Table 1 DOAS spectral analysis details for the various trace gases and their spectral fitting intervals. Refer to Table 2 for the corresponding fitted absorbers. The solar I 0 correction used is suggested in Aliwell et al. A summary of the trace gases and details of their absorption cross sections used for the DOAS analysis can be found in Tables 1 and 2.
The dSCDs of each gas are calculated using an in-flight Fraunhofer reference spectrum, which is the same for the scaling and target gas e. When inspecting the O 3 vs. For the retrieval of VMRs at flight altitude, the recently developed O 3 scaling method is used, the details of which are discussed in Stutz et al. For this method, the radiative transfer of each limb measurement is modeled using McArtim Deutschmann et al.
The a priori profile shapes of the scaling and target gases are taken from simulated trace gas VMR curtains along the flight track modeled by CLaMS see Sect. This was done previously in Werner et al. These adjusted profiles are used by the RT model to calculate the trace gas absorption in the line-of-sight to the total absorption, i.
Lastly, to retrieve the trace gas VMRs [ X ] j in an atmospheric layer j i. The scaling method virtually compensates for any effects of the light path length modifications e. The VMR of the target gas, [ X ] j , for these limb UV—Vis measurements is an average over a given atmospheric volume based on the distance the aircraft has traveled during a single measurement, over the FOV of the telescope to the right of the aircraft, and the light path length in the current conditions for examples, see Figs.
The CL sensor detects light emission from the reaction of O 3 with an organic dye, coumarin e. The CL response is calibrated by the UV photometer, thus combining the accuracy of a UV photometer with the high measurement frequency of a CL detector.
The mean age of air can be inferred from SF 6 measurements only if a single entry point can be assumed. As air masses observed during this study, i. Instead we use so-called lag time here, i. In addition, SF 6 data are smoothed using a local correlation with the CFC data an atmospheric transport tracer which has a higher precision. A total of 10 data points surrounding the measurement on both sides are used to determine the local correlation for each data point.
This procedure retains the local information without introducing an offset to SF 6 mixing ratios and removes some instrumental scatter. The lag time derived in this way has an overall precision better than 0.
In particular, close to the TP, observed mixing ratios are often higher than those in the reference time series, resulting in negative lag times. The second channel measures bromocarbons and other halogenated species with cryogenic enrichment Obersteiner et al.
This correlation leads to a scaling of The instrument is in situ-calibrated against secondary standards, which are compared to NOAA primary standards before and after the campaign. These tracers are used for the interpretation of air mass transport around the UTLS during this study. CLaMS is particularly good at portraying the gradients of trace gases and the transport of air parcels, especially in the region of transport barriers, for example near the extratropical tropopause Ex-TP due to its Lagrangian nature e.
Also, only long-lived Br y inorg is part of the simulation, and bromine compounds from VSLS are considered to already be converted to Br y inorg. Trace gas curtains along the flight tracks have been derived for each flight of the WISE campaign. These curtains are defined by the latitude, longitude, and time of the flight track for many altitudes. The chemical composition from the 3-D CLaMS simulation is then interpolated to the trajectory endpoints; subsequently the CLaMS chemistry is calculated forward in time along these trajectories to determine the chemical composition along the given curtain.
In this study we use two different kinds of artificial tracers. The first kind is an artificial air mass origin tracer initialized on 1 May approximately 5 months prior to the WISE campaign. The air mass origin tracers mark nine distinct 3-D domains in the entire model atmosphere: the tropical troposphere, upper and lower TTL, tropical pipe, midlatitudinal troposphere and LMS, polar troposphere and LMS, and lastly the stratospheric background.
These are used to study vertical and horizontal transport of these air masses to the LMS in the NH within 5 months. Divisions of the air mass origin domains are described in further detail in Table 1 and Fig. A prior test flight RF01 is not included in this study. The first research flight, RF02, was conducted locally from the home base in Oberpfaffenhofen, Germany, and all subsequent flights were based from Shannon, Ireland, aside from the transfer flights.
The flights illustrated by the dashed lines, i. The second kind is an artificial tracer that marks specific regions in the CLaMS model boundary layer referred to as surface emission tracers, and these are used here to study the transport of young air masses into the LMS in the NH. The surface emission tracers are divided into 24 surface regions see Fig. Moreover, in this study, the entire Earth's surface is covered by surface emission tracers. For some regions, coastlines or orography both provided by ECMWF are used as criteria to define the boundaries between different regions.
The same setup for the surface emission tracers was already used for WISE measurements in Wetzel et al. In the setup used here, the model employs a hybrid vertical coordinate with terrain-following sigma levels near the surface and pressure levels at higher altitudes. Large-scale vertical motion is calculated from the divergence of the horizontal winds. The O 3 loss reactions are described in Werner et al. The simulations used here were initialized from a multidecadal control simulation which started in Dhomse et al.
Output from this run on 1 January was used to initialize a series of sensitivity runs. Initial constraints for the brominated species in the UT are given in Table 3.
We have performed three different TOMCAT sensitivity runs from January a base run followed by two runs with elevated bromine constraints. The additional two runs continue to use the Ex-TP conditions in the extratropics, while elevated bromine in the form of Br VSLS and Br y inorg is initialized in the tropical UT for two differing scenarios.
Comparison of the model runs allows for the diagnosis of the impact of the differing bromine levels on the O 3 levels in this region. Specific topics of interest during WISE include the transport pathways, timescales, and mixing processes affecting the late summer and fall in the UTLS. The potential temperature of the flight trajectory and WMO TP solid and dashed black lines, respectively and equivalent latitude solid blue line, right axis are shown in a.
Dark gray shading indicates flight sections in the high bromine region HBrR between eq. The flight tracks are shown in Fig. The measurement region ranged from longitudes of The equivalent latitude describes an enclosed area relative to the area of the globe of specific potential vorticity on a given potential temperature contour and is a useful quasi-Lagrangian coordinate for the interpretation of tracers in the stratosphere Pan et al. The majority of the flight time was spent at altitudes between 8.
Panels a—g are as given in Fig. Two flights are chosen as examples. The first sample flight, RF04, on 20 September , consisted of two different length, but overlapping, rectangular shuttles northeast of Ireland up the Scandinavian coast, over the Norwegian Sea, and only briefly crossing land masses over the United Kingdom and Ireland see Figs.
The flight track reached a maximum latitude of The final stretch back to Shannon was flown at the highest altitude during this flight of The negative mean air mass lag times are due to higher SF 6 VMRs near the NH source regions compared to the global mean and in particular in the upper levels of the tropical TP region.
This flight is chosen as a sample flight of Br tot mixing ratios near the LS campaign average, as well as flight segments within the LMS region with elevated bromine, indicated by the dark gray shading discussed in Sect. This flight consisted of two overlapping rectangular shuttles southwest of Ireland over the Celtic Sea and North Atlantic Ocean see Figs. The latitudes ranged from The highest altitude during this flight was Measurements from near the surface during takeoff or landing, i.
Complementary measurements and insight for a suite of sources gases and studies of the dynamics, potential vorticity, baroclinic waves, and isentropic mixing of the region have been reported elsewhere for flights during the WISE campaign e.
Br tot ranges from The variability is partly due to the different origins of the air masses and various inferred mean air mass lag times which have a spread of more than 3 years. The trend is suspected to now be decreasing by - 0. Furthermore, our results fit well into the expectation based on the total amount of stratospheric Br tot , published earlier by our group from different measurements e.
CH 3 Br contribution 1 to Br tot is destroyed with increasing distance into the stratosphere at a slow rate from 7. The tropospheric CH 3 Br 7. Although further into the stratosphere the Br org is destroyed, bromine is converted to Br y inorg and is compensated for in the Br tot budget.
Contribution 4 to Br tot , the Br y inorg , near the TP is around 1. In the LS the weighted mean Br tot ranges from These small changes from the LS Br tot weighted mean of Only 11 flights have Br org measurements available, resulting in a sparser distribution.
The maximum mean Br y inorg VMR is 8. These results agree well with previous studies, such as Werner et al. A modeling study by Schmidt et al. Figure 6 Frequency distribution of inferred total Br tot. The gray lines are constant potential temperature isentropes. The dark red arrows show regions of strong convection transporting surface air masses from bromine source regions to the UT.
Older air see Fig. There, a small pocket of older air with lag times larger than 1 year has low Br org and Br y inorg.
Here, the relative change of the mean air mass lag times greater than 3 years is more relevant in the context of our study. Of particular interest is the region in the LMS at middle to high equivalent latitudes where Br tot local grid means of up to A frequency distribution of inferred Br tot is displayed in Fig.
The distribution of the Br tot in the HBrR brown as compared to the rest of the LS excluding the HBrR blue shows the characteristically significant increase of bromine in this region Fig. The HBrR measurements result in the bromine bulge noticeable in Fig. Potential sources include other regions of elevated bromine larger than the LS average, such as from the tropical and extratropical troposphere.
These regions have younger tropospheric air masses which correspond well with the relatively younger air masses observed within the HBrR local grid mean lag times ranging from 0. A schematic summarizing these regions of elevated bromine and the transport pathways from the UT into the LMS is shown in Fig.
Both possible transport pathways are investigated in the following with observational data from other measured gases Fig. The observational findings are as follows:.
Studies such as those by Fueglistaler et al. N 2 O is a good transport tracer due to its long lifetime of years e. In the extratropics just above the TP, N 2 O shows an increasing tropospheric contribution from high to low equivalent latitudes. This indicates that the tropospheric air masses transported there are not yet mixed with stratospheric air masses. The SF 6 measurements are also used for analysis of the transport as it constantly increases, and its atmospheric lifetime is in excess of years e.
As seen in Fig. The persistence of the HBrR observed in many flights during WISE and the already months-long presence and respective mixing generally rules out an origin of this air by some event-like short duration recent transport such as by high-reaching mesoscale convective systems or another form of STE process.
Studies such as by Pan et al. Vogel et al. A second horizontal transport pathway can occur through filamentation by Rossby wave breaking, east of the anticyclonic event in the extratropics Vogel et al. Specific Rossby wave-breaking events producing filaments irreversibly mix young tropospheric air into older air of the LMS e. The relative contributions of these transport pathways are investigated in the next section.
The atmospheric model is divided into nine domains. Figure 9 CLaMS artificial surface emission tracers by region based on previous simulations described in Vogel et al.
Adapted from Wetzel et al. The advection and mixing processes of the air parcels over the integration time result in the diverse compositions of the LMS air from the various domains of the atmosphere. The fractions of air originating in four of the atmospheric domains most relevant to our discussion are shown in Fig.
In the HBrR marked by the black box , the fraction of air from the tropical troposphere is Yan et al. Their findings are in agreement with those of von Hobe et al. Large bromine sources, particularly the VSLS, are from tropical marine regions, mainly in coastal areas Engel and Rigby et al.
Therefore, surface emission tracers for details see Sect. The sum of the surface emission tracers i. Therefore, the larger tropical tropospheric air contribution to the HBrR compared to the surrounding LS as seen in the air mass origin tracers is largely from recent surface emissions rather than from the free troposphere. The individual surface regions are displayed in Fig. The grouped emission tracer contributions to the HBrR and surrounding LS can be found in Table 5 , and for a breakdown of all surface emission tracers, see Fig.
The AMR accounts for This is in general agreement with results of CLaMS simulations using a previous version of surface emission tracers for and that found a flooding of the northern Ex-LS in boreal summer with young air masses from the region of the Asian monsoon and from the tropical Pacific Vogel et al.
Furthermore, this feature is in general agreement with findings of Orbe et al. Levine et al. The increased contribution of younger surface air to the HBrR compared to the surrounding air masses below and above has a significant influence on the trace gas composition, in particular, considering the majority of the surface air masses are transported from regions with large biological activity and known bromine sources Engel and Rigby et al.
This highlights the influence of surface emissions from southeastern Asia on pollutants and in particular bromine in the northern LMS during boreal fall. Adcock et al. Figure 12 Examples of recent air mass surface emissions from the tropical marine environment TME in southeastern Asia as well as elevated emissions from Central America CAM during flights in remnants of tropical cyclones.
Similarly, Ashfold et al. The fast transport on the order of days from the Asian tropical planetary boundary layer to the TTL allows even the short-lived trace substances from the southeastern Asian region to reach the UTLS Orbe et al.
The impact of maritime boundary sources on the chemical composition of the Asian monsoon anticyclone by convective uplift in tropical cyclones in the western Pacific is discussed by, e. A study by Liang et al. Hamer et al. Therefore, the solubility of the gases and local surrounding conditions may also impact the delivery to the TTL and finally the Ex-LS. This is partially when tropospheric O 3 is low and prevents the soluble forms of bromine from reacting and converting to insoluble inorganic bromine compounds.
There are two flights with particularly large air mass fractions from CAM emissions observed during the campaign, i. During both flights, remnant air masses of two mesoscale convective systems in the Central American tropics were probed. For reference for the following discussion, the average contribution of emissions from CAM excluding RF08 and RF14 per flight ranges from 4. This flight, off the coast of Ireland over the Atlantic Ocean up to The average CAM surface air fraction along the flight track is Only a short flight segment reached the HBrR, which is indicated by the dark gray shading in Fig.
They use H 2 O and O 3 lidar data as tropospheric and stratospheric tracers to discuss three mixing regimes near the tropopause fold indicating the presence of different air masses. This is verified from data collected during RF14 on the 15 October Fig.
A large influence of surface emission tracers from CAM is present, with a flight average of Although this flight does not have organic bromine data available, the variability of air masses probed by the aircraft in the LMS is noticeable in Br y inorg.
A third flight, RF15, on 19 October Fig. The air of this flight is also characterized by a slightly elevated CAM influence in the LS, mainly with a surface emission of 8. Only partial organic bromine data are available with slightly elevated VMRs Fig.
The CLaMS simulations indicate the variety of different air masses influencing our observations. Additionally, the two events with higher Br y inorg observed in the UT shaded light blue sections in Fig. The base run was initialized with constant bromine Run 1 and 2 each had elevated bromine boundary conditions in the tropical UT in addition to the Ex-TP boundary conditions from the base run see Table 3. Run 1 and 2 are initialized with an additional [Br tot ] of 1.
The increase in run 1 is mainly due to increased Br y inorg , while the increase of Br tot in run 2 is largely due to additional Br VSLS. The impact of increasing tropical UT bromine run 1 leads to 5. Run 2 leads to 8. In the HBrR, the absolute O 3 mixing ratios change by - 6. The decrease of O 3 is not strictly linear with increasing Br tot , partially due to the nature of the increased bromine Br y inorg vs.
Br VSLS differing between run 1 and 2, as well as other feedback loops such as via lower stratospheric HO x chemistry. The average relative O 3 loss throughout the whole LS is - 2. However, the largest relative O 3 decreases are observed along the tropical TP where there is the largest bromine enhancement due to the initialization.
Further significant decreases of O 3 extend to the midlatitudes along the TP. As the bromine increase in run 1 is mainly in the form of Br y inorg , this shows the efficiency and immediate destruction of O 3 by Br y inorg.
As the bromine increase of run 2 is largely in the form of Br VSLS , O 3 is not immediately destroyed because of the time delay for the conversion of Br org to Br y inorg. Although the O 3 destruction is not as strong near the source of increased bromine in run 2 compared to run 1, the O 3 decrease extends further towards the pole just above the TP.
A study by Hossaini et al. If the transport of source gases into the stratosphere in the tropics increases as climate change progresses, the strongest decrease in O 3 can be expected near the cold-point TP in agreement with the simulations here e. The majority of the observations vary between 8. The observations include air masses of the entire NH in equivalent latitudes, indicating geographical distributions as well as allowing for transport interpretation. Br tot is assessed from simultaneous measurements of all relevant Br org source gases and inferred Br y inorg.
The Br org source gases include CH 3 Br , the four halons, and the five major brominated, very short-lived substances. Air mass lag times inferred from SF 6 measurements vary by over 3 years. Major insights into the causes of the Br tot variability have been gained from studying the geographical distribution of the brominated gases as well as transport tracers as a function of equivalent latitude, both from observations Fig. The key findings of our study are summarized in Fig.
Elevated Br tot is observed in a persistent region extending into the LMS, i. The air mass origin tracers modeled by CLaMS agree reasonably well with our observations. The LS air masses below and above the HBrR show a decreasing tropospheric contribution while an approximately equivalent increasing stratospheric background contribution. Only a small fraction of air 3. This transport pathway in boreal late summer and fall has a direct impact on the trace gas composition and specifically of bromine in the northern LMS.
Our study complements previous studies on the importance of the transport of air masses via the lower branch of the Brewer—Dobson circulation e. Notably, air masses of high bromine were transported by two hurricanes from CAM into the tropical UT, i. Additionally, our flights captured two stratosphere—troposphere exchange STE events where stratospheric air of elevated Br y inorg was recently transported into the UT caused by breaking Rossby waves in the extratropics.
The continuous nature of our measurements covering a large range of air mass lag times, even for individual flights, offers several advantages over previous mainly balloon and some aircraft-related studies on Br tot. This includes an improved space and time resolution as well as a higher precision and accuracy of inferred Br tot. Her Research Unit is involved with clinical research, epidemiology and operational research, and is a treatment site for HIV infected adults and children.
Her research interests include HIV vaccine research, microbicide research and other biomedical and behavioural interventions, and she is an investigator in testing two HIV vaccine regimens in late stage clinical development.
He has been an author on over manuscripts in the field of infectious diseases and has an extensive track record in infectious diseases research and practice covering clinical, laboratory and epidemiological aspects. He is an HIV and TB immunologist focused on studying the immune response to these pathogens in affected tissues, and how this relates to what can be observed from the blood.
The research goal is to improve understanding of the immunopathology of TB and HIV, using this information to aid in developing novel therapeutic approaches and diagnostic biomarkers. His research has centered on understanding the mechanisms by which the human immune system recognises the Mycobacterium tuberculosis M.
His work has a strong translational component, asking if both classically and non-classically restricted T cells are associated with infection with M. Her current research focuses on HIV broadly neutralising antibodies and their interplay with the evolving virus. Recent studies published in PloS Pathogens, Nature and Nature Medicine have highlighted the role of viral escape in creating new epitopes and immunotypes, thereby driving the development of neutralisation breadth, with implications for HIV vaccine design.
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