ESRL Quarterly Newsletter - Fall 2009

Tracking the Sun

NOAA site serves scientists, photographers, deep-sea fishers

A redesigned web site that lets users calculate the Sun’s precise position, including the times of sunrise and sunset, has captured the interest of thousands of web surfers since early July.

The NOAA Solar Calculator is now one of ESRL’s most popular web pages, surpassed regularly only by ESRL’s home page, trends in carbon cycle and greenhouse gases, and the ever-popular South Pole live camera.

Chris Cornwall calibrating instrument.

Chris Cornwall demonstrates how to align an instrument with the shadow of a plumb bob at solar noon Sept. 4, on the roof of the David Skaggs Research Center. Photo by Will von Dauster, NOAA.

ESRL’s Chris Cornwall redesigned his group’s solar calculator this summer, to improve upon a page that has proved far more popular than he imagined. Originally intended to help ESRL researchers install solar radiation instruments in the field, the solar calculator now serves amateur photographers around the world, green architects, robot engineers, and even movie makers.

Cornwall is the information technology manager of ESRL’s Global Monitoring Division, and his work during the last 12 years has included helping to set up and maintain the group’s network of surface radiation monitors. Radiation monitors gather critical on-the-ground information about Earth’s energy budget and climate. Such instruments can’t capture accurate data unless installed precisely in a north-south direction, Cornwall said. In the field, that can mean aligning instrumentation along the shadow of a plumb bob at exactly solar noon.

“And we miss solar noon a lot,” Cornwall said. “You can have a nice clear morning, and suddenly at solar noon you get a cloud. You can’t align an instrument without a shadow. Then we need to figure out when the Sun will be exactly 5° off solar noon…”

Screen image of solar calculator.

Solar Calculator output. If a photographer wants to capture a picture of the Washington Monument framed by the sunset next Fourth of July, NOAA’s Solar Calculator can help pick a spot. In the screenshot above, the red line (sunset) intersects the base of the Monument when a viewer is positioned to the southeast.

Cornwall, Chris Lehman, and Aaron Horiuchi created the original NOAA Solar Calculator site for colleagues 10 years ago, opening it up to public use about a year later. The emails have been rolling in since then, from unexpected users:

  • A Canadian defense researcher working on navigation by autonomous robots
  • An ecologist studying how albacore tuna behavior changes by day and night
  • A fire department manager scheduling annual training
  • A movie maker who needed to line up and time a sunset shot
  • A green architect designing a passive solar building
  • A small business owner who ran deep-sea fishing trips and wanted sunrise times

In July, Cornwall improved the Solar Calculator substantially, taking into account user suggestions. He included a feature to let users pinpoint their location on Google’s familiar map interface—something made possible by NOAA’s 2007 licensing of Google Earth and Google Maps API. And the visitors arrived, more than 6,000 in August alone.

NOAA researchers still rely on the site to set up sensitive instruments, Cornwall said, and public users have come to depend on it, too.

“Hey you guys, don’t you *dare* take down this page,” an elementary school teacher wrote him recently. “You gotta keep it working nicely!”

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