Surface Weather Elements

Station Plots

• Station "plots" or "model" are used to spatially display the current conditions in a particular region.

Current Plots

Test Yourself

Isoplething

• The analysis process represents only one step in the production of an analysis chart. The construction of isopleths can entail either subjective or objective analysis schemes.

• Subjective analysis refers to a hand-drawn product, where a meteorologist draws isopleths based upon visual interpolation between the irregularly distributed data points, coupled with continuity from previous charts, experience and intuition.

• Objective analysis typically refers to computer generated products, where the isopleths are generated by numerical interpolation schemes involving an organized grid representation of the given field.

• On the surface map there are many more stations to provide information and the following information is given to you:
• Wind speed and wind direction (wind barb at each station)
• Isobars drawn at 4-mb intervals
• Areas of relatively High (H) and Low (L) pressure.

• As one studies the sequence of the three surface maps one sees how both the surface fronts and the areas of low and high pressure move. These features are:
• Transient
• Linked to what's going on at 500-mb! Dynamic!

• Matter of fact, the activity associated with upper-level troughs (movement, location, development) dictates the movement, location and development of the surface low- and high-pressure systems!

• One thing to do in any sequence is pick a location, let's say St. Louis and examine how the surface characteristics change with time. 

Sea-level pressure, surface winds, and frontal positions at 00, 09, and 18 UTC 10 Nov 1998. The dashed blue line denotes the cold front. The contour interval for sea-level pressure is 4 hPa. [Atmospheric Science, Wallace & Hobbs]

Surface air temperature (in degrees celsius) and frontal positions at 00, 09, and 18 UTC 10 Nov 1998.  [Atmospheric Science, Wallace & Hobbs] 

Winds and Pressure

• Wind is plotted vectorially, showing the direction from which the wind is coming from.

• It tends to blow across the isobars going from higher pressure to lower pressure at and near the surface.
• This flow across the isobars is due to friction.

• As you examine the maps you will see that areas of high pressure are separated by troughs of lower pressure.

• A surface trough represents an area of convergence or a line of confluence where air is flowing together in the wind field. The confluence line is generally represented by some type of front.

• Areas of surface low-pressure develop along the confluence line.

• Generally ahead (or to the east) of the surface low pressure the confluence line moves northward (with southerly winds) while behind (or to the west) of the surface low pressure the confluence line moves southward (with northerly winds).

• Counterclockwise (cyclonic) circulation develops around the surface low

Station Models. Wind entries. [Aguado and Burt 411]

Temperature and Fronts

• Surface temps can be plotted.  Once plotted these values represent an excellent way to define frontal location.

• As one can clearly see the temp. north of the convergence or confluence line are much cooler than those south of it.  This is typically the case in the N.H. (weaker differences in the summer than winter).
• Gulf air (warm, moist) -- mT
• Canadian air (cool, dry) -- cP

• If we compare temps to where the wind is blowing from, the relationship between temps and wind direction can be drawn.

• In the warm air region south of the confluence line the temps appear horizontally homogeneous. This is expected in a air mass.

Idealized cross sections through frontal zones showing air motions relative to the ground in the plane transverse to the front. Colored shading indicates the departure of the local temperature from the mean temperature of the air at the same level. (a) Warm front. (b) Stationary front. (c) Cold front. Heavy arrows at the bottom indicate the sense of the frontal movements. [Wallace and Hobbs 321]

Surface air temperature (in degrees celsius) and frontal positions at 00, 09, and 18 UTC 10 Nov 1998.  [Wallace and Hobbs 324] 

Fronts

• Because the confluence line, a boundary, separates relatively cool air from warm air we call it a front.

• The region of strong thermal contrast on the "cold air side (poleward)" of the confluence line is called a frontal zone or baroclinic zone.
• It is the zone, not the front, that separate the cool and warm air masses.  The front represents the warm air boundary of the frontal zone and coincides with the line of confluence in the wind field.

• Fronts are named based on the direction of movement:
• Cold air advancing → cold front (triangles on front)
• Cold air retreating → warm front (semi-circles on front)

• The direction of the front movement is based on the side of the front the symbols are located and direction they are pointing.

• Stationary fronts are denoted by alternating cold and warm front symbols on different sides.

• A transition zone between two air masses of different densities (temp) and humidities.

• They are important not only for temp. and humidity changes they bring but also for the uplift they cause (frontal “wedging”).

• Four primary types:
• Cold
• Warm
• Stationary
• Occluded

Frontal symbols used on surface weather maps. [Robert et al. 166]

• Identifying Fronts:
• Sharp horizontal temperature change
• Sharp horizontal dewpoint/humidity temperature change
• Shift in the wind direction
• Presence of clouds & precipitation
• Change in pressure

• Frontal Characteristics
• Why do fronts move?  Examine the vertical cross sections normal to the fronts which are moving.
• Air within the frontal zone is "trapped" in the shallow wedge beneath the frontal surface and thus can not move relative to the front, or conversely, the front can not move relative to it.
• The direction and speed of movement of the front is determined by the winds within the frontal zone.
• In warm front situation -- cold air retreats poleward and warm air tied to southerly winds tries to push up the frontal surface -- providing for the development of layered clouds (aka stratus).
• In cold front situation -- cold air (associated with northerly winds) advances southeastward forcing the warm air to rise vertically -- giving way to vertically developed clouds.

• Temperatures and Fronts
• Role of fronts in mediating surface temps is important, but other factors influence surface temps including: time of day, sky cover, altitude of the station, and proximity to water
• These can exert an equally important role of influencing temps

• Fronts are often difficult to locate because...
• Over oceans, temps are strongly influenced by underlying water (sea surface temps do not change much over a short distance)
• In mountainous terrain, large difference in station elevation mask the temp gradients
• Terrain effects, nocturnal inversions, convection, and UHI can all affect temps.

Moisture and Dew Point

• Similar to the steep temp. gradients located along lines of confluence, we see horizontal gradients of dew point.
• Steep gradient (continental vs. maritime air)
• Weak gradient (cool maritime vs. warm maritime air)

• In some situations the dew point gradient is a more reliable indicator; especially in summer when temp. differences near fronts are small.

• Dryline is the boundary between  marine and continental air masses.
• Forms due to land-sea geometry and terrain features.
• Typically form during warm season and are situated meridionally across the southern and central Great Plains.

Precipitation

• The distribution of fog and precip. is very much related to the location of the front.

• Early on, the precip. is located north of the stationary front because the warm air overruns the sloping frontal surface.  The snow continues along the front-range of the Rockies as easterly surface winds push the air up the mountain range, lifting mechanism.

• Eventually, the precip will become of greater intensity and will increase in areal coverage due to the surface low and upper air trough deepening causing more surface convergence.

• Fog exists along the warm front and north of the stationary front. Fog is common when warm, moist air passes over a colder, underlying surface.

• The band of precip. associated with the cold front is generally more intense but in narrow bands.  Often t-storms will occur along the cold front

Precipitation Tendency

• Passage of warm front is associated with a leveling off of the pressure (warm, moist air).

• Passage of cold front triggers a rise in the surface pressure.

• Pressure rises after a cold front are usually greater than the pressure falls which occur prior to the passage of a warm front.

• In surface analysis, lines connecting points at which the same pressure tendency occurs are called isallobars.

• The pressure falling in the vicinity of the low pressure indicates that the low is deepening as it moves.  With this comes stronger winds in the circulation around the low.

• When interpreting small changes in pressure, the diurnal cycle in solar heating produces small but noticeable pressure fluctuations that have nothing to do with synoptic situation.  These are referred to as tidal fluctuations and should be removed before a true synoptic assessment.

Works Cited

Aguado, Edward, and James E. Burt. Understanding Weather and Climate. 7th ed., Pearson, 2014.

Rauber, Robert M., et al. Severe and Hazardous Weather: An Introduction to High Impact Meteorology. 4th ed., Kendall Hunt, 2014.

Wallace, John, and Peter Hobbs. Atmospheric Science: An Introductory Survey. 2nd ed., Academic Press, 2006.

Solving litter box Problems

Solving litter box Problems

Cats tend to have surface and location preferences for where, and on what, they like to eliminate. Most cats prefer a loose, sandy substance, which is why they will use a litter box. It's only when their preferences include the laundry basket, the bed or the Persian rug, that normal elimination behavior becomes a problem. With careful analysis of your cat's environment, specific factors that have contributed to the litter box problem can usually be identified and changed, so that your cat will again use the litter box for elimination.

Some common reasons why cats don't use the litter box: an aversion to the box, a preference for a surface not provided by the box, a preference for a location where there is no box or a combination of all three. You'll need to do some detective work to determine the reason your cat is house soiling. Sometimes, the reason the litter box problem initially started may not be the same reasoning it's continuing. For example, your cat may have stopped using the litter box because of a urinary tract infection, and has now developed a surface preference for carpet and a location preference for the bedroom closet. You would need 0 address all three of these factors to resolve the problem.

Cats don't stop using their litter boxes because they're mad or upset and are trying to get revenge for something that "offended" or "angered" them. Because humans act for these reasons, it's easy for us to assume that our pets do as well. Animals don't act of spite or revenge, so it won't help to give your cat special privileges in the hope that she'll start using the litter box again.

Medical Problems

It's common for cats to begin eliminating outside of their litter box when they have a medical problem. For example, a urinary tract infection or crystals in the urine can make urination very painful. Cats often associate this pain with the litter box and begin to avoid it. If your cat has a house-soiling problem, check with your veterinarian first to rule out any medical problems for the behavior. Cats don't always act sick, even when they are, and only a trip to the veterinarian for a thorough physical examination can rule out a medical problem.

Cleaning Soiled Areas

Because animals are highly motivated to continue soiling an area that smells like urine or feces, it's imperative that you thoroughly clean the soiled areas.

Aversion to the litter box

You cat may have decided that the litter box is an unpleasant place to eliminate if:

v  The box is not clean enough for her.

v  She has experienced painful urination or defecation in the box due to a medical problem.

v  She has been startled by a noise while using the box.

v  She has been "ambushed" while in the box either by another cat, a child, a dog, or by you, if you were attempting to catch her for some reason.

v  She associates the box with punishment (someone punished her for eliminating outside the box, and then placed her in the box).

What You Can Do

·         Keep the litter box extremely clean. Scoop at least once a day and change the litter completely every four to five days. If you use scoop able litter, you may not need to change the litter as frequently. This will vary per how many cats are in the household, how many litter boxes you have, and how large the cats are that are using the box or boxes. A good guideline is that if you can smell the box, then you can be sure it's offensive to your cat as well.

·         Add a new box in a different location than the old one and use a different type of litter in the new box. Because your cat has decided that her old litter box is unpleasant, you'll want to make the new one different enough that she doesn't simply add the old, negative associations to the new box.

·         Make sure that the litter box isn't near an appliance that makes noise or in an area of the house that your cat doesn't frequent.

Surface Preferences

All animals develop preferences for a surface on which they like to eliminate. These preferences may be established early in life, but they may also change overnight for reasons that we don't always understand. Your cat may have a surface preference if:

v  She consistently eliminates on a texture. For example, soft-textured surfaces, such as carpet, bedding or clothing, or slick-textured surfaces, such as tile, cement, bathtubs or sinks.

v  She frequently scratches on this same texture after elimination, even if she eliminates in the litter box.

v  She is or was previously an outdoor cat and prefers to eliminate on grass or soil.

What You Can Do

·         If your cat is eliminating on soft surfaces, try using a high quality, scoop able litter, and put a soft rug under the litter box.

·         If your cat is eliminating on slick-textured surfaces, try using a high quality, scoop able litter, and put a soft rug under the litter box.

·         If your cat has a history of being outdoors, add some soil or sod to the litter box.

·         Make the area where she has been eliminating aversive to her by covering it with an upside-down carpet runner or aluminum foil, or by placing citrus-scented cotton balls over the area.

Location Preferences

Your cat may have a location preference if:

v  She always eliminates in quiet, protected places, such as under a desk downstairs or in a closet.

v  She eliminates in an area where the litter box was previously kept or where there are urine odors.

v  She eliminates on a different level of the house from where the litter box is located.

What You Can Do

·         Put it least one litter box on every level of your house.

·         Make the area where she has been eliminating aversive to her by covering it with upside down carpet runner or aluminum foil, or by placing citrus-scented cotton balls over the area.

Or

·         Put a litter box in the location where your cat has been eliminating. When she has consistently used this box for at least one month, you may gradually move it to a more convenient location at a rate of an inch per day.

Oops!

If you catch your cat in the act of eliminating in the house, do something to interrupt her like making a startling noise, but be careful not to scare her. Immediately take her to the where the litter box is located and set her on the floor. If she wanders over to the litter box, wait and praise her after she eliminates in the box. If she takes off in another direction, she may want privacy, so watch from afar until she goes back to the litter box and eliminates, then praise her when she does.

Don't ever punish your cat for eliminating outside of the litter box. If you find a soiled area, it's too late to administer a correction. Do nothing but clean it up. Rubbing your eat's nose in it, taking her to the spot and scolding her, or any other type of punishment, will only make her afraid of you or afraid to eliminate in your presence. Animals don't understand punishment after the fact, even if it's only seconds later. Punishment will do more harm than good.

Other Types of House soiling Problems

v  Fears or Phobias: When animals become frightened, they may lose control of their bladder and/or bowels. If your cat is afraid of loud noises, strangers, or other animals, she may house soil when she is exposed to these stimuli.

Weather Station Model

Temperature, pressure, moisture, and wind measurements are reported hourly at the surface (most are usually made 2 meters above the ground).

77: Temperature.

68: Dewpoint.

998: Pressure, to the nearest tenth of a millibar. Add either a 10 or 9 in front based on which would bring the value closer to 1000. The pressure here is 999.8 millibars (mb).

-03: Pressure tendency the last 3 hours, to the nearest tenth of a millibar. The pressure here has fallen .3 mb the last 3 hours.

Middle Circle (filled in w/ mostly black): Cloud cover. It's mostly black showing that this station is mostly cloudy. Technically, this represents a broken sky with 7/8 of the sky covered with clouds.

Black line, extending from circle: Wind barb. It points to where the wind is coming from. The wind here is from the southwest, hence a southwest wind. The two lines extending represent 20 knot winds with each line representing 10 knots.

Symbol between 77 and 68: This is the present weather field and in this case shows that there is a thunderstorm occurring at the station.

Symbol next to -03: That line is the pressure tendency. The 1st hour the pressure was steady, then fell the last two hours.

Triangle (with a dot above it): Previous weather, or the weather one hour ago. In this case it was a light rain shower.

How does the upper air station model differ from the surface station model?

─     Temperature is given in Celsius

─     Dewpoint depression is given not dewpoint temperature

─     Altitude of the pressure surface is given instead of pressure

─     Cloud cover is not noted

─     Circles indicating station locations are often omitted

Forecasting: Short Waves in the Upper Atmosphere and Their Effect on Surface Conditions

Understanding Weather and Climate (7th Edition) (MasteringMeteorology Series) by Edward Aguado, James E. Burt 

Weather Maps--The Surface Station Model and Surface Weather Maps

Ø  The Surface Station Model and Surface Weather Maps

̶        Temperature, pressure, moisture, and wind measurements are reported hourly at the surface (most are usually made 2 meters above the ground)

̶        Station Model:

·         Isobars: Lines of constant pressure

·         Pressure Gradient: Where pressure changes over distance

·         Temperature Gradient: rapid change in temperature with distance

·         Isotherms: Lines of constant temperature

Meteorological Measurements

Ø  Surface Measurements

̶        Most locations report hourly automated measurements

̶        Non-automated measurements are reported every 3 hours

̶        U.S. national weather service stations are called ASOS (Automated Surface Observing Systems)

̶        Federal aviation administration and department of defense are called AWOS (Automated Weather Observing Systems)

̶        ASOS reports cloud height and amount, visibility, precipitation type, intensity, and accumulation, obstructions to vision such as fog or haze, dewpoint temperatures, and wind direction, speed, and character (gusts, squalls)

̶        Data available on the internet

̶        Original data are coded using Meteorological Aviation Report format called METAR

̶        Data also plotted on meteograms (graphs that show how several atmospheric properties change with time)

̶        Meteorologists use meteograms to analyze the structure of hazardous weather events and track their progress as they move between stations

Ø  Rawinsondes

̶        Rawinsondes are primary instrument packages used to make these measurements (through the depth of the troposphere and well into the stratosphere)

̶        Is a balloon-borne instrument system that measure pressure, temperature, dewpoint temperature, wind direction, and speed?

̶        Launched worldwide twice a day at 0000 UTC and 1200 UTC

̶        Data collected are plotted on a diagram that depicts pressure on the vertical axis and temperature (Celsius) on the horizontal axis

Ø  Radar

̶        A device that transmits pulses of microwave energy

̶        When microwaves encounter objects, such as raindrops and hailstones, some of the energy is scattered back toward the antenna.

̶        The antenna gathers its energy (radar echo) and passes it through other electronic device called a receiver

̶        The amount of energy that returns to the radar depends on 3 parameters:

1.    Size of precipitation particles

2.    Type of particles (ice crystals, rain, hail)

3.    Number of particles in the beam

̶        Radar reflectivity allows meteorologists to estimate the rain rate

̶        To display radar reflectivity meteorologists use logarithmic or decibel scale which is denoted as dBZ

Ø  Wind Profiling

̶        Type of Doppler radar that operates with very high frequency (VHF) and ultra high frequency (UHF) radio bands.

̶        Antenna is an array of cables called a Phased Array Antenna

̶        Array transmits electromagnetic radiation with a slight time delay from one side to the other across the array - delay creates a beam of radiation that points in a specific direction

̶        By using three beams and trigonometry a vertical profile of the wind can be obtained

̶        RASS (Radio Acoustic Sounding System) transmits an acoustic (sound) wave in the vertical direction

̶        Speed of sound is related to the temperature of the air through which the acoustic wave is passing

̶        WSR-88D (Doppler) radar are obtained through mathematical manipulation of the radial velocity measurements all around the radar

̶        WSR-88D can also detect motion within about 20 km of the radar site

Ø  Satellites and Satellite Imagery

̶        Found in 2 types of orbits (Geostationary orbits and Low-Earth orbits)

̶        Geostationary Orbits: circular orbit lying in the earth’s equatorial plane in which a satellite has the same rotational velocity as the earth, must be 35,800 km up

̶        Low-earth Orbits: several hundreds of thousands of km up, near polar orbit (crosses the equator), view small part of the earth, clear view of polar regions

̶        Three primary channels are used when weather monitoring:

1.    Visible: measures solar radiation reflected from the earth or atmosphere at a frequency visible to the human eye (like sitting on a satellite viewing the earth in black and white)

2.    Infrared: Tuned to be sensitive to infrared electromagnetic radiation that the earth emits. Lower clouds are warmer so they give off more radiation then the cooler higher clouds in the troposphere

3.    Water Vapor Channels: Measures radiation at a specific infrared frequency that is sensitive to radiation emitted from water vapor molecules in the atmosphere, allows meteorologists to monitor during both clear and cloudy situations

Ø  Commercial Aircraft Measurements

̶        Various types of systems used are collectively named AMDAR (aircraft meteorological data reporting) systems

̶        Meteorological data is reported to the National Weather Service (NWS) and is used to develop weather forecasts

Ø  Lightning Detection

̶        NLDN (national lightning detection network) and CLDN (Canada LDN) map out the location of all cloud-to-ground lightning strikes in the US and Canada

̶        Consists of remote, ground based sensing stations

̶        Direction, time of arrival, and other characteristics of electromagnetic waves created

̶        Triangulates using three or more receivers to determine the position, time, strength, and polarity