This Week: Ancient water = ancient habitat?
In the News: Texas is dry and hot. Global warming?
Coming Thursday: Roaches: A lot smarter than you thought!
How long have satellites been used to study Earth’s weather? NASA image of Explorer VII satellite, 1964 The first successful meteorological experiment conducted from a satellite was launched on Explorer VII on October 13, 1959, just over 50 years ago. Explorer VII carried an instrument that measured Earth’s heat balance. The thermal radiation experiment was [...]
What is the jet stream? Photo: NOAA The jet stream is a narrow current of strong wind that blows through the upper regions of the troposphere, about seven miles above ground. The jet stream generally moves from west to east, but it can meander like a river. The winds can move up to 200 mph [...]
Numerical Weather Forecasting is younger than rock ‘n roll!! From NOAA Before 1960, the idea that a reasonably accurate two-day weather forecast could be made routinely was a pipe dream – now it’s a routine reality. In fact, it was not until just after World War I that a theory concerning the structure, life cycle [...]
How accurate are weather forecasts? Image: NOAA In general, weather forecasts are getting better, due to improvements in computer models, observations and our understanding of atmospheric. Accuracy depends on the purpose of the forecast and how far out it extends. Next-day forecasts of maximum temperature are good to within 3 or 4 degrees; however, the [...]
Is there a relationship between sun spots and climate? Since the invention of the telescope in the 1600s, observers have recorded variations in the numbers of dark spots – “sunspots” – on the Sun’s surface. These variations normally follow a regular cycle with peaks 11 years apart. This cycle coincides with a small oscillation in [...]
What do heating degree-days tell us? Each degree that the mean temperature is below 65 degrees F is one heating degree-day. So if today’s average temperature is 55 degrees F, the day accounts for 10 heating degree-days. Engineers determined that when the mean outdoor temperature drops below 65 degrees F, most buildings require heating to [...]
What is space weather? Space weather describes the conditions in space that affect Earth and its technological systems. Space weather storms originate from the sun and occur in space near Earth or in the atmosphere. Space weather, like weather here on Earth, is continually moving and changing. Space weather phenomena include the Northern lights and [...]
What is the dewpoint temperature? Dew on evergreens, by Michael Theberge at NOAA Think of a morning when you walked on a grass lawn or through a field. Did your shoes get wet? If yes, that is because the grass was wet with dew. The dewpoint temperature is the temperature to which the air must [...]
Crane moves radome into position during installation of radar antennae at NOAA’s National Severe Storms Laboratory in Norman, Oklahoma Photo from NOAA How does weather radar work? Radar, an acronym for RAdio Detection And Ranging, was invented during World War II to detect aircraft, but precipitation frequently got in the way. The military’s noise is [...]
Why are clouds white? Photograph of Cumulus clouds in fair weather taken by Michael Jastremsk Clouds are made of water and clean water is clear. So why are clouds white? Because clouds are made of billions of small water droplets and ice crystals. When light beams interact with particles suspended in air, some of the [...]
What does a 60 percent chance of precipitation mean? The probability of precipitation (fondly known as PoP) has been part of weather forecasts since the late 1960s, and is the only forecast element that includes a probability. Unfortunately, there is confusion about the exact meaning of a “60 percent chance of precipitation.” Part of that [...]
How does tornado season vary across the United States? Tornado season begins as early as late February or early March in northern Texas and Oklahoma, the southern portion of Tornado Alley, where the tornado threat remains through most of May. By early June, the greatest threats tend to lie to the north, in Kansas and [...]
What do weather conditions have to do with maple syrup harvesting? Original image from the New York Public Library Digital Gallery. Weather is a crucial factor for a good harvest of maple syrup. Tapping trees occurs in late winter and early spring. In Wisconsin, March is a prime month for tapping sugar maple trees as [...]
Can there be a sun-snowshower? Photo: Zaphod These cumulus clouds are not sunshower material. See a late spring sun-snow shower here! Almost all of us have noticed a summer rainshower that occurs while the sun is shining on us. In this event, known as a sun-shower, the raindrops fall from a type of cloud called [...]
Why is the sky blue? Half Dome (in California’s Yosemite National Park) under a bright blue sky. To understand why the sky is blue, we need to understand a little about light. Light is a form of electromagnetic energy, which can propagate through empty space. We describe this energy by wavelength – the distance between [...]