Extreme Heat Data Pathfinder

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According to the United States Global Change Research Program, heat waves are occurring more frequently in major cities across the nation. Heat waves are periods of abnormally hot and/or humid weather, lasting a few days to weeks at a time. In the 1960s, major cities in the U.S. experienced, on average, about two heat waves per year. In the 2010s, that number rose to more than six heat waves per year. Not only are cities experiencing more extreme heat events, the seasons are also lasting longer, on average 47 days longer than in 1960. Even under different climate models and emission scenarios, results indicate that extreme heat events worsen.

Humidity is an important factor in heat index assessment. When the humidity is high, water does not evaporate as easily and so it becomes difficult for the body to cool off through sweating. The heat index incorporates both temperature and humidity and is used to determine public health warnings for areas experiencing heat waves. The public health impacts of heat waves include exhaustion or heat stroke, and even death. According to the Center for Disease Control, extreme heat results in about 600 deaths per year in the U.S, with the elderly, very young, outdoor workers, and people with mental illness and chronic diseases at higher risk.

In monitoring heat waves, it's important to access long-term data records to assess abnormalities from the norm. Using remote sensing data can be an asset in determining climate trends, as several satellite platforms have been acquiring data over many years. For example, the Terra satellite has been acquiring land surface temperature data since 2000. With consistent and continuous data coverage, reliable temperature and humidity anomalies can be assessed.

Urban heat islands play a role in extreme heat events. Cities tend to have higher temperatures than outlying more rural areas; this is due primarily with the differences in radiative and thermal properties of varying surfaces, especially impervious surfaces such as buildings, pavement, etc., as well as the spatial distribution of water, soils, vegetation, and manmade surfaces.

Please visit the Earthdata Forum, where you can interact with other users and NASA subject matter experts on a variety of Earth science research and applications topics.

Find the Data

Temperature Data

Temperature, both air and land surface, is useful for assessing changes in weather and climate patterns that are critical for monitoring and responding to extreme heat events.

Humidity Data

Humidity must be factored in when determining the heat index for an area. NASA provides remote sensing and modeled measurements of relative humidity.

Land Cover Data

Urban heat islands are caused by the albedo of surfaces and infrastructure, the amount of vegetative cover, large bodies of water, and anthropogenic heat, that being emitted by vehicles, industrial facilities, etc.

Weather Maps

Weather maps which can be used to produce a 240-hour/10-day forecast of parameters, such as precipitation, humidity, wind speed, and temperature.

Socioeconomic Data

Heat-related deaths are preventable, but prevention requires a knowledge of where vulnerable populations exist and what interventions are needed in those communities.

Tools for Data Access and Visualization

Earthdata Search | Panoply | Giovanni | Worldview | AppEEARS | MODIS/VIIRS Subsetting Tools Suite

Earthdata Search

Earthdata Search is a tool for data discovery of Earth Observation data collections from NASA's Earth Observing System Data and Information System (EOSDIS), as well as U.S and international agencies across the Earth science disciplines. Users (including those without specific knowledge of the data) can search for and read about data collections, search for data files by date and spatial area, preview browse images, and download or submit requests for data files, with customization for select data collections.

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In the project area, for some datasets, you can customize your granule. You can reformat the data and output as HDF, NetCDF, ASCII, KML, or GeoTIFF format. You can also choose from a variety of projection options. Lastly, you can subset the data, obtaining only the bands that are needed.

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Panoply

Files in HDF and NetCDF format can be viewed in Panoply, a cross-platform application that plots geo-referenced and other arrays. Panoply offers additional functionality, such as slicing and plotting arrays, combining arrays, and exporting plots and animations.

• Panoply Orientation on NASA's Earthdata YouTube channel
• Tutorial on Creating Plots in Panoply

Giovanni

Giovanni is an online environment for the display and analysis of geophysical parameters. There are many options for analysis. The following are the more popular ones.

• Time-averaged maps are a simple way to observe the variability of data values over a region of interest.
• Map animations are a means to observe spatial patterns and detect unusual events over time.
• Area-averaged time series are used to display the value of a data variable that has been averaged from all the data values acquired for a selected region for each time step.
• Histogram plots are used to display the distribution of values of a data variable in a selected region and time interval.

For more detailed tutorials:

• Giovanni How-To's on GES DISC's YouTube channel.
• Data recipe for downloading a Giovanni map in NetCDF format and converting its data to quantifiable map data in the form of latitude-longitude-data value ASCII text.

Worldview

NASA's EOSDIS Worldview visualization application provides the capability to interactively browse over 1,000 global, full-resolution satellite imagery layers and then download the underlying data. Many of the available imagery layers are updated within three hours of observation, essentially showing the entire Earth as it looks "right now." This supports time-critical application areas such as wildfire management, air quality measurements, and flood monitoring. Imagery in Worldview is provided by NASA's Global Imagery Browse Services (GIBS). Worldview now includes nine geostationary imagery layers from GOES-East, GOES-West and Himawari-8 available at ten minute increments for the last 30 days. These layers include Red Visible, which can be used for analyzing daytime clouds, fog, insolation, and winds; Clean Infrared, which provides cloud top temperature and information about precipitation; and Air Mass RGB, which enables the visualization of the differentiation between air mass types (e.g., dry air, moist air, etc.). These full disk hemispheric views allow for almost real-time viewing of changes occurring around most of the world.

AppEEARS

AppEEARS, from LP DAAC, offers a simple and efficient way to access and transform geospatial data from a variety of federal data archives. AppEEARS enables users to subset geospatial datasets using spatial, temporal, and band/layer parameters. Two types of sample requests are available: point samples for geographic coordinates and area samples for spatial areas via vector polygons.

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Performing Area Extractions

After choosing to request an area extraction, you will be taken to the Extract Area Sample page where you will specify a series of parameters that are used to extract data for your area(s) of interest.

Spatial Subsetting

Define your region of interest in one of these three ways:

• Upload a vector polygon file in shapefile format (you can upload a single file with multiple features or multipart single features). Files in .shp, .shx, .dbf, or .prj format must be zipped into a file folder to upload.
• Upload a vector polygon file in GeoJSON format (can upload a single file with multiple features or multipart single features).
• Draw a polygon on the map by clicking on the Bounding box or Polygon icons (single feature only).

Select the date range for your time period of interest.

Specify the range of dates for which you wish to extract data by entering a start and end date (MM-DD-YYYY) or by clicking on the Calendar icon and selecting dates a start and end date in the calendar.

Adding Data Layers

Enter the product short name (e.g., MOD09A1, ECO3ETPTJPL), keywords from the product long name, a spatial resolution, a temporal extent, or a temporal resolution into the search bar. A list of available products matching your query will be generated. Select the layer(s) of interest to add to the Selected layers list. Layers from multiple products can be added to a single request. Be sure to read the list of available products available through AppEEARS.

Selecting Output Options

Two output file formats are available:

• GeoTIFF
• NetCDF4

If GeoTIFF is selected, one GeoTIFF will be created for each feature in the input vector polygon file for each layer by observation. If NetCDF4 is selected, outputs will be grouped into files in .nc format by product and by feature.

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Interacting with Results

Once your request is completed, from the Explore Requests page, click the View icon in order to view and interact with your results. This will take you to the View Area Sample page.

The Layer Stats plot provides time series boxplots for all of the sample data for a given feature, data layer, and observation. Each input feature is renamed with a unique AppEEARS ID (AID). If your feature contains attribute table information, you can view the feature attribute table data by clicking on the Information icon to the right of the Feature dropdown. To view statistics from different features or layers, select a different AID from the Feature dropdown and/or a different layer of interest from the Layer dropdown.

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Be sure to check out the AppEEARS documentation to learn more about downloading the output GeoTIFF or NetCDF4 files.

MODIS/VIIRS Subsetting Tools Suite

ORNL DAAC also has several MODIS and VIIRS Subset Tools for subsetting data.

• With the Global Subset Tool, you can request a subset for any location on earth, provided as GeoTIFF and in text format, including interactive time-series plots and more. Users specify a site by entering the site's geographic coordinates and the area surrounding that site, from one pixel up to 201 x 201 km. From the available datasets, you can specify a date and then select from MODIS Sinusoidal Projection or Geographic Lat/Long. You will need to register for an Earthdata Login to request data.
• With the Fixed Subsets Tool, you can download pre-processed subsets for 3000+ field and flux tower sites for validation of models and remote sensing products. The goal of the Fixed Sites Subsets Tool is to prepare summaries of selected data products for the community to characterize field sites. It includes sites from networks such as National Ecological Observatory Network, Forest Global Earth Observatory network, Phenology Camera network, and Long Term Ecological Research Network that are of relevance to the biodiversity community.
• With the Web Service, you can retrieve subset data (in real-time) for any location(s), time period, and area programmatically using a REST web service. Web service client and libraries are available in multiple programming languages, allowing integration of subsets into users' workflow.
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