#projects-jvdh

abrupt vs. diffuse land cover transitions

cross-scale pattern comparisons #2

cross-scale pattern comparisons #1

mapping ghostly landscapes across three decades in Guatemala with archival aerial photography

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Residents of the northeast United States had their first glimpse of Hurricane Sandy as its spiraling winds crept to shore early last week. But long before landfall, scientists had been tracking Sandy’s approach with images provided by satellites circling our planet nearly every ninety minutes. Earth-observing satellites were critical in monitoring and predicting the storm’s path, timing, and intensity – information central to planning neighborhood evacuations that helped save many lives. Sandy was only the latest extreme event in which satellite observations have played a pivotal role. Two months ago, satellites documented the retreat of Arctic sea ice to its lowest-ever recorded extent and were silent witnesses as the first ship crossed the Arctic Ocean. When a blitzkrieg of wildfires ravaged over ten thousand square miles in the western U.S. last summer, satellites mapped the destruction in near real-time. In the same summer, satellites monitored thousands of Midwest farmlands devastated by the worst drought since the Dust Bowl. As the consequences of climate change are ever more undeniable, Earth-observing satellites are vital allies in understanding and preparing for our new reality. From a vantage point hundreds of miles overhead, satellites take thousands of pictures of forests, glaciers, lakes, clouds, and seas every day like an overzealous tourist. Earth-observing satellites do not see our world the same way we do, though. In most cases, people, cars, and even houses are too small to register in a satellite’s gaze. Satellites also typically record light that is imperceptible to our eyes, such as infrared light. Measuring the amount of reflected non-visible light is central to the operation of most satellites. Differences in reflected infrared light can, for example, expose slash-and-burn deforestation in the Amazon rainforest, a practice that emits carbon dioxide into our atmosphere, fueling climate change. It is perhaps unintuitive that distant tropical deforestation or glacial melt in Greenland could impact the tides on our shores. Yet this is exactly the case: our local environment is affected by global processes that, in turn, are influenced by distant environmental events. Satellite images help bridge the gap between local perceptions of environmental conditions and the global reality of climate change by illuminating many of the links in the climate chain. Satellite measurements of sea and land surface temperature, land cover, soil moisture, and atmospheric gas concentrations can be used to effectively estimate local sea level rise and potential for heat waves, drought, and storm severity. “Local” could be anywhere on Earth, as we are each indirectly or directly affected by climate change regardless of our geography. Satellite images also contextualize current impacts of climate change with a detailed record of our planetary past as seen from above. Nimbus 2, an early Earth-observing satellite, was launched by NASA in 1966 to monitor Earth processes on a global scale. Nearly forgotten for decades, Nimbus 2’s images of polar ice caps and measurements of sea surface temperature have recently been resurrected as historical benchmarks for today’s drastically different environment. The NASA/USGS Landsat program is exceptional in providing an archive for comparison having produced images of our planet’s surface every sixteen days since 1972 with enough detail to spot a baseball diamond. The environmental conditions contributing to Sandy’s record-breaking pressure and storm surge are now on record, and will provide essential information for future forecasting efforts. Highly detailed satellite images, much like those seen in Google Earth, are increasingly being used in humanitarian aid efforts after extreme events. In the days following the 2010 earthquake in Haiti, satellite images were used to delineate roadways where no reliable maps existed, helping to direct relief supplies. Satellite images identified communities affected by the 2011 Japanese tsunami, an especially crucial contribution in areas that rescue workers could not immediately reach. Information gleaned from satellite images is often integrated with crowdsourced Twitter posts or cell phone SMS messages to direct a highly localized response. By coupling distinct but complementary data, these initiatives provide a template for future disaster response efforts. Satellite images help us to better understand how the Earth functions despite the seemingly chaotic future that recent events herald. By holding up a mirror to a planet in terrific flux, satellites provide a perspective unrivaled on the ground and unparalleled in importance.

Constellation-like normalized difference vegetation (NDVI) images paired with false-color Near-Infrared - Red - Green images, all of which are derived from a May 2006 WorldView-2 image over West Bank.

Landsat ETM plussed to the max, showing Kauth-Thomas Brightness, Greenness, Wetness index values across northwest Yunnan, China.