Equatorial belt vapour measurements in the upper TTL under superpressure balloon during STRATEOLE 2 pre-campaign: tape recorder effect, role of waves and deep convection.

2021 ◽  
Author(s):  
Emmanuel Riviere ◽  
Mélanie Ghysels ◽  
Georges Durry ◽  
Jérémie Burgalat ◽  
Nadir Amarouche ◽  
...  
Keyword(s):  
Water Vapour ◽  
Lower Stratosphere ◽  
Deep Convection ◽  
Tape Recorder ◽  
Kelvin Wave ◽  
Water Vapour Content ◽  
The Pacific ◽  
Equatorial Belt ◽  
Local Water ◽  
Constant Altitude

<p>STRATEOLE 2 is a French-American project based on superpressure balloon borne measurements to study dynamics and processes in the TTL and the lower stratosphere of equatorial regions. One single flight of these balloons (of a duration of about 80 days) can make several turns of the Earth.</p><p>Here we present water vapour measurements by the Pico-SDLA infrared laser spectrometer on-board the TTL 2 gondola. The float altitude was of about 19 km during the technical campaign of STRATEOLE 2, providing measurements at the top of the TTL or the lower stratosphere. In this presentation, we analyse the tape recorder signal at a constant altitude during the 80 days of flight. We compute an anomaly of the <em>in situ</em> water vapour measurements with respect to a regional/temporal satellite-borne mean climatology from Aura MLS. It allows to analyse the local measurements by Pico-SDLA with respect to what is expected at a given position and a given time. The obtained contrast allows the positioning of observations with respect to local climatology and therefore, the identification of singular events responsible for modulation of the local water vapour content. Our analysis shows that a long wet anomaly above the Pacific Ocean is explained by the balloon “surfing” on a warm perturbation of a Kelvin wave. Concurrently, a dry anomaly is put to the fore over the Indian Ocean, associated to a packet of gravity waves cold perturbations. The balloon has flown twice above the Maritime Continent. For each passage, a short scale succession of dry and wet anomalies is shown, indicating a possible influence of local deep convection. This influence is studied further using satellite borne cloud top data.</p>

scholarly journals Convective hydration in the tropical tropopause layer during the StratoClim aircraft campaign: pathway of an observed hydration patch

2019 ◽  
Vol 19 (18) ◽  
pp. 11803-11820 ◽  
Author(s):  
Keun-Ok Lee ◽  
Thibaut Dauhut ◽  
Jean-Pierre Chaboureau ◽  
Sergey Khaykin ◽  
Martina Krämer ◽  
...  
Keyword(s):  
Water Vapour ◽  
Lower Stratosphere ◽  
Asian Summer Monsoon ◽  
Great Part ◽  
The South ◽  
Water Vapour Content ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Water Vapour Concentration ◽  
Ice Content

Abstract. The source and pathway of the hydration patch in the TTL (tropical tropopause layer) that was measured during the Stratospheric and upper tropospheric processes for better climate predictions (StratoClim) field campaign during the Asian summer monsoon in 2017 and its connection to convective overshoots are investigated. During flight no. 7, two remarkable layers are measured in the TTL, namely (1) the moist layer (ML) with a water vapour content of 4.8–5.7 ppmv in altitudes of 18–19 km in the lower stratosphere and (2) the ice layer (IL) with ice content up to 1.9 eq. ppmv (equivalent parts per million by volume) in altitudes of 17–18 km in the upper troposphere at around 06:30 UTC on 8 August to the south of Kathmandu (Nepal). A Meso-NH convection-permitting simulation succeeds in reproducing the characteristics of the ML and IL. Through analysis, we show that the ML and IL are generated by convective overshoots that occurred over the Sichuan Basin about 1.5 d before. Overshooting clouds develop at altitudes up to 19 km, hydrating the lower stratosphere of up to 20 km with 6401 t of water vapour by a strong-to-moderate mixing of the updraughts with the stratospheric air. A few hours after the initial overshooting phase, a hydration patch is generated, and a large amount of water vapour (above 18 ppmv) remains at even higher altitudes up to 20.5 km while the anvil cloud top descends to 18.5 km. At the same time, a great part of the hydrometeors falls shortly, and the water vapour concentration in the ML and IL decreases due to turbulent diffusion by mixing with the tropospheric air, ice nucleation, and water vapour deposition. As the hydration patch continues to travel toward the south of Kathmandu, tropospheric tracer concentration increases up to ∼30 % and 70 % in the ML and IL, respectively. The air mass in the layers becomes gradually diffused, and it has less and less water vapour and ice content by mixing with the dry tropospheric air.

scholarly journals Annual cycle of water vapour in the lower stratosphere over the Indian Peninsula derived from Cryogenic Frost-point Hygrometer observations

2018 ◽  
Author(s):  
Maria Emmanuel ◽  
Sukumarapillai V. Sunilkumar ◽  
Muhsin Muhammed ◽  
Buduru Suneel Kumar ◽  
Nagendra Neerudu ◽  
...  
Keyword(s):  
Water Vapour ◽  
Summer Monsoon ◽  
Lower Stratosphere ◽  
Indian Subcontinent ◽  
Monsoon Season ◽  
Deep Convection ◽  
Equatorial Station ◽  
Post Monsoon ◽  
Frost Point ◽  
Stratospheric Water Vapour

Abstract. In situ measurements of lower stratospheric water vapour employing Cryogenic Frost point Hygrometer (CFH) over two tropical stations, Trivandrum (8.53 °N, 76.87 °E) and Hyderabad (17.47 °N, 78.58 °E) over the Indian subcontinent are conducted as part of Tropical Tropopause Dynamics (TTD) monthly campaigns under GARNETS program. The annual variation of lower stratosphere (LS) water vapour clearly depicts the so called tape recorder effect at both the stations. The ascent rate of water vapour compares well with the velocity of Brewer-Dobson circulation and is slightly higher over the equatorial station when compared to the off-equatorial station. The column integrated water vapour in the LS varies in the range 1.5 to 4 g/m2 with low values during winter and high values during summer monsoon and post monsoon seasons and its variability shows the signatures of local dynamics. The variation in water vapour mixing ratio (WVMR) at the cold point tropopause (CPT) exactly follows the variation in CPT temperature. The difference in WVMR between the stations shows a semi-annual variability in the altitude region 18–20 km region with high values of WVMR during summer monsoon and winter over Hyderabad and during pre-monsoon and post-monsoon over Trivandrum. This difference is related to the influence of the variations in local CPT temperature and deep convection. The monsoon dynamics has a significant role in stratospheric water vapour distribution in summer monsoon season.

scholarly journals Simulation of the isotopic composition of stratospheric water vapour – Part 2: Investigation of HDO/H<sub>2</sub>O variations

2014 ◽  
Vol 14 (21) ◽  
pp. 29459-29497 ◽  
Author(s):  
R. Eichinger ◽  
P. Jöckel ◽  
S. Lossow
Keyword(s):  
Isotopic Composition ◽  
Water Vapour ◽  
Lower Stratosphere ◽  
Hydrological Cycle ◽  
Isotope Ratios ◽  
Tape Recorder ◽  
Boreal Summer ◽  
Substantial Impact ◽  
Stratospheric Water Vapour ◽  
Water Isotope

Abstract. Studying the isotopic composition of water vapour in the lower stratosphere can reveal the driving mechanisms of changes in the stratospheric water vapour budget and therefore help to explain the trends and variations of stratospheric water vapour during the recent decades. We equipped a global chemistry climate model with a description of the water isotopologue HDO, comprising its physical and chemical fractionation effects throughout the hydrological cycle. We use this model to improve our understanding of the processes, which determine the patterns in the stratospheric water isotope composition and in the water vapour budget, itself. The link between the water vapour budget and its isotopic composition in the tropical stratosphere is presented through their correlation in a simulated 21 year time series. The two quantities depend on the same processes, however, are influenced with different strengths. A sensitivity experiment shows that fractionation effects during the oxidation of methane has a damping effect on the stratospheric tape recorder signal in the water isotope ratio. Moreover, the chemically produced high water isotope ratios overshadow the tape recorder in the upper stratosphere. Investigating the origin of the boreal summer tape recorder signal in the lower stratosphere reveals isotopically enriched water vapour crossing the tropopause over the subtropical Western Pacific. A correlation analysis confirms this link, which identifies the Asian Summer Monsoon as the major contributor for the intrusion of isotopically enriched water vapour into the stratosphere during boreal summer. Furthermore, convective ice lofting is shown to have a substantial impact on the isotope ratios of water vapour in the upper troposphere and lower stratosphere.

scholarly journals Variations in the Flow of the Global Atmosphere Associated with a Composite Convectively Coupled Oceanic Kelvin Wave

2010 ◽  
Vol 23 (15) ◽  
pp. 4192-4201 ◽  
Author(s):  
Paul E. Roundy ◽  
Lynn M. Gribble-Verhagen
Keyword(s):  
Southern Oscillation ◽  
Deep Convection ◽  
Composite Analysis ◽  
High Latitudes ◽  
Madden Julian Oscillation ◽  
Global Flow ◽  
Kelvin Wave ◽  
Coupled Mode ◽  
The Pacific ◽  
The Pacific Ocean

Abstract Kelvin waves in the Pacific Ocean occasionally develop and propagate eastward together with anomalies of deep convection and low-level westerly wind. This pattern suggests coupling between the oceanic waves and atmospheric convection. A simple composite analysis based on observed coupled events from October through April demonstrates that this apparent coupled mode is associated with significant large anomalies in the global flow that extend to high latitudes. These high-latitude anomalies are significantly larger than those that are linearly associated with the El Niño–Southern Oscillation (ENSO), and they evolve on time scales between those of the Madden–Julian oscillation and ENSO, potentially providing an opportunity for enhanced subseasonal predictability in the flow of the global atmosphere.

scholarly journals A model study on the influence of overshooting convection on TTL water vapour

2010 ◽  
Vol 10 (20) ◽  
pp. 9833-9849 ◽  
Author(s):  
M. E. E. Hassim ◽  
T. P. Lane
Keyword(s):  
Water Vapour ◽  
Deep Convection ◽  
Three Dimensional ◽  
Direct Role ◽  
Water Vapour Content ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Model Study ◽  
Cloud Resolving Model ◽  
Passive Tracers

Abstract. Overshooting deep convection that penetrates into the Tropical Tropopause Layer (TTL) is thought to have an important role in regulating the water vapour content of this region. Yet, the net effect of such convection and the dominant mechanisms remain unclear. This study uses two idealised three-dimensional cloud-resolving model simulations to examine the influence of overshooting convection on water vapour when it penetrates into two different TTL environments, one supersaturated and the other subsaturated with respect to ice. These simulations show that the overshooting convection plays a direct role in driving the ambient environment towards ice saturation through either net moistening (subsaturated TTL) or net dehydration (supersaturated TTL). Moreover, in these cases the extent of dehydration in supersaturated conditions is greater than the moistening in subsaturated conditions. With the aid of modelled passive tracers, the relative roles of transport, mixing and ice microphysics are assessed; ultimately, ice sublimation and scavenging processes play the most important role in defining the different TTL relative humidity tendencies. In addition, significant moistening in both cases is modelled well into the subsaturated tropical lower stratosphere (up to 450 K), even though the overshooting turrets only reach approximately 420 K. It is shown that this moistening is the result of jumping cirrus, which is induced by the localised upward transport and mixing of TTL air following the collapse of the overshooting turret.

scholarly journals Preliminary signs of the initiation of deep convection by GNSS

2013 ◽  
Vol 13 (11) ◽  
pp. 5425-5449 ◽  
Author(s):  
H. Brenot ◽  
J. Neméghaire ◽  
L. Delobbe ◽  
N. Clerbaux ◽  
P. De Meutter ◽  
...  
Keyword(s):  
Water Vapour ◽  
Time Resolution ◽  
Time Window ◽  
Deep Convection ◽  
Critical Role ◽  
Small Scale ◽  
Convective System ◽  
International Gnss Service ◽  
Total Delay ◽  
Water Vapour Content

Abstract. This study reports on the exploitation of GNSS (Global Navigation Satellite System) and a new potential application for weather forecasts and nowcasting. We focus on GPS observations (post-processing with a time resolution of 5 and 15 min and fast calculations with a time resolution of 5 min) and try to establish typical configurations of the water vapour field which characterise convective systems and particularly which supply precursors of their initiation are associated with deep convection. We show the critical role of GNSS horizontal gradients of the water vapour content to detect small scale structures of the troposphere (i. e. convective cells), and then we present our strategy to obtain typical water vapour configurations by GNSS called "H2O alert". These alerts are based on a dry/wet contrast taking place during a 30 min time window before the initiation of a convective system. GNSS observations have been assessed for the rainfall event of 28–29 June 2005 using data from the Belgian dense network (baseline from 5 to 30 km). To validate our GNSS H2O alerts, we use the detection of precipitation by C-band weather radar and thermal infrared radiance (cloud top temperature) of the 10.8-micrometers channel [Ch09] of SEVIRI instrument on Meteosat Second Generation. Using post-processed measurements, our H2O alerts obtain a score of about 80%. Final and ultra-rapid IGS (International GNSS Service) orbits have been tested and show equivalent results. Fast calculations (less than 10 min) have been processed for 29 June 2005 with a time resolution of 5 min. The mean bias (and standard deviation) between fast and reference post-processed ZTD (zenith total delay) and gradients are, respectively, 0.002 (± 0.008) m and 0.001 (± 0.004) m. The score obtained for the H2O alerts generated by fast calculations is 65%.

scholarly journals Water vapour profiles by ground-based FTIR spectroscopy: study for an optimised retrieval and its validation

2005 ◽  
Vol 5 (5) ◽  
pp. 9493-9545
Author(s):  
M. Schneider ◽  
F. Hase ◽  
T. Blumenstock
Keyword(s):  
Ftir Spectroscopy ◽  
Water Vapour ◽  
Lower Stratosphere ◽  
Spectroscopy Study ◽  
Water Vapour Content ◽  
Signal Ratio ◽  
Upper Troposphere ◽  
Applied Method ◽  
Ftir Technique ◽  
Vertical Gradients

Abstract. The sensitivity of ground-based instruments measuring in the infrared with respect to tropospheric water vapour content is generally limited to the lower and middle troposphere. The large vertical gradients and variabilities avoid a better sensitivity for the upper troposphere/lower stratosphere region. In this work an optimised retrieval is presented and it is demonstrated that compared to a commonly applied method, it widely improves the performance of the FTIR technique with respect to upper tropospheric water vapour. Within a realistic error scenario it is estimated that the optimised method reduces the upper tropospheric uncertainties by about 25–30%, leading to a noise to signal ratio of 50%. The reasons for this improvement and the possible deficiencies of the method are discussed. The estimations are confirmed by a comparison of retrieval results based on real FTIR measurements with coinciding measurements of synoptical meteorological radiosondes.

scholarly journals An overview of the HIBISCUS campaign

2011 ◽  
Vol 11 (5) ◽  
pp. 2309-2339 ◽  
Author(s):  
J.-P. Pommereau ◽  
A. Garnier ◽  
G. Held ◽  
A. M. Gomes ◽  
F. Goutail ◽  
...  
Keyword(s):  
Water Vapour ◽  
Lower Stratosphere ◽  
Deep Convection ◽  
Weather Forecast ◽  
Lapse Rate ◽  
Neutral Buoyancy ◽  
Bromine Oxide ◽  
Tropical Tropopause ◽  
Long Duration ◽  
The Impact

Abstract. The EU HIBISCUS project consisted of a series of field campaigns during the intense convective summers in 2001, 2003 and 2004 in the State of São Paulo in Brazil. Its objective was to investigate the impact of deep convection on the Tropical Tropopause Layer (TTL) and the lower stratosphere by providing a new set of observational data on meteorology, tracers of horizontal and vertical transport, water vapour, clouds, and chemistry in the tropical Upper Troposphere/Lower Stratosphere (UT/LS). This was achieved using short duration research balloons to study local phenomena associated with convection over land, and long-duration balloons circumnavigating the globe to study the contrast between land and oceans. Analyses of observations of short-lived tracers, ozone and ice particles show strong episodic local updraughts of cold air across the lapse rate tropopause up to 18 or 19 km (420–440 K) in the lower stratosphere by overshooting towers. The long duration balloon and satellite measurements reveal a contrast between the composition of the lower stratosphere over land and oceanic areas, suggesting significant global impact of such events. The overshoots are shown to be well captured by non-hydrostatic meso-scale Cloud Resolving Models indicating vertical velocities of 50–60 m s−1 at the top of the Neutral Buoyancy Level (NBL) at around 14 km, but, in contrast, are poorly represented by global Chemistry-Transport Models (CTM) forced by Numerical Weather Forecast Models (NWP) underestimating the overshooting process. Finally, the data collected by the HIBISCUS balloons have allowed a thorough evaluation of temperature NWP analyses and reanalyses, as well as satellite ozone, nitrogen oxide, water vapour and bromine oxide measurements in the tropics.

scholarly journals Simulation of convective moistening of the extratropical lower stratosphere using a numerical weather prediction model

2020 ◽  
Vol 20 (4) ◽  
pp. 2143-2159 ◽  
Author(s):  
Zhipeng Qu ◽  
Yi Huang ◽  
Paul A. Vaillancourt ◽  
Jason N. S. Cole ◽  
Jason A. Milbrandt ◽  
...  
Keyword(s):  
High Resolution ◽  
Water Vapour ◽  
Lower Stratosphere ◽  
Grid Spacing ◽  
Water Vapour Content ◽  
In Situ Observations ◽  
Horizontal Grid ◽  
Stratospheric Water Vapour ◽  
Resolution Simulation

Abstract. Stratospheric water vapour (SWV) is a climatically important atmospheric constituent due to its impacts on the radiation budget and atmospheric chemical composition. Despite the important role of SWV in the climate system, the processes controlling the distribution and variation in water vapour in the upper troposphere and lower stratosphere (UTLS) are not well understood. In order to better understand the mechanism of transport of water vapour through the tropopause, this study uses the high-resolution Global Environmental Multiscale model of the Environment and Climate Change Canada to simulate a lower stratosphere moistening event over North America. Satellite remote sensing and aircraft in situ observations are used to evaluate the quality of model simulation. The main focus of this study is to evaluate the processes that influence the lower stratosphere water vapour budget, particularly the direct water vapour transport and the moistening due to the ice sublimation. In the high-resolution simulations with horizontal grid spacing of less than 2.5 km, it is found that the main contribution to lower stratospheric moistening is the upward transport caused by the breaking of gravity waves. In contrast, for the lower-resolution simulation with horizontal grid spacing of 10 km, the lower stratospheric moistening is dominated by the sublimation of ice. In comparison with the aircraft in situ observations, the high-resolution simulations predict the water vapour content in the UTLS well, while the lower-resolution simulation overestimates the water vapour content. This overestimation is associated with the overly abundant ice in the UTLS along with a sublimation rate that is too high in the lower stratosphere. The results of this study affirm the strong influence of overshooting convection on the lower stratospheric water vapour and highlight the importance of both dynamics and microphysics in simulating the water vapour distribution in the UTLS region.

scholarly journals Analysis of Apparent Coupling between an Oceanic Kelvin Wave and Atmospheric Convection during the Winter of 1986/87

2010 ◽  
Vol 23 (23) ◽  
pp. 6352-6364 ◽  
Author(s):  
Lynn Gribble-Verhagen ◽  
Paul E. Roundy
Keyword(s):  
Deep Convection ◽  
High Amplitude ◽  
Sea Surface ◽  
Madden Julian Oscillation ◽  
Kelvin Wave ◽  
Atmospheric Convection ◽  
Convective Envelope ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Wind Bursts

Abstract This study analyzes the apparent coupling between an intraseasonal oceanic Kelvin wave in the Pacific Ocean and atmospheric moist deep convection for a particularly high-amplitude event during the winter of 1986/87. This wave was initiated initially by westerly wind bursts that developed in association with the Madden–Julian oscillation (MJO). After initiation by the MJO, the active convective anomaly slowed to roughly 1.5 m s−1, suggesting that the event became distinct from the MJO, which usually propagates at roughly 5–7 m s−1. This study demonstrates how surface winds, currents, SST anomalies, fluxes of sensible and latent heat across the sea surface, and atmospheric convection evolve throughout the event. Results suggest that the convective envelope and oceanic Kelvin wave are mutually beneficial and serve to prolong and enhance each other.

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