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

2011 ◽  
Vol 11 (1) ◽  
pp. 163-192 ◽  
Author(s):  
J. P. Vernier ◽  
J. P. Pommereau ◽  
L. W. Thomason ◽  
J. Pelon ◽  
A. Garnier ◽  
...  
Keyword(s):  
Transport Process ◽  
Lower Stratosphere ◽  
Thermal Structure ◽  
Radiative Heating ◽  
Convective Activity ◽  
Upper Troposphere ◽  
Tropical Tropopause Layer ◽  
Volcanic Plumes ◽  
Tropical Tropopause ◽  
Hemisphere Winter

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 of the lower stratosphere to altitudes as high as 20 km. The cleansing of the full 14–20 km layer takes place within 1–4 months. Its coincidence with the maximum of convective activity in the southern tropics, suggests that the cleansing is the result of a large number of overshooting towers, injecting aerosol-poor tropospheric air into the lower stratosphere. The enhancements of aerosols at the tropopause level during the NH summer may be due to the same transport process but associated with intense sources of aerosols at the surface. Since, the tropospheric air flux derived from CALIOP observations during North Hemisphere winter is 5–20 times larger than the slow ascent by radiative heating usually assumed, the observations suggest that convective overshooting is a major contributor to troposphere-to-stratosphere transport with concommitant implications to the Tropical Tropopause Layer top height, chemistry and thermal structure.

scholarly journals Effect of tropical cyclones on the tropical tropopause parameters observed using COSMIC GPS RO data

2015 ◽  
Vol 15 (18) ◽  
pp. 10239-10249 ◽  
Author(s):  
S. Ravindra Babu ◽  
M. Venkat Ratnam ◽  
G. Basha ◽  
B. V. Krishnamurthy ◽  
B. Venkateswararao
Keyword(s):  
Tropical Cyclones ◽  
Lower Stratosphere ◽  
Thermal Structure ◽  
Radial Distance ◽  
Lapse Rate ◽  
Tropical Tropopause Layer ◽  
Water Vapour Transport ◽  
Tropical Tropopause ◽  
High Vertical Resolution ◽  
Cold Point

Abstract. Tropical cyclones (TCs) are deep convective synoptic-scale systems that play an important role in modifying the thermal structure, tropical tropopause parameters and hence also modify stratosphere–troposphere exchange (STE) processes. In the present study, high vertical resolution and high accuracy measurements from COSMIC Global Positioning System (GPS) radio occultation (RO) measurements are used to investigate and quantify the effect of tropical cyclones that occurred over Bay of Bengal and Arabian Sea in the last decade on the tropical tropopause parameters. The tropopause parameters include cold-point tropopause altitude (CPH) and temperature (CPT), lapse-rate tropopause altitude (LRH) and temperature (LRT) and the thickness of the tropical tropopause layer (TTL), that is defined as the layer between convective outflow level (COH) and CPH, obtained from GPS RO data. From all the TC events, we generate the mean cyclone-centred composite structure for the tropopause parameters and removed it from the climatological mean obtained from averaging the GPS RO data from 2002 to 2013. Since the TCs include eye, eye walls and deep convective bands, we obtained the tropopause parameters based on radial distance from the cyclone eye. In general, decrease in the CPH in the eye is noticed as expected. However, as the distance from the cyclone eye increases by 300, 400, and 500 km, an enhancement in CPH (CPT) and LRH (LRT) is observed. Lowering of CPH (0.6 km) and LRH (0.4 km) values with coldest CPT and LRT (2–3 K) within a 500 km radius of the TC centre is noticed. Higher (2 km) COH leading to the lowering of TTL thickness (2–3 km) is clearly observed. There are multiple tropopause structures in the profiles of temperature obtained within 100 km from the centre of the TC. These changes in the tropopause parameters are expected to influence the water vapour transport from the troposphere to the lower stratosphere, and ozone from the lower stratosphere to the upper troposphere, hence influencing STE processes.

scholarly journals The impact of overshooting deep convection on local transport and mixing in the tropical upper troposphere/lower stratosphere (UTLS)

2015 ◽  
Vol 15 (11) ◽  
pp. 6467-6486 ◽  
Author(s):  
W. Frey ◽  
R. Schofield ◽  
P. Hoor ◽  
D. Kunkel ◽  
F. Ravegnani ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Deep Convection ◽  
Horizontal Resolution ◽  
Transport Processes ◽  
Convective System ◽  
Upper Troposphere ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Transport And Mixing ◽  
The Impact

Abstract. In this study we examine the simulated downward transport and mixing of stratospheric air into the upper tropical troposphere as observed on a research flight during the SCOUT-O3 campaign in connection with a deep convective system. We use the Advanced Research Weather and Research Forecasting (WRF-ARW) model with a horizontal resolution of 333 m to examine this downward transport. The simulation reproduces the deep convective system, its timing and overshooting altitudes reasonably well compared to radar and aircraft observations. Passive tracers initialised at pre-storm times indicate the downward transport of air from the stratosphere to the upper troposphere as well as upward transport from the boundary layer into the cloud anvils and overshooting tops. For example, a passive ozone tracer (i.e. a tracer not undergoing chemical processing) shows an enhancement in the upper troposphere of up to about 30 ppbv locally in the cloud, while the in situ measurements show an increase of 50 ppbv. However, the passive carbon monoxide tracer exhibits an increase, while the observations show a decrease of about 10 ppbv, indicative of an erroneous model representation of the transport processes in the tropical tropopause layer. Furthermore, it could point to insufficient entrainment and detrainment in the model. The simulation shows a general moistening of air in the lower stratosphere, but it also exhibits local dehydration features. Here we use the model to explain the processes causing the transport and also expose areas of inconsistencies between the model and observations.

scholarly journals Effect of tropical cyclones on the tropical tropopause parameters observed using COSMIC GPS RO data

2015 ◽  
Vol 15 (9) ◽  
pp. 13043-13071
Author(s):  
S. Ravindra Babu ◽  
M. Venkat Ratnam ◽  
Ghouse Basha ◽  
B. V. Krishnamurthy ◽  
B. Venkateswara Rao
Keyword(s):  
Tropical Cyclones ◽  
Lower Stratosphere ◽  
Thermal Structure ◽  
Radial Distance ◽  
Lapse Rate ◽  
Tropical Tropopause Layer ◽  
Water Vapour Transport ◽  
Tropical Tropopause ◽  
High Vertical Resolution ◽  
Cold Point

Abstract. Tropical cyclones (TCs) are deep convective synoptic scale systems and play an important role in modifying the thermal structure, tropical tropopause parameters and hence stratosphere–troposphere exchange (STE) processes. In the present study, high vertical resolution and high accuracy measurements from COSMIC Global Positioning System (GPS) Radio Occultation (RO) measurements are used to investigate and quantify the effect of tropical cyclones that occurred over Bay of Bengal and Arabian Sea in last decade on the tropical tropopause parameters. The tropopause parameters include cold point tropopause altitude (CPH) and temperature (CPT), lapse rate tropopause altitude (LRH) and temperature (LRT) and the thickness of the tropical tropopause layer (TTL), that is defined as the layer between convective outflow level (COH) and CPH, obtained from GPS RO data. From all the TCs events, we generate the mean cyclone-centered composite structure for the tropopause parameters and removed from climatological mean obtained from averaging the GPS RO data from 2002–2013. Since the TCs include eye, eye walls and deep convective bands, we obtained the tropopause parameters based on radial distance from cyclone eye. In general, decrease in the CPH in the eye is noticed as expected. However, as the distance from cyclone eye increases by 3, 4, and 5° an enhancement in CPH (CPT), LRH (LRT) are observed. Lowering of CPH (0.6 km) and LRH (0.4 km) values with coldest CPT and LRT (2–3 K) within the 500 km radius from the TC centre is noticed. Higher (2 km) COH leading to the lowering of TTL thickness (2–3 km) is clearly observed. There exists multiple tropopause structures in the profiles of temperature obtained within 1° from centre of TC. These changes in the tropopause parameters are expected to influence the water vapour transport from troposphere to lower stratosphere and ozone from lower stratosphere to the upper troposphere and hence STE processes.

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 The impact of overshooting deep convection on local transport and mixing in the tropical upper troposphere/lower stratosphere (UTLS)

2015 ◽  
Vol 15 (1) ◽  
pp. 1041-1091 ◽  
Author(s):  
W. Frey ◽  
R. Schofield ◽  
P. Hoor ◽  
D. Kunkel ◽  
F. Ravegnani ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Deep Convection ◽  
Horizontal Resolution ◽  
Transport Processes ◽  
Convective System ◽  
Upper Troposphere ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Transport And Mixing ◽  
The Impact

Abstract. In this study we examine the simulated downward transport and mixing of stratospheric air into the upper tropical troposphere as observed on a research flight during the SCOUT-O3 campaign in connection to a deep convective system. We use the Advanced Research Weather and Research Forecasting (WRF-ARW) model with a horizontal resolution of 333 m to examine this downward transport. The simulation reproduces the deep convective system, its timing and overshooting altitudes reasonably well compared to radar and aircraft observations. Passive tracers initialised at pre-storm times indicate the downward transport of air from the stratosphere to the upper troposphere as well as upward transport from the boundary layer into the cloud anvils and overshooting tops. For example, a passive ozone tracer (i.e. a tracer not undergoing chemical processing) shows an enhancement in the upper troposphere of up to about 30 ppbv locally in the cloud, while the in situ measurements show an increase of 50 ppbv. However, the passive carbon monoxide tracer exhibits an increase, while the observations show a decrease of about 10 ppbv, indicative of an erroneous model representation of the transport processes in the tropical tropopause layer. Furthermore, it could point to insufficient entrainment and detrainment in the model. The simulation shows a general moistening of air in the lower stratosphere but it also exhibits local dehydration features. Here we use the model to explain the processes causing the transport and also expose areas of inconsistencies between the model and observations.

scholarly journals Impact of land convection on the thermal structure of the lower stratosphere as inferred from COSMIC GPS radio occultations

2013 ◽  
Vol 13 (1) ◽  
pp. 1-31 ◽  
Author(s):  
S. M. Khaykin ◽  
J.-P. Pommereau ◽  
A. Hauchecorne
Keyword(s):  
Lower Stratosphere ◽  
Thermal Structure ◽  
Geographical Location ◽  
Temperature Cycle ◽  
Tropical Tropopause Layer ◽  
Convective Systems ◽  
Tropical Tropopause ◽  
The Difference ◽  
Strong Injection ◽  
Cold Point

Abstract. Following recent studies evidencing the effect of deep overshooting convection on the chemical composition of the tropical lower stratosphere by injection of tropospheric air across the cold-point tropopause we explore its impact on the thermal structure of the tropical tropopause layer (TTL) and the lower stratosphere using the high-resolution COSMIC GPS radio-occultation temperature measurements spanning from 2006 through 2011. The temperature of the lower tropical stratosphere is shown to display a systematic mean cooling of 0.6 K up to 20 km in the late afternoon in the summer over land compared to oceanic areas where little or no diurnal variation is observed. The temperature cycle is fully consistent with the diurnal cycle and geographical location of deep convective systems reported by the Tropical Rainfall Measurement Mission (TRMM) precipitation radar suggesting strong injection of adiabatically cooled air into the lower tropical stratosphere in the afternoon over tropical continents. But most unexpected is the difference between the southern and Northern Hemispheres, the first displaying systematic larger cooling suggesting more intense convection in the southern than in the northern tropics.

Influence of Upper-Troposphere Stratification and Cloud-Radiation Interaction on Convective Overshoots in the Tropical Tropopause Layer

2021 ◽  
Author(s):  
Zeyuan Hu ◽  
Fayçal Lamraoui ◽  
Zhiming Kuang
Keyword(s):  
Vertical Velocity ◽  
Large Scale ◽  
Cloud Microphysics ◽  
Horizontal Resolution ◽  
Radiative Heating ◽  
Soft Landing ◽  
Upper Troposphere ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
The Difference

AbstractIt is still debated whether radiative heating observed in the tropical tropopause layer (TTL) is balanced primarily by cooling from convective overshoots, as in an entrainment layer, or by adiabatic cooling from large-scale eddy-driven upwelling. In this study, three-dimensional cloud-resolving model simulations of radiative-convective equilibrium were carried out with three different cloud microphysics schemes and 1-km horizontal resolution. We demonstrate that overshooting cooling in the TTL can be strongly modulated by upper-troposphere stratification. Two of the schemes produce a hard-landing scenario in which convective overshoots reach the TTL with frequent large vertical velocity leading to strong overshooting cooling (~ −0.2 K day-1). The third scheme produces a soft-landing scenario in which convective overshoots rarely reach the TTL with large vertical velocity and produce little overshooting cooling (~ −0.03 K day-1). The difference between the two scenarios is attributed to changes in the upper-troposphere stratification related to different atmospheric cloud radiative effects (ACRE). The microphysics scheme that produces the soft-landing scenario has much stronger ACRE in the upper troposphere leading to a ~3K warmer and more stable layer which acts as a buffer zone to slow down the convective updrafts. The stratification mechanism suggests the possibility for the ozone variation or eddy-driven upwelling in the TTL to modulate convective overshoots. We further test the sensitivity of overshooting cooling to changes in model resolution by increasing the horizontal resolution to 100 m. The corresponding change of overshooting cooling is much smaller compared with the difference between the hard-landing and soft-landing scenarios.

scholarly journals VARIASI TRACE GASES SELAMA 10 TAHUN DAN PENCAMPURAN DI SEKITAR LAPISAN TROPOPAUSE DI INDONESIA BERBASIS SATELIT (TRACE GASES VARIATION FOR 10 YEARS AND MIXING AROUND THE TROPOPAUSE LAYERS IN INDONESIA BASED ON SATELLITE)

2018 ◽  
Vol 14 (2) ◽  
pp. 83
Author(s):  
Novita Ambarsari ◽  
Ninong Komala ◽  
Fanny Aditya Putri
Keyword(s):  
Time Series ◽  
Cross Section ◽  
Lower Stratosphere ◽  
Trace Gases ◽  
Radiation Budget ◽  
Vertical Profiles ◽  
Upper Troposphere ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Budget Analysis

Measurement of trace gases (CO, O3, CH3Cl, HCl, H2O, and HNO3) and temperatures around upper troposphere/lower stratosphere (UT/LS) or rather around Tropical Tropopause Layer (TTL) in Indonesia by using Microwave Limb Sounder (MLS) instrument board on Satellite AURA for 2005-2014 period to make variations of these gases over the 10 years around TTL allows to be studied more deeply. TTL becomes the main route entry of chemical compounds and aerosols originating in the troposphere into the stratosphere. The composition of minor gases in the TTL is very important because it affects the global radiation budget. Analysis of vertical profiles of these gases in the TTL was done to determine the suitability of the concept of TTL which starts from the upper troposphere to the lower stratosphere. Other method are the time series diagram of the altitude (height versus time series cross section) which shows the annual and interannual variations in vertical profiles of these gases in the TTL and the possible influence of the dynamics of the atmosphere. The results showed correlation of these gases with ozone showed most of the air in the stratosphere is experiencing mixing in the TTL. In addition, changes in concentration and temperature values in the TTL have been calculated using the trends of each parameter and it is known that the parameters of HCl, CH3Cl, and temperature show respective decreases of -0.036 ppmv, -0.024 ppmv, and -0.456 K. As for other parameters such as ozone, CO, H2O, and HNO3 showed an increase of respectively 0.0036 ppmv, 0.0096 ppmv, 0.108 ppmv, and 0.06 ppmv. AbstrakPengukuran trace gases (CO, O3, CH3Cl, HCl, H2O, HNO3) dan temperatur di sekitar lapisan troposfer atas/stratosfer bawah (UT/LS) atau tepatnya di sekitar Tropical Tropopause Layer (TTL) di Indonesia menggunakan instrumen Microwave Limb Sounder (MLS) pada Satelit AURA periode 2005-2014 menjadikan variasi gas-gas tersebut selama 10 tahun di sekitar TTL memungkinkan untuk dikaji lebih dalam. TTL menjadi jalur utama masuknya senyawa-senyawa kimia dan aerosol yang bersumber di troposfer ke stratosfer. Komposisi gas-gas minor di TTL sangat penting karena mempengaruhi budget radiasi global. Analisis profil vertikal gas-gas tersebut di TTL dilakukan untuk mengetahui kesesuaian konsep TTL yang dimulai dari lapisan troposfer atas hingga ke stratosfer bawah. Metode lainnya adalah dengan diagram time series terhadap ketinggian (time series versus height cross section) yang menunjukkan variasi tahunan maupun antar tahunan profil vertikal gas-gas tersebut di TTL serta kemungkinan adanya pengaruh dari proses dinamika atmosfer. Hasil penelitian menunjukkan korelasi gas-gas tersebut dengan ozon menunjukkan adanya sebagian udara di stratosfer yang mengalami pencampuran di wilayah TTL. Selain itu, perubahan nilai konsentrasi dan temperatur di TTL telah dihitung menggunakan trend masing-masing parameter dan diketahui bahwa parameter HCl, CH3Cl, dan temperatur menunjukkan penurunan masing-masing sebesar  -0,036 ppmv, -0,024 ppmv, dan -0,456 K. Adapun parameter lain seperti ozon, CO, H2O, dan HNO3 menunjukkan adanya peningkatan masing-masing sebesar 0,0036 ppmv, 0,0096 ppmv, 0,108 ppmv, dan 0,06 ppmv.  

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