ACCURACY AND PRECISION OF CRYOGENIC LIMB ARRAY ETALON SPECTROMETER (CLAES) TEMPERATURE RETRIEVALS

The Cryogenic Limb Array Etalon Spectrometer (CLAES) measured emission from the 792 cm(-1) Q branch of CO2, from which temperature distribut ions in the stratosphere and low mesosphere were derived, Here we brie fly review the measurement technique, concentrating on aspects that af fect the temperature determination, Comparison of many pairs of retrie vals at the same location (near 32 degrees N or 32 degrees S) measured on sequential orbits (time separation of 96 min) shows a precision ra nging from approximately 0.8 K at 68 mbar to about 3.5 K at 0.2 mbar, which agrees with simulations incorporating random noise and short-per iod spacecraft motions, Comparisons of globally analyzed CLAES data wi th National Meteorological Center (NMC) and U.K. Meteorological Office (UKMO) analyses show general agreement, with CLAES tending to be cool er by about 2 K, except in the tropics and high-latitude winter condit ions. This is supported by comparisons with individual radiosondes and several lidars that indicate that the agreement is within 2 K through out the profile (except for a narrow layer around 3 mbar). An error an alysis also indicates that systematic errors should be roughly 2 K, in dependent of altitude, The systematic differences at low latitudes app ear to be due to tropical waves, which have vertical wavelengths too s hort to be seen by the TIROS Operational Vertical Sounder (TOVS) instr uments. There are no correlative rocketsondes or lidars to help resolv e the reasons for the high-latitude differences. Comparisons with othe r Upper Atmosphere Research Satellite (UARS) data should shed addition al light on this question.