scholarly journals Physical processes controlling the spatial distributions of relative humidity in the tropical tropopause layer over the Pacific

2017 ◽  
Vol 122 (11) ◽  
pp. 6094-6107 ◽  
Author(s):  
Eric J. Jensen ◽  
Troy D. Thornberry ◽  
Andrew W. Rollins ◽  
Rei Ueyama ◽  
Leonhard Pfister ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Spatial Distributions ◽  
Physical Processes ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
The Pacific

scholarly journals Impact of gravity waves on the motion and distribution of atmospheric ice particles

2018 ◽  
Vol 18 (14) ◽  
pp. 10799-10823 ◽  
Author(s):  
Aurélien Podglajen ◽  
Riwal Plougonven ◽  
Albert Hertzog ◽  
Eric Jensen
Keyword(s):  
Relative Humidity ◽  
Gravity Waves ◽  
Ice Crystals ◽  
Lapse Rate ◽  
Temperature Lapse Rate ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Ice Particles ◽  
The Pacific ◽  
The Impact

Abstract. Gravity waves are an ubiquitous feature of the atmosphere and influence clouds in multiple ways. Regarding cirrus clouds, many studies have emphasized the impact of wave-induced temperature fluctuations on the nucleation of ice crystals. This paper investigates the impact of the waves on the motion and distribution of ice particles, using the idealized 2-D framework of a monochromatic gravity wave. Contrary to previous studies, special attention is given to the impact of the wind field induced by the wave. Assuming no feedback of the ice on the water vapor content, theoretical and numerical analyses both show the existence of a wave-driven localization of ice crystals, where some ice particles remain confined in a specific phase of the wave. The precise location where the confinement occurs depends on the background relative humidity, but it is always characterized by a relative humidity near saturation and a positive vertical wind anomaly. Hence, the wave has an impact on the mean motion of the crystals and may reduce dehydration in cirrus by slowing down the sedimentation of the ice particles. The results also provide a new insight into the relation between relative humidity and ice crystals' presence. The wave-driven localization is consistent with temperature–cirrus relationships recently observed in the tropical tropopause layer (TTL) over the Pacific during the Airborne Tropical Tropopause EXperiment (ATTREX). It is argued that this effect may explain such observations. Finally, the impact of the described interaction on TTL cirrus dehydration efficiency is quantified using ATTREX observations of clouds and temperature lapse rate.

scholarly journals Impact of gravity waves on the motion and distribution of atmospheric ice particles

2017 ◽  
Author(s):  
Aurélien Podglajen ◽  
Riwal Plougonven ◽  
Albert Hertzog ◽  
Eric Jensen
Keyword(s):  
Relative Humidity ◽  
Gravity Waves ◽  
Ice Crystals ◽  
Lapse Rate ◽  
Temperature Lapse Rate ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Ice Particles ◽  
The Pacific ◽  
The Impact

Abstract. Gravity waves are an ubiquitous feature of the atmosphere and influence clouds in multiple ways. Regarding cirrus clouds, many studies have emphasized the impact of wave-induced temperature fluctuations on the nucleation of ice crystals. This paper investigates the impact of the waves on the motion and distribution of ice particles, using the idealized 2-D framework of a monochromatic gravity wave. Contrary to previous studies, a special attention is given to the impact of the wind field induced by the wave. Assuming no feedback of the ice on the water vapor content, theoretical and numerical analyses both show the existence of a wave-driven localization of ice crystals, where some ice particles remain confined in a specific phase of the wave. The precise location where the confinement occurs depends on the background relative humidity, but it is always characterized by a relative humidity near saturation and a positive vertical wind anomaly. Hence, the wave has an impact on the mean motion of the crystals and may reduce dehydration in cirrus by slowing down the sedimentation of the ice particles. The results also provide a new insight into the relation between relative humidity and ice crystals presence. The wave-driven localization is consistent with temperature-cirrus relationships recently observed in the tropical tropopause layer (TTL) over the Pacific during the Airborne Tropical Tropopause EXperiment (ATTREX). It is argued that this effect may explain such observations. Finally, the impact of the described interaction on TTL cirrus dehydration efficiency is quantified using ATTREX observations of clouds and temperature lapse rate.

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 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 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 Airborne measurements of organic bromine compounds in the Pacific tropical tropopause layer

2015 ◽  
Vol 112 (45) ◽  
pp. 13789-13793 ◽  
Author(s):  
Maria A. Navarro ◽  
Elliot L. Atlas ◽  
Alfonso Saiz-Lopez ◽  
Xavier Rodriguez-Lloveras ◽  
Douglas E. Kinnison ◽  
...  
Keyword(s):  
Ozone Depletion ◽  
Lower Stratosphere ◽  
Climate Model ◽  
Accurate Estimation ◽  
Tropical Tropopause Layer ◽  
Airborne Measurements ◽  
Tropical Tropopause ◽  
The Pacific ◽  
Aircraft Observations ◽  
The Tropical Pacific

Very short-lived brominated substances (VSLBr) are an important source of stratospheric bromine, an effective ozone destruction catalyst. However, the accurate estimation of the organic and inorganic partitioning of bromine and the input to the stratosphere remains uncertain. Here, we report near-tropopause measurements of organic brominated substances found over the tropical Pacific during the NASA Airborne Tropical Tropopause Experiment campaigns. We combine aircraft observations and a chemistry−climate model to quantify the total bromine loading injected to the stratosphere. Surprisingly, despite differences in vertical transport between the Eastern and Western Pacific, VSLBr (organic + inorganic) contribute approximately similar amounts of bromine [∼6 (4−9) parts per thousand] to the stratospheric input at the tropical tropopause. These levels of bromine cause substantial ozone depletion in the lower stratosphere, and any increases in future abundances (e.g., as a result of aquaculture) will lead to larger depletions.

Annual, Interannual, and Intraseasonal Variability of Tropical Tropopause Transition Layer Cirrus

2010 ◽  
Vol 67 (10) ◽  
pp. 3097-3112 ◽  
Author(s):  
Katrina S. Virts ◽  
John M. Wallace
Keyword(s):  
Annual Cycle ◽  
El Niño ◽  
Transition Layer ◽  
El Nino ◽  
Southern Oscillation ◽  
Cirrus Clouds ◽  
Boreal Winter ◽  
Central Pacific ◽  
Tropical Tropopause ◽  
The Pacific

Abstract Cloud fields based on the first three years of data from the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission are used to investigate the relationship between cirrus within the tropical tropopause transition layer (TTL) and the Madden–Julian oscillation (MJO), the annual cycle, and El Niño–Southern Oscillation (ENSO). The TTL cirrus signature observed in association with the MJO resembles convectively induced, mixed Kelvin–Rossby wave solutions above the Pacific warm pool region. This signature is centered to the east of the peak convection and propagates eastward more rapidly than the convection; it exhibits a pronounced eastward tilt with height, suggestive of downward phase propagation and upward energy dispersion. A cirrus maximum is observed over equatorial Africa and South America when the enhanced MJO-related convection enters the western Pacific. Tropical-mean TTL cirrus is modulated by the MJO, with more than twice as much TTL cirrus fractional coverage equatorward of 10° latitude when the enhanced convection enters the Pacific than a few weeks earlier, when the convection is over the Indian Ocean. The annual cycle in cirrus clouds around the base of the TTL is equatorially asymmetric, with more cirrus observed in the summer hemisphere. Higher in the TTL, the annual cycle in cirrus clouds is more equatorially symmetric, with a maximum in the boreal winter throughout most of the tropics. The ENSO signature in TTL cirrus is marked by a zonal shift of the peak cloudiness toward the central Pacific during El Niño and toward the Maritime Continent during La Niña.

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