Cheryl Craig

Global estimates of gravity wave momentum flux from High Resolution Dynamics Limb Sounder observations

analyzed to derive global properties of gravity waves. We describe a wavelet analysis technique that determines covarying wave temperature amplitude in adjacent temperature profile pairs, the wave vertical wavelength as a function of height, and the horizontal wave number along the line joining each profile pair. The analysis allows a local estimate of the magnitude of gravity wave momentum flux as a function of geographic location and height on a daily basis. We examine global distributions of these gravity wave properties in the monthly mean and on an individual day, and we also show sample instantaneous wave events observed by HIRDLS. The results are discussed in terms of previous satellite and radiosonde observational analyses and middle atmosphere general circulation model studies that parameterize gravity wave effects on the mean flow. The high vertical and horizontal resolution afforded by the HIRDLS measurements allows the analysis of a wider range of wave vertical and horizontal wavelengths than previous studies and begins to show individual wave events associated with mountains and convection in high detail. Mountain wave observations show clear propagation to altitudes in the mesosphere.

Higher-Order Turbulence Closure and Its Impact on Climate Simulations in the Community Atmosphere Model

AbstractThis paper describes climate simulations of the Community Atmosphere Model, version 5 (CAM5), coupled with a higher-order turbulence closure known as Cloud Layers Unified by Binormals (CLUBB). CLUBB is a unified parameterization of the planetary boundary layer (PBL) and shallow convection that is centered around a trivariate probability density function (PDF) and replaces the conventional PBL, shallow convection, and cloud macrophysics schemes in CAM5. CAM–CLUBB improves many aspects of the base state climate compared to CAM5. Chief among them is the transition of stratocumulus to trade wind cumulus regions in the subtropical oceans. In these regions, CAM–CLUBB provides a much more gradual transition that is in better agreement with observational analysis compared to CAM5, which is too abrupt. The improvement seen in CAM–CLUBB can be largely attributed to the gradual evolution of the simulated turbulence, which is in part a result of the unified nature of the parameterization, and to the general i...

Validation studies using multiwavelength Cryogenic Limb Array Etalon Spectrometer (CLAES) observations of stratospheric aerosol

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%.

Revised reference model for nitric acid

Abstract A nearly global set of data on the nitric acid distribution was obtained for seven months by the Limb Infrared Monitor of the Stratosphere (LIMS) experiment on the Nimbus 7 spacecraft. The evaluation of the accuracy, precision and resolution of these data is described, and a description of the major features of the nitric acid distributions is presented. The sonal mean for nitric acid is distributed in a stratospheric layer that peaks near 30 mb, with the largest mixing ratios occurring in polar regions, especially in winter.

Initial validation of ozone measurements from the High Resolution Dynamics Limb Sounder

Comparisons of the latest High Resolution Dynamics Limb Sounder (HIRDLS) ozone retrievals (v2.04.09) are made with ozonesondes, ground-based lidars, airborne lidar measurements made during the Intercontinental Chemical Transport Experiment–B, and satellite observations. A large visual obstruction blocking over 80% of the HIRDLS field of view presents significant challenges to the data analysis methods and implementation, to the extent that the radiative properties of the obstruction must be accurately characterized in order to adequately correct measured radiances. The radiance correction algorithms updated as of August 2007 are used in the HIRDLS v2.04.09 data presented here. Comparisons indicate that HIRDLS ozone is recoverable between 1 and 100 hPa at middle and high latitudes and between 1 and 50 hPa at low latitudes. Accuracy of better than 10% is indicated between 1 and 30 hPa (HIRDLS generally low) by the majority of the comparisons with coincident measurements, and 5% is indicated between 2 and 10 hPa when compared with some lidars. Between 50 and 100 hPa, at middle and high latitudes, accuracy is 10–20%. The ozone precision is estimated to be generally 5–10% between 1 and 50 hPa. Comparisons with ozonesondes and lidars give strong indication that HIRDLS is capable of resolving fine vertical ozone features (1–2 km) in the region between 1 and 50 hPa. Development is continuing on the radiance correction and the cloud detection and filtering algorithms, and it is hoped that it will be possible to achieve a further reduction in the systematic bias and an increase in the measurement range downward to lower heights (at pressures greater than 50–100 hPa).

Overview and characterization of retrievals of temperature, pressure, and atmospheric constituents from the High Resolution Dynamics Limb Sounder (HIRDLS) measurements

Received 18 February 2009; revised 22 April 2009; accepted 26 June 2009; published 23 October 2009. [1] The retrieval algorithm for the High Resolution Dynamics Limb Sounder (HIRDLS) instrument onboard NASA’s Earth Observing System (EOS) Aura satellite is presented. The algorithm is based on optimal estimation theory, using a modified Levenberg-Marquardt approach for the iterative solution. Overview of the retrieval scheme, convergence criteria, and the forward models is given. Treatments of clouds and aerosols as well as line-of-sight gradients in temperature are described. The retrievals are characterized by high vertical resolution of 1 km and negligible a priori contribution for all products in regions of high signal-to-noise ratio (SNR) (most of the retrieval ranges). It is shown that these characteristics hold for all latitudes along a HIRDLS orbit. The weighting functions are narrow and show good sensitivity to temperature or gas perturbations in regions of high SNR. The retrieval error predicted by the algorithm consists of radiometric noise, pointing jitter error, smoothing error, and forward model error. For temperature, these components are shown for a midlatitude profile as well as for a full orbit. The predicted temperature error varies from 0.5 K to 0.8 K from the upper troposphere to the stratopause region, consistent with the empirical estimates given by Gille et al. (2008). For O3 and HNO3, the predicted errors and their useful pressure ranges are, respectively, 10–5% from 50 to 1 hPa and 5–10% from 100 to 10 hPa. These results are based on version V004 of the retrieved data, released in August 2008 to the Goddard Earth Sciences Data and Information Services Center (http://daac.gsfc.nasa.gov).

Development of special corrective processing of HIRDLS data, and early validation

The High Resolution Dynamics Limb Sounder (HIRDLS) instrument was launched on NASAs Aura spacecraft on 15 July 2004. When activation was completed 25 days later, it was discovered that the measured radiances were very different from those that were expected. After a long series of analyses and diagnostic tests, the cause was confirmed to be a blockage that covers much of the front aperture, preventing even one completely clear view of the atmosphere. In this paper the steps required to correct the radiances for the effects of the blockage are noted. These are calibrating the radiances, removing the effects of the blockage oscillating, and the radiance coming from the blockage, correcting for the effects of the partial aperture, and filtering the noise. The paper describes the algorithms needed, and presents the results of their application. The success of the procedures will be demonstrated by the quality of the resulting radiances and retrieved profiles of temperature and trace species. The difficulties that have been eliminated, and that still remain are noted, along with plans for further improvement. Finally, the scientific implications are briefly discussed.