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.

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

2021 ◽  
Author(s):  
Jing Feng ◽  
Yi Huang
Keyword(s):  
Water Vapor ◽  
Tropical Cyclones ◽  
Distribution Patterns ◽  
Radiative Heating ◽  
Radiative Cooling ◽  
Heating Rates ◽  
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, 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.

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

2007 ◽  
Vol 7 (5) ◽  
pp. 13989-14010 ◽  
Author(s):  
K. Krüger ◽  
S. Tegtmeier ◽  
M. Rex
Keyword(s):  
Mass Transport ◽  
Volcanic Eruptions ◽  
Radiative Heating ◽  
Residual Circulation ◽  
Heating Rates ◽  
Air Mass ◽  
Tropical Tropopause Layer ◽  
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.

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

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 Layer ◽  
Tropical Tropopause ◽  
Tropopause Region ◽  
The Impact

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.

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 radiative role of ozone and water vapour in the temperature annual cycle in the tropical tropopause layer

2016 ◽  
Author(s):  
Alison Ming ◽  
Amanda C. Maycock ◽  
Peter Hitchcock ◽  
Peter Haynes
Keyword(s):  
Water Vapour ◽  
Annual Cycle ◽  
Temperature Response ◽  
Radiative Heating ◽  
Latitudinal Gradients ◽  
Peak Amplitude ◽  
Tropical Tropopause Layer ◽  
Enhanced Absorption ◽  
Tropical Tropopause ◽  
Cold Point

Abstract. The prominent annual cycle in temperatures (with maximum peak to peak amplitude of ~ 8 K around 70 hPa and ~ 6 K at 90 hPa) is a key feature of the tropical tropopause layer (TTL). There is also a strong annual cycle observed in both ozone and water vapour in the TTL, with the latter understood as a consequence of the temperature annual cycle. The radiative contributions of the annual cycle in ozone and water vapour to the temperature annual cycle are studied, first with a seasonally evolving fixed dynamical heating calculation (SEFDH) where the dynamical heating is assumed to be unaffected by the radiative heating. In this framework, the variations in ozone and water vapour derived from satellite data lead to variations in temperature that are respectively in phase and out of phase with the observed annual cycle. The ozone contribution is at the upper range of previous calculations. This difference in phasing can be understood from the fact that an increase in water vapour cools the TTL, predominantly through enhanced local emission, whereas an increase in ozone warms the TTL, mostly through enhanced absorption of upwelling longwave radiation from the troposphere. The relative phasing of the water vapour and ozone effects on temperature is further influenced by the fact that for water vapour there is a strong non-local effect on temperatures from variations in concentrations occurring in lower layers of the TTL. In contrast, for ozone it is the local variations in concentration that have the strongest impact on local temperature variations. The factors that determine the vertical structure of the annual cycle in temperature are also examined. Radiative damping time scales are shown to maximize over a broad layer centred on the cold point. Non-radiative processes in the upper troposphere are inferred to impose a strong constraint on temperature perturbations below 130 hPa. These effects, combined with the annual cycles in dynamical and radiative heating, which both peak above the cold point, result in a maximum amplitude of temperature response that is relatively localized around 70 hPa. Finally, the SEFDH assumption is relaxed by considering the temperature responses to ozone and water vapour variations in a zonally symmetric dynamical model. While the magnitude of the tropical averaged temperature annual cycle in this framework is found to be consistent with the SEFDH results, the effects of the dynamical adjustment act to reduce the strong latitudinal gradients and inter-hemispheric asymmetry in the temperature response. This results in a temperature response that shows a considerably smoother structure than inferred from the SEFDH model. Whilst precise numerical values are likely to be sensitive to changes in the details of radiation code and of ozone and water vapour concentrations, the net contribution to the annual cycle in temperature from both ozone and water vapour averaged between 20° N–S, calculated in this work, is substantial and around 35 % of the observed peak to peak amplitude at both 70 hPa and 90 hPa.

scholarly journals The roles of convection, extratropical mixing, and in-situ freeze-drying in the Tropical Tropopause Layer

2008 ◽  
Vol 8 (20) ◽  
pp. 6051-6067 ◽  
Author(s):  
W. G. Read ◽  
M. J. Schwartz ◽  
A. Lambert ◽  
H. Su ◽  
N. J. Livesey ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Quantitative Agreement ◽  
Radiative Heating ◽  
Cold Trap ◽  
Neutral Buoyancy ◽  
Tropical Tropopause Layer ◽  
Convective Mixing ◽  
Tropical Tropopause ◽  
Trace Species ◽  
Cold Point

Abstract. Mechanisms for transporting and dehydrating air across the tropical tropopause layer (TTL) are investigated with a conceptual two dimensional (2-D) model. The 2-D TTL model combines the Holton and Gettelman cold trap dehydration mechanism (Holton and Gettelman, 2001) with the two column convection model of Folkins and Martin (2005). We investigate 3 possible transport scenarios through the TTL: 1) slow uniform ascent across the level of zero radiative heating without direct convective mixing, 2) convective mixing of H2O vapor at 100% relative humidity with respect to ice (RHi) with no ice retention, and 3) convective mixing of extremely subsaturated air (100% RHi following the moist adiabatic temperature above the level of neutral buoyancy) with sufficient ice retention such that total H2O is 100%RHi. The three mechanisms produce similar seasonal cycles for H2O that are in good quantitative agreement with the Aura Microwave Limb Sounder (MLS) measurements. We use Aura MLS measurement of CO and Atmospheric Chemistry Experiment-Fourier Transform Spectrometer measurement of HDO to distinguish among the transport mechanisms. Model comparisons with the observations support the view that H2O is predominantly controlled by regions having the lowest cold point tropopause temperature but the trace species CO and HDO support the convective mixing of dry air and lofted ice. The model provides some insight into the processes affecting the long term trends observed in stratospheric H2O.

scholarly journals The role of tropical deep convective clouds on temperature, water vapor, and dehydration in the tropical tropopause layer (TTL)

2010 ◽  
Vol 10 (4) ◽  
pp. 8963-8994 ◽  
Author(s):  
J. H. Chae ◽  
D. L. Wu ◽  
W. G. Read ◽  
S. C. Sherwood
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Temperature Drop ◽  
Critical Factor ◽  
Tropical Tropopause Layer ◽  
Convective Clouds ◽  
Tropical Tropopause ◽  
Dehydration Mechanism ◽  
Environmental Air ◽  
Cloud Tops

Abstract. Temperature and water vapor variations due to clouds in the TTL have been investigated using co-located MLS, CALISPO, and CloudSat data. Convective cooling occurs only up to cloud top heights, but there is warming above these heights in the TTL. Water vapor and ozone anomalies above cloud top heights support that the warming anomalies occur due to downward motion. Thicker clouds cause a greater magnitude of the temperature anomalies. Water vapor of the environment below cloud tops can either increase or decrease, depending on the cloud top height. The critical factor, which divides these different water vapor variations below cloud tops, is the relative humidity. Clouds hydrate the environment below 16 km, where the air after mixing between cloud and the environmental air does not reach saturation, but clouds dehydrate above 16 km, due to the supersaturation because of the larger temperature drop and the high initial relative humidity. Water vapor above cloud tops has negative anomalies compared to clear skies and suggests another dehydration mechanism.

scholarly journals Short-lived brominated hydrocarbons – observations in the source regions and the tropical tropopause layer

2012 ◽  
Vol 12 (3) ◽  
pp. 1213-1228 ◽  
Author(s):  
S. Brinckmann ◽  
A. Engel ◽  
H. Bönisch ◽  
B. Quack ◽  
E. Atlas
Keyword(s):  
Marine Boundary Layer ◽  
Sampling Technique ◽  
Radiative Heating ◽  
Western Pacific ◽  
Data Set ◽  
Tropical Tropopause Layer ◽  
Mixing Ratios ◽  
Tropical Tropopause ◽  
Linear Relationships ◽  
Made In

Abstract. We conducted measurements of the five important short-lived organic bromine species in the marine boundary layer (MBL). Measurements were made in the Northern Hemisphere mid-latitudes (Sylt Island, North Sea) in June 2009 and in the tropical Western Pacific during the TransBrom ship campaign in October 2009. For the one-week time series on Sylt Island, mean mixing ratios of CHBr3, CH2Br2, CHBr2Cl and CH2BrCl were 2.0, 1.1, 0.2, 0.1 ppt, respectively. We found maxima of 5.8 and 1.6 ppt for the two main components CHBr3 and CH2Br2. Along the cruise track in the Western Pacific (between 41° N and 13° S) we measured mean mixing ratios of 0.9, 0.9, 0.2, 0.1 and 0.1 ppt for CHBr3, CH2Br2, CHBrCl2, CHBr2Cl and CH2BrCl. Air samples with coastal influence showed considerably higher mixing ratios than the samples with open ocean origin. Correlation analyses of the two data sets yielded strong linear relationships between the mixing ratios of four of the five species (except for CH2BrCl). Using a combined data set from the two campaigns and a comparison with the results from two former studies, rough estimates of the molar emission ratios between the correlated substances were: 9/1/0.35/0.35 for CHBr3/CH2Br2/CHBrCl2/CHBr2Cl. Additional measurements were made in the tropical tropopause layer (TTL) above Teresina (Brazil, 5° S) in June 2008, using balloon-borne cryogenic whole air sampling technique. Near the level of zero clear-sky net radiative heating (LZRH) at 14.8 km about 2.25 ppt organic bromine was bound to the five short-lived species, making up 13% of total organic bromine (17.82 ppt). CH2Br2 (1.45 ppt) and CHBr3 (0.56 ppt) accounted for 90% of the budget of short-lived compounds in that region. Near the tropopause (at 17.5 km) organic bromine from these substances was reduced to 1.35 ppt, with 1.07 and 0.12 ppt attributed to CH2Br2 and CHBr3, respectively.

scholarly journals Convective sources of trajectories traversing the tropical tropopause layer

2016 ◽  
Vol 16 (5) ◽  
pp. 3383-3398 ◽  
Author(s):  
Ann-Sophie Tissier ◽  
Bernard Legras
Keyword(s):  
Mass Flux ◽  
Asian Monsoon ◽  
Warm Pool ◽  
Monsoon Region ◽  
Heating Rates ◽  
Asian Monsoon Region ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Transit Times ◽  
Cloud Tops

Abstract. Transit properties across the tropical tropopause layer are studied using extensive forward and backward Lagrangian diabatic trajectories between cloud tops and the reference surface 380 K. After dividing the tropical domain into 11 subregions according to the distribution of land and convection, we estimate the contribution of each region to the upward mass flux across the 380 K surface and to the vertical distribution of convective sources and transit times over the period 2005–2008. The good agreement between forward and backward statistics is the basis of the results presented here. It is found that about 85 % of the tropical parcels at 380 K originate from convective sources throughout the year. From November to April, the sources are dominated by the warm pool which accounts for up to 70 % of the upward flux. During boreal summer, the Asian monsoon region is the largest contributor with similar contributions from the maritime and continental parts of the region; however, the vertical distributions and transit times associated with these two subregions are very different. Convective sources are generally higher over the continental part of the Asian monsoon region, with shorter transit times. We estimate the monthly averaged upward mass flux on the 380 K surface and show that the contribution from convective outflow accounts for 80 % on average and explains most of its seasonal variations. The largest contributor to the convective flux is the South Asian Pacific region (warm pool) at 39 % throughout the year followed by oceanic regions surrounding continental Asia at 18 % and Africa at 10.8 %. Continental Asian lowlands account for 8 %. The Tibetan Plateau is a minor overall contributor (0.8 %), but transport from convective sources in this region is very efficient due to its central location beneath the Asian upper level anticyclone. The core results are robust to uncertainties in data and methods, but the vertical source distributions and transit times exhibit some sensitivity to the representations of cloud tops and heating rates. The main sensitivity is to the radiative heating rates which vary among reanalyses.

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