A32C-01
Scientific Accomplishments from Ten Years of SHADOZ (Southern Hemisphere Additional Ozonesondes) Profile Data: An Overview
Strategically designed ozonesonde networks (e.g. SHADOZ, MATCH, IONS) have revolutionized ozone sampling in the troposphere and stratosphere, providing mechanistic information and data for trends not accessible by other measurement methods. The SHADOZ network has collected more than 3500 ozone and P-T-U profiles at 15 tropical and subtropical stations since 1998 [Thompson et al., 2003a; 2007]. SHADOZ has added greatly to our knowledge about variability and trends at individual stations and provided new views of the equatorial wave- one in tropospheric ozone, Brewer-Dobson circulation, the quasi-biennial oscillation in temperature and ozone, convective impacts on ozone and processes within the so-called Tropical Tropopause Layer. SHADOZ is invaluable for evaluation of satellite data and ozone distributions computed from chemical-transport and assimilation models. An important contribution of SHADOZ to global observations and trends is improved accuracy and precision of the ozonesonde measurement derived from participation of SHADOZ Co-investigators in intercomparison activities of the World Meteorological Organization. This paper will review these SHADOZ highlights. http://croc.gsfc.nasa.gov/shadoz
A32C-02 INVITED
Seasonal to decadal variability of tropical UTLS ozone observed with SHADOZ
The SHADOZ program is providing a novel observational record of ozone variability in the tropical UTLS region, spanning time scales of days to (nearly) a decade. We highlight low-frequency variability in the SHADOZ observations, including the seasonal cycle, quasi-biennial oscillation (QBO) and longer-term fluctuations, and show comparisons with satellite ozone observations. We analyze the detailed vertical structure of tropical ozone variability, and the coherence between ozone and temperature measurements (also from SHADOZ). The correlated variations in ozone and temperature can be used to infer the behavior of tropical upwelling in the UTLS region.
A32C-03
Trend Analysis of Tropical Ozone From the Southern Hemisphere Additional Ozonesondes (SHADOZ) Data
Linear trends of ozone for 1998-2007 are estimated for the troposphere through the lower stratosphere at ten tropical ozonesonde stations participating in the Southern Hemisphere Additional Ozonesondes (SHADOZ) project. Most stations cover the period from early 1998 to the end of 2006, but some stations have a shorter or longer record. Soundings are made once to four times per month, varying for station and year, but cover basically all seasons. The total sounding number ranges from 102 for Malindi to 429 for Ascension Island. Trends are calculated for vertically averaged values in each 1-km bin from 0-1 km to 30-31 km, and expressed as percent per year. Statistical test is also made. Around the tropopause, between 15 and 20 km, negative trends are seen for most stations. At San Cristobal (in the eastern Pacific) at 16-17 km, the trend is -4.3 ± 3.0 percent per year, and at Watukosek (in Indonesia) at 17-18 km, it is -4.8 ± 3.9 percent per year, both statistically significant. However, at Ascension (in the Atlantic) and at Natal (in South America), the tropopause trend is near zero and not statistically significant. At Natal at 12-13 km, the trend is +3.7 ± 3.0 percent per year, and at Malindi (in Africa) at 11-12 km, it is +5.0 ± 4.6 percent per year, both statistically significant. Generally in the free troposphere, positive trends are seen, but are statistically not significant for most regions. In the planetary boundary layer, statistically significant positive trends are seen at Kuala Lumpur (in Southeast Asia) and at Fiji (in the southwestern Pacific), and a statistically significant negative trend is seen at Paramaribo (in South America). The trend analysis is also made for four different seasons. Around the tropopause, seasonality in trend is small for all stations. In the upper troposphere, at Fiji and at Samoa, negative trends are seen in SON, but positive trends are seen in DJF.
A32C-04
EOF Analysis of Temperature Anomalies in the Tropics with Radiosonde Data from the SHADOZ Program
A principal component analysis is performed on the vertical temperature and ozone profiles of the Southern Hemisphere Additional Ozonesondes (SHADOZ) soundings (1998-2006). Because the soundings are launched at 5-10 day intervals, the analysis resolves variability at time scales that range from approximately two weeks to eight years. For selected SHADOZ sites, which are distributed throughout the tropics close to the equator, the two most dominant empirical orthogonal functions (EOFs) together represent the Quasi-biennial Oscillation (QBO) in the stratosphere. The third most dominant temperature EOF is found to be closely associated with the El Nino-Southern Oscillation (ENSO). While the principal component (PC) time series of the third EOF is significantly correlated with the Nino3 index, the time series also shows much shorter time scale fluctuations. The vertical scale of the temperature associated with the ENSO is consistent with vertically propagating Kelvin waves. These results indicate that next to the QBO, ENSO has the most ignificant impact on the tropical low stratosphere (LS) temperature signal, and that this LS/ENSO relationship may be realized through vertically propagating Kelvin waves, which have much shorter time scales than ENSO itself. http://croc.gsfc.nasa.gov/shadoz
A32C-05 INVITED
Assimilation of Aura ozone data and comparisons with in situ observations
Ozone data from the Ozone Monitoring Instrument (OMI) and the Microwave Limb Sounder (MLS) onboard EOS Aura satellite were assimilated into the Goddard Earth Observing System Version 4 (GEOS-4) ozone assimilation system. Comparison of assimilated ozone with ozone sonde and MOZAIC data indicate an agreement within 10% in the lower stratosphere, where dynamical processes dominate. Assimilation of OMI and MLS data improves tropospheric column estimates in the Atlantic region, but leads to an overestimation in the tropical Pacific in comparison with SHADOZ sondes. Transport and data biases are considered in order to understand these discrepancies. Comparisons of assimilated tropospheric ozone columns with ozone sonde data reveal root-mean-square (RMS) differences of 2.9 to 7.2 DU, which are typically smaller than the model-sonde RMS differences. Four different definitions of the tropopause using temperature lapse rate, potential vorticity (PV) and isentropic surfaces or ozone isosurfaces are compared with respect to their global impact on the estimated tropospheric ozone column. The largest sensitivity in the tropospheric ozone column is found near the subtropical jet, where the ozone or PV determined tropopause typically lies below the lapse rate tropopause.
A32C-06
Trends and Variability of Mid Latitude Stratospheric Water Vapor Deduced From the Re- evaluated Boulder Balloon Series and HALOE
An updated trend analysis of water vapor in the lower mid latitude stratosphere from the Boulder balloon-borne NOAA frostpoint hygrometer measurements and from the Halogen Occultation Experiment (HALOE) is presented. Two corrections for instrumental bias are applied to homogenize the frostpoint data series, and a quality assessment of all soundings after 1991 is presented. Linear trend estimates based on the corrected data for the period 1980-2000 are up to 40 percent lower than previously reported. Vertically resolved trends and variability are calculated with a multi-regression analysis including the quasi-biennal oscillation and equivalent latitude as explanatory variables. In the range of 380 to 640 K potential temperature (~14 to 25 km), the frostpoint data from 1981 to 2006 show positive linear trends between 0.3±0.3 and 0.7±0.1 percent/yr. The same dataset shows trends between -0.2±0.3 and 1.0 ±0.3 percent/yr for the period 1992 to 2005. HALOE data over the same time period suggest negative trends ranging from -1.1±0.2 to -0.1±0.1 percent/yr. In the lower stratosphere, a rapid drop of water vapor is observed in 2000/2001 with little change since. At higher altitudes, the transition is more gradual, with slowly decreasing concentrations between 2001 and 2007. This pattern is consistent with a change induced by a drop of water concentrations at entry into the stratosphere. Previously noted differences in trends and variability between frostpoint and HALOE remain for the homogenized data. Due to uncertainties in reanalysis temperatures and stratospheric transport combined with uncertainties in observations, no quantitative inference about changes of water entering the stratosphere in the tropics could be made with the mid latitude measurements analyzed here.
A32C-07
Mechanisms for the Acceleration of the Brewer-Dobson Circulation in a Climate Change Scenario
The evolution of the Berwer-Dobson circulation as a result of climate change has been analyzed using the NCAR's Whole Atmosphere Community Climate Model (WACCM3). Two experiments, one with fixed greenhouse gas concentrations from 2000 onwards and the other with concentrations that follow the A1B scenario have been compared for the period 2000-2050. In both experiments, the sea surface temperatures are specified from existing runs of NCAR's coupled atmosphere-ocean model that follow the same scenarios. The comparison shows that the Brewer-Dobson circulation in the tropical lower stratosphere strengthens when the greenhouse gases increase. This acceleration is due to changes in the Eliassen-Palm (EP) flux divergence in the subtropical lower stratosphere. In this work, we will show the waves responsible for the changes in the EP flux divergence and the mechanisms whereby these changes take place.
A32C-08
An analysis of cloud scale vertical motions, upper tropospheric humidity, and cirrus microphysical properties in relation to the large-scale atmospheric state
The importance of upper tropospheric (UT) ice clouds on the Earth's radiation budget and their influence on UT humidity is well known. The inhomogeneous nature of UT clouds can have a significant impact on the mean longwave and shortwave radiative fluxes. Cloud scale motions play a significant role in determining UT relative humidity (and hence cloud initiation) and the inhomogeneous nature of cirrus microphysical properties. Since cloud scale variability is much smaller than global model grid box scales, parameterization of these sub-grid processes are critical to improving predictions of future climate. We will investigate the relationship between cirrus microphysical properties, upper tropospheric water vapor, and vertical motions to understand the link between cloud scale features and the large-scale atmospheric state. Our approach is to combine cloud scale vertical motion derived from radar Doppler velocity measurements, cirrus microphysical properties retrieved using a combined lidar-radar algorithm, thermodynamic radiosonde profiles, and water vapor measurements measured by Raman lidar to evaluate the relationship between cloud scale motions, cloud properties and UT humidity. We will also explore the link between the large-scale atmospheric state (i.e. synoptic features) and UT clouds and water vapor by utilizing a competitive neural network classification scheme. We will analyze cirrus cases compiled over a 2 year period at the Department of Energy's Atmospheric Radiation Measurement Climate Research Facility located at the Southern Great Plains site near Lamont, OK.