Cross-calibration of UARS and Aura MLS HNO3 data sets by means of ground-based millimeter-wave Observations

• Published in: Journal of Geophysical Research: Atmospheres
• Main Authors: Fiorucci, I., Muscari, G., Froidevaux, L., Santee, M. L., De Zafra, R. L.
• Other Authors: Fiorucci, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia, Muscari, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia, Froidevaux, L.; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA, Santee, M. L.; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA, De Zafra, R. L.; State University of New York, Stony Brook, NY, USA, Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA, State University of New York, Stony Brook, NY, USA
• Format: Other/Unknown Material
• Language: English
• Published: 2010
• Subjects: millimeter wave spectroscopy; stratospheric HNO3; Satellite validation; 01. Atmosphere::01.01. Atmosphere::01.01.01. Composition and Structure; 01. Atmosphere::01.01. Atmosphere::01.01.04. Processes and Dynamics; 01. Atmosphere::01.01. Atmosphere::01.01.08. Instruments and techniques; Greenland; South Pole; Thule Air Base; Antarc*; Antarctica; South pole; Thule Air; Thule
• Online Access: http://hdl.handle.net/2122/6662

Nitric acid (HNO3) is a major player in processes controlling the springtime depletion of polar ozone. It is the main constituent of the Polar Stratospheric Clouds (PSCs) and a primary reservoir for reactive nitrogen. Potential variations in the stratospheric circulation and temperature may alter the extent and duration of PSCs activity, influencing the future ozone levels significantly. Monitoring HNO3 and its long-term variability, especially in polar region, is then crucial for better understanding issues related to ozone decline and expected recovery. In this study we present an intercomparison between ground based HNO3 measurements, carried out by means of the Ground-Based Millimeter-wave Spectrometer (GBMS), and two satellite data sets produced by the two NASA/JPL Microwave Limb Sounder (MLS) experiments. In particular, we compare UARS MLS measurements (1991-1999) with those carried out by the GBMS at South Pole, Antarctica (90°S), Fall of 1993 and 1995. A similar intercomparison is made between Aura MLS HNO3 observations (2004 - to date) and GBMS measurements obtained during the period February 2004 - March 2007, at the mid-latitudes/high altitudes station of Testa Grigia (45.9° N, 7.7° E, elev. 3500 m), and during polar winters 2008/09 and 2009/2010 at Thule Air Base (76.5°N 68.8°W), Greenland. We assess systematic differences between GBMS and both UARS and Aura HNO3 data sets at seven potential temperature levels (θ) spanning the range 465 – 960 K. The UARS data set advected to the South Pole shows a low bias, within 20% for all θ levels but the 960 K, with respect to GBMS measurements. A very good agreement, within 5%, is obtained between Aura and GBMS observations at Testa Grigia, while larger differences, possibly due to latitude dependent effects, are observed over Thule. These differences are under further investigations but a preliminary comparison over Thule among MLS v3, GBMS, and ACE-FTS measurements suggests that GBMS measurements carried out during winter 2009 might not be reliable. These ...