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

2011 ◽  
Vol 11 (8) ◽  
pp. 3811-3821 ◽  
Author(s):  
J. H. Chae ◽  
D. L. Wu ◽  
W. G. Read ◽  
S. C. Sherwood
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Temperature Drop ◽  
Critical Factor ◽  
Environmental Water ◽  
Tropical Tropopause Layer ◽  
Convective Clouds ◽  
Tropical Tropopause ◽  
Environmental Air ◽  
Cloud Tops

Abstract. Temperature and water vapor variations due to clouds in the tropical tropopause layer (TTL) are investigated using co-located MLS, CALIPSO, and CloudSat data. Convective cooling occurs only up to the cloud tops, with warming above these heights in the TTL. Water vapor and ozone anomalies above the cloud tops are consistent with the warming being due to downward motion. Thicker clouds are associated with larger anomalies. Environmental water vapor below cloud tops can be either higher or lower than when clouds are absent, depending on the cloud top height. The critical factor determining the sign of this change appears to be the relative humidity. In general cloud-forming processes 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, as the larger temperature drop and the high initial relative humidity cause supersaturation to occur. Negative water vapor anomalies above cloud tops compared to clear skies suggest another dehydration mechanism operating above the detected cloud layers.

scholarly journals Dehydration in the tropical tropopause layer estimated from the water vapor match

2013 ◽  
Vol 13 (1) ◽  
pp. 633-688 ◽  
Author(s):  
Y. Inai ◽  
F. Hasebe ◽  
M. Fujiwara ◽  
M. Shiotani ◽  
N. Nishi ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Water Vapor ◽  
Relative Humidity ◽  
Western Pacific ◽  
Dehydration Process ◽  
Saturation State ◽  
Air Mass ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
The Western Pacific

Abstract. Variation in stratospheric water vapor is controlled mainly by the dehydration process in the tropical tropopause layer (TTL) over the western Pacific; however, this process is poorly understood. To address this shortcoming, in this study the match method is applied to quantify the dehydration process in the TTL over the western Pacific. The match pairs are sought from the Soundings of Ozone and Water in the Equatorial Region (SOWER) campaign network observations using isentropic trajectories. For the pairs identified, extensive screening procedures are performed to verify the representativeness of the air parcel and the validity of the isentropic treatment, and to check for possible water injection by deep convection, consistency between the sonde data and analysis field, and conservation of the ozone content. Among the pairs that passed the screening test, we found some cases corresponding to the first quantitative value of dehydration associated with horizontal advection in the TTL. The statistical features of dehydration for the air parcels advected in the lower TTL are derived from the match pairs. Match analysis indicates that ice nucleation starts before the relative humidity with respect to ice (RHice) reaches 207 ± 81% (1σ) and that the air mass is dehydrated until RHice reaches 83 ± 30% (1σ). The efficiency of dehydration is estimated as the relaxation time required for the relative humidity of the supersaturated air parcel to approach the saturation state. This is empirically estimated from the match pairs as the quantity that reproduces the second water vapor observation, given the first observed water vapor amount and the history of the saturation mixing ratio of the match air mass exposed during the advection. The relaxation time is found to range from 2 to 3 h, which is consistent with previous studies.

scholarly journals Modeling upper tropospheric and lower stratospheric water vapor anomalies

2013 ◽  
Vol 13 (4) ◽  
pp. 9653-9679 ◽  
Author(s):  
M. R. Schoeberl ◽  
A. E. Dessler ◽  
T. Wang
Keyword(s):  
Water Vapor ◽  
Lower Stratosphere ◽  
Calculation Model ◽  
Vapor Concentration ◽  
Cold Temperatures ◽  
Tropical Tropopause Layer ◽  
Stratospheric Water Vapor ◽  
Tropical Tropopause ◽  
Minimum Displacement ◽  
Asian Monsoons

Abstract. The domain-filling, forward trajectory calculation model developed by Schoeberl and Dessler (2011) is used to further investigate processes that produce upper tropospheric and lower stratospheric water vapor anomalies. We examine the pathways parcels take from the base of the tropical tropopause layer (TTL) to the lower stratosphere. Most parcels found in the lower stratosphere arise from East Asia, the Tropical West Pacific (TWP) and the Central/South America. The belt of TTL parcel origins is very wide compared to the final dehydration zones near the top of the TTL. This is due to the convergence of rising air as a result of the stronger diabatic heating near the tropopause relative to levels above and below. The observed water vapor anomalies – both wet and dry – correspond to regions where parcels have minimal displacement from their initialization. These minimum displacement regions include the winter TWP and the Asian and American monsoons. To better understand the stratospheric water vapor concentration we introduce the water vapor spectrum and investigate the source of the wettest and driest components of the spectrum. We find that the driest air parcels that originate below the TWP, moving upward to dehydrate in the TWP cold upper troposphere. The wettest air parcels originate at the edges of the TWP as well as the summer American and Asian monsoons. The wet air parcels are important since they skew the mean stratospheric water vapor distribution toward higher values. Both TWP cold temperatures that produce dry parcels as well as extra-TWP processes that control the wet parcels determine stratospheric water vapor.

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 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 A model of HDO in the tropical tropopause layer

2003 ◽  
Vol 3 (6) ◽  
pp. 2173-2181 ◽  
Author(s):  
A. E. Dessler ◽  
S. C. Sherwood
Keyword(s):  
Water Vapor ◽  
Isotopic Composition ◽  
Vertical Profile ◽  
Tropical Tropopause Layer ◽  
Physical Constraints ◽  
Dry Air ◽  
Tropical Tropopause

Abstract. Any theory of water vapor in the tropical tropopause layer (TTL) must explain both the abundance and isotopic composition of water there. In previous papers, we presented a model of the TTL that simulated the abundance of water vapor as well as the details of the vertical profile. That model included the effects of "overshooting" convection, which injects dry air directly into the TTL. Here, we present results for the model after modifying it to include water's stable isotopologue HDO (where D represents deuterium, 2H). We find that the model predicts a nearly uniform HDO depletion throughout the TTL, in agreement with recent measurements. This occurs because the model dehydrates by dilution, which does not fractionate, instead of by condensation. Our model shows that this dehydration by dilution is consistent with other physical constraints on the system. We also show the key role that lofted ice plays in determining the abundance of HDO in the TTL. Such lofted ice requires a complementary source of dry air in the TTL; without that, the TTL will rapidly saturate and the lofted ice will not evaporate.

scholarly journals A 1D RCE Study of Factors Affecting the Tropical Tropopause Layer and Surface Climate

2019 ◽  
Vol 32 (20) ◽  
pp. 6769-6782 ◽  
Author(s):  
Sally Dacie ◽  
Lukas Kluft ◽  
Hauke Schmidt ◽  
Bjorn Stevens ◽  
Stefan A. Buehler ◽  
...  
Keyword(s):  
Water Vapor ◽  
Climate Models ◽  
Temperature Response ◽  
Global Climate Models ◽  
Lapse Rate ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Surface Climate ◽  
Ozone Profile ◽  
Convective Adjustment

Abstract There are discrepancies between global climate models regarding the evolution of the tropical tropopause layer (TTL) and also whether changes in ozone impact the surface under climate change. We use a 1D clear-sky radiative–convective equilibrium model to determine how a variety of factors can affect the TTL and how they influence surface climate. We develop a new method of convective adjustment, which relaxes the temperature profile toward the moist adiabat and allows for cooling above the level of neutral buoyancy. The TTL temperatures in our model are sensitive to CO2 concentration, ozone profile, the method of convective adjustment, and the upwelling velocity, which is used to calculate a dynamical cooling rate in the stratosphere. Moreover, the temperature response of the TTL to changes in each of the above factors sometimes depends on the others. The surface temperature response to changes in ozone and upwelling at and above the TTL is also strongly amplified by both stratospheric and tropospheric water vapor changes. With all these influencing factors, it is not surprising that global models disagree with regard to TTL structure and evolution and the influence of ozone changes on surface temperatures. On the other hand, the effect of doubling CO2 on the surface, including just radiative, water vapor, and lapse-rate feedbacks, is relatively robust to changes in convection, upwelling, or the applied ozone profile.

scholarly journals Water Vapor, Clouds, and Saturation in the Tropical Tropopause Layer

2019 ◽  
Vol 124 (7) ◽  
pp. 3984-4003 ◽  
Author(s):  
M. R. Schoeberl ◽  
E. J. Jensen ◽  
L. Pfister ◽  
R. Ueyama ◽  
T. Wang ◽  
...  
Keyword(s):  
Water Vapor ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause

scholarly journals Radiative Impacts of the 2011 Abrupt Drops in Water Vapor and Ozone in the Tropical Tropopause Layer

2016 ◽  
Vol 29 (2) ◽  
pp. 595-612 ◽  
Author(s):  
Daniel M. Gilford ◽  
Susan Solomon ◽  
Robert W. Portmann
Keyword(s):  
Water Vapor ◽  
Radiative Forcing ◽  
Tropical Tropopause Layer ◽  
Stratospheric Water Vapor ◽  
Tropical Tropopause ◽  
Radiative Impacts ◽  
Radiative Impact ◽  
Rf Values ◽  
Mean Structure ◽  
Large Water

Abstract An abrupt drop in tropical tropopause layer (TTL) water vapor, similar to that observed in 2000, recently occurred in 2011, and was concurrent with reductions in TTL temperature and ozone. Previous studies have indicated that such large water vapor variability can have significant radiative impacts. This study uses Aura Microwave Limb Sounder observations, the Stratospheric Water Vapor and Ozone Satellite Homogenized dataset, and two radiative transfer models to examine the radiative effects of the observed changes in TTL water vapor and ozone on TTL temperatures and global radiative forcing (RF). The analyses herein suggest that quasi-isentropic poleward propagation of TTL water vapor reductions results in a zonal-mean structure with “wings” of extratropical water vapor reductions, which account for about half of the 2011 abrupt drop global radiative impact. RF values associated with the mean water vapor concentrations differences between 2012/13 and 2010/11 are between −0.01 and −0.09 W m−2, depending upon the altitude above which perturbations are considered. TTL water vapor and ozone variability during this period jointly lead to a transient radiative cooling of ~0.25–0.5 K in layers below the tropopause. The 2011 abrupt drop also prolonged the reduction in stratospheric water vapor that followed the 2000 abrupt drop, providing a longer-term radiative forcing of climate. Water vapor concentrations from 2005 to 2013 are lower than those from 1990 to 1999, resulting in a RF between these periods of about −0.045 W m−2, approximately 12% as large as, but of opposite sign to, the concurrent estimated CO2 forcing.

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