scholarly journals Coordinated Airborne Studies in the Tropics (CAST)

2017 ◽  
Vol 98 (1) ◽  
pp. 145-162 ◽  
Author(s):  
N. R. P. Harris ◽  
L. J. Carpenter ◽  
J. D. Lee ◽  
G. Vaughan ◽  
M. T. Filus ◽  
...  
Keyword(s):  
Marine Boundary Layer ◽  
Chemical Species ◽  
Active Species ◽  
Convective Transport ◽  
Atmospheric Measurements ◽  
The West ◽  
West Pacific ◽  
Tropical Tropopause ◽  
The Tropics ◽  
Global Hawk

Abstract The main field activities of the Coordinated Airborne Studies in the Tropics (CAST) campaign took place in the west Pacific during January–February 2014. The field campaign was based in Guam (13.5°N, 144.8°E), using the U.K. Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 atmospheric research aircraft, and was coordinated with the Airborne Tropical Tropopause Experiment (ATTREX) project with an unmanned Global Hawk and the Convective Transport of Active Species in the Tropics (CONTRAST) campaign with a Gulfstream V aircraft. Together, the three aircraft were able to make detailed measurements of atmospheric structure and composition from the ocean surface to 20 km. These measurements are providing new information about the processes influencing halogen and ozone levels in the tropical west Pacific, as well as the importance of trace-gas transport in convection for the upper troposphere and stratosphere. The FAAM aircraft made a total of 25 flights in the region between 1°S and 14°N and 130° and 155°E. It was used to sample at altitudes below 8 km, with much of the time spent in the marine boundary layer. It measured a range of chemical species and sampled extensively within the region of main inflow into the strong west Pacific convection. The CAST team also made ground-based measurements of a number of species (including daily ozonesondes) at the Atmospheric Radiation Measurement Program site on Manus Island, Papua New Guinea (2.1°S, 147.4°E). This article presents an overview of the CAST project, focusing on the design and operation of the west Pacific experiment. It additionally discusses some new developments in CAST, including flights of new instruments on board the Global Hawk in February–March 2015.

scholarly journals The NASA Airborne Tropical Tropopause Experiment: High-Altitude Aircraft Measurements in the Tropical Western Pacific

2017 ◽  
Vol 98 (1) ◽  
pp. 129-143 ◽  
Author(s):  
Eric J. Jensen ◽  
Leonhard Pfister ◽  
David E. Jordan ◽  
Thaopaul V. Bui ◽  
Rei Ueyama ◽  
...  
Keyword(s):  
High Altitude ◽  
Active Species ◽  
Convective Transport ◽  
Western Pacific ◽  
Lower Altitude ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Cloud Properties ◽  
The Tropics ◽  
Global Hawk

Abstract The February–March 2014 deployment of the National Aeronautics and Space Administration (NASA) Airborne Tropical Tropopause Experiment (ATTREX) provided unique in situ measurements in the western Pacific tropical tropopause layer (TTL). Six flights were conducted from Guam with the long-range, high-altitude, unmanned Global Hawk aircraft. The ATTREX Global Hawk payload provided measurements of water vapor, meteorological conditions, cloud properties, tracer and chemical radical concentrations, and radiative fluxes. The campaign was partially coincident with the Convective Transport of Active Species in the Tropics (CONTRAST) and the Coordinated Airborne Studies in the Tropics (CAST) airborne campaigns based in Guam using lower-altitude aircraft (see companion articles in this issue). The ATTREX dataset is being used for investigations of TTL cloud, transport, dynamical, and chemical processes, as well as for evaluation and improvement of global-model representations of TTL processes. The ATTREX data are publicly available online (at https://espoarchive.nasa.gov/).

scholarly journals Emission and transport of bromocarbons: from the West Pacific ocean into the stratosphere

2012 ◽  
Vol 12 (22) ◽  
pp. 10633-10648 ◽  
Author(s):  
S. Tegtmeier ◽  
K. Krüger ◽  
B. Quack ◽  
E. L. Atlas ◽  
I. Pisso ◽  
...  
Keyword(s):  
Ozone Depletion ◽  
Transport Model ◽  
Source Region ◽  
Convective Transport ◽  
Tropical Atlantic ◽  
The West ◽  
West Pacific ◽  
Oceanic Emissions ◽  
In Situ Observations

Abstract. Oceanic emissions of halogenated very short-lived substances (VSLS) are expected to contribute significantly to the stratospheric halogen loading and therefore to ozone depletion. The amount of VSLS transported into the stratosphere is estimated based on in-situ observations around the tropical tropopause layer (TTL) and on modeling studies which mostly use prescribed global emission scenarios to reproduce observed atmospheric concentrations. In addition to upper-air VSLS measurements, direct observations of oceanic VSLS emissions are available along ship cruise tracks. Here we use such in-situ observations of VSLS emissions from the West Pacific and tropical Atlantic together with an atmospheric Lagrangian transport model to estimate the direct contribution of bromoform (CHBr3), and dibromomethane (CH2Br2) to the stratospheric bromine loading as well as their ozone depletion potential. Our emission-based estimates of VSLS profiles are compared to upper-air observations and thus link observed oceanic emissions and in situ TTL measurements. This comparison determines how VSLS emissions and transport in the cruise track regions contribute to global upper-air VSLS estimates. The West Pacific emission-based profiles and the global upper-air observations of CHBr3 show a relatively good agreement indicating that emissions from the West Pacific provide an average contribution to the global CHBr3 budget. The tropical Atlantic, although also being a CHBr3 source region, is of less importance for global upper-air CHBr3 estimates as revealed by the small emission-based abundances in the TTL. Western Pacific CH2Br2 emission-based estimates are considerably smaller than upper-air observations as a result of the relatively low sea-to-air flux found in the West Pacific. Together, CHBr3 and CH2Br2 emissions from the West Pacific are projected to contribute to the stratospheric bromine budget with 0.4 pptv Br on average and 2.3 pptv Br for cases of maximum emissions through product and source gas injection. These relatively low estimates reveal that the tropical West Pacific, although characterized by strong convective transport, might overall contribute less VSLS to the stratospheric bromine budget than other regions as a result of only low CH2Br2 and moderate CHBr3 oceanic emissions.

scholarly journals Contribution of mixing to upward transport across the tropical tropopause layer (TTL)

2007 ◽  
Vol 7 (12) ◽  
pp. 3285-3308 ◽  
Author(s):  
P. Konopka ◽  
G. Günther ◽  
R. Müller ◽  
F. H. S. dos Santos ◽  
C. Schiller ◽  
...  
Keyword(s):  
Large Scale ◽  
Potential Temperature ◽  
Vertical Mixing ◽  
Chemical Species ◽  
Convective Transport ◽  
Vertical Shear ◽  
Lagrangian Model ◽  
Tropical Tropopause ◽  
Upward Transport ◽  
Meteorological Analysis

Abstract. During the second part of the TROCCINOX campaign that took place in Brazil in early 2005, chemical species were measured on-board the high-altitude research aircraft Geophysica (ozone, water vapor, NO, NOy, CH4 and CO) in the altitude range up to 20 km (or up to 450 K potential temperature), i.e. spanning the entire TTL region roughly extending between 350 and 420 K. Here, analysis of transport across the TTL is performed using a new version of the Chemical Lagrangian Model of the Stratosphere (CLaMS). In this new version, the stratospheric model has been extended to the earth surface. Above the tropopause, the isentropic and cross-isentropic advection in CLaMS is driven by meteorological analysis winds and heating/cooling rates derived from a radiation calculation. Below the tropopause, the model smoothly transforms from the isentropic to the hybrid-pressure coordinate and, in this way, takes into account the effect of large-scale convective transport as implemented in the vertical wind of the meteorological analysis. As in previous CLaMS simulations, the irreversible transport, i.e. mixing, is controlled by the local horizontal strain and vertical shear rates. Stratospheric and tropospheric signatures in the TTL can be seen both in the observations and in the model. The composition of air above ≈350 K is mainly controlled by mixing on a time scale of weeks or even months. Based on CLaMS transport studies where mixing can be completely switched off, we deduce that vertical mixing, mainly driven by the vertical shear in the tropical flanks of the subtropical jets and, to some extent, in the the outflow regions of the large-scale convection, offers an explanation for the upward transport of trace species from the main convective outflow at around 350 K up to the tropical tropopause around 380 K.

scholarly journals Contribution of mixing to the upward transport across the TTL

2006 ◽  
Vol 6 (6) ◽  
pp. 12217-12266 ◽  
Author(s):  
P. Konopka ◽  
G. Günther ◽  
R. Müller ◽  
F. H. S. dos Santos ◽  
C. Schiller ◽  
...  
Keyword(s):  
Large Scale ◽  
Potential Temperature ◽  
Vertical Mixing ◽  
Chemical Species ◽  
Convective Transport ◽  
Vertical Shear ◽  
Lagrangian Model ◽  
Tropical Tropopause ◽  
Upward Transport ◽  
Subtropical Jets

Abstract. During the second part of the TROCCINOX campaign that took place in Brazil in early 2005, chemical species were measured on-board of the high altitude research aircraft Geophysica (ozone, water vapor, NO, NOy, CH4 and CO) in the altitude range up to 20 km (or up to 450 K potential temperature), i.e. spanning the TTL region roughly extending between 350 and 420 K. Analysis of transport across TTL is performed using a new version of the Chemical Lagrangian Model of the Stratosphere (CLaMS). In this new version, the stratospheric model has been extended to the earth surface. Above the tropopause, the isentropic and cross-isentropic advection in CLaMS is driven by ECMWF winds and heating/cooling rates derived from a radiation calculation. Below the tropopause the model smoothly transforms from the isentropic to hybrid-pressure coordinate and, in this way, takes into account the effect of large-scale convective transport as implemented in the ECMWF vertical wind. As with other CLaMS simulations, the irreversible transport, i.e. mixing, is controlled by the local horizontal strain and vertical shear rates. Stratospheric and tropospheric signatures in the TTL can be seen both in the observation and in the model. The composition of air above ≈350 K is mainly controlled by mixing on a time scale of weeks or even months. Based on CLaMS transport studies where mixing can be completely switched off, we deduce that vertical mixing, mainly driven by the vertical shear in the outflow regions of the large-scale convection and in the vicinity of the subtropical jets, is necessary to understand the upward transport of the tropospheric air from the main convective outflow around 350 K up to the tropical tropopause around 380 K. This mechanism is most effective if the outflow of the mesoscale convective systems interacts with the subtropical jets.

scholarly journals Impact of land convection on troposphere-stratosphere exchange in the tropics

2007 ◽  
Vol 7 (2) ◽  
pp. 3269-3300 ◽  
Author(s):  
P. Ricaud ◽  
B. Barret ◽  
J.-L. Attié ◽  
E. Le Flochmoën ◽  
E. Motte ◽  
...  
Keyword(s):  
Transport Model ◽  
Source Region ◽  
Tropical Rainfall Measuring Mission ◽  
Convective Transport ◽  
Chemical Transport Model ◽  
Tropical Tropopause Layer ◽  
Evergreen Forests ◽  
Tropical Tropopause ◽  
Longitudinal Gradients ◽  
The Tropics

Abstract. The mechanism of troposphere-stratosphere exchange in the tropics was investigated from space-borne observations of the horizontal distributions of nitrous oxide (N2O), methane (CH4) and carbon monoxide (CO) at 17 km in March-April-May by the ODIN/Sub-Millimeter Radiometer (SMR), the Upper Atmosphere Research Satellite (UARS)/Halogen Occultation Experiment (HALOE) and the TERRA/Measurements Of Pollution In The Troposphere (MOPITT) instruments in 2002–2004, completed by recent observations of the AURA/Microwave Limb Sounder (MLS) instrument during the same season in 2005. At the top of the Tropical Tropopause Layer (TTL), all gases show significant longitudinal gradients with maximum amounts primarily over Africa and, depending on the species, secondary more or less pronounced maxima above northern South America and South-East Asia. The Maritime continent in the Western Pacific never appears as a source region for the stratosphere. The large longitudinal gradient at latitudes where the circulation is essentially zonal, and the co-location of the maximum tropospheric trace gases concentrations with the overshooting features reported by the Tropical Rainfall Measuring Mission (TRMM) satellite precipitation radar, strongly supports that rapid uplift over land convective regions is the dominating process of troposphere-stratosphere exchange. Calculations carried out with the MOCAGE-Climat chemical transport model well capture the location of the maximum gas concentration in the TTL but of lesser amplitude. Although there are obvious misrepresentations of some of the sources in the model, i.e. CH4 emissions by evergreen forests, the main reason for discrepancy appears to be the underestimation of the maximum altitude reached by land convective transport in MOCAGE.

scholarly journals Dimethylsulphide (DMS) emissions from the West Pacific Ocean: a potential marine source for the stratospheric sulphur layer

2012 ◽  
Vol 12 (11) ◽  
pp. 30543-30570
Author(s):  
C. A. Marandino ◽  
S. Tegtmeier ◽  
K. Krüger ◽  
C. Zindler ◽  
E. L. Atlas ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Transport Model ◽  
Atmospheric Transport ◽  
Dispersion Model ◽  
Transport Processes ◽  
Atmospheric Measurements ◽  
The West ◽  
West Pacific ◽  
West Pacific Ocean ◽  
The West Pacific Ocean

Abstract. Sea surface and atmospheric measurements of dimethylsulphide (DMS) were performed during the TransBrom cruise in the West Pacific Ocean between Japan and Australia in October 2009. Air-sea DMS fluxes were computed between 0 and 30 μmol m−2 d−1, which are in agreement with those computed by the current climatology, and peak emissions of marine DMS into the atmosphere were found during the occurrence of tropical storm systems. Atmospheric variability in DMS, however, did not follow that of the computed fluxes and was more related to atmospheric transport processes. The computed emissions were used as input fields for the Langrangian dispersion model FLEXPART, which was set up with actual meteorological fields from ERA-interim data and different chemical lifetimes of DMS. A comparison with aircraft in-situ data from the adjacent HIPPO2 campaign revealed an overall good agreement between modeled versus observed DMS profiles over the tropical West Pacific ocean. Based on observed DMS emissions and the meteorological fields over the cruise track region, the model projected that up to 30 g S per month in the form of DMS can be transported above 17 km in this region. This surprisingly large DMS entrainment into the stratosphere is disproportionate to the regional extent of the cruise track area and mainly due to the high convective activity in this region as simulated by the transport model. Thus, we conclude that the considerably larger area of the tropical West Pacific Ocean can be an important source of sulphur to the stratospheric persistent sulphur layer, which has not been considered as yet.

scholarly journals Convective transport of very-short-lived bromocarbons to the stratosphere

2014 ◽  
Vol 14 (1) ◽  
pp. 651-676
Author(s):  
Q. Liang ◽  
E. Atlas ◽  
D. Blake ◽  
M. Dorf ◽  
K. Pfeilsticker ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Climate Model ◽  
Degradation Products ◽  
Deep Convection ◽  
Gas Injection ◽  
Tropical Indian Ocean ◽  
Warm Pool ◽  
Convective Transport ◽  
Tropical Tropopause

Abstract. We use the NASA GEOS Chemistry Climate Model (GEOSCCM) to quantify the contribution of two most important brominated very short-lived substances (VSLS), bromoform (CHBr3) and dibromomethane (CH2Br2), to stratospheric bromine and its sensitivity to convection strength. Model simulations suggest that the most active transport of VSLS from the marine boundary layer through the tropopause occurs over the tropical Indian Ocean, the Western Pacific warm pool, and off the Pacific coast of Mexico. Together, convective lofting of CHBr3 and CH2Br2 and their degradation products supplies ∼8 ppt total bromine to the base of the Tropical Tropopause Layer (TTL, ∼150 hPa), similar to the amount of VSLS organic bromine available in the marine boundary layer (∼7.8–8.4 ppt) in the above active convective lofting regions. Of the total ∼8 ppt VSLS-originated bromine that enters the base of TTL at ∼150 hPa, half is in the form of source gas injection (SGI) and half as product gas injection (PGI). Only a small portion (< 10%) the VSLS-originated bromine is removed via wet scavenging in the TTL before reaching the lower stratosphere. On global and annual average, CHBr3 and CH2Br2, together, contribute ∼7.7 pptv to the present-day inorganic bromine in the stratosphere. However, varying model deep convection strength between maximum and minimum convection conditions can introduce a ∼2.6 pptv uncertainty in the contribution of VSLS to inorganic bromine in the stratosphere (BryVSLS). Contrary to the conventional wisdom, minimum convection condition leads to a larger BryVSLS as the reduced scavenging in soluble product gases, thus a significant increase in PGI (2–3 ppt), greatly exceeds the relative minor decrease in SGI (a few 10ths ppt).

scholarly journals Transport of short-lived species into the Tropical Tropopause Layer

2012 ◽  
Vol 12 (1) ◽  
pp. 441-478 ◽  
Author(s):  
M. J. Ashfold ◽  
N. R. P. Harris ◽  
E. L. Atlas ◽  
A. J. Manning ◽  
J. A. Pyle
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Vertical Profiles ◽  
The West ◽  
West Pacific ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
La Nina

Abstract. We use NAME, a trajectory model, to investigate the routes and timescales over which air parcels reach the tropical tropopause layer (TTL). Our aim is to assist the planning of aircraft campaigns focussed on improving knowledge of such transport. We investigate the conditions which might occur during one such campaign, SHIVA, which takes place in Borneo during November 2011. We first study the TTL above Borneo in November 2008, under neutral El Niño/Southern Oscillation (ENSO) conditions. Air parcels (trajectories) arriving in the lower TTL (below ~15 km) are most likely to have travelled from the boundary layer (BL; <1 km) above the West Pacific. Few air parcels found above ~16 km travelled from the BL in the previous 15 days. We then perform similar calculations for moderate El Niño (2006) and La Niña (2007) conditions and find year-to-year variability consistent with the phase of ENSO. Under El Niño conditions fewer air parcels travel from the BL to the TTL above Borneo. During the La Niña year, more air parcels travel from the BL to the mid and upper TTL (above ~15 km) than in the ENSO-neutral year, and again they do so from the BL above the West Pacific. We also find intra-month variability in all years, with day-to-day differences of up to an order of magnitude in the fraction of an idealised short-lived tracer travelling from the BL to the TTL above Borneo. Finally, we consider measurements made in two previous campaigns in order to validate our approach. The features of vertical profiles of short-lived species observed in the TTL during CR-AVE and TC4 are in broad agreement with calculated vertical profiles of idealised short-lived tracers. It will require large numbers of observations to fully describe the statistical distribution of short-lived species in the TTL. This modelling approach should prove valuable in planning flights for the long-duration aircraft capable of making such measurements.

scholarly journals Transport of short-lived species into the Tropical Tropopause Layer

2012 ◽  
Vol 12 (14) ◽  
pp. 6309-6322 ◽  
Author(s):  
M. J. Ashfold ◽  
N. R. P. Harris ◽  
E. L. Atlas ◽  
A. J. Manning ◽  
J. A. Pyle
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Vertical Profiles ◽  
The West ◽  
West Pacific ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
La Nina

Abstract. We use NAME, a trajectory model, to investigate the routes and timescales over which air parcels reach the tropical tropopause layer (TTL). Our aim is to assist the planning of aircraft campaigns focussed on improving knowledge of such transport. We focus on Southeast Asia and the Western Pacific which appears to be a particularly important source of air that enters the TTL. We first study the TTL above Borneo in November 2008, under neutral El Niño/Southern Oscillation (ENSO) conditions. Air parcels (trajectories) arriving in the lower TTL (below ~15 km) are most likely to have travelled from the boundary layer (BL; <1 km) above the West Pacific. Few air parcels found above ~16 km travelled from the BL in the previous 15 days. We then perform similar calculations for moderate El Niño (2006) and La Niña (2007) conditions and find year-to-year variability consistent with the phase of ENSO. Under El Niño conditions fewer air parcels travel from the BL to the TTL above Borneo. During the La Niña year, more air parcels travel from the BL to the mid and upper TTL (above ~15 km) than in the ENSO-neutral year, and again they do so from the BL above the West Pacific. We also find intra-month variability in all years, with day-to-day differences of up to an order of magnitude in the fraction of an idealised short-lived tracer travelling from the BL to the TTL above Borneo. These calculations were performed as a prelude to the SHIVA field campaign, which took place in Borneo during November 2011. So finally, to validate our approach, we consider measurements made in two previous campaigns. The features of vertical profiles of short-lived species observed in the TTL during CR-AVE and TC4 are in broad agreement with calculated vertical profiles of idealised short-lived tracers. It will require large numbers of observations to fully describe the statistical distribution of short-lived species in the TTL. This modelling approach should prove valuable in planning flights for the long-duration aircraft now capable of making such measurements.

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