Skip to main content

Yuh-lang Lin

North Carolina Agricultural and Technical State University, Energy & Environmental Systems, Faculty Member

Followers

40

Following

15

Co-authors

9

Public Views

Dr. Yuh-Lang Lin is a professor at the Department of Physics, North Carolina A
Phone: 336-285-2127
Address: 302H Gibbs Hall, NC A&T State U, 1601 E. Market Street, Greensboro, NC 27411

less

Interests

Uploads

Papers by Yuh-lang Lin

Multiscale Dynamics of the February 11-12, 2010, Deep South US Snowstorm Event

Advances in Meteorology

This study investigates the synoptic/mesoscale dynamics responsible for an unusually heavy southe... more This study investigates the synoptic/mesoscale dynamics responsible for an unusually heavy southern US snowstorm that occurred on February 11-12, 2010, using reanalysis, observations, and numerical simulations. This record breaking snowfall event represents an example of multiple upper level and low-level jets (LLJs) and their accompanying baroclinic zones. The analysis reveals the following synoptic scale processes as significant contributors: (1) upper level jet splitting and merging, (2) advection of cold arctic air at low levels by a large anticyclone, and (3) an incoming upper level shortwave trough. In addition to the synoptic scale processes, the following mesoscale features played a major role in this snowstorm event: coexisting potential (convective) instability and conditional symmetric instability, terrain blocking, and a double LLJ development process. Sensitivity experiments including (1) limiting the orographic effects of elevated plateau in Texas and the Sierra Madre ...

Convective Density Current Circulations That Modulated Meso-γ Surface Winds near the Yarnell Hill Fire

Fire

On 30 June 2013, 19 Granite Mountain Hotshots firefighters were killed fighting a wildfire near Y... more On 30 June 2013, 19 Granite Mountain Hotshots firefighters were killed fighting a wildfire near Yarnell in the mountains of Central Arizona. They succumbed when the wildfire, driven by erratic winds, blocked their escape route and overran their location. A previous study is extended to simulate and analyze the downscale organization of convective circulations that redirected the wildfire, which started from the scale of the Rossby Wave Breaking over North America to a convective gust front that redirected the wildfire, trapping the firefighters. Five stages are found: Stage I, the initial deep prolonged gust front; Stage II, a front-to-rear jet and its ascending motions that organized high-based convection; Stage III, high-based dry microburst-induced downdrafts organized initially by ascending flow in Stage II that transported mass and entropy to the surface; Stage IV; multiple meso-γ-scale high centers and confluence zones formed that encompassed the firefighters’ location, which ...

Some common ingredients for orographic flooding and heavy rainfall

Weather and Forecasting, 2001

Simulating Virtual Terminal Area Weather Data Bases for Use in the Wake Vortex Avoidance System (Wake VAS) Prediction Algorithm

During the research project, sounding datasets were generated for the region surrounding 9 major ... more During the research project, sounding datasets were generated for the region surrounding 9 major airports, including Dallas, TX, Boston, MA, New York, NY, Chicago, IL, St. Louis, MO, Atlanta, GA, Miami, FL, San Francico, CA, and Los Angeles, CA. The numerical simulation of winter and summer environments during which no instrument flight rule impact was occurring at these 9 terminals was performed using the most contemporary version of the Terminal Area PBL Prediction System (TAPPS) model nested from 36 km to 6 km to 1 km horizontal resolution and very detailed vertical resolution in the planetary boundary layer. The soundings from the 1 km model were archived at 30 minute time intervals for a 24 hour period and the vertical dependent variables as well as derived quantities, i.e., 3-dimensional wind components, temperatures, pressures, mixing ratios, turbulence kinetic energy and eddy dissipation rates were then interpolated to 5 m vertical resolution up to 1000 m elevation above gro...

Continued Research into Characterizing the Preturbulence Environment for Sensor Development, New Hazard Algorithms and Experimental Flight Planning

The purpose of the research was to develop and test improved hazard algorithms that could result ... more The purpose of the research was to develop and test improved hazard algorithms that could result in the development of sensors that are better able to anticipate potentially severe atmospheric turbulence, which affects aircraft safety. The research focused on employing numerical simulation models to develop improved algorithms for the prediction of aviation turbulence. This involved producing both research simulations and real-time simulations of environments predisposed to moderate and severe aviation turbulence. The research resulted in the following fundamental advancements toward the aforementioned goal: 1) very high resolution simulations of turbulent environments indicated how predictive hazard indices could be improved resulting in a candidate hazard index that indicated the potential for improvement over existing operational indices, 2) a real-time turbulence hazard numerical modeling system was improved by correcting deficiencies in its simulation of moist convection and 3)...

Characterizing the Preturbulence Environment for Sensor Development, New Hazard Algorithms and NASA Experimental Flight Planning

During the grant period, several tasks were performed in support of the NASA Turbulence Predictio... more During the grant period, several tasks were performed in support of the NASA Turbulence Prediction and Warning Systems (TPAWS) program. The primary focus of the research was on characterizing the preturbulence environment by developing predictive tools and simulating atmospheric conditions that preceded severe turbulence. The goal of the research being to provide both dynamical understanding of conditions that preceded turbulence as well as providing predictive tools in support of operational NASA B-757 turbulence research flights. The advancements in characterizing the preturbulence environment will be applied by NASA to sensor development for predicting turbulence onboard commercial aircraft. Numerical simulations with atmospheric models as well as multi-scale observational analyses provided insights into the environment organizing turbulence in a total of forty-eight specific case studies of severe accident producing turbulence on commercial aircraft. These accidents exclusively ...

GP-Extra: Pathways to Atmospheric Science Through Immersion in Geosciences Research

Geological Society of America Abstracts with Programs, 2017

Formation Mechanisms of the Mesoscale Environment Conducive to a Downslope Windstorm over the Cuyamaca Mountains Associated with Santa Ana Wind during the Cedar Fire (2003)

Journal of Applied Meteorology and Climatology

Numerical simulations were conducted to investigate the upstream environment’s impacts on the air... more Numerical simulations were conducted to investigate the upstream environment’s impacts on the airflow over the lee slope of the Cuyamaca Mountains (CM) near San Diego, California, during the Cedar Fire that occurred from 25 to 29 October 2003. The upstream environment was largely controlled by a southwest–northeast-oriented upper-tropospheric jet streak that rotated around a positively tilted ridge within the polar jet stream. Three sequential dynamical processes were found to be responsible for modifying the mesoscale environment conducive to low-level momentum and dry air that sustained the Cedar Fire. First, the sinking motion associated with the indirect circulation of the jet streak’s exit region strengthened the midtropospheric flow over the southern Rockies and the lee slope of the Sawatch and San Juan Ranges, thus modestly affecting the airflow by enhancing the downslope wind over the CM. Second, consistent with the coupling process between the upper-level sinking motion, do...

The Development of a Stratospheric Real-Time Turbulence Modeling SystemScient

AFRL-VS-HA-TR-2006-1110 The Development of a Stratospheric Real-Time Turbulence Modeling System Y... more

Characterizing the Severe Turbulence

Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. ... more Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the lead center for NASA’ s scientific and technical information. The NASA STI Program Office provides access to the NASA STI Database, the largest collection of aeronautical and space science STI in the world. The Program Office is also NASA’ s institutional mechanism for disseminating the results of its research and development activities. These results are published by NASA in the NASA STI Report Series, which includes the following report types:

12.3 Finite Difference Approximations of the Advection Equation

Chapter 12 Numerical Methods 12.1

Effects of Mechanical and Thermal Forcing on the Enhancement and Ingredients of Orographic Rain Associated with the 2007-08 Madden-Julian Oscillation Passing the New Guinea Highlands

Earth Science Research

In this study, the Advanced Research Weather Research and Forecasting (WRF) model was adopted to ... more In this study, the Advanced Research Weather Research and Forecasting (WRF) model was adopted to investigate the mechanical and thermal forcing effects associated with the New Guinea Highland (NGH) on Madden-Julian Oscillation (MJO) propagation and rainfall formation and enhancement mechanisms over the island of New Guinea. Our results show that both forces affect the propagation of the MJO07-08, resulting in orographic rainfall production. Even though each forcing helps produce orographic rainfall, the mechanical forcing of the NGH plays a much larger role in the orographic blocking than the thermal forcing. We also found two flow regimes associated with the propagation of MJO07-08 over the NGH. First, in the flow-around regime, the MJO and its associated convective system split around the NGH due to the strong orographic blocking. We can observe this splitting when looking at the splitting stage. Second, the flow-over regime could occur when the mountain is lower than its original...

Generation and Enhancement Mechanisms and Essential Ingredients for the Extreme Orographic Rainfall Associated with Typhoon Morakot (2009) Passing over Taiwan’s Central Mountain Range

Effects of Density Current, Diurnal Heating, and Local Terrain on the Mesoscale Environment Conducive to the Yarnell Hill Fire

Atmosphere, 2022

The Yarnell Hill Fire, triggered by dry lightning on 28 June 2013, was initiated by hot and dry w... more The Yarnell Hill Fire, triggered by dry lightning on 28 June 2013, was initiated by hot and dry westerly winds, which rapidly shifted to north-northeast by convective-induced outflows. This sudden wind shift led to the demise of 19 firefighters. This study focuses on the environment and its predictive potential in terms of erratically changing the fire spread. Three numerical sensitivity tests are performed investigating the evolving synoptic-meso-β scale environmental wind flow: (1) deactivating the evaporative cooling, (2) deactivating surface-driven diurnal heating/cooling, and (3) removing the mountain. Results show the strong north-northeasterly wind induced by the density current(s) and the diurnal surface sensible heating played the most significant roles in enhancing the mesoscale environment conducive to the rapid change in the fire spread direction. While the mountain played a less significant role in weakening the magnitude of the airflow affecting the fire, it still had ...

P1.15 Modeling Track Deflection for Tropical Cyclones Passing Over a Mesoscale Mountain and Its Potential Application to Track Prediction

In this study, we use observed tropical cyclones and a simple mesoscale model (GFDM), along with ... more

P1.14 the Maintenance of a MCC Across Norhtern Africa: A Case Study and Analysis Realting to Surface Moisture Variables an Fluxes

This research focuses on the precursor of Hurricane Alberto that initially formed over the Ethiop... more

P3.31 Control Parameters for Track Continuity and Deflection Associated with Tropical Cyclones Over a Mesoscale Mountain

The orographic influence on TC tracks has been studied extensively over Taiwan’s Central Mountain... more

The Effects of Orographic Geometry on Supercell Thunderstorms

arXiv: Atmospheric and Oceanic Physics, 2016

The effect of elongated bell-shaped mountain orientation on supercell thunderstorms is numericall... more The effect of elongated bell-shaped mountain orientation on supercell thunderstorms is numerically investigated using the Bryan Cloud Model 1 (CM1). The orography is varied by three mountain heights and is varied in four different positions, effectively producing 12 different terrain configurations. It is found that the different orientations produce variations in the supercell life cycle with shorter cycles for higher inflow rates. Furthermore, these cycles are associated with the storm reaching its minimum intensity just after a peak rain period. Moreover, the effect of stronger inflow was seen before direct storm-terrain interactions started. The higher inflow also played a significant role in increasing rainfall rate and areal extent, to the point that further convection, associated with the cold pool, was triggered adding to rainfall amount. Using a stricter form of the National Weather Service Tornado Detection Algorithm to investigate the tornadic nature of simulated supercel...

Flow Regimes of a Continuously Stratified Flow over a Mesoscale Mountain and their Impacts on Aviation Turbulence

One important source of aviation turbulence is gravity wave breaking induced by airflow over meso... more One important source of aviation turbulence is gravity wave breaking induced by airflow over mesoscale mountains, which is responsible for many severe turbulence encounters. The purpose of this study is to investigate gravity wave breaking over terrain in different parameter space. In order to gain a more in-depth understanding of the dynamics, we perform a series of systematic idealized simulations with idealized bell-shaped mountains by adopting the Cloud Model 1 (CM1) to avoid some unnecessary complications from the real atmosphere and test some hypotheses. For a uniform, but structured flow over a mesoscale mountain, two distinguished flow regimes are found: (I) upward propagating moist gravity waves (GW) regime and (II) evanescent fluid flow (EV), depending upon the hydrostatic control parameter (Na/U), similar to a uniform, unstructured flow. The flow associated with the GW regime tends to steepen, overturn, create a wave-induced critical level, trap the energy below it, and t...

Cold-Air Damming : Their Interactions and Impacts on 1 Heavy Rainfall in the Carolinas 2 3 4 5 6

The interactions between an Appalachian cold-air damming event and the near-passage of Tropical S... more The interactions between an Appalachian cold-air damming event and the near-passage of Tropical Storm Kyle (2002) along the coastal Carolinas are assessed by using a numerical weather prediction model. As the storm moved along the coastline, it began extra-tropical transition, bringing heavy rains to both the coastal region and inland towards the Piedmont of North Carolina. Our goal is to quantify the effects of both interacting weather systems on heavy precipitation in order to improve the dynamical understanding of such effects, as well as precipitation forecasts in the study region. A series of sensitivity tests were performed to isolate and quantify the effects of both systems on the total accumulated precipitation. It was found that (a) for this type of alongcoast track, the pre-existing cold-air damming played only a minor role on the total accumulated precipitation, (b) the outer circulation of Kyle weakened the cold-air damming due to a redirection of the mean flow away from the east side of the Appalachian Mountains, and (c) the combination of Kyle with a shortwave mid to upper-level trough and a surface coastal front were responsible for the heavy precipitation experienced in the study area through the advection of moisture, vorticity, and the forcing of upward motion.