The Evolution of the Stratopause During the 2006 Major Warming: Satellite Data and Assimilated Meteorological Analyses

Microwave Limb Sounder and Sounding of the Atmosphere with Broadband Emission Radiometry data show the polar stratopause, usually higher than and separated from that at midlatitudes, dropping from <55-60 to near 30 km, and cooling dramatically in January 2006 during a major stratospheric sudden warming (SSW). After a nearly isothermal period, a cool stratopause reforms near 75 km in early February, then drops to <55 km and warms. The stratopause is separated in longitude as well as latitude, with lowest temperatures in the transition regions between higher and lower stratopauses. Operational assimilated meteorological analyses, which are not constrained by data at stratopause altitude, do not capture a secondary temperature maximum that overlies the stratopause or the very high stratopause that reforms after the SSW; they underestimate the stratopause altitude variation during the SSW. High-quality daily satellite temperature measurements are invaluable in improving our understanding of stratopause evolution and its representation in models and assimilation systems

Calibration of the NASA scatterometer using a ground calibration station

To aid in calibrating and monitoring the performance of the NASA scatterometer (NSCAT), a calibration ground station (CGS) was operated in White Sands, New Mexico from mid November 1996 through February 1997. The CGS was used to verify the proper operation of the NSCAT system including transmit power, frequency, pulse width, and receiver gain. It was also used to track spacecraft attitude variation, and to measure the antenna gain balance between different beams. This paper will describe the basic operation of the CGS, and the principle results obtained during the calibration period. The CGS is a transmit/receive system which was used to record pulses from NSCAT, and to transmit pulses back to NSCAT. The C(W data was synchronized with NSCAT telemetry, and processed for timing, frequency, and gain information. These results were then compared with the values expected using the nominal pre-launch calibration data. Timing discrepancies indicated significant spacecraft attitude variations beyond the values reported in telemetry. Gain discrepancies showed a small ascending/descending difference. The cause of this difference (NSCAT or the CGS) is not clear at this time