Since 2008, the USDA’s National Agricultural Statistics Service, or NASS, has drawn on Landsat data to monitor dozens of crops in the lower 48 states as part of NASS’s Cropland Data Layer program. The Cropland Data layer uses Landsat and similar sensors to identify what crop is growing where in the country. Separately, NASS uses NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard the Aqua and Terra satellites to monitor daily vegetation health and growth stage, all indicators of crop yield.
Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth’s atmosphere (the ozone layer), and a much larger springtime decrease in stratospheric ozone around Earth’s polar regions. The latter phenomenon is referred to as the ozone hole. There are also springtime polar tropospheric ozone depletion events in addition to these stratospheric events. In 2019, NASA announced the “ozone hole” was the smallest ever since it was first discovered in 1982.
The main cause of ozone depletion and the ozone hole is manufactured chemicals, especially manufactured halocarbon refrigerants, solvents, propellants and foam-blowing agents (chlorofluorocarbons (CFCs), HCFCs, halons), referred to as ozone-depleting substances (ODS). These compounds are transported into the stratosphere by turbulent mixing after being emitted from the surface, mixing much faster than the molecules can settle. Once in the stratosphere, they release halogen atoms through photodissociation, which catalyze the breakdown of ozone (O3) into oxygen (O2). Both types of ozone depletion were observed to increase as emissions of halocarbons increased.
Ozone depletion and the ozone hole have generated worldwide concern over increased cancer risks and other negative effects. The ozone layer prevents most harmful UV wavelengths of ultraviolet light (UV light) from passing through the Earth’s atmosphere. These wavelengths cause skin cancer, sunburn and cataracts, which were projected to increase dramatically as a result of thinning ozone, as well as harming plants and animals. These concerns led to the adoption of the Montreal Protocol in 1987, which bans the production of CFCs, halons and other ozone-depleting chemicals.
The ban came into effect in 1989. Ozone levels stabilized by the mid-1990s and began to recover in the 2000s. Recovery is projected to continue over the next century, and the ozone hole is expected to reach pre-1980 levels by around 2075. The Montreal Protocol is considered the most successful international environmental agreement to date.
In April, instruments aboard NASA’s Operation IceBridge airborne campaign and the Ice, Cloud and Land Elevation Satellite-2 succeeded in measuring the same Arctic sea ice at the same time, a tricky feat given the shifting sea ice. Scientists have now analyzed airborne and spaceborne height measurements, and found that the two datasets match almost exactly, demonstrating how precisely ICESat-2 can measure the heights of the sea ice’s bumpy, cracked surface.
Arctic sea ice likely reached its 2019 minimum extent of 1.60 million square miles (4.15 million square kilometers) on Sept. 18, tied for second lowest summertime extent in the satellite record, according to NASA and the National Snow and Ice Data Center.
The Arctic sea ice cap is an expanse of frozen seawater floating on top of the Arctic Ocean and neighboring seas. Every year, it expands and thickens during the fall and winter and grows smaller and thinner during the spring and summer. But in the past decades, increasing temperatures have caused marked decreases in the Arctic sea ice extents in all seasons, with particularly rapid reductions in the minimum end-of-summer ice extent. The shrinking of the Arctic sea ice cover can ultimately affect local ecosystems, global weather patterns, and the circulation of the oceans.
Video Credit: NASA Goddard/Lead Producer: Katie Jepson (USRA); Technical Support: Aaron E. Lepsch (ADNET); Scientists: Nathan T. Kurtz (NASA/GSFC), Walt Meier (NASA/GSFC); Lead Visualizers: Trent L. Schindler (USRA), Cindy Starr (GST); Lead Animator: Bailee DesRocher (USRA); Narrator: LK Ward (USRA); Visualizer: Lori Perkins (NASA/GSFC); Lead Writer: Maria-Jose Vinas Garcia (Telophase); Videographers: Kate Ramsayer (Telophase), Jefferson Beck (USRA), John Caldwell (AIMM)
High temperatures and low humidity are two essential factors behind the rise in fire risk and activity, affecting fire behavior from its ignition to its spread. Even before a fire starts they set the stage, said Jim Randerson, an Earth system scientist at the University of California, Irvine who studies fires both in the field and with satellite data.
He and his colleagues studied the abundance of lightning strikes in the 2015 Alaskan fire season that burned a record 5.1 million acres. Lightning strikes are the main natural cause of fires. The researchers found an unusually high number of lightning strikes occurred, generated by the warmer temperatures that cause the atmosphere to create more convective systems — thunderstorms — which ultimately contributed to more burned area that year.
Hurricane Dorian is a strong tropical cyclone currently affecting the Bahamas and the Southeastern United States. The fourth named storm, second hurricane, and first major hurricane of the 2019 Atlantic hurricane season, Dorian developed from a tropical wave on August 24 in the Central Atlantic. The system gradually intensified while moving toward the Lesser Antilles, before becoming a hurricane on August 28. Rapid intensification ensued, and on August 31, Dorian intensified into a Category 4 major hurricane. On the following day, Dorian reached Category 5 intensity, peaking with one-minute sustained winds of 185 mph (295 km/h) and a minimum central pressure of 910 millibars (26.87 inHg) while making landfall in Elbow Cay, Bahamas, at 16:40 UTC. Dorian made another landfall on Grand Bahama several hours later, near the same intensity.
From August 26–28, the storm affected Caribbean nations and territories devastated by hurricanes Irma and Maria in 2017. Extensive precautionary measures were taken to mitigate damage, especially in Puerto Rico, where one person died. Damaging winds primarily affected the Virgin Islands where gusts reached 111 mph (179 km/h). Elsewhere in the Lesser Antilles, impacts from the storm were relatively minor.
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