REMOTE SENSING IN METEOROLOGY APPLICATIONS FOR STORMS

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REMOTE SENSING IN METEOROLOGYAPPLICATIONS FOR
STORMS

• CEMALETTIN B. BOLAT
• 110020211

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STORM

• A storm is any disturbed state of a planet's
  atmosphere, especially affecting its surface, and
  strongly implying severe weather. It may be
  marked by strong wind (a wind storm), thunder and
  lightning (a thunderstorm), heavy precipitation,
  such as ice (ice storm), or wind transporting
  some substance through the atmosphere (as in a
  dust storm, snowstorm, hailstorm, etc).
• Storms are created when a center of low pressure
  develops, with a system of high pressure
  surrounding it. This combination of opposing
  forces can create winds and result in the
  formation of storm clouds, such as the
  cumulonimbus.
• A strict meteorological definition of a storm is
  a wind measuring 10 or higher on the Beaufort
  scale, meaning a wind speed of 89 km/h (55 mph)
  or more however, popular usage is not so
  restrictive.

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• The National Severe Storms Laboratory is one of
  NOAA's internationally known research
  laboratories, leading the way in investigations
  of all aspects of severe weather. Headquartered
  in Norman OK, the people of NSSL, in partnership
  with the National Weather Service, are dedicated
  to improving severe weather warnings and
  forecasts in order to save lives and reduce
  property damage.

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• With research efforts in
• Radar Satellite Software Development
  Modeling Tornadoes Thunderstorms Damaging
  Winds Lightning Hail Winter Weather Flooding

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• Powerful storms such as thunderstorms,
  hurricanes, and tornadoes are generated when
  warm, light air rises quickly into higher, colder
  levels in an unstable updraft that can reach over
  100 miles per hour. Each type of storm forms
  under specific conditions hurricanes occur over
  moisture-rich oceans and coastlines, for example.
  They draw their energy from warm ocean waters.
  Understanding the conditions that give rise to
  powerful storms is the key to preparing for their
  devastating effects.

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Regional MW OI SST maps and SST values at
forecasted storm locations
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• The SSTs shown here on the RSS Storm Watch site
  are a Microwave Optimally Interpolated (MW OI)
  daily SST that utilizes both TMI and AMSR-E SST
  retrievals. This new MW OI SST product has good
  coverage since it utilizes data from two
  satellites, and is responsive to the most recent
  observations available. Diurnal warming is
  removed from this SST product, so it is a good
  representation of temperature in the upper
  several meters of sea water. Satellite SST
  retreivals generally measure the skin temperature
  (lt 1 milimeter), where solar heating can cause
  warming of 3 C in low wind. Removing the
  diurnal warming component leads to a more
  accurate measurement of the heat energy content
  in the upper several meters of ocean water, where
  it is available to a tropical cyclone. This MW OI
  SST provides important measurements of the
  ocean's heat energy in front of tropical cyclones.

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About SST Storm Maps

• The through-cloud capabilities of the microwave
  SSTs provide a valuable picture of the ocean
  surface temperatures in front of a storm path.
• In the SST imagery, areas with no data are shown
  in light grey. This is mostly due to proximity to
  land, which is shown in dark grey.
• The SST Anomaly maps consist of differences
  between MW OI SSTs and Reynold's SST climatology
  data. The anomaly maps best reveal
  mixing/upwelling due to tropical storms.
• They update the maps and tracks every 3 hours.
  Forecasted positions are shown with a dashed
  black line, with forecasted wind speed indicated
  by circle diameter.

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About QuikScat Storm Viewer

• The SeaWinds Scatterometer (QuikScat) crosses
  many tropical cyclones approximately twice daily
  dependent upon storm forward velocity. Plots
  include QuikScat 10-meter ocean surface vector
  winds (shown as wind barbs or ambiguities), daily
  Microwave OI SSTs, and collocated SSM/I rain
  rates. The winds are derived using the Ku-2001
  algorithm. A help button is provided to describe
  the parts and uses of this TC analysis
  environment.

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Locating Tornadoes hook echoes and velocity
couplets

• Tornadoes are often located at the center of a
  hook-shaped echo on the southwest side of
  thunderstorms. The hook is best observed in the
  reflectivity field. This image shows a
  reflectivity field containing several hook echoes
  associated with thunderstorms that occurred in
  Tennessee and Kentucky on May 18, 1995

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• Another way to determine if a storm is tornadic
  is to examine the radial velocity field. A
  mesocyclone, the small rotating circulation with
  its center beneath the updraft of a supercell
  thunderstorm, is detectable as a velocity
  couplet.

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• The couplet is oriented so that a concentrated
  area of radial winds moving away from the radar
  appears on one side of the beam axis, while a
  concentrated area of radial winds moving toward
  the radar appears on the opposite side of the
  beam axis. When the central pixels near the beam
  axis show exceptionally strong winds, this
  signature is called a tornado vortex signature
  (TVS). This image shows the TVS in the velocity
  field from the same Tennessee and Kentucky
  storms. Negative values (blue-green) denote
  movement toward the radar and positive values
  (yellow-red) represent movement away from the
  radar.

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Image hook echo new Newcastle
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Supercell Thunderstorms thunderstorms with deep
rotating updrafts

• One of the major storm types is the supercell. We
  define a supercell as a thunderstorm with a deep
  rotating updraft (mesocyclone). In fact, the
  major difference between supercell and multicell
  storms is the element of rotation in supercells.
  As we shall see, circumstances keep some
  supercells from producing tornadoes, even with
  the presence of a mesocyclone.

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• Even though it is the rarest of storm types, the
  supercell is the most dangerous because of the
  extreme weather generated. This storm was
  producing baseball hail east of Carnegie,
  Oklahoma, as it was photographed looking east
  from 30 miles. From right to left (south to
  north), we note the flanking line, main Cb, and
  downwind anvil above the precipitation area.

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Radial Velocity measured by Doppler radars

• Doppler radars can measure the component of the
  velocity of targets toward or away from the
  radar. This component is called the "radial
  velocity".

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• For example, at time T1 a pulse is sent towards a
  target and it returns a target distance "D".

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• At time T2, another pulse is sent towards the
  same target and returns a target distance "DA"

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• The distance to target has changed from times T1
  to T2, resulting in a phase shift between the two
  return signals, which Doppler radars are capable
  of measuring. By knowing the phase shift, the
  wavelength and the time interval from T1 to T2,
  the velocity the target has moved toward or away
  from the radar can be computed. If the target is
  moving sideways so that its distance relative to
  the radar does not change, the radar will record
  zero radial velocity for that target.

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Snow Storms radar data is used to identify bands
of heavy snow

• This image shows the different scales on which
  snow can occur. The large snow band extending
  across the figure is associated with a large
  storm system moving across the country

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• Superimposed on the large system, is a smaller
  scale snow band located off the west shoreline of
  Lake Michigan. Each of these bands individually
  produced heavy snow and where they intersected
  near Chicago, the snow was particularly intense.

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• Four ingredients are necessary for severe
  thunderstorm development
• a deep layer of moisture in the lowest 1-2 kms
  of the atmosphere,
• instability,
• a lifting mechanism such as a frontal boundary,
  which acts to initiate thunderstorms, and
• moderate to strong vertical wind shear
• Meteorologists use satellite data in order
  to examine how these four necessary ingredients
  are evolving in near real-time, and then
  integrate these data with other non-satellite
  data sources.
• Three primary wavelengths used are,
• visible,
• infrared, and
• Water Vapour

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• It is now possible to watch a severe weather
  event evolve, occur, and then analyze it from the
  perspective of remote sensing devices. Direct
  observation of changes in near real-time is an
  important part of severe weather forecasting,
  especially as meteorology is a field which is
  constantly in flux, and the current surface
  observing networks are far from source.

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• Most tornadoes develop out of mesocyclone that
  forms in the strong updraft of a severe
  thunderstorm ( supercell) by a process that is
  not yet well understood. The circulation in a
  tornado is apparently the consequence of an
  interaction between a thunderstorm updraft and
  strong shear in the horizontal wind.
• Waterspouts, virga and dust devils resemble
  tornadoes in appearance only.

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• Weather radar determines the location and
  movement of areas of precipitation. Echo strength
  increases with precipitation intensity.
• Currently, conventionally radar is being
  replaced by Doppler radar, which can determine
  the detailed movement of targeted precipitation
  toward or away from the radar unit based upon
  frequency shift. Doppler radar monitors can be
  noticed the circulation with a severe
  thunderstorm and thus can provide advance warning
  of tornado development.

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• Early satellite imagery, provided by the TIROS-1
  weather satellite produced little more than a
  hazy picture of the general cloud patterns in the
  earths atmosphere, but tremendous advancements in
  satellite research and development during the
  last 30 years now provide meteorologists with
  numerous satellite derived visual and numerical
  products.

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• Computer model generated forecasts are also
  analyzed in order to see how the atmosphere might
  evolve through the day, but the addition of near
  real-time weather observations provided by
  satellite imagery allows the forecaster to
  interpret more precisely where thunderstorms may
  initiate, and when they do, whether they will be
  severe or not.

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• By Doppler Radar, rotational signatures within
  thunderstorms detected by Doppler radar allow
  lead-times of 10s of minutes in alerting the
  public to tornadic development (OSF 1999). This
  active remote sensing device also allows
  forecasters to evaluate any storm for the
  potential of large hail, severe winds, and heavy
  rainfall. In addition to forecasting severe
  thunderstorms, high-resolution satellite data
  provides valuable post-event analysis of
  locations which have been damaged by severe
  thunderstorms. Various indices of the surface
  areas which have been scoured by tornadoes,
  hurricanes, and other natural disasters

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• Infrared satellite imagery (3.8-4.0 micrometers)
  allows meteorologists to observe thunderstorms
  during both day and night.
• IR imagery does not provide a lot of information
  on surface processes, but is valuable in
  examining the characteristics of storm-top
  evolution, which reveals quite a bit of
  information on how a thunderstorm is behaving.

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• Certain temperatures in the IR are
  highlighted through MB enhancement, which aid
  meteorologists in locating the most intense
  convective updrafts during mesoscale convective
  complexes (MCC) events which may be producing
  heavy rainfall, and finally, whether the MCC is
  beginning to decay or strengthen.

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Water vapor imagery provides key information on
the large-scale synoptic patterns which lead to
severe weather events. This is all possible due
to the absorption of certain wavelengths by the
atmosphere, specifically clouds and suspended
water vapor. Two widely used applications of
this concept are channel 9 (7.3 microns) and
channel 10 (6.7 microns) on the GOES VISSR
sensors. Energy emitted at these particular
wavelengths is readily absorbed by water vapor in
the middle and upper atmosphere.
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• The large scale waves show up as elongated ridges
  and troughs of cloud (water vapor, often
  associated with the jet stream), while the
  shortwaves are areas of enhanced subsidence (very
  dry regions, which are dark) moving rapidly
  through the longer waves. These shortwaves are
  often responsible for aiding in the initiation of
  severe thunderstorms, and are closely monitored
  by meteorologists.
• - A detailed picture of how the whole atmosphere
  is evolving can be obtained when the visible, IR,
  and water vapor channel imagery are integrated
  together

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