Did The Time Dependence Of HALOE Sampling Affect The Upper Stratospheric HCl Trend?
Abstract
Measurements of HCl by the Halogen Occultation Experiment (HALOE) on the Upper Atmosphere Research Satellite have previously been used to show the time dependence of the upper-stratospheric HCl concentration. The time series constructed from HALOE showed that the chlorine content of the upper stratosphere is responding to the limitation of chlorofluorocarbons (CFCs) due to the Montreal Protocol. The time series also showed some fluctuations that remain unexplained. We examine the effects of HALOE sampling on the time series of upper stratospheric HCl. From launch in 1991 until (1994) HALOE was in near continuous operations, and the spatial sampling pattern was such that it was possible to adjust for the small seasonal variation in HCl when calculating the HCl time series.. In 1995, an anomaly with the solar array limited the power available for operations. UARS operated in a power-sharing mode, and HALOE operations were restricted. The HALOE sampling pattern was such that relatively few measurements were made between 40S and 60S latitude during Oct-Nov-Dec and between 40N and 60N latitude during April-May-June. In each hemisphere this is the time of the seasonal maximum in a simulation using the Goddard three-dimensional chemistry and climate model. The seasonal cycle in the model is evaluated using observations from HALOE, the Atmospheric Chemistry Experiment (ACE) on Sci-Sat, and the Microwave Limb Sounder on Aura. Trends calculated with full sampling of the CCM are compared with those calculated from the CCM as sampled by HALOE. From this it is demonstrated that much of the unexplained variability in the HCl time series is a result of time-dependent sampling issues.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.A54B..05D
- Keywords:
-
- 0340 ATMOSPHERIC COMPOSITION AND STRUCTURE / Middle atmosphere: composition and chemistry