TOTAL PRECIPITABLE WATER & CLOUD LIQUID WATER

TOTAL PRECIPITABLE WATER

TOTAL PRECIPITABLE WATER Total precipitable water (TPW) is a microwave product that represents the depth of liquid water that would be accumulated if all the water vapour in a hypothetical cylinder above a location on the earth were condensed into an equivalent amount of liquid water. Because microwave instruments are able to sense energy through most clouds, we can create products that depict atmospheric constituents from the sea surface to the top of the troposphere.

TOTAL PRECIPITABLE WATER Traditional infrared water vapour imagery using the 6.7-micrometer channel detects water vapour mainly at middle and high levels of the troposphere. TPW imagery on the other hand depicts the moisture present at all levels, especially important for the low levels where most water vapour is concentrated.

CLOUD LIQUID WATER DEFINITION Cloud Liquid Water (or CLW) is the analog of TPW. It represents the depth of liquid that would be accumulated if all the cloud droplets in a vertical column were compressed into an equivalent depth of liquid water.

WV & TPW

TPW Arrow D shows the extent of the low-level water vapor, It was almost impossible to determine the low-level water plume from the two GOES images (IR and WV) provided. WV channel is sensitive to high-level water vapor, and the infrared window image depicts the tops of clouds, not water vapor in the atmosphere. It neither shows low-level water vapor. TPW imagery, supplied here by the Special Sensor Microwave Imager (SSM/I), helps to see that the low-level moisture plume is considerably narrower than the high-level moisture plume shown in the water vapor image. TPW values are about 100 times greater than CLW. In other words, a typical vertically integrated column of cloudy air contains roughly 100 times more water in vaporous form than in liquid form.

TPW & CLW TPW depicts the liquid water equivalent of all of the water vapour present in a hypothetical cylinder above the satellite's footprint. IR & WV imagery detect only high-level moisture. TPW imagery depicts low and mid-level moisture. TPW values are larger over low latitudes where more water vapor is present. Unlike WV imagery, TPW imagery detects moisture concentrated in the lower layers of the atmosphere. Cloud Liquid Water represents the depth of liquid from cloud droplets in a hypothetical cylinder above the satellite's footprint compressed into an equivalent depth of liquid water. Both TPW & CLW are valid over water only. Clouds are naturally discontinuous in the atmosphere, and there are many regions with no clouds and CLW values of zero.

ATMOSPHERIC RIVER The term was originally coined by researchers Reginald Newell and Yong Zhu of the Massachusetts Institute of Technology in the early 1990s, to reflect the narrowness of the moisture plumes involved. An atmospheric river is a narrow corridor or filament of concentrated moisture in the atmosphere. Consist of narrow bands of enhanced water vapor transport, typically along the boundaries between large areas of divergent surface air flow, including some frontal zones in association with extratropical cyclones that form over the oceans.

ATMOSPHERIC RIVER They are typically several thousand kilometres long and only a few hundred kilometres wide, and a single one can carry a greater flux of water than the Earth's largest river, the Amazon River. There are typically 3-5 of these narrow plumes present within a hemisphere at any given time. Have a central role in the global water cycle. On any given day, and account for over 90% of the global meridional (north-south) water vapor transport, yet they cover less than 10% of the Earth's circumference. Major cause of extreme precipitation events which cause severe flooding in many mid-latitude, westerly coastal regions of the world, including the West Coast of North America,western Europe, and the west coast of North Africa.

PINEAPPLE EXPRESS It is a non-technical term for a meteorological phenomenon characterized by a strong and persistent flow of atmospheric moisture and associated with heavy precipitation from the waters adjacent to the Hawaiian Islands and extending to any location along the Pacific coast of North America. A Pineapple Express is an example of an atmospheric river, which is a more general term for such narrow corridors of enhanced water vapor transport at mid-latitudes around the world

CAUSES AND EFFECTS A Pineapple Express is driven by a strong, southern branch of the Polar jetstream and is marked by the presence of a surface frontal boundary which is typically either slow or stationary, with waves of low pressure travelling along its axis. Each of these low pressure systems brings enhanced rainfall. The conditions are often created by the Madden-Julian oscillation, an equatorial rainfall pattern which feeds its moisture into this pattern. They are also present during an El Niño episode. The composition of moisture-laden air, atmospheric dynamics, and orographic enhancement resulting from the passage of this air over the mountain ranges of the western coast of North America causes some of the most torrential rains to occur in the region. Pineapple Express systems typically generate heavy snowfall in the mountains and Interior Plateau, which often melts rapidly because of the warming effect of the system. After being drained of their moisture, the tropical air masses reach the inland prairies as a Chinook wind or simply "a Chinook", a term which is also synonymous in the Pacific Northwest with the Pineapple Express.

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