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.

Use better products!
The IEM Reanalysis is nothing special. It was cool maybe 15 years ago, but now days there are superior products available. Use those instead!

• 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.
  Having said that, here are some alternatives:
  ERA5Land
  DayMet
  GridMet
  PRISM

Product Changes

• 4 Jan 2023: Near realtime solar radiation is sourced from the HRRR model. For dates prior to 8 days ago, it is sourced from ERA5Land. This is a change as it used to be sourced from MERRAv2. It will take a number of days to update the archive to use this new source.
• 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

Hourly Data Sources

Yearly netcdf files since 1950, with updates at about 10 after the hour. Since we want real-time data, some of these model sources are not available immediately, so the denoted intermediate source fills the gap until the final source is available.

Daily Data Sources

Yearly netcdf files since 1893. Some of these variables are directly sourced from the hourly grids above. The concept of a daily variable is a bit nebulous, but is intended to be a 6 to 6 UTC period.

Data Access

Here are some JSON web services you may try.

MultiDay Request
================
Form: https://mesonet.agron.iastate.edu/iemre/multiday/{YYYY-MM-DD::date1}/{YYYY-MM-DD::date2}/{LAT}/{LON}/json
Example: https://mesonet.agron.iastate.edu/iemre/multiday/2010-05-01/2010-09-30/42.54/-96.40/json

Single Day Request
=======++=========
Form: https://mesonet.agron.iastate.edu/iemre/daily/{YYYY-MM-DD}/{LAT}/{LON}/json
Example: https://mesonet.agron.iastate.edu/iemre/daily/2010-05-01/42.54/-96.40/json

Single Day's Hourly (CDT/CST) Request
=======++=========
Form: https://mesonet.agron.iastate.edu/iemre/hourly/{YYYY-MM-DD}/{LAT}/{LON}/json
Example: https://mesonet.agron.iastate.edu/iemre/hourly/2010-05-01/42.54/-96.40/json

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:

• IEMRE Files
• ERA5Land Hourly Netcdf Files
• MRMS CST Daily Netcdf Files
• NCEP Stage IV Hourly Data
• Oregon State PRISM Daily Data