Halogen Occultation Experiment Instrument Research Articles

Classification of Northern Hemisphere stratospheric ozone and water vapor profiles by meteorological regime

Abstract. The subtropical and polar upper troposphere fronts and the polar vortex serve as the boundaries to divide the Northern Hemisphere into four meteorological regimes. These regimes are defined as (1) the arctic regime – within the polar vortex, (2) the polar regime – between the polar front and the polar vortex, or when the latter is not present, the pole, (3) the midlatitude regime – between the subtropical and polar fronts, and (4) the tropical regime – between the equator and the subtropical front. Data from the Halogen Occultation Experiment (HALOE) and the Stratospheric Aerosol and Gas Experiment II (SAGE II) were used to show that within each meteorological regime, ozone and water profiles are characterized by unique ozonepause and hygropause heights. Daily measurements and seven-year (1997–2003) monthly climatologies showed that, within each meteorological regime, both constituents exhibited distinct profile shapes from the tropopause up to approximately 20 km. This distinction was most pronounced in the winter and spring months, and weak in the summer and fall. Despite differences in retrieval techniques and sampling between the SAGE and HALOE instruments, the seven-year monthly climatologies calculated for each regime agreed well for both species below ~22 km. Given that profiles of ozone and water vapor exhibit unique profiles shapes within each regime in the UTLS, trends in this region will therefore be the result of both changes within each meteorological regime, and changes in the relative contribution of each regime to a given zonal band over time.

Near‐real‐time approach to assimilation of satellite‐retrieved 3D ozone fields in a global model using a simplified Kalman filter

AbstractIn this paper, a near‐real‐time approach to data assimilation for the estimation of the three‐dimensional global ozone distribution based on the transport model TM3 is presented. TM3 uses the meteorological data from European Centre for Medium‐Range Weather Forecasts to transport the ozone field. The ozone profiles used in the assimilation are retrieved from measurements of the Global Ozone Monitoring Experiment instrument (GOME) on the European Space Agency's European Remote Sensing‐2 satellite. A simplified Kalman filter technique is chosen as a data assimilation technique since it not only estimates the ozone distribution globally but also quantifies the uncertainty in its estimate. The NRT data assimilation technique is demonstrated for the period of March–June 2000. The results presented in this paper show that the estimated profiles deviate from the measurements by, on a global average, 15% of the ozone values in pressure layer 163–119 hPa and ranging from 6% to 2% of the ozone values between 119 hPa and 40 hPa. The deviation of the estimate from the measurements decreases with altitude and reaches 0.05% of the ozone value in the layer 2–0 hPa. Comparison with ozone‐sonde observations shows that the model driven by observed meteorological fields is capable of describing the main spatial and temporal variations. Comparison with data from the Halogen Occultation Experiment instrument on the Upper Atmosphere Research Satellite shows that assimilating the retrieved profiles from GOME improves the vertical description of ozone profiles mainly in the stratosphere and the upper troposphere. Moreover, the integrated ozone‐profile estimate is compared with the total‐column ozone measurements made by the Total Ozone Mapping Spectrometer. This shows that assimilating the ozone profiles results in a better description of the total column than the ten‐day forecast. Copyright © 2003 Royal Meteorological Society

Near-real-time approach to assimilation of satellite-retrieved 3D ozone fields in a global model using a simplified Kalman filter

In this paper, a near-real-time approach to data assimilation for the estimation of the three-dimensional global ozone distribution based on the transport model TM3 is presented. TM3 uses the meteorological data from European Centre for Medium-Range Weather Forecasts to transport the ozone field. The ozone profiles used in the assimilation are retrieved from measurements of the Global Ozone Monitoring Experiment instrument (GOME) on the European Space Agency's European Remote Sensing-2 satellite. A simplified Kalman filter technique is chosen as a data assimilation technique since it not only estimates the ozone distribution globally but also quantifies the uncertainty in its estimate. The NRT data assimilation technique is demonstrated for the period of March–June 2000. The results presented in this paper show that the estimated profiles deviate from the measurements by, on a global average, 15% of the ozone values in pressure layer 163–119 hPa and ranging from 6% to 2% of the ozone values between 119 hPa and 40 hPa. The deviation of the estimate from the measurements decreases with altitude and reaches 0.05% of the ozone value in the layer 2–0 hPa. Comparison with ozone-sonde observations shows that the model driven by observed meteorological fields is capable of describing the main spatial and temporal variations. Comparison with data from the Halogen Occultation Experiment instrument on the Upper Atmosphere Research Satellite shows that assimilating the retrieved profiles from GOME improves the vertical description of ozone profiles mainly in the stratosphere and the upper troposphere. Moreover, the integrated ozone-profile estimate is compared with the total-column ozone measurements made by the Total Ozone Mapping Spectrometer. This shows that assimilating the ozone profiles results in a better description of the total column than the ten-day forecast. Copyright © 2003 Royal Meteorological Society

Solar cycle variation of nitric oxide in the thermosphere

The measurements of trace gases in the atmosphere made by the Halogen Occultation Experiment instrument on UARS have been used to investigate the solar cycle variation of nitric oxide. The data covers the period from near solar activity maximum in late 1991 to its near minimum in late 1996. Systematic errors in the NO measurements were corrected, and the results were correlated with the F10.7 index. Regression coefficients derived from this analysis are presented. It is found that nitric oxide in the equatorial thermosphere varies significantly with F10.7, but its variation in polar thermosphere is very small.

Interannual Variability of Trace Gases in the Subtropical Winter Stratosphere

Abstract Measurements of water vapor and methane from the Halogen Occultation Experiment instrument on board the Upper Atmosphere Research Satellite are used to study the interannual variability of trace gas distributions in the atmosphere. Particular attention is paid to the mechanisms influencing trace gas distributions in the subtropics. The study highlights the quasi-biennial oscillation (QBO) dependence of subtropical tracer distributions more clearly than in previous studies. There is a strong correlation between the equatorial wind QBO and the slope of the tracer isolines in the Northern Hemisphere subtropics, with steeper subtropical isoline slopes in the easterly phase compared with the westerly phase. This is particularly so in the lower stratosphere. Two possible mechanisms for the QBO signal in subtropical isoline slopes are identified: advection by the mean circulation and isentropic mixing. A comparison between the QBO signal in the slope of the tracer isolines and the isentropic tracer grad...

Aerosol effects and corrections in the Halogen Occultation Experiment

The eruptions of Mt. Pinatubo in June 1991 increased stratospheric aerosol loading by a factor of 30, affecting chemistry, radiative transfer, and remote measurements of the stratosphere. The Halogen Occultation Experiment instrument on board UARS makes measurements globally for inferring profiles of NO2, H2O, O3, HF, HCl, CH4, NO, and temperature in addition to aerosol extinction at five wavelengths. Understanding and removing the aerosol extinction is essential for obtaining accurate retrievals from the radiometer channels of NO2, H2O and O3 in the lower stratosphere since these measurements are severely affected by contaminant aerosol absorption. If ignored, aerosol absorption in the radiometer measurements is interpreted as additional absorption by the target gas, resulting in anomalously large mixing ratios. To correct the radiometer measurements for aerosol effects, a retrieved aerosol extinction profile is extrapolated to the radiometer wavelengths and then included as continuum attenuation. The sensitivity of the extrapolations to size distribution and composition is small for certain wavelength combinations, reducing the correction uncertainty. The aerosol corrections extend the usable range of profiles retrieved from the radiometer channels to the tropopause with results that agree well with correlative measurements. In situations of heavy aerosol loading, errors due to aerosol in the retrieved mixing ratios are reduced to values of about 15, 25, and 60% in H2O, O3, and NO2, respectively, levels that are much less than the correction magnitude.

Application Of The Langley Plot For Calibration Of Sun Sensors For The Halogen Occultation Experiment (Haloe)

The calibration of the Halogen Occultation Experiment (HALOE) sun sensor is described. This system consists of two energy-balancing silicon detectors which provide coarse azimuth and elevation control signals and a silicon photodiode array which provides top and bottom solar edge data for fine elevation control. All three detectors were calibrated on a mountaintop near Tucson, Ariz., using the Langley plot technique. The conventional Langley plot technique was modified to allow calibration of the two coarse detectors, which operate wideband. A brief description of the test setup is given. The HALOE instrument is a gas correlation radiometer that is now being developed for the Upper Atmospheric Research Satellite.