A33D-0087 1340h
Determination of macrophysics and microphysics cloud parameters from combination of passive and active radiation measurements during the airborne FRENCH campaign
The airborne FRENCH (Field Radiation Experiment on Natural Cirrus and High-level clouds) campaign has taken place over the Atlantic Ocean and the Mediterranean Sea off the coasts of southern France from the end of September to mid-October in 2001. The flights plans were high enough to acquire measurements above high-level clouds such as cirrus. The aim of this experiment was to acquire simultaneously measurements of various remote sensing instruments (passive and active) in order to describe optical and radiative cloud properties and their link with microphysical properties. This campaign was also an opportunity to analyze combination of radiation instruments before it is exploited in the frame of future space missions such as the Aqua-Train. Some of the instruments on board the aircraft had characteristics similar to those of spaceborne instruments of the Train. The airPOLDER (POLarization and Directionality of the Earth's Reflectances) is similar to PARASOL and measures multidirectional and polarized reflected light in the visible and the near-infrared. The MiniMIR (Middle InfraRed) instrument has spectral channels similar to some of MODIS. Leandre (lidar with polarization capabilities) is very similar to the CALIOP lidar on board the CALIPSO platform and finally, the multichannel thermal infrared radiometer CLIMAT has spectral channels close to those of the IIR radiometer on board CALIPSO. Moreover, we lead our study as part of a new instrumental project of the laboratory, which should be a multidirectional and polarized radiometer with capability of spectral measurements extended up to 2.5 m. Thanks to the diversity of the instruments available during the FRENCH campaign, we compare and combine the different measurements using various methods. As a first step of our analysis, cloud altitude is derived from different techniques. Then we investigate a methodology based on the capability of each instrument, in order to determine the cloud optical thickness as well as to describe the cloud microphysics.
A33D-0088 1340h
Aerosol Extinction Profiles Validation: New Approach.
SAGE II/III measures aerosol extinction in the visible and near-infrared where extinction is dominated by scattering that is more dependent on size and to a lesser extent, on composition. On the other hand, other instruments such as HALOE and ILAS II measures aerosol extinction in the infrared where aerosol extinction is dominated by absorption and is strongly dependent on composition and to a lesser extent on size. In the past, the usual procedure to compare visible and infrared measurements is to convert to a common parameter like surface area density, mass mixing ratio, or a common extinction wavelength. While such comparison produced general agreement during periods of high aerosol loading, it often does not produce similar agreement during periods of low aerosol. In this work, we are using a new and unconventional mean of comparing aerosol profiles measured by different instruments at different wavelength range, by examining the aerosol extinction/absorption wavelength dependence and comparing to theoretically modeled ratios. SAGE II and HALOE long records are used to illustrate this approach for both high and low aerosol loading periods. Comparisons also include using SAGE III and ILAS II aerosol extinction profiles.
A33D-0089 1340h
Validation of ILAS-II Aerosol Extinction Coefficients at 780 nm: Comparison with SAGE II, SAGE III, POAM III, and OPC/LPC measurements
The Improved Limb Atmospheric Spectrometer (ILAS) II, which is the successor to ILAS, was launched on board the Advanced Earth Observing Satellite (ADEOS) II on December 14 in 2002. ILAS-II observed stratospheric aerosol in visible/near-infrared/infrared spectral regions at both of the high latitudes, intermittently from January to March, and continuously from April through October 2003. This study reveals characteristics of aerosol extinction coefficients at 780 nm by estimating repeatability of measurements and making comparisons with other data. The repeatability of ILAS-II aerosol extinction data below 30 km is 5$\sim$30% in the Northern Hemisphere and 5$\sim$40% in the Southern Hemisphere. Aerosol extinction coefficients of ILAS-II agree to those measured by SAGE II within their errors, while ILAS-II shows smaller values by $\sim$20% from 20 to 26 km in the Northern Hemisphere; statistical comparisons between ILAS-II and SAGE III, and ILAS-II and POAM III support the result above, although the discrepancy is larger in these comparisons. The aerosol extinction profile derived from the size distribution obtained with an Optical Particle Counter and Laser Particle Counter (OPC/LPC) balloon sounding over Syowa Station (69 $^\circ$S, 40 $^\circ$E) was compared to ILAS-II and SAGE II extinction profiles which were obtained with 599 km and 414 km distances, respectively. A good agreement was shown among those three profiles except for small discrepancies attributable to fine structures in the OPC/LPC data, while ILAS-II aerosol extinction was smaller than the others from 17 km to 25 km. One of the possible major reason for the discrepancy between ILAS-II and other measurements was considered to be uncertainties in tangent height registration. ILAS-II observed Polar Stratospheric Clouds (PSCs) first in the Southern Hemisphere around May 20 in 2003, and then continuously obtained PSC data through early October. When ILAS-II and POAM III made measurements in close horizontal proximity to each other (within $\sim$50 km), small-scale vertically-layered structures in the PSC extinction coefficient profiles resembles to each other in some occasions, which suggests that both the instruments provide data with enough quality to estimate vertical and horizontal extent of PSC clouds.
A33D-0090 1340h
Aerosol Optical Properties in Southeast Asia and Comparison of MODIS Optical Depth Retrievals to AERONET Measurements
Monitoring of aerosol optical properties at Aerosol Robotic Network (AERONET) sites in 2003 and 2004 at five locations in Thailand and two in Vietnam has contributed to the initial stages of an optical aerosol climatology in the region. During the dry season monsoon of November through April (6 months) the aerosols are primarily anthropogenic in origin, generated by agricultural biomass burning and fossil fuel combustion/ industrial emissions. Monitoring during the entire dry season at one rural site in Thailand suggests a seasonal trend in optical properties, showing decreases in both accumulation mode particle size and also in single scattering albedo as the biomass burning activity peaks late in the season. Validation comparisons of aerosol optical depth (AOD) from MODIS retrievals (on both Terra and Aqua satellites) to AERONET data are presented for four sites. Influences of both aerosol properties assumed in the satellite retrievals and of satellite surface reflectance estimates are observed in these validation comparisons. Additionally, smoke optical properties in Thailand are compared to those at AERONET sites in other major biomass burning regions in tropical southern Africa, South America, and in boreal forest regions and found to be intermediate in absorption between smoke from forest region sites (weak absorption for smoke) to savanna sites in Africa (strong absorption). Aerosol single scattering albedo and size distributions measured in the urban center of Bangkok, Thailand are compared with those measured at other urban sites globally, and found to be strongly absorbing (SSA = 0.90 at 550 nm) in the dry season.
A33D-0091 1340h
Validation of ILAS-II Version 1.4 N$_2$O and CH$_4$ Profiles
The Improved Limb Atmospheric Spectrometer-II (ILAS-II) aboard the Advanced Earth Observing Satellite-II (ADEOS-II) measured the vertical profiles of nitrous oxide (N$_2$O) and methane (CH$_4$) profiles at high latitudes in both hemisphere from January to October 2003. Repeatability as a measure of precision defined by a ratio of the standard deviation to the mean value was calculated for N$_2$O and CH$_4$ profiles for the periods when the atmospheric conditions were stable. The repeatability of N$_2$O and CH$_4$ was found to be less than 10% below 30 km, except the N$_2$O at the altitudes of 25$\sim$30 km in the Southern Hemisphere (10$\sim$17%). To evaluate the ILAS-II version 1.4 N$_2$O and CH$_4$ measurements, these profiles are compared with those obtained by balloon-borne sensors (MIPAS-B and MkIV). In addition, the ILAS-II N$_2$O and CH$_4$ profiles are compared statistically with other satellite data (Odin/SMR for N$_2$O and UARS/HALOE for CH$_4$). The criterion for comparison with SMR and HALOE were (1) distance between observed points at the tangent altitude of 20 km by ILAS-II and by SMR/HALOE is less than 300 km/600 km, respectively, and (2) difference of observation time is less than 12 hours. Results of the comparison with MIPAS-B, MkIV and SMR showed that the ILAS-II N$_2$O mixing ratios were $\sim$20% and $\sim$30% lower than them for mixing ratios larger than 100 ppbv in the Northern Hemisphere and the Southern Hemisphere, respectively. ILAS-II CH$_4$ in the Northern Hemisphere showed a tendency to near exponentially 0 ppmv above 25 km or for mixing ratios smaller than 1 ppmv. The tendency was not shown in the ILAS-II CH$_4$ on the Southern Hemisphere. We are investigating the cause of this difference that was seen in the Northern Hemisphere. While, below 25 km or for mixing ratios larger than 1 ppmv in the Northern Hemisphere, ILAS-II CH$_4$ profiles showed a good agreement within $\pm$10% with two balloon and HALOE profiles. In the Southern Hemisphere, ILAS-II CH$_4$ profiles agreed within -10$\sim$+20% with HALOE profiles below $\sim$40 km. In this presentation, we will show more details of the validation and discuss the results and problems.
A33D-0092 1340h
A Comparison of TOMS & SBUV Version 8 Total Column Ozone Data With Data From Groundstations
Data from the Nimbus-7 and Earth Probe Total Ozone Mapping Spectrometer (TOMS) as well as the Solar Backscatter UltraViolet (SBUV) series of instruments have been reprocessed with a new retrieval algorithm (Version 8), and an updated calibration procedure. These data have been systematically compared to total ozone data from Brewer and Dobson spectrophotometers for many individual ground stations. The comparisons were made as a function of latitude, solar zenith angle, reflectivity and total ozone. Results show that the accuracy of the TOMS retrieval is much improved when aerosols are present in the atmosphere, when snow/ice and sea glint are present, and when ozone in the northern hemisphere is extremely low. The SBUV total ozone values have now been calculated as the sum of the profile values instead of the pair method as in the previous version(s). Comparisons of the column measurements to the ozone measurements from the ground will be shown. TOMS overpass data are derived from the single TOMS best match measurement, almost always located within one degree of the ground station and usually made within an hour of local noon. Nimbus-7 and early EarthProbe TOMS data are well calibrated, however significant changes in the sensitivity of the EarthProbe instrument since 2000 have increased uncertainties in the data despite efforts to minimize them with special calibration methods. The agreement with groundstations are still very good but the data should not be used for trend studies. The SBUV measurements have been interpolated along the orbital track and distance weighted from the groundstation location. The time of the SBUV measurements vary according to the satellite's orbit and some do change significantly over a decadal time scale. Large station-to-station differences suggest the possibility of significant instrument errors at some ground stations.
A33D-0093 1340h
Zenith-sky Total Ozone Column Retrievals in the Ultraviolet
A new algorithm to determine the total column ozone from zenith-sky intensities in the ultraviolet, ZTOZ, has been developed for the Shuttle Solar Backscatter Ultraviolet Spectrometer (SSBUV) instrument at the NASA Goddard Space Flight Center. The algorithm derives total ozone column amounts by comparing a ratio of measured intensities from three wavelengths with the equivalent intensity ratios calculated by radiative transfer. ZTOZ allows retrievals of total ozone at solar zenith angles larger than 70 degrees with far more accuracy than can be provided by conventional direct-sun measurements. This capability is important for validating satellite ozone measurements at high solar zenith angles and high latitudes where the direct-sun retrievals become increasingly less accurate. For the period beginning in October 2001, the differences between the ZTOZ and the collocated GSFC Brewer double monochromator direct-sun total column ozone measurements are within 2% and the precision is 1% or less. The ZTOZ methodology, as well as the influences of the ozone profiles, surface albedo, solar zenith angle, and aerosols on the accuracy of the retrieved total ozone amounts will be presented. The applicability of ZTOZ to existing Dobson and Brewer spectrometers operating in zenith-sky mode will also be discussed.
A33D-0094 1340h
First Tropospheric Water Vapor Measurements at the JPL Table Mountain Facility in Support of AURA Validation
In support for the validation of AURA's water vapor satellite measurements, a new water vapor Raman lidar is being implemented at the Table Mountain Facility (TMF) of the Jet Propulsion Laboratory (JPL) in California. The lidar measurements are complemented with simultaneous, co-located, radiosonde measurements. The lidar system was designed to reach accuracies better than 5% anywhere up to 12 km altitude, and with the capability to measure water vapor mixing ratios as low as 1 ppm near the tropopause and in the lower stratosphere. The system high capabilities, and actual performance were demonstrated from preliminary measurements in 2003. Using the experience of these measurements, the system was dismantled, and then re-built in a fully optimized configuration. Simultaneous lidar and radiosonde measurements will take place on a routine basis (4 to 5 nights per week) starting this fall. More intense measurement periods are planned in connection with TES, MLS and HIRDLS coincident measurements onboard AURA. The first results from these remote ground-based and in-situ measurements will be shown, as well as comparisons with the satellite measurements.
A33D-0095 1340h
Passive Remote Sensing Of Aerosol Fine Mode Fraction: A Comparison With In-Situ Measurements During The ACE-Asia Field Campaign.
The contribution of the aerosol accumulation mode optical depth to the total optical depth ($\eta$) has become more relevant in recent years since it is a parameter that can be retrieved from satellite (MODIS) and sunphotometry (AERONET). $\eta$ has been defined in terms of optical properties and it assumes that the aerosol size distribution in the atmospheric column can be represented by two modes. A necessary method to interpret and validate $\eta$ is the comparison of retrievals with in-situ data. However, these comparisons are difficult due to several factors, for example aircraft in-situ measurements are frequently dominated by a variety of sampling issues. The purpose of this work is to address some of the issues related to the definition and interpretation of $\eta$: 1) How does the retrieved $\eta$ scale with the different ratios derived from the in-situ size distributions? 2) When multiple layers and mixed aerosols are present (such as pollution and dust layers frequently observed during ACE-Asia), is the retrieved $\eta$ characteristic of any particular layer or of all layers? 3) Can $\eta$, a parameter defined from optical properties, be related to a physical property such as total columnar or layer aerosol mass? Specifically, we compare collocated measurements of sun photometer derived $\eta$ and profiles of aerosol size distributions and scattering coefficients measured by the NOAA C-130 aircraft during the ACE-Asia field campaign. Appropriate corrections are applied to in-situ measurements in order to account for sampling drying and unknown index of refraction of the ambient aerosol. Several definitions of in-situ $\eta$ are tested including ratios defined in terms of the aerosol size distribution (ratio of accumulation mode to total surface and volume) as well as the ratio of measured scattering coefficient for particles up to 1 um (aerodynamic diameter) to total scattering. An inversion scheme based on the spectral dependence of the optical depth (O'Neill method) is used to derive $\eta$ from the AATS-6 sunphotometer onboard (bands 380,450,525 and 1020 nm). Initial comparisons indicate that retrieved $\eta$ scales reasonably well with the ratios of accumulation mode to total integrated area and volume. Further comparisons will be shown at the meeting.
A33D-0096 1340h
Ozone Observations over Toronto: A Comparison between a Ground-Based Fourier Transform InfraRed (FTIR) Spectrometer and the Optical Spectrograph and InfraRed Imager System (OSIRIS)
The Toronto Atmospheric Observatory (TAO) was commissioned in 2001, and a newly redesigned Bomem DA8 high resolution Fourier Transform Infrared Spectrometer (FTIR) was installed as its principal instrument. Since 2002, spectra have been recorded routinely with both an InSb and an MCT detector, over a spectral range of 720 to 4300 cm-1 with a nominal resolution of 0.004 cm-1. Using the SFIT2 optimal estimation retrieval algorithm, total and partial column concentrations of O3, N2O, CH4, HF, HCl, NO2, NO, CO, HCN, OCS, and C2H6 over Toronto have been determined. In March 2004, the TAO FTIR was formally designated as a complementary site of the Network for the Detection of Stratospheric Change (NDSC). This presentation will focus on comparing partial column and total column ozone observations made with the TAO-FTS with observed ozone profiles made by the Optical Spectrograph and InfraRed Imager System (OSIRIS) on board the Odin satellite. By employing the formalism of the optimal estimation method, the differing characteristics between the two observing systems are taken into account and the retrieved partial and total ozone columns are recalculated with the effects of smoothing error taken into consideration. Furthermore, by characterizing the information content and degrees of freedom for signal of the TAO-FTIR measurements, the optimal partial column retrievals for comparing measurements are found. The relevant errors and changes in the resulting error patterns are also addressed.
A33D-0097 1340h
Evaluation of Ozonesonde Solution Concentrations Using Dual Ozonesonde Balloon Flights, and Comparison With EP-TOMS Satellite and Dobson Spectrophotometer Total Column Ozone Over McMurdo Station, Antarctica
Balloon-borne ozonesondes are used to measure vertical profiles of ozone concentration from 0 to $\sim$ 35 km. While these instruments have precisions of $\sim$ 5%, there are questions concerning accuracy. The debate centers primarily on the concentration of the potassium-iodide (KI) solution used in the electrochemical concentration cell, and whether it should be buffered with potassium bromide. The recommendations range from 0.5% buffered to 1.0% buffered to 2.0% unbuffered solution. Here, we compare the results of 19 dual ozonesonde flights over McMurdo Station, Antarctica (78$\deg$S) (12 flights with 1.0% and 0.5% buffered KI solution, and 7 flights with 1.0% buffered and 2.0% unbuffered KI solution). Comparisons between vertical ozone profiles show that the 0.5% buffered and the 2.0% unbuffered solutions consistently give lower values of ozone than the 1.0% buffered solution when ozone partial pressure is $\sim>$5mPa. Total column ozone values are calculated from balloon flight measurements and compared with total column ozone measured by the Total Ozone Mapping Spectrometer (TOMS) on NASA's Earth Probe satellite and by a Dobson spectrophotometer operated approximately 1 km from McMurdo station. In seven of the dual flights consisting of 0.5% and 1% buffered solutions and all of the dual flights with 2.0% unbuffered and 1.0% buffered solutions, the 1.0% buffered solution compared better to both TOMS and Dobson spectrophotometer measurements. Of the other 5 flights with 0.5% and 1.0% solutions, four occurred while McMurdo was outside of the polar vortex. In these cases, the 0.5% solution compares better with the TOMS and Dobson spectrophotometer data. While other studies, comparing solution types and strengths in the mid latitudes, have suggested that 0.5% buffered solution gives more accurate total column ozone, the analyses presented here suggest that 1.0% buffered solution measurements compare more favorably to other measures of total ozone in the polar vortex during periods of large ozone depletion.
A33D-0098 1340h
Ground-Based Validation of ACE Measurements of Ozone and NO$_{2}$ in the Canadian Arctic
The Atmospheric Chemistry Experiment (ACE), was successfully launched on August 12, 2003. There are two instruments on board: ACE-FTS, a high resolution infrared Fourier Transform Spectrometer, and MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation), a UV-Visible dual spectrograph. Together, they can measure profiles of ozone, NO$_{2}$, N$_{2}$O, N$_{2}$O$_{5}$, NO, HNO$_{3}$, ClNO$_{3}$, CH$_{4}$, H$_{2}$O, HCl, HF, CO, CFC-11, and CFC-12, as well as temperature and pressure profiles, and aerosol extinction. The goal of the ACE mission is to investigate the chemical and dynamical processes that are involved in the distribution of ozone in the atmosphere, with a focus on the Canadian Arctic. As part of the effort to validate the two instruments, a ground-based validation campaign took place at Eureka, Nunavut (80$^{o}$N, 86$^{o}$W) at Environment Canada's Arctic Stratospheric Observatory (AStrO) from February 18 to April 18 of 2004, coinciding with the most chemically active time of year in the Arctic. Seven instruments were active during the intensive phase of the campaign (February 23 to March 9): a MAESTRO clone, a SunPhotoSpectrometer (SPS), a zenith-viewing UV-visible grating spectrometer, the ACE clone - PARIS (Portable Atmospheric Research Interferometric Spectrometer), a Bomem DA8 Fourier transform spectrometer, a Differential Absorption Lidar (DIAL), and a Brewer spectrophotometer. In addition, daily ozonesondes were released during this intensive phase. We will present comparisons of ozone and NO$_{2}$ vertical columns and, where possible, profiles retrieved using these instruments, with a focus on the period of February 28 to March 5, 2004, when there were particularly good measurement conditions for the ground-based instruments. Comparisons will also be made to coincident measurements made by MAESTRO and ACE-FTS.
A33D-0099 1340h
Comprehensive Intercomparison of SBUV and Umkehr Ozone Data Using TOMRAD Code
The comprehensive intercomparison of SBUV/SBUV2 (Solar Backscatter Ultra-Violet) and Umkehr total and profile ozone data is presented. This paper discusses consistency between the two datasets. The recently updated retrieval algorithms for both systems are verified through the use of radiative transfer code. The SBUV data records from Nimbus-7, NOAA-9, NOAA-11, and NOAA-16 satellites covering period from November 1978 through December 2003 have been reprocessed by NOAA-NASA ozone team using newly-developed Version 8 retrieval algorithm. Umkehr data selected for comparisons include ozone measurements taken at Tateno (Japan), Arosa (Switzerland), and Boulder (USA) Dobson stations. Umkehr retrieval algorithm was recently updated at NOAA/SRRB. We have compared monthly-averaged total column and profile ozone obtained from the set of coincident (within place and time) observations. Using TOMRAD radiative transfer code we have simulated SBUV measurement signal from Umkehr and SBUV coincident profiles to assess compatibility of forward model and inversion algorithms for both instruments. Measurement residuals and their possible causes obtained during these simulations are discussed.
A33D-0100 1340h
Assimilation and Validation of Radiances From the Solar Backscatter UltraViolet (SBUV)/2 Instrument
In operational weather forecasting, the assimilation of brightness temperatures from satellite sounders, instead of assimilation of 1D-retrievals has become increasingly common practice over the last two decades. Assimilation of trace gases is still at a relatively early stage of development, and efforts to directly assimilate radiances instead of retrieved products have just begun a few years ago, partially because it requires much more computation power due to the employment of a radiative transfer forward model. This paper will focus on a method to assimilate SBUV/2 Version~8 radiances (albedos) in order to constrain the global ozone field. Assimilation of retrieved ozone was shown to contribute to monitoring of ozone data from TOMS and SBUV. The radiance assimilation approach provides a more direct access to the measurements and potentially a more direct way of their validation. Furthermore, assimilation can help in understanding the impact of collocation distance on sonde comparisons. The ozone system that was developed at the Global Modeling and Assimilation Office (GMAO) of NASA/Goddard has been successfully used to assimilate ozone data from several satellite instruments: TOMS, SBUV~V6, MIPAS and POAM. We use a recent version of this system, which includes parameterized chemistry in stratosphere and troposphere, and transport within the general circulation model (GCM) that is constrained by GMAO's meteorological analyses. The statistical analysis is implemented using the Physical-space Statistical Analysis Scheme (PSAS). The talk will also discuss methods to deal with the increased computational load of radiance assimilation, and try to assess the error characteristics and future potential of the new approach.
http://gmao.gsfc.nasa.gov/research/ozone/ozone_assim.php
A33D-0101 1340h
An equation for determining ground heat flux according to land skin temperature observations from in-situ stations and satellites
Due to the rapid progress of remote sensing techniques, skin temperature can now be observed with global coverage from satellites. This study derives an equation for utilizing skin temperature measurements to determine ground heat flux. This equation is verified at the FIFE and 4 Ameri Fluxnet sites. A preliminary monthly global data set of ground heat flux with 1 degree resolution, covering the years 1984-1995, is derived based on skin temperature observations obtained via satellite. It shows that the seasonal variation of ground heat flux over land can be determined 1.5 months ahead by observing the increasing rate of skin temperature, and that the variation increases from -O2 W m-2 at the Equator to -O20 W m-2 at the Poles. Over land, the resulting ground heat flux can be compared with that of the ERA15 reanalysis, showing root-mean-square (rms) differences of about 5 W m-2. Over oceans, the flux can be compared with that of the reanalysis only in regions where horizontal advected heat transport and upwelling mechanisms are known to be weak, with rms differences of about 40 W m-2.
A33D-0102 1340h
Validation of Combined SBUV Time Series: Search for Shifts and Biases.
Ground-based and satellite measurements are among the few observing systems that provide long-term data for ozone trend analysis and detection of the first signs of recovery. Although satellite instruments offer wide spatial coverage of ozone profile changes, they often have shorter lifetimes than their ground-based counterparts. To use satellite data for trend analysis, several data records must be combined into a long-term time series, with careful validation required to ensure consistency. This analysis represents the first comparison of upper-stratosphere ozone information observed by two independent systems: the Solar Backscatter UltraViolet (BUV and SBUV/2) instruments on board several NASA and NOAA satellites, and ground-based Dobson spectrophotometer. Trend analyses of the ozone time series from the SBUV/SBUV2 data set are complex because of the multiple instruments involved, changes in the instruments' geo-location, and short time overlaps for inter-calibrations among different instruments. Umkehr Dobson time series are therefore used to validate combined SBUV/SBUV2 dataset at several atmospheric levels. Both the new SBUV Version 8 and the new UMK 2004 profile retrieval algorithms were designed with the goal of studying long-term variability and trends in ozone by optimizing the inter-annual variability of their a priori profiles. Furthermore, all UMK04 profiles had been assessed for stratospheric aerosol errors, which are related not only to aerosol optical depth, but also to the height of aerosol maximum load over the ground-based station. We use over-pass SBUV data to confirm aerosol corrections in Dobson time series. The SBUV time series from 1979 to 2003 were analyzed over three Umkehr stations (Arosa, Boulder, and Tateno) in the northern middle latitudes (35°N- 50°N). Generally, both data sets agree well, particularly in layers 6 - 8 (28 km - 43 km), and differences between the satellite and ground-based data do not suggest any significant time-dependent shifts or trends.
http://www.srrb.noaa.gov/research/umkehr
A33D-0103 1340h
Improved A Priori for Tropospheric CO Based on Satellite and In-situ Data Analysis
The Measurements of Pollution in the Troposphere (MOPITT) satellite instrument has now produced more than four years of global measurements of tropospheric CO. These data form the basis of a new a priori for tropospheric CO. However, quantitative interpretations of MOPITT retrieved CO profiles must account for the role played by a priori information; current MOPITT retrieved profiles are based on an optimal estimation retrieval algorithm with a fixed (global) a priori profile. Thus, deriving the new a priori directly from the current MOPITT product would necessarily result in regional and seasonal biases. For example, in much of the southern hemisphere, where CO volume mixing ratios are usually much smaller than values in the global a priori profile, MOPITT retrievals are typically positively biased. A revised ``dynamic'' CO a priori without the regional and seasonal biases described above is under development. The key constraint in this development is that, within each a priori domain (defined by some temporal and geographic interval), the average of all profiles retrieved with the new a priori profile is forced to be equal to the new a priori profile for that domain. Principal components analysis applied to in-situ profile datasets from two remote oceanic sites (Hawaii in the northern hemisphere, and Rarotonga in the southern hemisphere) is used to complement the information provided by the MOPITT data. The new seasonally- and latitudinally-variable a priori will be validated using monthly-mean surface station CO measurements compiled by the NOAA Climate Monitoring and Diagnostics Laboratory (CMDL).
A33D-0104 1340h
Odin/SMR Limb Observations of Nitrous Oxide in the Stratosphere: Analysis, Assessment, Applications.
The {\em Sub-Millimetre Radiometer} (SMR) on board the {\em Odin} satellite, \linebreak launched on 20 February 2001, performs regular measurements of the global distribution of stratospheric nitrous oxide (N$_2$O) using spectral observations of the J=20$\rightarrow$19 rotational transition centered at 502.296\,GHz. Roughly 3\,years of data have been accumulated so far. N$_2$O is a very useful tracer for global transport processes since it is chemically inert in the lower stratosphere with a lifetime of more than one year. We present the achieved measurement capabilities and assess the quality of the retrieved N$_2$O profiles ({\em level~2} product) by comparison with independent balloon- and aircraft-borne validation measurements. Odin/SMR data are also compared with preliminary results from the {\em Improved Limb Atmospheric Spectrometer-II} (ILAS-II) on board the {\em Advanced Earth Observing Satellite-II} (ADEOS-II) and from the {\em Michelson Interferometer for Passive Atmospheric Sounding} (MIPAS) on the {\em Envisat} satellite. Besides the quality assessment, the morphology of the global N$_2$O dataset is described and examples for applications such as the measurement of subsidence of air masses inside the polar vortices are given. Odin is a Swedish-led satellite project funded jointly by Sweden, Canada, Finland and France.
A33D-0105 1340h
On-orbit Calibration of Satellite Instruments Using the Moon
The Moon provides a unique and useful target for radiometric calibration of satellite instruments on-orbit. Although the lunar surface is non-uniform and non-Lambertian, it is extremely stable. Thus a model that fits the complex lunar reflectance properties, once established, can be applied to satellite observations of the Moon made at any time. The USGS RObotic Lunar Observatory (ROLO) project has developed a model for the lunar disk-equivalent irradiance,based upon a ground-based observational dataset spanning 6+ years. Irradiance data from $\sim$1200 observations are fitted for each of 32 bands covering wavelengths 350 to 2500~nm and phase angles from near-eclipse to 90$^\circ$. The empirical model form includes terms to accommodate lunar libration and the opposition effect. The mean absolute fit residual is below 1%. Comparisons against the ROLO model are presented for seven remote sensing imaging instruments: SeaWiFS, Hyperion, ALI, MTI, MODIS-Terra, MISR and ASTER. These results show significant calibration discrepancies among the instruments. Although the absolute calibration of the ROLO data still has some persistent uncertainties, the model supports relative response trending with sub-percent precision. SeaWiFS has observed the Moon nearly monthly since 1997 November. Based on the first 66 lunar observations, a time-dependent correction for SeaWiFS ocean-leaving radiance data has been developed; these trend corrections have residuals $\sim$0.1%. This level of precision achievable with the ROLO lunar irradiance model can meet the long-term stability requirements for climate research data products derived from space-based instrumentation.
http://www.moon-cal.org
A33D-0106 1340h
The Orbiting Carbon Observatory (OCO) Mission: Validation Strategy and First Retrieval Results
The Orbiting Carbon Observatory (OCO) mission will make the first global, space-based measurements of atmospheric CO2 with the precision, resolution, and coverage needed to characterize CO2 sources and sinks on regional scales. During its 2-year mission, OCO will fly in a sun-synchronous orbit with a 16-day ground-track repeat time, just ahead of the EOS Aqua platform. OCO incorporates three bore-sighted high-resolution spectrometers to measure reflected sunlight in the O2 A-band and in the CO2 bands at 1.61 and 2.06 microns. Soundings recorded in these three bands will be analyzed simultaneously to retrieve the column-averaged CO2 dry air mole fraction. In order to verify and improve the space-based CO2 measurements the OCO project incorporates a comprehensive validation program based on ground-based Fourier Transform Spectrometers (FTS) measuring direct sunlight. These measurements are ideally suited since the vertical sensitivity is very similar and the same quantity is measured using the same O2 and CO2 absorption bands as OCO. As an important part of this strategy these FTS measurements will be analyzed using the same retrieval algorithm as for the space-based measurements. In this paper we will discuss the OCO retrieval algorithm and the validation strategy. Also we will present some first results obtained with the OCO retrieval algorithm using space-based SCIAMACHY and ground-based FTS measurements. These retrieval exercises are especially helpful for the characterisation and validation of the retrieval algorithm under realistic measurement conditions.
A33D-0107 1340h
Validation of Calibration Corrections Applied to EarthProbe TOMS in Response to Significant Instrument Degradation
EarthProbe TOMS solar calibration data show a dramatic, time-dependent decrease in instrument sensitivity of nearly 50% between 2000 and 2002. A simple thin film interference model suggests that contaminant build-up on the scan mirror is responsible. Also, analysis of unusual total ozone patterns across scans reveal a scan angle-dependent, wavelength-dependent instrument error in radiance sensitivity that developed at the same time. The angular dependence of radiance measurements interferes with on-board calibration, which requires equal radiance sensitivity across the angular range between the solar calibration diffuser and Earth-viewing scan angles. Soft calibration methods and inter-satellite comparisons have been used to assess these instrument changes. The scan angle dependence is captured assuming average longitudinal homogeneity of ozone at the equator across the 2200 km wide TOMS scan swath, and then characterizing radiances at all scan angles using ozone sensitivities. Overall trends in instrument sensitivity are determined using spectral discrimination analysis and total ozone comparisons with SBUV/2 instruments at the equator. Based on these results, calibration corrections were applied uniformly with latitude in the official reprocessing of the EarthProbe TOMS data using the new Version 8 algorithm. We have now extended the corrected dataset through June 2004. Results show 1-3% agreement with NOAA-11 and 16 SBUV/2 data at the equator, and independent comparisons with Brewer ground measurements show differences of 1-2%. However, these corrections are less effective at high latitudes, and measurements of ice radiance over Greenland and Antarctica suggest signal level-related issues may play a role. Users should exercise caution and evaluate the latter EarthProbe data (2000-present) for their specific purpose. Analysis of these data for long-term trends is discouraged. Overall however, the instrument has stabilized, and our corrections make TOMS data useful for inter-comparison with OMI in the coming year.
A33D-0108 1340h
Soundings and Satellite Ozone Combine to Reveal Mechanisms for the Intraseasonal Variability of Tropospheric O$_3$ during the Indian Winter Monsoon (INDOEX Period)
The tropospheric ozone (O$_3$) column over the Northern Hemisphere Indian Ocean displays complex temporal and spatial variability. We describe daily northern-winter variations over the northern Indian Ocean for the INDOEX period. In this period, a rich dataset of soundings allows us to disentangle this rich spatial and temporal variability in terms of underlying process. Total tropospheric ozone, TTO, satellite data [Hudson and Thompson, 1998] provides geographic descriptions for the whole region, and is validated in our study. Vital information about vertical distribution comes from ozonesondes aboard the Research Vessel Ronald H. Brown, moving 15$^\circ$S to 15$^\circ$N, and from special sondes launched at Kaashidhoo in the Maldives (5$^\circ$N). Analysis shows that (a) elevated low-level O$_3$over the northern Indian Ocean mainly originated from the Indian subcontinent with a maximum contribution from high emission areas, generally the northern industrial-agricultural around the Ganges Plain. Convective activity just south of Sri Lanka significantly affects pollutant outflow from the Northern Indian Subcontinent. (b) The middle tropospheric O$_3$ maximum observed over the Northern Indian Ocean alternates from different sources, sometimes changing rapidly. (c) Mixing in of stratospheric air introduced along the subtropical jet apparently often raised tropospheric O$_3$ at the beginning of March by $\sim$40--50 ppbv, especially poleward of ~10$^\circ$N. (d) Convective lofting of Asian pollutants could also add about 20--50 ppbv to middle troposphere at 5--10$^\circ$N, alternating with stratospheric influence. The soundings show that one influence producing high ozone can be replaced by another within a few hours. Similarly, TTO maps also suggest that features with different origins can merge. The southern (pollutant) buildup seen in TTO has long-range effects, traveling towards across Africa. Our broadest point is that the variance of tropical tropospheric ozone is only poorly captured by seasonal averages or those based on global circulation indicators like warm/cold-phase ENSO.
http://geo.arc.nasa.gov/sgg/chatfield/recentRes.html
A33D-0109 1340h
IMAA-CNR Campaign for the Validation of MIPAS Water Vapor and Temperature Products
An intensive measurement campaign, has been performed at IMAA in Tito Scalo (PZ) (Southern Italy, 40°36'N, 15°44'E, 820 m above sea level) in the framework of the validation program of ENVISAT. This campaign has been carried out by using a Raman lidar system, able to perform measurements of water vapor mixing ratio vertical profiles with high vertical and temporal resolution, and a radiosounding station for PTU measurements. These data have been used to validate MIPAS water vapor and temperature products. In the period July 2002 - December 2002, 2 radiosoundings and 2 lidar measurements of water vapor mixing ratio per week in coincidence with satellite overpasses have been performed. In the period January 2003 - July 2003, 1 radiosounding and 1 lidar measurement per week have been performed. Moreover, after the validation campaign, systematic measurements are still in progress. A set of criteria was defined to select the overpasses and to decide when MIPAS, lidar and radiosounding measurements can be considered as coincident and used for the validation: a) the maximum spatial distance between MIPAS overpass and IMAA station has to be lower than 1000 km; b) the maximum temporal distance between MIPAS overpass time and the radiosonde launch time has to be lower than 2h30min; c) the lidar water vapor vertical profile is retrieved by integrating measurements over 10 minutes, with this time interval centered on the overpass time. An analysis of the comparison between MIPAS, lidar and radiosonde for H2O measurements has been performed in terms of water vapor mixing ratio. This is directly measured by Raman lidar, while for MIPAS it is easily obtained converting the ppm unit and for radiosonde is obtained by using relative humidity and simultaneous pressure and temperature profiles. Starting from the available MIPAS data processed with IPF 4.61, used for the validation purposes, a mean underestimation of MIPAS of 0.016 g/kg has been observed in the altitude range of 10-13 km above sea level. It is evident that MIPAS presents several problems in performing water vapor measurements in the tropopause because of the sharp gradient in water vapor content typical at these heights. MIPAS temperature data have been validated by means of a radiosounding system located at IMAA-CNR. A total number of 12 coincidences with a 98 temperature compared points has been studied. The agreement is quite good. However, it is not possible to verify and quantify the presence of any temperature bias, because of the large MIPAS temperature error. In the near future, the availability of more reprocessed MIPAS data will improve validation activity. ACKNOWLEDGMENTS The financial support of this work by the European Space Agency under grant ESA-ESTEC Contract No. 16040/02/NL/SF, "Ground based observations of water vapour and aerosol for the validation of ENVISAT products", is gratefully acknowledged.
A33D-0110 1340h
Airborne Sunphotometer and Related Measurements Acquired Over the Gulf of Maine during INTEX-ITCT 2004
The NASA Ames 14-channel Airborne Tracking Sunphotometer (AATS-14) took measurements from aboard a Jetstream 31 (J31) twin turboprop aircraft during 19 science flights (~53 flight hours) over the Gulf of Maine during 12 July - 8 August 2004. The flights were conducted in support of the INTEX-NA (INtercontinental chemical Transport EXperiment-North America) and ITCT (Intercontinental Transport and Chemical Transformation of anthropogenic pollution) field studies. AATS-14 measures the solar direct-beam transmission at 14 discrete wavelengths (354-2138 nm), and provides instantaneous measurements of aerosol optical depth (AOD) spectra and water vapor column content, in addition to vertical profiles of aerosol extinction and water vapor density during aircraft ascent and descent. Also on board the J31 during the mission was the NASA Ames Solar Spectral Flux Radiometer (SSFR). SSFR consists of separate nadir and zenith viewing hemispheric FOV sensors that yield measurements of downwelling, upwelling, and net solar irradiance at a spectral resolution of ~8-12 nm over the wavelength range 300-1700 nm. The objectives of the J31-based measurements were to validate MODIS (MODerate-resolution Imaging Spectroradiometer) and MISR (Multi-angle Imaging Spectro-Radiometer) aerosol retrievals, quantify sea surface spectral albedo (which can contribute the largest uncertainty to MISR aerosol retrievals for low aerosol loading), test closure (consistency) among suborbital results, test chemical-transport models using AOD profiles, and assess regional radiative forcing by combining satellite and suborbital results. Combination of coincident AATS-14 and SSFR measurements allows derivation of aerosol radiative forcing from simultaneously measured radiative flux and AOD gradients, and the derivation of spectra of aerosol absorbing fraction from spectra of radiative flux and AOD. Specific J31 flight patterns were designed to address the science goals, and these patterns included a mixture of vertical profiles (spiral and ramped ascents and descents) and constant altitude horizontal transects at a variety of altitudes. Flight plans often included profiles above NOAA Ship Ronald H. Brown and, in a few cases, coordination with other mission aircraft - namely, the NOAA DC-3 and the NASA DC-8. In general, flight plans were designed to include a near sea surface horizontal transect in a region of minimal cloud cover during or near the time of an AQUA (MODIS) and/or TERRA (MODIS and MISR) satellite overpass. Twelve J31 flights included segments that were temporally and/or spatially near-coincident to the satellite overpasses. These included four MISR local mode events, of which one involved a successful J31 and DC-8 flight coordination. In this paper, we focus on satellite validation measurements obtained with AATS-14.
A33D-0111 1340h
Validation of SCIAMACHY tropospheric NO2 columns with in-situ profiles during INTEX-NA
Tropospheric NO2 columns from SCIAMACHY are retrieved using the reference sector and nadir-limb subtraction methods during the INTEX-NA (North America) campaign in July and August of 2004. The TD-LIF (thermal dissociation laser-induced fluorescence) instrument measured NO2 vertical profiles in-situ during ascents and descents by the DC-8 during INTEX-NA. Tropospheric profiles measured by the TD-LIF technique are vertically integrated to provide in-situ tropospheric columns. A three-way comparison is performed between SCIAMACHY reference sector, nadir-limb matching and TD-LIF techniques.
A33D-0112 1340h
A New AVHRR Pathfinder Atmospheres Extended (PATMOS-x) Data Set
The NOAA/NESDIS Office of Research and Applications has funded a pilot study to improve the quality of the 24-year (1981-2004) data record from NOAA's Advanced Very High Resolution Radiometer. In addition to improving the data, this project also includes the creation of new climate data sets from the AVHRR. One of these climate data sets is a new and extended version of the AVHRR Pathfinder Atmospheres (PATMOS-x) project. PATMOS-x includes many radiometric, cloud and surface parameters that have all benefited from the calibration and navigation improvements to the AVHRR GAC data. Compared to the original PATMOS data set, PATMOS-x includes the data from the morning satellites, the NOAA-klm series of satellites and includes many more parameters. PATMOS-x is not uniquely a land data set, although it includes NDVI, land surface temperature and snow cover. Other variables in the data set such as channel radiance values, aerosol optical depth, SST, radiation budget and cloud amounts and properties will provide valuable ancillary data to support land studies. The climate data records from PATMOS-x have a spatial resolution of 0.25 or 0.5 degrees and are freely available in an easy to read HDF format. This paper will highlight some of the recent calibration and navigation improvements and give example time series of selected PATMOS-x parameters.
http://cimss.ssec.wisc.edu/clavr
A33D-0113 1340h
Three Years of OSIRIS Stratospheric O$_3$ and NO$_2$ Measurements: A Valuable Dataset for Intercomparison Studies
The Optical Spectrograph and InfraRed Imager System (OSIRIS) was launched onboard the Odin satellite in February 2001. Since the satellite became fully operational in November 2001, stratospheric ozone and nitrogen dioxide profiles have been routinely retrieved from the limb-scattered sunlight measurements made by OSIRIS. Both species are retrieved between 10 km and 50 km with a vertical resolution of about 2 km and an accuracy of 10% at 30 km. Various studies have found the results to be in good agreement with other satellite, balloon-based and ground-based instruments. In this paper an overview of the OSIRIS stratospheric ozone and nitrogen dioxide dataset will be presented. The dataset offers an excellent source for intercomparison studies.
A33D-0114 1340h
Initial Validation of SAGE III Limb Scattering Ozone Retrievals
In addition to its regular operation in solar and lunar occultation modes, the SAGE III instrument has been used to measure limb scattering (LS) radiance spectra. Initial LS ozone retrievals have shown good agreement with correlative data available from ozonesondes, occultation data (from SAGE II and SAGE III), limb scattering data (from SOLSE/LORE-2 and ODIN/OSIRIS), and nadir viewing data (from TOMS). We outline a comprehensive validation plan for the SAGE III LS ozone profiles, and present preliminary results of this effort.
A33D-0115 1340h
MAESTRO O$_3$ and NO$_2$: A comparison with coincident OSIRIS profiles
MAESTRO (Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) is a UV-visible spectrometer performing solar occultations and nadir backscatter measurements on board ACE (Atmospheric Chemistry Experiment, or SCI-SAT I) since August 2003. In this paper we present an introduction to the MAESTRO instrument and retrieval algorithms and a comparison of MAESTRO O$_3$ and NO$_2$ profiles with coincident OSIRIS (Optical Spectrograph and Infrared Imager System) measurements. To faciltate the comparison, OSIRIS NO$_2$ profiles have been shifted from their local time to a SZA of 90$^\deg$ using a photochemical model.