Validation of the Aura Microwave Limb Sounder ClO measurements

Abstract

[1] We assess the quality of the version 2.2 (v2.2) ClO measurements from the Microwave Limb Sounder (MLS) on the Earth Observing System Aura satellite. The MLS v2.2 ClO data are scientifically useful over the range 100 to 1 hPa, with a single-profile precision of $0.1 ppbv throughout most of the vertical domain. Vertical resolution is $3-4 km. Comparisons with climatology and correlative measurements from a variety of different platforms indicate that both the amplitude and the altitude of the peak in the ClO profile in the upper stratosphere are well determined by MLS. The latitudinal and seasonal variations in the ClO distribution in the lower stratosphere are also well determined, but a substantial negative bias is present in both daytime and nighttime mixing ratios at retrieval levels below (i.e., pressures larger than) 22 hPa. Outside of the winter polar vortices, this negative bias can be eliminated by subtracting gridded or zonal mean nighttime values from the individual daytime measurements. In studies for which knowledge of lower stratospheric ClO mixing ratios inside the winter polar vortices to better than a few tenths of a ppbv is needed, however, day À night differences are not recommended and the negative bias must be corrected for by subtracting the estimated value of the bias from the individual measurements at each affected retrieval level.

20 years of ClO measurements in the Antarctic lower stratosphere

“…The version 2.2 ClO measurements were validated in Santee et al (2008). Here, we use the v4.2 retrievals (Livesey The times for these measurements remain consistent within ±4 min throughout the entire Aura mission.…”

“…The loweraltitude ClO continues to show a gradual increase until midSeptember and then experiences a sharp decline, as it converts back to the reservoir gases. Santee et al (2008) present a detailed study of the seasonal evolution of the partitioning between ClO, HCl (from MLS), and ClONO 2 (from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer; ACE-FTS) in the Arctic and Antarctic. Figure 3 shows measurements of day minus night ClO column from ChlOE during 2006 together with those from the coincident (within ±2 • latitude and ±15 • longitude of Scott Base) MLS measurements.…”

Variability in Antarctic ozone loss in the last decade (2004–2013): high-resolution simulations compared to Aura MLS observations

“…The time resolution of the measurements is about 3500 profiles per day. The estimated uncertainty of typical ozone and ClO retrievals is about 5-10 and 10-20 %, respectively (Livesey et al, 2013;Santee et al, 2008a;Froidevaux et al, 2008). For a comparison with the measurements, the model results (6 h output) are interpolated to the measurement locations.…”

“…Large variability in Antarctic ozone loss has been seen in the last few years (2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013) relative to other winters since 1992 (e.g., Tilmes et al, 2006;Huck et al, 2007;Yang et al, 2006;Santee et al, 2008a). For instance, the winters of 2004, 2010, and 2012 were relatively warm, with minor warmings and, hence, limited ozone loss (Santee et al, 2005;de Laat and van Weele, 2011;WMO, 2014).…”

Antarctic ozone variability inside the polar vortex estimated from balloon measurements

“…In Belgrano it is about 200 h, while at SPS it is 668 h. Greater rates of accumulated light could lead to activation of more halogen compounds at SPS. Santee et al (2008) found a positive chlorine gradient toward the pole for this season by analysing AURA-MLS data. Therefore, more activated chlorine at SPS could be responsible of the higher ozone loss rate.…”