## Shortcuts to Prediction

Efforts to develop "calculating aids" to convert between different temperature scales, correct barometer readings, and compute atmospheric variables that could not be measured directly had started in the 19th century. By the beginning of the 20th century, calculating aids were being used to compute wind values from pressure data and rates of pressure change from temperature and pressure, and to make specialized calculations better solved with graphs.

Stations reported temperatures in Celsius, Fahrenheit, and Reamur depending on their location, and the temperatures had to be converted to Celsius before making calculations. Barometers often registered different air pressure values depending on air temperature, so there were special calculations to account for temperature before computing the final pressure. Humidity had to be calculated from simultaneous measurement of wet- and dry-bulb temperatures. For all of these calculations, meteorologists created special tables that allowed users to connect their observation data with the desired value.

The Bjerkneses created a graphical calculus that allowed meteorologists to determine the vertical velocity of air strictly on the basis of the horizontal wind speed and direction over a large area. The Japanese meteorologist Sakuhei Fujiwara (18841950), chief of the Central Meteorological Bureau in Tokyo, Japan, created a special scale printed on clear plastic film that helped to compute the vorticity (amount of spin) in the atmosphere. The gradient wind scale was placed over the weather map and adjusted until the distance between the lines on the scale matched the distance between the lines of equal pressure on the map. The vorticity could then be read off the overlay.

In 1925, the British meteorologist Shaw created a thermodynamic diagram called the tephi-gram (TEFF-ee-grahm). Weather balloons carrying instruments aloft recorded pressure, temperature, and humidity values. The data were plotted on the tephigram, and the resulting lines could be interpreted to determine cloud heights, relative amounts of moisture in the atmosphere, maximum and minimum temperatures for the next day, and time when fog and low clouds would clear.

Other calculating aids called nomograms allowed forecasters to enter two or three different variables, connect the values with a ruler, and find the desired variable. For instance, one nomogram required the meteorologist to know the pressure gradient (difference in pressure), the latitude of the observation, and the radius of curvature of the closest constant pressure line. Once the values were entered into the nomogram, the forecaster could find the velocity of the wind resulting from the pressure gradient. In this way, meteorologists could determine the wind velocity in areas lacking observation stations. Nomograms were popular with forecasters because they saved time and increased accuracy but are less common now because of the use of computer-generated forecasts. Meteorologists still use thermodynamic diagrams like the tephigram to identify the altitude and vertical extent of cloud formations.

DEW POINT NOMOGRAM

Dry-bulb Wet-bulb Dew point temperature temperature go°F

then divide by 1.8 to obtain °C © Infobase Publishing

then divide by 1.8 to obtain °C © Infobase Publishing

Nomograms, like this one for calculating the dew point temperature, provide convenient methods for calculating desired meteorological information.

creation was ordered by President Franklin D. Roosevelt (1882-1945), was composed of some of the most respected scientists in the United States, including Robert A. Millikan and the Massachusetts Institute of Technology (MIT) president, Karl T. Compton (1887-1954). In late 1933, they recommended that the Weather Bureau adopt Bergen School methods. By the next year, the Weather Bureau had hired three young meteorologists with Ph.D.'s to train its forecasters. Fronts appeared on U.S. weather maps for the first time in 1936.

Although the use of Bergen School techniques could have led to improved forecasts, often they did not. Air mass analysis and frontal analysis depend on accurate data from closely spaced weather stations. Furthermore, forecasters had to be extremely skilled in their use of data to locate frontal and air mass boundaries. When stations are hundreds of miles apart, as they are in the United States, the location of the front may be difficult to find. Without the benefit of satellite pictures and radar, forecaster judgment was the most critical component of successful predictions.

## Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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