Bright polar mesospheric clouds formed by main engine exhaust from the space shuttle's final launch

Abstract

[1] The space shuttle launched for the last time on 8 July 2011. As with most shuttle launches, the three main engines injected about 350 t of water vapor between 100 and 115 km off the east coast of the United States during its ascent to orbit. We follow the motion of this exhaust with a variety of satellite and ground-based data sets and find that (1) the shuttle water vapor plume spread out horizontally in all directions over a distance of 3000 to 4000 km in 18 h, (2) a portion of the plume reached northern Europe in 21 h to form polar mesospheric clouds (PMCs) that are brighter than over 99% of all PMCs observed in that region, and (3) the observed altitude dependence of the particle size is reversed with larger particles above smaller particles. We use a one-dimensional cloud formation model initialized with predictions of a plume diffusion model to simulate the unusually bright PMCs. We find that eddy mixing can move the plume water vapor down to the mesopause near 90 km where ice particles can form. If the eddy diffusion coefficient is 400 to 1000 m 2 /s, the predicted integrated cloud brightness is in agreement with both satellite and ground-based observations of the shuttle PMCs. The propellant mass of the shuttle is about 20% of that from all vehicles launched during the northern 2011 PMC season. We suggest that the brightest PMC population near 70 N is formed by space traffic exhaust.

Recent observations of high mass density polar mesospheric clouds: A link to space traffic?

“…The table shows that space traffic released more H 2 O in 2011 than in any year since the beginning of the AIM mission. The effects of STS 135, launched on 8 July 2011 at 11:40 EDT, have already been documented, and it was shown that some of the brightest PMCs ever observed by CIPS and from the ground were formed from the main engine exhaust of this shuttle [ Stevens et al ., ]. This is consistent with not only the July 2011 enhancement we see here but also the occurrence of very high IWC in the 2011 SOFIE data (Figure ).…”

“…Our suggestion that the explanation lies in an H 2 O source from space traffic steps beyond previous discussions of this effect in three ways. First, previous reports have concentrated on relatively isolated events of PMC production by shuttle exhaust [e.g., Stevens et al ., , ]. Here we are suggesting that average PMC mass density and frequency, and its year‐to‐year variability from 2007 to 2012, are modulated by space traffic.…”

Contrail formation in the tropopause region caused by emissions from an Ariane 5 rocket

“…A water vapor plume leading to the formation of an exceptionally bright PMC has been observed in a variety of satellite and ground based data sets as result of emissions from the main engines from the space shuttle£s ¦nal launch in July 2011 [15]. Rocket emissions might explain the brightest fraction of the PMC population and interestingly larger ice particles were found above the smaller ones within the PMC.…”

Evaluation of Space Traffic Effects in SBUV Polar Mesospheric Cloud Data

“…Stevens et al () looked at a subsequent Shuttle launch during the NH PMC season and identified a distinct postlaunch enhancement in PMC occurrence frequency and calculated IWC, using National Oceanic and Atmospheric Administration (NOAA)‐14 SBUV/2 PMC data. Shuttle‐related signals in PMC data have since been reported for five additional launches during the period 1999–2011 (Collins et al, ; Kelley et al, , ; Stevens et al, ; Stevens et al, ; Stevens et al, ). Table briefly summarizes these published results.…”