IEM Reanalysis (IEMRE)

IEM Reanalysis is an effort to provide a regular dataset of Iowa Environmental Data without many of the problems associated with single site observations. The IEM will continue to provide single site observational data, but for some purposes, this dataset will be easier to work with. No dataset is perfect and this dataset is provided without warranty.

  • Why do this?
    Previously, the IEM has only provided raw observations with limited quality control checks in place. Quality control is hard! Many times, users are simply looking for something "close" and perhaps not as perfect as high quality sensor observations can be. Producing a gridded analysis is one way to produce a dataset from point observations which can be sampled as a means of spatial interpolation.
  • Isn't this a duplication of effort?
    While there are other "reanalysis" type projects out there with data freely available, many times their data does not update in near real-time and does not include many of the datasets the IEM uniquely collects. We may also produce an analysis on sub-hourly timescales.
    Having said that, here are some alternatives:

Product Changes

1 May 2018: Grid domain expanded to cover CONUS. It will take a while to fully populate the grids. At the moment, just the previous midwestern US data is available. Grid resolution increased to 0.125x0.125 degree.

Data Flow

1. Input Datasets

  • NCEP Stage IV Precipitation
    This is an hourly gridded product with precipitation estimates derived by RADAR and then bias corrected by gauge data. The IEM caches the grib data and makes hourly plots available here.
  • MRMS Precipitation
    Currently, this is only used to populate a daily total in a dedicated netcdf file.
  • ASOS/AWOS Daily Summaries
  • NWS Daily Climate Summaries
  • HRRR/MERRA/NARR Daily Solar Radiation
  • NWS COOPerative Observations
  • Manually QC'd Iowa COOP data from Iowa's State Climatologist
  • NCDC QC'd COOP Data

2. IEM ReAnalysis Gridded Datasets

3. Climodat Station Data

The location of the IEM Longterm tracked climate stations are used to sample from the IEMRE grid to produce daily values of high / low temperature, precipitation, snowfall, snow depth, and radiation. For some stations, a direct copy of the corresponding ASOS station data is used.

  • Climodat Reports
    These are pre-generated reports answering many of the commonly asked climatology questions.

Data Availability

Hourly IntervalDaily Interval
  • 2 Meter Air Temperature
  • 10 Meter Wind Speed and Direction
  • Precipitation
  • High and Low 2 Meter Air Temperature
  • Precipitation

Data Access

Here are some JSON web services you may try.

MultiDay Request
Single Day Request
Single Day's Hourly (CDT/CST) Request

Raw Data Access

The IEM makes extensive use of the NetCDF file format to store these gridded datasets. You can find individual web directories for various IEMRE related datasets: