REMOTE SENSING IN REMOTE SENSING IN METEOROLOGYMETEOROLOGY

APPLICATIONS FOR APPLICATIONS FOR STORMSSTORMS

CEMALETTİN B. BOLATCEMALETTİN B. BOLAT

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STORMSTORM

• 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.

• 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.

• With research efforts in: Radar

Satellite Software Development Modeling

Tornadoes Thunderstorms Damaging Winds Lightning Hail Winter Weather Flooding

• 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.

Regional MW OI SST maps and SST Regional MW OI SST maps and SST values at forecasted storm values at forecasted storm

locations:locations:

• 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 (< 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.

About SST Storm Maps: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.

About QuikScat Storm Viewer: 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.

Locating TornadoesLocating Tornadoes hook echoes and velocity couplets 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

• 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.

• 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.

Image: hook echo new Newcastle Image: hook echo new Newcastle

Supercell ThunderstormsSupercell Thunderstorms thunderstorms with deep rotating thunderstorms with deep rotating

updrafts 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.

• 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.

Radial VelocityRadial Velocity measured by Doppler radars 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".

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

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

• 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.

Snow StormsSnow Storms radar data is used to identify bands radar data is used to identify bands

of heavy snow 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

• 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.

Four ingredients are necessary for severe thunderstorm development

• a deep layer of moisture in the lowest 1-2 km’s 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

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.

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.

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.

• 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.

• 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.

• By Doppler Radar, rotational signatures within thunderstorms detected by Doppler radar allow lead-times of 10’s 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

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.

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.

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.

• 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