DOCSLIB.ORG

Shifting Westerlies to Shift After the Last Glacial Period? J

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Shifting Westerlies to Shift After the Last Glacial Period? J PERSPECTIVES CLIMATE CHANGE What caused atmospheric westerly winds Shifting Westerlies to shift after the last glacial period? J. R. Toggweiler he westerlies are the prevailing ica-rich deep water must be drawn to the sur- winds in the middle latitudes of face. As mentioned above, silica-rich deep Earth’s atmosphere, blowing water tends to be high in CO . It is also T 2 from west to east between the high- warmer than the near-freezing surface pressure areas of the subtropics and waters around Antarctica. the low-pressure areas over the poles. A shift of the westerlies that draws They have strengthened and shifted more warm, silica-rich deep water to poleward over the past 50 years, pos- the surface is thus a simple way to sibly in response to warming from explain the CO2 steps, the silica pulses, rising concentrations of atmospheric and the fact that Antarctica warmed carbon dioxide (CO2) (1–4). Some- along with higher CO2 during the two thing similar appears to have happened steps. Anderson et al.’s two silica pulses 17,000 years ago at the end of the last ice occur right along with the two CO2 steps, age: Earth warmed, atmospheric CO2 in- which implies that the westerlies shifted creased, and the Southern Hemisphere wester- early as the level of CO2 in the atmosphere lies seem to have shifted toward Antarctica began to rise. Had the westerlies shifted in (5, 6). Data reported by Anderson et al. on response to higher CO , one would expect to Southward movement. At the end of the last ice 2 page 1443 of this issue (7) suggest that the see more upwelling and more silica accumula- on October 23, 2009 age, the ITCZ and the Southern Hemisphere wester- shift 17,000 years ago occurred before the lies winds moved southward in response to a flatter tion after the second CO2 step when the level of warming and that it caused the CO2 increase. temperature contrast between the hemispheres (5, CO2 is highest, but instead the silica accumula- The CO2 that appeared in the atmosphere 6, 11). According to Anderson et al., the northern tion drops back down. 17,000 years ago came from the oceans rather westerlies may have also shifted to the south; this What made the westerlies shift when they than from anthropogenic emissions. It was shift is not depicted in the figure. did? The answer seems obvious empirically vented from the deep ocean up to the atmo- but may be difficult to understand theoreti- sphere in the vicinity of Antarctica. The south- the ACC to the surface around Antarctica. Over cally. The Northern Hemisphere is systemati- ern westerlies are important in this context the past 50 years, the westerlies have shifted cally warmer than the Southern Hemisphere, because they can alter the oceanic circulation southward so that they are better aligned with especially near the Atlantic Ocean, where the www.sciencemag.org in a way that vents CO2 from the ocean inte- the ACC and draw more mid-depth water to the overturning circulation transports heat across rior up to the atmosphere. The prevailing view surface than they did before (8, 9). At the peak the equator from south to north. As a result, has been that the westerlies shifted 17,000 of the last ice age, the opposite situation pre- Earth’s thermal equator—the Intertropical years ago as part of a feedback: A small CO2 vailed: The westerlies were so far north of Convergence Zone (ITCZ)—is north of the increase or small warming initiated a shift of today’s position that they were no longer equator. The easterly trade winds that flank the the westerlies toward Antarctica; the shifted aligned with the ACC and could not draw much ITCZ to the north and south are also skewed westerlies then caused more CO2 to be vented mid-depth water to the surface. toward the Northern Hemisphere. Downloaded from up to the atmosphere, which led to more The mid-depth water upwelled by the Anderson et al.’s two pulses of sediment warming, a greater poleward shift of the west- westerlies is rich in CO2 and in silica, a nutri- accumulation took place along with Heinrich erlies, more CO2, and still more warming (5). ent that fuels biological production in the sur- Event 1 and the Younger Dryas—events in But Anderson et al. show that the westerlies face waters around Antarctica. Siliceous which icebergs and melting glaciers flooded did not shift in response to an initial CO2 remains of the organisms settle to the sea floor the North Atlantic with fresh water, thereby increase; rather, they shifted early in the cli- and accumulate in the sediments. Anderson et weakening the overturning. The weakened mate transition and were probably the main al. show that the accumulation of siliceous overturning cooled the Northern Hemisphere cause of the initial CO2 increase. sediment increased dramatically during the and warmed the Southern Hemisphere, The strongest southern westerlies are found transition out of the last ice age. They attribute thus reducing the temperature asymmetry. several hundred kilometers to the north of a this increase to a poleward shift of the wester- Sediment records from the southern Caribbean broad oceanic channel that circles the globe lies that drew more CO2- and silica-rich water Sea show that the trade winds shifted to the around Antarctica. The stress from the wester- up to the surface. south during the two pulses (11, 12). Thus, the lies on the ocean drives the Antarctic Circum- A detailed analysis of the ice-core records ITCZ shifted closer to the equator and the polar Current (ACC) through the channel. This from Antarctica shows that atmospheric CO2 southern westerlies apparently shifted toward stress also draws mid-depth water from north of concentrations rose in two steps along with the Antarctica along with the southward move- air temperatures over Antarctica (10). The silica ment of the trade winds (see the figure). accumulation in Anderson et al.’s best resolved The sediment accumulation rate during Geophysical Fluid Dynamics Laboratory/National Oceanic record also shows two pulses that correspond in Anderson et al.’s two pulses was five times as and Atmospheric Administration, Princeton University, Princeton, NJ 08540, USA. E-mail: robbie.toggweiler@ time to the two steps (7). To create such a pulse high as it was at the Last Glacial Maximum noaa.gov in silica accumulation, larger quantities of sil- (just before the two pulses), and twice as high J. TOGGWEILER/CARNEGIE MELLON UNIVERSITY CREDIT: 1434 13 MARCH 2009 VOL 323 SCIENCE www.sciencemag.org Published by AAAS PERSPECTIVES as it is today. This points to massive changes in in the Southern Hemisphere than in the References 1. J. W. Hurrell, H. van Loon, Tellus Ser. A 46, 325 (1994). the wind-driven upwelling around Antarctica north (3). The results of Anderson et al. (7) 2. G. J. McCabe et al., J. Climate 14, 2763 (2001). during the transition out of the last ice age and suggest that in the past, the westerlies 3. N. P. Gillett et al., Nature 422, 292 (2003). suggests that the westerlies were closer to (or shifted asymmetrically toward the south in 4. D. T. Shindell, G. A. Schmidt, Geophys. Res. Lett. 31, L18209 (2004). stronger next to) Antarctica during the transi- response to a flatter temperature contrast 5. J. R. Toggweiler, J. L. Russell, S. R. Carson, tion than they are now. between the hemispheres. The magnitude of Paleoceanography 21, PA 2005 (2006). Climate scientists have attributed changes the shift seems to have been very large. If 6. F. Lamy et al., Earth Planet. Sci. Lett. 259, 400 (2007). 7. R. F. Anderson et al., Science 323, 1443 (2009). in the westerlies over the past 50 years to the there was a response to higher CO2 back 6. O. A. Saenko et al., Climate Dyn. 25, 415 (2005). 9. J. L. Russell et al., J. Climate 19, 6382 (2006). warming from higher CO2. The changes pre- then, it paled in comparison. Changes in the dicted by climate models in response to north-south temperature contrast today are 10. E. Monnin et al., Science 291, 112 (2001). 11. G. H. Haug et al., Science 293, 1304 (2001). higher CO2 are fairly small, however, and not going to be as large as they were at the 12. D. W. Lea, D. K. Pak, L. C. Peterson, K. A. Hughen, tend to be symmetric with respect to the end of the last ice age, but even small Science 301, 1361 (2003). equator. The observed changes have been changes could be an additional source of quite asymmetric, with much larger changes modern climate variability. 10.1126/science.1169823 CHEMISTRY Inducing Chirality with Circularly An unexpected difference in electron transfer rates for right- and left-handed versions of a Polarized Light molecule is caused by quantum interference. Robert J. Cave on October 23, 2009 e have an intuitive understanding the rate will be faster the more the donor and bridge (the solid line). In this tight-binding of how the shape and symmetry of acceptor states delocalize onto the bridge low- model, reversing the helicity of the bridge Wobjects affects their use from our ering the effective mass of the electron and while preserving the bonding strength and rel- hands. Each hand is chiral: Its mirror image leading to more efficient tunneling. ative energetics would yield equivalent elec- (the right versus the left hand) is different This delocalization is enhanced when tron transfer rates through the two possible from it. When we extend right hands, they can bonding is strong between the donor, accep- bridge helicities.
Load more

Recommended publications
  • Ocean Currents and the Pacific Garbage Patch
    ocean currents and the Pacific Garbage Patch photo: Scripps Institution of Oceanography The image above shows a net tow sample from the Pacific Garbage Patch. The sample contains small fish and many small pieces of plastic. The Garbage Patch is primarily composed of this small plastic “confetti” suspended throughout the surface water of the North Pacific Gyre, and is not a island of trash as suggested by some media outlets. The region where the trash converges in the center of the North Pacific Gyre, in a region where surface currents are weak and convergent, thus concentrating large amounts of trash in an area estimated to be close to the size of Texas. With this slide I often show a video clip about the Garbage Patch. Although the links may change, here is one from ABC that I’ve used several times: www.youtube.com/watch?v=OFMW8srq0Qk this video is a bit over the top but it gets the point across. There is additional information from Scripps Institution of Oceanography SEAPLEX experiment: http://sio.ucsd.edu/Expeditions/Seaplex/ and several videos on youtube.com by searching the phrase “SEAPLEX” Pacific garbage patch tiny plastic bits • the worlds largest dump? • filled with tiny plastic “confetti” large plastic debris from the garbage patch photo: Scripps Institution of Oceanography little jellyfish photo: Scripps Institution of Oceanography These are some of the things you find in the Garbage Patch. The large pieces of plastic, such as bottles, breakdown into tiny particles. Sometimes animals get caught in large pieces of floating trash: photo: NOAA photo: NOAA photo: Scripps Institution of Oceanography How do plants and animals interact with small small pieces of plastic? fish larvae growing on plastic Trash in the ocean can cause various problems for the organisms that live there.
    [Show full text]
  • Winds in the Lower Cloud Level on the Nightside of Venus from VIRTIS-M (Venus Express) 1.74 Μm Images
    atmosphere Article Winds in the Lower Cloud Level on the Nightside of Venus from VIRTIS-M (Venus Express) 1.74 µm Images Dmitry A. Gorinov * , Ludmila V. Zasova, Igor V. Khatuntsev, Marina V. Patsaeva and Alexander V. Turin Space Research Institute, Russian Academy of Sciences, 117997 Moscow, Russia; [email protected] (L.V.Z.); [email protected] (I.V.K.); [email protected] (M.V.P.); [email protected] (A.V.T.) * Correspondence: [email protected] Abstract: The horizontal wind velocity vectors at the lower cloud layer were retrieved by tracking the displacement of cloud features using the 1.74 µm images of the full Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS-M) dataset. This layer was found to be in a superrotation mode with a westward mean speed of 60–63 m s−1 in the latitude range of 0–60◦ S, with a 1–5 m s−1 westward deceleration across the nightside. Meridional motion is significantly weaker, at 0–2 m s−1; it is equatorward at latitudes higher than 20◦ S, and changes its direction to poleward in the equatorial region with a simultaneous increase of wind speed. It was assumed that higher levels of the atmosphere are traced in the equatorial region and a fragment of the poleward branch of the direct lower cloud Hadley cell is observed. The fragment of the equatorward branch reveals itself in the middle latitudes. A diurnal variation of the meridional wind speed was found, as east of 21 h local time, the direction changes from equatorward to poleward in latitudes lower than 20◦ S.
    [Show full text]
  • 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.
    [Show full text]
  • Global Climate Influencer – Arctic Oscillation
    ARCTIC OSCILLATION GLOBAL CLIMATE INFLUENCER by James Rohman | February 2014 Figure 1. A satellite image of the jet stream. Figure 2. How the jet stream/Arctic Oscillation might affect weather distribution in the Northern Hemisphere. Arctic Oscillation Introduction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
    [Show full text]
  • Globe Lesson 10 - Latitude Zones - Grade 6+ Geographers Divide the Earth Into Latitude Zones
    Globe Lesson 10 - Latitude Zones - Grade 6+ Geographers divide the Earth into latitude zones. There are three latitude zones: - Low latitude zones - Middle latitude zones - High latitude zones There are 90 degrees of latitude. Each zone of latitude is 30 degrees wide. The Equator is 0 degrees. 0 to 30 are low numbers, 30-60 are middle numbers, and 60 to 90 are high numbers. This chart shows the arrangement of the zones in the Northern Hemisphere. Write in high, middle, and low latitude zones in the proper order in the Southern Hemisphere. Remember that the Equator is latitude 0 and the South Pole is latitude 90. Find the 180th meridian on your globe. On this line you will find the numbers of the printed parallels. Find 30 and 60 degrees north latitude. Draw a line of dashes around your globe on these lines. Find 30 and 60 degrees south latitude. Draw a line of dashes on these lines. These parallels divide the latitude zones. Label the zones Low, Middle and High in both the Northern and Southern Hemisphere on your globe. Finding Latitude Zones 4. In the following exercise identify the latitude with the proper latitude zone. "L" stands for low latitudes. "M" stands for middle latitudes. "H" stands for high latitudes. ______ 35°N ______ 23°N ______ 86°N ______ 15°N ______ 5°N ______ 66°N ______ 45°N ______ 28°N 5. In the following exercise, identify each city with the latitude zone where you find it. "L" stands for low latitudes. "M" stands for middle latitudes.
    [Show full text]
  • Monthly Weather Review June1960
    DEPARTMENT OF COMMERCE WEATHER BUREAU FREDERICK H. MUELLER, Secretary F. W.REICHELDERFER, Chief MONTHLYWEATHER REVIEW JAMESE. CASKEY, JR., Editor Volume 88 JUNE 1960 Closed August 15, 1960 Number 6 Issued September 15, 1960 THE SEASONAL VARIATION OF THE STRENGTH OF THE SOUTHERN CIRCUMPOLAR VORTEX W. SCHWERDTFEGER Department of Meteorology, Naval Hydrographic Service, Argentina [Manuscript received May 24, 1960; revised June 20, 19601 ABSTRACT The annual marchof the strengthof the southerncircumpolar. vortexis shown to be composed of a simple annual variation(with the maximumoccurring in late winter)which dominates in thestratosphere, and a semiannual variation with the maximum at the equinoxes, which is the dominating part in the troposphere. This behavior of the circumpolarvortex is considered to be the consequence of the seasonal variation of radiation conditions and of the different efficiency of meridional turbulent exchange in the troposphere and stratosphere. It is suggested that the semiannual variation of the tropospheric vortex is an essential feature of a planetary circulation. The annual march of pressure with opposite phase values at polar and middle latitudes, can be understood as a consequence of the formation and decay of the great circumpolar vortex. 1. INTRODUCTION part of the period which can now be considered. The Some aerological data of the Southern Hemisphere and South Pole station has been taken as representative of the particularly those from the South Pole (Amundsen-Scott inner part of the SCPV, in spiteof the fact that inseveral Station) obtained during theIGY and its extension through months the center of the vortex cannot be found exactly 1959, make it possible for the first time to arrive at an es- over the Pole.
    [Show full text]
  • Surface Circulation2016
    OCN 201 Surface Circulation Excess heat in equatorial regions requires redistribution toward the poles 1 In the Northern hemisphere, Coriolis force deflects movement to the right In the Southern hemisphere, Coriolis force deflects movement to the left Combination of atmospheric cells and Coriolis force yield the wind belts Wind belts drive ocean circulation 2 Surface circulation is one of the main transporters of “excess” heat from the tropics to northern latitudes Gulf Stream http://earthobservatory.nasa.gov/Newsroom/NewImages/Images/gulf_stream_modis_lrg.gif 3 How fast ( in miles per hour) do you think western boundary currents like the Gulf Stream are? A 1 B 2 C 4 D 8 E More! 4 mph = C Path of ocean currents affects agriculture and habitability of regions ~62 ˚N Mean Jan Faeroe temp 40 ˚F Islands ~61˚N Mean Jan Anchorage temp 13˚F Alaska 4 Average surface water temperature (N hemisphere winter) Surface currents are driven by winds, not thermohaline processes 5 Surface currents are shallow, in the upper few hundred metres of the ocean Clockwise gyres in North Atlantic and North Pacific Anti-clockwise gyres in South Atlantic and South Pacific How long do you think it takes for a trip around the North Pacific gyre? A 6 months B 1 year C 10 years D 20 years E 50 years D= ~ 20 years 6 Maximum in surface water salinity shows the gyres excess evaporation over precipitation results in higher surface water salinity Gyres are underneath, and driven by, the bands of Trade Winds and Westerlies 7 Which wind belt is Hawaii in? A Westerlies B Trade
    [Show full text]
  • Waves in the Westerlies
    Operational Weather Analysis … www.wxonline.info Chapter 9 Waves in the Westerlies Operational meteorologists track middle latitude disturbances in the middle to upper troposphere as part of their analysis of the atmosphere. This chapter describes these waves and highlights the importance of these waves to day-to-day weather changes at the Earth’s surface. The Westerlies Atmospheric flow above the Earth’s surface in the middle latitudes is primarily westerly. That is, the winds have a prevailing westerly component with numerous north and south meanders that impose wave-like undulations upon the basic west- to-east flow. This flow extends from the subtropical high pressure belt poleward to around 65 degrees latitude. A glance at any upper level chart from 700 mb upward to 200 mb shows that the westerlies dominate in the middle and upper troposphere. The term westerlies will refer to this layer unless otherwise specified. Upper Level Charts The westerlies are easily identified on charts of constant pressure in the middle to upper troposphere. That is, charts are prepared from upper level data at specified pressure levels (called standard levels). Traditionally, lines are drawn on these charts to represent the height of the pressure surface above mean sea level, temperature, and, on some charts, wind speed. With modern computer workstations, any observed or derived parameter may be drawn on an upper level chart. Standard levels include charts for 925, 850, 700, 500, 300, 250, 200, 150 and 100 mb. For our discussion of the westerlies, only levels from 700 mb upward to 200 mb will be considered.
    [Show full text]
  • Contrasting Recent Trends in Southern Hemisphere Westerlies Across
    RESEARCH LETTER Contrasting Recent Trends in Southern Hemisphere 10.1029/2020GL088890 Westerlies Across Different Ocean Basins Key Points: Darryn W. Waugh1,2 , Antara Banerjee3,4, John C. Fyfe5, and Lorenzo M. Polvani6 • There are substantial zonal variations in past trends in the 1Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, USA, 2School of Mathematics magnitude and latitude of the peak 3 Southern Hemisphere zonal winds and Statistics, University of New South Wales, Sydney, New South Wales, Australia, Cooperative Institute for Research in • Only over the Atlantic and Indian Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA, 4Chemical Sciences Laboratory, National Oceans have peak winds shifted Oceanic and Atmospheric Administration, Boulder, CO, USA, 5Canadian Centre for Climate Modelling and Analysis, poleward, with an equatorward (yet Environment and Climate Change Canada, Victoria, British Columbia, Canada, 6Department of Applied Physics and insignificant) shift over the Pacific • Climate model simulations indicate Applied Mathematics, Columbia University, New York, NY, USA that the differential movement of the westerlies is due to internal atmospheric variability Abstract Many studies have documented the trends in the latitudinal position and strength of the midlatitude westerlies in the Southern Hemisphere. However, very little attention has been paid to the Supporting Information: longitudinal variations of these trends. Here, we specifically focus on the zonal asymmetries in the southern • Supporting Information S1 hemisphere wind trends between 1980 and 2018. Meteorological reanalyses show a large strengthening and a statistically insignificant equatorward shift of peak near‐surface winds over the Pacific, in contrast to a fi Correspondence to: weaker strengthening and signi cant poleward shift over the Atlantic and Indian Ocean sectors.
    [Show full text]
  • Weather and Climate Science 4-H-1024-W
    4-H-1024-W LEVEL 2 WEATHER AND CLIMATE SCIENCE 4-H-1024-W CONTENTS Air Pressure Carbon Footprints Cloud Formation Cloud Types Cold Fronts Earth’s Rotation Global Winds The Greenhouse Effect Humidity Hurricanes Making Weather Instruments Mini-Tornado Out of the Dust Seasons Using Weather Instruments to Collect Data NGSS indicates the Next Generation Science Standards for each activity. See www. nextgenscience.org/next-generation-science- standards for more information. Reference in this publication to any specific commercial product, process, or service, or the use of any trade, firm, or corporation name See Purdue Extension’s Education Store, is for general informational purposes only and does not constitute an www.edustore.purdue.edu, for additional endorsement, recommendation, or certification of any kind by Purdue Extension. Persons using such products assume responsibility for their resources on many of the topics covered in the use in accordance with current directions of the manufacturer. 4-H manuals. PURDUE EXTENSION 4-H-1024-W GLOBAL WINDS How do the sun’s energy and earth’s rotation combine to create global wind patterns? While we may experience winds blowing GLOBAL WINDS INFORMATION from any direction on any given day, the Air that moves across the surface of earth is called weather systems in the Midwest usually wind. The sun heats the earth’s surface, which warms travel from west to east. People in Indiana can look the air above it. Areas near the equator receive the at Illinois weather to get an idea of what to expect most direct sunlight and warming. The North and the next day.
    [Show full text]
  • Synoptic Meteorology
    Lecture Notes on Synoptic Meteorology For Integrated Meteorological Training Course By Dr. Prakash Khare Scientist E India Meteorological Department Meteorological Training Institute Pashan,Pune-8 186 IMTC SYLLABUS OF SYNOPTIC METEOROLOGY (FOR DIRECT RECRUITED S.A’S OF IMD) Theory (25 Periods) ❖ Scales of weather systems; Network of Observatories; Surface, upper air; special observations (satellite, radar, aircraft etc.); analysis of fields of meteorological elements on synoptic charts; Vertical time / cross sections and their analysis. ❖ Wind and pressure analysis: Isobars on level surface and contours on constant pressure surface. Isotherms, thickness field; examples of geostrophic, gradient and thermal winds: slope of pressure system, streamline and Isotachs analysis. ❖ Western disturbance and its structure and associated weather, Waves in mid-latitude westerlies. ❖ Thunderstorm and severe local storm, synoptic conditions favourable for thunderstorm, concepts of triggering mechanism, conditional instability; Norwesters, dust storm, hail storm. Squall, tornado, microburst/cloudburst, landslide. ❖ Indian summer monsoon; S.W. Monsoon onset: semi permanent systems, Active and break monsoon, Monsoon depressions: MTC; Offshore troughs/vortices. Influence of extra tropical troughs and typhoons in northwest Pacific; withdrawal of S.W. Monsoon, Northeast monsoon, ❖ Tropical Cyclone: Life cycle, vertical and horizontal structure of TC, Its movement and intensification. Weather associated with TC. Easterly wave and its structure and associated weather. ❖ Jet Streams – WMO definition of Jet stream, different jet streams around the globe, Jet streams and weather ❖ Meso-scale meteorology, sea and land breezes, mountain/valley winds, mountain wave. ❖ Short range weather forecasting (Elementary ideas only); persistence, climatology and steering methods, movement and development of synoptic scale systems; Analogue techniques- prediction of individual weather elements, visibility, surface and upper level winds, convective phenomena.
    [Show full text]
  • On the Dynamics of Tropical Cyclone Structural Changes
    Quart. J. R. Met. SOC. (1984), 110, pp. 723-745 551.515.21 On the dynamics of tropical cyclone structural changes By GREG. J. HOLLAND. and ROBERT T. MERRILL Department of Atmospheric Science, Colorado State University (Received 16 March 1983; revised 17 January 1%) SUMMARY Tropical cyclone structural change is separated into three modes: intensity, strength and size. The possible physical mechanisms behind these three modes are examined using observations .in the Australiadsouth-west Pacific region and an axisymmetric diagnostic model. We propose that, though dependent on moist convection and other internal processes, the ultimate intensity, strength or sue of a cyclone is regulated by interactions with its environment. Possible mechanisms whereby these interactions occur are described. 1. INTRODUCTION Most of the work on tropical cyclone development in past years has been concerned with ‘genesis’ and ‘intensification’, even though no precise definition exists for either term. The result has been confusion in interpreting some aspects of cyclone structural changes, and the neglect of other aspects altogether. More precise and comprehensive interpretations are possible if we separate tropical cyclone structural changes into three modes: intensity, strength, and size (Merrill and Gray 1983). These are illustrated in Fig. 1 as changes from an initial tangential wind profile. ‘Intensity’ is defined by the maximum wind, or by the central pressure if no maximum wind data are available, and has received the most attention in the literature. ‘Strength’ is defined by the average relative angular momentum of the low-level inner circulation (inside 300 km radius). ‘Size’ is defined by the axisymmetric extent of gale force winds, or by the radius of the outermost closed isobar.
    [Show full text]