Cracking the AQ Code
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The Generation of a Mesoscale Convective System from Mountain Convection
JUNE 1999 TUCKER AND CROOK 1259 The Generation of a Mesoscale Convective System from Mountain Convection DONNA F. T UCKER Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas N. ANDREW CROOK National Center for Atmospheric Research Boulder, Colorado (Manuscript received 18 November 1997, in ®nal form 13 July 1998) ABSTRACT A mesoscale convective system (MCS) that formed just to the east of Denver is investigated with a nonhy- drostatic numerical model to determine which processes were important in its initiation. The MCS developed from out¯ow from previous convective activity in the Rocky Mountains to the west. Model results indicate that this out¯ow was necessary for the development of the MCS even though a convergence line was already present in the area where the MCS developed. A simulation with a 3-km grid spacing more fully resolves the convective activity in the mountains but the development of the MCS can be simulated with a 6.67-km grid. Cloud effects on solar radiation and ice sedimentation both in¯uence the strength of the out¯ow from the mountain convection but only the ice sedimentation makes a signi®cant impact on the development of the MCS after its initiation. The frequent convective activity in the Rocky Mountains during the warm season provides out¯ow that would make MCS generation favorable in this region. Thus, there is a close connection between mountain convective activity and MCS generation. The implications of such a connection are discussed and possible directions of future research are indicated. 1. Introduction scale or mesoscale. Forced lifting always occurs on the windward side of mountains; however, the mechanisms Mesoscale convective systems (MCSs) commonly de- that promote lifting on the downwind side of mountains, velop in the central United States during the warm sea- where a large proportion of MCSs initiate, are not as son, accounting for 30%±70% of the summer precipi- obvious. -
The Impact of Outflow Environment on Tropical Cyclone Intensification And
VOLUME 68 JOURNAL OF THE ATMOSPHERIC SCIENCES FEBRUARY 2011 The Impact of Outflow Environment on Tropical Cyclone Intensification and Structure ERIC D. RAPPIN Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, Florida MICHAEL C. MORGAN AND GREGORY J. TRIPOLI University of Wisconsin—Madison, Madison, Wisconsin (Manuscript received 3 October 2008, in final form 5 June 2009) ABSTRACT In this study, the impacts of regions of weak inertial stability on tropical cyclone intensification and peak strength are examined. It is demonstrated that weak inertial stability in the outflow layer minimizes an energy sink of the tropical cyclone secondary circulation and leads to more rapid intensification to the maximum potential intensity. Using a full-physics, three-dimensional numerical weather prediction model, a symmetric distribution of environmental inertial stability is generated using a variable Coriolis parameter. It is found that the lower the value of the Coriolis parameter, the more rapid the strengthening. The lower-latitude simulation is shown to have a significantly stronger secondary circulation with intense divergent outflow against a com- paratively weak environmental resistance. However, the impacts of differences in the gradient wind balance between the different latitudes on the core structure cannot be neglected. A second study is then conducted using an asymmetric inertial stability distribution generated by the presence of a jet stream to the north of the tropical cyclone. The initial intensification is similar, or even perhaps slower, in the presence of the jet as a result of increased vertical wind shear. As the system evolves, convective outflow from the tropical cyclone modifies the jet resulting in weaker shear and more rapid intensification of the tropical cyclone–jet couplet. -
Weather and Climate: Changing Human Exposures K
CHAPTER 2 Weather and climate: changing human exposures K. L. Ebi,1 L. O. Mearns,2 B. Nyenzi3 Introduction Research on the potential health effects of weather, climate variability and climate change requires understanding of the exposure of interest. Although often the terms weather and climate are used interchangeably, they actually represent different parts of the same spectrum. Weather is the complex and continuously changing condition of the atmosphere usually considered on a time-scale from minutes to weeks. The atmospheric variables that characterize weather include temperature, precipitation, humidity, pressure, and wind speed and direction. Climate is the average state of the atmosphere, and the associated characteristics of the underlying land or water, in a particular region over a par- ticular time-scale, usually considered over multiple years. Climate variability is the variation around the average climate, including seasonal variations as well as large-scale variations in atmospheric and ocean circulation such as the El Niño/Southern Oscillation (ENSO) or the North Atlantic Oscillation (NAO). Climate change operates over decades or longer time-scales. Research on the health impacts of climate variability and change aims to increase understanding of the potential risks and to identify effective adaptation options. Understanding the potential health consequences of climate change requires the development of empirical knowledge in three areas (1): 1. historical analogue studies to estimate, for specified populations, the risks of climate-sensitive diseases (including understanding the mechanism of effect) and to forecast the potential health effects of comparable exposures either in different geographical regions or in the future; 2. studies seeking early evidence of changes, in either health risk indicators or health status, occurring in response to actual climate change; 3. -
An Observational Analysis Quantifying the Distance of Supercell-Boundary Interactions in the Great Plains
Magee, K. M., and C. E. Davenport, 2020: An observational analysis quantifying the distance of supercell-boundary interactions in the Great Plains. J. Operational Meteor., 8 (2), 15-38, doi: https://doi.org/10.15191/nwajom.2020.0802 An Observational Analysis Quantifying the Distance of Supercell-Boundary Interactions in the Great Plains KATHLEEN M. MAGEE National Weather Service Huntsville, Huntsville, AL CASEY E. DAVENPORT University of North Carolina at Charlotte, Charlotte, NC (Manuscript received 11 June 2019; review completed 7 October 2019) ABSTRACT Several case studies and numerical simulations have hypothesized that baroclinic boundaries provide enhanced horizontal and vertical vorticity, wind shear, helicity, and moisture that induce stronger updrafts, higher reflectivity, and stronger low-level rotation in supercells. However, the distance at which a surface boundary will provide such enhancement is less well-defined. Previous studies have identified enhancement at distances ranging from 10 km to 200 km, and only focused on tornado production and intensity, rather than all forms of severe weather. To better aid short-term forecasts, the observed distances at which supercells produce severe weather in proximity to a boundary needs to be assessed. In this study, the distance between a large number of observed supercells and nearby surface boundaries (including warm fronts, stationary fronts, and outflow boundaries) is measured throughout the lifetime of each storm; the distance at which associated reports of large hail and tornadoes occur is also collected. Statistical analyses assess the sensitivity of report distributions to report type, boundary type, boundary strength, angle of interaction, and direction of storm motion relative to the boundary. -
Squall Lines: Meteorology, Skywarn Spotting, & a Brief Look at the 18
Squall Lines: Meteorology, Skywarn Spotting, & A Brief Look At The 18 June 2010 Derecho Gino Izzi National Weather Service, Chicago IL Outline • Meteorology 301: Squall lines – Brief review of thunderstorm basics – Squall lines – Squall line tornadoes – Mesovorticies • Storm spotting for squall lines • Brief Case Study of 18 June 2010 Event Thunderstorm Ingredients • Moisture – Gulf of Mexico most common source locally Thunderstorm Ingredients • Lifting Mechanism(s) – Fronts – Jet Streams – “other” boundaries – topography Thunderstorm Ingredients • Instability – Measure of potential for air to accelerate upward – CAPE: common variable used to quantify magnitude of instability < 1000: weak 1000-2000: moderate 2000-4000: strong 4000+: extreme Thunderstorms Thunderstorms • Moisture + Instability + Lift = Thunderstorms • What kind of thunderstorms? – Single Cell – Multicell/Squall Line – Supercells Thunderstorm Types • What determines T-storm Type? – Short/simplistic answer: CAPE vs Shear Thunderstorm Types • What determines T-storm Type? (Longer/more complex answer) – Lot we don’t know, other factors (besides CAPE/shear) include • Strength of forcing • Strength of CAP • Shear WRT to boundary • Other stuff Thunderstorm Types • Multi-cell squall lines most common type of severe thunderstorm type locally • Most common type of severe weather is damaging winds • Hail and brief tornadoes can occur with most the intense squall lines Squall Lines & Spotting Squall Line Terminology • Squall Line : a relatively narrow line of thunderstorms, often -
NWS Unified Surface Analysis Manual
Unified Surface Analysis Manual Weather Prediction Center Ocean Prediction Center National Hurricane Center Honolulu Forecast Office November 21, 2013 Table of Contents Chapter 1: Surface Analysis – Its History at the Analysis Centers…………….3 Chapter 2: Datasets available for creation of the Unified Analysis………...…..5 Chapter 3: The Unified Surface Analysis and related features.……….……….19 Chapter 4: Creation/Merging of the Unified Surface Analysis………….……..24 Chapter 5: Bibliography………………………………………………….…….30 Appendix A: Unified Graphics Legend showing Ocean Center symbols.….…33 2 Chapter 1: Surface Analysis – Its History at the Analysis Centers 1. INTRODUCTION Since 1942, surface analyses produced by several different offices within the U.S. Weather Bureau (USWB) and the National Oceanic and Atmospheric Administration’s (NOAA’s) National Weather Service (NWS) were generally based on the Norwegian Cyclone Model (Bjerknes 1919) over land, and in recent decades, the Shapiro-Keyser Model over the mid-latitudes of the ocean. The graphic below shows a typical evolution according to both models of cyclone development. Conceptual models of cyclone evolution showing lower-tropospheric (e.g., 850-hPa) geopotential height and fronts (top), and lower-tropospheric potential temperature (bottom). (a) Norwegian cyclone model: (I) incipient frontal cyclone, (II) and (III) narrowing warm sector, (IV) occlusion; (b) Shapiro–Keyser cyclone model: (I) incipient frontal cyclone, (II) frontal fracture, (III) frontal T-bone and bent-back front, (IV) frontal T-bone and warm seclusion. Panel (b) is adapted from Shapiro and Keyser (1990) , their FIG. 10.27 ) to enhance the zonal elongation of the cyclone and fronts and to reflect the continued existence of the frontal T-bone in stage IV. -
Articles from Bon, Inorganic Aerosol and Sea Salt
Atmos. Chem. Phys., 18, 6585–6599, 2018 https://doi.org/10.5194/acp-18-6585-2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 3.0 License. Meteorological controls on atmospheric particulate pollution during hazard reduction burns Giovanni Di Virgilio1, Melissa Anne Hart1,2, and Ningbo Jiang3 1Climate Change Research Centre, University of New South Wales, Sydney, 2052, Australia 2Australian Research Council Centre of Excellence for Climate System Science, University of New South Wales, Sydney, 2052, Australia 3New South Wales Office of Environment and Heritage, Sydney, 2000, Australia Correspondence: Giovanni Di Virgilio ([email protected]) Received: 22 May 2017 – Discussion started: 28 September 2017 Revised: 22 January 2018 – Accepted: 21 March 2018 – Published: 8 May 2018 Abstract. Internationally, severe wildfires are an escalating build-up of PM2:5. These findings indicate that air pollution problem likely to worsen given projected changes to climate. impacts may be reduced by altering the timing of HRBs by Hazard reduction burns (HRBs) are used to suppress wild- conducting them later in the morning (by a matter of hours). fire occurrences, but they generate considerable emissions Our findings support location-specific forecasts of the air of atmospheric fine particulate matter, which depend upon quality impacts of HRBs in Sydney and similar regions else- prevailing atmospheric conditions, and can degrade air qual- where. ity. Our objectives are to improve understanding of the re- lationships between meteorological conditions and air qual- ity during HRBs in Sydney, Australia. We identify the pri- mary meteorological covariates linked to high PM2:5 pollu- 1 Introduction tion (particulates < 2.5 µm in diameter) and quantify differ- ences in their behaviours between HRB days when PM2:5 re- Many regions experience regular wildfires with the poten- mained low versus HRB days when PM2:5 was high. -
Quantifying the Impact of Synoptic Weather Types and Patterns On
1 Quantifying the impact of synoptic weather types and patterns 2 on energy fluxes of a marginal snowpack 3 Andrew Schwartz1, Hamish McGowan1, Alison Theobald2, Nik Callow3 4 1Atmospheric Observations Research Group, University of Queensland, Brisbane, 4072, Australia 5 2Department of Environment and Science, Queensland Government, Brisbane, 4000, Australia 6 3School of Agriculture and Environment, University of Western Australia, Perth, 6009, Australia 7 8 Correspondence to: Andrew J. Schwartz ([email protected]) 9 10 Abstract. 11 Synoptic weather patterns are investigated for their impact on energy fluxes driving melt of a marginal snowpack 12 in the Snowy Mountains, southeast Australia. K-means clustering applied to ECMWF ERA-Interim data identified 13 common synoptic types and patterns that were then associated with in-situ snowpack energy flux measurements. 14 The analysis showed that the largest contribution of energy to the snowpack occurred immediately prior to the 15 passage of cold fronts through increased sensible heat flux as a result of warm air advection (WAA) ahead of the 16 front. Shortwave radiation was found to be the dominant control on positive energy fluxes when individual 17 synoptic weather types were examined. As a result, cloud cover related to each synoptic type was shown to be 18 highly influential on the energy fluxes to the snowpack through its reduction of shortwave radiation and 19 reflection/emission of longwave fluxes. As single-site energy balance measurements of the snowpack were used 20 for this study, caution should be exercised before applying the results to the broader Australian Alps region. 21 However, this research is an important step towards understanding changes in surface energy flux as a result of 22 shifts to the global atmospheric circulation as anthropogenic climate change continues to impact marginal winter 23 snowpacks. -
Forecasting of Thunderstorms in the Pre-Monsoon Season at Delhi
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Publications of the IAS Fellows Meteorol. Appl. 6, 29–38 (1999) Forecasting of thunderstorms in the pre-monsoon season at Delhi N Ravi1, U C Mohanty1, O P Madan1 and R K Paliwal2 1Centre for Atmospheric Sciences, Indian Institute of Technology, New Delhi 110 016, India 2National Centre for Medium Range Weather Forecasting, Mausam Bhavan Complex, Lodi Road, New Delhi 110 003, India Accurate prediction of thunderstorms during the pre-monsoon season (April–June) in India is essential for human activities such as construction, aviation and agriculture. Two objective forecasting methods are developed using data from May and June for 1985–89. The developed methods are tested with independent data sets of the recent years, namely May and June for the years 1994 and 1995. The first method is based on a graphical technique. Fifteen different types of stability index are used in combinations of different pairs. It is found that Showalter index versus Totals total index and Jefferson’s modified index versus George index can cluster cases of occurrence of thunderstorms mixed with a few cases of non-occurrence along a zone. The zones are demarcated and further sub-zones are created for clarity. The probability of occurrence/non-occurrence of thunderstorms in each sub-zone is then calculated. The second approach uses a multiple regression method to predict the occurrence/non- occurrence of thunderstorms. A total of 274 potential predictors are subjected to stepwise screening and nine significant predictors are selected to formulate a multiple regression equation that gives the forecast in probabilistic terms. -
The Evolution of the 10–11 June 1985 PRE-STORM Squall Line: Initiation
478 MONTHLY WEATHER REVIEW VOLUME 125 The Evolution of the 10±11 June 1985 PRE-STORM Squall Line: Initiation, Development of Rear In¯ow, and Dissipation SCOTT A. BRAUN AND ROBERT A. HOUZE JR. Department of Atmospheric Sciences, University of Washington, Seattle, Washington (Manuscript received 12 December 1995, in ®nal form 12 August 1996) ABSTRACT Mesoscale analysis of surface observations and mesoscale modeling results show that the 10±11 June squall line, contrary to prior studies, did not form entirely ahead of a cold front. The primary environmental features leading to the initiation and organization of the squall line were a low-level trough in the lee of the Rocky Mountains and a midlevel short-wave trough. Three additional mechanisms were active: a southeastward-moving cold front formed the northern part of the line, convection along the edge of cold air from prior convection over Oklahoma and Kansas formed the central part of the line, and convection forced by convective out¯ow near the lee trough axis formed the southern portion of the line. Mesoscale model results show that the large-scale environment signi®cantly in¯uenced the mesoscale cir- culations associated with the squall line. The qualitative distribution of along-line velocities within the squall line is attributed to the larger-scale circulations associated with the lee trough and midlevel baroclinic wave. Ambient rear-to-front (RTF) ¯ow to the rear of the squall line, produced by the squall line's nearly perpendicular orientation to strong westerly ¯ow at upper levels, contributed to the exceptional strength of the rear in¯ow in this storm. -
A Monsoon—A Weather Phenomenon Occurring Primarily in July, August and September—Brings Rain and Cooler Temperatures to Arizona
What is a Monsoon? A monsoon—a weather phenomenon occurring primarily in July, August and September—brings rain and cooler temperatures to Arizona. It also raises special concerns for you, your family and your property. A monsoon triggers heavy rainfall, lightning, severe winds, dust storms and flash floods—all of which can endanger homeowners, motorists or anyone caught unaware. Rain Rains throughout the state can quickly fill channels, rivers and washes, creating a potentially life- threatening danger. A flash flood caused by a short yet intense rainfall can occur virtually anywhere—mountains, canyons, flat desert or urban areas. The National Weather Service may issue watches or warnings to identify a thunderstorm hazard. A flood watch or flash flood watch means there is a possibility of flooding or a flash flood. Affected residents should take the following precautions. • Be prepared to evacuate. • If time allows, bring in outdoor furniture and move valuables to higher places in your home. • Unplug electrical appliances, and, if possible, move them to higher levels. Do not touch an electric appliance if you are wet or standing in water. • Keep the gas tank in your car full, in case you have to evacuate. A flood warning means a flood is occurring or will likely occur soon. If you are advised to evacuate, do so immediately. A flash flood warning means a flash flood is occurring. Seek higher ground immediately. Always listen to the radio or television for current information. Lightning Lightning is attracted to metal and water and tends to strike the highest or tallest objects. Observe the following to avoid lightning strikes: • You are in the lightning strike zone if you hear thunder five seconds or less after seeing lightning. -
CLOUD FRACTION: CAN IT BE DEFINED and MEASURED? and IF WE KNEW IT WOULD IT BE of ANY USE to US? Stephen E
CLOUD FRACTION: CAN IT BE DEFINED AND MEASURED? AND IF WE KNEW IT WOULD IT BE OF ANY USE TO US? Stephen E. Schwartz Upton NY USA Cloud Properties, Observations, and their Uncertainties www.bnl.gov/envsci/schwartz CLOUD FRACTION: CAN IT BE DEFINED AND MEASURED? AND IF WE KNEW IT WOULD IT BE OF ANY USE TO US? CONCLUSIONS No. No. No. I come to bury cloud fraction, not to praise it. - Shakespeare, 1599 WHAT IS A CLOUD? AMS Glossary of Meteorology (2000) A visible aggregate of minute water droplets and/or ice particles in the atmosphere above the earth’s surface. Total cloud cover: Fraction of the sky hidden by all visible clouds. Clothiaux, Barker, & Korolev (2005) Surprisingly, and in spite of the fact that we deal with clouds on a daily basis, to date there is no universal definition of a cloud. Ultimately, the definition of a cloud depends on the threshold sensitivity of the instruments used. Ramanathan, JGR (ERBE, 1988) Cloud cover is a loosely defined term. Potter Stewart (U.S. Supreme Court, 1964) I shall not today attempt further to define it, but I know it when I see it. WHY DO WE WANT TO KNOW CLOUD FRACTION, ANYWAY? Clouds have a strong impact on Earth’s radiation budget: -45 W m-2 shortwave; +30 W m-2 longwave. Slight change in cloud fraction could augment or offset greenhouse gas induced warming – cloud feedbacks. Getting cloud fraction “right” is an evaluation criterion for global climate models. Domain Observations Cloud cover Millions % Land 116 52.4 Ocean 43.3 64.8 Global 159 61.2 Warren, Hahn, London, Chervin, Jenne CLOUD FRACTION BY MULTIPLE METHODS 2 Surface, 3 satellite methods at U.S.