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A Comparison of Precipitation from Maritime and Continental Air
254 BULLETIN AMERICAN METEOROLOGICAL SOCIETY A Comparison of Precipitation from Maritime and Continental Air GEORGE S. BENTON 1 and ROBERT T. BLACKBURN 2 OR many decades, knowledge of atmospheric These 123 periods of precipitation for 1946 were F movements of water vapor has lagged behind grouped as indicated below. Classifications for other phases of meteorological information. In which precipitation was necessarily from maritime recent years, however, the accumulation of upper- air are marked with an asterisk; classifications for air data has stimulated hydrometeorological re- which precipitation was necessarily from contin- search. One interesting problem considered has ental air are marked with a double asterisk. For been the source of precipitation classified accord- all other classifications, precipitation may have ing to air mass. occurred either from maritime or continental air, In 1937 Holzman [2] advanced the hypothesis depending upon the individual circumstances. that the great majority of precipitation comes from maritime air masses. Although meteorologists I. Cold front have generally been willing to accept this hypothe- A. Pre-frontal precipitation sis on the basis of their qualitative familiarity with *1. MT present throughout tropo- atmospheric phenomena, little has been done to sphere determine quantitatively the percentage of pre- **2. cP present throughout tropo- cipitation which can actually be traced to maritime sphere air. Certainly the precipitation from continental 3. MT overriding cP in warm sec- air masses must be measurable and must vary in tor importance from region to region. B. Post-frontal precipitation In the course of an analysis of the role of the 1. MT overriding cP atmosphere in the hydrologic cycle [1], the au- *a. -
Air Masses and Fronts
CHAPTER 4 AIR MASSES AND FRONTS Temperature, in the form of heating and cooling, contrasts and produces a homogeneous mass of air. The plays a key roll in our atmosphere’s circulation. energy supplied to Earth’s surface from the Sun is Heating and cooling is also the key in the formation of distributed to the air mass by convection, radiation, and various air masses. These air masses, because of conduction. temperature contrast, ultimately result in the formation Another condition necessary for air mass formation of frontal systems. The air masses and frontal systems, is equilibrium between ground and air. This is however, could not move significantly without the established by a combination of the following interplay of low-pressure systems (cyclones). processes: (1) turbulent-convective transport of heat Some regions of Earth have weak pressure upward into the higher levels of the air; (2) cooling of gradients at times that allow for little air movement. air by radiation loss of heat; and (3) transport of heat by Therefore, the air lying over these regions eventually evaporation and condensation processes. takes on the certain characteristics of temperature and The fastest and most effective process involved in moisture normal to that region. Ultimately, air masses establishing equilibrium is the turbulent-convective with these specific characteristics (warm, cold, moist, transport of heat upwards. The slowest and least or dry) develop. Because of the existence of cyclones effective process is radiation. and other factors aloft, these air masses are eventually subject to some movement that forces them together. During radiation and turbulent-convective When these air masses are forced together, fronts processes, evaporation and condensation contribute in develop between them. -
Avoiding the Risks of Deadly Lightning Strikes
Avoiding the Risks of Deadly Lightning Strikes Lightning is one of the most underrated severe weather hazards, yet ranks as the second-leading weather killer in the United States. More deadly than hurricanes or tornadoes, lightning strikes in America each year kill an average of 73 people and injure 300 others, according to NOAA's National Weather Service. How Lightning Works Lightning is caused by the attraction between positive and negative charges in the atmosphere, resulting in the buildup and discharge of electrical energy. This rapid heating and cooling of the air produces the shock wave that results in thunder. During a storm, raindrops can acquire extra electrons, which are negatively charged. These surplus electrons seek out a positive charge from the ground. As they flow from the clouds, they knock other electrons free, creating a conductive path. This path follows a zigzag shape that jumps between randomly distributed clumps of charged particles in the air. When the two charges connect, current surges through that jagged path, creating the lightning bolt. The Warning Signs High winds, rainfall, and a darkening cloud cover are the warning signs for possible cloud-to- ground lightning strikes. While many lightning casualties happen at the beginning of an approaching storm, more than 50 percent of lightning deaths occur after the thunderstorm has passed. The lightning threat diminishes after the last sound of thunder, but may persist for more than 30 minutes. When thunderstorms are in the area, but not overhead, the lightning threat can exist when skies are clear. Safety Precautions While nothing offers absolute safety from lightning, some actions can greatly reduce your risks. -
A Winter Forecasting Handbook Winter Storm Information That Is Useful to the Public
A Winter Forecasting Handbook Winter storm information that is useful to the public: 1) The time of onset of dangerous winter weather conditions 2) The time that dangerous winter weather conditions will abate 3) The type of winter weather to be expected: a) Snow b) Sleet c) Freezing rain d) Transitions between these three 7) The intensity of the precipitation 8) The total amount of precipitation that will accumulate 9) The temperatures during the storm (particularly if they are dangerously low) 7) The winds and wind chill temperature (particularly if winds cause blizzard conditions where visibility is reduced). 8) The uncertainty in the forecast. Some problems facing meteorologists: Winter precipitation occurs on the mesoscale The type and intensity of winter precipitation varies over short distances. Forecast products are not well tailored to winter Subtle features, such as variations in the wet bulb temperature, orography, urban heat islands, warm layers aloft, dry layers, small variations in cyclone track, surface temperature, and others all can influence the severity and character of a winter storm event. FORECASTING WINTER WEATHER Important factors: 1. Forcing a) Frontal forcing (at surface and aloft) b) Jetstream forcing c) Location where forcing will occur 2. Quantitative precipitation forecasts from models 3. Thermal structure where forcing and precipitation are expected 4. Moisture distribution in region where forcing and precipitation are expected. 5. Consideration of microphysical processes Forecasting winter precipitation in 0-48 hour time range: You must have a good understanding of the current state of the Atmosphere BEFORE you try to forecast a future state! 1. Examine current data to identify positions of cyclones and anticyclones and the location and types of fronts. -
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. -
Environmental Systems the Atmosphere and Hydrosphere
Environmental Systems The atmosphere and hydrosphere THE ATMOSPHERE The atmosphere, the gaseous layer that surrounds the earth, formed over four billion years ago. During the evolution of the solid earth, volcanic eruptions released gases into the developing atmosphere. Assuming the outgassing was similar to that of modern volcanoes, the gases released included: water vapor (H2O), carbon monoxide (CO), carbon dioxide (CO2), hydrochloric acid (HCl), methane (CH4), ammonia (NH3), nitrogen (N2) and sulfur gases. The atmosphere was reducing because there was no free oxygen. Most of the hydrogen and helium that outgassed would have eventually escaped into outer space due to the inability of the earth's gravity to hold on to their small masses. There may have also been significant contributions of volatiles from the massive meteoritic bombardments known to have occurred early in the earth's history. Water vapor in the atmosphere condensed and rained down, of radiant energy in the atmosphere. The sun's radiation spans the eventually forming lakes and oceans. The oceans provided homes infrared, visible and ultraviolet light regions, while the earth's for the earliest organisms which were probably similar to radiation is mostly infrared. cyanobacteria. Oxygen was released into the atmosphere by these early organisms, and carbon became sequestered in sedimentary The vertical temperature profile of the atmosphere is variable and rocks. This led to our current oxidizing atmosphere, which is mostly depends upon the types of radiation that affect each atmospheric comprised of nitrogen (roughly 71 percent) and oxygen (roughly 28 layer. This, in turn, depends upon the chemical composition of that percent). -
Soaring Weather
Chapter 16 SOARING WEATHER While horse racing may be the "Sport of Kings," of the craft depends on the weather and the skill soaring may be considered the "King of Sports." of the pilot. Forward thrust comes from gliding Soaring bears the relationship to flying that sailing downward relative to the air the same as thrust bears to power boating. Soaring has made notable is developed in a power-off glide by a conven contributions to meteorology. For example, soar tional aircraft. Therefore, to gain or maintain ing pilots have probed thunderstorms and moun altitude, the soaring pilot must rely on upward tain waves with findings that have made flying motion of the air. safer for all pilots. However, soaring is primarily To a sailplane pilot, "lift" means the rate of recreational. climb he can achieve in an up-current, while "sink" A sailplane must have auxiliary power to be denotes his rate of descent in a downdraft or in come airborne such as a winch, a ground tow, or neutral air. "Zero sink" means that upward cur a tow by a powered aircraft. Once the sailcraft is rents are just strong enough to enable him to hold airborne and the tow cable released, performance altitude but not to climb. Sailplanes are highly 171 r efficient machines; a sink rate of a mere 2 feet per second. There is no point in trying to soar until second provides an airspeed of about 40 knots, and weather conditions favor vertical speeds greater a sink rate of 6 feet per second gives an airspeed than the minimum sink rate of the aircraft. -
Tornado Safety Q & A
TORNADO SAFETY Q & A The Prosper Fire Department Office of Emergency Management’s highest priority is ensuring the safety of all Prosper residents during a state of emergency. A tornado is one of the most violent storms that can rip through an area, striking quickly with little to no warning at all. Because the aftermath of a tornado can be devastating, preparing ahead of time is the best way to ensure you and your family’s safety. Please read the following questions about tornado safety, answered by Prosper Emergency Management Coordinator Kent Bauer. Q: During s evere weather, what does the Prosper Fire Department do? A: We monitor the weather alerts sent out by the National Weather Service. Because we are not meteorologists, we do not interpret any sort of storms or any sort of warnings. Instead, we pass along the information we receive from the National Weather Service to our residents through social media, storm sirens and Smart911 Rave weather warnings. Q: What does a Tornado Watch mean? A: Tornadoes are possible. Remain alert for approaching storms. Watch the sky and stay tuned to NOAA Weather Radio, commercial radio or television for information. Q: What does a Tornado Warning mean? A: A tornado has been sighted or indicated by weather radar and you need to take shelter immediately. Q: What is the reason for setting off the Outdoor Storm Sirens? A: To alert those who are outdoors that there is a tornado or another major storm event headed Prosper’s way, so seek shelter immediately. I f you are outside and you hear the sirens go off, do not call 9-1-1 to ask questions about the warning. -
Weather Charts Natural History Museum of Utah – Nature Unleashed Stefan Brems
Weather Charts Natural History Museum of Utah – Nature Unleashed Stefan Brems Across the world, many different charts of different formats are used by different governments. These charts can be anything from a simple prognostic chart, used to convey weather forecasts in a simple to read visual manner to the much more complex Wind and Temperature charts used by meteorologists and pilots to determine current and forecast weather conditions at high altitudes. When used properly these charts can be the key to accurately determining the weather conditions in the near future. This Write-Up will provide a brief introduction to several common types of charts. Prognostic Charts To the untrained eye, this chart looks like a strange piece of modern art that an angry mathematician scribbled numbers on. However, this chart is an extremely important resource when evaluating the movement of weather fronts and pressure areas. Fronts Depicted on the chart are weather front combined into four categories; Warm Fronts, Cold Fronts, Stationary Fronts and Occluded Fronts. Warm fronts are depicted by red line with red semi-circles covering one edge. The front movement is indicated by the direction the semi- circles are pointing. The front follows the Semi-Circles. Since the example above has the semi-circles on the top, the front would be indicated as moving up. Cold fronts are depicted as a blue line with blue triangles along one side. Like warm fronts, the direction in which the blue triangles are pointing dictates the direction of the cold front. Stationary fronts are frontal systems which have stalled and are no longer moving. -
CALIFORNIA STATE UNIVERSITY, NORTHRIDGE FORECASTING CALIFORNIA THUNDERSTORMS a Thesis Submitted in Partial Fulfillment of the Re
CALIFORNIA STATE UNIVERSITY, NORTHRIDGE FORECASTING CALIFORNIA THUNDERSTORMS A thesis submitted in partial fulfillment of the requirements For the degree of Master of Arts in Geography By Ilya Neyman May 2013 The thesis of Ilya Neyman is approved: _______________________ _________________ Dr. Steve LaDochy Date _______________________ _________________ Dr. Ron Davidson Date _______________________ _________________ Dr. James Hayes, Chair Date California State University, Northridge ii TABLE OF CONTENTS SIGNATURE PAGE ii ABSTRACT iv INTRODUCTION 1 THESIS STATEMENT 12 IMPORTANT TERMS AND DEFINITIONS 13 LITERATURE REVIEW 17 APPROACH AND METHODOLOGY 24 TRADITIONALLY RECOGNIZED TORNADIC PARAMETERS 28 CASE STUDY 1: SEPTEMBER 10, 2011 33 CASE STUDY 2: JULY 29, 2003 48 CASE STUDY 3: JANUARY 19, 2010 62 CASE STUDY 4: MAY 22, 2008 91 CONCLUSIONS 111 REFERENCES 116 iii ABSTRACT FORECASTING CALIFORNIA THUNDERSTORMS By Ilya Neyman Master of Arts in Geography Thunderstorms are a significant forecasting concern for southern California. Even though convection across this region is less frequent than in many other parts of the country significant thunderstorm events and occasional severe weather does occur. It has been found that a further challenge in convective forecasting across southern California is due to the variety of sub-regions that exist including coastal plains, inland valleys, mountains and deserts, each of which is associated with different weather conditions and sometimes drastically different convective parameters. In this paper four recent thunderstorm case studies were conducted, with each one representative of a different category of seasonal and synoptic patterns that are known to affect southern California. In addition to supporting points made in prior literature there were numerous new and unique findings that were discovered during the scope of this research and these are discussed as they are investigated in their respective case study as applicable. -
Exploring the MBL Cloud and Drizzle Microphysics Retrievals from Satellite, Surface and Aircraft
Exploring the MBL cloud and drizzle microphysics retrievals from satellite, surface and aircraft Xiquan Dong, University of Arizona Pat Minnis, SSAI 1. Briefly describe our 2. Can we utilize these surface newly developed retrieval retrievals to develop cloud (and/or drizzle) Re profile for algorithm using ARM radar- CERES team? lidar, and comparison with aircraft data. Re is a critical for radiation Wu et al. (2020), JGR and aerosol-cloud- precipitation interactions, as well as warm rain process. 1 A long-term Issue: CERES Re is too large, especially under drizzling MBL clouds A/C obs in N Atlantic • Cloud droplet size retrievals generally too high low clouds • Especially large for Re(1.6, 2.1 µm) CERES Re too large Worse for larger Re • Cloud heterogeneity plays a role, but drizzle may also be a factor - Can we understand the impact of drizzle on these NIR retrievals and their differences with Painemal et al. 2020 ground truth? A/C obs in thin Pacific Sc with drizzle CERES LWP high, tau low, due to large Re Which will lead to high SW transmission at the In thin drizzlers, Re is overestimated by 3 µm surface and less albedo at TOA Wood et al. JAS 2018 Painemal et al. JGR 2017 2 Profiles of MBL Cloud and Drizzle Microphysical Properties retrieved from Ground-based Observations and Validated by Aircraft data during ACE-ENA IOP 푫풎풂풙 ퟔ Radar reflectivity: 풁 = ퟎ 푫 푵풅푫 Challenge is to simultaneously retrieve both cloud and drizzle properties within an MBL cloud layer using radar-lidar observations because radar reflectivity depends on the sixth power of the particle size and can be highly weighted by a few large drizzle drops in a drizzling cloud 3 Wu et al. -
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.