Wednesday, April 23, 2014

Update - CoCoRaHS Observations and NOWData

There was a lot of interest, a number of questions via Facebook, and some confusion about the inclusion of CoCoRaHS data in the NWS NOWData product.  I'll try and clear up a few things in this post, and also point you to another web site where you can also look at CoCoRaHs observations.

The data that feeds the NOWData tool on the National Weather Service web sites come from the Applied Climate Information System (ACIS) developed and maintained by the Regional Climate Centers (RCCs). The daily data from the U.S. Cooperative Network and CoCoRaHS are fed into ACIS by the Global Historical Climate Network (GHCN) Daily database which is collected, compiled, and distributed by the National Climatic Data Center in Asheville, NC. Are you following all of this? Good.

A few people have asked why their station does not appear in NOWData. The GHCN database only contains the data for CoCoRaHS stations that have submitted at least 100 observations. New active stations are added to the GHCN database once a month, so depending on timing it could be four months before a new station appears in GHCN and thus in NOWData.

Remember, to see the CoCoRaHS stations on NowData you must choose View Map, and then at the bottom of the map select "Show more stations".  The only way to identify a station is to move your mouse over the CoCoRaHS symbol.  Click on the symbol to select that station. Note that CoCoRaHS stations are only identified by the station name, not the CoCoRaHS station number.

There is another source where you can view tables and charts of CoCoRaHS data.  The Midwestern Regional Climate Center's cli-MATE system has a number of ways to view CoCoRAHS data. (Full disclosure - I was Director of the MRCC for 13 years and still work there on a part-time basis).  You do have to register for an account, but it's free. Once you have an account you have access to climate data throughout the U.S., not just CoCoRaHS.

Once you have an account you have access to the data and charts. As an example we'll look at Station Data/Daily Between Two Dates and one of the Multi-Station Summaries. You can select a station either through a sequential menu or through a map interface. For this example we'll select CoCoRaHS station CO-LR-273, FCL 2.2 NW. Note that you can select the stations only by their names at this time. cli-MATE also access the GHCN data through ACIS, so the data availability rules apply here as well (100 observations).

After the station is selected, go to Station Data/Daily Data Between Two dates. Here you can select over what time period you wish to view data, and whether you want tabular output (similar to what is on the CoCoRaHS Station Precip Summary option), or a chart. This chart has precip, snow, and snow depth data plotted on it..

Chart showing precip, snow, and snow depth for CO-LR-273

Here is the chart with just precipitation. If you move your mouse pointer over a bar on the chart the data for that bar is displayed.

You can also display summaries of precipitation data by climate division.

Input screen for multi-station precip summary

Output for multi-station precip summary. This list was truncated for display - there are many more stations in the summary

 Another option allows you to display daily data for a particular county.

Input screen for county daily data

Output for county daily data.
This output can get rather large (several screen widths) if there are a large number of stations in a county.

CoCoRaHS data is really "out there" in the world of weather and climate data. CoCoRaHS is now the largest provider of daily precipitation observations in the United States.  These new tools allow more people to have access to the observations you make and report every day. Thanks to all of our dedicated observers!

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