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

Tropical Tropopause ◽

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, although this impact is poorly quantified due to the lack of collocated data. To address this problem, we implement a synergistic retrieval approach to obtain the thermodynamic profiles and ice water content above thick high-level clouds using the A-Train satellite measurements that pass over the tropical cyclones. This study detects the signature of cyclone impact on the distribution patterns of cloud, water vapor, temperature, and radiation by compositing these thermodynamic fields with respect to cyclone center locations. It is found that tropical cyclone events considerably increase the occurrence 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 convections that penetrate the bottom of TTL. Using the synergistic retrieval 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. The atmospheric column above 16 km is generally hydrated by overshooting convections, although dehydration is detected above non-overshooting TTL clouds. Above overshooting deep convections, the column-integrated water vapor is found to be on average 40 % higher than the climatology. Moreover, the TTL above tropical cyclones is cooled due to longwave radiative cooling. The radiative heating rates above cyclones are well differentiated by the brightness temperature of a satellite infrared channel in the window band. Using radiative calculations, it is found that TTL hydration is usually associated with radiative cooling of the TTL, which inhibits the diabatic ascent of moist air. The radiative balance of the TTL under the impact of the cyclone, therefore, is not in favor of maintaining the moist anomalies in the TTL or transporting water vertically to the stratosphere.

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

10.5194/acp-21-15493-2021 ◽

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 ◽

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.

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

Journal of Climate ◽

10.1175/jcli-d-19-0813.1 ◽

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 ◽

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.

Effect of deep convection on the tropical tropopause layer composition over the southwest Indian Ocean during austral summer

10.5194/acp-20-10565-2020 ◽

2020 ◽

Vol 20 (17) ◽

pp. 10565-10586

Author(s):

Stephanie Evan ◽

Jerome Brioude ◽

Karen Rosenlof ◽

Sean M. Davis ◽

Holger Vömel ◽

...

Keyword(s):

Water Vapor ◽

Indian Ocean ◽

Tropical Cyclones ◽

Austral Summer ◽

Lagrangian Model ◽

Southwest Indian Ocean ◽

Tropical Tropopause ◽

Tropopause Region ◽

Abstract. Balloon-borne measurements of cryogenic frost-point hygrometer (CFH) water vapor, ozone and temperature and water vapor lidar measurements from the Maïdo Observatory on Réunion Island in the southwest Indian Ocean (SWIO) were used to study tropical cyclones' influence on tropical tropopause layer (TTL) composition. The balloon launches were specifically planned using a Lagrangian model and Meteosat-7 infrared images to sample the convective outflow from tropical storm (TS) Corentin on 25 January 2016 and tropical cyclone (TC) Enawo on 3 March 2017. Comparing the CFH profile to Aura's Microwave Limb Sounder's (MLS) monthly climatologies, water vapor anomalies were identified. Positive anomalies of water vapor and temperature, and negative anomalies of ozone between 12 and 15 km in altitude (247 to 121 hPa), originated from convectively active regions of TS Corentin and TC Enawo 1 d before the planned balloon launches according to the Lagrangian trajectories. Near the tropopause region, air masses on 25 January 2016 were anomalously dry around 100 hPa and were traced back to TS Corentin's active convective region where cirrus clouds and deep convective clouds may have dried the layer. An anomalously wet layer around 68 hPa was traced back to the southeast Indian Ocean where a monthly water vapor anomaly of 0.5 ppmv was observed. In contrast, no water vapor anomaly was found near or above the tropopause region on 3 March 2017 over Maïdo as the tropopause region was not downwind of TC Enawo. This study compares and contrasts the impact of two tropical cyclones on the humidification of the TTL over the SWIO. It also demonstrates the need for accurate balloon-borne measurements of water vapor, ozone and aerosols in regions where TTL in situ observations are sparse.

The impact of temperature vertical structure on trajectory modeling of stratospheric water vapor

10.5194/acp-15-3517-2015 ◽

2015 ◽

Vol 15 (6) ◽

pp. 3517-3526 ◽

Cited By ~ 15

Author(s):

T. Wang ◽

A. E. Dessler ◽

M. R. Schoeberl ◽

W. J. Randel ◽

J.-E. Kim

Keyword(s):

Water Vapor ◽

Vertical Structure ◽

Vertical Resolution ◽

Stratospheric Water Vapor ◽

Dry Air ◽

Tropical Tropopause ◽

Cold Point ◽

The Impact ◽

Modern Era

Abstract. Lagrangian trajectories driven by reanalysis meteorological fields are frequently used to study water vapor (H2O) in the stratosphere, in which the tropical cold-point temperatures regulate the amount of H2O entering the stratosphere. Therefore, the accuracy of temperatures in the tropical tropopause layer (TTL) is of great importance for understanding stratospheric H2O abundances. Currently, most reanalyses, such as the NASA MERRA (Modern Era Retrospective – analysis for Research and Applications), only provide temperatures with ~ 1.2 km vertical resolution in the TTL, which has been argued to miss finer vertical structure in the tropopause and therefore introduce uncertainties in our understanding of stratospheric H2O. In this paper, we quantify this uncertainty by comparing the Lagrangian trajectory prediction of H2O using MERRA temperatures on standard model levels (traj.MER-T) to those using GPS temperatures at finer vertical resolution (traj.GPS-T), and those using adjusted MERRA temperatures with finer vertical structures induced by waves (traj.MER-Twave). It turns out that by using temperatures with finer vertical structure in the tropopause, the trajectory model more realistically simulates the dehydration of air entering the stratosphere. But the effect on H2O abundances is relatively minor: compared with traj.MER-T, traj.GPS-T tends to dry air by ~ 0.1 ppmv, while traj.MER-Twave tends to dry air by 0.2–0.3 ppmv. Despite these differences in absolute values of predicted H2O and vertical dehydration patterns, there is virtually no difference in the interannual variability in different runs. Overall, we find that a tropopause temperature with finer vertical structure has limited impact on predicted stratospheric H2O.

Contribution of different processes to changes in tropical lower-stratospheric water vapor in chemistry–climate models

10.5194/acp-17-8031-2017 ◽

2017 ◽

Vol 17 (13) ◽

pp. 8031-8044 ◽

Cited By ~ 12

Author(s):

Kevin M. Smalley ◽

Andrew E. Dessler ◽

Slimane Bekki ◽

Makoto Deushi ◽

Marion Marchand ◽

...

Keyword(s):

Water Vapor ◽

Regression Model ◽

21St Century ◽

Climate Models ◽

Quasi Biennial Oscillation ◽

Stratospheric Water Vapor ◽

Tropical Tropopause ◽

Abstract. Variations in tropical lower-stratospheric humidity influence both the chemistry and climate of the atmosphere. We analyze tropical lower-stratospheric water vapor in 21st century simulations from 12 state-of-the-art chemistry–climate models (CCMs), using a linear regression model to determine the factors driving the trends and variability. Within CCMs, warming of the troposphere primarily drives the long-term trend in stratospheric humidity. This is partially offset in most CCMs by an increase in the strength of the Brewer–Dobson circulation, which tends to cool the tropical tropopause layer (TTL). We also apply the regression model to individual decades from the 21st century CCM runs and compare them to a regression of a decade of observations. Many of the CCMs, but not all, compare well with these observations, lending credibility to their predictions. One notable deficiency is that most CCMs underestimate the impact of the quasi-biennial oscillation on lower-stratospheric water vapor. Our analysis provides a new and potentially superior way to evaluate model trends in lower-stratospheric humidity.

Hydration of the tropical tropopause layer (TTL) by convective updraft during tropical cyclone ENAWO(2017) and generalization to tropical storms in the southwestern Indian Ocean in summer 2016-2017.

10.5194/egusphere-egu2020-12643 ◽

2020 ◽

Author(s):

Damien Héron ◽

Stephanie Evan ◽

Jerome Brioude ◽

Joris Pianezze ◽

Thibault Dauhut ◽

...

Keyword(s):

Water Vapor ◽

Tropical Cyclone ◽

Indian Ocean ◽

Tropical Cyclones ◽

Mesoscale Model ◽

Cirrus Clouds ◽

Water Vapor Transport ◽

Tropical Tropopause ◽

Southwestern Indian Ocean

Stratospheric water vapor variations play an important role on the climate. Predictions of changes in stratospheric humidity are uncertain because of gaps in our understanding of physical processes occurring in the TTL, between 14 and 20 km altitude. In particular, climate models have great difficulties in modelling water vapor variations in the TTL due to a poor representation of tropical convection, which largely controls the vertical transport of water vapor to UTLS, among other things.One of the scientific objectives of the CONCIRTO5 program is to better understand the role of marine deep convective systems, and tropical cyclones in particular, on the hydration of TTL in the Southwestern Indian Ocean.&#160; In March 2017, a rapid deepening of the tropical cyclone Enawo occured north-west of Reunion island before to strike and cross Madagascar from north to south. The progressive intensification of the cyclone to the intense tropical cyclone stage makes it an ideal case study to analyze the transport of water vapor and hydrometeors in the TTL according to the intensity phase of the cyclone.&#160;We will present modelling results on water vapor transport into the TTL in March 4 during ENAWO&#8217;s intensification. On March 4, the mesoscale model Meso-NH simulated a large water vapour transport through the TTL, associated with the injection of ice through the tropopause and the observation of cirrus clouds. The model validation is done by comparison with satellite data (CALIPSO, Meteosat-8). We generalize the intrusion modelling during ENAWO intensification by comparing the brightness temperature observed above the tropical cyclones and the tropical tropopause temperature extracted from ECMWF-Analysis during the 2016-2017 cyclonic season. From these studies, we can estimate the number of intrusions during a cyclonic season and the cyclonic intensity associated with the intrusions.&#160;5Effects of convection and cirrus clouds on the Tropical Tropopause Layer over the Indian Ocean

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

10.5194/acp-2017-951 ◽

2017 ◽

Cited By ~ 1

Author(s):

Hao Ye ◽

Andrew E. Dessler ◽

Wandi Yu

Keyword(s):

Water Vapor ◽

Interannual Variability ◽

Deep Convection ◽

Tropospheric Temperature ◽

Quasi Biennial Oscillation ◽

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.

Observed Increase of TTL Temperature and Water Vapor in Polluted Clouds over Asia

Journal of Climate ◽

10.1175/2010jcli3749.1 ◽

2011 ◽

Vol 24 (11) ◽

pp. 2728-2736 ◽

Cited By ~ 26

Author(s):

Hui Su ◽

Jonathan H. Jiang ◽

Xiaohong Liu ◽

Joyce E. Penner ◽

William G. Read ◽

...

Keyword(s):

Water Vapor ◽

Radiative Heating ◽

Specific Humidity ◽

Boreal Summer ◽

Boreal Winter ◽

Maritime Continent ◽

Ice Clouds ◽

Tropical Tropopause ◽

Higher Temperature

Abstract Satellite observations are analyzed to examine the correlations between aerosols and the tropical tropopause layer (TTL) temperature and water vapor. This study focuses on two regions, both of which are important pathways for the mass transport from the troposphere to the stratosphere and over which Asian pollution prevails: South and East Asia during boreal summer and the Maritime Continent during boreal winter. Using the upper-tropospheric carbon monoxide measurements from the Aura Microwave Limb Sounder as a proxy of aerosols to classify ice clouds as polluted or clean, the authors find that polluted clouds have a smaller ice effective radius and a higher temperature and specific humidity near the tropopause than clean clouds. The increase in water vapor appears to be related to the increase in temperature, as a result of increased aerosols. Meteorological differences between the clouds cannot explain the differences in temperature and water vapor for the polluted and clean clouds. The authors hypothesize that aerosol semidirect radiative heating and/or changes in cirrus radiative heating, resulting from aerosol microphysical effects on clouds, may contribute to the increased TTL temperature and thus increased water vapor in the polluted clouds.

The Impact of Cloud Radiative Effects on the Tropical Tropopause Layer Temperatures

Atmosphere ◽

10.3390/atmos9100377 ◽

2018 ◽

Vol 9 (10) ◽

pp. 377 ◽

Cited By ~ 4

Author(s):

Qiang Fu ◽

Maxwell Smith ◽

Qiong Yang

Keyword(s):

Maximum Temperature ◽

Radiative Effects ◽

Heating Rates ◽

Tropical Tropopause ◽

Cloud Radiative Effect ◽

Single Column ◽

Cloud Radiative Effects ◽

Cold Point ◽

A single-column radiative-convective model (RCM) is a useful tool to investigate the physical processes that determine the tropical tropopause layer (TTL) temperature structures. Previous studies on the TTL using the RCMs, however, omitted the cloud radiative effects. In this study, we examine the impact of cloud radiative effects on the simulated TTL temperatures using an RCM. We derive the cloud radiative effects based on satellite observations, which show heating rates in the troposphere but cooling rates in the stratosphere. We find that the cloud radiative effect warms the TTL by as much as 2 K but cools the lower stratosphere by as much as −1.5 K, resulting in a thicker TTL. With (without) considering cloud radiative effects, we obtain a convection top of ≈167 hPa (≈150 hPa) with a temperature of ≈213 K (≈209 K), and a cold point at ≈87 hPa (≈94 hPa) with a temperature of ≈204 K (≈204 K). Therefore, the cloud radiative effects widen the TTL by both lowering the convection-top height and enhancing the cold-point height. We also examine the impact of TTL cirrus radiative effects on the RCM-simulated temperatures. We find that the TTL cirrus warms the TTL with a maximum temperature increase of ≈1.3 K near 110 hPa.

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

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-7-13989-2007 ◽

2007 ◽

Vol 7 (5) ◽

pp. 13989-14010 ◽

Cited By ~ 2

Author(s):

K. Krüger ◽

S. Tegtmeier ◽

M. Rex

Keyword(s):

Mass Transport ◽

Volcanic Eruptions ◽

Radiative Heating ◽

Residual Circulation ◽

Heating Rates ◽

Air Mass ◽

Tropical Tropopause ◽

Improved Performance

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 TTL, the averaged diabatic ascent is 0.5 K/day during Northern Hemisphere (NH) winters 1992–2001, close to observations from the tape recorder. Climatological maps show a cooling and strengthening of this part of the residual circulation during the late 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 are found to be influenced by volcanic eruptions, ENSO, QBO and the solar cycle. The coldest and driest TTL is reached during QBOE and La Niña over the western Pacific, whereas during volcanic eruptions, El Niño and QBOW it is warmer and less dry.