Observations of temperature, winds, and atmospheric trace gases suggest that the transition from troposphere to stratosphere occurs in a layer, rather than at sharp “tropopause.” In tropics, this layer is often called “tropical tropopause layer” (TTL). We present an overview observations TTL discuss radiative, dynamical, chemical processes lead its time‐varying, three‐dimensional structure. synthesis definition with bottom 150 hPa, 355 K, 14 km (pressure, potential altitude) top 70 425 18.5...

Significance We show observational evidence for a stratospheric water vapor feedback—a warmer climate increases vapor, and because is itself greenhouse gas, this leads to further warming. An estimate of its magnitude from model yields value +0.3 W/(m 2 ⋅K), suggesting that feedback plays an important role in our system.

Between 2003 and 2008, the global‐average surface temperature of Earth varied by 0.6°C. We analyze here response tropospheric water vapor to these variations. Height‐resolved measurements specific humidity (q) relative (RH) are obtained from NASA's satellite‐borne Atmospheric Infrared Sounder (AIRS). Over most troposphere, q increased with increasing temperature, although some regions showed opposite response. RH in decreased others, global average remaining nearly constant at altitudes. The...

We present a hypothesis on the dehydration and transfer of air from tropical troposphere into stratosphere. The is based existence thick “tropopause layer,” in which vertical horizontal mixing are both significant. Air rapidly dehydrated upon entering this layer vigorous convective overshoots, then slowly ascends through before fully Dehydration genuine entry stratosphere separate processes that happen much different time scales.

Estimates of Earth's climate sensitivity are uncertain, largely because uncertainty in the long-term cloud feedback. I estimated magnitude feedback response to short-term variations by analyzing top-of-atmosphere radiation budget from March 2000 February 2010. Over this period, had a 0.54 ± 0.74 (2σ) watts per square meter kelvin, meaning that it is likely positive. A small negative possible, but one large enough cancel climate's positive feedbacks not supported these observations. Both...

A model of convective and advective transport across the tropical tropopause is described. In this overshooting turrets inject dehydrated tropospheric air into a "tropopause layer" (TTL) bounded approximately by 50- 150-hPa surfaces, layer similar to "entrainment zone" at top planetary boundary layer. The process occurs only in limited regions. TTL, mixtures ambient undergo buoyancy-driven settling, then slowly loft through TTL eventually enter main stratosphere throughout Tropics. It found...

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In situ observations of H 2 O and HDO in the midlatitude stratosphere are used to evaluate role convection determining stratospheric water budget. The show that vapor overworld (potential temperature > 380 K) is isotopically heavier than expected. Measurements an airmass with anomalously high concentrations isotopic signatures characteristic evaporated ice lofted from troposphere during convective storms. Observed plume enhanced background suggest extratropical can account for a...

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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, vapor is instantaneously removed from parcel keep relative humidity (RH) respect ice exceeding saturation or a specified super-saturation value. We also test simple parameterization convective moistening through lofting and effect gravity waves as mechanism can augment dehydration. Comparing...

Abstract Feedbacks in response to climate variations during the period 2000–10 have been calculated using reanalysis meteorological fields and top-of-atmosphere flux measurements. Over this period, was stabilized by a strongly negative temperature feedback (~−3 W m−2 K−1); were also amplified strong positive water vapor (~+1.2 K−1) smaller albedo cloud feedbacks (~+0.3 +0.5 K−1, respectively). These observations are compared two model ensembles, one dominated internal variability (the...

Abstract We examine variations in water vapor air entering the stratosphere through tropical tropopause layer (TTL) over past three decades satellite data and a trajectory model. Most of variance can be explained by processes that affect TTL: quasi‐biennial oscillation, strength Brewer‐Dobson circulation, temperature troposphere. When these factors act phase, significant are possible. also find volcanic eruptions, which inject aerosol into TTL, amount stratosphere. While there is clear...

Abstract Analyses of Coupled Model Intercomparison Project phase 5 simulations suggest that climate models with more positive cloud feedback in response to interannual fluctuations also have long‐term global warming. Ensemble mean vertical profiles change and surface warming are similar, the ensemble is on both timescales. However, average smaller than feedback, likely due differences pattern two Low cover (LCC) found be well correlated across explains over half covariance between feedback....

Abstract We use our forward domain filling trajectory model to explore the impact of tropical convection on stratospheric water vapor (H 2 O) and tropopause layer cloud fraction (TTLCF). Our results are compared winter 2008/2009 TTLCF derived from Cloud‐Aerosol Lidar with Orthogonal Polarization lower H O observations Microwave Limb Sounder. Convection alters in situ by driving air toward ice saturation relative humidity. If is subsaturated, then hydrates through evaporation ice, but if...

The goal of this investigation is to understand the mechanism behind observed high relative humidity with respect ice (RHi) in tropical region between ~14 km (150 hPa) and tropopause, often referred as tropopause layer (TTL). As shown by satellite, aircraft balloon observations, (>80%) RHi regions are widespread within TTL. Regions highest co-located extensive cirrus. During boreal winter, TTL over Tropical Western Pacific (TWP) a weaker maximum South America Africa. In temperatures coldest...

Abstract On 15 January 2022, the Hunga Tonga‐Hunga Ha'apai (HT) eruption injected SO 2 and water into middle stratosphere. The is rapidly converted to sulfate aerosols. aerosol vapor anomalies have persisted in Southern Hemisphere throughout 2022. anomaly increases net downward IR radiative flux whereas layer reduces direct solar forcing. reduction larger than increased flux. Thus, tropospheric forcing will be negative. changes peak July August diminish thereafter. Scaling observed cooling...

Satellite and in situ water vapor ozone observations near the base of overworld (θ ≈ 380‐K potential temperature) are examined summertime northern midlatitudes, with a focus on how their horizontal variations influenced by deep convection. We show that convection has significant effect budget here, but only small budget. Using simple model, we estimate increases model extratropical at 380 K 40% decreases few percent, relative to what would occur without In data this convective injection...

A satellite‐borne precipitation radar is used to study the penetration of convection bearing large particles altitudes around tropical tropopause, a region now known as tropopause layer (TTL). This overshooting has been identified potentially important in dehydration air entering stratosphere. The global distribution reflectivity tops TTL follows interseasonal and interannual patterns surface rates. amount ∼5% total deep ∼1.5% convective rain. In agreement with previous studies, observations...

We have developed an in situ instrument to measure water vapor on the NASA ER-2 as a prototype for use Perseus remotely piloted aircraft. It utilizes photofragment fluorescence throughout stratosphere and upper middle troposphere (mixing ratios from 2 300 ppmv) with simultaneous absorption measurements (water concentrations ≳5×1014 mol/cc). The flew successfully aircraft during 1993 CEPEX SPADE campaigns. 2σ measurement precision 10 s integration time, limited by variation background...

A recent paper (Paltridge et al., 2009) found that specific humidity in the National Centers for Environmental Prediction/National Center Atmospheric Research (NCEP/NCAR) reanalysis declined between 1973 and 2007, particularly tropical mid upper troposphere, region plays key role water vapor feedback. If borne out, this result suggests potential problems consensus view of a positive Here we consider whether holds other reanalyses what time scale climate fluctuation is associated with...

Abstract To understand the radiative impact of tropical thin cirrus clouds, frequency occurrence and optical depths these clouds have been derived. “Thin” are defined here as being those that not detected by operational Moderate Resolution Imaging Spectroradiometer (MODIS) cloud mask, corresponding to an depth value approximately 0.3 or smaller, but detectable in terms reflectance product based on MODIS 1.375-μm channel. With such a definition, were present more than 40% pixels flagged...

Abstract. The domain-filling, forward trajectory calculation model developed by Schoeberl and Dessler (2011) is extended to the 1979–2010 period. We compare results from NASA's MERRA, NCEP's CFSR, ECMWF's ERAi reanalyses with HALOE, MLS, balloon observations. CFSR based simulation produces a wetter stratosphere than drier MERRA. find that 100 hPa temperatures are cold biased compared Singapore sondes which explains result, grid does not resolve point tropopause, its relatively higher water...