scholarly journals Impact of deep convection on the tropical tropopause layer composition in Equatorial Brazil

2011 ◽  
Vol 11 (5) ◽  
pp. 16147-16183 ◽  
Author(s):  
V. Marécal ◽  
G. Krysztofiak ◽  
Y. Mébarki ◽  
V. Catoire ◽  
F. Lott ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Biomass Burning ◽  
Transition Period ◽  
Deep Convection ◽  
Dry Season ◽  
Radiative Heating ◽  
Quasi Biennial Oscillation ◽  
Backward Trajectories ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause

Abstract. This paper documents measurements of carbon monoxide (CO), ozone (O3) and temperature in the tropical tropopause layer over Equatorial Brazil for the first time. These measurements were sampled by the balloon-borne instrument SPIRALE (Spectroscopie Infa-Rouge par Absorption de Lasers Embarqués) in June 2005 and in June 2008, both at the transition period from wet to dry season. The height of the Tropical Tropopause Layer (TTL) top and bottom determined from the chemical species profiles are similar for the two flights. Nevertheless the measured profiles of ozone and CO are different in their volume mixing ratio and shape. The larger CO values measured in the TTL in 2005 can be linked to a more intense biomass burning activity in 2005 than in 2008. We also show that both measured profiles are influenced by convection but in different ways leading to different shapes. The CO profile in 2005 is characterised by a generally smooth decrease in the TTL from tropospheric to stratospheric conditions, except for two layers of enhanced CO around 14.2 (>100 parts per billion by volume = ppbv) and 16.3 km altitude (>85 ppbv). Backward trajectories indicate that these layers come from the vertical transport by remote deep convection occurring 2 and 3 days prior to the flight, respectively. This shows that the transition period from wet to dry season is favourable for the transport of significant amounts of CO in the TTL, sometimes above the level of zero radiative heating, because of increasing biomass burning together with decaying but still important convective activity. In 2008 we focus our analysis on a 1 km deep layer, between 17 and 18 km, where both the temperature and the ozone profiles are uniform in the vertical, corresponding to a layer of well-mixed air. We show that this unusual behaviour is indirectly related to the interaction between convection and the Quasi-Biennial Oscillation (QBO), through vertically propagating gravity waves. Quasi-stationary gravity waves are likely to be produced by convective systems and certainly break in the intense wind shear that imposes the QBO at these altitudes. This conclusion is supported by the fact that the 16–18 km layer is devoid of ice particles (hence the mixing is not convective) and from backward trajectories that point towards a convective region as the origin of the air masses in this layer.

scholarly journals Model study of the cross-tropopause transport of biomass burning pollution

2007 ◽  
Vol 7 (14) ◽  
pp. 3713-3736 ◽  
Author(s):  
B. N. Duncan ◽  
S. E. Strahan ◽  
Y. Yoshida ◽  
S. D. Steenrod ◽  
N. Livesey
Keyword(s):  
Biomass Burning ◽  
El Niño ◽  
Fossil Fuels ◽  
Extreme Event ◽  
El Nino ◽  
Deep Convection ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
El Niño Event ◽  
The Impact

Abstract. We present a modeling study of the troposphere-to-stratosphere transport (TST) of pollution from major biomass burning regions to the tropical upper troposphere and lower stratosphere (UT/LS). TST occurs predominately through 1) slow ascent in the tropical tropopause layer (TTL) to the LS and 2) quasi-horizontal exchange to the lowermost stratosphere (LMS). We show that biomass burning pollution regularly and significantly impacts the composition of the TTL, LS, and LMS. Carbon monoxide (CO) in the LS in our simulation and data from the Aura Microwave Limb Sounder (MLS) shows an annual oscillation in its composition that results from the interaction of an annual oscillation in slow ascent from the TTL to the LS and seasonal variations in sources, including a semi-annual oscillation in CO from biomass burning. The impacts of CO sources that peak when ascent is seasonally low are damped (e.g. Southern Hemisphere biomass burning) and vice-versa for sources that peak when ascent is seasonally high (e.g. extra-tropical fossil fuels). Interannual variation of CO in the UT/LS is caused primarily by year-to-year variations in biomass burning and the locations of deep convection. During our study period, 1994–1998, we find that the highest concentrations of CO in the UT/LS occurred during the strong 1997–1998 El Niño event for two reasons: i. tropical deep convection shifted to the eastern Pacific Ocean, closer to South American and African CO sources, and ii. emissions from Indonesian biomass burning were higher. This extreme event can be seen as an upper bound on the impact of biomass burning pollution on the UT/LS. We estimate that the 1997 Indonesian wildfires increased CO in the entire TTL and tropical LS (>60 mb) by more than 40% and 10%, respectively, for several months. Zonal mean ozone increased and the hydroxyl radical decreased by as much as 20%, increasing the lifetimes and, subsequently TST, of trace gases. Our results indicate that the impact of biomass burning pollution on the UT/LS is likely greatest during an El Niño event due to favorable dynamics and historically higher burning rates.

scholarly journals Estimating the contribution of bromoform to stratospheric bromine and its relation to dehydration in the tropical tropopause layer

2006 ◽  
Vol 6 (12) ◽  
pp. 4755-4761 ◽  
Author(s):  
B.-M. Sinnhuber ◽  
I. Folkins
Keyword(s):  
Boundary Layer ◽  
Degradation Products ◽  
Deep Convection ◽  
Extreme Case ◽  
Radiative Heating ◽  
Model Calculations ◽  
One Dimensional ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
The One

Abstract. The contribution of bromoform to the stratospheric bromine loading is estimated using the one-dimensional tropical mean model of Folkins and Martin (2005), which is constrained by observed mean profiles of temperature and humidity. In order to reach the stratosphere, bromoform needs to be lifted by deep convection into the tropical tropopause layer (TTL), above the level of zero radiative heating. The contribution of bromoform to stratospheric bromine then depends critically on the rate of removal of the degradation products of bromoform (collectively called Bry here) from the TTL, which is believed to be due to scavenging by falling ice. This relates the transport of short-lived bromine species into the stratosphere to processes of dehydration in the TTL. In the extreme case of dehydration occurring only through overshooting deep convection, the loss of Bry from the TTL may be negligible and consequently bromoform will fully contribute with its boundary layer mixing ratio to the stratospheric bromine loading, i.e. with 3 pptv for an assumed 1 pptv of bromoform in the boundary layer. For the other extreme that Bry is removed from the TTL almost instantaneously, the model calculations predict a contribution of about 0.5 pptv for the assumed 1 pptv of boundary layer bromoform. While this gives some constraints on the contribution of bromoform to stratospheric bromine, a key uncertainty in estimating the contribution of short-lived bromine source gases to the stratospheric bromine loading is the mechanism and rate of removal of Bry within the TTL.

scholarly journals Long-term climatology of air mass transport through the Tropical Tropopause Layer (TTL) during NH winter

2008 ◽  
Vol 8 (4) ◽  
pp. 813-823 ◽  
Author(s):  
K. Krüger ◽  
S. Tegtmeier ◽  
M. Rex
Keyword(s):  
Mass Transport ◽  
El Niño ◽  
El Nino ◽  
Volcanic Eruptions ◽  
Radiative Heating ◽  
Quasi Biennial Oscillation ◽  
Air Mass ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause

Abstract. A long-term climatology of air mass transport through the tropical tropopause layer (TTL) is presented, covering the period from 1962–2005. The transport through the TTL is calculated with a Lagrangian approach using radiative heating rates as vertical velocities in an isentropic trajectory model. We demonstrate the improved performance of such an approach compared to previous studies using vertical winds from meteorological analyses. Within the upper part of the TTL, the averaged diabatic ascent is 0.5 K/day during Northern Hemisphere (NH) winters 1992–2001. Climatological maps show a cooling and strengthening of this part of the residual circulation during the 1990s and early 2000s compared to the long-term mean. Lagrangian cold point (LCP) fields show systematic differences for varying time periods and natural forcing components. The interannual variability of LCP temperature and density fields is found to be influenced by volcanic eruptions, El Niño Southern Oscillation (ENSO), Quasi-Biennial Oscillation (QBO) and the solar cycle. The coldest and driest TTL is reached during QBO easterly phase and La Niña over the western Pacific, whereas during volcanic eruptions, El Niño and QBO westerly phase it is warmer and less dry.

scholarly journals Effects of tropical deep convection on interannual variability of tropical tropopause layer water vapor

2017 ◽  
Author(s):  
Hao Ye ◽  
Andrew E. Dessler ◽  
Wandi Yu
Keyword(s):  
Water Vapor ◽  
Interannual Variability ◽  
Deep Convection ◽  
Tropospheric Temperature ◽  
Quasi Biennial Oscillation ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Tropical Deep Convection ◽  
The Impact ◽  
Biennial Oscillation

Abstract. Water vapor interannual variability in the tropical tropopause layer (TTL) is investigated using satellite observations and model simulations. We breakdown the influences of the Brewer-Dobson circulation (BDC), the quasi-biennial oscillation (QBO), and the tropospheric temperature (ΔT) as a function of latitude and longitude using a 2-dimensional multivariable linear regression. This allows us to examine the spatial distribution of the impact on TTL water vapor from these physical processes. In agreement with expectation, we find that the impacts from the BDC and QBO act on TTL water vapor by changing TTL temperature. For ΔT, we find that TTL temperatures alone cannot explain the influence. We hypothesize a moistening role for the evaporation of convective ice from increased deep convection as troposphere warms. Tests with simulations from GEOSCCM and a corresponding trajectory model support this hypothesis.

scholarly journals Impacts of tropical cyclones on the thermodynamic conditions in the tropical tropopause layer observed by A-Train satellites

2021 ◽  
Vol 21 (20) ◽  
pp. 15493-15518
Author(s):  
Jing Feng ◽  
Yi Huang
Keyword(s):  
Water Vapor ◽  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
Deep Convection ◽  
Radiative Heating ◽  
Radiative Cooling ◽  
Radiative Balance ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
The Impact

Abstract. The tropical tropopause layer (TTL) is the transition layer between the troposphere and the stratosphere. Tropical cyclones may impact the TTL by perturbing the vertical distributions of cloud, temperature, and water vapor. This study combines several A-Train instruments, including radar from CloudSat, lidar from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite, and the Atmospheric Infrared Sounder (AIRS) on the Aqua satellite, to detect signatures of cyclone impacts on the distribution patterns of cloud, water vapor, temperature, and radiation by compositing these thermodynamic fields relative to the cyclone center location. Based on the CloudSat 2B-CLDCLASS-LIDAR product, this study finds that tropical cyclone events considerably increase the occurrence frequencies of TTL clouds, in the form of cirrus clouds above a clear troposphere. The amount of TTL cloud ice, however, is found to be mostly contributed by overshooting deep convection that penetrates the base of the TTL at 16 km. To overcome the lack of temperature and water vapor products in cloudy conditions, this study implements a synergistic method that retrieves temperature, water vapor, ice water content, and effective radius simultaneously by incorporating observations from AIRS, CloudSat, and CALIPSO. Using the synergistic method, we find a vertically oscillating pattern of temperature anomalies above tropical cyclones, with warming beneath the cloud top (around 16 km) and cooling above. Based on water vapor profiles retrieved by the synergistic method, we find that the layer integrated water vapor (LIWV) above 16 km is higher above tropical cyclones, especially above overshooting deep convective clouds, compared to climatological values. Moreover, we find that the longwave and net radiative cooling effect of clouds prevails within 1000 km of tropical cyclone centers. The radiative heating effects of clouds from the CloudSat 2B-FLXHR-LIDAR product are well differentiated by the collocated brightness temperature of an infrared window channel from the collocated AIRS L1B product. By performing instantaneous radiative heating rate calculations, we further find that TTL hydration is usually associated with radiative cooling of the TTL, which inhibits the diabatic ascent of moist air across isentropic surfaces to the stratosphere. Therefore, the radiative balance of the TTL under the impact of the cyclone does not favor the maintenance of moist anomalies in the TTL or transporting water vertically to the stratosphere.

scholarly journals Overshooting of clean tropospheric air in the tropical lower stratosphere as seen by the CALIPSO lidar

2011 ◽  
Vol 11 (18) ◽  
pp. 9683-9696 ◽  
Author(s):  
J.-P. Vernier ◽  
J.-P. Pommereau ◽  
L. W. Thomason ◽  
J. Pelon ◽  
A. Garnier ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Lower Stratosphere ◽  
Thermal Structure ◽  
Radiative Heating ◽  
Major Contributor ◽  
Upper Troposphere ◽  
Tropical Tropopause Layer ◽  
Volcanic Plumes ◽  
Tropical Tropopause ◽  
Organic Particles

Abstract. The evolution of aerosols in the tropical upper troposphere/lower stratosphere between June 2006 and October 2009 is examined using the observations of the space borne CALIOP lidar aboard the CALIPSO satellite. Superimposed on several volcanic plumes and soot from an extreme biomass-burning event in 2009, the measurements reveal the existence of fast-cleansing episodes in the lower stratosphere to altitudes as high as 20 km. The cleansing of the layer, which extends from 14 to 20 km, takes place within 1 to 4 months during the southern tropics convective season that transports aerosol-poor tropospheric air into the lower stratosphere. In contrast, the convective season of the Northern Hemisphere summer shows an increase in the particle load at the tropopause consistent with a lofting of air rich with aerosols. These aerosols can consist of surface-derived material such as mineral dust and soot as well as liquid sulfate and organic particles. The flux of tropospheric air during the Southern Hemisphere convective season derived from CALIOP observations is shown to be 5 times at 16 km and 20 times at 19 km larger, respectively, than that associated with flux caused by slow ascent through radiative heating. These results suggest that convective overshooting is a major contributor to troposphere-to-stratosphere transport with concomitant implications for the Tropical Tropopause Layer top height, the humidity, the photochemistry and the thermal structure of the layer.

scholarly journals Estimating the contribution of bromoform to stratospheric bromine and its relation to dehydration in the tropical tropopause layer

2005 ◽  
Vol 5 (6) ◽  
pp. 12939-12956 ◽  
Author(s):  
B.-M. Sinnhuber ◽  
I. Folkins
Keyword(s):  
Boundary Layer ◽  
Degradation Products ◽  
Deep Convection ◽  
Extreme Case ◽  
Radiative Heating ◽  
Model Calculations ◽  
One Dimensional ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
The One

Abstract. The contribution of bromoform to the stratospheric bromine loading is estimated using the one-dimensional tropical mean model of Folkins and Martin (2005), which is constrained by observed mean profiles of temperature and humidity. In order to reach the stratosphere, bromoform needs to be lifted by deep convection into the tropical tropopause layer (TTL), above the level of zero radiative heating. The contribution of bromoform to stratospheric bromine depends then critically on the rate of removal of the degradation products of bromoform (collectively called Bry here) from the TTL, which is believed to be due to scavenging by falling ice. This relates the transport of short-lived bromine species into the stratosphere to processes of dehydration in the TTL. In the extreme case of dehydration occurring only through overshooting deep convection, the loss of Bry from the TTL may be negligible and consequently bromoform will fully contribute with its boundary layer mixing ratio to the stratospheric bromine loading, i.e. with 3 pptv for an assumed 1 pptv of bromoform in the boundary layer. For the other extreme that Bry is removed from the TTL almost instantaneously, the model calculations predict a contribution of about 0.5 pptv for the assumed 1 pptv of boundary layer bromoform. While this gives some constraints on the contribution of bromoform to stratospheric bromine, it is argued that a more precise number cannot be given until the mechanisms of dehydration in the TTL are better understood.

scholarly journals Effects of convective ice evaporation on interannual variability of tropical tropopause layer water vapor

2018 ◽  
Vol 18 (7) ◽  
pp. 4425-4437 ◽  
Author(s):  
Hao Ye ◽  
Andrew E. Dessler ◽  
Wandi Yu
Keyword(s):  
Water Vapor ◽  
Interannual Variability ◽  
Climate Model ◽  
Deep Convection ◽  
Tropospheric Temperature ◽  
Quasi Biennial Oscillation ◽  
Tropical Tropopause Layer ◽  
Earth Observing System ◽  
Tropical Tropopause ◽  
The Impact

Abstract. Water vapor interannual variability in the tropical tropopause layer (TTL) is investigated using satellite observations and model simulations. We break down the influences of the Brewer–Dobson circulation (BDC), the quasi-biennial oscillation (QBO), and the tropospheric temperature (ΔT) on TTL water vapor as a function of latitude and longitude using a two-dimensional multivariate linear regression. This allows us to examine the spatial distribution of the impact of each process on TTL water vapor. In agreement with expectations, we find that the impacts from the BDC and QBO act on TTL water vapor by changing TTL temperature. For ΔT, we find that TTL temperatures alone cannot explain the influence. We hypothesize a moistening role for the evaporation of convective ice from increased deep convection as the troposphere warms. Tests using a chemistry–climate model, the Goddard Earth Observing System Chemistry Climate Model (GEOSCCM), support this hypothesis.

scholarly journals Ozonesonde profiles from the West Pacific Warm Pool

2015 ◽  
Vol 15 (12) ◽  
pp. 16655-16696 ◽  
Author(s):  
R. Newton ◽  
G. Vaughan ◽  
H. M. A. Ricketts ◽  
L. L. Pan ◽  
A. J. Weinheimer ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Ozone Concentration ◽  
Deep Convection ◽  
Warm Pool ◽  
Atmospheric Composition ◽  
Measured Signal ◽  
Background Current ◽  
West Pacific ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause

Abstract. We present a series of ozonesonde profiles measured from Manus Island, Papua New Guinea, during February 2014. The experiment formed a part of a wider airborne campaign involving three aircraft based in Guam, to characterise the atmospheric composition above the tropical West Pacific in unprecedented detail. Thirty-nine ozonesondes were launched between 2 and 25 February, of which 34 gave good ozone profiles. Particular attention was paid to measuring the background current of the ozonesonde before launch, as this can amount to half the measured signal in the tropical tropopause layer (TTL). An unexpected contamination event affected these measurements and required a departure from standard operating procedures for the ozonesondes. Comparison with aircraft measurements allows validation of the measured ozone profiles and confirms that for well-characterized sondes (background current <50 nA) a constant background current should be assumed throughout the profile, equal to the minimum value measured during preparation just before launch. From this set of 34 ozonesondes, the minimum reproducible ozone concentration measured in the TTL was 12–13 ppbv; no examples of near-zero ozone concentration as reported by other recent papers were measured. The lowest ozone concentrations coincided with outflow from extensive deep convection to the east of Manus, consistent with uplift of ozone-poor air from the boundary layer. However, these minima were lower than the ozone concentration measured through most of the boundary layer, and were matched only by measurements at the surface in Manus.

scholarly journals Quantifying the Radiative Impact of Clouds on Tropopause Layer Cooling in Tropical Cyclones

2020 ◽  
Vol 33 (15) ◽  
pp. 5527-5542
Author(s):  
Louis Rivoire ◽  
Thomas Birner ◽  
John A. Knaff ◽  
Natalie Tourville
Keyword(s):  
Tropical Cyclones ◽  
Spatial Scales ◽  
Radiative Heating ◽  
Orthogonal Polarization ◽  
Heating Rates ◽  
Tropical Tropopause Layer ◽  
Convective Clouds ◽  
Tropical Tropopause ◽  
Convective Region ◽  
Order Of Magnitude

AbstractA ubiquitous cold signal near the tropopause, here called “tropopause layer cooling” (TLC), has been documented in deep convective regions such as tropical cyclones (TCs). Temperature retrievals from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) reveal cooling of order 0.1–1 K day−1 on spatial scales of order 1000 km above TCs. Data from the Cloud Profiling Radar (onboard CloudSat) and from the Cloud–Aerosol Lidar with Orthogonal Polarization [onboard the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO)] are used to analyze cloud distributions associated with TCs. Evidence is found that convective clouds within TCs reach the upper part of the tropical tropopause layer (TTL) more frequently than do convective clouds outside TCs, raising the possibility that convective clouds within TCs and associated cirrus clouds modulate TLC. The contribution of clouds to radiative heating rates is then quantified using the CloudSat and CALIPSO datasets: in the lower TTL (below the tropopause), clouds produce longwave cooling of order 0.1–1 K day−1 inside the TC main convective region, and longwave warming of order 0.01–0.1 K day−1 outside; in the upper TTL (near and above the tropopause), clouds produce longwave cooling of the same order as TLC inside the TC main convective region, and up to one order of magnitude smaller outside. Considering that clouds also produce shortwave warming, it is suggested that cloud radiative effects inside and outside TCs only explain modest amounts of TLC while other processes must provide the remaining cooling.

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