This document discusses how freely available weather and volcanic ash data from government agencies can be combined and visualized in near real-time using open web mapping services and tools. Specifically, it shows how data from NOAA and USGS on cloud cover, sulfur dioxide levels, and volcanic locations can be streamed and overlaid to track the dispersal of ash from the Eyjafjallajokull volcano in Iceland in 2010. Examples are given of viewing this "mash-up" of data on GIS Cloud and ArcGIS Explorer to monitor the movement of ash plumes and their impact on air travel.

1. Near real-time weather data and volcanic ash dispersal in the North Atlantic
Andrew Zolnai
Cambridge UK
blog.zolnai.ca
Abstract
Newly available internet technologies allow freely available government data mash-ups help track
weather patterns in real time. This allows for example to ascertain the weather risk across the north
Atlantic, and help track weather and flight disruptions associated with ongoing Icelandic volcanic
eruptions. Such developments will encourage citizen geographers to monitor their environment.
Introduction
The Eyjafjallajokull volcano is situated on the south coast of Iceland astride the mid-Atlantic oceanic
ridge. Its eruption has been spewing ash into the atmosphere more or less continuously since late
April 2010. It had a major impact on air traffic in the north Atlantic, affecting flights from North
America as well as those across northern Europe. The only respite is provided when the wind bears
ash away from the continent towards the uninhabited Arctic region.
It is therefore critical to be able to follow the dispersal of ash in near-real time, in order to try and
anticipate it impact in the near future. Whilst government meteorological offices have been
providing advisories and the news media followed its consequences, new tools allow the public to
follow this themselves. Here are simple tools available for free on the internet, as well as freely
accessible government data sources in order to do this.
Data Sources
US National Oceanic and Atmospheric Administration (NOAA) Goddard Space Flight Center (GSFC)
hosts web mapping services (WMS) of near-real time cloud cover data worldwide. They also carry
sulphur dioxide (SO2) and carbon monoxide (CO) readings, as reflective of ash dispersal hard to see
in the visible spectrum. These can be displayed for the current and up to six previous day in near real
time using WMS on a mapping system described in the next paragraph.
The US Geological Survey (USGS) also produced an Open File Report (OFR) that describe the plate
tectonic boundaries and the volcanoes along them. These are available in Keyhole Mark-up
Language (KML) and have been exported to a spreadsheet for correction (global data often posted
as east E and W longitude are more often read as positive and negative, respectively, and data
across the antemeridian or date line are often repeated or misread by software and data systems).
Tools
These data can be posted individually straight from source, either as NOAA WMS in any browser or
USGS KML in Google Earth. A web GIS service is used here to spatially register and correctly stack the
data together into what is called a mash-up. It is the combination of several datasets that provides
the power to link, track and even predict complex weather phenomena.

2. Vector web service
The service used is a free Geographic Information System (GIS) on the web called GIS Cloud posted
on www.giscloud.com. Data can be freely viewed anonymously, a free login can be created, and data
can be freely posted with certain terms and conditions (please review the website for details). The
mash-up can be found under Google Fusion > NOAA Cloud or directly under http://bit.ly/ansAbe.
Near-real time weather data are posted together with their origin, and freely usable under the
NOAA and USGS terms & conditions. Note that data posted here are original vectors and images.
Raster web service
The same data can be posted on ESRI’s free GIS viewer ArcGIS Explorer (AGX). The data file has been
posted on the new Arcgis.com repository http://bit.ly/bkdntd - double-clicking the icon will
download the NMF file and launch it in ArcMap or AGX desktop , whichever you have. Note that at
time of posting, ArcGIS Explorer online http://explorer.arcgis.com/ could not access this type of file.
Usage
The original screenshot of the ash cloud over England is posted on my blog http://bit.ly/ajU8IR
giscloud.com ArcGIS Explorer
SO2 readings clearly indicate where the as plume went early May 2010. The blog also show a video
created from snapshots of the cloud cover in the visible light spectrum, taken late May after the
second air traffic disruption – it is also posted on YouTube http://bit.ly/b4Iz85.
Conclusion
This shows how easy it can be to post weather and geographic data freely available from
government websites, by using free GIS software on the internet: Can’t you thus view, analyse and
post near-real time data relevant to your specific geography and to your particular sphere of
interest? We hope this will inspire you to become citizen geographers surveying your environment!
References
NOAA WMS, current: Goddard Earth Sciences Data and Information Services Center, Atmospheric
Infrared Sounder (AIRS) Near-Real-Time, http://disc.sci.gsfc.nasa.gov/services/ogc_wms
USGS, 2009: Open File Report 2009-1133, Preliminary Spreadsheet of Eruption Source Parameters
for Volcanoes of the World, http://pubs.usgs.gov/of/2009/1133/of2009-1133_text.pdf