scholarly journals Diurnal Variability of Lower and Middle Atmospheric Water Vapour Over The Asian Summer Monsoon Region: First Results From COSMIC-1 and TIMED-SABER Measurements

2021 ◽  
Author(s):  
Siddarth Shankar Das ◽  
K N Uma ◽  
K V Suneeth
Keyword(s):  
Water Vapour ◽  
Middle Atmosphere ◽  
Asian Summer Monsoon ◽  
Diurnal Variability ◽  
Diurnal Amplitude ◽  
Tropical Tropopause ◽  
First Results ◽  
Asian Summer ◽  
Tropopause Temperature ◽  
Stratospheric Water Vapour

Abstract First observations on the vertical structure of diurnal variability of tropospheric water vapour in the lower and middle atmosphere using 13 years of COSMIC and 18 years of SABER observations are presented in this paper. The most significant and new observation is that the middle stratospheric water vapour (SWV) enhancement is observed between 9-18 LT, whereas it is between 6-15 LT near tropopause in all the seasons. The diurnal amplitude of water vapour near tropopause is between 0.3-0.4 ppmv. Bimodal peaks are found in the diurnal amplitude of SWV, maximizing between 25-30 km (~0.4 ppmv) and 45-50 km (~0.6 ppmv). The analysis reveals that the diurnal variability in the lower SWV is controlled by the tropical tropopause temperature, whereas the middle and upper SWV is controlled by methane oxidation. The results are presented and discussed in the light of present understanding.

scholarly journals Is there a solar signal in lower stratospheric water vapour?

2015 ◽  
Vol 15 (17) ◽  
pp. 9851-9863 ◽  
Author(s):  
T. Schieferdecker ◽  
S. Lossow ◽  
G. P. Stiller ◽  
T. von Clarmann
Keyword(s):  
Solar Cycle ◽  
Water Vapour ◽  
Time Lag ◽  
Michelson Interferometer ◽  
Latitude Range ◽  
Tropical Tropopause ◽  
Atmospheric Sounding ◽  
Solar Signal ◽  
Tropopause Temperature ◽  
Stratospheric Water Vapour

Abstract. A merged time series of stratospheric water vapour built from the Halogen Occultation Instrument (HALOE) and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) data between 60° S and 60° N and 15 to 30 km and covering the years 1992 to 2012 was analysed by multivariate linear regression, including an 11-year solar cycle proxy. Lower stratospheric water vapour was found to reveal a phase-shifted anti-correlation with the solar cycle, with lowest water vapour after solar maximum. The phase shift is composed of an inherent constant time lag of about 2 years and a second component following the stratospheric age of air. The amplitudes of the water vapour response are largest close to the tropical tropopause (up to 0.35 ppmv) and decrease with altitude and latitude. Including the solar cycle proxy in the regression results in linear trends of water vapour being negative over the full altitude/latitude range, while without the solar proxy, positive water vapour trends in the lower stratosphere were found. We conclude from these results that a solar signal seems to be generated at the tropical tropopause which is most likely imprinted on the stratospheric water vapour abundances and transported to higher altitudes and latitudes via the Brewer–Dobson circulation. Hence it is concluded that the tropical tropopause temperature at the final dehydration point of air may also be governed to some degree by the solar cycle. The negative water vapour trends obtained when considering the solar cycle impact on water vapour abundances can possibly solve the "water vapour conundrum" of increasing stratospheric water vapour abundances despite constant or even decreasing tropopause temperatures.

scholarly journals A solar signal in lower stratospheric water vapour?

2015 ◽  
Vol 15 (8) ◽  
pp. 12353-12387 ◽  
Author(s):  
T. Schieferdecker ◽  
S. Lossow ◽  
G. P. Stiller ◽  
T. von Clarmann
Keyword(s):  
Solar Cycle ◽  
Water Vapour ◽  
Solar Maximum ◽  
Time Lag ◽  
Latitude Range ◽  
Tropical Tropopause ◽  
Solar Signal ◽  
Tropopause Temperature ◽  
Stratospheric Water Vapour ◽  
Linear Trends

Abstract. A merged time series of stratospheric water vapour built from HALOE and MIPAS data between 60° S and 60° N and 15 to 30 km and covering the years 1992 to 2012 was analyzed by multivariate linear regression including an 11 year solar cycle proxy. Lower stratospheric water vapour was found to reveal a phase-shifted anti-correlation with the solar cycle, with lowest water vapour after solar maximum. The phase shift is composed of an inherent constant time lag of about 2 years and a second component following the stratospheric age of air. The amplitudes of the water vapour response are largest close to the tropical tropopause (up to 0.35 ppmv) and decrease with altitude and latitude. Including the solar cycle proxy in the regression results in linear trends of water vapour being negative over the full altitude/latitude range, while without the solar proxy positive water wapour trends in the lowermost stratosphere were found. We conclude from these results that a solar signal generated at the tropical tropopause is imprinted on the stratospheric water vapour abundances and transported to higher altitudes and latitudes via the Brewer–Dobson circulation. Hence it is concluded that the tropical tropopause temperature at the final dehydration point of air is also governed to some degree by the solar cycle. The negative water vapour trends obtained when considering the solar cycle impact on water vapour abundances can solve the water vapour conundrum of increasing stratospheric water vapour abundances at constant or even decreasing tropopause temperatures.

scholarly journals Trend differences in lower stratospheric water vapour between Boulder and the zonal mean and their role in understanding fundamental observational discrepancies

2018 ◽  
Vol 18 (11) ◽  
pp. 8331-8351 ◽  
Author(s):  
Stefan Lossow ◽  
Dale F. Hurst ◽  
Karen H. Rosenlof ◽  
Gabriele P. Stiller ◽  
Thomas von Clarmann ◽  
...  
Keyword(s):  
Water Vapour ◽  
Satellite Data ◽  
Middle Atmosphere ◽  
Michelson Interferometer ◽  
Lagrangian Model ◽  
Data Set ◽  
Temporal Behaviour ◽  
Model Simulations ◽  
Time Period ◽  
Stratospheric Water Vapour

Abstract. Trend estimates with different signs are reported in the literature for lower stratospheric water vapour considering the time period between the late 1980s and 2010. The NOAA (National Oceanic and Atmospheric Administration) frost point hygrometer (FPH) observations at Boulder (Colorado, 40.0° N, 105.2° W) indicate positive trends (about 0.1 to 0.45 ppmv decade−1). On the contrary, negative trends (approximately −0.2 to −0.1 ppmv decade−1) are derived from a merged zonal mean satellite data set for a latitude band around the Boulder latitude. Overall, the trend differences between the two data sets range from about 0.3 to 0.5 ppmv decade−1, depending on altitude. It has been proposed that a possible explanation for these discrepancies is a different temporal behaviour at Boulder and the zonal mean. In this work we investigate trend differences between Boulder and the zonal mean using primarily simulations from ECHAM/MESSy (European Centre for Medium-Range Weather Forecasts Hamburg/Modular Earth Submodel System) Atmospheric Chemistry (EMAC), WACCM (Whole Atmosphere Community Climate Model), CMAM (Canadian Middle Atmosphere Model) and CLaMS (Chemical Lagrangian Model of the Stratosphere). On shorter timescales we address this aspect also based on satellite observations from UARS/HALOE (Upper Atmosphere Research Satellite/Halogen Occultation Experiment), Envisat/MIPAS (Environmental Satellite/Michelson Interferometer for Passive Atmospheric Sounding) and Aura/MLS (Microwave Limb Sounder). Overall, both the simulations and observations exhibit trend differences between Boulder and the zonal mean. The differences are dependent on altitude and the time period considered. The model simulations indicate only small trend differences between Boulder and the zonal mean for the time period between the late 1980s and 2010. These are clearly not sufficient to explain the discrepancies between the trend estimates derived from the FPH observations and the merged zonal mean satellite data set. Unless the simulations underrepresent variability or the trend differences originate from smaller spatial and temporal scales than resolved by the model simulations, trends at Boulder for this time period should also be quite representative for the zonal mean and even other latitude bands. Trend differences for a decade of data are larger and need to be kept in mind when comparing results for Boulder and the zonal mean on this timescale. Beyond that, we find that the trend estimates for the time period between the late 1980s and 2010 also significantly differ among the simulations. They are larger than those derived from the merged satellite data set and smaller than the trend estimates derived from the FPH observations.

scholarly journals Dehydration and low ozone in the tropopause layer over the Asian monsoon caused by tropical cyclones: Lagrangian transport calculations using ERA-Interim and ERA5 reanalysis data

2020 ◽  
Vol 20 (7) ◽  
pp. 4133-4152 ◽  
Author(s):  
Dan Li ◽  
Bärbel Vogel ◽  
Rolf Müller ◽  
Jianchun Bian ◽  
Gebhard Günther ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Water Vapour ◽  
Tropical Cyclones ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Deep Convection ◽  
Reanalysis Data ◽  
Trajectory Calculations ◽  
Asian Summer ◽  
The Western Pacific

Abstract. Low ozone and high water vapour mixing ratios are common features in the Asian summer monsoon (ASM) anticyclone; however, low ozone and low water vapour values were observed near the tropopause over Kunming, China, within the ASM using balloon-borne measurements performed during the SWOP (sounding water vapour, ozone, and particle) campaign in August 2009 and 2015. Here, we investigate low ozone and water vapour signatures in the upper troposphere and lower stratosphere (UTLS) using FengYun-2D, FengYun-2G, and Aura Microwave Limb Sounder (MLS) satellite measurements and backward trajectory calculations. Trajectories with kinematic and diabatic vertical velocities were calculated using the Chemical Lagrangian Model of the Stratosphere (CLaMS) trajectory module driven by both ERA-Interim and ERA5 reanalysis data. All trajectory calculations show that air parcels with low ozone and low water vapour values in the UTLS over Kunming measured by balloon-borne instruments originate from the western Pacific boundary layer. Deep convection associated with tropical cyclones over the western Pacific transports ozone-poor air from the marine boundary layer to the cold tropopause region. Subsequently, these air parcels are mixed into the strong easterlies on the southern side of the Asian summer monsoon anticyclone. Air parcels are dehydrated when passing the lowest temperature region (< 190 K) at the convective outflow of tropical cyclones. However, trajectory calculations show different vertical transport via deep convection depending on the employed reanalysis data (ERA-Interim, ERA5) and vertical velocities (diabatic, kinematic). Both the kinematic and the diabatic trajectory calculations using ERA5 data show much faster and stronger vertical transport than ERA-Interim primarily because of ERA5's better spatial and temporal resolution, which likely resolves convective events more accurately. Our findings show that the interplay between the ASM anticyclone and tropical cyclones has a significant impact on the chemical composition of the UTLS during summer.

scholarly journals Linking the uncertainty in simulated arctic ozone losses to modelling of tropical stratospheric water vapour

2018 ◽  
Author(s):  
Laura Thölix ◽  
Alexey Karpechko ◽  
Leif Backman ◽  
Rigel Kivi
Keyword(s):  
Water Vapour ◽  
Climate Models ◽  
Polar Vortex ◽  
The Arctic ◽  
Ozone Loss ◽  
Tropical Tropopause ◽  
Water Vapour Concentration ◽  
Vapour Concentration ◽  
The Impact ◽  
Stratospheric Water Vapour

Abstract. Stratospheric water vapor plays a key role in radiative and chemical processes, it e.g. influences the chemical ozone loss via controlling the polar stratospheric cloud formation in the polar stratosphere. The amount of water entering the stratosphere through the tropical tropopause differs substantially between chemistry-climate models. This is because the present-day models have difficulties in capturing the whole complexity of processes that control the water transport across the tropopause. As a result there are large differences in the stratospheric water vapour between the models. In this study we investigate the sensitivity of simulated Arctic ozone loss to the amount of water, which enters the stratosphere through the tropical tropopause. We used a chemical transport model, FinROSE-CTM, forced by ERA-Interim meteorology. The water vapour concentration in the tropical tropopause was varied between 0.5 and 1.6 times the concentration in ERA-Interim, which is similar to the range seen in chemistry climate models. The water vapour changes in the tropical tropopause led to about 1.5 and 2 ppm more water vapour in the Arctic polar vortex compared to the ERA-Interim, respectively. We found that the impact of water vapour changes on ozone loss in the Arctic polar vortex depend on the meteorological conditions. Polar stratospheric clouds form in the cold conditions within the Arctic vortex, and chlorine activation on their surface lead to ozone loss. If the cold conditions persist long enough (e.g. in 2010/11), the chlorine activation is nearly complete. In this case addition of water vapour to the stratosphere increased the formation of ICE clouds, but did not increase the chlorine activation and ozone destruction significantly. In the warm winter 2012/13 the impact of water vapour concentration on ozone loss was small, because the ozone loss was mainly NOx induced. In intermediately cold conditions, e.g. 2013/14, the effect of added water vapour was more prominent than in the other studied winters. The results show that the simulated water vapour concentration in the tropical tropopause has a significant impact on the Arctic ozone loss and deserves attention in order to improve future projections of ozone layer recovery.

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 Sensitivity of stratospheric water vapour to variability in tropical tropopause temperatures and large-scale transport

2020 ◽  
Author(s):  
Jacob W. Smith ◽  
Peter H. Haynes ◽  
Amanda C. Maycock ◽  
Neal Butchart ◽  
Andrew C. Bushell
Keyword(s):  
Seasonal Variation ◽  
Water Vapour ◽  
Temperature Variability ◽  
Interannual Variations ◽  
Trajectory Calculations ◽  
Monthly Temperature ◽  
Tropical Tropopause ◽  
Water Vapour Concentration ◽  
Annual Range ◽  
Stratospheric Water Vapour

Abstract. Concentrations of water vapour entering the tropical lower stratosphere are primarily determined by conditions that air parcels encounter as they are transported through the tropical tropopause layer (TTL). Here we quantify the relative roles of variations in TTL temperatures and transport in determining seasonal and interannual variations of stratospheric water vapour. Following previous studies, we use trajectory calculations with the water vapour concentration set by the Lagrangian Dry Point along trajectories. To isolate the roles of transport and temperatures, the Lagrangian Dry Point calculations are modified by time-shifting temperatures relative to transport, and vice versa, with the shift made by years to investigate interannual variations and by months to investigate seasonal variations. Both ERA-Interim reanalysis data for the 1999–2009 period and data generated by a chemistry-climate model (UM-UKCA) are investigated. Variations in temperatures, rather than transport, dominate interannual variability, typically explaining more than 70 % of variability, including individual events such as the 2000 stratospheric water vapour drop. Similarly seasonal variation of temperatures, rather than transport, is shown to be the dominant driver of the annual cycle in lower stratospheric water vapour concentrations in both model and reanalysis, but it is also shown that seasonal variation of transport plays an important role in reducing the seasonal cycle maximum (reducing the annual range by about 30 %). The quantitative role in dehydration of sub-seasonal and sub-monthly Eulerian temperature variability is also examined by using time-filtered temperature fields in the trajectory calculations. Sub-monthly temperature variability reduces annual mean water vapour concentrations by 40 % in the reanalysis calculation and 30 % in the model calculation. These results indicate that, whilst capturing seasonal and interannual variation of temperature is a major factor in modelling realistic stratospheric water vapour concentrations, simulation of seasonal variation of transport and of sub-seasonal and sub-monthly temperature variability are also important and cannot be ignored.

scholarly journals Impact of typhoons on the composition of the upper troposphere within the Asian summer monsoon anticyclone: the SWOP campaign in Lhasa 2013

2016 ◽  
Author(s):  
Dan Li ◽  
Bärbel Vogel ◽  
Jianchun Bian ◽  
Rolf Müller ◽  
Laura L. Pan ◽  
...  
Keyword(s):  
Water Vapour ◽  
Tropical Cyclones ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Vertical Transport ◽  
Western Pacific ◽  
Lagrangian Model ◽  
Upper Troposphere ◽  
Asian Summer ◽  
The Western Pacific

Abstract. In the frame of the SWOP (sounding water vapour, ozone, and particle) campaign during the Asian summer monsoon (ASM), ozone and water vapour profiles were measured by balloon-borne sensors launched from Lhasa (29.66° N, 91.14° E, elevation 3650 m), China, in August 2013. In total, 24 soundings were launched, nearly half of which show some strong variations in the relationship between ozone and water vapour in the tracer-tracer correlation in the upper troposphere and lower stratosphere (UTLS). 20-day backward trajectories of each sounding were calculated using the trajectory module of the Chemical Lagrangian Model of the Stratosphere (CLaMS) to analyse these variations. The trajectory calculations demonstrate that three tropical cyclones (tropical storm Jebi, typhoons Utor and Trami), which occurred over the Western Pacific Ocean during August 2013, had a considerable impact on the vertical distribution of ozone and water vapour by uplifting marine air masses to altitudes of the ASM anticyclone. Air parcels subsequently arrived at the observation site via two primary pathways: firstly via direct horizontal transport from the location of the typhoon to the station within approximately three days, and secondly via rotational subsidence, during which air parcels descend slowly along a circle following the anticyclone flow within a timescale of one week. Furthermore, the interplay between the spatial position of the ASM anticyclone and tropical cyclones plays a key role in controlling the transport pathways of air parcels from the boundary layer of the Western Pacific to Lhasa in horizontal as well as vertical transport. Moreover, the statistical analysis shows that the strongest impact by typhoons is found at altitudes between 14.5 km and 17 km (365–375 K). Low ozone values (50–80 ppbv) were observed between 370 K and 380 K due to the strong vertical transport within tropical cyclones.

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