For precipitation events, you can access NASA IMERG data on the NASA Giovanni website. For drought events you can access NASA SMAP data on the NASA Worldview website.
Precipitation (Rain/Snow)
IMERG - NASA Giovanni
NASA Giovanni (Geospatial Interactive Online Visualization and Analysis Infrastructure) is an online tool that allows users to visualize, analyze, and access a wide range of Earth science data without the need for downloading large datasets. It simplifies working with satellite data by offering tools for plotting, comparing, and averaging variables such as temperature, precipitation, and soil moisture across different regions and time periods.
You can access IMERG (Integrated Multi-satellite Retrievals for GPM) data on NASA Giovanni to visualize and analyze global precipitation patterns, as IMERG combines satellite and ground-based observations to provide high-resolution rainfall estimates every 30 minutes. To access longer time-periods of data, you may need to create a free account.
How to find storm data on NASA Giovanni
Open NASA Giovanni. If you want to access longer time-periods of data, you may need to create a free account.
Search "GPM_3IMERGHHL v07" in the keyword search bar.
Select "Multi-satellite precipitation estimate with climatological gauge calibration - Late Run (GPM_3IMERGHHL v07)" (not Random Error). This includes up-to-date data, likely including within the last 24 hours. If you're looking at an older storm, you might search "GPM_3IMERGHH v07" instead to get the "Final Run" version of IMERG which NASA recommends for general use, but generally runs 6 months behind.
At the top left of Giovanni, Select the Plot you want to generate. Pick 'Time Averaged Map' to see the average precipitation rate across your chosen location. Pick 'Map, Accumulated' to see the total amount of precipation that fell in your selected area during your selected timeframe. 'Animation' will allow you to see how the storm traveled over time. 'Time Series, Area Averaged' will show you a line graph that tracks how precipitation changes over time, making it easier to see when the storm was strongest and how long it lasted.
Select the Date Range you want to include. This could include the dates/times of a specific storm, or the last few days (or any dates you want to checkout!). Notice that the time zone is in UTC (Coordinated Universal Time) so if you're looking for specific times, you'll need to convert the local time to UTC (for example, you could Google search 6 PM EST to UTC). Keep in mind that the longer time series you choose, the longer Giovanni will take to plot.
Select the Region (Bounding Box or Shape). This is where (location) that you are going to pull data from. You can drag to select a rectangle on the map, type in latitude/longitude coordinates, or choose a preset shape (the relevant options are entire states or certain lakes/water bodies). Keep in mind that the larger the area you choose, the longer Giovanni will take to plot.
When you've selected all of your parameters, click the green "Plot Data" button at the bottom of the page.
After your selected plot loads, you can download the plot or data used to make the plot in a CSV file using the "Download" button. You can use CSV data in spreadsheet software (like Google Sheets or Microsoft Excel) to do further data analysis.
You will plot the IMERG variable "Multi-satellite precipitation estimate with climatological gauge calibration - Late Run half-hourly 0.1 deg. [GPM GPM_3IMERGHHL v07]" which is measured in mm/hour. Keep in mind that satellite data may appear to be less than ground measurements due to averaging across large areas. The U.S. Geological Survey (USGS) defines rainfall rate categories as:
Slight rain: Less than 0.5 mm per hour.
Moderate rain: Greater than 0.5 mm per hour, but less than 4.0 mm per hour.
Heavy rain: Greater than 4 mm per hour, but less than 8 mm per hour.
Very heavy rain: Greater than 8 mm per hour.
Heavy shower: Greater than 10 mm per hour, but less than 50 mm per hour.
Violent shower: Greater than 50 mm per hour.
You can find out what the typical precipitation amount is in a given month at your location using the NOAA Climate Normals tool.
How to Format and Analyze IMERG Data using Google Sheets (including Heat Maps)
NASA Worldview is an interactive online tool that allows users to explore and visualize satellite imagery and data layers in near real-time or for specific dates. It provides access to a variety of datasets, including soil moisture data from the SMAP (Soil Moisture Active Passive) mission, which measures moisture in the top layer of soil globally.
On the left side in the Layers tab, click the red "Add Layers" button and search for "Surface Soil Moisture 9 km". Select the first option (not the "Uncertainty" one). Exit the pop-up window.
Scroll down in the Base Layers section and hide the Corrected Reflectance layer by clicking the eye symbol.
Published SMAP data is usually a few months behind. Change the date at the bottom to a year ago to make sure your SMAP data is displaying. Then, you can select whatever dates you like to check out soil moisture data!
Note: If you'd like to download the SMAP data to CSV, click the Data tab in Worldview, select Surface Soil Moisture 9 km, optionally select the area of interest, and click "Download via EarthData Search". This will allow you to download H5 files (you may need to log in or create an account). We recommend just selecting one timestep (one file). You can use our H5 to CSV converter CoLab notebook in our Spreadsheet Resources page.