DOCSLIB.ORG

Static Stability Stability in the Atmosphere

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Static Stability Stability in the Atmosphere MTO 412E Physics of Cloud and Precipitation Objectives • Be able to provide the definition of stability Static Stability and Cloud • Be able to describe the two methods by Development which air is displace • Be able to identify the types of clouds that form during either forced ascent or auto - convective ascent • Be able to determine if the atmosphere is potentially unstable Static Stability and Environmental Lapse Why is stability important? Rate (ELR) • Vertical motions in the atmosphere are a critical • Static Stability part of energy transport and strongly influence the • Absolutely Unstable Air hydrologic cycle • Absolutely Stable Air • Without vertical motion, there would be no precipitation, no mixing of pollutants away from • Conditionally Unstable Air ground level - weather as we know it would simply not exist. • There are two types of vertical motion: – forced motion such as forcing air up over a hill, over colder air, or from horizontal convergence – buoyant motion in which the air rises because it is less dense than its surroundings - stability is especially important here Static Stability Stability in the atmosphere • Static stability – The air’s susceptibility to lift. – Unstable – Air will continue to rise if given an initial upwards push – Stable – Air resists the upward displacement An Initial Stable Unstable Neutral and sinks back to original level. Perturbation – Neutral – Air will neither rise on its own or sink back to its original level. If an air parcel is displaced from its original height it can: Return to its original height - Stable Accelerate upward because it is buoyant - Unstable Stay at the place to which it was displaced - Neutral 1 uoyancy Buoyancy Static Stability is Related to Buoyancy Parcel of Air • An air parcel rises in the atmosphere when it’s density is Less dense Than Surrounding Air: Positive Buoyancy less than its surroundings Tends to Rise (Warmer) • Let env be the density of the environment. From the More dense Than Surrounding Air: Negative Buoyancy Equation of State/Ideal Gas Law Tends to Sink if Not Lifted(Colder) env = P/ RT env A Rising Parcel of Air • Let parcel be the density of an air parcel. Then Stops Rising When It Cools to Surrounding Air parcel = P/ RT parcel • Since both the parcel and the environment at the same Sinks When It Becomes Colder Than Surrounding Air height are at the same pressure This Suppresses Uplift – when Tparcel > Tenv parcel < env (positive buoyancy ) – when Tparcel < Tenv parcel > env (negative buoyancy ) Rising Air What is lapse rate? Cools The lapse rate is the change of temperature • The lapse rate is the change of temperature with • Rising air with altitude. parcels expand height in the atmosphere • Work done by The atmospheric dry • There are two kinds of lapse rates: adiabatic air molecules in – Environmental Lapse Rate the parcel lapse rate is ~ • What you would measure with a weather balloon pushing 5.4 F/1000 ft outward or – Parcel Lapse Rate consumes 10 C/1000 m • The change of temperature that an air parcel would experience energy and when it is displaced vertically The actual, • This is assumed to be an adiabatic process (i.e ., no heat lowers the environmental lapse parcel rate may be greater exchange occurs across parcel boundary) temperature or smaller than this Lapse Rates Trading Height for Heat Lifted Parcel of Air There are two kinds of “static” energy in the Cools at One of the Adiabatic Lapse Rates Air Around it Maintains Its Original Temperature Profile parcel: potential energy (due to its height) and enthalpy (due to the motions of the molecules Relative Density 1. Depends on Unsaturated or Saturated that make it up) DALP or SALP 2. Environmental Lapse Rate (ELP) S = c ∆ T +∆ gz Three Types of Static Stability p 1. Absolutely Unstable Air Change in Change in Change in 2. Absolutely Stable Air gravitational static energy enthalpy 3. Conditionally Stable Air potential energy 2 Trading Height for Heat (cont’d) • Suppose a parcel exchanges no energy with Lapse Rates its surroundings … we call this state adiabatic, meaning, “not gaining or losing • Dry adiabatic lapse rate (DALR) –Rate at which rising parcel of unsaturated air cools. (1.0°C/100 energy” 0 =c ∆ T + gz ∆ m) p • Saturated adiabatic lapse rate (SALR) - Rate at c∆ T =− gz ∆ which rising parcel of unsaturated air cools. p (0.5°C/100 m) ∆T g • Dew point lapse rate – Rate at which dew point = − decreases with height. (0.2°C/100 m) ∆z c p • Environmental lapse rate (ELR) – Vertical change in temperature profile through still air. .)ry adiabatic lapse rate” Lapse Rates Lapse Rates • Difference between ELR and DALR/SALR Stability and the Reversible Process dry adiabatic lapse rate • Atmospheric stability depends on the environmental lapse rate – A rising unsaturated air parcel cools according to the dry adiabatic lapse rate – If this air parcel is • warmer than surrounding air it is less dense and buoyancy accelerates the parcel upward • colder than surrounding air it is more dense and buoyancy forces oppose the rising motion 3 A saturated rising air parcel cools Stability and the less than an moist adiabatic lapse rate • Atmospheric stability unsaturated parcel depends on the environmental lapse rate • If a rising air parcel becomes saturated condensation – A rising saturated air parcel cools according to the moist occurs adiabatic lapse rate • Condensation warms the air parcel due to the – When the environmental lapse release of latent heat rate is smaller than the moist adiabatic lapse rate, the • So, a rising parcel cools less if it is saturated atmosphere is termed dry absolutely stable • Define a moist adiabatic lapse rate • Recall that the dry adiabatic – ~ 6 C/1000 m lapse rate is larger than the – Not constant (varies from ~ 3 -9 C) moist – depends on T and P – What types of clouds do you expect to form if saturated air is forced to rise in an absolutely stable atmosphere? 0actors Influencing the Heating or Cooling of the Lower Environmental Lapse Rate Atmosphere The Average Environmental Lapse Rate (ELR) -0.65 °C / 100 meters ( -6.5 °C / km) Highly Variable in Space and Time Both Surface Air Temperature Vertical Temperature Profile Influences 1. Heating or Cooling of the Lower Atmosphere. Atmosphere Is Heated From the Surface 2. Advection of Cold or Warm Air at Different Levels. ELR Is Steeper (More Change in Temperature) at Mid -day 3. Advection of a Different Air Mass with a Different ELR. Greatest on Clear Days Least at Night Inversion - If Air at Surface Gets Colder Than Aloft Positive ELR Advection of Cold or Warm Air at Advection of a Different Air Mass Different Levels with a Different ELR Air Mass Large Area Distinguished From Its Neighbors by Differences i n Advection or Wind Can Be Different at the Surface From That Alof t 1. Temperature ELR Can Be Different If Winds Are Different 2. Water Content (Humidity) Example Same Direction: -0.5°c/100m Maintain Their Identity (1 & 2) Perpendicular : -1.0°c/100m Air Masses Can Migrate Into Other Large Areas Changing ELR Idealized Example As Winds Gradually Change With Height (A takes the place of B) Seen by Cloud Movement 4 Limitations on Lifting Unstable Air Advection of Cold and Warm Air Stable Unstable Unstable Air Can Not Lift Forever Braking Mechanisms 1. Ascent Into Layer of Stable Air 2. Entrainment (Advection of Warmer Air) Advection of Cold and Warm Air Static Stability Static Stability Air’s Susceptibility to Uplift. Statically Unstable Air Continues to Rise If Given an Initial Upward Push Statically Stable Air Resists Upward Displacement and Sinks Back to Original Level Statically Neutral Air Will not Rise or Sink After Its Initial Upward Push Comes to Rest Where It was Displaced Stability Psychological Instability • Psychological Stability • Results From Stress • Meteorological Stability – Too many Exams – Too Much Homework – Poor Grades – Too Much Alcohol • Example 5 Meteorological Stability Stability • The ability of the air to return to its origin • Depends on the after displacement thermal structure of the atmosphere Stability Stable • Can be classified into 3 categories • Returns to original position after – Stable displacement – Neutral – Unstable Neutral Unstable • Remains in new position after being • Moves farther away from its original displaced position 6 Stability Forced Ascent • How is air displaced? • Some mechanism forces air aloft – Two methods – Usually synoptic scale feature 1.) Forced Ascent 2.) Auto -Convective Ascent Cold air Warm air Cool Air Forced Ascent Auto-Convective Ascent • Type of clouds • Air becomes buoyant – Depends on stability by contact with warm ground – Usually microscale or mesoscale Stable - Stratus Unstable - Cumulus Cool Hot Cool Auto-Convective Ascent Parcel Theory • Type of Clouds • Assumptions T ,P T ,P – Cumulus – Thermally insulated from its e p environment – Temperature changes w adiabatically – Always at the same pressure as the environment at that level 7 Parcel Theory Stability • Assumptions • As parcel rises T ,P T ,P – Hydrostatic equilibrium e p 1.) Parcel Temperature – Moving slow enough that its Changes kinetic energy is a negligible w • Unsaturated? – Dry Adiabatic Lapse Rate Stability Stability Pseudo - Adiabat Mixing Ratio line • As parcel rises 4 1.) Parcel Temperature Unsaturated Changes 3 Parcel • Saturated? Temperature 2 – Pseudoadiabatic Lapse Dry Rate 1 Adiabat Height (km) Height Height (km) Height 0 -20 -10 0 10 20 Temperature (°C) Stability Stability Pseudo - Adiabat Mixing Ratio line • As parcel rises 4 2.) Environmental Saturated
Load more

Recommended publications
  • Impacts of Anthropogenic Aerosols on Fog in North China Plain
    BNL-209645-2018-JAAM Journal of Geophysical Research: Atmospheres RESEARCH ARTICLE Impacts of Anthropogenic Aerosols on Fog in North China Plain 10.1029/2018JD029437 Xingcan Jia1,2,3 , Jiannong Quan1 , Ziyan Zheng4, Xiange Liu5,6, Quan Liu5,6, Hui He5,6, 2 Key Points: and Yangang Liu • Aerosols strengthen and prolong fog 1 2 events in polluted environment Institute of Urban Meteorology, Chinese Meteorological Administration, Beijing, China, Brookhaven National Laboratory, • Aerosol effects are stronger on Upton, NY, USA, 3Key Laboratory of Aerosol-Cloud-Precipitation of China Meteorological Administration, Nanjing University microphysical properties than of Information Science and Technology, Nanjing, China, 4Institute of Atmospheric Physics, Chinese Academy of Sciences, macrophysical properties Beijing, China, 5Beijing Weather Modification Office, Beijing, China, 6Beijing Key Laboratory of Cloud, Precipitation and • Turbulence is enhanced by aerosols during fog formation and growth but Atmospheric Water Resources, Beijing, China suppressed during fog dissipation Abstract Fog poses a severe environmental problem in the North China Plain, China, which has been Supporting Information: witnessing increases in anthropogenic emission since the early 1980s. This work first uses the WRF/Chem • Supporting Information S1 model coupled with the local anthropogenic emissions to simulate and evaluate a severe fog event occurring Correspondence to: in North China Plain. Comparison of the simulations against observations shows that WRF/Chem well X. Jia and Y. Liu, reproduces the general features of temporal evolution of PM2.5 mass concentration, fog spatial distribution, [email protected]; visibility, and vertical profiles of temperature, water vapor content, and relative humidity in the planetary [email protected] boundary layer throughout the whole period of the fog event.
    [Show full text]
  • GEOGRAPHY OPTIONAL by SHAMIM ANWER
    GEOGRAPHY OPTIONAL by SHAMIM ANWER LEARNING GEOGRAPHY - A NEVER BEFORE EXPERIENCE PREP SUPPLEMENT CLIMA T OLOGY NOT FOR SALE | Off : 57/17 1st Floor, Old Rajender Nagar 8026506054, 8826506099 | Above Dr, Batra’s Delhi - 110060 Also visit us on www.keynoteias.com | www.facebook.com/keynoteias.in KEYNOTE IAS PHYSICAL GEOGRAPHY CLIMATOLOGY INDEX 1. CIRCULATION OF THE ATMOSPHERE ................................................................1-13 Local Winds; Observed Distribution of Pressure and Winds and Idealized Zonal Pressure Belts; Monsoons, Westerlies and Jet Streams; EL Nino and La Nina. 2. MOISTURE AND ATMOSPHERIC STABILITY ..................................................14-24 Atmospheric Stability and Instability 3. FORMS OF CONDENSATION AND PRECIPITATION ........................................25-38 Types and Global Distribution of Precipitation 4. AIR MASSES...........................................................................................................39-53 Polar-Front Theory; Fronts; Cyclone Formation; Cyclonic and Anticyclonic Circulation PREP-SUPPLEMENT: CLIMATOLOGY 1 1. CIRCULATION OF THE ATMOSPHERE Atmospheric circulation and wind Macroscale Winds: The largest wind patterns, called macroscale winds, are exemplified by the Winds are generated by pressure differences that westerlies and trade winds. These planetary-scale arise because of unequal heating of Earth's surface. flow patterns extend around the entire globe and Global winds are generated because the tropics can remain essentially unchanged for weeks at
    [Show full text]
  • Atmospheric Stability Atmospheric Lapse Rate
    ATMOSPHERIC STABILITY ATMOSPHERIC LAPSE RATE The atmospheric lapse rate ( ) refers to the change of an atmospheric variable with a change of altitude, the variable being temperature unless specified otherwise (such as pressure, density or humidity). While usually applied to Earth's atmosphere, the concept of lapse rate can be extended to atmospheres (if any) that exist on other planets. Lapse rates are usually expressed as the amount of temperature change associated with a specified amount of altitude change, such as 9.8 °Kelvin (K) per kilometer, 0.0098 °K per meter or the equivalent 5.4 °F per 1000 feet. If the atmospheric air cools with increasing altitude, the lapse rate may be expressed as a negative number. If the air heats with increasing altitude, the lapse rate may be expressed as a positive number. Understanding of lapse rates is important in micro-scale air pollution dispersion analysis, as well as urban noise pollution modeling, forest fire-fighting and certain aviation applications. The lapse rate is most often denoted by the Greek capital letter Gamma ( or Γ ) but not always. For example, the U.S. Standard Atmosphere uses L to denote lapse rates. A few others use the Greek lower case letter gamma ( ). Types of lapse rates There are three types of lapse rates that are used to express the rate of temperature change with a change in altitude, namely the dry adiabatic lapse rate, the wet adiabatic lapse rate and the environmental lapse rate. Dry adiabatic lapse rate Since the atmospheric pressure decreases with altitude, the volume of an air parcel expands as it rises.
    [Show full text]
  • Atmospheric Thermal and Dynamic Vertical Structures of Summer Hourly Precipitation in Jiulong of the Tibetan Plateau
    atmosphere Article Atmospheric Thermal and Dynamic Vertical Structures of Summer Hourly Precipitation in Jiulong of the Tibetan Plateau Yonglan Tang 1, Guirong Xu 1,*, Rong Wan 1, Xiaofang Wang 1, Junchao Wang 1 and Ping Li 2 1 Hubei Key Laboratory for Heavy Rain Monitoring and Warning Research, Institute of Heavy Rain, China Meteorological Administration, Wuhan 430205, China; [email protected] (Y.T.); [email protected] (R.W.); [email protected] (X.W.); [email protected] (J.W.) 2 Heavy Rain and Drought-Flood Disasters in Plateau and Basin Key Laboratory of Sichuan Province, Institute of Plateau Meteorology, China Meteorological Administration, Chengdu 610072, China; [email protected] * Correspondence: [email protected]; Tel.: +86-27-8180-4913 Abstract: It is an important to study atmospheric thermal and dynamic vertical structures over the Tibetan Plateau (TP) and their impact on precipitation by using long-term observation at represen- tative stations. This study exhibits the observational facts of summer precipitation variation on subdiurnal scale and its atmospheric thermal and dynamic vertical structures over the TP with hourly precipitation and intensive soundings in Jiulong during 2013–2020. It is found that precipitation amount and frequency are low in the daytime and high in the nighttime, and hourly precipitation greater than 1 mm mostly occurs at nighttime. Weak precipitation during the daytime may be caused by air advection, and strong precipitation at nighttime may be closely related with air convection. Both humidity and wind speed profiles show obvious fluctuation when precipitation occurs, and the greater the precipitation intensity, the larger the fluctuation. Moreover, the fluctuation of wind speed Citation: Tang, Y.; Xu, G.; Wan, R.; Wang, X.; Wang, J.; Li, P.
    [Show full text]
  • Atmospheric Instability Parameters Derived from Msg Seviri Observations
    P3.33 ATMOSPHERIC INSTABILITY PARAMETERS DERIVED FROM MSG SEVIRI OBSERVATIONS Marianne König*, Stephen Tjemkes, Jochen Kerkmann EUMETSAT, Darmstadt, Germany 1. INTRODUCTION K-Index: Convective systems can develop in a thermo- (Tobs(850)–Tobs(500)) + TDobs(850) – (Tobs(700)–TDobs(700)) dynamically unstable atmosphere. Such systems may quickly reach high altitudes and can cause severe Lifted Index: storms. Meteorologists are thus especially interested to Tobs - Tlifted from surface at 500 hPa identify such storm potentials when the respective system is still in a preconvective state. A number of Maximum buoyancy: obs(max betw. surface and 850) obs(min betw. 700 and 300) instability indices have been defined to describe such Qe - Qe situations. Traditionally, these indices are taken from temperature and humidity soundings by radiosondes. As (T is temperature, TD is dewpoint temperature, and Qe radiosondes are only of very limited temporal and is equivalent potential temperature, numbers 850, 700, spatial resolution there is a demand for satellite-derived 300 indicate respective hPa level in the atmosphere) indices. The Meteorological Product Extraction Facility (MPEF) for the new European Meteosat Second and the precipitable water content as additionally Generation (MSG) satellite envisages the operational derived parameter. derivation of a number of instability indices from the brightness temperatures measured by certain SEVIRI 3. DESCRIPTION OF ALGORITHMS channels (Spinning Enhanced Visible and Infrared Imager, the radiometer onboard MSG). The traditional 3.1 The Physical Retrieval physical approach to this kind of retrieval problem is to infer the atmospheric profile via a constrained inversion An iterative solution to the inversion equation (e.g. and compute the indices then directly from the obtained Ma et al.
    [Show full text]
  • Static Stability (I) the Concept of Stability (Ii) the Parcel Technique (A
    ATSC 5160 – supplement: static stability Static stability (i) The concept of stability The concept of (local) stability is an important one in meteorology. In general, the word stability is used to indicate a condition of equilibrium. A system is stable if it resists changes, like a ball in a depression. No matter in which direction the ball is moved over a small distance, when released it will roll back into the centre of the depression, and it will oscillate back and forth, until it eventually stalls. A ball on a hill, however, is unstably located. To some extent, a parcel of air behaves exactly like this ball. Certain processes act to make the atmosphere unstable; then the atmosphere reacts dynamically and exchanges potential energy into kinetic energy, in order to restore equilibrium. For instance, the development and evolution of extratropical fronts is believed to be no more than an atmospheric response to a destabilizing process; this process is essentially the atmospheric heating over the equatorial region and the cooling over the poles. Here, we are only concerned with static stability, i.e. no pre-existing motion is required, unlike other types of atmospheric instability, like baroclinic or symmetric instability. The restoring atmospheric motion in a statically stable atmosphere is strictly vertical. When the atmosphere is statically unstable, then any vertical departure leads to buoyancy. This buoyancy leads to vertical accelerations away from the point of origin. In the context of this chapter, stability is used interchangeably
    [Show full text]
  • Analysis of Stability Parameters in Relation to Precipitation Associated with Pre-Monsoon Thunderstorms Over Kolkata, India
    Analysis of stability parameters in relation to precipitation associated with pre-monsoon thunderstorms over Kolkata, India H P Nayak and M Mandal∗ Centre for Oceans, Rivers, Atmosphere and Land Sciences, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India ∗Corresponding author. e-mail: [email protected] The upper air RS/RW (Radio Sonde/Radio Wind) observations at Kolkata (22.65N, 88.45E) during pre- monsoon season March–May, 2005–2012 is used to compute some important dynamic/thermodynamic parameters and are analysed in relation to the precipitation associated with the thunderstorms over Kolkata, India. For this purpose, the pre-monsoon thunderstorms are classified as light precipitation (LP), moderate precipitation (MP) and heavy precipitation (HP) thunderstorms based on the magnitude of associated precipitation. Richardson number in non-uniformly saturated (Ri*) and saturated atmosphere (Ri); vertical shear of horizontal wind in 0–3, 0–6 and 3–7 km atmospheric layers; energy-helicity index (EHI) and vorticity generation parameter (VGP) are considered for the analysis. The instability measured ∗ in terms of Richardson number in non-uniformly saturated atmosphere (Ri ) well indicate the occurrence of thunderstorms about 2 hours in advance. Moderate vertical wind shear in lower troposphere (0–3 km) and weak shear in middle troposphere (3–7 km) leads to heavy precipitation thunderstorms. The wind shear in 3–7 km atmospheric layers, EHI and VGP are good predictors of precipitation associated with thunderstorm. Lower tropospheric wind shear and Richardson number is a poor discriminator of the three classified thunderstorms. 1. Introduction high socio-economic impact, thunderstorms are of serious concern to researchers and meteorologists.
    [Show full text]
  • Subseasonal and Diurnal Variability in Lightning and Storm Activity Over the Yangtze River Delta, China, During Mei-Yu Season
    15 JUNE 2020 Y A N G E T A L . 5013 Subseasonal and Diurnal Variability in Lightning and Storm Activity over the Yangtze River Delta, China, during Mei-yu Season a,b,c a,b d,e a,b c JI YANG, KUN ZHAO, XINGCHAO CHEN, ANNING HUANG, YUANYUAN ZHENG, AND a,b,c KANGYUAN SUN a Key Laboratory for Mesoscale Severe Weather/Ministry of Education and School of Atmospheric Science, Nanjing University, Nanjing, China b State Key Laboratory of Severe Weather and Joint Center for Atmospheric Radar Research of the China Meteorological Administration and Nanjing University, Beijing, China c Jiangsu Research Institute of Meteorological Sciences, Nanjing, China d Department of Meteorology and Atmospheric Science, The Pennsylvania State University, University Park, Pennsylvania e Center for Advanced Data Assimilation and Predictability Techniques, The Pennsylvania State University, University Park, Pennsylvania (Manuscript received 20 June 2019, in final form 16 March 2020) ABSTRACT Using 5 years of operational Doppler radar, cloud-to-ground (CG) lightning observations, and National Centers for Environmental Prediction reanalysis data, this study examined the spatial and temporal char- acteristics of and correlations between summer storm and lightning activity over the Yangtze River Delta (YRD), with a focus on subseasonal variability and diurnal cycles. The spatiotemporal features of storm top, duration, maximum reflectivity, size, and cell-based vertical integrated liquid water were investigated using the Storm Cell Identification and Tracking algorithm. Our results revealed that there was high storm activity over the YRD, with weak diurnal variations during the mei-yu period. Specifically, storms were strongly associated with mei-yu fronts and exhibited a moderate size, duration, and intensity.
    [Show full text]
  • Teaching Weather and Climate Buoyancy and Vertical Motion Scott
    Teaching Weather and Climate Buoyancy and Vertical Motion Thermodynamics, Buoyancy, and Vertical Motion Temperature, Pressure, and Density Buoyancy and Static Stability Adiabatic “Lapse Rates” Dry and Moist Convective Motions Present Atmospheric Composition What is Air Temperature? • Temperature is a measure of the kinetic (motion) energy of air molecules – K.E. = ½ mv2 m = mass, v = velocity – So…temperature is a measure of air molecule speed • The sensation of warmth is created by air molecules striking and bouncing off your skin surface – The warmer it is, the faster molecules move in a random fashion and the more collisions with your skin per unit time Scott Denning CSU CMMAP 1 Teaching Weather and Climate Buoyancy and Vertical Motion Temperature Scales • In the US, we use Fahrenheit most often • Celsius (centigrade) is a scale based on freezing/boiling of water • Kelvin is the “absolute” temperature scale How do we measure temperature? • Conventional thermometry - Liquid in glass. • Electronic thermometers - Measures resistance in a metal such as nickel. • Remote sensing using radiation emitted by the air and surface (by satellites or by you in this class!). What is the coldest possible temperature? Why? Atmospheric Soundings Helium-filled weather balloons are released from over 1000 locations around the world every 12 hours (some places more often) These document temperature, pressure, humidity, and winds aloft Scott Denning CSU CMMAP 2 Teaching Weather and Climate Buoyancy and Vertical Motion Pressure • Pressure is defined as a force applied per unit area • The weight of air is a force, equal to the mass m times the acceleration due to gravity g • Molecules bumping into an object also create a force on that object, or on one another • Air pressure results from the weight of the entire overlying column of air! How do we measure pressure? Sea Level Value Units of Pressure: (average) 1 atmosphere 760 mm.
    [Show full text]
  • Sea Surface Temperature–Precipitation Relationship in Different Reanalyses
    1118 MONTHLY WEATHER REVIEW VOLUME 141 Sea Surface Temperature–Precipitation Relationship in Different Reanalyses ARUN KUMAR Climate Prediction Center, NOAA/NWS/NCEP, College Park, Maryland LI ZHANG Climate Prediction Center, NOAA/NWS/NCEP, College Park, Maryland, and Wyle Science, Technology, and Engineering, McLean, Virginia WANQIU WANG Climate Prediction Center, NOAA/NWS/NCEP, College Park, Maryland (Manuscript received 2 August 2012, in final form 22 November 2012) ABSTRACT The focus of this investigation is how the relationship at intraseasonal time scales between sea surface temperature and precipitation (SST–P) varies among different reanalyses. The motivation for this work was spurred by a recent report that documented that the SST–P relationship in Climate Forecast System Re- analysis (CFSR) was much closer to that in the observation than it was for the older generation of reanalyses [i.e., NCEP–NCAR reanalysis (R1) and NCEP–Department of Energy (DOE) reanalysis (R2)]. Further, the reason was attributed either to the fact that the CFSR is a partially coupled reanalysis, while R1 and R2 are atmospheric-alone reanalyses, or that R1 and R2 use the observed weekly-averaged SST. The authors repeated the comparison of the SST–P relationship among R1, R2, and CFSR, as well as two recent generations of atmosphere-alone reanalyses, the Modern-Era Retrospective Analysis for Research and Applications (MERRA) and the ECMWF Re-Analysis Interim (ERA-Interim). The results clearly demonstrate that the differences in the SST–P relationship at intraseasonal time scales across different reanalyses are not due to whether the reanalysis system is coupled or atmosphere alone, but are due to the specification of different SSTs.
    [Show full text]
  • Atmospheric Instability As a Loss of a Metastable Equilibrium
    Atmospheric instability as a loss of a metastable equilibrium Yuri Kornyushin Maître Jean Brunschvig Research Unit, Chalet Shalva, Randogne, CH-3975 Abstract. General thermodynamic theory of metastable states is used in this short note to try to understand better atmospheric instabilities. It is shown that not only cooling of a cloud can lead to rain, but heating also, especially when there are charged water drops in a cloud (in this case we have rain with lightning). The influence of the global warming on weather is discussed. 1. Introduction Metastable state in Classical Mechanics is a very well known one and it is shown on Fig. 1, which presents a schematic dependence of mechanical energy E on some parameter X (generalized coordinate). Metastable state (1) exists in a shallow minimum of mechanical energy. It is separated from more stable state (3) by a relatively low barrier (2). As the barrier is relatively low, the equilibrium in position (1) can be easily unstable. Fig. (1). Metastable state (1) in a shallow minimum of the energy in Classical Mechanics. It is separated from more stable state (3) by rather low barrier (2). Parameter X represents some generalized coordinate. Metastable states in Classical Thermodynamics were very well known quite a long time ago (see, e.g. [1]). The specific feature of the metastable state in Classical Thermodynamics is that there exists some virtual critical point (temperature of the absolute instability), Ti. At this temperature the thermodynamic barrier, separating a metastable state from more stable one, does not exist. The matter is that the height of the barrier mentioned depends on temperature, T, and ceases to exist at T = Ti (see, e.g., [2,3]).
    [Show full text]
  • Clouds and Atmospheric Convection
    Clouds and atmospheric convection Caroline Muller CNRS/Laboratoire de Météorologie Dynamique (LMD) Département de Géosciences ENS 1 M2 P7/ IPGP Clouds and atmospheric convection 2 Clouds and atmospheric convection 3 Clouds and atmospheric convection Intertropical Convergence Zone 4 Clouds and atmospheric convection 1. Cloud types 2. Moist thermodynamics and stability 3. Coupling with circulation 5 1. Cloud types Cumulus: heap, pile Stratus: flatten out, cover with a layer Cirrus: lock of hair, tuft of horsehair Combined to define 10 cloud types Nimbus: precipitating cloud Altum: height 6 1. Cloud types Clouds are classified according to height of cloud base and appearance High clouds Base: 5 to 12km Middle clouds Base: 2 to 6km Low clouds Base < 2km 7 1. High Clouds Almost entirely ice crystals Cirrus Wispy, feathery Cirrocumulus Layered clouds, cumuliform lumpiness Cirrostratus Widespread, sun/moon halo 8 1. Middle Clouds Liquid water droplets, ice crystals, or a combination of the two, including supercooled droplets (i.e., liquid droplets whose temperatures are below freezing). Altocumulus Heap-like clouds with convective elements in mid levels May align in rows or streets of clouds Altostratus Flat and uniform type texture in mid levels 9 1. Low Clouds Liquid water droplets or even supercooled droplets, except during cold winter storms when ice crystals (and snow) comprise much of the clouds. The two main types include stratus, which develop horizontally, and cumulus, which develop vertically. Stratocumulus Hybrids of layered stratus and cellular cumulus Stratus Uniform and flat, producing a gray layer of cloud cover Nimbostratus Thick, dense stratus or stratocumulus clouds producing steady rain or snow 10 1.
    [Show full text]