The Climodat section of the IEM website has been around since the beginning and dates further back than that. It generates a series of simple ASCII text reports that address commonly asked questions of long term daily data.
The input dataset used for these reports has been curated over many decades by climatologists here at ISU. Generally, this dataset only covered locations in Iowa. Over the years, the IEM expanded this dataset to cover the upper Midwestern US and now it covers the Continental US. Please note that there no longer is any manual data quality control done by ISU climatologists on this dataset. Previously, the Iowa data would go through a delayed quality control process by the State of Iowa Climatologist.
The realtime daily data closely tracks the NWS Cooperative Observer (COOP) network and Automated Surface Observation Station (ASOS) sites. This dataset should closely resemble datasets made available by the National Centers for Environmental Information (NCEI) and by NOAA's Regional Climate Centers (see ACIS).
In general, the IEM does not attempt to generate redundant datasets made available elsewhere. The most obvious redundancy here is to what is found within ACIS. Here's a current list of why this dataset continues to be redundantly generated here:
- Solar Radiation is an often requested dataset and while the NWS COOP nor ASOS network observe this variable, the IEM does processing to have model estimated solar radiation data tag along and made available for download. It is an useful value-add.
- The climodat work done by the IEM dates back to the beginning of the IEM and even before that, the recent services from NCEI and ACIS are relatively new. It would be nice to see some more products and rough edges taken out of upstream services before redirecting folks there.
- A lot of IEM infrastructure relies on this dataset. While a straight usage of ACIS would be possible, we would need to still have code in place to handle any ACIS outages or missing data. The IEM climodat dataset always contains at least 'daily' high and low temperature along with precipitation. Observations are prioritized, but estimates are done when necessary.
- The IEM has a very extensive ingest of NWS COOP data in SHEF format. With this data in house, it makes sense to continue curating the long term record.
Long term, the hope is to point folks upstream to NOAA when they want the data and reports, but in the interim, the IEM continues to effort removing variances between this dataset and other online sources. As always, feedback and comments are welcome.