Is warmer air ‘heavier’?

Posted on July 5, 2018 by WeatherGuys Editor

Explore physics involved in hitting a baseball
via the CIMSS Baseball WebApp at
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We are now in the heart of the baseball season and even the casual fans begin to tune in a bit more regularly to the summer game. One of the long-standing pieces of baseball wisdom suggests that the heat and humidity of oppressive summer heat waves render the air “heavy” and lead to a decrease in offensive power, particularly in home runs.

The veracity of this “wisdom” is testable.

The air we breathe is a mixture of many gases (but mostly molecular nitrogen and oxygen). Since we know the constituents and their fractional amounts, it is fairly easy to determine the molecular weight of the mixture.

The most highly variable constituent of the mixture is water vapor, so it is useful to calculate the molecular weight of so-called “dry air” — air without any water vapor in it. That weight is 29.87 grams/mole. The molecular weight of water vapor (water as a gas) is only 18.02 grams/mole.

Consequently, when any amount of water vapor is mixed into dry air, the resulting mixture is less massive than the purely dry air. On the very humid days that attract our attention in the summer, this effect is at its height and the weight of the humid mixture is often much less than that of dry air. Sir Isaac Newton was the first to demonstrate this truth.

Thus, this piece of baseball “wisdom” is utterly false — it is much more likely that any decrease in power production observed during a mid-summer heat wave is a function of the human body’s inability to perform at its peak efficiency in the heat and humidity. It is definitely not because the air is “heavier.”

Category: Meteorology, Phenomena

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Is climate science becoming a political issue?

Posted on June 25, 2018 by WeatherGuys Editor

Last week a group of four Republican U.S. senators — Ted Cruz, Rand Paul, James Lankford and Jim Inhofe — wrote to the inspector general of the National Science Foundation attacking its support of the Climate Matters program.

The program offers short courses, webinars and graphical data for broadcast meteorologists to incorporate discussion of climate change when appropriate in their broadcasts.

By doing so, the program seeks to leverage the general public’s frequent and familiar contact with atmospheric science, through television weather broadcasts, as a means to contributing to public education on this important topic.

The senators argued that the foundation’s support of the Climate Matters program goes beyond its mandate to fund basic research and represents a violation of the 1939 Hatch Act, which prohibits government agencies from engaging in partisan activities.

These senators, and large numbers of their colleagues, are now many years into a relentless effort aimed at convincing the country that the carefully argued, peer reviewed scientific evidence and conclusions regarding the reality and accelerating threat of global warming is a hoax.

They have essentially encouraged the mistaken belief that the science is politically motivated and now argue that the foundation is in the business of funding “partisan” efforts in science education.

This is rather like asserting that 2+2=5, counter to the analytical conclusions reached by nearly all mathematicians, and then demanding that public funding of mathematics education and outreach be stopped on the basis that the 2+2=4 crowd is “partisan.”

The scientific consensus on climate change is not a political viewpoint — a reality perhaps best illustrated by the recent statements of the new NASA Administrator James Bridenstine, formerly a congressman from Oklahoma and climate change skeptic.

Only a month into his new job, when asked about his stance on the issue, he said, “I … know that the climate is changing. I also know that we human beings are contributing to it in a major way. … We’re putting (CO2) into the atmosphere in volumes that we haven’t seen, and that greenhouse gas is warming the planet.”

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month.
Category: Climate

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Did weather forecasting play a role in D-Day?

Posted on June 11, 2018 by WeatherGuys Editor

Had the Allies delayed the D-Day invasion of Europe that began June 6, 1944 with the landings on the beaches at Normandy, the combination of lunar cycle, tides and weather almost certainly would have postponed the invasion for more than a month likely costing the effort the tremendous advantage of secrecy. (Photo Credit: Associated Press Archives)

Wednesday was the 74th anniversary of the Allied invasion of Europe that began with the landings on the beaches at Normandy.

The combined land, air and sea assault of June 6, 1944, remains the largest such event in history. The success of the invasion was extraordinarily dependent on weather conditions.

More than three months before the invasion, a combined British and American forecasting team began rigorous forecast exercises designed to iron out the physical and logistical kinks of such a coordinated effort.

As June drew near, the nature of this collaboration was still problematic as the two groups employed vastly different methods in fashioning the requisite three- to five-day forecasts. The British were attempting to make such forecasts based upon the understanding of atmospheric dynamics that had grown substantially during the war. The Americans were employing a method based on a statistically based search through old weather data for historical analogues that could be used to guide the forecast.

To maintain secrecy, a large portion of the Allied fleet was squirreled far away in northern Scotland. Consequently, five days of lead time was required to mobilize these forces. Thus, Gen, Dwight D. Eisenhower needed to know by May 31 whether the first week of June, the prospective target for the invasion, would provide favorable weather.

The forecasters foresaw a break in that year’s unusually stormy late spring and suggested June 5 would work. As the day approached, the team realized that a one-day postponement would offer better conditions, prompting Eisenhower to make the fateful decision to invade on June 6, under barely acceptable conditions.

Had the Allies delayed, the combination of lunar cycle, tides and weather almost certainly would have postponed the invasion for more than a month — likely costing the effort the tremendous advantage of secrecy.

Category: Meteorology

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If we stopped emitting carbon dioxide right now, would Earth stop warming?

Posted on June 4, 2018 by WeatherGuys Editor

No. Objects, even the atmosphere, will warm as long as the energy gains exceed the energy losses to their environment.

When the energy gains balance the energy losses, the object’s temperature remains constant. If the carbon dioxide levels were to suddenly remain constant, the atmosphere would continue to warm.

The orange line in this graph shows committed warming if greenhouse gases were held constant from the year 2000, the other lines show warming with continued fossil fuel use.

Climate models estimate that it will take about 40 more years for the temperature to stabilize at a temperature higher than today’s global mean temperature. This decades-long lag is due in part to the long time it takes to heat the oceans.

The energy increases due to higher carbon dioxide concentrations does more than warm the air, it heats the ocean. It takes more energy to raise the temperature of water than air. Once the ocean temperature is elevated, it will release heat back to the air, and be measured as surface warming.

Once the carbon dioxide is released into the atmosphere, from the burning of fossil fuels as an example, it accumulates and will remain in the atmosphere for many decades. Carbon dioxide moves among the atmosphere, the oceans, the land and the biosphere. Eventually, after many millennia the carbon dioxide in the atmosphere may be stored in rocks and as part of marine organisms’ shells that settle to the bottom of the ocean. Of course it is more complicated than just the amount of carbon in the atmosphere, there are feedbacks that enhance warming. For example, melting ice and snow increases the amount of solar energy our planet absorbs, increasing our energy gains and warming. A warmer atmosphere results in more atmospheric water vapor, which, like carbon dioxide, is a greenhouse gas and further warms the atmosphere.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison Department of Atmospheric and Oceanic Sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month.
Category: Climate, Meteorology

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Is this hot start to summer unusual?

Posted on May 29, 2018 by WeatherGuys Editor

Jet stream winds. Credit: Climate Reanalyzer

Beginning on Saturday, Madison has experienced two straight days in May at or above 90 degrees for the first time since 1991 and for only the third time in nearly the last half-century (the others were in 1975 and 1978).

What’s more, the forecast is for temperatures to soar into the mid-90s again Memorial Day and Tuesday which, if it happens, would be the first time since at least 1971 (and perhaps in its history) that Madison has had four consecutive May days at or above 90.

The underlying causes of this remarkable heat are circumstantial. First, and perhaps most importantly, the jet stream is well north of its normal position for this time of year. Currently located in central Canada, the jet is in a location more common for late July and August. Since the jet is tied to regions of large horizontal temperature contrast, its current position ensures that locations even as far north as Madison are on the warm, tropical side of the hemispheric flow.

In addition, a reasonably strong upper-level trough exists over southern California which has been promoting broad southerly and southwesterly air flow from the Desert Southwest to the High Plains. This has placed a wide expanse of exceptionally warm air just to our west and southwest, ensuring a prolonged period of very warm temperatures over the western Great Lakes states.

So, the warmth we are likely to continue experiencing for the next couple of days is quite unusual for this time of year. Such a warm start to our summer season does not, however, suggest anything at all about the remainder of the summer in terms of warmth. The circumstances of the hemispheric flow patterns that have conspired to create this heat wave may, or may not, conspire again this season.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison Department of Atmospheric and Oceanic Sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month.
 
Category: Climate, Meteorology, Seasons

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