Physical Sciences and Mathematics Commons^™

Probing The Structure Of Water On Surfaces: From Water Absorption To Ice Nucleation, Jiarun Zhou

All Dissertations

Water, essential for all life forms, is the most abundant, simple, yet mysterious molecule in the world. This molecule, consisting of only three atoms, behaves in unexpectedly different ways with the change of environment. In the past, studies of water under different conditions (temperature, pressure, on the surfaces, with confinement) have been conducted using experimental and computational methods. However, the influence of a given environment on water properties is yet to be fully understood. This dissertation studies water at complex interfaces (surfaces with various chemistry and physics properties) in both the liquid and crystalline states. Various heterogeneous systems used to …

The Influence Of Particle Concentration And Bulk Characteristics On Polarized Oceanographic Lidar Measurements, Brian L. Collister, Richard C. Zimmerman, Charles I. Sukenik, William M. Balch, Victoria J. Hill

OES Faculty Publications

Oceanographic lidar measurements of the linear depolarization ratio, δ, contain information on the bulk characteristics of marine particles that could improve our ability to study ocean biogeochemistry. However, a scarcity of information on the polarized light-scattering properties of marine particles and the lack of a framework for separating single and multiple scattering effects on δ have hindered the development of polarization-based retrievals of bulk particle properties. To address these knowledge gaps, we made single scattering measurements of δ for several compositionally and morphologically distinct marine particle assemblages. We then used a bio-optical model to explore the influence of multiple …

The Role Of Boundary-Parallel Vertical Wind Shear In Convection Initiation, Alexander J. Krull

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Convection initiation (CI) remains a forecasting challenge for meteorologists. CI frequently occurs within the vicinity of some airmass boundary or density current. Airmass boundaries are favored areas of convergence, thus associated forced ascent facilitates CI. Features such as misocyclones often develop along the leading edge of airmass boundaries, favoring updraft formation and prompting alterations to the horizontal and vertical flow near the boundary. Airmass boundary characteristics and CI potential have been found to be sensitive to the environmental vertical wind shear. This affects propagation speed, convergence, and thus forced ascent along the leading edge. Previous studies have focused primarily on …

The Simulated Impact Of Snow Cover And Soil Moisture On Convective Precipitation Within The Rocky Mountains Under Climate Warming, Brendan Charles Wallace

Legacy Theses & Dissertations (2009 - 2024)

Warm season moist diurnal convection can be particularly sensitive to changes in land surface

Aerosol Direct Radiative And Cloud Adjustment Effects On Surface Climate Over The Eastern China : Analyses Of Wrf Model Simulations, Yangyang Song

Legacy Theses & Dissertations (2009 - 2024)

Aerosol climate effects consist of the initial forcing of atmospheric radiation perturbation through both the direct radiative effect and the modulation of radiatively-important cloud microphysics, and the subsequent changes in meteorology that also affect cloud macro- and micro-physics. The aerosol-induced cloud adjustment therefore involves many couplings and interactions, and its quantitative evaluation requires the use of model simulations. This study uses WRF model simulated changes in clouds and meteorology due to anthropogenic aerosol increases (versus 1970s) for 2002−2008 summers over the eastern China to address two relevant issues: direct radiative vs. cloud adjustment effects, and their roles in affecting surface …

Investigation Of Microphysical Properties Of Laboratory And Atmospheric Clouds Using Digital In-Line Holography, Neel Desai

Dissertations, Master's Theses and Master's Reports

In this study, we attempt to perform in-cloud measurements, both in the laboratory using the Michigan Tech $\Pi$-chamber and in the atmosphere via the CSET field campaign. Atmospheric turbulence is believed to play a critical role in the growth, development and dissipation of clouds and it is important to study its effect in order to better understand and predict cloud properties such as albedo and lifetime. We use digital in-line holography to measure the effect of turbulence on cloud microphysical properties such as variations in droplet number concentration and droplet or ice particle size. In the first half, we study …

Sensitivity Of Conus Summer Rainfall To The Selection Of Cumulus Parameterization Schemes In Nu-Wrf Seasonal Simulations, Takamichi Iguchi, Wei-Kuo Tao, Di Wu, Christa D. Peters-Lidard, Joseph A. Santanello, Eric Kemp, Yudong Tian, Jonathan Case, Weile Wang, Robert Ferraro, Duane E. Waliser, Jinwon Kim, Huikyo Lee, Bin Guan, Baijun Tian, Paul C. Loikith

Geography Faculty Publications and Presentations

This study investigates the sensitivity of daily rainfall rates in regional seasonal simulations over the contiguous United States (CONUS) to different cumulus parameterization schemes. Daily rainfall fields were simulated at 24-km resolution using the NASA-Unified Weather Research and Forecasting (NU-WRF) Model for June–August 2000. Four cumulus parameterization schemes and two options for shallow cumulus components in a specific scheme were tested. The spread in the domain-mean rainfall rates across the parameterization schemes was generally consistent between the entire CONUS and most subregions. The selection of the shallow cumulus component in a specific scheme had more impact than that of the …

The Role Of Sulfur Dioxide In Stratospheric Aerosol Formation Evaluated By Using In Situ Measurements In The Tropical Lower Stratosphere, A. W. Rollins, T. D. Thornberry, L. A. Watts, P. Yu, K. H. Rosenlof, M. Mills, E. Baumann, F. R. Giorgetta, T. V. Bui, M. Höpfner, P. F. Bernath

Chemistry & Biochemistry Faculty Publications

Stratospheric aerosols (SAs) are a variable component of the Earth's albedo that may be intentionally enhanced in the future to offset greenhouse gases (geoengineering). The role of tropospheric-sourced sulfur dioxide (SO₂) in maintaining background SAs has been debated for decades without in situ measurements of SO₂ at the tropical tropopause to inform this issue. Here we clarify the role of SO₂ in maintaining SAs by using new in situ SO₂ measurements to evaluate climate models and satellite retrievals. We then use the observed tropical tropopause SO₂ mixing ratios to estimate the global flux of …

Cirrus Cloud Microphysics Over Darwin, Australia, Dorothea Ivanova, Matthew Johnson

Publications

Ice clouds, crucial to the understanding of both short - and long - term climate trends, are poorly represented in global climate models (GCMs). Cirrus clouds, one of the largest uncertainties in the global radiation budget, have been inadequately studied at low latitudes. Parameterizations exist for mid - latitude and tropical cirrus ( Ivanova et al. 2001; McFarquhar et al. 1997). Due to climate sensitivity in the GCM with respect to cloud input, without robust parameterizations of cirrus clouds, the GCM is inaccurate over most output fields, including radiative forcing, temperature, albedo, and heat flux (Yao and Del Genio 1999). …

Determination And Analysis Of Dscovr-Eipc Satellite-Retrieved Radiance From Cloud Geometric And Optical Properties, Emily Christine Morgan

Legacy Theses & Dissertations (2009 - 2024)

Using simulations and numerical fitting, this work sought to describe the satellite-retrieved radiance of clouds as a function of their thermodynamic and optical properties. Subsequently, this understanding can then be used in a look-up-table to determine the properties of clouds imaged by the EPIC sensor in the NASA DSCOVR satellite. In this study, background oxygen absorption was modeled in a radiative transfer model and convolved with EPIC filter functions for two absorption-reference pairs for Oxygen A- and B-band. This absorption profile was established as the primary vertical coordinate in this study, leveraging the similarity principle to allow for intercomparison of …

Understanding The Dependence Of Radiative Feedbacks And Clouds On The Spatial Structure Of Ocean Heat Uptake, Lance Rayborn

Legacy Theses & Dissertations (2009 - 2024)

Ocean heat uptake and radiative forcing are important for understanding transient climate change. Differences in efficacy of ocean heat uptake (suppression of surface warming per unit energy flux into the deep oceans relative to CO2 forcing) account for a substantial fraction of the spread in transient warming between models. Rose et al. (2014) studied the dependence of efficacy on the spatial pattern of ocean heat uptake in an ensemble of aquaplanet simulations with prescribed ocean heat uptake, and found large differences in model responses to high versus low latitude uptake. This study accurately quantifies these model responses through the use …

Characterization Of Tropical Clouds Using Multi-Satellite Observations, Ricardo Anderson

Dissertations and Theses

Clouds an important component of the earth-climate system and play a critical role in affecting energy and water cycle of the planet. In particular, tropical convective clouds account for the majority of the precipitation that fall on the Earth's surface. Multiple active satellite missions in recent decade such as TRMM (Tropical Rainfall Measurement Mission), and CloudSat have provided fruitful new insight into the internal structures of these tropical convective clouds. In conjunction with cloud data from ISCCP (International Satellite Cloud Climatology Project), that is based passive remote sensing technology in the visible and infrared spectrum, this allows for a more …

Technical Note: Swift - A Fast Semi-Empirical Model For Polar Stratospheric Ozone Loss, M. Rex, S. Kremser, P. Huck, G. Bodeker, I. Wohltmann, M. L. Santee, P. F. Bernath

Chemistry & Biochemistry Faculty Publications

An extremely fast model to estimate the degree of stratospheric ozone depletion during polar winters is described. It is based on a set of coupled differential equations that simulate the seasonal evolution of vortex-averaged hydrogen chloride (HCl), nitric acid (HNO3), chlorine nitrate (ClONO₂), active forms of chlorine (ClO_x = Cl+ClO+2ClOOCl) and ozone (O₃) on isentropic levels within the polar vortices. Terms in these equations account for the chemical and physical processes driving the time rate of change of these species. Eight empirical fit coefficients associated with these terms are derived by iteratively fitting the equations …

Solar Radiation Measurements And Their Applications In Climate Research, Bangsheng Yin

Legacy Theses & Dissertations (2009 - 2024)

Aerosols and clouds play important roles in the climate system through their radiative effects and their vital link in the hydrological cycle. Accurate measurements of aerosol and cloud optical and microphysical properties are crucial for the study of climate and climate change. This study develops/improves retrieval algorithms for aerosol single scattering albedo (SSA) and low liquid water path (LWP) cloud optical properties, evaluates a new spectrometer, and applies long-term measurements to establish climatology of aerosol and cloud optical properties. The following results were obtained.

Process-Evaluation Of Tropospheric Humidity Simulated By General Circulation Models Using Water Vapor Isotopic Observations: 2. Using Isotopic Diagnostics To Understand The Mid And Upper Tropospheric Moist Bias In The Tropics And Subtropics, Camille Risi, David Noone, John Worden, Christian Frankenberg, Gabriele Stiller, Michael Kiefer, Bernd Funke, Kaley Walker, Peter Bernath, Matthias Schneider, Sandrine Bony, Jeonghoon Lee, Derek Brown, Christophe Sturm

Chemistry & Biochemistry Faculty Publications

Evaluating the representation of processes controlling tropical and subtropical tropospheric relative humidity (RH) in atmospheric general circulation models (GCMs) is crucial to assess the credibility of predicted climate changes. GCMs have long exhibited a moist bias in the tropical and subtropical mid and upper troposphere, which could be due to the mis-representation of cloud processes or of the large-scale circulation, or to excessive diffusion during water vapor transport. The goal of this study is to use observations of the water vapor isotopic ratio to understand the cause of this bias. We compare the three-dimensional distribution of the water vapor isotopic …

Remote Sensing Of Cloud Properties Using Oxygen A-Band Spectral Measurements, Siwei Li

Legacy Theses & Dissertations (2009 - 2024)

Clouds play an important role in the climate system through their radiative effects and their vital link in the hydrological cycle. Detailed knowledge of the three dimensional (3-D) distribution of cloud macrophysical and microphysical properties is crucial to properly characterize radiative forcing by clouds and to quantify the response of the climate. In this study, a multi-layer cloud detection algorithm is developed by utilizing photon path length distributions retrieved from oxygen A-band spectral measurements. Case studies from measurements at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site demonstrate that this photon path length method can detect multi-layer clouds …

Process-Evaluation Of Tropospheric Humidity Simulated By General Circulation Models Using Water Vapor Isotopologues: 1. Comparison Between Models And Observations, Camille Risi, David Noone, John Worden, Christian Frankenberg, Gabriele Stiller, Michael Kiefer, Bernd Funke, Kaley Walker, Peter Bernath, Matthias Schneider, Debra Wunch, Vanessa Sherlock, Nicholas Deutscher, David Griffith, Paul O. Wennberg, Kimberly Strong, Dan Smale, Emmanuel Mahieu, Sabine Barthlott, Frank Hase, Omaira García, Justus Notholt, Thorsten Warneke, Geoffrey Toon, David Sayres, Sandrine Bony, Jeonghoon Lee, Derek Brown, Ryu Uemura, Christophe Sturm

Chemistry & Biochemistry Faculty Publications

The goal of this study is to determine how H₂O and HDO measurements in water vapor can be used to detect and diagnose biases in the representation of processes controlling tropospheric humidity in atmospheric general circulation models (GCMs). We analyze a large number of isotopic data sets (four satellite, sixteen ground-based remote-sensing, five surface in situ and three aircraft data sets) that are sensitive to different altitudes throughout the free troposphere. Despite significant differences between data sets, we identify some observed HDO/H₂O characteristics that are robust across data sets and that can be used to evaluate …

Research Poster: An Overview Of Progress In Nsf Epscor Project Entitled, “Reducing Cloud Uncertainties In Climate Models”, Subhashree Mishra, David L. Mitchell, W. Patrick Arnott

2010 Annual Nevada NSF EPSCoR Climate Change Conference

Research poster

Influences Of Winter Haze On Fog/Low Cloud Over The Indo-Gangetic Plains, Ritesh Gautam, N. C. Hsu, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

The aerosol loading in south Asia has increased considerably because of the growing population, urbanization, and industrialization in recent years. To understand the effects of aerosols on cloud properties in this region, we have analyzed an extensive collection of aerosol and cloud properties, obtained from the Moderate resolution Imaging Spectroradiometer (MODIS) data, over the Indian subcontinent during winter 2000–2006. During these winter months, the Indo-Gangetic (IG) plains, in the northern part of India, are subjected to dense haze and fog on the basis of MODIS climatology of aerosol optical depth and cloud properties (cloud effective radius, cloud top pressure, and …

Consistency Based Error Evaluation For Deep Sea Bathymetric Mapping With Robotic Vehicles, Christopher Roman, Hanumant Singh

Christopher N. Roman

This paper presents a method to evaluate the mapping error present in point cloud terrain maps created using robotic vehicles and range sensors. This work focuses on mapping environments where no a priori ground truth is available and self consistency is the only available check against false artifacts and errors. The proposed error measure is based on a disparity measurement between common sections of the environment that have been imaged multiple times. This disparity measure highlights inconsistency in the terrain map by showing regions where multiple overlapping point clouds do not fit together well. This error measure provides the map …

Evolution Of Cloud-To-Ground Lightning Discharges In Tornadic Thunderstorms, Wendy L. Seaman

Theses and Dissertations

Air Force operations are directly impacted by weather on a daily basis. Erroneous forecasts negatively impact mission readiness and consequently cost the government time, in terms of wasted man-hours, and money. Advanced forecast lead-time could make a difference to minimize loss to both USAF personnel and assets. This study examined lightning data from 64 storm events from 1995-2000 in search of unique lightning signatures indicative of tornadic activity. Overall flash rates, percentage of positive flashes, positive and negative peak currents and multiplicity for each case were separated into two categories based on tornado intensity and season of occurrence. Based on …

Analysis Of Cloud-Free Line-Of-Sight Probability Calculations, Joseph J. Golemboski Iii

Theses and Dissertations

Cloud-free line-of-sight probabilities were calculated using two separate methods. The first was a variation of a method developed by the Rand Corporation in 1972. In it, CFLOS probabilities were calculated using empirical data based on five years of photograms taken over Columbia, Missouri and forecasted cloud amounts rather than climatological values. The second was a new approach using the Cloud Scene Simulation Model developed by Phillips Laboratory. Cloud scenes were generated using forecasted cloud fields, meteorological inputs, and thirty random numbers. Water content files were produced and processed through a follow-on program to determine the extinction coefficients at each grid …

Development Of Predictors For Cloud-To-Ground Lightning Activity Using Atmospheric Stability Indices, Kenneth C. Venzke

Theses and Dissertations

A detailed examination was performed on several commonly applied atmospheric stability indices and lightning activity from 1993 to 2000 to determine the indices usefulness as predictive tools for determining cloud-to-ground lightning activity. Predetermined radii of 50 nautical miles around upper-air stations in the Midwest U.S. were used for the lightning summaries. Also explored is an improvement upon the commonly accepted thresholds of the stability indices as general thunderstorm indicators. An improvement was found and new threshold ranges were developed for relating stability index values to lightning occurrence. Traditional statistical regression methods failed to find a significant predictive relationship. By examining …

Experimental Goes Sounder Products For The Assessment Of Downburst Potential, Gary P. Ellrod, James P. Nelson Iii, Michael R. Witiw, Lynda Bottos, William P. Roeder

Aeronautics Faculty Publications

Several experimental products derived from Geostationary Operational Environmental Satellite (GOES) Sounder retrievals (vertical profiles of temperature and moisture) have been developed to assist weather forecasters in assessing the potential for convective downbursts. The product suite currently includes the wind index (WINDEX), a dry microburst index, and the maximum difference in equivalent potential temperature (θe) from the surface to 300 hPa. The products are displayed as color-coded boxes or numerical values, superimposed on GOES visible, infrared, or water vapor imagery, and are available hourly, day and night, via the Internet. After two full summers of evaluation, the products have been shown …

A Validation Study Of The Ssm/I Temperature Algorithm And Comparison With The Cal/Val Land Surface Temperatures, Ronald L. Comoglio

Theses and Dissertations

The USAF operational cloud model, the Real-Time Nephanalysis (RTNEPH), requires infrared and visual scene scans as well as input from the Special Sensor Microwave Imager (SSM/I), featured on the Defense Meteorological Satellite Program (DMSP) polar orbiters. Additionally, SSM/I provides input to the Air Force Global Weather Center (AFGWC) surface temperature model (SFCTMP). The global surface temperatures are required for identifying which pixel of a scene is cloud and which is ground and as a first guess input to initialize NWP models. The SSM/I provides brightness temperatures sampled at four discrete: frequencies and dual polarizations to produce surface temperatures. Two algorithms …

An Alternative Representation Of The Ice Canopy For Calculating Microwave Brightness Temperatures Over A Thunderstorm, Bradley M. Muller, Henry E. Fuelberg, Eric A. Smith

Publications

Passive microwave brightness temperatures (T(B)'s) at 92 and 183 GHz from an aircraft thunderstorm overflight are compared with values calculated from radar-derived hydrometeor profiles and a modified proximity sounding. Two methods for modeling particles in the ice canopy are contrasted. The first is a ''traditional'' approach employing Marshall-Palmer ice spheres. The second, or ''alternative,'' method partitions 20% of the ice water content into a Marshall-Palmer component for graupel and hail, and 80% into a modified gamma spherical particle size distribution function representing ice crystals.

Results from the alternative approach are superior to those from the traditional method in the anvil …