If you were in the path of the total solar eclipse last week, you may have observed a change in your environment. The more sunlight that was blocked, the more dramatic the changes.
Skiers and hikers on Saddleback Mountain in Maine during the April 8 total solar eclipse. (Photo credit: R. Bukaty, Associated Press)
A range of surface and near-surface meteorological observations can occur during a total solar eclipse. If it was a cloud-free day, or mostly cloudy day, you probably felt a drop in temperature. As the moon crossed in front of sun, it cast a shadow blocking solar energy from reaching your location. While it may have lasted only a few minutes, the reduction in solar radiation would result in a drop in temperature. In some locations, the temperature dropped by as much as 10 degrees. As the sun reappeared, the temperature increased.
A drop in temperature would include a corresponding increase in the relative humidity. So, it might have felt more humid. You may have also observed a change in the wind speed.
The planetary boundary layer, also referred to as the atmospheric boundary layer, is the lowest part of our atmosphere. It is about 0.6 miles thick and is where the atmosphere exchanges energy directly with the ground. The exchanges are primarily mechanical (e.g. wind and turbulence) and thermal. The thermal contact between the boundary layer and the ground surface is a result of the amount of solar radiation.
You may have already observed, in the absence of a storm, that after sundown the wind calms. When the sun sets, the radiative cooling of the ground increases the stability of the lower atmosphere. This reduces the energy exchanges between the atmosphere and the surface. This can result in the wind dying down. The drop in temperature you experienced during the eclipse would similarly cool the ground.
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. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.
This new Plant Hardiness Zone Map was generated from the past three decades of data reflecting overall warming, especially in overnight lows. The data mostly comes from weather stations and reveals a general trend of warmer temperatures, as zones tending to be farther north in the 2023 map. (Image credit: USDA)
If you are involved with gardening, you probably are aware of the Plant Hardiness Zone Map, or PHZM, often listed on seed packets. The U.S. Department of Agriculture developed the zones and first published them in 1960. The USDA updated them in 2012 and more recently in November 2023.
A hardiness zone provides information on the type of plants capable of surviving certain climatic conditions. The designations are based on the “average annual extreme minimum temperature” at a given location during a particular 30-year period. The climate zones are determined from temperature records kept by National Atmospheric and Oceanic Administration.
Every 10 years NOAA computes a revised 30-year average temperature and extreme temperatures for the U.S. using climate observations collected at local weather stations across the country. The newest revision spans the 30-year period from 1991 to 2020. The influence of long-term global warming is reflected in the revised temperatures. The 30-year average minimum winter temperatures increased at nearly all locations in the continental U.S.
The revised PHZM reflects this climate change. Compared with the 2012 map, the 2023 designation shows that about half of the country shifted to the next warmer half zone, and the other half of the country remained in the same half zone. Previously, northwestern Wisconsin was in zones 4a and 3b; the revised map indicates the region to be zone 4a. The colder zone of 3b is no longer a designation in Wisconsin.
While the hardiness zones are very useful, they cannot account for all climate and weather conditions such as snowfall, which can insulate the plants during a cold winter, or severe summertime heat. In addition to knowing your plant hardiness zone, it is also very useful to talk with local master gardeners and nurseries as you plan your plantings 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. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.
The weather observing stations of the National Weather Service operate in fully automatic mode and have sensors that measure visibility.
National Weather Service (NWS) Automated Surface Observing System (ASOS). (Photo credit: NOAA/NWS)
These instruments sense the forward scattering characteristics of light to measure the extinction coefficient of a high intensity beam directed at a volume of air close to the sensor. This provides an accurate measurement over a range of visibilities. The use of light within the visible spectrum also allows the sensor to simulate human perception of visibility.
There are a smaller number of stations where there is still a human observer to estimate visibility (e.g. at airfields). When people make the measurements, they are estimating the maximum distance away that they can see an object located near or on the ground. The object should be identifiable against the background. If the visibility varies with direction, the lowest value is reported.
A person with 20/20 vision who is about 5 feet tall can see a horizontal distance of about 3 miles along a flat ground surface. The human eye is more sensitive and can see a greater distance, but 3 miles is the point at which Earth’s curvature bends away. The instrument observations employ physics and are not concerned with Earth’s curvature.
We are all interested in horizontal visibility as it has major implications for transportation. The measurement is made at weather stations since visibility is dependent on current weather.
Horizontal visibility near the ground is one of the observations plotted on a station model. It is measured in fractions of a mile, unless there is an obstruction due to current weather conditions, such as fog, rain or smoke. If the visibility is above 10 miles, the values are either omitted from the map or listed at 10 miles.
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. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.
Changes in the weather patterns that brought record-breaking warm temperatures to the Madison area this winter might also mean that a warmer-than-usual summer lies ahead.
Temperature Outlookfor June, July and August (Image credit: NOAA Climate Prediction Center)
There’s a fair chance that temperatures could rise above normal in June, July and August, and even into early fall, climate scientists say.
“Looking at the outlook for meteorological summer, the three-month period including June, July and August, the probabilities of above-normal temperatures are slightly greater than one-third, or between 33 and 40%,” said Dan Collins, lead climate scientist for the National Oceanic and Atmospheric Administration’s most recent Climate Prediction Center seasonal outlook.
“Later in the summer, the seasonal outlook increases the chance of above-normal temperatures to greater than 40% for the July, August and September period,” Collins said.
Just how high the mercury could rise, it’s not possible to say. Official predictions do not say what exactly “above normal” temperatures could mean, Collins said.
However, Madison’s recent wintertime high temperatures — some into the high 60s — are not directly linked to what’s to come this summer, said Steven Ackerman, emeritus professor for the Department of Atmospheric and Oceanic Sciences and the retired vice chancellor for research and graduate education at UW-Madison.
“This unusual winter we’ve been having is partially due to the El Niño (climate pattern) that we’ve had that’s been pretty strong,” Ackerman explained.
But NOAA recently declared this El Niño is breaking down, he said, “and that means in the summertime the outlook is for ‘neutral’ conditions.”
“Neutral” means that the El Niño year — when the tropical Pacific is warmer than normal — is transitioning to a La Niña year, “which is pretty much the opposite,” Ackerman said. In that “neutral” scenario, “Wisconsin is typically above average in regards to temperature, and pretty much near normal in regards to precipitation,” he said.
“What we typically see after an El Niño is both the minimum temperatures go up as well as the maximum temperatures. And what we’ve been seeing in general is the minimum temperatures seem to be warmer than the increase in the high temperatures during summertime,” Ackerman said. “All of this is sitting on top of a world that is warming.”
Daily high temperatures in Madison for the month of June from 1991 to 2020 ranged from 75 to 82 degrees Fahrenheit, according to the National Weather Service. Low temperatures in June during those same years ranged from 53 to 61 degrees, with steady increases through the month.
Daily normal highs in July from 1991 to 2020 were consistently at 82 degrees, and lows hovered around 61 or 62 degrees. Daily normal El Niño temperatures for August were similar during that time, though they dropped several degrees toward the end of the month.
Last summer, however, was a different story. As Ackerman and UW professor Jonathan Martin, co-authors of the “Ask the Weather Guys” column, which runs on Mondays in the Wisconsin State Journal, wrote in early January: “Our meteorological summer in 2023 was the fifth-driest summer on record (since 1895). An intense heat wave hit in August, peaking from Aug. 22 to Aug. 24. Temperatures reached more than 100 degrees in many areas across the state.”
Wildfire smoke from Canada in late June also was an extreme weather factor in 2023, causing many people to curb outdoor activities and forcing the cancellation of outdoor summer events for several days.
If temperatures do soar in the coming summer and residents crank up the window fans or air conditioning, Madison Gas and Electric is equipped to serve any increased needs for electricity, said MGE communications manager Steve Schultz.
“MGE has sufficient capacity to meet the energy needs of our customers this summer, even if demand is higher overall, and we prepare for all sorts of weather conditions,” he said.
“Utilities are required to have enough generation capacity to provide power to all customers when demand for power is at its peak, or highest. For example, on the hottest day of the year when everyone is running their air conditioners,” Schultz said. “In Wisconsin, utilities also are required to have a reserve capacity margin above what they need to serve all customers when demand is at its peak.”
Under current predictions, precipitation in the Madison area is expected to be close to normal this summer. In the month of June from 1991 to 2020, that meant 5.28 inches; in July and August during those same years, 4.51 inches and 4.16 inches respectively.
“I hope we get adequate precipitation at timely intervals,” said Ed Hopkins, assistant state climatologist at the UW-Madison department of Atmospheric and Oceanic Sciences.
“Not a deluge in one day and nothing for the next month. It would be wonderful to have 1 inch of rain a week here in the corn belt, for the development of crops.”
We are now past the end of the meteorological winter, which consists of the months of December, January and February.
NWS winter weather statistics for Madison Wisconsin
This season has been a remarkably mild one for most of its duration. With the exception of a week of desperate cold in mid-January, there was hardly any cold air to speak of in southern Wisconsin all winter. In fact, Madison was 9.5 degrees above normal for December, 3.5 degrees above normal for January (reduced because of the cold snap Jan. 14-21, during which the temperature was 14 degrees below normal!) and 11 degrees above normal for February.
All together this means we were 7.9 degrees above normal from Dec. 1 through Feb. 28. (We don’t count leap days.)
Over the wider region, this was the warmest winter in the past 132 years at a vast majority of locations throughout Wisconsin and Minnesota, and over northeast Iowa and most of northern Michigan.
As measured by the areal extent of air colder than minus 5 centigrade (23 Fahrenheit) at 850 millibars (about 1 mile above the surface), this was the third-warmest winter in the past 76 seasons, only slipping from second to third place on the last day of the tally, Feb. 28.
No matter how one looks at this winter — locally, regionally or hemispherically — it was one of the warmest in a century. Current guidance from the Climate Prediction Center suggests about a 50% chance of the unusual warmth persisting, though with some interruptions, through meteorological spring, March through May. We would not be surprised, however, to see at least a couple additional examples of winter before we finally see this mildest of winter seasons come to its end.
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. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.
