scholarly journals Cirrus and water vapor transport in the tropical tropopause layer: a modeling study

2012 ◽  
Vol 12 (4) ◽  
pp. 10729-10773 ◽  
Author(s):  
T. Dinh ◽  
D. R. Durran ◽  
T. Ackerman
Keyword(s):  
Water Vapor ◽  
Large Scale ◽  
Vertical Direction ◽  
Water Vapor Transport ◽  
Kelvin Wave ◽  
Tropical Tropopause Layer ◽  
Mesoscale Dynamics ◽  
Tropical Tropopause ◽  
Upward Transport ◽  
Microphysical Processes

Abstract. We carry out simulations of tropical-tropopause-layer (TTL) cirrus which are formed and forced by a large-scale equatorial Kelvin wave. We find that, even under the influence of the large-scale wave, the radiatively induced mesoscale dynamics in TTL cirrus actively contributes to transport of water vapor in the vertical direction. In a typical TTL cirrus, the heating that results from absorption of radiation by ice crystals induces a mesoscale circulation. Advection of water vapor by the radiatively induced circulation leads to upward advection of the cloudy air. Upward advection of the cloudy air is equivalent to upward transport of water vapor when the air above the cloud is drier than the cloudy air. On the other hand, ice nucleation and depositional growth, followed by sedimentation and sublimation lead to downward transport of water vapor. The net direction of transport is determined by the relative magnitudes of the upward advection of water vapor and the downward transport associated with microphysical processes.

scholarly journals Cirrus and water vapor transport in the tropical tropopause layer – Part 1: A specific case modeling study

2012 ◽  
Vol 12 (20) ◽  
pp. 9799-9815 ◽  
Author(s):  
T. Dinh ◽  
D. R. Durran ◽  
T. Ackerman
Keyword(s):  
Water Vapor ◽  
Large Scale ◽  
Vertical Direction ◽  
Water Vapor Transport ◽  
Mesoscale Circulation ◽  
Kelvin Wave ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Upward Transport ◽  
Microphysical Processes

Abstract. In a simulation of a tropical-tropopause-layer (TTL) cirrus forced by a large-scale equatorial Kelvin wave, the radiatively induced mesoscale dynamics of the cloud actively contributes to the transport of water vapor in the vertical direction. In a typical TTL cirrus, the heating that results from absorption of radiation by ice crystals induces a mesoscale circulation. Advection of water vapor by the radiatively induced circulation leads to upward advection of the cloudy air. Upward advection of the cloudy air is equivalent to upward transport of water vapor when the air above the cloud is drier than the cloudy air. On the other hand, ice nucleation and depositional growth, followed by sedimentation and sublimation lead to downward transport of water vapor. Under the conditions specific to our simulation, the upward transport of water vapor by the mesoscale circulation dominates the downward transport by microphysical processes. The net result is upward transport of water vapor, which is equivalent to hydration of the lower stratosphere. Sensitivity to model conditions and parameters will be discussed in a follow-up paper.

Hydration of the tropical tropopause layer (TTL) by convective updraft during tropical cyclone ENAWO(2017) and generalization to tropical storms in the southwestern Indian Ocean in summer 2016-2017.

2020 ◽  
Author(s):  
Damien Héron ◽  
Stephanie Evan ◽  
Jerome Brioude ◽  
Joris Pianezze ◽  
Thibault Dauhut ◽  
...  
Keyword(s):  
Water Vapor ◽  
Tropical Cyclone ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
Mesoscale Model ◽  
Cirrus Clouds ◽  
Water Vapor Transport ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Southwestern Indian Ocean

<p>Stratospheric water vapor variations play an important role on the climate. Predictions of changes in stratospheric humidity are uncertain because of gaps in our understanding of physical processes occurring in the TTL, between 14 and 20 km altitude. In particular, climate models have great difficulties in modelling water vapor variations in the TTL due to a poor representation of tropical convection, which largely controls the vertical transport of water vapor to UTLS, among other things.</p><p>One of the scientific objectives of the CONCIRTO<sup>5</sup> program is to better understand the role of marine deep convective systems, and tropical cyclones in particular, on the hydration of TTL in the Southwestern Indian Ocean.  In March 2017, a rapid deepening of the tropical cyclone Enawo occured north-west of Reunion island before to strike and cross Madagascar from north to south. The progressive intensification of the cyclone to the intense tropical cyclone stage makes it an ideal case study to analyze the transport of water vapor and hydrometeors in the TTL according to the intensity phase of the cyclone. </p><p>We will present modelling results on water vapor transport into the TTL in March 4 during ENAWO’s intensification. On March 4, the mesoscale model Meso-NH simulated a large water vapour transport through the TTL, associated with the injection of ice through the tropopause and the observation of cirrus clouds. The model validation is done by comparison with satellite data (CALIPSO, Meteosat-8). We generalize the intrusion modelling during ENAWO intensification by comparing the brightness temperature observed above the tropical cyclones and the tropical tropopause temperature extracted from ECMWF-Analysis during the 2016-2017 cyclonic season. From these studies, we can estimate the number of intrusions during a cyclonic season and the cyclonic intensity associated with the intrusions.</p><p> </p><p><sup>5</sup>Effects of convection and cirrus clouds on the Tropical Tropopause Layer over the Indian Ocean</p>

scholarly journals Extreme Floods in the Eastern Part of Europe: Large-Scale Drivers and Associated Impacts

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1122
Author(s):  
Monica Ionita ◽  
Viorica Nagavciuc
Keyword(s):  
Water Vapor ◽  
Heavy Rainfall ◽  
Large Scale ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Flood Events ◽  
Rainfall Events ◽  
Catchment Areas ◽  
Large Scale Atmospheric Circulation ◽  
Heavy Rainfall Events

The role of the large-scale atmospheric circulation in producing heavy rainfall events and floods in the eastern part of Europe, with a special focus on the Siret and Prut catchment areas (Romania), is analyzed in this study. Moreover, a detailed analysis of the socio-economic impacts of the most extreme flood events (e.g., July 2008, June–July 2010, and June 2020) is given. Analysis of the largest flood events indicates that the flood peaks have been preceded up to 6 days in advance by intrusions of high Potential Vorticity (PV) anomalies toward the southeastern part of Europe, persistent cut-off lows over the analyzed region, and increased water vapor transport over the catchment areas of Siret and Prut Rivers. The vertically integrated water vapor transport prior to the flood peak exceeds 300 kg m−1 s−1, leading to heavy rainfall events. We also show that the implementation of the Flood Management Plan in Romania had positive results during the 2020 flood event compared with the other flood events, when the authorities took several precaution measurements that mitigated in a better way the socio-economic impact and risks of the flood event. The results presented in this study offer new insights regarding the importance of large-scale atmospheric circulation and water vapor transport as drivers of extreme flooding in the eastern part of Europe and could lead to a better flood forecast and flood risk management.

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 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.

Moisture fluxes in the tropics dominated by deep convection up to near tropical tropopause levels

2021 ◽  
Author(s):  
Maximilien Bolot ◽  
Stephan Fueglistaler
Keyword(s):  
Large Scale ◽  
Deep Convection ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
Convective Scale ◽  
Moisture Fluxes ◽  
Global Impacts ◽  
Observational Estimate ◽  
Cold Point ◽  
Open Question

<p>The role played by tropical storms in the tropical tropopause layer (TTL), the transitional layer regulating the flux into the stratosphere of trace gases affecting radiation and the ozone layer, has been a long-standing open question. Progress has been slow because of computational limitations and challenging conditions for measurements and most numerical studies have used simulations over limited domains whose results must be upscaled to the tropical surface to infer global impacts. We compute the first global observational estimate of the convective ice flux at near tropical tropopause levels by using spaceborne lidar measurements from CALIOP. The calculation uses a method to convert from lidar extinction to sedimenting ice flux and uses error propagation to provide margins of uncertainty. We show that, at any given level in the TTL, the sedimenting ice flux exceeds the inflow of vapor computed from ERA5 reanalysis, revealing additional ice transport and allowing to deduce the advective ice flux as a function of altitude. The contribution to this flux of large-scale motions (resolved by ERA5) is computed and the residual is hypothesized to represent the flux of ice on the convective scale. Results show without ambiguity that the upward ice flux in deep convection dominates moisture transport up to close to the level of the cold point tropopause.</p>

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.

Response of Seasonal Simulations of a Regional Climate Model to High-Frequency Variability of Soil Moisture during the Summers of 1988 and 1993

2007 ◽  
Vol 8 (4) ◽  
pp. 738-757 ◽  
Author(s):  
Song Yang ◽  
S-H. Yoo ◽  
R. Yang ◽  
K. E. Mitchell ◽  
H. van den Dool ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Water Vapor ◽  
Diurnal Cycle ◽  
High Frequency ◽  
Large Scale ◽  
Climate Model ◽  
Regional Climate ◽  
Water Vapor Transport ◽  
Diurnal Variability ◽  
High Frequency Variability

Abstract This study employs the NCEP Eta Regional Climate Model to investigate the response of the model’s seasonal simulations of summer precipitation to high-frequency variability of soil moisture. Specifically, it focuses on the response of model precipitation and temperature over the U.S. Midwest and Southeast to imposed changes in the diurnal and synoptic variability of soil moisture in 1988 and 1993. High-frequency variability of soil moisture increases (decreases) precipitation in the 1988 drought (1993 flood) year in the central and southern-tier states, except along the Gulf Coast, but causes smaller changes in precipitation along the northern-tier states. The diurnal variability and synoptic variability of soil moisture produce similar patterns of precipitation change, indicating the importance of the diurnal cycle of land surface process. The increase (decrease) in precipitation is generally accompanied by a decrease (increase) in surface and lower-tropospheric temperatures, and the changes in precipitation and temperature are attributed to both the local effect of evaporation feedback and the remote influence of large-scale water vapor transport. The precipitation increase and temperature decrease in 1988 are accompanied by an increase in local evaporation and, more importantly, by an increase in the large-scale water vapor convergence into the Midwest and Southeast. Analogous but opposite-sign behavior occurs in 1993 (compared to 1988) in changes in precipitation, temperature, soil moisture, evaporation, and large-scale water vapor transport. Results also indicate that, in regions where the model simulates the diurnal cycle of soil moisture reasonably well, including this diurnal cycle in the simulations improves model performance. However, no notable improvement in model precipitation can be found in regions where the model fails to realistically simulate the diurnal variability of soil moisture.

scholarly journals Tropical temperature variability and Kelvin-wave activity in the UTLS from GPS RO measurements

2017 ◽  
Vol 17 (2) ◽  
pp. 793-806 ◽  
Author(s):  
Barbara Scherllin-Pirscher ◽  
William J. Randel ◽  
Joowan Kim
Keyword(s):  
Large Scale ◽  
Deep Convection ◽  
Wave Activity ◽  
Kelvin Waves ◽  
Temperature Variability ◽  
Stationary Waves ◽  
Kelvin Wave ◽  
Quasi Biennial Oscillation ◽  
Tropical Tropopause ◽  
Tropopause Region

Abstract. Tropical temperature variability over 10–30 km and associated Kelvin-wave activity are investigated using GPS radio occultation (RO) data from January 2002 to December 2014. RO data are a powerful tool for quantifying tropical temperature oscillations with short vertical wavelengths due to their high vertical resolution and high accuracy and precision. Gridded temperatures from GPS RO show the strongest variability in the tropical tropopause region (on average 3 K2). Large-scale zonal variability is dominated by transient sub-seasonal waves (2 K2), and about half of sub-seasonal variance is explained by eastward-traveling Kelvin waves with periods of 4 to 30 days (1 K2). Quasi-stationary waves associated with the annual cycle and interannual variability contribute about a third (1 K2) to total resolved zonal variance. Sub-seasonal waves, including Kelvin waves, are highly transient in time. Above 20 km, Kelvin waves are strongly modulated by the quasi-biennial oscillation (QBO) in stratospheric zonal winds, with enhanced wave activity during the westerly shear phase of the QBO. In the tropical tropopause region, however, peaks of Kelvin-wave activity are irregularly distributed in time. Several peaks coincide with maxima of zonal variance in tropospheric deep convection, but other episodes are not evidently related. Further investigations of convective forcing and atmospheric background conditions are needed to better understand variability near the tropopause.

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.

Sign in / Sign up

Export Citation Format

Share Document