Understanding Weather Hazards: Whiteout Conditions
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Questions and Answers

What type of fog is associated with a warm front?

  • Post-frontal fog
  • Pre-frontal fog (correct)
  • Radiation fog
  • Desert fog

    • What is the OCDS-II example illustrating?

  • Visibility Climogram
  • WSCC example
  • Radiation Fog Point
  • OCDS-II (correct)

    • What does the Fog Stability Index (FSI) thresholds indicate?

  • Favorable conditions for dust advection
  • Snowfall intensity limits
  • Radiation fog formation likelihood (correct)
  • Dust lofting wind speeds

    • Where can you find the Threshold dust-lofting wind speeds for different desert environments?

    <p>Table 1.2</p> Signup and view all the answers

    What do Fog threat thresholds indicate?

    <p>Radiation fog formation likelihood</p> Signup and view all the answers

    What should be examined at the 850 mb level to determine the presence of a nocturnal low-level jet stream?

    <p>Wind speeds</p> Signup and view all the answers

    Why are surface winds of at least 15 knots usually needed to loft dust?

    <p>To have sufficient force to lift and transport dust particles</p> Signup and view all the answers

    Which wind direction in Iraq is favorable for dust lofting?

    <p>North or northwest</p> Signup and view all the answers

    When does dust generally start to settle at the surface according to the text?

    <p>After dark once the nocturnal radiational inversion develops</p> Signup and view all the answers

    Why is analyzing wind speeds at the 925 mb level important?

    <p>To strengthen wind speeds at the surface and enhance dust lofting potential</p> Signup and view all the answers

    What is often conducive to momentum transfer from aloft that can enhance surface winds?

    <p>Dry low-level air</p> Signup and view all the answers

    What is the key ingredient required for dust storm generation after an appropriate source?

    <p>Lofting of dust particles by strong winds</p> Signup and view all the answers

    What is the role of wind shear in the lofting of dust particles?

    <p>Creating turbulence in the boundary layer</p> Signup and view all the answers

    At what range of wind speeds do the first sand and dust particles from 0.08 to 1 mm in diameter start to move?

    <p>15 to 25 knots</p> Signup and view all the answers

    What happens to the intensity of a dust storm even when wind speeds slow down?

    <p>It remains the same</p> Signup and view all the answers

    What is one of the effects of lakes drying up on soil and plant growth?

    <p>Inhibition of plant growth</p> Signup and view all the answers

    Which natural phenomenon in southern Iraq is responsible for many dust storms in the region?

    <p>Shamal events</p> Signup and view all the answers

    What does the Pollution Trapping Index (PTI) value indicate when it is greater than -40?

    <p>Minimal pollution trapping potential</p> Signup and view all the answers

    How is the Pollution Trapping Index (PTI) calculated?

    <p>PTI = -1.0 X (LAPSE + WIND^2)</p> Signup and view all the answers

    What do the blowing snow products from GEPS and MEPS indicate?

    <p>Indicate strong winds and snow accumulation but not necessarily visibility reduction</p> Signup and view all the answers

    Why could a drop in prevailing visibility from 25 miles to 15 miles be significant?

    <p>It may signal an unnoticed increase in low-level moisture</p> Signup and view all the answers

    What role does experience play in visibility forecasting according to the text?

    <p>Experience plays a significant role in visibility forecasting</p> Signup and view all the answers

    Why is sector visibility mentioned as significant in visibility forecasting?

    <p>Significant differences could suggest important occurrences</p> Signup and view all the answers

    What characteristics are important to consider when forecasting fog?

    <p>Synoptic situation, time of year, and station climatology</p> Signup and view all the answers

    Under what conditions may fog develop or intensify?

    <p>When air is supersaturated with respect to water in the presence of cloud condensation nuclei</p> Signup and view all the answers

    What must be the relationship between air temperature and dew point for fog to form?

    <p>Air temperature must equal the dew point (RH = 100%)</p> Signup and view all the answers

    What is a factor that contributes to the formation of visible cloud droplets in fog?

    <p>Presence of dust, soil, and other minerals in the air</p> Signup and view all the answers

    Which of the following is NOT a characteristic important to consider when forecasting fog?

    <p>Amount of precipitation in the area</p> Signup and view all the answers

    What does it mean for an air mass to be supersaturated regarding fog formation?

    <p>It has a relative humidity slightly greater than 100%</p> Signup and view all the answers

    Based on the text, which chart is used for contrail forecasting?

    <p>Appleman chart</p> Signup and view all the answers

    In the context of aircraft engines, what does the Appleman chart for high-bypass and low-bypass engines refer to?

    <p>Engine bypass type</p> Signup and view all the answers

    What do Planck curves for black bodies represent?

    <p>Emission of energy by an object</p> Signup and view all the answers

    Which table in the text compares the temperature of an object with its emitted energy?

    <p>Table 2.15</p> Signup and view all the answers

    Based on the text, which figure provides information on probabilities of contrail formation based on temperature and pressure level?

    <p>Figure 2.44</p> Signup and view all the answers

    What are the key factors influencing the duration of advected dust?

    <p>Depth of the dust and wind speed</p> Signup and view all the answers

    Which synoptic situation may change both the wind direction and the probability of dust advecting into an area?

    <p>Cold frontal passage</p> Signup and view all the answers

    What is a potential source of dust generation in agricultural areas?

    <p>Mechanical breaking of soil</p> Signup and view all the answers

    In which type of region can dust plumes be generated in advance of cold fronts?

    <p>Coastal areas</p> Signup and view all the answers

    What environmental condition is most prevalent in deserts where dust storms occur?

    <p>Scarce rainfall</p> Signup and view all the answers

    What factor can lead to increased dust potential beyond 36 hours following a rainstorm?

    <p>Soil evaporation after heavy rain</p> Signup and view all the answers

    What are the three major varieties of frontal dust storms mentioned in the text?

    <p>Prefrontal, postfrontal, shear-line</p> Signup and view all the answers

    What is the primary factor that distinguishes frontal dust storms from shamals?

    <p>Scale of the weather systems</p> Signup and view all the answers

    In which quadrant of a jet streak is there an increase in upward vertical velocities according to the text?

    <p>Left-front</p> Signup and view all the answers

    What are prefrontal winds called in Saudi Arabia according to the text?

    <p>Kaus</p> Signup and view all the answers

    Why are prefrontal dust storms difficult to detect in METSAT imagery?

    <p>Their short-lived nature</p> Signup and view all the answers

    What is the average wind speed range for prefrontal dust storms according to the text?

    <p>$15-20$ knots</p> Signup and view all the answers

    What does a negative Lifted Index (LI) value (less than -2) indicate?

    <p>High likelihood of convection later in the day</p> Signup and view all the answers

    When determining the maximum relative humidity (RH) in the 700 mb to 400 mb layer, what RH percentage is associated with precipitation aloft?

    <p>Around 90%</p> Signup and view all the answers

    What is the impact of water droplets falling into a deep, dry planetary boundary layer (PBL)?

    <p>Cools and moistens the PBL</p> Signup and view all the answers

    In which layer and at what temperature do ice crystals form from water vapor according to the text?

    <p>700-400 mb layer at temperatures below -5°C</p> Signup and view all the answers

    What is the significance of high relative humidity (above 90%) at temperatures below -5°C in the 700-400 mb layer according to the text?

    <p>Strengthens potential downdrafts</p> Signup and view all the answers

    What does analyzing mid-level moisture aim to assess in atmospheric conditions?

    <p>Negatively buoyant downdraft potential</p> Signup and view all the answers

    What typically delineates the top of the planetary boundary layer where haze layers are found?

    <p>A temperature inversion and a cessation of vertical mixing</p> Signup and view all the answers

    Under what conditions can haze persist for days according to the text?

    <p>When atmospheric conditions are stagnant and there is no cleansing mechanism like precipitation</p> Signup and view all the answers

    What atmospheric conditions can favor the formation of sulfate aerosols, leading to the creation of haze?

    <p>Plenty of sun, increasing boundary layer moisture, and limited mixing</p> Signup and view all the answers

    What factor can lead to the dissipation of haze according to the text?

    <p>Thermal instability or increase in wind speeds</p> Signup and view all the answers

    What range of visibility is typically restricted by haze according to the text?

    <p>Less than 1 mile occasionally</p> Signup and view all the answers

    In what regions can elevated haze layers occur according to the text?

    <p>Regions downstream from where particles are lofted above the PBL by cumulus clouds</p> Signup and view all the answers

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