Recent evidences of deep convective transport through the tropopause (original) (raw)
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Further evidences of deep convective vertical transport of water vapor through the tropopause
Atmospheric Research, 2009
A few years ago, we identified a deep convective transport mechanism, of water vapor through the tropopause, namely, storm top gravity wave breaking, such that tropospheric water substance can be injected into the lower stratosphere via this pathway. The main evidence presented previously was taken from the lower resolution AVHRR images of the storm anvil top cirrus plumes obtained by polar orbiting satellites. Recent observations have provided further supporting evidence for this important cross-tropopause transport mechanism. There are now many higher resolution satellite images, mainly from MODIS instrument, that show more definitely the existence of these plumes, many of which would probably be unseen by lower resolution images. Furthermore, a thunderstorm movie taken in Denver (USA) area during STEPS2000 field campaign and another thunderstorm movie taken by a building top webcam in Zurich also demonstrate that the jumping cirrus phenomenon, first identified by T. Fujita in 1980s, may be quite common in active thunderstorm cells, quite contrary to previous belief that it is rare. We have used a cloud model to demonstrate that the jumping cirrus is exactly the gravity wave breaking phenomenon that transports water vapor through the tropopause. These additional evidences provide increasing support that deep convection contributes substantially to the troposphere-to-stratosphere transport of water substance. This corroborates well with recent studies of the stratospheric HDO/H 2 O ratio which is much highly than it would be if the transport is via slow ascent. The only explanation that can be used to interpret this observation at present is that water substance is transported through the tropopause via rapid vertical motion, i.e., deep convection.
Cross Tropopause Transport of Water by Mid-Latitude Deep Convective Storms: A Review
Terrestrial, Atmospheric and Oceanic Sciences, 2011
Recent observational and numerical modeling studies of the mechanisms which transport moisture to the stratosphere by deep convective storms at mid-latitudes are reviewed. Observational evidence of the cross-tropopause transport of moisture by thunderstorms includes satellite, aircraft and ground-based data. The primary satellite evidence is taken from both conventional satellite of thunderstorm images and CloudSat vertical cloud cross-section images. The conventional satellite images show cirrus plumes above the anvil tops of some of the convective storms where the anvils are already at the tropopause level. The CloudSat image shows an indication of penetration of cirrus plume into the stratosphere. The aircraft observations consist of earlier observations of the "jumping cirrus" phenomenon reported by Fujita and recent detection of ice particles in the stratospheric air associated with deep convective storms. The ground-based observations are video camera records of the jumping cirrus phenomenon occurring at the top of thunderstorm cells. Numerical model studies of the penetrative deep convective storms were performed utilizing a three-dimensional cloud dynamical model to simulate a typical severe storm which occurred in the US Midwest region on 2 August 1981. Model results indicate two physical mechanisms that cause water to be injected into the stratosphere from the storm: (1) the jumping cirrus mechanism which is caused by the gravity wave breaking at the cloud top, and (2) an instability caused by turbulent mixing in the outer shell of the overshooting dome. Implications of the penetrative convection on global processes and a brief future outlook are discussed.
Deep convective cross-tropopause transport in the tropics and evidence by A-Train satellites
Cross-tropopause transport by deep convective clouds can be an (and perhaps the most) important source of water vapor in the stratosphere. Our previous studies have verified that deep convective cross-tropopause transport does occur rather regularly in midlatitudes. This transport is demonstrated by the presence of cloud top features of above anvil cirrus plumes and jumping cirrus phenomenon that have been observed by aircraft, satellite and ground-based observations. The present paper will demonstrate that the same mechanism occurs in the tropics. Because the tropics typically have weaker wind shear at the tropopause level, previous observation did not show clear evidence of the presence of such cross-tropopause features. But the recent NSAS A-Train satellites, especially CloudSat, CALIPSO and MODIS, provide both horizontal cloud top and vertical cross-sectional views of the cloud structure and making the identification of such features much less unambiguous. In this study, we will...
Atmospheric Research, 2008
Past studies using a variety of satellite instruments have demonstrated the possibility of detecting lower stratospheric water vapor against a cold background of deep convective storm tops. The method is based on the brightness temperature difference (BTD) between the water vapor absorption and infrared window bands, assuming a thermal inversion above the cloud top level. This paper confirms the earlier studies, documenting positive BTD values between the 6.2 μm and 10.8 μm bands in Meteosat Second Generation (MSG) Spinning Enhanced Visible and InfraRed Imager (SEVIRI) imagery above tops of deep convective storms over Europe. The observed positive BTD values for a case from 28 June 2005 are compared to calculations from a radiative transfer model, and possible reasons for their existence are discussed. A localized increase in positive BTD is observed at the later stages of storm evolution, and this increase is likely a signal of water vapor being transported by this particular storm from the troposphere into the lower stratosphere.
Transport of water vapor in the tropical tropopause layer
Geophysical Research Letters, 2002
1] A trajectory model coupled to a simple micro-physical model is used to explore the observed relationship between convection, water vapor and cirrus clouds in the tropical tropopause layer (TTL). Horizontal transport associated with the local Hadley circulation leads to water vapor minima in the winter hemisphere separated from the convective regions and the region of minimum temperatures. These spatial signatures are consistent with observations of water vapor and cirrus in the TTL from the Halogen Occultation Experiment (HALOE). In the simulations, one third of observed ice is formed due to horizontal transport through cold regions. Applied variations in temperature over time scales longer than a few hours, similar to gravity wave induced perturbations, act to lower the simulated water vapor.
Mass and water transport into the tropical stratosphere: A cloud-resolving simulation
Journal of Geophysical Research, 2004
A three-dimensional cloud-resolving model is used to investigate the relative contributions of cumulus clouds and slow, large-scale nonconvective ascent to the transport of mass and moisture into the tropical stratosphere. When run to equilibrium, the simulation reproduces key features of the thermal and cloud structure in the tropical tropopause region, including a sharp cold point with a thin cirrus layer above the level of cumulus outflow. The simulated nonconvective mass flux into the stratosphere is 2 orders of magnitude greater than the cumulus mass flux, and the nonconvective water flux is several times greater than the cumulus water flux. The water content of air entering the stratosphere is controlled by the coldest temperature experienced by the air during its slow nonconvective ascent. Temperature fluctuations associated with convectively generated gravity waves reduce this coldest temperature slightly below that of the large-scale temperature minimum.
Atmospheric Chemistry and Physics Discussions, 2016
High-resolution in situ balloon measurements of water vapour, aerosol, methane and temperature in the upper Tropical Tropopause Layer (TTL) and lower stratosphere are used to evaluate the processes controlling the stratospheric water budget: horizontal transport (inmixing) and hydration by cross-tropopause overshooting updrafts. The obtained in situ evidences of these phenomena are analyzed using satellite observations by Aura MLS (Microwave Limb Sounder) and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) together with trajectory and transport modeling performed using CLaMS (Chemical Lagrangian Model of the Stratosphere) and HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) model. Balloon soundings were conducted during March 2012 in Bauru, Brazil (22.3° S) in the frame of the TRO-Pico campaign for studying the impact of convective overshooting on the stratospheric water budget. The balloon payloads included two stratospheric hygrometers:...
Stratosphere-troposphere exchange in a midlatitude mesoscale convective complex: 1. Observations
Journal of Geophysical Research, 1996
On June 28, 1989, a severe thunderstorm over North Dakota developed into a squall line and then into a mesoscale convective complex (MCC) with overshooting tops as high as ---14 l•n and a cirrus anvil that covered more than 300,000 1,an 2. In this paper we describe the trace gas concentrations prior to, in, and around the storm; paper 2 presents numerical simulations. Observations of 0 3 and 0eq unaffected bv upstream convection for at least 3 days prior to the flights placed the undisturbed tropopaus• bctxveen 10.7 and 11 1,an.
AGU Spring Meeting Abstracts, 2008
Measuring water vapor in the upper troposphere and lower stratosphere is difficult due to the low mixing ratios found there, typically only a few parts per million. Here we examine near-infrared spectra acquired with the Solar Spectral Flux Radiometer (SSFR) during the first science phase of the NASA Airborne Tropical TRopopause EXperiment (ATTREX). From the 1400 and 1900 nm absorption bands we infer water vapor amounts in the tropical tropopause layer and adjacent regions between altitudes of 14 and 18 km. We compare these measurements to solar transmittance spectra produced with the MODerate resolution atmospheric TRANsmission (MODTRAN) radiative transfer model, using in situ water vapor, temperature, and pressure profiles acquired concurrently with the SSFR spectra. Measured and modeled transmittance values agree within 0.002, with some larger differences in the 1900 nm band (up to 0.004). Integrated water vapor amounts along the absorption path lengths of 3 to 6 km varied from 1.26 × 10 −4 to 4.59 × 10 −4 g cm −2. A 0.002 difference in absorptance at 1367 nm results in a 3.35 × 10 −5 g cm −2 change of integrated water vapor amounts; 0.004 absorptance change at 1870 nm results in 5.50 × 10 −5 g cm −2 of water vapor. These are 27 % (1367 nm) and 44 % (1870 nm) differences at the lowest measured value of water vapor (1.26 × 10 −4 g cm −2) and 7 % (1367 nm) and 12 % (1870 nm) differences at the highest measured value of water vapor (4.59 × 10 −4 g cm −2). A potential method for extending this type of measurement from aircraft flight altitude to the top of the atmosphere is discussed.