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- All Subjects: Meteorology
- All Subjects: urban planning
- Creators: Huang, Huei-Ping
- Creators: Brazel, Anthony
- Status: Published
Description
While there are many elements to consider when determining one's risk of heat or cold stress, acclimation could prove to be an important factor to consider. Individuals who are participating in more strenuous activities, while being at a lower risk, will still feel the impacts of acclimation to an extreme climate. To evaluate acclimation in strenuous conditions, I collected finishing times from six different marathon races: the New York City Marathon (New York City, New York), Equinox Marathon (Fairbanks, Alaska), California International Marathon (Sacramento, California), LIVESTRONG Austin Marathon (Austin, Texas), Cincinnati Flying Pig Marathon (Cincinnati, Ohio), and the Ocala Marathon (Ocala, Florida). Additionally, I collected meteorological variables for each race day and the five days leading up to the race (baseline). I tested these values against the finishing times for the local runners, those from the race state, and visitors, those from other locations. Effects of local acclimation could be evaluated by comparing finishing times of local runners to the change between the race day and baseline weather conditions. Locals experienced a significant impact on finishing times for large changes between race day and the baseline conditions for humidity variables, dew point temperature, vapor pressure, relative humidity, and temperature based variables such as the heat index, temperature and the saturation vapor pressure. Wind speed and pressure values also marked a change in performance, however; pressure was determined to be a larger psychological factor than acclimation factor. The locals also demonstrated an acclimation effect as performance improved when conditions were similar on race day to baseline conditions for the three larger races. Humidity variables had the largest impact on runners when those values increased from training and acclimation values; however increased wind speed appeared to offset increased humidity values. These findings support previous acclimation research stating warm wet conditions are more difficult to acclimate to than warm dry conditions. This research while primarily pertaining to those participating physically demanding activities may also be applied to other large scale events such as festivals, fairs, or concerts.
ContributorsDeBiasse, Kimberly Michelle (Author) / Cerveny, Randall S. (Thesis advisor) / Brazel, Anthony (Committee member) / Selover, Nancy (Committee member) / Arizona State University (Publisher)
Created2011
Description
This thesis outlines the development of a vector retrieval technique, based on data assimilation, for a coherent Doppler LIDAR (Light Detection and Ranging). A detailed analysis of the Optimal Interpolation (OI) technique for vector retrieval is presented. Through several modifications to the OI technique, it is shown that the modified technique results in significant improvement in velocity retrieval accuracy. These modifications include changes to innovation covariance portioning, covariance binning, and analysis increment calculation. It is observed that the modified technique is able to make retrievals with better accuracy, preserves local information better, and compares well with tower measurements. In order to study the error of representativeness and vector retrieval error, a lidar simulator was constructed. Using the lidar simulator a thorough sensitivity analysis of the lidar measurement process and vector retrieval is carried out. The error of representativeness as a function of scales of motion and sensitivity of vector retrieval to look angle is quantified. Using the modified OI technique, study of nocturnal flow in Owens' Valley, CA was carried out to identify and understand uncharacteristic events on the night of March 27th 2006. Observations from 1030 UTC to 1230 UTC (0230 hr local time to 0430 hr local time) on March 27 2006 are presented. Lidar observations show complex and uncharacteristic flows such as sudden bursts of westerly cross-valley wind mixing with the dominant up-valley wind. Model results from Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®) and other in-situ instrumentations are used to corroborate and complement these observations. The modified OI technique is used to identify uncharacteristic and extreme flow events at a wind development site. Estimates of turbulence and shear from this technique are compared to tower measurements. A formulation for equivalent wind speed in the presence of variations in wind speed and direction, combined with shear is developed and used to determine wind energy content in presence of turbulence.
ContributorsChoukulkar, Aditya (Author) / Calhoun, Ronald (Thesis advisor) / Mahalov, Alex (Committee member) / Kostelich, Eric (Committee member) / Huang, Huei-Ping (Committee member) / Phelan, Patrick (Committee member) / Arizona State University (Publisher)
Created2013
Description
Modern day gas turbine designers face the problem of hot mainstream gas ingestion into rotor-stator disk cavities. To counter this ingestion, seals are installed on the rotor and stator disk rims and purge air, bled off from the compressor, is injected into the cavities. It is desirable to reduce the supply of purge air as this decreases the net power output as well as efficiency of the gas turbine. Since the purge air influences the disk cavity flow field and effectively the amount of ingestion, the aim of this work was to study the cavity velocity field experimentally using Particle Image Velocimetry (PIV). Experiments were carried out in a model single-stage axial flow turbine set-up that featured blades as well as vanes, with purge air supplied at the hub of the rotor-stator disk cavity. Along with the rotor and stator rim seals, an inner labyrinth seal was provided which split the disk cavity into a rim cavity and an inner cavity. First, static gage pressure distribution was measured to ensure that nominally steady flow conditions had been achieved. The PIV experiments were then performed to map the velocity field on the radial-tangential plane within the rim cavity at four axial locations. Instantaneous velocity maps obtained by PIV were analyzed sector-by-sector to understand the rim cavity flow field. It was observed that the tangential velocity dominated the cavity flow at low purge air flow rate, its dominance decreasing with increase in the purge air flow rate. Radially inboard of the rim cavity, negative radial velocity near the stator surface and positive radial velocity near the rotor surface indicated the presence of a recirculation region in the cavity whose radial extent increased with increase in the purge air flow rate. Qualitative flow streamline patterns are plotted within the rim cavity for different experimental conditions by combining the PIV map information with ingestion measurements within the cavity as reported in Thiagarajan (2013).
ContributorsPathak, Parag (Author) / Roy, Ramendra P (Thesis advisor) / Calhoun, Ronald (Committee member) / Lee, Taewoo (Committee member) / Arizona State University (Publisher)
Created2013
Description
Global climate change (GCC) is among the most important issues of the 21st century. Adaptation to and mitigation of climate change are some of the salient local and regional challenges scientists, decision makers, and the general public face today and will be in the near future. However, designed adaptation and mitigation strategies do not guarantee success in coping with global climate change. Despite the robust and convincing body for anthropogenic global climate change research and science there is still a significant gap between the recommendations provided by the scientific community and the actual actions by the public and policy makers. In order to design, implement, and generate sufficient public support for policies and planning interventions at the national and international level, it is necessary to have a good understanding of the public's perceptions regarding GCC. Based on survey research in nine countries, the purpose of this study is two-fold: First, to understand the nature of public perceptions of global climate change in different countries; and secondly to identi-fy perception factors which have a significant impact on the public's willingness to sup-port GCC policies or commit to behavioral changes to reduce GHG emissions. Factors such as trust in GCC information which need to be considered in future climate change communication efforts are also dealt with in this dissertation. This study has identified several aspects that need to be considered in future communication programs. GCC is characterized by high uncertainties, unfamiliar risks, and other characteristics of hazards which make personal connections, responsibility and engagement difficult. Communication efforts need to acknowledge these obstacles, build up trust and motivate the public to be more engaged in reducing GCC by emphasizing the multiple benefits of many policies outside of just reducing GCC. Levels of skepticism among the public towards the reality of GCC as well as the trustworthiness and sufficien-cy of the scientific findings varies by country. Thus, communicators need to be aware of their audience in order to decide how educational their program needs to be.
ContributorsHagen, Bjoern (Author) / Pijawka, David (Thesis advisor) / Brazel, Anthony (Committee member) / Chhetri, Netra (Committee member) / Guhathakurta, Subhrajit (Committee member) / Arizona State University (Publisher)
Created2013
Description
This study considered the impact of grid resolution on wind velocity simulated by the Weather Research and Forecasting (WRF) model. The period simulated spanned November 2009 through January 2010, for which, multi-resolution nested domains were examined. Basic analysis was performed utilizing the data assimilation tools of NCEP/NCAR (National Center for Environmental Prediction/National Center for Atmospheric Research) to determine the ideal location to examine during the simulation was the Pacific Northwest portion of the United States, specifically the border between California and Oregon. The simulated mutli-resolution nested domains in this region indicated an increase in apparent wind speed as the resolution for the domain was increased. These findings were confirmed by statistical analysis which identified a positive bias for wind speed with respect to increased resolution as well as a correlation coefficient indicating the existence of a positive change in wind speed with increased resolution. An analysis of temperature change was performed in order to test the validity of the findings of the WRF simulation model. The statistical analysis performed on temperature change throughout the increased grid resolution did not indicate any change in temperature. In fact the correlation coefficient values between the domains were found in the 0.90 range, indicating the non-sensitivity of temperature across the increased resolutions. These results validate the findings of the WRF simulation: increased wind velocity can be observed at higher grid resolution. The study then considered the difference between wind velocity observed over the entire domains and the wind velocity observed solely over offshore locations. Wind velocity was observed to be significantly higher (an increase of 68.4%) in the offshore locations. The findings of this study suggest simulation tools should be utilized to examine domains at a higher resolution in order to identify potential locations for wind farms. The results go further to suggest the ideal location for these potential wind farms will be at offshore locations.
ContributorsBouey, Michael (Author) / Huang, Huei-Ping (Thesis advisor) / Trimble, Steve (Committee member) / Ronald, Ronald (Committee member) / Arizona State University (Publisher)
Created2012
Description
This study performs numerical modeling for the climate of semi-arid regions by running a high-resolution atmospheric model constrained by large-scale climatic boundary conditions, a practice commonly called climate downscaling. These investigations focus especially on precipitation and temperature, quantities that are critical to life in semi-arid regions. Using the Weather Research and Forecast (WRF) model, a non-hydrostatic geophysical fluid dynamical model with a full suite of physical parameterization, a series of numerical sensitivity experiments are conducted to test how the intensity and spatial/temporal distribution of precipitation change with grid resolution, time step size, the resolution of lower boundary topography and surface characteristics. Two regions, Arizona in U.S. and Aral Sea region in Central Asia, are chosen as the test-beds for the numerical experiments: The former for its complex terrain and the latter for the dramatic man-made changes in its lower boundary conditions (the shrinkage of Aral Sea). Sensitivity tests show that the parameterization schemes for rainfall are not resolution-independent, thus a refinement of resolution is no guarantee of a better result. But, simulations (at all resolutions) do capture the inter-annual variability of rainfall over Arizona. Nevertheless, temperature is simulated more accurately with refinement in resolution. Results show that both seasonal mean rainfall and frequency of extreme rainfall events increase with resolution. For Aral Sea, sensitivity tests indicate that while the shrinkage of Aral Sea has a dramatic impact on the precipitation over the confine of (former) Aral Sea itself, its effect on the precipitation over greater Central Asia is not necessarily greater than the inter-annual variability induced by the lateral boundary conditions in the model and large scale warming in the region. The numerical simulations in the study are cross validated with observations to address the realism of the regional climate model. The findings of this sensitivity study are useful for water resource management in semi-arid regions. Such high spatio-temporal resolution gridded-data can be used as an input for hydrological models for regions such as Arizona with complex terrain and sparse observations. Results from simulations of Aral Sea region are expected to contribute to ecosystems management for Central Asia.
ContributorsSharma, Ashish (Author) / Huang, Huei-Ping (Thesis advisor) / Adrian, Ronald (Committee member) / Herrmann, Marcus (Committee member) / Phelan, Patrick E. (Committee member) / Vivoni, Enrique (Committee member) / Arizona State University (Publisher)
Created2012
Description
A well-insulated dark conventional rooftop can be hotter than any other urban surface, including pavements. Since rooftops cover around 20 – 25% of most urban areas, their role in the urban heat island effect is significant. In general, buildings exchange heat with the surroundings in three ways: heat release from the cooling/heating system, air exchange associated with exfiltration and relief air, and heat transfer between the building envelope and surroundings. Several recent studies show that the building envelope generates more heat release into the environment than any other building component.Current advancements in material science have enabled the development of materials and coatings with very high solar reflectance and thermal emissivity, and that can alter their radiative properties based on surface temperature. This dissertation is an effort to quantify the impact of recent developments in such technologies on urban air. The current study addresses three specific unresolved topics: 1) the relative importance of rooftop solar reflectance and thermal emissivity, 2) the role of rooftop radiative properties in different climates, and 3) the impact of temperature-adaptive exterior materials/coatings on building energy savings and urban cooling. The findings from this study show that the use of rooftop materials with solar reflectance above 0.9 maintain the surface temperature below ambient air temperature most of the time, even when the materials have conventional thermal emissivity (0.9). This research has demonstrated that for hot cities, rooftops with high solar reflectance and thermal emittance maximize building energy savings and always cool the surrounding air. For moderate climate regions, high solar reflectance and low thermal emittance result in the greatest building energy cost savings. This combination of radiative properties cools the air during the daytime and warms it at night. Finally, this research found that temperature-adaptive materials could play a significant role in reducing utility costs for poorly insulated buildings, but that they heat the surrounding air in the winter, irrespective of the rooftop insulation.
Through the detailed analysis of building façade radiative properties, this dissertation offers climate-specific design guidance that can be used to simultaneously optimize energy costs while minimizing adverse warming of the surrounding environment.
ContributorsPrem Anand Jayaprabha, Jyothis Anand (Author) / Sailor, David (Thesis advisor) / Phelan, Patrick (Thesis advisor) / Huang, Huei-Ping (Committee member) / Wang, Liping (Committee member) / Yeom, Dongwoo Jason (Committee member) / Arizona State University (Publisher)
Created2022
Description
The fast pace of global urbanization makes cities the hotspots of population density and anthropogenic activities, leading to intensive emissions of heat and carbon dioxide (CO2), a primary greenhouse gas. Urban climate scientists have been actively seeking effective mitigation strategies over the past decades, aiming to improve the environmental quality for urban dwellers. Prior studies have identified the role of urban green spaces in the relief of urban heat stress. Yet little effort was devoted to quantify their contribution to local and regional CO2 budget. In fact, urban biogenic CO2 fluxes from photosynthesis and respiration are influenced by the microclimate in the built environment and are sensitive to anthropogenic disturbance. The high complexity of the urban ecosystem leads to an outstanding challenge for numerical urban models to disentangling and quantifying the interplay between heat and carbon dynamics.This dissertation aims to advance the simulation of thermal and carbon dynamics in urban land surface models, and to investigate the role of urban greening practices and urban system design in mitigating heat and CO2 emissions. The biogenic CO2 exchange in cities is parameterized by incorporating plant physiological functions into an advanced single-layer urban canopy model in the built environment. The simulation result replicates the microclimate and CO2 flux patterns measured from an eddy covariance system over a residential neighborhood in Phoenix, Arizona with satisfactory accuracy. Moreover, the model decomposes the total CO2 flux from observation and identifies the significant CO2 efflux from soil respiration. The model is then applied to quantify the impact of urban greening practices on heat and biogenic CO2 exchange over designed scenarios. The result shows the use of urban greenery is effective in mitigating both urban heat and carbon emissions, providing environmental co-benefit in cities. Furthermore, to seek the optimal urban system design in terms of thermal comfort and CO2 reduction, a multi-objective optimization algorithm is applied to the machine learning surrogates of the physical urban land surface model. There are manifest trade-offs among ameliorating diverse urban environmental indicators despite the co-benefit from urban greening. The findings of this dissertation, along with its implications on urban planning and landscaping management, would promote sustainable urban development strategies for achieving optimal environmental quality for policy makers, urban residents, and practitioners.
ContributorsLi, Peiyuan (Author) / Wang, Zhihua (Thesis advisor) / Vivoni, Enrique (Committee member) / Huang, Huei-Ping (Committee member) / Myint, Soe (Committee member) / Xu, Tianfang (Committee member) / Arizona State University (Publisher)
Created2021
Description
Dust storms have far-reaching human and economic impacts; spreading disease, raspatory and cardiovascular disruption, destruction of property and crops, and death. Understanding of this phenomenon is can help with operational and academic endeavors and alleviate some of these impacts. To accomplish this goal, this dissertation poses a central question: Do dust storms have discreet geographic and temporal characteristics that can aid academic and operational analysis of these storms? To answer this question three case studies were undertaken. The first study constructed an archive of 549 dust rain events across Europe to determine a seasonal pattern. It was discovered that the largest number of events occurred in the Spring season (MAM). Then three individual events across Europe were examined to highlight the synoptic events that control these dust rains. Each event can be closely tied to the movement of the migratory Rossby waves and linked to Saharan dust from North Africa. The second study was a construction of Central Sonoran Desert dust storms from 2009 to 2022 tied to the NAM. HYSPLIT back-trajectories linked the strongest events to source regions mainly from the Southwest along the Gila River from the Gulf of California. As the storms weaken in intensity they drift to the South and Southeast traveling along the Santa Cruz River and its tributaries. The third study was a case study of three large events in the Central Sonoran Desert along the Gila River. This study examines the effects of the local topography, specifically the stand-alone mountain complexes that can block or funnel dust as it moves through the Gila River Valley. In each instance the South Mountain Complex and the Sierra Estrella served as a dust shield containing the highest dust concentrations to the south side of the Gila River Valley. This dissertation has analyzed several of the different elements of dust storms. These elements include the synoptic patterns that drive dust storms, the source regions of dust storms, and the ground level topography that can control their movement. Fundamentally, these findings can enhance our academic understanding of dust storms as well as our operational ability to forecast.
ContributorsWhite, Joshua Randolph (Author) / Cerveny, Randall S. (Thesis advisor) / Balling Jr., Robert C. (Committee member) / Brazel, Anthony (Committee member) / Arizona State University (Publisher)
Created2024
Description
Urban-induced heating is a challenge to the livability and health of city dwellers. It is a complex issue that many cities are facing, and a more urgent hazard in hot urban deserts (HUDs) than elsewhere due to already high temperatures and aridity. The challenge compounds in the absence of more localized heat mitigation understanding. In addition, over-reliance on evidence from temperate regions is disconnected from the actualities of extreme bioclimatic dynamics found in HUDs. This dissertation is an integration of a series of studies that inform urban climate relationships specific to HUDs. This three-paper dissertation demonstrates heat mitigation aspirational goals from actualities, depicts local urban thermal drivers in Kuwait, and then tests morphological sensitivity of selected thermal modulation strategies in one neighborhood in Kuwait City.
The first paper is based on a systematic literature review where evidence from morphological mitigation strategies in HUDs were critically reviewed, synthesized and integrated. Metrics, measurements, and methods were extracted to examine the applicability of the different strategies, and a content synthesis identified the levels of strategy success. Collective challenges and uncertainties were interpreted to compare aspirational goals from actualities of morphological mitigation strategies.
The second paper unpacks the relationship of urban morphological attributes in influencing thermal conditions to assess latent magnitudes of heat amelioration strategies. Mindful of the challenges presented in the first study, a 92-day summer field-measurement campaign captured system dynamics of urban thermal stimuli within sub-diurnal phenomena. A composite data set of sub-hourly air temperature measurements with sub-meter morphological attributes was built, statistically analyzed, and modeled. Morphological mediation effects were found to vary hourly with different patterns under varying weather conditions in non-linear associations. Results suggest mitigation interventions be investigated and later tested on a site- use and time-use basis.
The third paper concludes with a simulation-based study to conform on the collective findings of the earlier studies. The microclimate model ENVI-met 4.4, combined with field measurements, was used to simulate the effect of rooftop shade-sails in cooling the near ground thermal environment. Results showed significant cooling effects and thus presented a novel shading approach that challenges orthodox mitigation strategies in HUDs.
The first paper is based on a systematic literature review where evidence from morphological mitigation strategies in HUDs were critically reviewed, synthesized and integrated. Metrics, measurements, and methods were extracted to examine the applicability of the different strategies, and a content synthesis identified the levels of strategy success. Collective challenges and uncertainties were interpreted to compare aspirational goals from actualities of morphological mitigation strategies.
The second paper unpacks the relationship of urban morphological attributes in influencing thermal conditions to assess latent magnitudes of heat amelioration strategies. Mindful of the challenges presented in the first study, a 92-day summer field-measurement campaign captured system dynamics of urban thermal stimuli within sub-diurnal phenomena. A composite data set of sub-hourly air temperature measurements with sub-meter morphological attributes was built, statistically analyzed, and modeled. Morphological mediation effects were found to vary hourly with different patterns under varying weather conditions in non-linear associations. Results suggest mitigation interventions be investigated and later tested on a site- use and time-use basis.
The third paper concludes with a simulation-based study to conform on the collective findings of the earlier studies. The microclimate model ENVI-met 4.4, combined with field measurements, was used to simulate the effect of rooftop shade-sails in cooling the near ground thermal environment. Results showed significant cooling effects and thus presented a novel shading approach that challenges orthodox mitigation strategies in HUDs.
ContributorsAlKhaled, Saud R A H (Author) / Coseo, Paul (Thesis advisor) / Brazel, Anthony (Thesis advisor) / Middel, Ariane (Committee member) / Cheng, Chingwen (Committee member) / Arizona State University (Publisher)
Created2019