# Presentation: 095265

## ACE Stratospheric Measurements of NOx during February-March 2004:  Impact of Intense Solar Flares

**Curtis P. Rinsland,****1**** Chris Boone,****2**** Ray Nassar****2****, Kaley Walker,****2**** Peter Bernath,****2**** John C. McConnell,****3**** Linda Chiou****4**
**1****NASA Langley Research Center, Hampton, VA  U.S.A.**
**2****Department of Chemistry, University of Waterloo, Ontario, Canada**
**3****Department of Earth and Atmospheric Sciences, York University, Ontario, Canada**
**4****System and Applied Sciences Corporation, Hampton, VA  U.S.A.**

## ACE Measurements of Elevated NOx during February-March 2004

- The Sun produced some of the most powerful solar flares ever recorded during October and November 2003
- The X-class solar proton event, resulting coronal mass ejections, and energetic particle precipitation led to large increases in energy deposition and NOx production with elevated levels observed by HALOE, GOME, and the MIPAS FTS during winter 2003-2004
- Elevated NOx measurements and their impact on O3 levels observed by several satellite experiments during this time period have been summarized recently (C. Randall et al., GRL in press).
- Intense emissions due to auroral activity likely contributed to the enhanced NOx levels observed at high northern latitudes during that winter [Semeniuk et al., GRL, 2005, submitted]

## ACE Time Series

- Routine measurements from ACE began in February 2004 from an orbit optimized to obtain frequent coverage of the Arctic during the spring period of maximum O3 depletion
- Analysis reported here is based on version 1 retrievals [Boone et al., 2005] with NOx levels higher than any previously reported values in the Arctic (mixing ratios of NO >1.3 ppmv )

## ACE NOx Time Series

- Individual ACE measurements were analyzed assuming the derived meteorological data assimilation products calculated for the location of individual ACE measurements by Gloria Manney (JPL, private communication, 2004)
- Empirically we assumed scaled potential vorticity >2.0 between 0.07- 2 hPA (~40-60 km) to assign the measurement as a vortex observation
- Our study and another ACE analysis focused on the ~30-50 km region of the stratosphere (R. Nassar et al., GRL, submitted, 2005) provide an opportunity to identify regions with a substantial high altitude barrier to transport in the Arctic during that time period
- NOx is not an inert tracer though it has a long lifetime during high latitude darkness [Solomon et al., JGR, 87, 5206-4220,1982]
- Photochemical model calculations for the mid-February to late March time period and latitude of the ACE measurements indicate the lifetime of NOx near the stratopause is 1-2 months with the NOx lifetime increasing to lower altitudes (M. Natarajan, NASA Langley, private communication, 2005)

## Slide 5

## NOx Dilution in the vortex

- The NOx  time series was fitted with the empirical expression
-      [NOx](t) = [NOx](tref) exp(-*k*(t-tref)   		(1)
-     where [NOx](t) is the NOx vortex volume mixing ratio at time *t*, tref is the time of the first measurement, and *k* is the NOx decrease rate (day-1).  The best fit with Eq. 1 indicates the vortex volume mixing ratios decreased from 1361.0 ppbv at the beginning of the time series (February 15, 2004) to 109.8 ppbv at the end (March 23, 2004) during the 5 week measurement time period.  The best fit yields a coefficient *k* equal to (0.0689±0.005827) day-1

## NOx Descent in the vortex

- The vortex observation time series with the expression
-         Z(t)= Z(tref) + *d*(t-tref )				(2)
-     where Z(t) is the altitude (km) of the vortex at time t and *d* is the vortex descent rate (km day-1), assumed linear with time.
- The vortex descended by 9 km from 54 to 45 km.  The best fit descent coefficient *d* equals (-0.2600±0.0144) km day-1
- ACE descent rate inferred in this work is roughly consistent with the early Arctic winter lower mesospheric descent rates reported by previous experiments (e.g. Greenblatt et al. [2002] (J. Geophys. Res., 107, D20, doi: 10.1029) from *in situ* and remotely-sensed N2O and CH4 measurements during 1999/2000 and model calculations

## Slide 8

## Summary and Conclusions

- ACE measured the highest reported NOx levels in the Arctic during February and March 2004
- We attribute the elevated NOx to the solar storms from the previous October-November followed by downward transport during Arctic darkness with descent and mixing ratios of NO as high as 1.3 ppmv measured in the Arctic vortex with an additional contribution from auroral emissions
- Our analysis suggests that a substantial barrier to transport existed in the upper stratosphere/lower mesosphere, at least during the time of the ACE February-March 2004 observations consistent with the meteorological analysis of Manney et al., JGR, in press, 2005.

## Lower Stratospheric Trends from a Comparison of ATMOS and ACE Measurements near 30oN Latitude 

**Curtis P. Rinsland,****1**** Peter Bernath,****2**** Ray Nassar,****2**** Chris Boone,****2**** Kaley Walker,****2**** and Linda Chiou****3**
**1****NASA Langley Research Center, Hampton, VA  U.S.A.**
**2****Department of Chemistry, University of Waterloo, Ontario, Canada**
**3****System and Applied Sciences Corporation, Hampton, VA  U.S.A.**

## Measurements

- ATMOS and ACE both recorded high spectral resolution solar occultation spectra covering the mid-infrared with an overlap in coverage near 30oN latitude
- ATMOS:  Spacelab 3 (April 29-May 6, 1985), ATLAS-1 (24 March-3 April 1992), ATLAS 2 (8-16 April 1993 (600-4800 cm-1), and November 1994 at 0.01 cm-1 resolution
- ACE:  August 2004 launch (750-4500 cm-1) at 0.02 cm-1 resolution

## Trend Analysis Approach

- Compare measured lower stratospheric volume mixing ratios from each time period for HF, HCl, CCl2F2, CCl3F, CHClF2, and SF6 with those of N2O to deduce trends for each molecule as a function of time
- Number of occultations depends on molecule with ACE providing the most events (~30) with fewer from ATLAS 3 (~5), and the fewest from Spacelab 3 (~2)
- Measured volume mixing ratios (VMRs) from each time period referenced to those of the long-lived constituent N2O to account for variations in the dynamic history of the sampled airmasses
- N2O mixing ratios corrected for the increase with time (we refer to the N2O-trend corrected volume mixing ratios as N2O* (Elkins *et al.,* AGU 2004 meeting )
- Mean and statistical uncertainties of lower stratospheric mixing ratios calculated for each time period from overlapping mixing ratio and N2O* intervals
- Empirical trend formula: V = a0 + a1(t-t0) + a2(t-t0)**2 used to fit the time series where t is time and t0 is the date of the first ATMOS mission and a0, a1, and a2 are coefficients derived for each molecule

## ATMOS/ACE HF mixing ratios (left) with best-fit volume mixing ratios and trends in percent (right)

- 20.52±7.88

- 4.49±4.26

- 0.02±5.48

- 20.52±7.88

- 4.49±4.26

- 0.02±5.48

- A slow down in the HF accumulation rate is observed, consistent with ground-based solar absorption measurements.

## HCl from ATMOS/ACE measurements (left) with mixing ratios and trends in percent (right) 

- 9.13±2.73

- 1.59±2.37

- -3.62±4.08

- Time series provides evidence for an onset of a decline in HCl, consistent with ground-based solar absorption measurements and model predictions confirming the effectiveness of the Montreal Protocol

## ATMOS/ACE CCl2F2 Measurements (left) with best-fit volume mixing ratios and trend in percent (right)

- 6.14±2.34

- 1.56±2.27

- -1.67±3.60

- CCl2F2 is close to its maximum with evidence for an expected slow, long-term decline consistent with other measurements and model predictions

## ATMOS/ACE CCl3F Measurements vs. N2O* (left) with  best-fit mixing ratios and trend in percent (right)

- 12.61±4.24

- 2.58±3.11

- -2.42±4.80

- Evidence for the impact of the Montreal Protocol emission restrictions is observed, consistent with other reported measurements and model predictions

## CHF2Cl vs. N2O* (left) with best-fit mixing ratios and trend (right) from ATMOS/ACE measurements (right)

- 14.57±4.10

- 6.35±2.24

- 3.92±2.08

- A continuous rise in CHF2Cl is observed, consistent with ground-based solar and other long-term trend measurements

## SF6 vs. N2O* measurements (left) with best-fit volume mixing ratios and Trend (right)

- 10.28±2.28

- 7.48±1.33

- 5.57±1.07

- A rapid increase in SF6 continues, consistent with reported surface and infrared ground-based solar absorption trend measurements

## Conclusions

- Lower stratospheric trends for HF, HCl, CCl2F2, CCl3F, CHClF2 (HFCFC-22) and SF6 have been derived from ATMOS 1985, ATMOS 1994, and ACE 2004 measurements near 30oN latitude
- Results are consistent with previously reported measurements and model results demonstrating  the capabilities of the ATMOS-ACE database to provide precise important information on long-term atmospheric trends
- Impact of Montreal Protocol restrictions observed for HCl (evidence for an onset of a slow decline ), CCl2F2, and CCl3F
- Continued increases observed for CHClF2 (HFCFC-22) and SF6