High San Joaquin Valley January temps paint chilling air-pollution picture

It is already a week into the new year and since Jan. 1st, there is no single day in the San Joaquin Valley (Valley) air basin on the Valley floor itself completely devoid of an exceedance of particulate matter pollution 2.5 micrometers or smaller – also referred to as PM 2.5.

Looking at data (in micrograms per cubic meter of air) from the Clovis (C) and Fresno-Garland (F-G) monitoring sites in Fresno County, for example, here are the associated numbers:

  • Jan. 6, 2014 – 48 (C), 62 (F-G)
  • Jan. 5, 2014 – 61 (C), 71 (F-G)
  • Jan. 4, 2014 – 65 (C), 77 (F-G)
  • Jan. 3, 2014 – 70 (C), 82 (F-G)
  • Jan. 2, 2014 – 58 (C), 71 (F-G)
  • Jan. 1, 2014 – 65 (C), 98 (F-G)
  • Dec. 31, 2013 – 46 (C), 66 (F-G)
  • Dec. 30, 2013 – 49 (C), 65 (F-G)
  • Dec. 29, 2013 – 61 (C), 70 (F-G)

The threshold established for the San Joaquin Valley is 35 micrograms per cubic meter of air.

Interestingly, the data from the remaining active Fresno County monitoring sites – Huron and Tranquility – is significantly different from the Clovis and Fresno-Garland monitoring sites.

Here is the respective Huron (H) and Tranquility (T) PM 2.5 air quality data:

  • Jan. 6, 2014 – 37 (H), 32 (T)
  • Jan. 5, 2014 – 31 (H), 23 (T)
  • Jan. 4, 2014 – 42 (H), 31 (T)
  • Jan. 3, 2014 – 44 (H), 30 (T)
  • Jan. 2, 2014 – 34 (H), 24 (T)
  • Jan. 1, 2014 – 37 (H), 28 (T)
  • Dec. 31, 2013 – 40 (H), 26 (T)
  • Dec. 30, 2013 – 21 (H), 18 (T)
  • Dec. 29, 2013 – 16 (H), 6 (T)

Whereas Clovis and Fresno-Garland are urban sites, Huron and Tranquility are more rural in nature.

The difference can probably best be attributed to the far higher concentration of wood-burning and motor vehicle activity in the urban-suburban sector compared to that which takes place in the outlying Fresno County areas. All during this time, incidentally, all wood-burning has been prohibited which suggests not everyone is following the rules. Something like 365 citations had been issued to violators.

640px-California's_Central_ValleyTo paint a clearer picture, for several weeks the regional air has either been in the “unhealthy for sensitive groups” or “unhealthy” (for everyone) ranges all due to a ridge of high pressure that has refused to budge. Not only has this stalled weather pattern resulted in above average temperatures for this time of year but a stagnant air condition too. And, what has been a persistent weather pattern seems intent on sticking around, at least, for now. Daytime highs have been in the 60s in many parts of the Valley.

Absent a low pressure, upper atmospheric disturbance such as wind or rain, I expect the pattern – and pollution – to continue.

Meanwhile, in the mid-west and upper mid-west plains regions what is called the “Polar Vortex” is mixing with the jet stream bringing frigid temperatures to that region of the country. By the weekend, according to one source, temperatures in the St. Louis, Missouri area may reach into the 50s.

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