Review question. How does hail form? What factors govern the ultimate size of hailstones?. Hail is produced only in cumulonimbus clouds where updrafts and downdrafts are strong and where there is an abundant supply of supercooled water.
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How does hail form? What factors govern the ultimate size of
Hail is produced only in cumulonimbus clouds where updrafts
and downdrafts are strong and where there is an abundant supply
of supercooled water.
Hailstones begin as tiny ice pellets that grow by collecting
supercooled cloud droplets as they fall through the cloud.
If a strong updraft is encountered, the hail may be carried
upward again and begin the descent anew.
For surface low pressure to exist for an extended period of time,
what condition must exist aloft?
In order for surface low pressure to exist for a reasonable period
of time, compensation must occur aloft. Surface pressure would be
maintained if divergence aloft occurs at a rate equal to the
Distinguish between macroscale, mesoscale and microscale
winds. Give an example of each.
Macroscale winds, the largest wind pattern, involve a time scale
of from days to years (hurricanes, mean global flow).
Mesoscale winds involve a time scale of from minutes to days
and include local winds such as the sea breeze as well or
weather phenomena such as tornadoes.
Microscale winds are very short-lived winds (from seconds to
minutes) and involves such things as turbulence (wind gusts).
What are two possible ways a blocking high might influence
Blocking highs can block the eastward migration of cyclones,
keeping one region dry and keeping another region continually
under the influence of cyclone storms.
Another influence of blocking highs is their contribution to air
pollution episodes. This can happen as subsidence within an
anticyclone can produce a temperature inversion and light winds
associated with the center of an anticyclone do little to disperse
Synoptic Weather Forecasting
The ENIAC machine occupied a room thirty by fifty feet. The controls are at the left, and a small part of the output device is seen at the right.
Eta Model Vertical Resolution Characteristics/Layer Distribution
Numerical Weather Prediction
Numerical Weather Prediction
A forecasting technique that entails running several weather forecasts models, each beginning with slightly different weather information. The forecaster’s level of confidence is based on how well the models agree (or disagree) at the end of some specified time.
Scientific and computational limitations prevent us from constructing a perfect numerical model of real systems. In a chaotic system like the atmosphere errors in the initial conditions contribute to the eventual loss of predictive skill.
Ensemble forecasting, where not only one but a number of numerical integrations are carried out, was first introduced to assess initial error related variations in predictability
Dr. Eugenia Kalnay
Distinguished University Professor, Department of Meteorology
University of Maryland
1965. Ph. D., 1971, MIT (under Jule G. Charney)
By looking at a number of model runs the forecaster can rule out or give more consideration to a particular weather scenario as well as get a general feel for the variability of a weather pattern.
Propagation of Errors
Random error is the irreproducibility in making replicate measurements and affects the precision of a result. The distribution of random errors follows a Gaussian-shape “bell" curve. The precision is described by statistical methods such as a standard deviation or confidence limit.
Systematic errors are errors that produce a result that differs from the true value by a fixed amount. These errors result from biases introduced by instrumental method, or human factors.
Systematic errors can sometimes be identified and corrected.
Propagation of Errors
Giving that many time steps are needed to produce a forecast, the
problem of “propagation of errors” is a constraint on weather
Small errors may make
little difference in the
early stages of prediction,
can amplify dramatically
Yt = (a x Yt+1) – Y2t
Tools in Weather Forecasting
Satellite Observations and remote sensing
The last 25 years have seen an explosion of remote weather
products. One advantage to these systems is that they provide
continuous data collection which allows observation changes
in the atmosphere over several time scales.
Challenge to design forecast models which
take advantage of constant data stream.
An electronic instrument used to detect objects (such as falling precipitation) by their ability to reflect and scatter microwaves back to a receiver.
(Next Generation Radar)
In 1988, the NEXRAD Agencies established the WSR-88D (Weather Surveillance Radar 88 Doppler) Radar Operations Center (ROC) in Norman, Oklahoma.
The NEXRAD network provides significant improvements in severe weather and flash flood warnings, air traffic safety, flow control for air traffic, resource protection at military bases, and management of water, agriculture, forest, and snow removal.
The wind profiler is a ground based array of multiple beam Doppler radar units which measures and displays wind information up to an altitude of 16 km. This instrument is generally used to detect low level wind shear.
Automated Surface Observing System (ASOS) / Automated Weather Observing System (AWOS)
Automated Weather Observing System (AWOS) is a suite of sensors, which measures, collects and broadcasts weather data to help meteorologists, pilots and flight dispatchers prepare and
monitor weather forecasts, plan flight
routes, and provide necessary
information for correct takeoffs and
Polar orbiting satellites orbit the globe
at low altitudes (a few hundred km)
which allows them to complete one
pass in 100 minutes. With such a
quick orbit the satellite can capture
two sweeps of the globe in 24 hours.
Polar Orbiting Satellite ViewHigh Resolution Picture Transmission(from: Patrick Prokop, Meteorologist, WTOC-TV
Geostationary satellites were placed in orbit over the equator; they remain fixed over a point. To keep the satellite in place over Earth the satellite must orbit at a farther distance than
polar orbiters (35,000 kms). Some resolution is lost but very powerful satellites.
The TIROS Program (Television Infrared Observation Satellite) was NASA's first experimental step to determine if satellites could be useful in the study of the Earth
The images above show the stark contrast between the first image beamed down from
TIROS-1 on April 1, 1960 and the full-color full-Earth images that GOES-8 produces every
three hours. But, if it hadn't been for TIROS and the TIROS experiment, there would
be no GOES images today.
NOAA's National Environmental Satellite,Data and Information Service
NESDIS operates the satellites and manages the processing and distribution
of millions of bits of data and images these satellites produce daily. The
prime customer for the satellite data is NOAA's National Weather Service,
which uses satellite data to create forecasts for television, radio, and weather
NOAA's operational environmental satellite system is composed of:
geostationary operational environmental satellites (GOES) for short-range
warning and "nowcasting," and polar-orbiting environmental satellites (POES)
for longer term forecasting. Both kinds of satellites are necessary for
providing a complete global weather monitoring system. The satellites carry
search and rescue instruments, and have helped save the lives of about
10,000 people to date. The satellites are also used to support aviation safety
and maritime/shipping safety (ice monitoring and prediction).
Around the world...around the clock...NOAA proudly stands watch. As an integral part of worldwide search and rescue, NOAA operates the Search & Rescue Satellite Aided Tracking (SARSAT) System to locate those in distress almost anywhere in the world at anytime and in most conditions.The SARSAT system uses NOAA satellites in low-earth and geostationary orbits to detect and locate aviators, mariners, and land-based users in distress. The satellites relay distress signals from emergency beacons to a network of ground stations and ultimately to the U.S. Mission Control Center (USMCC) in Suitland, Maryland. The USMCC processes the distress signal and alerts the appropriate search and rescue authorities to who is in distress and, more importantly, where they are located. Truly, SARSAT takes the "search" out of search and rescue.
Chapter 13 Air Pollution
AMERICAN CHEMICAL SOCIETY
AN EXAMINATION OF THE ATMOSPHERE OF A LARGE
By Charles F. Mabery
“….The essential constituents of the atmosphere include oxygen, nitrogen, and
carbon dioxide in constant proportions, nitrous and nitric acids, sulphurous and
sulphuric acids, dust, soot, moisture, ammonia, and certain other constituents in
variable proportions depending upon atmospheric conditions and local influences.
The allotropic form of oxygen, ozone is an important constituent of the atmosphere,
and probably also hydrogen dioxide….”
A Brief Historical Perspective
Air pollutants: Airborne particles and gases occurring in
concentrations that endanger the health and well being of
organisms or disrupt the orderly functioning of the environment.
The atmosphere’s composition of gases is always changing
(some gases are changing much faster than others). Natural
sources of air pollution have always existed. Some examples of
natural air pollution are: volcanic ash, salt particles from the
oceans, pollen and spores released by plants, smoke from forest
fires and windblown dust.
An important thing to consider when looking at atmospheric gases is not necessarily the concentration but rather the reactivity. Very reactive gases, even though they are not present in “high” concentrations are important.
The OH radical is one of the most important
species in atmospheric chemistry and global
change, as it controls the lifetimes of many
important atmospheric species, such as methane
and the alternative chlorofluorocarbons.
However, because of its high reactivity, the
concentration of the OH radical in the
atmosphere is very small (typically less than
0.5 parts per trillion by volume) and its lifetime
very short (less than 1 second). As a result,
accurate measurements of the OH radical in the
atmosphere are extremely difficult.
Sources of primary pollution
Factories were symbolic of economic growth and prosperity
“I want the sky to be filled with smoke of American industry and upon that cloud of smoke will rest forever the bow of perpetual promise.”
-Robert Ingersoll 1880
An intricate connection between economic development and pollution.
Natural air pollution can be accentuated by human activities
Dust storm in 1937 occurred because the soil was plowed
and vulnerable to strong winds.
Sources and Types of Air Pollution