Mid-season climate diagnostics of jet contrail ëoutbreaksí and implications for eastern US sky‑cover trends

Abstract

The cirrus-level 'condensation trails' (contrails) produced by jet aircraft often occur as sub-regional-scale 'outbreaks' of multiple contrails, suggested as contributing to post ~1965 climate trends in parts of the US and Europe. Several previously-developed, satellite-image based contrail spatial inventories for the conterminous US (CONUS) revealed regional-scale differences in frequency. However, the use of such geographically-fixed regions was not ideal for climate studies. As a first step towards determining the potential climate impacts of contrail outbreaks for the CONUS, we develop maps of overlapping (in time, space) outbreak occurrences-'overlaps'by applying GIS to a recent period (2000-2002) satellite-image derived inventory for mid-season months. The higher-frequency outbreak overlap regions undergo substantial between-season variations in magnitude and extent that reflect an association with upper-tropospheric temperature gradients and winds. Overlap maps generated for additional mid-season months in 2008-2009 indicate the inter-annual variability of the outbreak regionalization. To clarify the role of uppertroposphere synoptic meteorological conditions in contrail outbreak occurrence, we form composites-multi-case averages-for the sub-region of maximum overlap frequency in each midseason month. Regional and seasonal variations in the relative roles of 'thermo-dynamic' (here, temperature, humidity) and 'dynamic' (vertical motion of air, horizontal wind) controls in outbreaks are identified. Last, we demonstrate potential utility of the spatial overlap method by deriving fallseason surface station trends (1951-1993) of sky cover variables for contrasting high versus low contrail and overlap frequency grid cells in the eastern CONUS. These suggest a contrail contribution to recent high-cloud increases, notably for the Midwest.

The impacts of long‐lived jet contrail ‘outbreaks’ on surface station diurnal temperature range

“…The daily spatial inventories of contrail clear‐sky outbreaks for the south sub‐region of the CONUS in January and the Midwest in April (both 2008–2009), resulted from visual interpretation of Advanced Very High Resolution Radiometer (AVHRR) satellite thermal IR images that were available between six and eight times per day for the entire country (Carleton et al ., ). Each outbreak inventory was depicted on spreadsheets and also on maps having a 1° × 1° grid resolution in a GIS.…”

“…Separate inventories of contrail outbreaks were developed in the same manner for mid‐season months of 2000–2002 (Travis et al , ; Carleton et al , ). These comprise the baseline ‘climatology’ (Figures and ), from which the individual 2008 and 2009 spatial inventories are subtracted to yield examples of recent outbreak inter‐annual variations (Carleton et al , ). The climatologically high frequencies of outbreaks in the South during January 2008–2009, and Midwest during April 2008–2009, underscore why these particular months and sub‐regions were selected for the analysis.…”

“…To better assess the impacts of contrail clear‐sky outbreaks on near‐surface climate, a fuller understanding of their influence on DTR is warranted. In pursuit of this objective, we undertake an observational study that compares the DTR at pairs of first‐order weather stations in two high‐contrail frequency sub‐regions of the CONUS (see DeGrand et al ., ; Carleton et al ., , ) for 2 years' mid‐season months; the South in January 2008 and 2009, and the Midwest in April 2008 and 2009. We adopt a composite (i.e.…”

“…That catalogue used manual identification (i.e. visual interpretation) of outbreaks appearing on high‐resolution polar orbiter images for the CONUS (Travis et al ., ; Carleton et al ., , ). The months of January and April were selected because they had the highest number of suitable outbreaks in this study of potential DTR impacts.…”

Statistical analysis of contrail to cirrus evolution during the Contrail and Cirrus Experiment (CONCERT)

“…The life cycle of contrails depends on their interaction with the wake vortices behind aircraft and the ambient atmosphere (Irvine et al, 2012;Graf et al, 2012;Carleton et al, 2013;Schumann and Heymsfield, 2017). The ice crystals in the young contrails are captured within two counter-rotating wake vortices in the downwash behind the aircraft induced by the aircraft lift; these vortices induce adiabatic compression, heating, and partial sublimation of the ice crystals within the primary wake (Lewellen and Lewellen, 2001;Sussmann and Gierens, 2001;Unterstrasser et al, 2008Unterstrasser et al, , 2016Kärcher and Voigt, 2017).…”