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[1] Diurnal variations in the troposphere are a source of the diurnal tides which are the prevalent dynamical phenomenon in the mesosphere and lower thermosphere. They are also discussed as contributing to the excitation of Rossby waves. Here we study diurnal variations of upper tropospheric and lower stratospheric winds (up to 22 km) over Japan from 1986 to 2008 mainly using data from the middle and upper atmosphere (MU) radar (34.85°N, 136.10°E) and JRA25/JCDAS data, as well as other four global reanalysis data sets (ERA40, ERA-Interim, NCEP1, and NCEP2) and output data from Global Scale Wave Model (GSWM). The diurnal and semidiurnal components are extracted and analyzed. For the diurnal wind component, the MU radar data are used to validate the reanalysis data, and the reanalysis data are chosen for the analysis. The diurnal amplitude monotonically increases with height above 15–20 km. The diurnal phase shows an upward progression up to 15 to 20 km, while above 15 to 20 km, it shows a downward progression in most months. It is found that the diurnal tide, defined as the diurnal component with absolute zonal wave numbers of ≤6, is dominant in the upper troposphere (explaining 60 to 80% of the variance) and in the stratosphere (explaining 80 to 90% of the variance). It is also observed that medium-scale waves contributed to the diurnal wind component in the upper troposphere from winter to spring (∼20% of the variance). For the semidiurnal wind component, only MU radar data are used for the analysis, which confirmed that the semidiurnal migrating tide is dominant through the troposphere and the lower stratosphere. The semidiurnal tidal amplitude shows a marked seasonal variation in the troposphere; the amplitude is largest in winter (∼0.4 m s−1) and smallest in summer (∼0.2 m s−1).

We investigated water vapor variations in the tropical lower stratosphere on seasonal, quasi-biennial oscillation (QBO), and decadal time scales using balloon-borne cryogenic frost point hygrometer data taken between 1993 and 2009 during various campaigns including the Central Equatorial Pacific Experiment (March 1993), campaigns once or twice annually during the Soundings of Ozone and Water in the Equatorial Region (SOWER) project in the eastern Pacific (1998-2003) and in the western Pacific and Southeast Asia (2001-2009), and the Ticosonde campaigns and regular sounding at Costa Rica (2005-2009). Quasi-regular sounding data taken at Costa Rica clearly show the tape recorder signal. The observed ascent rates agree well with the ones from the Halogen Occultation Experiment (HALOE) satellite sensor. Average profiles from the recent five SOWER campaigns in the equatorial western, Pacific in northern winter and from the three Ticosonde campaigns at Costa Rica (10degN) in northern summer clearly show two effects of the QBO. One is the vertical displacement of water vapor profiles associated with the QBO meridional circulation anomalies, and the other is the concentration variations associated with the QBO tropopause temperature variations. Time series of cryogenic frost point hygrometer data averaged in a lower stratospheric layer together with HALOE and Aura Microwave Limb Sounder data show the existence of decadal variations: The mixing ratios were higher and increasing in the 1990s, lower in the early 2000s, and probably slightly higher again or recovering after 2004. Thus linear trend analysis is not appropriate to investigate the behavior of the tropical lower stratospheric water vapor.

[1] Cirrus cloud variability associated with n = 0 eastward inertio-gravity equatorial waves and equatorial Kelvin waves (both with the period of ~4 days) and equatorial Kelvin wave with another periodicity (~16 days) were observed in the tropical Indian Ocean (8.0°S, 80.5°E) in November of 2011 during the Cooperative Indian Ocean experiment on intraseasonal variability in the Year 2011 (CINDY2011)/Dynamics of the Madden-Julian Oscillation (DYNAMO) field campaign using balloon-borne cryogenic frostpoint hygrometers, Vaisala radiosondes, and a shipborne high spectral resolution lidar system. During early to mid-November, the cirrus cloud appearance corresponded primarily with high supersaturation and high relative humidity caused by the temperature disturbances associated with the ~4 day waves between 12 km altitude and the cold-point tropopause. The cirrus clouds disappeared under the unfavorable (downward wind and dry) conditions that were caused by the ~4 day waves, although the ~16 day wave was generating favorable conditions. Our multi-instrument cirrus measurements revealed that we must consider the phases of various overlapping waves when estimating dehydration efficiency caused by cirrus clouds around the cold-point tropopause.

[1] Ozone and water vapor observations have been conducted at Christmas/Kiritimati Island (2°N, 157°W) in the equatorial central Pacific as a part of the Soundings of Ozone and Water in the Equatorial Region (SOWER)/Pacific mission. We launched 33 ozonesondes and 33 chilled-mirror hygrometers in nine observation campaigns from 1999 to 2003 for various seasons. We found that ozone concentrations at Christmas Island are low in the whole troposphere (∼10–35 ppbv), particularly in the marine boundary layer (MBL). Ozone variation is small throughout the year compared with other tropical stations, though annual and interannual variations of meteorological fields are large over the equatorial central Pacific. Just below the tropopause, during the August 2002 campaign, we observed substantially reduced ozone concentrations (

A number of field-campaigns in the tropics have been conducted in the recent years with two different LIDAR systems at Paramaribo in Suriname (5.8° N, 55.2° W). The lidars detect particles in the atmosphere with high vertical and temporal resolution and are capable of detecting extremely thin cloud layers which frequently occur in the tropical tropopause layer (TTL). Radiosonde as well as operational ECMWF analysis show that temperature anomalies caused by equatorial Kelvin waves propagate downward, well below the cold point tropopause (CPT). We find a clear correlation between the temperature anomalies introduced by these waves and the occurrence of thin cirrus in the TTL. In particular we found that extremely thin ice clouds form regularly where cold anomalies shift the tropopause to high altitudes. This finding suggests an influence of Kelvin wave activity on the dehydration in the TTL and thus on the global stratospheric water vapour concentration.

[1] Here we present extensive observations of stratospheric and upper tropospheric water vapor using the balloon-borne Cryogenic Frost point Hygrometer (CFH) in support of the Aura Microwave Limb Sounder (MLS) satellite instrument. Coincident measurements were used for the validation of MLS version 1.5 and for a limited validation of MLS version 2.2 water vapor. The sensitivity of MLS is on average 30% lower than that of CFH, which is fully compensated by a constant offset at stratospheric levels but only partially compensated at tropospheric levels, leading to an upper tropospheric dry bias. The sensitivity of MLS observations may be adjusted using the correlation parameters provided here. For version 1.5 stratospheric observations at pressures of 68 hPa and smaller MLS retrievals and CFH in situ observations agree on average to within 2.3% ± 11.8%. At 100 hPa the agreement is to within 6.4% ± 22% and at upper tropospheric pressures to within 23% ± 37%. In the tropical stratosphere during the boreal winter the agreement is not as good. The “tape recorder” amplitude in MLS observations depends on the vertical profile of water vapor mixing ratio and shows a significant interannual variation. The agreement between stratospheric observations by MLS version 2.2 and CFH is comparable to the agreement using MLS version 1.5. The variability in the difference between observations by MLS version 2.2 and CFH at tropospheric levels is significantly reduced, but a tropospheric dry bias and a reduced sensitivity remain in this version. In the validation data set a dry bias at 177.8 hPa of −24.1% ± 16.0% is statistically significant.

In the framework of the European Project STAR the mobile Aerosol Raman Lidar (MARL) of the Alfred Wegener Institute (AWI) was operated in Paramaribo/Suriname (5.8°, 55.2°W) and carried out extensive observations of tropical cirrus clouds during the fall dry season from September 28 to November 15 2004. With 81% the coverage with ice clouds was very high in the upper troposphere (above 12 km). The frequency of occurrence of subvisible clouds was found to be clearly enhanced compared to the midlatitudes. The extinction-to-backscatter ratio of thin tropical cirrus is with 26 ± 7 sr significantly higher than that of mid-latitude cirrus (16 ± 9 sr).Subvisible cirrus occur mostly in the tropical tropopause layer (TTL) abovean upper tropospheric inversion. The formation conditions of these cloudsand the dehydration of the TTL was investigated by means of a newly developed trajectory model. Clouds were assumed to occur when the relativehumidity above ice (RHI) exceeds 100% due to adiabatic cooling and subsequently the humidity is reduced to the saturation vapor pressure. This simple dehydration scheme yields an amazingly good agreement with cloud andhumidity observations at Paramaribo. However, it challenges the way cirrusformation is generally conceived, since high supersaturation were thoughtto be required. Our results suggest, that the inclination of the TTL to contain solid particles is rather high, even under modestly moist conditions. Wealso detected extremely thin layers of solid particles slightly above the temperature minimum in sub-saturated air which are possibly stabilized by HNO3.

[1] Simultaneous vertical profiles of cirrus cloud backscattering and frost point temperature were obtained for the first time in the tropopause region over Bandung, Indonesia, (6.9°S, 107.6°E). These profiles were measured by ground-based lidar and by balloon-borne Cryogenic Frost point Hygrometer (CFH) sondes. Supersaturation up to several ten percent was observed by the CFH just below the cold point tropopause at the altitude where a cirrus cloud was observed by lidar. The water vapor mixing ratio decreased slightly at the altitude of the cirrus cloud, suggesting that this decrease was caused by uptake in the cirrus cloud and that the water vapor reduction corresponds to the lower limit of the cloud water content of the observed cirrus cloud. Theoretical calculations of the scattering parameters for the observed cirrus cloud particles and estimations of the time constants for sedimentation and for condensational growth indicate that particles size range is between 4 μm and 30 μm.

We estimate the tropospheric column ozone using a forward trajectory model to increase the horizontal resolution of the Aura Microwave Limb Sounder (MLS) derived stratospheric column ozone. Subtracting the MLS stratospheric column from Ozone Monitoring Instrument total column measurements gives the trajectory enhanced tropospheric ozone residual (TTOR). Because of different tropopause definitions, we validate the basic residual technique by computing the 200-hPa-to-surface column and comparing it to the same product from ozonesondes and Tropospheric Emission Spectrometer measurements. Comparisons show good agreement in the tropics and reasonable agreement at middle latitudes, but there is a persistent low bias in the TTOR that may be due to a slight high bias in MLS stratospheric column. With the improved stratospheric column resolution, we note a strong correlation of extratropical tropospheric ozone column anomalies with probable troposphere-stratosphere exchange events or folds. The folds can be identified by their colocation with strong horizontal tropopause gradients. TTOR anomalies due to folds may be mistaken for pollution events since folds often occur in the Atlantic and Pacific pollution corridors. We also compare the 200-hPa-to-surface column with Global Modeling Initiative chemical model estimates of the same quantity. While the tropical comparisons are good, we note that chemical model variations in 200-hPa-to-surface column at middle latitudes are much smaller than seen in the TTOR.

Water vapor observations by chilled-mirror hygrometers were conducted at Bandung, Indonesia (6.90° S, 107.60° E) and Tarawa, Kiribati (1.35° N, 172.91° E) in December 2003 to examine the efficiency of dehydration during horizontal advection in the tropical tropopause layer (TTL). Trajectory analyses based on bundles of isentropic trajectories suggest that the modification of air parcels' identity due to irreversible mixing by the branching-out and merging-in of nearby trajectories is found to be an important factor, in addition to the routes air parcels follow, for interpreting the water vapor concentrations observed by chilled-mirror frostpoint hygrometers in the TTL. Clear correspondence between the observed water vapor concentration and the estimated temperature history of air parcels is found showing that drier air parcels were exposed to lower temperatures than were more humid ones during advection. Although the number of observations is quite limited, the water content in the observed air parcels on many occasions was more than that expected from the minimum saturation mixing ratio during horizontal advection prior to sonde observations.

Water vapor sonde observations were conducted at Bandung, Indonesia (6.90 S, 107.60 E) and Tarawa, Kiribati (1.35 N, 172.91 E) in December 2003 to examine the efficiency of the "cold trap'' dehydration in the tropical tropopause layer (TTL). Trajectory analysis based on bundles of trajectories suggest that the modification of air parcels' identity due to irreversible mixing by the branching-out and merging-in of nearby trajectories is found to be an important factor, in addition to the routes air parcels are supposed to follow, for interpreting the water vapor concentrations observed by radiosondes in the TTL. Clear correspondence between the observed water vapor concentration and the estimated temperature history of air parcels is found showing that dry air parcels are exposed to low temperatures while humid air parcels do not experience cold conditions during advection, in support of the "cold trap'' hypothesis. It is suggested that the observed air parcel retained the water vapor by roughly twice as much as the minimum saturation mixing ratio after its passage through the "cold trap,'' although appreciable uncertainties remain.

[1] Shipboard radiosonde measurements revealed a persistent temperature inversion layer with a thickness of ∼200 m at 12–13 km in a nonconvective region over the tropical eastern Pacific, along 2°N, in September 1999. Simultaneous relative humidity measurements indicated that the thin inversion layer was located at the top of a very wet layer with a thickness of 3–4 km, which was found to originate from the intertropical convergence zone (ITCZ) to the north. Radiative transfer calculations suggested that this upper tropospheric inversion (UTI) was produced and maintained by strong longwave cooling in this wet layer. A strong easterly jet stream was also observed at 12–13 km, centered around 4°–5°N. This easterly jet was in the thermal wind balance, with meridional temperature gradients produced by the cloud and radiative processes in the ITCZ and the wet outflow. Furthermore, the jet, in turn, acted to spread inversions further downstream through the transport of radiatively active water vapor. This feedback mechanism may explain the omnipresence of temperature inversions and layering structures in trace gases in the tropical troposphere. Examination of high-resolution radiosonde data at other sites in the tropical Pacific indicates that similar UTIs often appear around 12–15 km. The UTI around 12–15 km may thus be characterized as one of the “climatological” inversions in the tropical troposphere, forming the lower boundary of the so-called tropical tropopause layer, where the tropospheric air is processed photochemically and microphysically before entering the stratosphere.

[1] In the paper “Kelvin-Helmholtz instability around the tropical tropopause observed with the Equatorial Atmosphere Radar” by Masayuki K. Yamamoto, Masatomo Fujiwara, Takeshi Horinouchi, Hiroyuki Hashiguchi, and Shoichiro Fukao (Geophys. Res. Lett., 30(9), 1476, doi:10.1029/2002GL016685, 2003), several corrections to the proof were omitted from the final published article. The corrected text appears below.

(1) The first view of stratospheric and tropospheric ozone variability in the Southern Hemisphere tropics is provided by a 3-year record of ozone soundings from the Southern Hemisphere Additional Ozonesondes (SHADOZ) network (http://croc.gsfc.nasa.gov/ shadoz). Observations covering 1998-2000 were made over Ascension Island, Nairobi (Kenya), Irene (South Africa), Reunion Island, Watukosek (Java), Fiji, Tahiti, American Samoa, San Cristobal (Galapagos), and Natal (Brazil). Total, stratospheric, and tropospheric column ozone amounts usually peak between August and November. Other features are a persistent zonal wave-one pattern in total column ozone and signatures of the quasi-biennial oscillation (QBO) in stratospheric ozone. The wave-one is due to a greater concentration of free tropospheric ozone over the tropical Atlantic than the Pacific and appears to be associated with tropical general circulation and seasonal pollution from biomass burning. Tropospheric ozone over the Indian and Pacific Oceans displays influences of the waning 1997-1998 El Nino, seasonal convection, and pollution transport from Africa. The most distinctive feature of SHADOZ tropospheric ozone is variability in the data, e.g., a factor of 3 in column amount at 8 of 10 stations. Seasonal and monthly means may not be robust quantities because statistics are frequently not Gaussian even at sites that are always in tropical air. Models and satellite retrievals should be evaluated on their capability for reproducing tropospheric variability and fine structure. A 1999- 2000 ozone record from Paramaribo, Surinam (6� N, 55� W) (also in SHADOZ) shows a marked contrast to southern tropical ozone because Surinam is often north of the Intertropical Convergence Zone (ITCZ). A more representative tropospheric ozone climatology for models and satellite retrievals requires additional Northern Hemisphere tropical data. INDEXTERMS: 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 1640 Global Change: Remote sensing; 3309 Meteorology and Atmospheric Dynamics: Climatology (1620); 9305 Information Related to Geographic Region: Africa; 9325 Information Related to Geographic Region: Atlantic Ocean; KEYWORDS: Free-words-ozone, tropospheric ozone, ozonesondes, satellite ozone, tropical climatology, wave-one, biomass burning, El Nino, satellite retrievals

[1] Balloon-borne observations of frost-point temperature and ozone in the equatorial western, central and eastern Pacific as well as over equatorial eastern Brazil provide a highly accurate data set of water vapor across the tropical tropopause. Data were obtained at San Cristobal, Galapagos, Ecuador (0.9°S, 89.6°W), during the late northern winter and the late northern summer in 1998 and 1999 and at Juazeiro do Norte, Brazil (7.2°S, 39.3°W), in February and November 1997. Earlier data in the western Pacific region in March 1993 were reanalyzed to extend the scope of the observations. The data show three different circumstances in which saturation or supersaturation occurs and imply different mechanisms for dehydration at the tropical tropopause: (1) convective dehydration, (2) slow-ascent dehydration, and (3) large-scale wave-driven dehydration. Furthermore, air that crosses the tropical tropopause in the late northern summer may be dehydrated further during late northern fall, as the average tropical tropopause rises and cools. Not all soundings show dehydration, and there are clear differences in the frequency and depth of saturation in different regions and seasons. The tropopause transition region can be identified in accurate measurements of relative humidity, even under conditions where ozone observations are ambiguous. Deep convection plays an important role in setting up this transition region, which is then subject to large-scale wave activity and wave breaking at the tropopause or midlatitude intrusions. High relative humidities over regions of strong subsidence show that descending motion in the troposphere is limited to levels below the transition region.

[1] The relationship between relative humidity and cirrus clouds in the tropical tropopause layer (TTL) is investigated using balloon-borne cryogenic frostpoint hygrometers (CFH) and quasi-collocated measurements of space-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) over Biak (1.17°S, 136.06°E) and Kototabang (0.20°S, 100.32°E) both in Indonesia in Januaries 2007 and 2008. At Kototabang, thin layers of high supersaturation, up to ∼160% in relative humidity with respect to ice (RHi), are often observed co-existing with cirrus clouds at altitudes of ∼15–18 km. At Biak, RHi inside cirrus is around 100% or less without large supersaturation layers, and most clouds are limited to altitudes below 16 km. We found that the presence and the degree of supersaturation may strongly depend on the phases of large-scale disturbances such as the MJO rather than geographical difference.

[1] An aerosol layer was found 1–2 km around the tropical cold point tropopause by observations using ground-based lidar and balloon-borne optical particle counters (OPC) over Biak, Indonesia, in January 2011. The layer was observed throughout the survey period from 6 to 13 January. The backscattering coefficient of the layer was about 5 times larger than that of the background aerosols. The lidar-observed depolarization ratio of the layer was very low, and the wavelength dependence of the backscattering coefficients of the layer was similar to that of stratospheric aerosols. A layer of the particles at the size of the accumulation mode was also observed by an OPC at ambient temperature, but the particles were volatile at 200°C. These properties indicate that the aerosol layer was composed of liquid phase aqueous sulfuric acid solution particles and probably originated from a volcanic eruption. It was observed by lidar that a thin cirrus cloud layer appeared within this aerosol layer. Backward trajectory analysis and satellite-observed equivalent blackbody temperature indicate that the cirrus cloud layer probably formed in situ. The estimated upper limit of the number concentration of cloud particles was 105 m−3. The number concentration of the volatile aerosol particles (∼3 × 106 m−3) was 30 times larger than this upper limit. This upper limit, however, is comparable to the aerosol particle concentration observed by the OPC at 200°C. These results are consistent with the cirrus cloud formation with solid sulfate particles in tropical upper troposphere suggested by previous studies.

International audience; The performance of 18 coupled Chemistry Climate Models (CCMs) in the Tropical Tropopause Layer (TTL) is evaluated using qualitative and quantitative diagnostics. Trends in tropopause quantities in the tropics and the extratropical Upper Troposphere and Lower Stratosphere (UTLS) are analyzed. A quantitative grading methodology for evaluating CCMs is extended to include variability and used to develop four different grades for tropical tropopause temperature and pressure, water vapor and ozone. Four of the 18 models and the multi‐model mean meet quantitative and qualitative standards for reproducing key processes in the TTL. Several diagnostics are performed on a subset of the models analyzing the Tropopause Inversion Layer (TIL), Lagrangian cold point and TTL transit time. Historical decreases in tropical tropopause pressure and decreases in water vapor are simulated, lending confidence to future projections. The models simulate continued decreases in tropopause pressure in the 21st century, along with ∼1K increases per century in cold point tropopause temperature and 0.5–1 ppmv per century increases in water vapor above the tropical tropopause. TTL water vapor increases below the cold point. In two models, these trends are associated with 35% increases in TTL cloud fraction. These changes indicate significant perturbations to TTL processes, specifically to deep convective heating and humidity transport. Ozone in the extratropical lowermost stratosphere has significant and hemispheric asymmetric trends. O3 is projected to increase by nearly 30% due to ozone recovery in the Southern Hemisphere (SH) and due to enhancements in the stratospheric circulation. These UTLS ozone trends may have significant effects in the TTL and the troposphere.

[1] The dynamical characteristics of the tropical tropopause layer (TTL) are investigated using the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) run on the Earth Simulator under an aqua planet condition. Two experiments are performed: one with a 3.5 km horizontal spacing and a three-dimensional snapshot output and another with a 7 km horizontal spacing and 3-hourly averages for 1 month. The number of vertical levels is 54 and the model top is at 40 km; the vertical spacing in and around the TTL is ∼700 m. Large-scale organized convection associated with convectively coupled equatorial Kelvin waves prevails around the equator. The zonal mean vertical distribution of cloud top height near the equator shows a realistic trimodal structure. The simulation results reveal that cumulus clouds penetrate the lapse-rate tropopause and the bottom boundary of the TTL (defined as the lapse rate minimum) for ∼0.1% and ∼25%, respectively, in the equatorial area. The frequency distribution of vertical wind may provide a good indicator of the TTL bottom boundary. A significant reduction in the speed of strong vertical winds is observed at ∼16 km. High variability in temperature and the water vapor mixing ratio observed around the tropopause is mainly caused by equatorial Kelvin waves generated by the organized convection in these experiments. Horizontal variability in tropopause height over a large-scale convective system is much smaller than that in the area of Kelvin waves. The gravity waves generated by this large-scale convective system locally control the temperature around the tropopause. In addition, large-amplitude gravity waves with a scale of 600 km are superimposed on the cold phase of Kelvin waves, producing one of the coldest regions around the tropopause. It is suggested that the combination of Kelvin waves and gravity waves may be one of the most effective dehydration processes in the TTL.

[1] A polarization lidar was continuously operated aboard the research vessel Mirai in the tropical western Pacific over three northern winters: at 2.0°N, 138.0°E during November and December 2001; at 2.0°N, 138.5°E during November and December 2002; and at 7.5°N, 134.0°E during December 2004 and January 2005. Intensive radiosonde soundings were made from the vessel at 3-h intervals during all three campaigns. The mechanisms that underlie the observed variations in cirrus in the tropical tropopause layer (TTL) are discussed from the viewpoint of large-scale dynamics and transport. During the 2001 campaign, the tropopause region was cold, but the TTL was often clear, with only some subvisual cirrus. Potential vorticity data and trajectories show that the TTL during this period was strongly affected by dry air transport from the northern midlatitude lower stratosphere. During the 2002 campaign, a packet of large-amplitude equatorial Kelvin waves was the primary control on the generation and disappearance of cirrus in the TTL. During the 2004–2005 campaign, a cold phase of large-scale waves resulted in cirrus generation in the TTL in late December of 2004, similar to that observed during the 2002 campaign. Outflow from the South Pacific Convergence Zone (SPCZ) caused optically thick cirrus in the TTL, particularly during early January 2005, when we also observed regular diurnal variations in cirrus development within the TTL, that is, apparent sedimentation during the nighttime. We investigated two possible controlling processes, namely, horizontal advection together with diurnal variations in convective activity within the SPCZ and diurnal variations in local temperature due to tides and gravity waves. In the equatorial western Pacific, equatorial Kelvin waves are the important dynamical process that controls cirrus variations in the TTL. Dry-air horizontal transport from the midlatitude lower stratosphere and wet-air vertical transport near the tropical convergence regions should also be considered in fully explaining the cirrus observations in the TTL.

We present validation studies of MLS version 2.2 upper tropospheric and stratospheric ozone profiles using ozonesonde and lidar data as well as climatological data. Ozone measurements from over 60 ozonesonde stations worldwide and three lidar stations are compared with coincident MLS data. The MLS ozone stratospheric data between 150 and 3 hPa agree well with ozonesonde measurements, within 8% for the global average. MLS values at 215 hPa are biased high compared to ozonesondes by A`20% at middle to high latitude, although there is a lot of variability in this altitude region. Comparisons between MLS and ground-based lidar measurements from Mauna Loa, Hawaii, from the Table Mountain Facility, California, and from the Observatoire de Haute-Provence, France, give very good agreement, within A`5%, for the stratospheric values. The comparisons between MLS and the Table Mountain Facility tropospheric ozone lidar show that MLS data are biased high by A`30% at 215 hPa, consistent with that indicated by the ozonesonde data. We obtain better global average agreement between MLS and ozonesonde partial column values down to 215 hPa, although the average MLS values at low to middle latitudes are higher than the ozonesonde values by up to a few percent. MLS v2.2 ozone data agree better than the MLS v1.5 data with ozonesonde and lidar measurements. MLS tropical data show the wave one longitudinal pattern in the upper troposphere, with similarities to the average distribution from ozonesondes. High upper tropospheric ozone values are also observed by MLS in the tropical Pacific from June to November.

[1] The Intertropical Convergence Zone (ITCZ) passes twice a year over tropical Suriname, bringing two wet and two dry seasons. During a pilot study campaign in Suriname, cirrus clouds were observed with a mobile aerosol Raman lidar (MARL) and with balloon sondes containing a frost point hygrometer called Snow White, over the period October–November 2004. These observations are used to study the origin of cirrus clouds and the dynamical processes that determine their transport, using European Centre for Medium-Range Weather Forecasts (ECMWF) operational analyses. The height of cirrus occurrence is in phase with the height of the cold point tropopause, with maximum heights occurring during Northern Hemisphere winter that are about 2 km above the minimum values in summertime. The occurrence of cirrus often corresponds with a northerly meridional wind flow (in a layer underneath the tropopause), also when the ITCZ lies to the south in the period January–May. ECMWF analyses point out that inertial instability flow, in the form of vertically stacked meridional circulation cells in the upper troposphere (UT), can explain the transport of these cirrus events. Also evident is that radiative cooling of a moist layer transported in the UT leads to a thermal wind in the form of an easterly/westerly jet associated with the southward/northward transport of moist air. An interactive play between the inertial instability and thermal wind mechanisms explains many of the observed features of cirrus occurrence over Suriname. The observed cirrus mostly originates from the ITCZ or from deep convective centers to the south that form during the early summer monsoon.

[1] Turbulent diffusivity and turbulent ozone fluxes in the tropo-stratosphere are studied employing simultaneous observations with the Middle and Upper (MU) Atmosphere radar and ozonesondes in Shigaraki, Japan during April 16–24, 1998. A broad region around the tropopause was dynamically active. Maxima of turbulent diffusivity were observed at 8–14 km altitude. Such maxima may produce vertical turbulent ozone fluxes across the tropopause with magnitudes comparable to those required for the global ozone budget. Meso-meteorological ozone intrusions may enhance the fluxes.

[1] Bromoform (CHBr 3 ), dibromochloromethane (CHBr 2 Cl), and dibromomethane (CH 2 Br 2 ) in the atmosphere were measured at various sites, including tropical islands, the Arctic, and the open Pacific Ocean. Up to 40 ppt of bromoform was observed along the coasts of tropical islands under a sea breeze. Polybromomethane concentrations were highly correlated among the coastal samples, and the ratios CH 2 Br 2 /CHBr 3 and CHBr 2 Cl/ CHBr 3 showed a clear tendency to decrease with increasing CHBr 3 concentration. These findings are consistent with the observations that polybromomethanes are emitted mostly from macroalgae whose growth is highly localized to coastal areas and that CHBr 3 has the shortest lifetime among these three compounds. The relationship between the concentration ratios CHBr 3 /CH 2 Br 2 and CHBr 2 Cl/CH 2 Br 2 suggested a large mixing/ dilution effect on bromomethane ratios in coastal regions and yielded a rough estimate of 9 for the molar emission ratio of CHBr 3 /CH 2 Br 2 and of 0.7 for that of CHBr 2 Cl/CH 2 Br 2 . Using these ratios and an global emission estimate for CH 2 Br 2 (61 Gg/yr (Br)) calculated from its background concentration, the global emission rates of CHBr 3 and CHBr 2 Cl were calculated to be approximately 820(±310) Gg/yr (Br) and 43(±16) Gg/yr (Br), respectively, assuming that the bromomethanes ratios measured in this study are global representative. The estimated CHBr 3 emission is consistent with that estimated in a very recent study by integrating the sea-to-air flux database. Thus the contribution of CHBr 3 and CHBr 2 Cl to inorganic Br in the atmosphere is likely to be more important than previously thought.

[1] The radiation balance of the tropical tropopause layer (TTL) is examined using several different radiation codes with standard profiles compiled from observations in the tropics assuming clear sky conditions. These codes include detailed radiative transfer models and simplified codes for global climate models. The importance of the various radiatively active gases are examined. Water vapor is the most important contributor to the TTL radiation balance, but carbon dioxide and ozone also play a role. Differences in radiative heating between radiation models are mostly due to treatments of shortwave radiation. Differences between models below the TTL are due to different treatments of water vapor continuum absorption. The level of zero clear sky radiative heating, a level important for understanding the transport of air into the stratosphere, is generally found near 15 km, 125 hPa and 200°K (360 K potential temperature), consistent with previous work. Changes in time and space can modify this level by ±500 m, and individual profiles vary from these averages by ±400 m (1σ). Increases in water vapor in the TTL would tend to increase the altitude of the level at which the net heating is zero, while increases in carbon dioxide or ozone would tend to decrease this level. Clouds in the TTL tend to increase the level due to enhancements in longwave cooling above clouds. The implications for transport are discussed.

[1] In November 2001, the Equatorial Atmosphere Radar (0.20°S, 100.32°E) observed a continuous strong eastward wind shear (10–50 m s−1 km−1), westward wind (2–27 m s−1), and the radar echo layer tilted downward to the west in the region 0–1 km above the tropopause. During the same period, the Richardson number calculated with hourly-averaged horizontal wind and radiosonde temperature data was almost continuously

[1] The Equatorial Atmosphere Radar (EAR) installed in Sumatra Island, Indonesia, observed significant enhancement of turbulence in the tropopause region, 15–17 km, intermittently for ∼5 days in November 2001. The turbulence intensity was estimated with the spectral width of the radar echo power spectrum, and the turbulence during the period was a factor of up to ∼5 larger in kinetic energy than that in other periods. Further analyses confirm that the enhanced turbulence was convectively generated in the breaking phase of an equatorial Kelvin wave. Between July and December 2001, we observed at least three more prominent cases of the turbulence generation by breaking Kelvin waves in the tropopause region.

[1] A network of 10 southern hemisphere tropical and subtropical stations, designated the Southern Hemisphere Additional Ozonesondes (SHADOZ) project and established from operational sites, provided over 1000 ozone profiles during the period 1998–2000. Balloon-borne electrochemical concentration cell (ECC) ozonesondes, combined with standard radiosondes for pressure, temperature, and relative humidity measurements, collected profiles in the troposphere and lower to midstratosphere at: Ascension Island; Nairobi, Kenya; Irene, South Africa; Reunion Island; Watukosek, Java; Fiji; Tahiti; American Samoa; San Cristobal, Galapagos; and Natal, Brazil. The archived data are available at: 〈http://croc.gsfc.nasa.gov/shadoz〉.1 In this paper, uncertainties and accuracies within the SHADOZ ozone data set are evaluated by analyzing: (1) imprecisions in profiles and in methods of extrapolating ozone above balloon burst; (2) comparisons of column-integrated total ozone from sondes with total ozone from the Earth-Probe/Total Ozone Mapping Spectrometer (TOMS) satellite and ground-based instruments; and (3) possible biases from station to station due to variations in ozonesonde characteristics. The key results are the following: (1) Ozonesonde precision is 5%. (2) Integrated total ozone column amounts from the sondes are usually to within 5% of independent measurements from ground-based instruments at five SHADOZ sites and overpass measurements from the TOMS satellite (version 7 data). (3) Systematic variations in TOMS-sonde offsets and in ground-based-sonde offsets from station to station reflect biases in sonde technique as well as in satellite retrieval. Discrepancies are present in both stratospheric and tropospheric ozone. (4) There is evidence for a zonal wave-one pattern in total and tropospheric ozone, but not in stratospheric ozone.

[1] An intensive observation with ozonesondes, radiosondes, and the Middle and Upper atmosphere (MU) radar was conducted at Shigaraki (34.9°N, 136.1°E), Japan, from 16 through 24 April 1998 to investigate the formation mechanism of ozone laminae in the midlatitude lower stratosphere. In these observations the temporal variation of an ozone lamina at Shigaraki was continuously observed through a short time interval of 8 hours. During the observation period an ozone lamina with a thickness of 2–3 km appeared and ascended with a speed of ∼1 km day−1 in the height region of 18–21 km. It is deduced that inertia gravity waves existing in this height region did not contribute to formation of the ozone lamina, because their amplitudes were too small and their vertical phase propagation was in the opposite direction. The reverse domain filling method was used to reconstruct the “high-resolution” modified potential vorticity field using backward trajectory calculations. The results indicate that this ozone lamina was caused by differential advection due to the vertical shear associated with the subtropical westerly jet and embedded stationary Rossby wave therein. This means that large-scale motions concurrent with vertical wind shear can produce much smaller-scale structures in material fields than those of the large-scale motions themselves.

Ionospheric winds required to produce the lunar daily geomagnetic variations are deduced from the atmospheric dynamo theory that takes into account the electric linkage between conjugate points in the northern and southern hemispheres. The electrical conductivity of the ionosphere is first estimated on the basis of atmospheric and ionospheric models for a moderate state of solar activity, and wind systems are then calculated separately for two supposed current layers (thick and thin) and also for three different seasons (D, E and J months). It is found that the amplitudes of wind velocities in middle latitudes are about 10 m/sec for the thick layer and about 15 m/sec for the thin layer, and that the phases are such that the wind systems have two sources around 9 hr and 21 hr and two sinks around 3 hr and 15 hr in lunar time. There is a tendency that the amplitudes of winds are a little larger in winter than in summer, and the phases are advanced systematically from summer to winter. The results are discussed by comparing with other theoretical and observational results, and suggest a purely tidal origin of the lunar daily geomagnetic variations.

Tropical instability waves (TIWs), with a typical wavelength of 1000 km and period of 30 days, cause the equatorial front to meander and result in SST variations on the order of 18–28C. Vertical soundings of temperature, humidity, and wind velocity were obtained on board a Japanese research vessel, which sailed through three fully developed SST waves from 1408 to 1108W along 28N during 21–28 September 1999. A strong temperature inversion is observed throughout the cruise along 28N, capping the planetary boundary layer (PBL) that is 1– 1.5 km deep. Temperature response to TIW-induced SST changes penetrates the whole depth of the PBL. In response to an SST increase, air temperature rises in the lowest kilometer and shows a strong cooling at the mean inversion height. As a result, this temperature dipole is associated with little TIW signal in the observed sea level pressure (SLP). The cruise mean vertical profiles show a speed maximum at 400–500 m for both zonal and meridional velocities. SST-based composite profiles of zonal wind velocity show weakened (intensified) vertical shear within the PBL that is consistent with enhanced (reduced) vertical mixing, causing surface wind to accelerate (decelerate) over warm (cold) SSTs. Taken together, the temperature and wind soundings indicate the dominance of the vertical mixing over the SLP-driving mechanism. Based on the authors’ measurements, a physical interpretation of the widely used PBL model proposed by Lindzen and Nigam is presented.