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

2013 ◽  
Vol 13 (17) ◽  
pp. 8623-8642 ◽  
Author(s):  
Y. Inai ◽  
F. Hasebe ◽  
M. Fujiwara ◽  
M. Shiotani ◽  
N. Nishi ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Water Vapor ◽  
Deep Convection ◽  
Water Injection ◽  
Equatorial Region ◽  
Screening Tests ◽  
Tropical Tropopause Layer ◽  
Horizontal Advection ◽  
Tropical Tropopause ◽  
Time Required

Abstract. We apply the match technique, whereby the same air mass is observed more than once and such cases are termed a "match", to study the dehydration process associated with horizontal advection in the tropical tropopause layer (TTL) over the western Pacific. The matches are obtained from profile data taken by the Soundings of Ozone and Water in the Equatorial Region (SOWER) campaign network observations using isentropic trajectories calculated from European Centre for Medium-Range Weather Forecasts (ECMWF) operational analyses. For the matches 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 referring to the ozone conservation. Among the matches that passed the screening tests, we identified 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 matches. The threshold of nucleation is estimated to be 146 ± 1% (1σ) in relative humidity with respect to ice (RHice), while dehydration seems to continue until RHice reaches about 75 ± 23% (1σ) in the altitude region from 350 to 360 K. The efficiency of dehydration expressed by the relaxation time required for the supersaturated air parcel to approach saturation is empirically determined from the matches. A relaxation time of approximately one hour reproduces the second water vapor observation reasonably well, given the first observed water vapor amount and the history of the saturation mixing ratio during advection in the lower TTL.

scholarly journals Bridging the gap between bromocarbon oceanic emissions and upper air concentrations

2012 ◽  
Vol 12 (2) ◽  
pp. 4477-4505 ◽  
Author(s):  
S. Tegtmeier ◽  
K. Krüger ◽  
B. Quack ◽  
I. Pisso ◽  
A. Stohl ◽  
...  
Keyword(s):  
Transport Model ◽  
Degradation Products ◽  
Source Region ◽  
Western Pacific ◽  
Emission Rates ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Oceanic Emissions ◽  
Atmospheric Concentrations ◽  
The Western Pacific

Abstract. Oceanic emissions of halogenated very short-lived substances (VSLS) are expected to contribute significantly to the stratospheric halogen loading and therefore to ozone depletion. Estimates of the amount of VSLS transported into the stratosphere are highly uncertain and based on sporadic observations around the tropical tropopause layer (TTL) and on modeling studies which use prescribed emission scenarios to reproduce observed atmospheric concentrations. Actual measurements of VSLS emissions at the ocean surface have not been linked to the stratospheric halogen loading until now. Here we use observations of oceanic VSLS emissions in the western Pacific and an atmospheric Lagrangian transport model to estimate the direct contribution of bromoform (CHBr3), and dibromomethane (CH2Br2) to the stratospheric bromine loading. Our emission-based estimates of VSLS profiles provide the first link between observed oceanic emissions and in situ TTL measurements. The emission-based and observed profiles of CHBr3 show good agreement, confirming the importance of the western Pacific as a source region. However, CH2Br2 emission-based estimates are considerable smaller than current upper air observations as a result of relatively low western Pacific emissions. We estimate the relative importance of the highly variable emission rates and the surface to stratosphere transport for the contribution of the two bromocarbons to the stratospheric bromine budget. Our results show that stratospheric entrainment of bromine in form of VSLS or their degradation products is highly variable and that this variability is primarily linked to the variability of the observed sea-to-air flux. Together, both bromocarbons contribute to the stratospheric bromine budget with 0.4 pptv on average and 2.3 pptv for cases of maximum emissions.

scholarly journals Cirrus observations in the tropical tropopause layer over the western Pacific

2009 ◽  
Vol 114 (D9) ◽  
Author(s):  
M. Fujiwara ◽  
S. Iwasaki ◽  
A. Shimizu ◽  
Y. Inai ◽  
M. Shiotani ◽  
...  
Keyword(s):  
Western Pacific ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
The Western Pacific

scholarly journals Modeling the inorganic bromine partitioning in the tropical tropopause layer over the eastern and western Pacific Ocean

2017 ◽  
Vol 17 (16) ◽  
pp. 9917-9930 ◽  
Author(s):  
Maria A. Navarro ◽  
Alfonso Saiz-Lopez ◽  
Carlos A. Cuevas ◽  
Rafael P. Fernandez ◽  
Elliot Atlas ◽  
...  
Keyword(s):  
Heterogeneous Reactions ◽  
Western Pacific ◽  
Eastern Pacific ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Community Atmosphere Model ◽  
Reservoir Species ◽  
The Pacific ◽  
Climate Simulations ◽  
The Western Pacific

Abstract. The stratospheric inorganic bromine (Bry) burden arising from the degradation of brominated very short-lived organic substances (VSLorg) and its partitioning between reactive and reservoir species is needed for a comprehensive assessment of the ozone depletion potential of brominated trace gases. Here we present modeled inorganic bromine abundances over the Pacific tropical tropopause based on aircraft observations of VSLorg from two campaigns of the Airborne Tropical TRopopause EXperiment (ATTREX 2013, carried out over the eastern Pacific, and ATTREX 2014, carried out over the western Pacific) and chemistry-climate simulations (along ATTREX flight tracks) using the specific meteorology prevailing. Using the Community Atmosphere Model with Chemistry (CAM-Chem) we model that BrO and Br are the daytime dominant species. Integrated across all ATTREX flights, BrO represents ∼ 43 and 48 % of daytime Bry abundance at 17 km over the western and eastern Pacific, respectively. The results also show zones where Br / BrO > 1 depending on the solar zenith angle (SZA), ozone concentration, and temperature. On the other hand, BrCl and BrONO2 were found to be the dominant nighttime species with ∼  61 and 56 % of abundance at 17 km over the western and eastern Pacific, respectively. The western-to-eastern differences in the partitioning of inorganic bromine are explained by different abundances of ozone (O3), nitrogen dioxide (NO2), total inorganic chlorine (Cly), and the efficiency of heterogeneous reactions of bromine reservoirs (mostly BrONO2 and HBr) occurring on ice crystals.

scholarly journals In situ observations of dehydrated air parcels advected horizontally in the Tropical Tropopause Layer of the western Pacific

2007 ◽  
Vol 7 (3) ◽  
pp. 803-813 ◽  
Author(s):  
F. Hasebe ◽  
M. Fujiwara ◽  
N. Nishi ◽  
M. Shiotani ◽  
H. Vömel ◽  
...  
Keyword(s):  
Water Vapor ◽  
Temperature History ◽  
Vapor Concentration ◽  
Tropical Tropopause Layer ◽  
Horizontal Advection ◽  
Tropical Tropopause ◽  
History Of ◽  
In Situ Observations ◽  
The Western Pacific

Abstract. Water vapor observations by chilled-mirror hygrometers were conducted at Bandung, Indonesia (6.90° S, 107.60° E) and Tarawa, Kiribati (1.35° N, 172.91° E) in December 2003 to examine the efficiency of dehydration during horizontal advection in the tropical tropopause layer (TTL). Trajectory analyses based on bundles of isentropic trajectories suggest that the modification of air parcels' identity due to irreversible mixing by the branching-out and merging-in of nearby trajectories is found to be an important factor, in addition to the routes air parcels follow, for interpreting the water vapor concentrations observed by chilled-mirror frostpoint hygrometers in the TTL. Clear correspondence between the observed water vapor concentration and the estimated temperature history of air parcels is found showing that drier air parcels were exposed to lower temperatures than were more humid ones during advection. Although the number of observations is quite limited, the water content in the observed air parcels on many occasions was more than that expected from the minimum saturation mixing ratio during horizontal advection prior to sonde observations.

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 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.

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