Weather Flashback

June 2021 - Summertime Blue (July 20, 2017)


I captured this Oklahoma, summertime scene at Will Rogers World Airport on my way home from a morning shift at UPS. Although Oklahoma is known for its thunderstorm activity, especially come spring and early summer: deep blue skies, breeziness and warmth in Oklahoma should be noted as being a "normal" climatological occurrence here in summer. On this morning, a deep area of high-pressure aloft was parked over the southern Plains region. The relative humidity aloft was quite low due to descent. Descent which warmed the air (adiabatically) and prevented more humid air below from mixing higher aloft; hence, there was little if any mid or high -level cloudiness in this scene. Near the surface, low-pressure was located to the west over the southern Rockies and desert Southwest; and high-pressure was located near the surface to the east over southern Appalachia and the Deep South. This surface pressure pattern is common during the summer over the southern half of the conterminous Unites States; the pressure pattern generates lower atmospheric winds with a large southerly component across the southern Plains region. The lack of haze in this scene is not uncommon for Oklahoma in summer. The lack of haze, in this case, is a function of parcels near the surface having had a recent contact with the Gulf of Mexico. This pure tropical air near the surface contrasts with parcels that originate over the continent farther east, for example; where winds near the surface are lighter and there is more human activity to pollute the air (haze may still occur for other reasons, however)[1]. I found the "Clean Energy" (natural-gas) station in this scene rather ironic as it is an indicator of a transition to use cleaner-burning fuels. Cleaning-burning fuels in a part of America where energy-production drives a large fraction of the state's economy, politics and culture; despite impacts from petrochemical emissions being quite low here because winds are stronger and there are fewer people to pollute the air. One might also note the yellowish grass in the scene: an indicator of Oklahoma's mid and late summer dryness relative to spring and early summer. This dryness also contributes to warmth across the region, in addition to the aforementioned factors like lack of clouds and haze. This is because yellowish grass indicates less plant moisture. Moisture that would otherwise cool the air through evaporation.

Plate 1. Summertime Blue. Captured on July 20, 2017 at 8:01am CDT. Looking south from 35.41°, -97.60°.

  1. See "Haze Over the Central and Eastern United States" (Corfidi 1996, ed. 2013): here.