Increased CPM with rain and humidity.

 
Three charts with data for the last 7 Days, Two different locations. 'juzzie' - SBM-19, 'espminid2' - 2x SI-180g, both outdoors, And 'espminid1' - SBT-10a, inside my tool trailer 30m away.
See the spike that was produced during last night's heavy rain.

I recall discussions on this phenomenon some years ago on Netc.com.  Rain washout of Radon and progeny from the sky is often seen on some outdoor detectors.  It would depend on local soil properties and perhaps a low pressure weather cell drawing more air up before the rain.  Here are 2 articles describing it in more detail: Weblog article , Research Journal article .

Yes Bert490, Radon daughters are most probably is the culprit. Also associated with the washout is 7Be, which is a key reason why a swab sample from a collection surface (say, the roof of a shed) giving off persistently high counts weeks after collection.

Data points 313-465 recorded 2 weeks after this swab was collected, and 465 onwards is the swab before collection (placed there in the chart for comparison).
I actually sent a swab like this one to a friend with a gamma scintillator some time ago for testing and the results confirmed the theory
 

There is a case study is on the subject here - https://pubmed.ncbi.nlm.nih.gov/15511568/
And an explanation below

Simomax wrote:

I like your graphs Juzzie. Especially in your first post. They look good. What do you use to generate them? 


 

I have all my data going into an influxdb database on a Raspberry Pi 4B, and use Grafana for my visualizations. It is very easy to set up using DietPi OS, and super easy to use.
The data for the decay chart was created using an LND-7317 with GK-B5 counter and visualization created with LibreCalc.