A13C-1353
Evaluation of the New HOxotope Total Water Isotopologues Instrument Performance During TC4 Through Instrument Intercomparison
Measurements of the relative abundance of HDO and H2O serve as a sensitive indicator of the convective history of an airmass. We present measurements of total water isotopologues (condensed and vapor phases) from the upper troposphere and lower stratosphere that were obtained by the HOx total water isotopologues instrument (HOxotope) onboard the NASA WB-57 aircraft during the TC4 field campaign. Measurements are obtained using a new inlet to sample water particles and vapor isokinetically. The inlet is designed to provide accurate, contamination-free total water isotopologue measurements by vaporizing condensed water prior to detection. Contamination is evaluated by the time response of our system between regions of high- and low- water as determined through comparisons with established water vapor measurements, made by Harvard's Lyman-α instrument (Harvard Water) and Jet Propulsion Laboratory's laser hygrometer instrument (JLH). Instrument sensitivity and time response during particle sampling is evaluated by comparison with the University of Colorado's closed-path laser hygrometer (CLH).
A13C-1354
Preliminary analysis of an ozonesonde data from Panama as part of TC-4
During July and August 2007, 25 ozonesondes were launched from Las Tables, Panama (7.8 N, 80.3 W) resulting in a unique data set that complements and enhances data from the SHADOZ network. Launches occurred nearly daily around 1 pm to provide the best possible coincidences with overpasses of the Aura satellite. In this presentation, we examine the exchange of air between the stratosphere and troposphere as evidenced from the profile data and make comparisons between the Panama sonde data, data from Aura satellite instruments including TES and OMI, and data from the SHADOZ network. http://physics.valpo.edu/ozone/tc4data.html
A13C-1355
TC4 campaign results: validating the Aura OMI total ozone data in tropics with the airborne CAFS and DIAL ozone measurements.
Highly resolved UV and Visible actinic flux measurements were taken by the CCD Actinic Flux Spectrometer (CAFS) instrument (R. Shetter, NCAR) onboard the NASA DC8 aircraft as part of the Tropical Composition, Clouds and Climate Coupling (TC4) campaign in Costa Rica. The partial ozone column above the aircraft products were derived from the CAFS actinic flux measurements as part of the continuous validation of the Aura ozone products. Although substantial parts of the NASA DC8 flights were flown in the clouds that somewhat inhibited the CAFS ozone retrieval algorithm, a sizable data set of partial ozone columns along the tracks of the Aura satellite were obtained. Preliminary analysis of the CAFS measurements shows the ability of the CAFS retrieval to produce good quality ozone data from measurements taken under thin cirrus clouds. Partial ozone column data above the aircraft were derived under conditions of high-sun and low ozone. The set of combined CAFS and climatological ozone data was used for validation of the Ozone Monitoring Instrument (OMI) total ozone column under low ozone and high-sun conditions. In addition, we will present preliminary results of comparisons between the OMI total ozone column and combined stratospheric ozone columns derived from the CAFS measurements and tropospheric ozone columns integrated from the Differential Airborne Lidar (DIAL) measurements onboard the NASA DC8 aircraft. We will also discuss results of the OMI total ozone column validation during the TC4 campaign, preliminary comparisons between DIAL tropospheric ozone columns and 4D climatology for the summer tropical troposphere, and address similarities and differences between the TC4 (tropical summer) and CR-AVE06 (tropical winter) campaign results. Results of the analysis will include estimates of uncertainties in the CAFS retrievals due to its limited sensitivity to the ozone distribution above the aircraft altitude, as well as uncertainties due to effects of the bright surfaces (clouds) on the CAFS and OMI ozone retrievals.
A13C-1356
Interaction of nitric acid and cirrus clouds in the tropical upper troposphere during TC4
Impacts of cirrus clouds on climate and the composition of the tropical upper troposphere were major foci of NASA's Tropical Composition, Cloud, and Climate Coupling Experiment (TC4). One chemical impact that has been postulated is removal and vertical redistribution of HNO3 through uptake on cirrus particles. Limited previous sampling campaigns have provided somewhat differing results and are not fully compatible with theory developed from lab studies. While deployed to San Jose, Costa Rica during the TC4 field campaign (July-August, 2007) the NASA DC-8 research aircraft spent approximately 41 flight hours in the tropical upper troposphere (> 9 km pressure altitude) during 15 flights. Close to half of the sampling time in the UT consisted of "racetrack" patterns in cirrus clouds from anvil outflow. Interstitial mixing ratios of HNO3 were depressed (mean 36 pptv) compared to clear air encountered in the UT (mean 70 pptv). Full depletion of HNO3, however, was never observed (minimum 5 pptv). HNO3 mixing ratios observed in-cloud varied considerably. HNO3 mixing ratios generally increased as condensed water decreased. On several flights, the same cloud region was traversed multiple times. Condensed cloud water content data revealed persistent regions of "thicker" cloud with less HNO3 and contrasting "thinner" cloud with relatively enhanced HNO3. Microphysical measurements of cloud properties from in situ instruments on the DC-8 may allow factors controlling the partitioning of HNO3 between the gas phase and cirrus particles in these relatively warm clouds (> 215K) to be determined. Also, strong enhancements of HNO3 at the base of the anvil systems apparently reflect vertical redistribution of HNO3 by sedimenting cirrus particles and subsequent particle sublimation and HNO3 evaporation. The impact of released HNO3, however, appears to be restricted to a very thin layer just below the cloud.
A13C-1357
Measured and modeled solar spectral irradiance and absorption for TC4 ice and water cloud scenes
The TC4 experiment provided extensive coordinated above- and below-cloud measurements of solar spectral irradiance (Solar Spectral Flux Radiometer) onboard the NASA ER-2 and DC-8 aircraft, which also carried various active and passive cloud remote sensing as well as in-situ cloud instrumentation. We present measured spectral irradiance and absorption along coordinated flight legs for water and ice clouds. We derive effective radius from reflected and absorbed irradiance along those legs and relate those to CAPS (Cloud Aerosol and Precipitation Spectrometer) in-situ measurements onboard the DC-8 and to retrievals from MAS (MODIS Airborne Simulator) and MASTER (MODIS and ASTER Airborne Simulator) onboard the ER-2.
A13C-1358
Recent measurements of water vapor in the TTL by the JPL Laser Hygrometer
The NASA Tropical Composition, Clouds and Climate Coupling Experiment (TC4) was a major effort combining satellite, aircraft, balloon, and ground-based measurements to study the tropical tropopause layer (TTL). One of the goals of this mission was to better understand the behavior and distribution of water in the TTL, which is important to climate through the greenhouse effect and the radiative impact of clouds. Here, we present new measurements of water vapor in the TTL measured by the JPL Laser Hygrometer (JLH) on the WB-57 aircraft during TC4. JLH utilized both harmonic and direct-absorption spectroscopy to measure water vapor. JLH water vapor profiles are compared with EOS MLS satellite retrievals as well as the Cryogenic Frostpoint Hygrometer. These results have been verified by recent laboratory measurements by JLH. We will discuss the implications of these profiles for theories of cloud formation in the TTL.
A13C-1359
In situ measurements of subvisual cirrus from the WB-57 aircraft during TC4
Subvisual cirrus (SVC) clouds are ubiquitous, and are recognized as playing an important, yet poorly constrained, role in Earth's radiation budget as well as stratospheric dehydration processes. During the 6 August TC4 flight, the WB-57 made several vertical profiles of a subvisual cirrus layer. Data from the cloud physics lidar (CPL) aboard the NASA ER-2 aircraft confirms the presence of this SVC layer, which would have likely gone unnoticed in the in situ data set because of the low signal contrasts relative to background. Measurements made during the SVC passes include total water/ice water content (IWC), cloud particle spectrometer and imaging measurements, and water vapor. These measurements are presented and compared to recent work on subvisual cirrus from the 2006 CR-AVE campaign, which was also based out of Costa Rica.
A13C-1360
Short-lived Organic Compounds in the UTLS
Measurements of short-lived organic compounds un the UTLS region have been used in a number of ways, including characterization of bromine and chlorine budgets, transport processes, and the age spectrum in the LS. The short-lived halogen source gases may play an important role in ozone chemistry in the UTLS, however, their source strengths and distributions are difficult to characterize due to spatial and temporal variations in emissions from organic halogens with natural origins. Recent airborne campaigns provide excellent opportunities to further characterize the mixing ratios and spatial distributions of the organic halogens as well as nonmethane hydrocarbons and alkyl nitrates in the tropical and midlatitude troposphere and lower stratosphere regions. This work will present a summary of measurements from TC4 and previous airborne campaigns of the organic halogen budgets and vertical distributions of selected short-lived organic compounds.
A13C-1361
In situ water isotope measurements aboard the WB-57 from 2005 to 2007: searching for seasonal and latitudinal trends
We present new TTL and lower stratospheric in situ observations of water isotopes obtained on the NASA WB-57 in the summer and winter in both Houston and Costa Rica. The seasonal and latitudinal spread of data from AVE-WIIF, CR-AVE, and TC4 allow for an investigation of winter-to-summer and latitudinal variability in δD using a self-consistent, exclusively in situ data set. The relative abundance of the hydrogen isotopes of water, H2O and HDO, is a sensitive indicator of the condensation history of an air mass in the upper troposphere and lower stratosphere. Measurements of δD, then, can lend insight to understanding how, where, and when water vapor and air in general are transported into the stratosphere. Traditional thought maintains that stratospheric water enters in the tropics, though the transport mechanism and longitudinal location has always been subject to debate. Numerous recent measurements, however, show evidence of a convective source of overworld stratospheric water vapor in the mid-latitudes, though the relative influence of the source has yet to be determined. Comparison of mid-latitude profiles to those from the tropics, as well as to prior remote and in situ observations, provides a context for these observations.
A13C-1362
Factors Influencing Aerosol Concentrations and Properties over the Tropical Eastern Pacific: Observations from TC4
The NASA Tropical Composition Cloud and Climate Coupling (TC4) mission was conducted during summer 2007 and had the primary objective of gaining a better understanding of composition and dynamics of the upper troposphere over the tropical eastern pacific region. Based in San Jose, Costa Rica, the mission employed instrumented aircraft along with ground, balloon, and satellite borne sensors to determine the spatial distribution of trace gas and aerosol species as well as moisture and clouds between the surface and roughly 16 km altitude over Central America, the eastern Pacific, the western Caribbean and northern South America. Because of its heavy payload and long endurance capability, the NASA DC-8 aircraft was the primary sampling platform for the lower-tropospheric altitude regime (i.e., below 12 km). It carried both remote and in situ instruments and was used to characterize cloud inflow and outflow as well as the microphysical properties of maritime convective systems. Because of their roles in regulating atmospheric radiation transfer and cloud formation and microphysics, flight plans placed particular emphasis on determining the sources and properties of the aerosol particles present within the region. A preliminary analysis of the DC-8 data set suggests that the following sources/processes had the greatest impact on aerosol number and mass loading: dust transport from Africa; sea salt production over the ocean; urban and biogenic emissions over the continent; secondary aerosol formation in volcanic plumes; nucleation in cloud outflow; and cloud scavenging. In this presentation, we will examine the microphysical, optical and hydration properties of each aerosol type and assess the overall impact of the source/sink processes to the regional aerosol budget. We will also contrast the microphysical properties of the Saharan Dust sampled over the Caribbean with those measured in fresh dust layers over the eastern Atlantic from the DC-8 during the summer 2006, NASA African Monsoon Multidisciplinary Activity (NAMMA).
A13C-1363
First Results From TC4: Halocarbons, Hydrocarbons, Alkyl Nitrates, OCS and DMS Measured in Whole Air Samples Collected Aboard the NASA DC-8
We present initial results from samples collected aboard the NASA DC-8 during the July and August 2007 TC4 campaign. All 1280 samples were analyzed by gas chromatography for selected C2-C10 nonmethane hydrocarbons, selected C1-C2 halocarbons (including CFCs, CH3Br, CH2Br2 and CH3I), C1-C5 alkyl nitrates, OCS, and DMS. During TC4 our measurements identified numerous air masses containing elevated levels of trace gases, of both marine and continental origin, that had been lofted to high altitude by convective systems. We compare and contrast marine emissions from the Pacific and Atlantic (Caribbean) Oceans. As reported previously, methyl nitrate levels are elevated in the equatorial Pacific marine boundary layer (MBL) but during TC4 levels over the Caribbean were close to background. By contrast, CH3I proved to be a much more general tracer for MBL air in this region.
A13C-1364
Preliminary Evaluation of GEOS-5 Aerosol and CO Distributions Forecast During TC4
The NASA Tropical Composition, Cloud, and Climate Coupling (TC4) Mission was based out San Jose, Costa Rica during July and August 2007. During TC4 the NASA Global Modeling and Assimilation Office (GMAO) ran twice-daily 0.5° x 0.666° global 5-day forecasts of the Goddard Earth Observing System atmospheric general circulation model and data assimilation system (GEOS-5). This implementation of GEOS-5 contained an aerosol and carbon monoxide (CO) model to provide online forecast tropospheric distributions of dust, sea salt, sulfate, and carbonaceous aerosols and CO for both the planning of flights and for science. Here we provide a description of the aerosol and CO modeling system and give a preliminary evaluation of forecast tracer distributions. Our comparisons to satellite observations of aerosol and CO show qualitatively similar simulated distributions of tracers to those observed. During TC4 copious amounts of dust were observed in the Caribbean. The model generally reproduced the observations of the timing of dust events and the vertical structure in the lower atmosphere. However, the model simulations had too much aerosol at high altitudes relative to airborne Cloud Physics Lidar observations. The results were similar for biomass burning aerosol and CO tracers, where the model showed higher simulated concentrations of these tracers at aircraft flight altitude than observations. http://code613-3.gsfc.nasa.gov/People/Colarco/Mission_Support/
A13C-1365
A Climatology of Saharan Dust Measurements Observed by CALIPSO, MODIS, and OMI in Support of the TC4 Field Experiment
During summer months, elevated layers of Saharan dust form off the western African coast and are frequently carried across the North Atlantic Ocean into the extreme western Caribbean region by predominate easterly flow. For more than a decade, satellites have observed this pattern of dust transport. Somewhat strikingly, however, is the absence of enhanced aerosol observations in the region immediately across the Isthmus of Panama and lower Central America in the adjacent waters of the Pacific Ocean. One of the goals of the Tropical Composition, Clouds, and Climate Coupling Experiment (TC4) field mission is to better understand the cause of this observed gradient in dust properties and help answer questions on how dust may be scavenged by precipitation from tropical convection, how they may be lofted to the upper troposphere, or how transport may be blocked by coastal mountain ranges and diverted along the coast. This poster will a present an aerosol climatology compiled for the summer of 2007 using measurements from CALIPSO, MODIS, and OMI – members of the A-Train satellite constellation. CALIPSO provides profile observations of aerosols and clouds with a two-wavelength polarization-sensitive lidar. MODIS and OMI provide aerosol observations over broader geographical regions at visible and in the near UV region, respectively. Together these datasets provide complementary information on Saharan dust that can provide a broad context for interpreting the aircraft measurements acquired during TC4. Preliminary comparisons on spatial homogeneity and typing with aircraft lidar and in situ aerosol observations will also be presented.
A13C-1366
High Spectral Resolution Infrared Closure Study Applied to TC4 Cloud Property Retrievals
A NASA Tropical Composition, Cloud and Climate Coupling (TC4) mission was conducted to investigate the structure, properties and processes in the tropical Eastern Pacific. The mission was designed from the perspective of the A-train satellite measurements: to both validate and provide critical observations not available from the satellites. A-train observations were well represented by aircraft measurements collected from the NASA ER-2 instrument suite. For this study we include the Scanning High Resolution Interferometer Sounder (S-HIS), the MODIS Airborne Simulator (MAS), and the Cloud Physics Lidar (CPL), which are akin to A-train instruments AIRS, MODIS, and Calipso, respectively. Cloud property retrievals obtained during the TC4 mission will be utilized to produce upwelling infrared radiance spectra using a radiative transfer model. These results will be compared to high spectral resolution infrared measurements acquired by the S-HIS (University of Wisconsin). A Line-by-Line Radiative Transfer Model (LBLRTM) has been combined with the Discrete Ordinate Radiate Transfer (DISORT) model to form a single application (LBLDIS) which can be used to calculate infrared atmospheric emission spectra in the presence of clouds or aerosol. Clear sky atmospheric state profiles, used as input to LBLDIS, will be determined using local radiosondes or National Center for Environmental Prediction (NCEP) Model data if measured profiles are unavailable. Cloud optical property input to LBLDIS (e.g., visible optical depth and bulk crystal effective radius) will be results that were retrieved from CPL (NASA GSFC) and MAS (NASA GSFC) measurements.
A13C-1367
Water Vapor in the Tropical Upper Troposphere and Lower Stratosphere over Costa Rica: Insights from In Situ Measurements from the TC4 and CWVCS Summertime Missions
In situ measurements of water vapor and its isotopologues from the suite of Harvard University instruments, in combination with simultaneous measurements of other tracers and meteorological parameters acquired aboard the WB-57 aircraft during two summertime missions out of San Jose, Costa Rica, are used to investigate the processes controlling water vapor in the tropical upper troposphere and lower stratosphere. Measurements from both the Clouds and Water Vapor in the Climate System (CWVCS) mission during August 2001, and the recent Tropical Composition Cloud and Climate Coupling (TC4) mission during August 2007, provide an excellent combined data set for investigating the causes of observed short-term (i.e. flight-to-flight) variability in water vapor concentrations in the UT/LS, and differences between the data sets provide a means of assessing inter-annual variability in this region. Both data sets show evidence of extreme short-term variability in UT water vapor, with the near-tropopause concentrations in both missions differing by more than 10 ppmv from flight to flight. Very low near-tropopause mixing ratios are coincident with the cooling of the upper tropical troposphere and tropopause. However, whether this is evidence of local in situ dehydration or part of a mesoscale change in the temperature and humidity structure of the tropical UT remains to be determined. Additionally, does this variability propagate into the lower tropical stratosphere? The data from both missions show no evidence of the dehydrated air masses impacting lower stratosphere humidity, however, the data do show evidence of the convective injection of water vapor and/or ice directly into the tropical lower stratosphere. Back-trajectory analyses, as well as MLS tracer contour maps, will be used to pinpoint the location, again whether local or remote, of these large-convective events. In general, the combined data set provides a rich set of examples of different processes that affect water vapor in the tropical UT/LS.
A13C-1368
Temperature, Water Vapor, and Trace Gas Profile Retrievals from the University of Wisconsin Scanning High-resolution Interferometer Sounder (S-HIS) during the TC4 Campaign
The University of Wisconsin Scanning High-resolution Interferometer Sounder (S-HIS) provides the high spectral resolution infrared observations on the high altitude NASA ER-2 aircraft to complement the MODIS Airborne Simulator (MAS) and the NASA Cloud Physics Lidar (CPL) on the same aircraft platform. These instruments provided high spatial resolution aircraft measurements during the NASA TC4 experiment in July-Agust 2007 in a manner similar to the lower spatial resolution observations from the AIRS, MODIS, and CALIPSO sensors on the NASA A-train. The S-HIS measures the upwelling infrared spectral radiance between 3.3 and 18 microns at 0.5 cm-1 (unapodized) spectral resolution in a cross-track swath of 14 fields of view of approximately 2 km diameter. The S-HIS is an airborne version of the advanced sounder AIRS found on the NASA Aqua satellite, the IASI sensor on the METOP-A satellite, and the CrIS sensor on the NPP/NPOESS platforms. During the TC-4 campaign based out of San Jose, Costa Rica, the S-HIS compiled a nearly perfect record of measurements for each ER-2 flight. Highlights of these missions will be presented in this paper, including measurement of the elevated dry layer associated with a Saharan Air Layer (SAL) sampled on 19 July 2007 in the Caribbean sea, measurement of upper level water vapor over the Galapagos Islands coincident with in situ validation, and retrieved levels of carbon monoxide associated with biomass burning. The retrieval uses Bayesian estimation based upon a maximum a posteriori (MAP) method which combines information contained in the spectral radiances with a priori information provided by climatological measurements for the TC4 domain. This paper includes a description of the S-HIS observations, the inversion method, prelimianry results, and comparison to model and validation data.
A13C-1369
Lidar Measurements of Ozone, Aerosols, and Clouds Observed in the Tropics Near Central America During TC4-Costa Rica
Large-scale measurements of ozone and aerosol distributions were made from the NASA DC-8 aircraft during the TC4 (Tropical Composition, Cloud, and Climate Coupling) field experiment conducted from June 28 - August 10, 2007 based in San Jose, Costa Rica. Remote measurements were made with an airborne lidar to provide ozone and multiple-wavelength aerosol and cloud backscatter profiles from near the surface to above the tropopause along the flight track. Aerosol depolarization measurements were also made for the detection of nonspherical aerosols, such as mineral dust, biomass burning, and recent emissions from South American volcanoes. Long-range transport of Saharan dust with depolarizing aerosols was frequently observed in the lower troposphere both over the Caribbean Sea and Pacific Ocean and within the marine boundary layer. In addition, visible and sub-visible cirrus clouds were observed with the multi-wavelength backscatter and depolarization measurements. Initial distributions of ozone, aerosol, and cloud are presented which will be used to interpret large-scale atmospheric processes. In situ measurements of ozone and aerosols made onboard the DC-8 will be compared to the remote lidar measurements. This paper provides a first look at the characteristics of ozone, aerosol, and cloud distributions that were encountered during this field experiment and provide a unique dataset that will be further related through satellite data, backward trajectories, and chemical transport models (CTM) to sources and sinks of ozone, aerosols, and clouds and to dynamical, chemical, and radiative processes.
A13C-1370
Measured Radiative Properties of Thin Cirrus During TC4
Thin, often subvisible, cirrus clouds are very common in the tropics but their importance to the radiative budget, their effect on stratosphere-troposphere exchange, and their formation and persistence mechanisms are still uncertain. Here we will present direct measurements of the heating rates of tropical thin cirrus in order to gain insight into whether the absorption of radiative energy contributes to the lifting and persistence of these clouds. During TC4, measurements of the upwelling and downwelling broadband infrared irradiance and spectral solar irradiance were made from both the NASA ER-2 aircraft flying above the cirrus and the NASA DC-8 aircraft flying below the cirrus. This data will be used to derive the heating and cooling rates of the thin cirrus, while downlooking cloud lidar measurements from the ER-2 will be used to detect their presence, altitude, thickness, and estimated optical depth. We will focus on two case study days from TC4, the 25July2007 flight, where the ER-2 attempted to fly a descent profile through a thin cirrus layer, and the 6Aug2007 flight where the ER-2 flew above a thin cirrus layer while the DC-8 flew below.
A13C-1371
Convective generated cirrus observed by CRS and EDOP during TC4
Tropical cirrus cloud plays an important role in the Earth's climate system. Cirrus ice crystals scatter incoming sunlight, reducing the solar radiation reaching Earth's surface, resulting in a surface cooling effect. Cirrus clouds also absorb upwelling infrared radiation emitted from the surface and lower atmosphere, reducing the infrared energy escaping the Earth-atmosphere system. The net effect of tropical cirrus on surface temperature depends on several factors including cloud height, cloud thickness, and ice crystal size. A significant portion of the tropical cirrus is directly associated with deep convection. Cloud Radar System (CRS), operating at 94 GHz, same frequency as that of CloudSat, detects both thin and thick cirrus outflow from deep convection but it cannot penetrate deep convection because of its strong attenuation. The ER-2 10?GHz Doppler precipitation radar provides detailed vertical structure of the convective and thick cirrus cloud. During TC4, there were a number of good cases where the ER-2 flew over the DC8 and the WB-57 the last few days. EDOP and CRS data provide information on the convection that produced the cirrus and the cirrus structure. This data combined with other remote and in situ data sets provides a wealth of information for studying the mechanisms of cirrus formation, detrainment in the TTL, and ice retrieval algorithms. This presentation will focus on characterizing cirrus evolution and associated convection from a radar point of view, examining whether there are any obvious signatures of cirrus evolution (particle size, IWC) from ER-2 multiple passes over the same cirrus region. Results from several good cases where the ER-2 flew over convection and then downwind over anvil cirrus in coordination with the DC-8 will be presented. We will apply particle size and IWC algorithms to the cirrus observations to evaluate whether the cirrus is undergoing changes.
A13C-1372
Vertical Structure and Variability of Ozone in the TTL From TC4 Ozonesondes
During the TC4 mission from July 13 through August 9,2007, ECC ozonesondes were launched from Alajuela, Costa Rica [10.0°N, 84.2°W], Las Tablas, Panama [7.8°N, 80.3°W] and San Cristobal in the Galapogos Islands [0.9°S, 89.6°W]. Here we examine 42 sondes that reached 25 km or higher. All of these sondes were accompanied by high-resolution temperature measurements from either RS80 or RS92 Vaisala radisondes, and most of the sondes also had GPS winds as well. Taken together, the ozone profiles display a rich fine structure and lamination in both the upper troposophere and in the lower stratosphere that in many instances can be linked to dynamical features induced in the temperature and wind fields by gravity waves and larger scale features. To characterize the typical structure of the profiles close to the tropopause we note that profile most often crosses the nominal stratospheric threshold mixing ratio of 100 ppbv within a few hundreds of meters of the first significant temperature minimum, either at the coded tropopause or just below it. Not all profiles are of this character and across the dataset the altitude at which the profiles first reach 100 ppbv varied from 13.7 km to 16.4 km . In several notable instances, such as the sounding at Alajuela at 06 UT on August 7, the coldpoint lay at 17 km atop a 3-km deep adiabatic layer with nearly constant ozone mixing ratio near the nominal threshold value, suggestive of a layer formed by mixing of stratospheric and tropospheric air. We use the ozone data in conjunction with the temperature and wind data to examine this and other cases for evidence of mixing and more purely dynamical processes.
A13C-1373
In Situ and Remote Measurements of Ice Particles in TC4
In situ microphysical measurements using cloud particle imager (CPI) and 2D-S probes were collected on both the NASA DC-8 and WB-57F during the recent TC4 field campaign. Additional data were collected using a CAPS cloud particle probe and other devices that measured cloud particle mass, including a CVI. When appropriate, these measurements are combined or compared in maritime and continental cirrus as a result of outflows from tropical convection near Costa Rica. The results, in terms of particle size distribution, extinction coefficient, optical depth, ice water content, ice water path and particle habit are compared with similar measurements in outflows from continental convection and synoptic cirrus observed over various regions in the United States. Particle shapes observed in the (cirrus) outflows from convection are distinctly different than cirrus formed in situ, whether it is formed at mid-latitudes or in the tropics. Cirrus formed in situ is characterized by ice particles with rosette shapes, whereas the outflow from convection contains mostly irregular shapes, plates and columns. However, once the outflow has aged for several hours, if it encounters regions with high ambient relative humidity (e.g., > 120% with respect to ice), then rosette ice shapes may be generated. Ice particles generated over the ocean do not appear to form "chains" of small ice crystals, such has been observed in strong convection with high electric fields over land. From radiation and modeling perspectives, it appears that particle shapes in synoptic cirrus and convective outflows can be predicted to first order if the life history of the particles is known; i.e., where the ice particles were formed and the history of their exposure to temperature and relative humidity. The issue of small ice crystals is considered in conjunction with a new remote sensing technique for determining the contribution of small ice in cirrus clouds. The principle of photon tunneling in anomalous diffraction theory is applied to the brightness temperature difference (BTD) between 10.8 and 12 microns. Since anomalous diffraction theory predicts an abrupt change in absorption efficiency factor between 10.8 and 12 microns when small ice particles are present, this signal can be used to remotely assess the contribution of small ice. Comparisons between in situ measurements and new 10.8 – 12 micron BTD remote sensing retrieval technique are presented and discussed. http://www.specinc.com
A13C-1374
Microphysical Properties of a Tropical Subvisible Cloud
Measurements of the microphysical properties of a very thin, tropical cirrus layer have been made as part of the NASA sponsored Tropical Composition, Clouds and Climate Coupling Experiment, (TC4), which was based in Costa Rica during July and August, 2007. The size distribution and water content were measured with two instruments, the Cloud, Aerosol and Precipitation Spectrometer (CAPS) and the Cloud Spectrometer and Impactor (CSI) that were mounted on the NASA WB57F. These instruments are upgraded versions of instruments previously flown on this aircraft and provide much more sensitivity to low levels of ice water content, greater accuracy of measurement in the 20-50 μm cloud particle range and less susceptibility to contamination from ice fragmentation. On August 6, 2007, the WB57F made a vertical profile through a 800 m cirrus cloud with an average temperature of -75° C. The ice crystal concentrations increased by a factor of 10 from cloud base to 400 m then remained almost constant over the remaining 400 m. The ice water contents also increased by a factor of ten from 0.1 to 1 mg m-3 over the lower 400 m then decreased again by a similar factor until reaching cloud top. The relationship between the number concentration and ice water content will be discussed in relation to the possible processes that could explain this link.
A13C-1375
An analysis of the synoptic situation during TC-4
During the TC-4 campaign, based in Costa Rica in July/August 2007, three different aircraft flew taking chemical and microphysical samples in the tropical region in the vicinity of Central and South America. In this study, we will analyze the meteorological origins of the air sampled, and compare the synoptic situation during 2007 to that of the past few years with NCAR/NCEP reanalysis output. In particular, there was a multi-day period where the southern hemisphere subtropical jet was unusually close to the equator. We will examine data from past years to determine if that was an anomalous occurrence, and what the impact was on the amount of mid latitude air present in the tropical upper troposphere.
A13C-1376
Sub-micron Aerosol Size Distributions in the Tropics: Implications for Stratospheric Aerosol Abundance
Dry aerosol size distributions in the diameter range from 4 to 1000 nm were measured in the NASA TC4 mission in Costa Rica in August 2007 from the NASA WB 57F to altitudes of approximately 18.3 km. Aerosol size distributions and profiles of integral parameters such as dry aerosol volume are compared with those measured from Costa Rica and Hawaii in the tropics in different seasons. Above the tropopause, the dry particles are assumed to be sulfuric acid, and the sulfuric acid mass loading is calculated and compared with the sulfuric acid mass loading in the mid and high latitude stratosphere. The scatter in the profile of dry aerosol volume below the tropopause is much greater than that above the tropopause, and the mixing ratio of sulfate aerosol mass increases with potential temperature above the tropopause. Stratospheric aerosol particles provide surface for heterogeneous chemistry important in determining the abundance of HOx, NOx and Clx in the stratosphere. These observations provide information on aerosol formation and transport in air entering the stratosphere in the tropics. Thus they contribute to our understanding of stratospheric aerosol abundance.