scholarly journals Large Uncertainties in Estimation of Tropical Tropopause Temperature Variabilities Due to Model Vertical Resolution

2019 ◽  
Vol 46 (16) ◽  
pp. 10043-10052 ◽  
Author(s):  
Wuke Wang ◽  
Ming Shangguan ◽  
Wenshou Tian ◽  
Torsten Schmidt ◽  
Aijun Ding
Keyword(s):  
Vertical Resolution ◽  
Tropical Tropopause ◽  
Tropopause Temperature

scholarly journals Processes Controlling Tropical Tropopause Temperature and Stratospheric Water Vapor in Climate Models

2015 ◽  
Vol 28 (16) ◽  
pp. 6516-6535 ◽  
Author(s):  
Steven C. Hardiman ◽  
Ian A. Boutle ◽  
Andrew C. Bushell ◽  
Neal Butchart ◽  
Mike J. P. Cullen ◽  
...  
Keyword(s):  
Water Vapor ◽  
Climate Models ◽  
Atmospheric Composition ◽  
Stratospheric Water Vapor ◽  
Vertical Advection ◽  
Radiative Processes ◽  
Microphysical Properties ◽  
Tropical Tropopause ◽  
The Tropics ◽  
Tropopause Temperature

Abstract A warm bias in tropical tropopause temperature is found in the Met Office Unified Model (MetUM), in common with most models from phase 5 of CMIP (CMIP5). Key dynamical, microphysical, and radiative processes influencing the tropical tropopause temperature and lower-stratospheric water vapor concentrations in climate models are investigated using the MetUM. A series of sensitivity experiments are run to separate the effects of vertical advection, ice optical and microphysical properties, convection, cirrus clouds, and atmospheric composition on simulated tropopause temperature and lower-stratospheric water vapor concentrations in the tropics. The numerical accuracy of the vertical advection, determined in the MetUM by the choice of interpolation and conservation schemes used, is found to be particularly important. Microphysical and radiative processes are found to influence stratospheric water vapor both through modifying the tropical tropopause temperature and through modifying upper-tropospheric water vapor concentrations, allowing more water vapor to be advected into the stratosphere. The representation of any of the processes discussed can act to significantly reduce biases in tropical tropopause temperature and stratospheric water vapor in a physical way, thereby improving climate simulations.

scholarly journals Dehydration of the stratosphere

2011 ◽  
Vol 11 (16) ◽  
pp. 8433-8446 ◽  
Author(s):  
M. R. Schoeberl ◽  
A. E. Dessler
Keyword(s):  
Water Vapor ◽  
Gravity Waves ◽  
Small Contribution ◽  
Stratospheric Water Vapor ◽  
Mixing Ratios ◽  
Trajectory Calculations ◽  
Tropical Tropopause ◽  
Type Water ◽  
Dehydration Processes ◽  
Tropopause Temperature

Abstract. Domain filling, forward trajectory calculations are used to examine the global dehydration processes that control stratospheric water vapor. As with most Lagrangian models of this type, water vapor is instantaneously removed from the parcel to keep the relative humidity (RH) with respect to ice from exceeding saturation or a specified super-saturation value. We also test a simple parameterization of stratospheric convective moistening through ice lofting and the effect of gravity waves as a mechanism that can augment dehydration. Comparing diabatic and kinematic trajectories driven by the MERRA reanalysis, we find that, unlike the results from Liu et al. (2010), the additional transport due to the vertical velocity "noise" in the kinematic calculation creates too dry a stratosphere and a too diffuse a water-vapor tape recorder signal compared observations. We also show that the kinematically driven parcels are more likely to encounter the coldest tropopause temperatures than the diabatic trajectories. The diabatic simulations produce stratospheric water vapor mixing ratios close to that observed by Aura's Microwave Limb Sounder and are consistent with the MERRA tropical tropopause temperature biases. Convective moistening, which will increase stratospheric HDO, also increases stratospheric water vapor while the addition of parameterized gravity waves does the opposite. We find that while the Tropical West Pacific is the dominant dehydration location, but dehydration over Tropical South America is also important. Antarctica makes a small contribution to the overall stratospheric water vapor budget as well by releasing very dry air into the Southern Hemisphere stratosphere following the break up of the winter vortex.

scholarly journals Ice injected into the tropopause by deep convection – Part 2: Over the Maritime Continent

2019 ◽  
Author(s):  
Iris-Amata Dion ◽  
Cyrille Dallet ◽  
Philippe Ricaud ◽  
Fabien Carminati ◽  
Peter Haynes ◽  
...  
Keyword(s):  
Deep Convection ◽  
Companion Paper ◽  
Horizontal Resolution ◽  
Horizontal Distribution ◽  
High Temporal Resolution ◽  
Vertical Resolution ◽  
Maritime Continent ◽  
Diurnal Cycles ◽  
Tropical Tropopause ◽  
Study Zone

Abstract. The amount of ice injected up to the tropical tropopause layer has a strong radiative impact on climate. In the tropics, the Maritime Continent (MariCont) region presents the largest injection of ice by deep convection into the upper troposphere (UT) and tropopause level (TL) (from results presented in the companion paper Part 1). This study focuses on the MariCont region and aims to assess the processes, the areas and the diurnal amount and duration of ice injected by deep convection over islands and over seas using a 2° × 2° horizontal resolution during the austral convective season of December, January and February. The model presented in the companion paper is used to estimate the amount of ice injected (∆IWC) up to the TL by combining ice water content (IWC) measured twice a day in tropical UT and TL by the Microwave Limb Sounder (MLS; Version 4.2), from 2004 to 2017, and precipitation (Prec) measurement from the Tropical Rainfall Measurement Mission (TRMM; Version 007) at high temporal resolution (1 hour). The horizontal distribution of ∆IWC estimated from Prec (∆IWCPrec) is presented at 2° × 2° horizontal resolution over the MariCont. ∆IWC is also evaluated by using the number of lightnings (Flash) from the TRMM-LIS instrument (Lightning Imaging Sensor, from 2004 to 2015 at 1-h and 0.25° × 0.25° resolutions). ∆IWCPrec and ∆IWC estimated from Flash (∆IWCFlash) are compared to ∆IWC estimated from the ERA5 reanalyses (∆IWCERA5) degrading the vertical resolution to that of MLS observations (). Our study shows that, while the diurnal cycles of Prec and Flash are consistent to each other in timing and phase over lands and different over offshore and coastal areas of the MariCont, the observational ∆IWC range between ∆IWCPrec and ∆IWCFlash is small (to within 4–20 % over land and to within 6–50 % over ocean) in the UT and TL. The reanalysis ∆IWC range between ∆IWCERA5 and has been also found to be small in the UT (22–32 %) but large in the TL (68–71 %), highlighting the stronger impact of the vertical resolution on the TL than in the UT. Combining observational and reanalysis ∆IWC ranges, the total ∆IWC range is estimated in the UT between 4.17 and 9.97 mg m−3 (20 % of variability per study zone) over land and between 0.35 and 4.37 mg m−3 (30 % of variability per study zone) over sea, and, in the TL, between 0.63 and 3.65 mg m−3 (70 % of variability per study zone) over land and between 0.04 and 0.74 mg m−3 (80 % of variability per study zone) over sea. Finally, from IWCERA5, Prec and Flash, this study highlights (1) ∆IWC over land has been found larger than ∆IWC over sea, and (2) the Java Island is the area of the largest ∆IWC in the UT (7.89–8.72 mg m−3 daily mean).

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 The impact of temperature vertical structure on trajectory modeling of stratospheric water vapor

2015 ◽  
Vol 15 (6) ◽  
pp. 3517-3526 ◽  
Author(s):  
T. Wang ◽  
A. E. Dessler ◽  
M. R. Schoeberl ◽  
W. J. Randel ◽  
J.-E. Kim
Keyword(s):  
Water Vapor ◽  
Vertical Structure ◽  
Vertical Resolution ◽  
Tropical Tropopause Layer ◽  
Stratospheric Water Vapor ◽  
Dry Air ◽  
Tropical Tropopause ◽  
Cold Point ◽  
The Impact ◽  
Modern Era

Abstract. Lagrangian trajectories driven by reanalysis meteorological fields are frequently used to study water vapor (H2O) in the stratosphere, in which the tropical cold-point temperatures regulate the amount of H2O entering the stratosphere. Therefore, the accuracy of temperatures in the tropical tropopause layer (TTL) is of great importance for understanding stratospheric H2O abundances. Currently, most reanalyses, such as the NASA MERRA (Modern Era Retrospective – analysis for Research and Applications), only provide temperatures with ~ 1.2 km vertical resolution in the TTL, which has been argued to miss finer vertical structure in the tropopause and therefore introduce uncertainties in our understanding of stratospheric H2O. In this paper, we quantify this uncertainty by comparing the Lagrangian trajectory prediction of H2O using MERRA temperatures on standard model levels (traj.MER-T) to those using GPS temperatures at finer vertical resolution (traj.GPS-T), and those using adjusted MERRA temperatures with finer vertical structures induced by waves (traj.MER-Twave). It turns out that by using temperatures with finer vertical structure in the tropopause, the trajectory model more realistically simulates the dehydration of air entering the stratosphere. But the effect on H2O abundances is relatively minor: compared with traj.MER-T, traj.GPS-T tends to dry air by ~ 0.1 ppmv, while traj.MER-Twave tends to dry air by 0.2–0.3 ppmv. Despite these differences in absolute values of predicted H2O and vertical dehydration patterns, there is virtually no difference in the interannual variability in different runs. Overall, we find that a tropopause temperature with finer vertical structure has limited impact on predicted stratospheric H2O.

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 Quantifying contributions to the recent temperature variability in the tropical tropopause layer

2015 ◽  
Vol 15 (10) ◽  
pp. 5815-5826 ◽  
Author(s):  
W. Wang ◽  
K. Matthes ◽  
T. Schmidt
Keyword(s):  
Climate Model ◽  
Temperature Response ◽  
Anthropogenic Factors ◽  
Vertical Resolution ◽  
Quasi Biennial Oscillation ◽  
Tropical Tropopause Layer ◽  
The Past ◽  
Tropical Tropopause ◽  
Tropical Ssts ◽  
Stratospheric Aerosols

Abstract. The recently observed variability in the tropical tropopause layer (TTL), which features a warming of 0.9 K over the past decade (2001–2011), is investigated with a number of sensitivity experiments from simulations with NCAR's CESM-WACCM chemistry–climate model. The experiments have been designed to specifically quantify the contributions from natural as well as anthropogenic factors, such as solar variability (Solar), sea surface temperatures (SSTs), the quasi-biennial oscillation (QBO), stratospheric aerosols (Aerosol), greenhouse gases (GHGs) and the dependence on the vertical resolution in the model. The results show that, in the TTL from 2001 through 2011, a cooling in tropical SSTs leads to a weakening of tropical upwelling around the tropical tropopause and hence relative downwelling and adiabatic warming of 0.3 K decade-1; stronger QBO westerlies result in a 0.2 K decade-1 warming; increasing aerosols in the lower stratosphere lead to a 0.2 K decade-1 warming; a prolonged solar minimum contributes about 0.2 K decade-1 to a cooling; and increased GHGs have no significant influence. Considering all the factors mentioned above, we compute a net 0.5 K decade-1 warming, which is less than the observed 0.9 K decade-1 warming over the past decade in the TTL. Two simulations with different vertical resolution show that, with higher vertical resolution, an extra 0.8 K decade-1 warming can be simulated through the last decade compared with results from the "standard" low vertical resolution simulation. Model results indicate that the recent warming in the TTL is partly caused by stratospheric aerosols and mainly due to internal variability, i.e. the QBO and tropical SSTs. The vertical resolution can also strongly influence the TTL temperature response in addition to variability in the QBO and SSTs.

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