Do oceans have heat waves?

Posted on September 16, 2024 by WeatherGuys Editor

As with the atmosphere, oceans can experience heat waves. The National Weather Service defines an atmospheric heat wave as a period of abnormally hot weather generally lasting more than two days. To be considered a heat wave, the temperatures must be outside the historical averages for a given area.

The magnitude of marine heatwaves (MHW) in the past 30 days is calculated using the daily high-resolution sea surface temperature (SST) dataset hosted at NOAA’s Physical Sciences Laboratory. (Image credit: NOAA/PSL)

Marine heat waves are defined as any time the ocean temperatures are warmer than 90% of the previous observations for the region at a given time of year. Marine heat waves can last for weeks, months and even years.

Marine heat wave conditions are monitored and forecast by NOAA. The National Data Buoy Center collects and disseminates quality-controlled marine observations. Global ocean surface temperatures are also monitored using satellite observations. In July 2024, 35% of the global ocean experienced marine heat waves.

The world’s oceans are heating up. Processes like marine heat waves and El Niño/La Niña make it a challenge to untangle the causes of warming anomalies for a specific year or region. However, analysis of the ocean temperature over decades shows the warming trends result from the observed increases in atmospheric carbon dioxide, just like the observed warming trend in atmospheric temperatures.

Warmer waters influence atmospheric weather patterns, such as tropical storms. There are also impacts on marine ecosystems.

An unprecedented marine heat wave dominated the northeastern Pacific from 2013 to 2016. Called “the Blob” because of the large expanse of unusually high temperatures, it upended ecosystems across a huge swath of the Pacific Ocean. The warm temperatures attracted subtropical species rarely seen off the West Coast of the U.S. The krill that humpback whales typically feed on grew scarce, and they switched to feeding on high concentrations of anchovy. The higher temperatures fueled a record bloom of toxic algae that shut down West Coast crabbing from November 2015 through March 2016.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Climate, History, Seasons

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Is the Sun Playing a Role in the Earth’s Global Warming?

Posted on September 9, 2024 by WeatherGuys Editor

The sun helps maintain Earth’s climate to be warm enough for us to survive. Even subtle changes in Earth’s orbit around the sun have led to and ended past ice ages. This relationship between Earth’s climate and its orbit around the Sun is well known.

The Solar & Heliospheric Observatory (SOHO), is a project of international collaboration between ESA and NASA to study the Sun from its deep core to the outer corona and the solar wind. (Photo credit: NASA/SOHO)

The sun’s activity and appearance goes through cycles, with one solar cycle taking 11 years to complete. The current cycle began at the end of 2019 and will reach peak levels of activity in 2025. During a solar cycle, the amount of solar radiation reaching Earth varies.  These changes have a variety of effects on Earth’s atmosphere, including auroras.

The amount of solar energy Earth receives follows the sun’s natural 11-year cycle of small ups and downs with no net increase since the 1950s. During this same time period, our global temperature has increased over 0.8 degrees C. This warming of Earth over the last few decades is too rapid to be caused by the observed solar activity.

Greenhouse gases in the atmosphere raise the surface temperature through absorption of radiation at wavelengths Earth emits to space. These gases play a crucial role in Earth’s climate by affecting our energy budget. They warm the planet. The three most abundant greenhouse gases in Earth’s atmosphere are: water vapor, carbon dioxide, and methane.

Humans have been altering weather and climate on local and regional scales for centuries. One of those impacts is through activities that increase the concentrations of greenhouse gases. Since the beginning of the Industrial Revolution, human activities have increased atmospheric carbon dioxide amounts by over 50% and methane levels by 150%. These rates of increase align with the observed trends in global warming.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Climate, History

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How can the Upper Midwest get such high dew points every year?

Posted on September 3, 2024 by WeatherGuys Editor

The dew point temperature is a measure of the amount of water vapor in the atmosphere and is also a good way to tell how uncomfortable you might feel on a hot day. Hot days and high water vapor contents are a serious health risk for some. Also, high water vapor content is a key fuel for severe thunderstorms.

There are three primary sources of water vapor that address this question: advection of water vapor largely from the Gulf of Mexico, evaporation over the Great Lakes, and transpiration from corn fields. The contribution from the Great Lakes in summer is minimal in comparison to the other factors, except maybe near the shorelines.

The process of evapotranspiration. Corn tends to release more vapor because it is a taller plant and tends to use more water than most crops. (Image credit: USDA)

Southerly winds help bring warmer temperatures to the Upper Midwest but they also transport moisture from the Gulf of Mexico. This leads to higher dew points over Wisconsin and the Midwest. Studies have demonstrated that summertime precipitation in the Midwest is strongly correlated with the strength of this Great Plains low-level jet stream, which transports relatively warm, moist air northward from the Gulf of Mexico.

Transpiration is the release of water vapor from plant leaves. Transpiration has three main steps: the plant’s roots uptake water from the soil, the water moves through plant tissues, and the leaves release water vapor into the air through their stomata. During summer months, maturing cornfields become a huge source of water vapor to the atmosphere. Studies suggest a single acre of corn can transpire 3,000 to 4,000 gallons of water per day. On calm days, an analysis of dew points over the Midwest can identify the location of the Corn Belt. This transpiration by corn is sometimes referred to as “corn sweat.”

Together, these factors can result in summer dew points in the low to middle 70Fs for the Upper Midwest.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Climate, Phenomena, Seasons

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Does the U.S. have a new weather satellite?

Posted on August 26, 2024 by WeatherGuys Editor

Weather satellites fly around Earth in two basic orbits: a geostationary Earth orbit (abbreviated as GEO) and a low Earth orbit (abbreviated as LEO). LEO satellites’ orbits often travel over the Earth’s polar regions, flying at an altitude of 530 miles. Geostationary satellites orbit Earth as fast as Earth spins and so hover over a single point above Earth at an altitude of about 22,300 miles. To maintain its position, a GEO satellite must be located over the equator. In contrast, polar satellites go around from pole to pole as the Earth rotates beneath the satellite; each orbit is slightly to the west of the previous one.

Since 1975, Geostationary Operational Environmental Satellites (GOES) have provided continuous imagery and data on atmospheric conditions and solar activity (space weather). They have even aided in search and rescue of people in distress. GOES data products have led to more accurate and timely weather forecasts and better understanding of long-term climate conditions. The National Aeronautics and Space Administration (NASA) builds and launches the GOES, and the National Oceanic and Atmospheric Administration (NOAA) operates them. (Image credit: GOES-R.gov

Satellite observations provide valuable information to meteorologists. The United States usually operates two geostationary satellites called GOES (Geostationary Operational Environmental Satellite). One has a good view of the East Coast; the other is focused on the West Coast. They are a basic element of the U.S. weather monitoring and forecasting enterprise. The first GOES satellite, GOES-1, was launched in October 1975. Upgrades to the instruments are made as needed and the U.S. is currently in the fifth generation of GOES satellites. These are the GOES-R series, first launched in 2016.

The current series of GOES provides advanced imagery and atmospheric measurements, real-time mapping of lightning activity, and monitoring of space weather. This is the Western Hemisphere’s most sophisticated weather-observing and environmental-monitoring system.

The procurement, design, and manufacture of GOES satellites is overseen by NASA, while NOAA is the official provider of both GOES terrestrial and space weather data. The most recent GOES satellite was launched June 25, 2024 and is currently undergoing post-launch check out. NOAA expects to see the first images from the new GOES-19 in September.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: History

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Is our rainy summer finally drying out a bit?

Posted on August 19, 2024 by WeatherGuys Editor

Readers may recall we reported on the unusually wet nature of our late spring/ early summer about a month ago. At that time, Madison had recorded the wettest May 1-July 15 period since at least 1939 while averaging more than 2.5 degrees Fahrenheit above normal for that same period.

Another month has ticked away in this summer, and it has been a bit different than the ones that came before it. Through Aug. 15, Madison has recorded 1.73 inches of precipitation, which is 0.35 below normal. Ten of the first 15 days of the month had no precipitation at all and, from Aug. 7 to Aug. 13 we had a streak of seven straight days with no rain at all. That is now the longest dry streak since May 1.

One last update for the current month is that we have averaged 0.8 degrees Fahrenheit below normal for the first 15 days.

So, both the coolness and the dryness have been very different thus far in the new month.

Despite this recent lack of precipitation recently, we will still have the wettest May 1 to Aug. 15 ever recorded in Madison. To top it off, if we were to receive more than 4.63 inches of rain between now and September 1, we would surpass the all time record for wettest May 1 through September 1, 29.09 inches, set in 2018. That would require an average of nearly 0.29 inches each day until then — not likely since this time of the year averages less than half that amount.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Uncategorized

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