Had a trace of rain yesterday, August 5th, in Catalina as a few drops fell just after 5 PM, and again just after 8 PM. If you weren’t outside or driving in the neighborhood, you wouldn’t have noticed.
I always felt recording a trace of rain was important, but the recording of traces is definitely human influenced: there are outstanding trace “reporters”, and those who aren’t so diligent. An example, discovered while looking at rainfall data for my hometown Los Angeles. For decades it seemed, Sam Miller, was the Weather Bureau (now NWS) “statistician” reporting to the newspapers the amount of rain or other climate data of interest from the Los Angeles official climate site, downtown. Sam NEVER missed a trace, whether it was a summertime sprinkle (sparse larger drops that fall rapidly) from mid-level clouds, or drizzle (fine, close together drops that almost float in the air) from low, maritime Stratus clouds prevalent in mornings in the Los Angeles basin during the spring and early summer. During Sam Miller’s regime, Los Angeles averaged about 20-25 traces a year. When Sam passed in the mid-1960s, he was replaced by an observer that was not so vigilant. The number of traces fell to just several a year!
At the time, being a little naive, I thought I had discovered an air pollution effect. It had been reported that smoke from cane fires in Australia had reduced rainfall from relatively shallow clouds. I thought maybe that the notorious Los Angeles smog had reached a level where it had turned off the Stratus drizzle machine (mid-level clouds would not be affected). I got excited, but it wasn’t long before reason set in and the “heterogeneity” in the data was found to be due to human influence.
Even today, I take pride in detecting “traces” of rain, recalling Sam Miller. A “trace” tells you, when you see it in the climate data, that rain was in the area. And especially here in the summertime, perhaps even heavy rain that missed gauges. So, while hoping for a “dump” from a promising cloud base almost directly overhead (first pic) I waited outside for many minutes so I could “detect” it first hand. A heavy shaft of rain was already drenching the west slopes of Samaniego Ridge.
I waited outside for the first sparse fall of giant drops the size of silver dollars, those big boys that fall through the updraft overhead first before the collapse and main rainshaft falls out. Didn’t happen. The shaft from the cloud base overhead developed that bit too late and all we got is a few, spares medium drops, more or less having been blown our way by the wind as the main shaft that eventually came down. Oh, well.
Evidence of those drops having fallen, in nearly 100 F temperatures, was soon gone. If I hadn’t been outside watching as this base developed overhead, I might have missed it, or at least when it fell. However, I do have a “trace detector”, our oldest car which is parked outside. That car is always aquiring a new layer of dust, and, at the same time, I clean the windows every day. With the inevitable dust, overnight “traces” of rain are NEVER missed! I deem myself therefore, the “Trace King.” I’ve noticed that many people do not park their cars outside for the purpose of detecting traces of rain, and so that’s why I EASILY surpass others trace reporting because so many night events are missed. Its great to be at the top, I have to say, to be good at something anyway, if nothing else. An example of the detection of a trace from an overnight event below (2nd photo) Note small mud balls where drops and mud congealed. What a great sight! Got me another “trace” for the records!
I hope now that many of you will now appreciate the meteorological importance of parking your car outside, 24/7, refreshing its surfaces each day for that new, possible trace, to help you be that bit better weather observer you always wanted to be. Soon, you could be the “Trace King” of your domain!