lunar and Planetary Institute, Universities Space Research Association ; Executive Committee, Ben Bussey, HEOMD Chief Scientist, NASA Headquarters, Jim Garvin, Goddard Space Flight Center Chief Scientist, Michael New, NASA Headquarters, Deputy AA for Research, SMD, Paul Niles, Executive Secretary, NASA Johnson Space Center, Jim Spann, MSFC Chief Scientist, Eileen Stansbery, Johnson Space CenterPARTIAL CONTENTS: Deep Space Gateway as a Deployment Staging Platform and Communication Hub of Lunar Heat Flow Experiment--Lunar Seismology Enabled by a Deep Space Gateway--In-Situ Measurements of Electrostatic Dust Transport on the Lunar Surface--Science Investigations Enabled by Magnetic Field Measurements on the Lunar Surface--Enhancing Return from Lunar Surface Missions via the Deep Space Gateway--Deep Space Gateway Support of Lunar Surface Ops and Tele-Operational Transfer of Surface Assets to the Next Landing Site--Development of a Lunar Surface Architecture Using the Deep Space Gateway--The Deep Space Gateway: The Next Stepping Stone to Mar

Remote Sensing of Earth Resources: A literature survey with indexes (1970 - 1973 supplement). Section 1: Abstracts

Abstracts of reports, articles, and other documents introduced into the NASA scientific and technical information system between March 1970 and December 1973 are presented in the following areas: agriculture and forestry, environmental changes and cultural resources, geodesy and cartography, geology and mineral resources, oceanography and marine resources, hydrology and water management, data processing and distribution systems, instrumentation and sensors, and economic analysis