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The eye of the storm captured on 25 August 2017. Credit: NASA/NOAA GOES Project

Mapping Hurricane Harvey.

As Houston’s residents return home to evaluate the damage caused by Hurricane Harvey, we look at the maps and satellite imagery that have been critical to the organisation of relief and recovery efforts.

A portrait of Harvey.

Pinpointing the eye of the storm.

Powerful thunderstorms were pinpointed at the centre of the storm when NASA’s Aqua satellite (an Earth Observation satellite) analysed Hurricane Harvey in infrared light on Friday 25 August. A thick bank of thunderstorms were also highlighted to the north.

The infrared data is collected by an Atmospheric Infrared Sounder, also known as an AIRS instrument that is carried aboard a satellite. Credit NASA JPL/Ed Olsen.

Sodden soil.

On Thursday 31 August, NASA’s Earth Observatory released a map of the soil conditions around south Texas on Sunday 27 August, which showed that the ground surrounding Houston was already quite wet, even before Harvey arrived. When soil is saturated, the likelihood of flooding increases, thus the pre-existing ground conditions contributed to the situation that unraveled in Texas.

Soil conditions in south Texas on 27 August 2017. The data for the map is collected by NASA’s Soil Moisture Active Passive satellite using a radiometer. NASA Earth Observatory image by Joshua Stevens, using soil moisture data courtesy of JPL and the SMAP science team.

Record-breaking rainfall.

So much rain fell in Texas, the National Weather Service had to update their weather chart to accurately map rainfall.

In Cedar Beyou, a total of 51.88 inches of rain was recorded on Tuesday 29 August. To put this into perspective, here’s a map of much time it takes in years for 50 inches of rain to fall, calculated with past precipitation data.

For people living in America, The New York Times has created an interactive data visualisation that can tell you how long it would take for 50 inches of rain to fall on your hometown.

Rescue and response.

As Harvey continued onwards towards Louisiana and beyond, NASA worked with its partners to provide support to the rescue and response services. In a press release dated 30 August, NASA outlined their efforts and demonstrated the important role held by satellites.

Mapping flooded areas.

At the forefront is the Earth Science Disasters Team who analyse satellite imagery and produce information that aids the decisions of those who are coordinating response efforts. For example, the team created flood proxy maps using high-resolution imagery of the Earth’s surface, which can be used to identify areas that are likely to be flooded.

Screenshot of the flood extent map created by the ARIA team at NASA-JPL/Caltech, derived from the ALOS-2 ScanSAR data acquired on 8/27/17 (~1:30PM Central Time) over Texas including Houston. Pixels in light blue indicate areas that are likely to be flooded. Read more here.

Predicting Harvey’s next move.

NASA’s Global Precipitation Measurement (GPM) mission team produced graphics that examined Harvey’s structure during various stages of its development and landfall. These graphics were shared with NOAA’s National Hurricane Center via NASA’s Short-term Prediction Research and Transition (SPoRT) Center and the Naval Research Laboratory, to improve short-term forecasts on a regional scale.

Hurricane Harvey at 11.45 UTC and 21:25 UTC on 27 August. The images in this video are of rain rates derived from GPM’s GMI microwave imager (outer swath) and dual-frequency precipitation radar or DPR (inner swath) overlaid on enhanced infrared data from the GOES-East satellite. Credit: NASA Scientific Visualization Studio.

Assessing the aftermath.

Gauging the agricultural impacts of Hurricane Harvey is NASA’s Land Information System (LIS), a software framework that can integrate satellite imagery and advanced modelling techniques to produce detailed maps such as this one of relative soil moisture. Data such as these informs recovery planning.

Maps make data more useable and useful.

When important decisions have to be made quickly, maps and visualisations make data easier to share and digest. Satellite imagery enables us to monitor Earth on a large spatial scale, but data visualisation is the key to making that data useable.

However, neither the satellite imagery nor the data visualisations in this blog reflect the human impact of Hurricane Harvey. We must not forget that beneath the colourful maps and record-breaking statistics, there are people who have lost their homes and loved ones. Our thoughts are with all of those affected by current flooding events, both in America and Asia.

The story does not end here: check for updates on NASA’s own website or on Twitter @NASAEarth.



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