The Measurements of Pollution in the Troposphere (MOPITT) instrument, which was launched aboard the Earth Observing System (EOS) Terra spacecraft on 18 December 1999, is designed to measure tropospheric CO and CH(4) by use of a nadir-viewing geometry. The measurements are taken at 4.7 mum in the thermal emission and absorption for the CO mixing ratio profile retrieval and at 2.3 and 2.2 mum in the reflected solar region for the total CO column amount and CH(4) column amount retrieval, respectively. To achieve the required measurement accuracy, it is critical to identify and remove cloud contamination in the radiometric signals. We describe an algorithm to detect cloudy pixels, to reconstruct clear column radiance for pixels with partial cloud covers, and to estimate equivalent cloud top height for overcast conditions to allow CO profile retrievals above clouds. The MOPITT channel radiances, as well as the first-guess calculations, are simulated with a fast forward model with input atmospheric profiles from ancillary data sets. The precision of the retrieved CO profiles and total column amounts in cloudy atmospheres is within the expected ?10% range. Validations of the cloud-detecting thresholds with the moderate-resolution imaging spectroradiometer airborne simulator data and MOPITT airborne test radiometer measurements were performed. The validation results showed that the MOPITT cloud detection thresholds work well for scenes covered with more than 5-10% cloud cover if the uncertainties in the model input profiles are less than 2 K for temperature, 10% for water vapor, and 5% for CO and CH(4).

Measurement of Pollution in the Troposphere (MOPITT) is an eight-channel gas correlation radiometer selected for the Earth Observing System AM-1 platform to be launched in 1999. Its primary objectives are the measurement of tropospheric carbon monoxide (CO) and methane (CH(4)). In this paper, the sensitivities of instrument signals and CO retrieval errors to various instrument parameters, especially the gas cell pressure and temperature variations, instrument radiometric noise, and ancillary data errors (such as atmospheric temperature and water vapor profile errors), are presented and discussed. In the MOPITT pressure modulator sell pressure sensitivity study, the instrument calibration process is considered, which leads to the relaxation of previous stringent requirements on the accuracy of in-orbit cell pressure monitoring. The approach of MOPITT CO retrieval error analysis is described, and the error analysis results are compared with retrieval simulation statistics. The error analysis results indicate that tropospheric CO distributions can be retrieved with a precision of 10% for most of the troposphere.

Global tropospheric carbon monoxide (CO) distributions can be retrieved from observations by spaceborne gas correlation radiometers and high-resolution interferometers. The Measurement of Pollution in the Troposphere (MOPITT) is a gas correlation radiometer designed for tropospheric CO and CH(4) remote sensing. It is being developed at the University of Toronto and the National Center for Atmospheric Research for launch on the EOS/AM-1 platform in 1999. Spaceborne high-resolution interferometers with troposphere CO remote sensing capability include the Interferometric Monitor for Greenhouse gases (IMG) instrument and the Troposphere Emission Spectrometer (TES). IMG was developed by the Ministry of International Trade and Industry (MITI) of Japan. It was on the ADEOS-1 spacecraft launched in October 1996. TES is being developed by the Jet Propulsion Laboratory for launch on the EOS/CHEM-1 platform in 2002.For the purpose of testing the MOPITT data processing algorithms before launch, a new digital gas correlation (DGC) method was developed. This method makes it possible to use existing IMG observations to validate the MOPITT retrieval algorithms. The DGC method also allows the retrieval of global troposphere CO from MOPITT, IMG, and TES observations with a consistent algorithm. The retrieved CO profiles can be intercompared, and a consistent long time series of tropospheric CO measurements can be created. In this paper, the DGC method is described. The procedures for using the DGC method to retrieve atmospheric trace species profiles are discussed. As an example, CO profiles from IMG observations have been retrieved with the DGC method as a demonstration of its feasibility and application in MOPITT retrieval algorithm validation.

Tropospheric concentrations of methane have been increasing at a rate of approximately 1% / year, though recent measurements suggest some slowing in this trend. Increased concentrations of methane, a greenhouse gas, will have significant consequences for tropospheric chemistry and climate on a global scale. Characterization of the spatial and temporal variability of methane is one goal of the MOPITT (Measurement of Pollution In The Troposphere) instrument included on the EOS Terra satellite. This instrument includes spectral channels designed to measure methane total column with approximately 1% precision with a spatial resolution of approximately 22 x 22 km.Retrieval of the methane total column will be accomplished by the MOPITT instrument from measurements of solar radiation reflected at the earth's surface. Gas correlation radiometry will be used to separate the spectral signature of methane in the upwelling radiance from features produced by other trace gases. The retrieval algorithm is based on maximum likelihood and uses an initial guess profile and methane total column variance estimates provided by aircraft insitu measurements. In this talk, we will describe features of the retrieval algorithm in detail and present results of retrieval simulations conducted to test the sensitivity of the retrieval algorithm to various sources of error.

The Measurement of Pollution in the Troposphere (MOPITT) instrument is an eight-channel gas correlation radiometer to be launched on the Earth Observing System (EOS) Terra spacecraft in 1999. Its main measurement objectives are tropospheric carbon monoxide (CO) profiles and total column. This paper gives a detailed description of MOPITT CO retrieval algorithm, which derives total CO column and tropospheric CO mixing ratios at a number of atmospheric pressure levels from MOPITT radiance observations. Retrieval performance evaluation using simulated MOPITT data are discussed.

A retrieval method for deriving the tropospheric carbon monoxide (CO) profile and column amount under clear sky conditions has been developed for the Measurements of Pollution In The Troposphere (MOPITT) instrument, scheduled for launch in 1998 onboard the EOS‐AM1 satellite. This paper presents a description of the method along with analyses of retrieval information content. These analyses characterize the forward measurement sensitivity, the contribution of a priori information, and the retrieval vertical resolution. Ensembles of tropospheric CO profiles were compiled both from aircraft in situ measurements and from chemical model results and were used in retrieval experiments to characterize the method and to study the sensitivity to different parameters. Linear error analyses were carried out in parallel with the ensemble experiments. Results of these experiments and analyses indicate that MOPITT CO column measurements will have better than 10% precision, and CO profile measurement will have approximately three pieces of independent information that will resolve 3–5 tropospheric layers to approximately 10% precision. These analyses are important for understanding MOPITT data, both for application of data in tropospheric chemistry studies and for comparison with in situ measurements.

Observations of the global distribution of nitric acid (HNO3) obtained by the Cryogenic Limb Array Etalon Spectrometer (CLAES) instrument on the Upper Atmospheric Research Satellite (UARS) have considerably extended our knowledge of its spatial and temporal distribution. The data span 16 months, and extend to 80 °S, within the Antarctic vortex during southern winter. The evaluation of the accuracy, precision, and resolution of these data are briefly described. The zonal mean distribution of nitric acid is characterized by a stratospheric layer with largest mixing ratios near 30 hPa in polar regions, sloping up to a slightly higher altitude but low mixing ratios in the tropics. New features are regions of very low nitric acid within the Antarctic vortex, and sensitivity to stratospheric aerosol concentration.

BACKGROUND:Large doses of intravenous opioids may cause severe rigidity and prevent spontaneous or controlled ventilation. The mechanism of this effect appears to be neuraxis dopamine antagonism. Rigidity after analgesic doses of fentanyl has not been reported previously.CASE:A pregnant woman receiving haloperidol for multiple psychiatric conditions presented for evaluation of vaginal bleeding. Intravenous fentanyl was administered to facilitate vaginal examination. Severe rigidity of the extremities and truncal region occurred, which prevented spontaneous or assisted ventilation.CONCLUSION:Opioid administration may result in rigidity and respiratory embarrassment. Decreased analgesic requirements in pregnancy and concomitant butyrophenone administration may predispose to opioid-induced rigidity.

CH4 and N2O are useful as dynamical tracers of stratospheric air transport because of their long photochemical lifetimes over a wide range of altitudes. The cryogenic limb array etalon spectrometer (CLAES) instrument on the NASA UARS provided simultaneous global measurements of the altitude profiles of CH4 and N2O mixing ratios in the stratosphere between October 1, 1991, and May 5, 1993. Data between January 9, 1992, and May 5, 1993 (388 days), have been processed using version 7 data processing software, and this paper is concerned with the assessment of the quality of this data set. CLAES is a limb‐viewing emission instrument, and approximately 1200 profiles were obtained each 24‐hour period for each constituent over a nominal altitude range of 100 to 0.1 mbar (16 to 64 km). Each latitude was sampled 30 times per day between latitudes 34°S and 80°N, or 34°N and 80°S depending on the yaw direction of the UARS, and nearly all local times were sampled in about 36 days. This data set extends the altitude, latitude, and seasonal coverage of previous experiments, particularly in relation to measurements at high winter latitudes. To arrive at estimates of experiment error, we compared CLAES profiles for both gases with a wide variety of correlative data from ground‐based, rocket, aircraft, balloon, and space‐borne sensors, looked at the repeatability of multiple profiles in the same location, and carried out empirical estimates of experiment error based on knowledge of instrument characteristics. These analyses indicate an average single‐profile CH4 systematic error of about 15% between 46 and 0.46 mbar, with CLAES biased high. The CH4 random error over this range is 0.08 to 0.05 parts per million, which translates to about 7% in the midstratosphere. For N2O the indicated systematic error is less than 15% at all altitudes between 68 and 2 mbar, with CLAES tending to be high below 6.8 mbar and low above. The N2O random error is 20 to 5 ppb between 46 and 2 mbar, which also translates to 7% in the low to midstratosphere. Both tracers have useful profile information to as low as 68 mbar, excluding the tropics, and as high as 0.2 mbar (CH4) and 1 mbar (N2O). The global fields show generally good spatial correlation and exhibit the major morphological and seasonal features seen in previous global field data. Several morphological features are pointed out for regions and conditions for which there have been essentially no previous data. These include the differential behavior of the tracer isopleths near and inside the Antarctic winter vortex, and local maxima in the tropics in 1992, probably associated with the Mount Pinatubo sulfate aerosol layer. Overall, the results of this validation exercise indicate that the version 7 CH4 and N2O data sets can be used with good confidence for quantitative and qualitative studies of stratospheric and lower‐mesospheric atmospheric structure and dynamics.

The cryogenic limb array etalon spectrometer (CLAES) aboard UARS made near‐global measurements of HNO 3 and 388 days from January 9, 1992, to April 25, 1993, have been processed to data version 7 (V7). Results from UARS instruments, including CLAES, the improved stratospheric and mesospheric sounder, and the microwave limb sounder, provide the first near‐global documentation of the evolution of denitrification in the Antarctic 1992 winter and spring vortex. We provide a description of the CLAES HNO 3 V7 quality that includes comparisons with correlative measurements to assess overall quality, accuracy, and precision. Correlative profiles of volume mixing ratio (vmr) included those obtained by the space shuttle deployed ATMOS in two missions, March–April 1992 and April 1993, data from a variety of balloon‐borne instruments at midlatitude (11 profiles), and in high‐latitude northern winter (six profiles), and LIMS data. In general, the CLAES V7 HNO 3 maximum values of vmr were of the order of 6–15% less than correlative for CLAES values ≤8 parts per billion by volume (ppbv). However, when CLAES peak vmr values were 10 to 13 ppbv, then CLAES values exceeded correlative by 0–7%. The comparisons were within the combined instrumental error estimates, or observed measurement variability, for the large majority of comparisons. As discussed, the retrieval of future versions will utilize updated spectral parameters and will also correct for a small uncompensated drift in radiometric calibration that occurred in the latter part of the mission. This is expected to improve the comparisons in the ≤8 ppbv range, perhaps at the expense of those in the ≥8 ppbv range. The data obtained January 9 to April 15, 1992, in comparison with data obtained January 9 to April 15, 1993, reveal strikingly evident 1‐year period deseasonalized trends on a global basis. These trends agree quantitatively with available correlative data suitable for trend analysis. These include ATMOS in the southern midlatitudes and published long‐term time series of HNO 3 column obtained at 45°S and 20°N. These trends reveal a large decrease in the southern hemisphere and small increases in the northern hemisphere, such that the global average is toward a decrease. The global average decrease we attribute to the diminishing influence of heterogeneous conversion of N 2 O 5 to HNO 3 as the Pinatubo aerosol settles out during this time period, and the HNO 3 recovers toward pre‐Pinatubo conditions. We establish plausibility that the small increases in the north are due to hemispherically asymmetric QBO‐like effects that are strong in the northern hemisphere and weak in the southern hemisphere and are phased to produce an increase in HNO 3 over the 1‐year time period of just the right magnitude to more than offset decrease due to settling out of the Pinatubo aerosol. Based on this study, our range of confidence in the CLAES HNO 3 V7 product is from 70 to 3 mbar, in comparison with correlative data, and the precision on this range is of the order of 0.3–1.0 ppbv. This precision was derived from data repeatability and agrees within a factor of 2 or better with estimates based on instrument characterization and with error estimates embedded within the V7 data.

Validation studies of multiwavelength Cryogenic Limb Array Etalon Spectrometer (CLAES) observations of stratospheric aerosol are discussed. An error analysis of the CLAES aerosol extinction data is presented. Aerosol extinction precision values are estimated at latitudes and times at which consecutive Upper Atmosphere Research Satellite (UARS) orbits overlap. Comparisons of CLAES aerosol data with theoretical Mie calculations, based upon in situ particle size measurements at Laramie, Wyoming, are presented. CLAES aerosol data are also compared to scaled aerosol extinction measured by the Stratospheric Aerosol and Gas Experiment (SAGE II) and Atmospheric Trace Molecule Spectroscopy (ATMOS) experiments. Observed and calculated extinction spectra, from CLAES, Improved Stratospheric and Mesospheric Sounder (ISAMS), and Halogen Occultation Experiment (HALOE) data, are compared. CLAES extinction data have precisions between 10 and 25%, instrumental biases near 30%, and accuracies between 33 and 43%.

The cryogenic limb array etalon spectrometer (CLAES) aboard the Upper Atmosphere Research Satellite has made extensive measurements of thermal infrared radiation from the Earth's limb from which vertical concentration profiles of several stratospheric gases and multiwavelength aerosol absorption coefficients have been retrieved for the period from January 9, 1992, to May 5, 1993. This work examines stratospheric ClONO2 concentrations from the current calibration and retrieval software which are designated version 7 data. These data provide the first near‐global view of this stratospheric species. This work evaluates data quality through (1) an analysis of estimated uncertainties and biases in the remote sensing process, (2) comparison with calculations using a two‐dimensional chemical model, (3) comparison with correlative data, and (4) an examination of various known limitations. The precision of CLAES ClONO2 volume mixing ratio retrievals are within 15% in the range (10 < P < 50 mbar). The upper limit on estimated systematic error is 28% in the range (10 < P < 100 mbar) based on studies of error sources in midlatitude retrievals. The global distribution of ClONO2 computed with the Lawrence Livermore National Laboratory two‐dimensional stratospheric chemistry model and the CLAES measurements agree qualitatively. However, above the profile peak the calculated concentration frequently exceeds the measurement. CLAES and ATMOS measurements show relatively good midlatitude agreement, suggesting that the major source of discrepancy is in the model. A possible explanation in terms of a missing reaction ClO + OH → HCl + O2 is suggested. Also, the ClONO2 diurnal cycle constructed from more than 30 days of CLAES data agrees well with the model. The CLAES ClONO2 data diifer from correlative data acquired on flights of the shuttle‐based ATMOS and balloon‐borne instruments by less than 25% on the average in the 10 < P < 50 mbar range. At altitudes above 10 mbar the CLAES measurement is biased low with respect to correlative measurements. This discrepancy at high altitudes is consistent with the analysis showing a large increase of systematic errors above 10 mbar. Heavy tropical volcanic aerosol from the Mount Pinatubo eruption in June 1991 apparently interfered with ClONO2 retrievals in the period before July 1992, causing anomalous peaks in the 20 < P < 30 mbar region accompanied by very small concentrations below the peak (P > 30 mbar). A similar effect associated with thick polar stratospheric clouds is identified. Overall, this validation study indicates that the majority of these data are of good quality and should be very useful in quantitative and qualitative chemical studies of the stratosphere.

The Cryogenic Limb Array Etalon Spectrometer (CLAES) measured emission from the 792 cm−1 Q branch of CO2, from which temperature distributions in the stratosphere and low mesosphere were derived. Here we briefly review the measurement technique, concentrating on aspects that affect the temperature determination. Comparison of many pairs of retrievals at the same location (near 32°N or 32°S) measured on sequential orbits (time separation of 96 min) shows a precision ranging 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‐period spacecraft motions. Comparisons of globally analyzed CLAES data with National Meteorological Center (NMC) and U.K. Meteorological Office (UKMO) analyses show general agreement, with CLAES tending to be cooler by about 2 K, except in the tropics and high‐latitude winter conditions. This is supported by comparisons with individual radiosondes and several lidars that indicate that the agreement is within 2 K throughout the profile (except for a narrow layer around 3 mbar). An error analysis also indicates that systematic errors should be roughly 2 K, independent of altitude. The systematic differences at low latitudes appear to be due to tropical waves, which have vertical wavelengths too short to be seen by the TIROS Operational Vertical Sounder (TOVS) instruments. There are no correlative rocketsondes or lidars to help resolve the reasons for the high‐latitude differences. Comparisons with other Upper Atmosphere Research Satellite (UARS) data should shed additional light on this question.

Ozone measurements made by the Cryogenic Limb Array Etalon Spectrometer (CLAES) aboard the NASA Upper Atmosphere Research Satellite (UARS) are compared to nearly coincident correlative measurements taken in 1992 and 1993 and to mean ozone distributions observed by other satellite instruments during past missions. This paper describes the CLAES measurement characteristics, uncertainties, predicted, and observed precisions and compares the observations with independent measurements both qualitatively and statistically. Satellite‐ and ground‐based remote sensing as well as balloon‐borne in situ measurements are represented in the correlative data set. The CLAES data are shown to be within ±20% of all correlative measurements between 0.5 and 30 mbar. Differences at lower altitudes may be related to effects of the Pinatubo aerosol on certain of the correlative measurements and the CLAES retrieval. Comparisons with historical data from the LIMS, SAGE II, and SBUV instruments indicate good agreement with the spatial and seasonal ozone distributions seen by CLAES.

We have developed a retrieval algorithm for deriving the tropospheric CO profile and column amount from the radiances measured by the Measurements of Pollution In The Troposphere (MOPITT) instrument. The main components of the algorithm are a fast radiative transfer model, based on the GENLN2 line-by-line model, and a maximum likelihood inversion method. The retrieval a priori information is derived from the results of several aircraft in situ measurements and a three-dimensional chemical transport model.This paper discusses the CO retrieval algorithm with an emphasis on the analysis and characterization of the algorithm. Forward model and retrieval sensitivities, along with the a priori information used in the retrieval are discussed in terms of their orthogonal components. Examples of ensemble retrieval experiments are also included.

The cryogenic limb array etalon spectrometer (CLAES) onboard the Upper Atmosphere Research Satellite (UARS) has obtained the first global measurements of CF 2 Cl 2 over six seasons, for which 388 days have been processed in data version 7 for the period from January 9, 1992, to May 5, 1993. The CLAES measurements provide a near‐global view of this stratospheric species, greatly extending the altitude, latitude, and seasonal coverage of previous measurements. This work evaluates CLAES version 7 data set quality. To arrive at estimates of experimental error, we compared the CLAES CF 2 Cl 2 profiles with all of the available correlative data from balloon and space‐borne sensors, and we looked at the repeatability of multiple profiles in the same location. In addition, we carried out empirical estimates of experimental error based on knowledge of instrument characteristics, and we performed consistency checks using the Lawrence Livermore National Laboratory two‐dimensional (LLNL‐2D) model and the CLAES N 2 O data set. Both the range of mean differences between CLAES and the available correlative data and the empirical estimates of the instrument systematic error indicate a CF 2 Cl 2 profile systematic error of 14% over the range of 18.7 through 32 km and 22% for 33–35 km and 16–18 km. These systematic errors are applicable in the spring through fall seasons for the midlatitude region and all seasons in the tropical region. The CF 2 Cl 2 estimated random errors, which are close to the observed data repeatability, are 32 to 11 pptv between 17 and 32 km and translate to an average 9% in the low to midstratosphere. The altitude range of best confidence for the CF 2 Cl 2 mixing ratio profiles is 18.7 to 32 km (∼68 to 10 mbar), to which we assign an accuracy (root‐sum‐square of systematic and random errors) of ∼17%. In the tropics the profiles from 16 to about 26 km may sometimes be biased low by up to 14% due to a data processing algorithm constraint. The CLAES CF 2 Cl 2 global fields show generally good spatial correlation and exhibit the major morphological and seasonal features seen in other global tracer field data. Overall, the results of this validation exercise indicate that the CLAES version 7 CF 2 Cl 2 data set, within the limitations discussed in the paper, can be used for quantitative and qualitative studies of stratospheric structure and dynamics.

The cryogenic limb etalon array spectrometer (CLAES) aboard the Upper Atmosphere Research Satellite (UARS) has made near‐global measurements of N2O5. Data for 388 days have been processed to version 7 (V7) for the period from January 9, 1992, to April 25, 1993. Results from UARS instruments, including CLAES and the improved stratospheric and mesospheric sounder (ISAMS) provide the first near‐global N2O5 measurements. Retrieval below 3.16 mbar is adversely affected by aerosols and above 1.47 mbar by lack of signal and possible instrument effects, so data usage is recommended for just the three “UARS pressure surfaces” 3.16, 2.15, and 1.47 mbar. A comparison of the diurnal data variation with the model suggests there are offsets in the data that are to first order diurnally independent. These offsets are tabulated to facilitate subtraction, which is recommended for most data applications. Candidate mechanisms for the offsets are discussed. Comparisons of CLAES data with the offsets subtracted, with profiles obtained by the shuttle‐deployed Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment and concurrent ISAMS profiles, and with a profile obtained by the balloon‐borne NASA Jet Propulsion Laboratory (JPL) MARK IV instrument, show poorest agreement in equatorial regions at 3.15 mbar where CLAES values are larger by about 30 to 40%. At higher altitudes and latitudes the comparison improves and tends toward consistency with systematic error estimates that are based on instrument and retrieval process characterization and range from 14% at 3.16 mbar to 21% at 1.47 mbar. A similar estimate of random CLAES error ranges from 7% at 3.16 mbar to 26% at 1.47 mbar. By comparison, the average values of the error estimates generated by the production processing algorithm at 3.16 and 1.47 mbar are 8 and 36%, respectively, and the average values derived from the observed data variability are 19 and 24%. Confidence is enhanced by the good global scale agreement and correlation of CLAES and ISAMS during an N2O5 enhancement event in early–mid‐January 1992 polar winter, in which values >5.5 parts per billion at 3.16 mbar by volume are observed. A description of artifacts that may occur at 3.16 mbar and much less frequently at 2.15 mbar, during this and other enhancement conditions, and the demonstrated approach to eliminate these in future versions, is given in the text.

CH 4 and N20 are useful as dynamical tracers of stratospheric air transport because of their long photochemical lifetimes over a wide range of altitudes. The cryogenic limb array etalon spectrometer (CLAES) instrument on the NASA UARS provided simultaneous global measurements of the altitude profiles of CH 4 and N20 mixing ratios in the stratosphere between October 1, 1991, and May 5, 1993. Data between January 9, 1992, and May 5, 1993 (388 days), have been processed using version 7 data processing software, and this paper is concerned with the assessment of the quality of this data set. CLAES is a limb-viewing emission instrument, and approximately 1200 profiles were obtained each 24-hour period for each constituent over a nominal altitude range of 100 to 0.1 mbar (16 to 64 km). Each latitude was sampled 30 times per day between latitudes 34øS and 80øN, or 34øN and 80øS depending on the yaw direction of the UARS, and nearly all local times were sampled in about 36 days. This data set extends the altitude, latitude, and seasonal coverage of previous experiments, particularly in relation to measurements at high winter latitudes. To arrive at estimates of experiment error, we compared CLAES profiles for both gases with a wide variety of correlative data from ground-based, rocket, aircraft, balloon, and space-borne sensors, looked at the repeatability of multiple profiles in the same location, and carried out empirical estimates of experiment error based on knowledge of instrument characteristics. These analyses indicate an average single-profile CH 4 systematic error of about 15% between 46 and 0.46 mbar, with CLAES biased high. The CH 4 random error over this range is 0.08 to 0.05 parts per million, which translates to about 7% in the midstratosphere. For N20 the indicated systematic error is less than 15% at all altitudes between 68 and 2 mbar, with CLAES tending to be high below 6.8 mbar and low above. The N20 random error is 20 to 5 ppb between 46 and 2 mbar, which also translates to 7% in the low to midstratosphere. Both tracers have useful profile information to as low as 68 mbar, excluding the tropics, and as high as 0.2 mbar (CH4) and 1 mbar (N20). The global fields show generally good spatial correlation and exhibit the major morphological and seasonal features seen in previous global field data. Several morphological features are pointed out for regions and conditions for which there have been essentially no previous data. These include the differential behavior of the tracer isopleths near and inside the Antarctic winter vortex, and local maxima in the tropics in 1992, probably associated with the Mount Pinatubo sulfate aerosol layer. Overall, the results of this validation exercise indicate that the version 7 CH 4 and N20 data sets can be used with good confidence for quantitative and qualitative studies of stratospheric and lower-mesospheric atmospheric structure and dynamics.

The Measurement of Pollution In The Troposphere (MOPITT) instrument is designed to measure CO and CH/sub 4/ in the troposphere from a satellite platform. This instrument has been selected to be on the Earth Observing System (EOS)'s AM platform, which is scheduled to be launched in 1998. The authors present the development of retrieval algorithms and the simulation experiments performed to evaluate the algorithms and to understand certain measurement issues. The MOPITT instrument is a gas correlation spectrometer. It makes measurements in three spectral regions. The objective is to measure the CO vertical distribution from O to 15 km within 10% accuracy and the CH/sub 4/ column amount within 1% accuracy. There are four radiometers making measurements in the thermal band at 4.7 /spl mu/m, which will be used to obtain profile information about the tropospheric CO distribution. Two short-wave solar reflectance channels will be used at 2.3 and 2.2 /spl mu/m to measure total column amounts of CO and CH,, respectively.<>

Multiwavelength observations of Antarctic and midlatitude aerosol by the Cryogenic Limb Array Etalon Spectrometer (CLAES) experiment on the Upper Atmosphere Research Satellite are used to demonstrate a technique that identifies the location of polar stratospheric clouds. The technique discussed uses the normalized area of the triangle formed by the aerosol extinctions at 925, 1257, and 1605 cm-1 (10.8, 8.0, and 6.2 mum) to derive a spectral aerosol measure M of the aerosol spectrum. Mie calculations for spherical particles and T-matrix calculations for spheroidal particles are used to generate theoretical spectral extinction curves for sulfate and polar stratospheric cloud particles. The values of the spectral aerosol measure M for the sulfate and polar stratospheric cloud particles are shown to be different. Aerosol extinction data, corresponding to temperatures between 180 and 220 K at a pressure of 46 hPa (near 21-km altitude) for 18 August 1992, are used to demonstrate the technique. Thermodynamic calculations, based upon frost-point calculations and laboratory phase-equilibrium studies of nitric acid trihydrate, are used to predict the location of nitric acid trihydrate cloud particles.