Near-Real Time NUCAPS Data via NOAA CLASS Subscription Service

SPoRT has been investigating options to obtain near-real time NUCAPS (NOAA Unique CrIS and ATMS Processing System) data to expand the ozone products to Suomi NPP retrievals.  The AIRS ozone products cover a Northwestern Hemisphere domain (Link to SPoRT AIRS products) and were specifically created for the National Centers (WPC and OPC) to aid interpretation of the Air Mass RGB for identifying and forecasting stratospheric intrusions that can lead to rapid cyclogenesis and hurricane-force wind events in the North Atlantic and North Pacific Oceans. The AIRS data are obtained from NASA Land Atmosphere Near-Real Time Capability for EOS (LANCE), rather than Direct Broadcast, so that the products can be created in hourly swaths that cover the OPC domain. Since the ozone products are created from polar-orbiting retrievals, forecasters are eager for better temporal and spatial resolution.  Use of retrievals from newer instruments such as Suomi-NPP CrIS/ATMS can provide additional overpasses to improve spatial and temporal resolution when paired with AIRS.

Suomi NPP data are available on the NOAA Comprehensive Large Array-Data Stewardship System (CLASS).  Typically data are obtained from CLASS by choosing options such as data type, domain, and time on the website and placing an order. Depending on the size of the order, it can take about an hour to 24 hours for your request to be processed and ready for download via ftp.  Manually placing an order is not an optimal approach for near-real time data processing and product development.

Recently SPoRT investigated the CLASS subscription service and has had success in obtaining NUCAPS data with a 2-3 hour latency. The CLASS subscription service is a valuable tool, comparable to NASA LANCE, for obtaining near-real time NUCAPS data. Others in the community who are interested in obtaining NUCAPS data with reduced latency and need a larger domain than what is available from Direct Broadcast should investigate the CLASS subscription service. Below is a outline of steps to set up a CLASS subscription for NUCAPS data.

First go to CLASS, create a user account and sign in. Click on “Subscriptions” in the left side menu. Choose your data product from the dropdown menu and click “Add New” to begin setting up the subscription details.  For NUCAPS choose S-NPP Data Exploitation Granule Data (NDE_L2)


Next, set up the search criteria for your subscription by choosing the domain either by making a box on the map or entering latitude and longitude values beside the map.  Click on the box next to “NUCAPS Environmental Data Records” and click on  “S-NPP”.  Click on “Delivery Options” to continue.


Last set up the delivery options.  Choose “yes” for a recurring schedule and set the start and end dates.  The start and end dates do not include the year, therefore you’ll need to modify the start and end date as the end of the year approaches.  Choose whether or not you want email notifications. I would initially choose “yes” so you can start to gauge how quickly your subscription is being processed from the time your data arrives in CLASS.  Note that you will get an email for every granule and sometimes the email notifications are delayed quite a bit after your data is ready.  The notifications are initially helpful as you first set-up your subscription. As a side note I did enjoy spamming myself with approximately 20-30 CLASS email notifications per hour when I first set up my subscription so I could see how it was working and could gauge the data latency.  Most important, choose how often you want to receive data in the dropdown list beside “Include delivery manifest”. I’ve chosen “Every 1 hour”, but depending on the product and your needs, you can choose any interval from 1-24 hours. Features such as the digital signature and checksum aren’t always necessary but you can decide if you need them by reading about them on the class help pages.  Now click “Save” to finish.


Once your subscription is set up, you can log in at any time to view, modify, or disable your subscription.  Just click on “Subscriptions” on the left side menu after you have logged in.

Once your data arrives in CLASS your order will be processed. Therefore the subscription service can provide automatic distribution of near-real time products as long as the data is arriving in CLASS near-real time. If the data is not pushed to CLASS near-real time by the product developer or NDE than the subscription service can’t be used for near-real time purposes (unless you don’t mind a 6-24 hour or longer latency).  Not all Suomi NPP products are pushed to CLASS in a real-real time capability. Thankfully NUCAPS is pushed to CLASS relatively quickly after it is processed and can be obtained via CLASS near-real time.  Your subscription will have a unique ID and your order will be available on the ftp site in a directory named with your username and subscription ID.  The data will also be available via a unique http site named with your username and subscription ID. Now your data is in one place and can be accessed via scripting and ftp without manually submitting an order on CLASS.

Latency of products getting to CLASS and figuring out how to order data without manually submitting an order on the website have been the largest deterrents for SPoRT using CLASS data for real-time product development.  Not all Suomi NPP data is immediately pushed to CLASS near-real time, however contacts at NESDIS have indicated that in the next 6-months or so, more Suomi NPP data will be pushed to CLASS in near-real time mode. Utilizing the CLASS subscription service opens up a new opportunity for SPoRT and the community to use NUCAPS data (and in the near future, other Suomi NPP data sets) from CLASS for product development.

More information on CLASS subscriptions can be found within the CLASS help pages.

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