Air masses and its types

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  Air masses and its types
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  • 1. Subject: Geography Class: MSc (Ist) Roll# 7826 Submitted to: Mam Nusrat parveen Submitted by: Fakhara younas Semester: Ist “morning” Department of Geography GC University Fsd
  • 2. AIR MASSES AND ITS TYPES AIR MASSES: An air mass is large body of air with similar temperature and humidity. Air masses form in stable “source regions” such as in the sub tropics or near to the poles. A region under the influence of an air mass will probably experience generally constant weather conditions, a situation referred to as “air mass weather”.
  • 3. TYPES OF AIR MASSES: CONTINENTAL AIR MASS MARITIME AIR MASS t Tropical w warmer p Polar k Kalt (cold) m Maritime s stable c continental u unstable INDEX
  • 4. CONTINENTAL AIR MASS: • A continental air mass has a uniform temperature and moisture profile. As with all air masses, the characteristics of the air are the same as the region from which the large mass of air originated. In the case of any air mass labeled as continental, the air originated over a large landmass and is usually dry. • MARITIME AIR MASSES: • The maritime tropical air mass of originates Atlantic ocean east of Florida over the Bahamas Ireland .over the pacific ocean. Lower California is, a source region of another maritime tropical (mt) air mass. A maritime or oceanic air mass has a uniform temperature and moisture profile. The characteristics of the air mass are the same as the region from which the large mass of air originated. In the case of any air mass labeled as maritime, the air originated over a large body of water and is usually moist.
  • 5. TYPES OF CONTINENTAL AIR MASSES 1. TROPICAL (cT) 2. MID LATITDUE (CM) 3. POLAR (CP) TROPICAL (cT) A hot dry continental tropical (cP air mass originates over Northern Mexico, Western Texas, New Mexico and Arizona during the summer. The source region for cT air is the desert South west, the high plains and Mexico. The air has low dew points and warm to hot afternoon temperatures but with mild nighttime temperature. Due to the buoyancy and elevation of cT air across North America, this air will advect into the mid-levels of the atmosphere once it moves out of its source region. This creates a cap of mild dry air. If this air adverts over PBL MT air, the severe thunderstorm threat increases significantly. The boundary of cT is most noticeable with the creation of a dry line. A dry line separates mT air from cT air. Depending on the strength of the dry line, convergence along the dry line and the dynamics above the dry line, severe thunderstorms can form near a dry line boundary.
  • 6. POLAR (cP): • The continental polar (cp) air mass of North America, originates over north-central Canada. This air mass has low dew points, cold temperatures and a high degree of stability. The denseness of cP air creates surface high pressure and a trough aloft, especially when cP air moves into lower latitudes. Precipitation in association with cP air is usually light due to the dryness and low moisture capacity of the air. Precipitation is most common on the "edges" of cP air, especially where it intersects and displaces mT air. Precipitation within a cP air mass is elevated and dynamically induced. These dynamical uplift mechanisms include jet streaks, isentropic lifting and positive differential vortices advection. Cold surface temperatures and a dry boundary layer inhibit thermodynamic convection.
  • 7. TYPES OF MARITIME AIR MASS: 1. TROPICAL (mT) 2. MID LATITUDE(Mm) 3. POLAR (mP) MARITIME TROPICAL (mT): The maritime tropical air mass is most often felt in the Southeast US. In the winter this air mass is shoved toward the equator but in summer it can cover much of the US east of the Rockies. This air mass results from the warm waters of the Gulf of Mexico and Gulf Stream. The warm waters in this region evaporate an enormous volume of water. Cold water currents tend to stabilize the atmosphere and produce little evaporation while warm waters destabilize the atmosphere and add moisture. The warm waters warm the low levels of the atmosphere.
  • 8. MARITIME POLAR (mP): • The maritime polar (mP) air mass originates over the north pacific and bearing strait north Atlantic ocean north American region. The source region for mP air is over cold ocean currents or high latitude ocean waters. This air does not have the moisture content as mT air. Since mP air is always near saturation, orographic lifting of the air mass can produce widespread rain or snow. This air mass is notorious for producing fog, drizzle, cloudy weather and long lasting light to moderate rain. The temperature of MP air ranges from just above freezing to below 70 ° F. mP air is modified as it moves over elevated terrain. On the windward side of mountain ranges, MP air can produce an abundance of rain and snow. Once on the lee side of mountains, the mP air mass modifies into a continental air mass. These air masses produce cold fronts but the air is not as cold as polar or arctic fronts. They are often termed "Pacific fronts.
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