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Category Archives: Climate
Does fall give any hints about the intensity of the coming winter?
Each winter we keep track of the areal extent of air colder than 23 degrees Fahrenheit at the 850 mb pressure level (about 1 mile above sea-level) around the entire Northern Hemisphere. This measure allows us to characterize the intensity of the winter season with respect to the lower tropospheric temperature.
Over the past 75 seasons there has been a systematic decrease in the December-January-February, or DJF, average areal extent of about 4.6%, and this is an unequivocal sign of global warming, measured in the winter season. Continue reading
What is the National Climate Assessment?
The U.S. National Climate Assessment is mandated by the Global Change Research Act of 1990. The assessment is conducted about every four years and is an authoritative scientific analysis of climate change risks, impacts and responses in the U.S.
The nation this month completed the Fifth National Climate Assessment, or NCA5. The National Oceanic and Atmospheric Administration is the administrative agency for NCA5 and certifies that the report meets Information Quality Act and Evidence Act standards. The assessment is an extensive process that includes internal and external review from federal agencies, the general public and external peer review by a panel of experts. Continue reading
Category: Climate, History, Seasons, Severe Weather
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Higher overnight lows led to warm September
As we enter the month of October and the traditional end of the warm season, it’s interesting to note that the average temperature last month, through Sept. 28, was 4.0 degrees above normal in Madison.
That is by far the biggest deviation among traditional warm-season months — June, July, August and September. All were warmer than average this year: June was 0.8 degrees, July just 0.5 degree and August only 1.2 degree above the respective norm. Continue reading
Are daily weather forecasts affected by climate change?
As it turns out, predictions of the coming weather are nearly exclusively dependent on the observed conditions of the atmosphere in the day prior to the forecast period. Continue reading
Category: Climate, Meteorology, Uncategorized
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Are computers used in weather forecasting?
Weather forecasting is a challenging and fascinating aspect of meteorology. An accurate forecast requires a thorough knowledge of all the variables of the atmosphere. There are also conservation principles of momentum, mass, energy and moisture, combined with the ideal gas law from chemistry that forecasters must consider.
The physical principles are represented as equations, and with current weather conditions, are used to solve for variables meteorologists care about — wind, temperature and precipitation. Computers are used in numerical weather prediction to solve these mathematical models to predict the weather based on current weather conditions. Continue reading
