DOCSLIB.ORG

Leeds Thesis Template

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Leeds Thesis Template Processes controlling the evolution of deep moist convection in the summertime West African Sahel Miroslav Provod University of Leeds School of Earth and Environment Submitted in accordance with the requirements for the degree of Doctor of Philosophy March 2016 The University of Leeds - ii - Declaration of Authorship The candidate confirms that the work submitted is his/her own, except where work which has formed part of jointly-authored publications has been included. The contribution of the candidate and the other authors to this work has been explicitly indicated below. The candidate confirms that appropriate credit has been given within the thesis where reference has been made to the work of others. Chapter 3 includes characterization of cold pools which has been published, with co-authors, in Monthly Weather Review. The reference is Provod, M., J.H. Marsham, D.J. Parker, C.E. Birch, A Characterization of Cold Pools in the West African Sahel, MWR, 2016. J. H. Marsham and D.J. Parker supervised the student. C.E. Birch gave advice on methods and ran model simulations (these not used in the publication, but are used throughout the thesis). This copy has been supplied on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement. The right of Miroslav Provod to be identified as Author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988. © 2016 The University of Leeds and Miroslav Provod - iii - Acknowledgements Firstly, I would like to express my thanks to my academic supervisors John Marsham and Doug Parker. Their advice, patience and help have been invaluable during the completion of this thesis. John has always been there to answer my questions, give advice and provide prompt feedback on results and gave invaluable guidance during the completion of this thesis. Both John and Doug have provided some great ideas that led to results in this thesis. I would also like to thank Cathryn Birch who ran some of the Cascade simulations, the output of which has been used throughout the thesis. Cathryn also promptly and fully answered all the questions I had regarding model output. Several other members of the School of Earth and Environment provided a great help throughout the PhD. A special thanks goes to Richard Pope, who gave a great help during struggles with code and provided hours of his time to explain and teach me some complex IDL coding. Richard Rigby, in IT support, has always provided great and very prompt help during IT issues. A great thanks also goes to all the current and past people in the office, both for help when it was needed as well as for the great office environment, including: Richard Pope, Becky Jansen, Nsikanabasi Silas Umo, Sarah Dennis, Hannah Walker, Seshagirirao Kolusu, Lindsay Lee, John Prytherch, Peggy Achtert, Mark Holden, Kirsty Pringle and Tamsin Farmer. Apologies if I missed out someone. We are a team and I will really miss you! My family also deserves to be mentioned. My wife, Lucie Provodova, my daughter, Sofia Provodova, my parents, Miroslav Provod and Dana Provodova, and sister, Marketa Provodova, have been all vital to me, not only during this PhD, but throughout my life, providing support of every form. Without your help, this thesis would not be here. Thank you all!!! - iv - Abstract Deep moist convection and mesoscale convective systems (MCSs) are integral to the West African monsoon and, as the main rain-producing mechanism in the Sahel, are essential to the livelihoods of millions. Current operational forecasting models struggle to predict rainfall with a good precision. It is therefore necessary to study the processes controlling deep moist convection in detail, in order to understand them better and to be able to evaluate simulations to identify errors for future model development. In this thesis properties of cold pools from Sahelian MCSs were characterised from surface observations. It was observed that early season cold pools were stronger and drier, likely due to drier mid-levels before the monsoon onset. The properties of observed cold pools were used to evaluate a Unified Model (UM) convection-permitting simulation. The comparison showed that simulated cold pools are generally weaker than observed. Cold pools and MCS structure were further investigated in two case studies. This enabled an analysis of MCS vertical structure. Processes controlling the diurnal cycle of convection were analysed using observations and UM simulations. This showed that while surface CAPE follows a diurnal cycle with a maximum in the afternoon and minimum in the early morning, elevated CAPE was found to have a nearly opposite cycle, due to advection of high equivalent potential temperature air overnight by the nocturnal low- level jet. In addition, the low-level jet provides low-level wind shear which balances the cold-pool related vorticity and helps to maintain the MCS until morning, when the jet decays and MCSs tend to dissipate. The jet also creates moisture flux convergence overnight, supporting MCSs. Finally, mechanisms underlying storm initiation and regeneration were analysed in UM simulations, showing the roles of soil moisture boundaries, pre-existing cold pools and bookend vortices. - v - Table of Contents Declaration of Authorship ......................................................................... ii Acknowledgements .................................................................................. iii Abstract ..................................................................................................... iv Table of Contents ....................................................................................... v List of Tables ...........................................................................................viiii List of Figures ........................................................................................... ix Abbreviations ...........................................................................................xix 1. Introduction ............................................................................................ 1 1.1 Motivations and aims ..................................................................... 1 1.1.1 Thesis structure .................................................................. 4 1.2 Literature review ............................................................................ 5 1.2.1. The West African Monsoon ................................................ 8 1.2.2. Mesoscale convective systems (MCSs) in the West Afrcian Monsoon ................................................................ 12 1.2.3. Simulations of MCSs in the West African Monsoon .......... 30 2. Methods ................................................................................................ 33 2.1 Observational datasets ................................................................ 27 2.2 Met-Office Unified Model convection-permitting simulations from the Cascade project ........................................................... 30 3. A Characterization of cold pools in the West African Sahel compared with a convection-permitting model ............................. 33 3.1 Introduction ................................................................................. 33 3.2 Methods ...................................................................................... 33 3.2.1 Cold pool detection in observed surface time-series and verification using remote-sensing data ....................................... 33 3.2.2 Selection of monsoon season sub-periods ........................... 35 3.2.3 Atmosphric tide and diurnal pressure variation ..................... 36 3.2.4 Statistical evaluation of observed cold-pool properties ......... 38 3.2.5 Evaluating cold pools in the 4 km covection-permitting Cascade simultions .................................................................... 39 3.3 Characterization of observed and simulated cold pools ...........40 3.3.1 Composite cold pools .............................................................. 39 3.3.2 Thermodynamic properties of cold pools ............................ 41 3.3.3 Role of mid-level dryness ................................................... 57 3.3.4 Cold-pool winds .................................................................. 61 - vi - 3.4 Conclusions ................................................................................ 69 4. Case studies of two squall-line mesoscale convective systems ...... 73 4.1 Introduction ........................................................................ 73 4.2 Methods ............................................................................. 78 4.2.1 Data ............................................................................ 78 4.2.2 TIme-to-space conversion .......................................... 79 4.2.3 Vertical profiles ........................................................... 81 4.3 Results ............................................................................... 83 4.3.1 Case study of 22nd July 2006 squall-line MCS ............ 83 4.3.2 Case study of 31st July 2006 squall-line MCS ............. 95 4.3.3 Preliminary analysis of UM simulation of the 31st July 2006 squall-line MCS .......................................................106 4.4 Discussion & Conclusions .................................................109 4.4.1 Future work ................................................................111
Load more

Recommended publications
  • ESSENTIALS of METEOROLOGY (7Th Ed.) GLOSSARY
    ESSENTIALS OF METEOROLOGY (7th ed.) GLOSSARY Chapter 1 Aerosols Tiny suspended solid particles (dust, smoke, etc.) or liquid droplets that enter the atmosphere from either natural or human (anthropogenic) sources, such as the burning of fossil fuels. Sulfur-containing fossil fuels, such as coal, produce sulfate aerosols. Air density The ratio of the mass of a substance to the volume occupied by it. Air density is usually expressed as g/cm3 or kg/m3. Also See Density. Air pressure The pressure exerted by the mass of air above a given point, usually expressed in millibars (mb), inches of (atmospheric mercury (Hg) or in hectopascals (hPa). pressure) Atmosphere The envelope of gases that surround a planet and are held to it by the planet's gravitational attraction. The earth's atmosphere is mainly nitrogen and oxygen. Carbon dioxide (CO2) A colorless, odorless gas whose concentration is about 0.039 percent (390 ppm) in a volume of air near sea level. It is a selective absorber of infrared radiation and, consequently, it is important in the earth's atmospheric greenhouse effect. Solid CO2 is called dry ice. Climate The accumulation of daily and seasonal weather events over a long period of time. Front The transition zone between two distinct air masses. Hurricane A tropical cyclone having winds in excess of 64 knots (74 mi/hr). Ionosphere An electrified region of the upper atmosphere where fairly large concentrations of ions and free electrons exist. Lapse rate The rate at which an atmospheric variable (usually temperature) decreases with height. (See Environmental lapse rate.) Mesosphere The atmospheric layer between the stratosphere and the thermosphere.
    [Show full text]
  • A Comprehensive Observational Study of Graupel and Hail Terminal Velocity, Mass Flux, and Kinetic Energy
    NOVEMBER 2018 H E Y M S F I E L D E T A L . 3861 A Comprehensive Observational Study of Graupel and Hail Terminal Velocity, Mass Flux, and Kinetic Energy ANDREW HEYMSFIELD National Center for Atmospheric Research, Boulder, Colorado MIKLÓS SZAKÁLL AND ALEXANDER JOST Institute for Atmospheric Physics, Johannes Gutenberg University, Mainz, Germany IAN GIAMMANCO Insurance Institute for Business and Home Safety, Richburg, South Carolina ROBERT WRIGHT RLWA and Associates, Houston, Texas (Manuscript received 2 February 2018, in final form 24 August 2018) ABSTRACT This study uses novel approaches to estimate the fall characteristics of hail, covering a size range from about 0.5 to 7 cm, and the drag coefficients of lump and conical graupel. Three-dimensional (3D) volume scans of 60 hailstones of sizes from 2.5 to 6.7 cm were printed in three dimensions using acrylonitrile butadiene styrene (ABS) plastic, and their terminal velocities were measured in the Mainz, Germany, vertical wind tunnel. To simulate lump graupel, 40 of the hailstones were printed with maximum dimensions of about 0.2, 0.3, and 0.5 cm, and their terminal velocities were measured. Conical graupel, whose three dimensions (maximum dimension 0.1–1 cm) were estimated from an analytical representation and printed, and the terminal veloc- ities of seven groups of particles were measured in the tunnel. From these experiments, with printed particle 2 densities from 0.2 to 0.9 g cm 3, together with earlier observations, relationships between the drag coefficient and the Reynolds number and between the Reynolds number and the Best number were derived for a wide range of particle sizes and heights (pressures) in the atmosphere.
    [Show full text]
  • An Improved Representation of Rimed Snow and Conversion to Graupel in a Multicomponent Bin Microphysics Scheme
    MAY 2010 M O R R I S O N A N D G R A B O W S K I 1337 An Improved Representation of Rimed Snow and Conversion to Graupel in a Multicomponent Bin Microphysics Scheme HUGH MORRISON AND WOJCIECH W. GRABOWSKI National Center for Atmospheric Research,* Boulder, Colorado (Manuscript received 13 July 2009, in final form 22 January 2010) ABSTRACT This paper describes the development of a new multicomponent detailed bin ice microphysics scheme that predicts the number concentration of ice as well as the rime mass mixing ratio in each mass bin. This allows for local prediction of the rime mass fraction. In this approach, the ice particle mass size, projected area size, and terminal velocity–size relationships vary as a function of particle mass and rimed mass fraction, based on a simple conceptual model of rime accumulation in the crystal interstices that leads to an increase in particle mass, but not in its maximum size, until a complete ‘‘filling in’’ with rime and conversion to graupel occurs. This approach allows a natural representation of the gradual transition from unrimed crystals to rimed crystals and graupel during riming. The new ice scheme is coupled with a detailed bin representation of the liquid hy- drometeors and applied in an idealized 2D kinematic flow model representing the evolution of a mixed-phase precipitating cumulus. Results using the bin scheme are compared with simulations using a two-moment bulk scheme employing the same approach (i.e., separate prediction of bulk ice mixing ratio from vapor deposition and riming, allowing for local prediction of bulk rime mass fraction).
    [Show full text]
  • Cloud Microphysics
    Cloud microphysics Claudia Emde Meteorological Institute, LMU, Munich, Germany WS 2011/2012 Growth Precipitation Cloud modification Overview of cloud physics lecture Atmospheric thermodynamics gas laws, hydrostatic equation 1st law of thermodynamics moisture parameters adiabatic / pseudoadiabatic processes stability criteria / cloud formation Microphysics of warm clouds nucleation of water vapor by condensation growth of cloud droplets in warm clouds (condensation, fall speed of droplets, collection, coalescence) formation of rain, stochastical coalescence Microphysics of cold clouds homogeneous, heterogeneous, and contact nucleation concentration of ice particles in clouds crystal growth (from vapor phase, riming, aggregation) formation of precipitation, cloud modification Observation of cloud microphysical properties Parameterization of clouds in climate and NWP models Cloud microphysics December 15, 2011 2 / 30 Growth Precipitation Cloud modification Growth from the vapor phase in mixed-phase clouds mixed-phase cloud is dominated by super-cooled droplets air is close to saturated w.r.t. liquid water air is supersaturated w.r.t. ice Example ◦ T=-10 C, RHl ≈ 100%, RHi ≈ 110% ◦ T=-20 C, RHl ≈ 100%, RHi ≈ 121% )much greater supersaturations than in warm clouds In mixed-phase clouds, ice particles grow from vapor phase much more rapidly than droplets. Cloud microphysics December 15, 2011 3 / 30 Growth Precipitation Cloud modification Mass growth rate of an ice crystal diffusional growth of ice crystal similar to growth of droplet by condensation more complicated, mainly because ice crystals are not spherical )points of equal water vapor do not lie on a sphere centered on crystal dM = 4πCD (ρ (1) − ρ ) dt v vc Cloud microphysics December 15, 2011 4 / 30 P732951-Ch06.qxd 9/12/05 7:44 PM Page 240 240 Cloud Microphysics determined by the size and shape of the conductor.
    [Show full text]
  • Graupel Or Hailstone), Some Negative Ions Transferred to the Colder Object What Causes the Charge Distribution? Part 2
    ATM 10 Severe and Unusual Weather Prof. Richard Grotjahn L 15/16 http://canvas.ucdavis.edu/ Lecture topics: • Lightning – Formation of charge conditions – Demonstrations – Various types – Climatology – Damage – Safety do’s and don’ts – videos • Hail – Formation – Locations – Damage Short Video Segments • Lightning – Daytime lightning & sound (10 sec, .mov) – Night, slow crawlers (18 sec, mpg) – Night, city (10 sec, mpg) What is lightning? • A very large spark • Traveling through a poor conductor (air) What is thunder? • Lightning instantly heats air to ~30,000 C (~54,000 F)! • Heated air expands (ideal gas law) compressing adjacent air • Sound wave (thunder) is created Perceiving Thunder • Air attenuates (absorbs) sound, removing high frequencies sooner than low • You hear high pitch “Crack!” (from that part of lightning close to you) • followed by low rumbles for that part of lightning furthest away • Sound waves (like light) refract (bend) towards cooler air (recall mirages) • If you are too far away (~15km) you may not hear it, though you see a flash “heat lightning” • Sound travels • 1 km in 3 seconds • 1 mile in 5 seconds bolt traveling horizontally towards camera, then dipping to the ground Lightning Bolt = Giant Spark 1. Negative charge in cloud base attracts positive charge on ground (esp. high pts) 2. "Stepped leader" steps downward 50-100m at a time -- creates the jagged shape. Each step ~ 50/1,000,000 second 3. When step leader nears the ground, ground leaders may rise from taller objects 4. << BOOM!>> -- positive charge rushes up: this is much brighter RETURN STROKE. A short circuit. The stepped leader made the air conducting along that path and the return stroke follows that easier path.
    [Show full text]
  • P1.4 West Texas Mesonet Observations of Wake Lows and Heat Bursts Across Northwest Texas
    P1.4 WEST TEXAS MESONET OBSERVATIONS OF WAKE LOWS AND HEAT BURSTS ACROSS NORTHWEST TEXAS Mark R. Conder*, Steven R. Cobb, and Gary D. Skwira National Weather Service Forecast Office, Lubbock, Texas 1. INTRODUCTION Wake lows (WLs) and heat bursts (HBs) are mesoscale phenomena associated with thunderstorms that can result in strong and sometimes severe (>25.5 m s-1), near-surface winds. The operational detection of severe winds is problematic because the associated convection can appear quite innocuous via WSR-88D data. The thermodynamic environment that supports WL and HB development is similar, and is often compared to the classic “onion” sounding structure as described by Zipser (1977). Observational studies such as Johnson et al. (1989) show that nearly dry-adiabatic lapse rates are prevalent in the lower to mid-troposphere, with a shallow stable layer near ground level. This type of environment is most commonly observed in the high plains during the warm season. While documented heat bursts were infrequent in the past, the recent expansion of surface mesonetworks are increasing the likelihood that these events will be sampled. One such network is the West Texas Mesonet (WTXM), a collection of over 40 meteorological stations spread across the Panhandle and South Plains of northwest Texas. During the period 1 June 2004 to 30 August 2006, the authors have FIG. 1. The Study area including the WTXM station recorded 10 WL/HB events that have been sampled by locations. Not all stations were available for every stations of the WTXM. Some of the more extreme event. measurements include a 15 degrees Celsius increase in temperature at the Pampa and McClean WTXM sites in -1 Meteorological data from each WTXM station is one event and 35 m s wind gusts at sites in Brownfield recorded in 5-minute intervals, representing average and Jayton on separate occasions.
    [Show full text]
  • The Southern Plains Cyclone
    The Southern Plains Cyclone A Weather Newsletter from your Norman Forecast Office for the Residents of western and central Oklahoma and western north Texas We Make the Difference When it Matters Most! Volume 2 Summer 2004 Issue 3 Behind the Scenes at the Norman Forecast Office Meet Your Weatherman Cheryl Sharpe By Rick Smith, Warning Coordination Meteorologist The National Weather Service’s ther caused by the weather or made main mission is to provide information worse by the weather – tornadoes and to help save lives. This is the reason we severe thunderstorms, flooding, ice come to work everyday. We are part of a storms, blizzards, wildfires, and heat network of 122 local weather forecast waves, among others. But, did you offices that cover the entire United know that the Norman Forecast Office States, with each office responsible for a also plays a key role in assisting with specific group of counties. The people at non-weather related disasters? each of these offices work hard to pro- From the Murrah Building bombing vide the best local weather information in 1995 to wildfires and other non- possible. weather related emergencies, the NWS At the Norman Forecast Office, we provides support and information in a take this responsibility seriously and variety of situations. ¡Hola! I am Cheryl Sharpe, one of strive to be the best when it comes to pro- We are staffed 24 hours a day every- the general forecasters at the Norman viding information you can use to help day of the year with at least two people Forecast Office. In addition to my regu- make decisions, plan activities, or just on shift at all times to allow us to re- lar duties as a meteorologist, I also assist live your day-to-day life in Oklahoma spond.
    [Show full text]
  • 2.3 Case Study Verification of Ruc/Maps Fog and Visibility Forecasts
    Preprints, 9th Conf. on Aviation, Range, and Aerospace Meteorology, AMS, Orlando, FL, September 2000 2.3 CASE STUDY VERIFICATION OF RUC/MAPS FOG AND VISIBILITY FORECASTS Tatiana G. Smirnova* Cooperative Institute for Research in Environmental Sciences (CIRES) University of Colorado/NOAA Forecast Systems Laboratory Boulder, Colorado Stanley G. Benjamin, John M. Brown NOAA Forecast Systems Laboratory Boulder, Colorado 1. INTRODUCTION predictions of surface conditions important for efficient operations in the vicinity of air terminals. Recently per- The Rapid Update Cycle (RUC) which runs operationally formed validations of MAPS/RUC hydrological cycle com- at the National Centers for Environmental Prediction ponents, such as precipitation, evapotranspiration and (NCEP) (Benjamin et al. 1999, 1998), and its experimen- soil moisture, as well as of skin temperature demonstrate tal version (Mesoscale Analysis and Prediction System - the model’s capability to represent surface processes MAPS) run at Forecast Systems Laboratory, were de- with a good degree of realism (Smirnova et al. 2000b). signed to provide frequently updated weather predictions Accurate prediction of aviation-impact variables for better guidance to aviation and other short-range fore- such as fog, surface visibility and cloud ceiling is impor- cast users. In January 2000, several additional aviation- tant for terminal operations. In this paper, a RUC visibility impact diagnostic variables became routinely available as algorithm (an extension to the Stoelinga-Warner (1999) part of the RUC output fields, including visibility, cloud algorithm) is presented and applied to native-grid RUC base (ceiling), stable cloud top, convective cloud top po- output to product diagnostic fields of surface visibility. tential, and surface wind gust potential.
    [Show full text]
  • Rime and Graupel: Description and Characterization As Revealed by Low-Temperature Scanning Electron Microscopy
    SCANNING VOL. 25, 121–131 (2003) Received: November 27, 2002 © FAMS, Inc. Accepted: February 20, 2003 Rime and Graupel: Description and Characterization as Revealed by Low-Temperature Scanning Electron Microscopy ALBERT RANGO,JAMES FOSTER,* EDWARD G. JOSBERGER,† ERIC F. ERBE,‡ CHRISTOPHER POOLEY,‡§ WILLIAM P. W ERGIN‡ Jornada Experimental Range, Agricultural Research Service (ARS), U. S. Department of Agriculture (USDA), New Mexico State University, Las Cruces, New Mexico; *Laboratory for Hydrological Sciences, NASA Goddard Space Flight Center, Green- belt, Maryland; †U. S. Geological Survey, Washington Water Science Center, Tacoma, Washington; ‡Soybean Genomics and Improvement Laboratory, ARS, USDA; §Hydrology and Remote Sensing Laboratory, ARS, USDA, Beltsville, Maryland, USA Summary: Snow crystals, which form by vapor deposition, ticle 1 to 3 mm across, composed of hundreds of frozen occasionally come in contact with supercooled cloud cloud droplets interspersed with considerable air spaces; the droplets during their formation and descent. When this oc- original snow crystal is no longer discernible. This study curs, the droplets adhere and freeze to the snow crystals in increases our knowledge about the process and character- a process known as accretion. During the early stages of istics of riming and suggests that the initial appearance of accretion, discrete snow crystals exhibiting frozen cloud the flattened hemispheres may result from impact of the droplets are referred to as rime. If this process continues, leading face of the snow crystal with cloud droplets. The the snow crystal may become completely engulfed in elongated and sinuous configurations of frozen cloud frozen cloud droplets. The resulting particle is known as droplets that are encountered on the more advanced stages graupel.
    [Show full text]
  • Climate Change and Its Impacts in Japan, October 2009
    Synthesis Report on Observations, Projections, and Impact Assessments of Climate Change Climate Change and Its Impacts in Japan October 2009 Ministry of Education, Culture, Sports, Science and Technology (MEXT) Japan Meteorological Agency (JMA) Ministry of the Environment (MOE) . Contents 1. Introduction ........................................................................................................................................1 2. Mechanisms of Climate Change and Contributions of Anthropogenic Factors — What are the Causes of Global Warming? ......................................................................................................2 2.1 Factors affecting climate change ...................................................................................................2 2.2 The main cause of global warming since the mid-20th century is anthropogenic forcing ...............3 2.3 Confidence in observation data and simulation results by models ................................................5 2.4 Changes on longer time scales and particularity of recent change................................................5 [Column 1] Definitions of Terms Related to Climate Change .....................................................8 [Column 2] Aerosols and Climate Change..................................................................................10 3. Past, Present, and Future of the Climate — What is the Current State and Future of Global Warming?.........................................................................................................................................11
    [Show full text]
  • The Impact of Unique Meteorological Phenomena Detected by the Oklahoma Mesonet and ARS Micronet on Automated Quality Control Christopher A
    The Impact of Unique Meteorological Phenomena Detected by the Oklahoma Mesonet and ARS Micronet on Automated Quality Control Christopher A. Fiebrich and Kenneth C. Crawford Oklahoma Climatological Survey, Norman, Oklahoma ABSTRACT To ensure quality data from a meteorological observing network, a well-designed quality control system is vital. Automated quality assurance (QA) software developed by the Oklahoma Mesonetwork (Mesonet) provides an effi- cient means to sift through over 500 000 observations ingested daily from the Mesonet and from a Micronet spon- sored by the Agricultural Research Service of the United States Department of Agriculture (USDA). However, some of nature's most interesting meteorological phenomena produce data that fail many automated QA tests. This means perfectly good observations are flagged as erroneous. Cold air pooling, "inversion poking," mesohighs, mesolows, heat bursts, variations in snowfall and snow cover, and microclimatic effects produced by variations in vegetation are meteorological phenomena that pose a problem for the Mesonet's automated QA tests. Despite the fact that the QA software has been engineered for most observa- tions of real meteorological phenomena to pass the various tests—but is stringent enough to catch malfunctioning sensors—erroneous flags are often placed on data during extreme events. This manuscript describes how the Mesonet's automated QA tests responded to data captured from microscale meteorological events that, in turn, were flagged as erroneous by the tests. The Mesonet's operational plan is to cata- log these extreme events in a database so QA flags can be changed manually by expert eyes. 1. Introduction and personnel at the central processing site for the Oklahoma Mesonet in Norman, Oklahoma.
    [Show full text]
  • A Comprehensive Observational Study of Graupel and Hail Terminal Velocity, Mass Flux, and Kinetic Energy
    NOVEMBER 2018 H E Y M S F I E L D E T A L . 3861 A Comprehensive Observational Study of Graupel and Hail Terminal Velocity, Mass Flux, and Kinetic Energy ANDREW HEYMSFIELD National Center for Atmospheric Research, Boulder, Colorado MIKLÓS SZAKÁLL AND ALEXANDER JOST Institute for Atmospheric Physics, Johannes Gutenberg University, Mainz, Germany IAN GIAMMANCO Insurance Institute for Business and Home Safety, Richburg, South Carolina ROBERT WRIGHT RLWA and Associates, Houston, Texas (Manuscript received 2 February 2018, in final form 24 August 2018) ABSTRACT This study uses novel approaches to estimate the fall characteristics of hail, covering a size range from about 0.5 to 7 cm, and the drag coefficients of lump and conical graupel. Three-dimensional (3D) volume scans of 60 hailstones of sizes from 2.5 to 6.7 cm were printed in three dimensions using acrylonitrile butadiene styrene (ABS) plastic, and their terminal velocities were measured in the Mainz, Germany, vertical wind tunnel. To simulate lump graupel, 40 of the hailstones were printed with maximum dimensions of about 0.2, 0.3, and 0.5 cm, and their terminal velocities were measured. Conical graupel, whose three dimensions (maximum dimension 0.1–1 cm) were estimated from an analytical representation and printed, and the terminal veloc- ities of seven groups of particles were measured in the tunnel. From these experiments, with printed particle 2 densities from 0.2 to 0.9 g cm 3, together with earlier observations, relationships between the drag coefficient and the Reynolds number and between the Reynolds number and the Best number were derived for a wide range of particle sizes and heights (pressures) in the atmosphere.
    [Show full text]