Evidence of impact of aviation on cirrus cloud formation

Abstract

Abstract. This work examines changes in cirrus cloud cover (CCC) in possible association with aviation activities at congested air corridors. The analysis is based on the latest version of the International Satellite Cloud Climatology Project D2 data set and covers the period 1984-1998. Over the studied areas, the effect of large-scale modes of natural climate variability such as ENSO, QBO and NAO as well as the possible influence of the tropopause variability, were first removed from the cloud data set in order to calculate long-term changes of observed cirrus cloudiness. The results show increasing trends in (CCC) between 1984 and 1998 over the high air traffic corridors of North America, North Atlantic and Europe. Of these upward trends, only in the summertime over the North Atlantic and only in the wintertime over North America are statistically significant (exceeding +2.0% per decade). Over adjacent locations with low air traffic, the calculated trends are statistically insignificant and in most cases negative both during winter and summer in the regions studied. These negative trends, over low air traffic regions, are consistent with the observed large scale negative trends seen in (CCC) over most of the northern middle latitudes and over the tropics. Moreover, further investigation of vertical velocities over high and low air traffic regions provide evidence that the trends of opposite signs in (CCC) over these regions, do not seem to be caused by different trends in dynamics. It is also shown that the longitudinal distribution of decadal changes in (CCC) along the latitude belt centered at the North Atlantic air corridor, parallels the spatial distribution of fuel consumption from highflying air traffic, providing an independent test of possible impact of aviation on contrail cirrus formation. The correlation between the fuel consumption and the longitudinal variability of (CCC) is significant (+0.7) over the middle latitudes but not over the tropics. This could be explained by the fact that over the tropics Correspondence to: C. S. Zerefos (zerefos@geol.uoa.gr) the variability of (CCC) is dominated by dynamics while at middle latitudes microphysics explain most of its variability. Results from this study are compared with other studies and for different periods of records and it appears that there exists general agreement as to the evidence of a possible aviation effect on high cloud positive trends over regions with congested air traffic.

Global patterns in daytime cloud properties derived from GOME backscatter UV-VIS measurements

“…The mean ISCCP total cloud amount for this band is ,65%, while there is almost no trend in the cloud coverage. There are however trends in the amount of cloud types, as noted by Zerefos et al (2003) for cirrus clouds, which is presumably due to increasing air traffic. The trend in the GOME series is probably linked to the degradation of the instrument's solar diffuser -this affects the COT deviation (%) GOME cloud optical thickness monthly mean 14.48, trend −1.07% ISCCP cloud optical thickness monthly mean 9.04, trend +1.35% Figure 9.…”

Ground-based observations for the validation of contrails and cirrus detection in satellite imagery

“…The coverage of aviation-induced cirrus is estimated to be 1.8 to 10 times higher than the one caused by contrails . According to Stordal et al (2005) cirrus coverage in Europe increased by 1-2% per decade, Zerefos et al (2003) find a value of 1.8% for Europe. The optical thickness of contrails on global average lies between 0.15 and 0.25 (Minnis et al, 2005), Meyer et al (2002) found a lower value of 0.1 for Europe.…”

Modeling the present and future impact of aviation on climate: an AOGCM approach with online coupled chemistry

“…The detection (measurement), properties, formation, evolution and radiative effects of linear-shaped contrails and/or the contrail-induced cloudiness have been subject to a large number of studies (Zerefos et al, 2003;Schumann, 2005;Stordal et al, 2005;Gao et al, 2006;Hong et al, 2008;Frömming et al, 2011). The physical mechanism behind its formation is now well understood; however, due to the uncertainties in the modeling of its occurrence and of its properties varying in time and space, the calculation of the related RF is still marked by a low to very-low level of scientific understanding .…”