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Wednesday, February 23, 2011

South Pole Meteorology

A significant percentage of the station personnel is dedicated to meteorology: 4 people in the summer and 2 in the winter.  That is about 3~4% of the population.  Now think about how many meteorologists you know back home and you will realize that meteorology at the South Pole is a big and important deal.  It is important because we are one of the few stations on the continent able to provide measurements year-round; it is a big deal because we maintain a skiway in the summer and need to provide accurate weather observations for air operation.   Short-term local weather forecasting is part of the job as well, as is the launch of balloons, twice a day. 
In addition to the meteorologists, we have two full-time employees from the National Oceanic and Atmospheric Administration (NOAA).  They do atmospheric measurements, including cloud coverage, air quality, analysis of particulates, carbon dioxide, concentration of ozone and ozone-depleting CFC gases, UV radiation, solar irradiance, albedo, and other parameters. 

Many measurements, such as temperature, humidity, barometric pressure, wind speed, etc, are automated but, much to my surprise, several critical measurements are still performed by humans and are fairly subjective and qualitative.  Every hour during the summer the meteorologist on shift climbs on the roof, looks over the horizon, and checks visibility, horizon definition, and surface definition.  Visibility is defined by the ability of the meteorologist to discern black boards positioned at half mile intervals from each other in different directions on the ice.  Horizon and surface definition are reported as good, fair, poor, or nil.  There are standardized criteria to follow, but I am sure there still is some subjectivity in the observations - surprising in the age of computers and image processing.  All of these observations are critical, as they are reported to aircrafts and form the basis for decisions on whether it is safe to land.  I went on the roof with Rolf on Feb 3 to see how well matched my eyes were to his, and discovered that I can use some eye calibration.

Phil, another one of our summer meteorologists, prepares a balloon launch at our Balloon Inflation Facility (BIF) on Feb 4.  The BIF is adjacent to the cryogenic facility, so the balloons can be inflated with the Helium that evaporates from the storage dewars, which would otherwise be wasted.

Phil checking the proper inflation of the balloon by measuring its lift force.  The balloon must provide enough upwards force to lift the weight of the measurement instruments attached to it.

Lindsay, who was visiting the science projects at the South Pole for just a few days, is given the privilege of releasing the balloon to the skies.

The balloon climbs at a rate of ascent of about 1,000 ft per minute, or about 12 mph.  It expands as it climbs up to 100,000 ft of elevation, until it bursts and falls back down to earth. 

As soon as the balloon is released, Phil comes back into the BIF and checks in real time the data transmitted by the on-board instruments to make sure that the launch is successful.  The data is recorded and then transmitted to meteorological centers around the world, where it becomes an input to complex weather forecasting models.

Here Christy, one of the two NOAA scientists, is about to release the NOAA balloon on Feb 2.  This is a much bigger balloon than the one launched by the meteorologists, because it carries a much heavier payload, consisting of instruments used to measure ozone concentrations.

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