Convective Atmosphere Group

Category: Uncategorized (Page 1 of 6)

Chilly November (2022)

Yep, November was reasonably cool in the Sacramento area.  This was felt mostly in the lows.  The median low temperature for the month was 39F while the normal median is 45F.  The median high temperature was 1 degree below the normal median of 65F.   Below are the distributions of November 2022 lows and highs.  Despite the cool weather, we never even came close to setting a record low in Sacramento*, but it is quite possible that the high temperature on the 8th of just 53F was at least within sight of the record-low high-temperature for the day.

*The official low this morning in Davis of 30F would tie the official low in Sacramento for this date.  The low at Travis AFB was 26F!

Statistics of Sacramento Temperature Statistics

So, I want to talk a little bit about Sacramento temperature climatology.  This first figure below is what you might expect to see when thinking about temperature statistics: “normal” lows and highs; and “record” lows and highs.  These will feel familiar to anyone who lives in the Central Valley.  We have mild winters with little diurnal range and rather warm record lows.  We have what you might consider a long spring with slowly increasing normal highs and lows.  We have a very hot summer followed by quickly cooling normal and record temperatures in fall.  What I’m showing below is actually the 10-day running mean of temperatures.  This helps smooth out all the bumps and wiggles in the data.

But, what I really want to talk about is the variance of the normal and record temperatures.  Below, I’ve included a figure with 4 panels.  The first is the 10-day running variance (or variability) of the normal temperatures.  Since normals are locally monotonic (in time), this panel shows us how quickly the normal high and low change.  As we might have inferred from above, normal highs vary at 10-day time scales more than normal lows and do so most strongly toward the end of the year.  Interestingly, the second panel (the 10-day variance of the records) doesn’t look at all like the first panel.  The variance in record high temperatures is wiggly but functionally constant across the year.  This is not what I expected.  I had imagined the record highs would vary strongly in the summer and weakly in the winter.  The variance of the record low peaks in the cold season and is near zero around day 225 (mid-August).

On the bottom row, I have plotted 1) the 10-day running mean of the year of the record high and low (gaps occur when the same record is set in multiple years) and 2) the 10-day variance of the year of records.  Here, we see an obvious global warming signal — much more recent mean years of high temperature records than low.  The average difference is 56 years!  That’s incredible.  Also noteworthy: the 10-day mean year of record high decreases throughout the year.  I have no idea what to make of that — Our winters are more record warm than our falls?  The 10-day variance of the year of records is also a bit surprising.  Here, we see peaks in record low occurrence year in the cold season.  It seems (from this figure and looking at the raw data) that in the winter, we’ve actually had lots of instances of contemporary record lows even if on average they primarily occurred prior to 1940.

September Rain

24 hour accumulation of precipitation to 7am on the 19th in Davis was about 1″.  Below is the record (for Sacramento, at least) daily rainfall values for the month of September.  A 1″ storm would easily be a top 10 daily accumulation.  So, this rain was in rare company but was hardly unprecedented.

Records for the 23rd, 24th, and 25th were all set in 1904.  Assuming that was just one storm, total rainfall from that single event was (at least) 3.50″!

The Unseen Things Are Scary

See the source image

The scariest things in life can be those that are imagined rather than seen.  Science, in a way, is the process of taking the seen and making it not-scary through understanding and explanation.  But, what of the unseen?  Too often in physical science we conflate the unseen with the impossible. Take the quotation below that I ran across today which, in effect, I have heard uttered many times from physical scientists:

“We didn’t think it was possible because we had never seen it before.” (quotation I have altered to anonymize)

This kind of reasoning frustrates me continually.  Science is fantastic at observing the physical world but simultaneously fantastically poor.  We can be lulled to sleep by our considerable skills.  In 2022, data pours in to scientists in deluges.  We have so much data that we don’t know what to do with it all.  Despite this, there are (at least) two reasons we might never have observed something possible.  1) Rare events happen rarely. 2) We might not be looking.  So, rather than being lulled to sleep by our data richness, I think we should consider the value in being rousted by our collective naivety.

The scientific enterprise is grounded by observations.  That grounding prevents people like me, who may otherwise be so inclined, from living in an imagined world.  But, having failed to observe something in the past is not the same thing as its being impossible or even, necessarily, uncommon.  Science requires us to be looking (and indeed it compels us to look) in order to test an idea.  A lack of observations should not preclude all attempts to consider that which is consistent with existing knowledge.

If it does, then Lisa Simpson has a Tiger-Repelling Rock to sell us all.  Unseen tigers are scary.

Fog Fall

It has been an incredibly foggy autumn here in Davis (and throughout much of the CA Central Valley).  I made a histogram of daily rainfall totals from the past 50 days of my Cocorahs gauge.  I’ve grouped totals into 0″ (clear, cloudy, or light fog), 0.01″-0.02″ (heavy fog), and >=0.03″ (rain).  So far this autumn, over half of our days have seen measurable precipitation but 60% of those days have been from fog-fall rather from rainfall.

Academic Year 20-21

That’s it.  As of this morning, grades have been submitted for the spring quarter.  It was a very strange year, and an especially strange quarter of ATM 111.  I’m looking forward to teaching full time in the classroom again in the fall.  Join me for ATM 250 to learn about clouds, wind, fronts, and all those weathery things we deem sub-synoptic.

The Passing of Hank Aaron

As any of my students will tell you, I am a life-long Atlanta Braves fan.  And as any Braves fan will tell you, the ultimate Brave was Hank Aaron.  Whether you think he is still the rightful homerun champion or not (he is), his records that impresses me the most are that he had 80 more RBI thank Babe Ruth (for the all-time lead) and an incredible 700 more Total Bases than Stan Musial (also for the all-time lead by over 10%!).  As a fan who watches a lot of games, it was also incredible to hear his stories in interviews of growing up and eventually playing professionally in the South.  He was a man who faced adversity but never let it stand in his way.  It’s a shame the team couldn’t give Aaron one last World Series in 2020.  It’s no longer Hammer Time.

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