A one-dimensional simulation of the water vapor isotope HDO in the tropical stratosphere (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.
Journal of Geophysical Research, 2003
1] Exchange between the upper tropical troposphere and the lower stratosphere is considered by examining WB57F and ER-2 aircraft observations of water, ozone, wind, and temperature in the potential temperature range 360 < q < 420 K. These processes are examined in part by using the technique of unified scale invariance on the airborne data, as has been done previously for the lower stratospheric polar vortex. Scale invariance is found, on scales from a few hundred meters to the maximum flown, 2700 km (25 great circle degrees). The results apply both to vertical exchange at the tropical tropopause and to isentropic exchange at the subtropical jet stream. All scales participate in the maintenance of the mean state, with substantial contributions from relatively infrequent but intense events in the long tails of the probability distributions. Past data are examined and found to fit this general framework. A unique mapping of tropical tropopause temperature to the total hydrogen content of the middleworld and overworld should not be expected; the head of the ''tape recorder'' is at 50-60 hPa rather than 90-100 hPa. The tropical tropopause is observed at potential temperatures q T greater than the maximum moist static surface values q W , such that q T À q W varies between 10 K in fall and up to 40 K in spring. The meridional gradient of q T is directed from the subtropical jet stream to the inner tropics, with q T declining by approximately 10 K from near 30°N to near 10°N in the vicinity of 95°W. The maintenance of these q T values is discussed. Total water (measured as the sum of vapor and vaporized ice) and ozone, major absorbers of solar radiation and emitters/ absorbers of terrestrial infrared radiation, show scale invariance in the upper tropical troposphere. The implications of this result for the notion of a conservative cascade of energy via fluid dynamics from the largest to the smallest scales are discussed. The scaling exponents H z for total water and ozone in the upper tropical troposphere are not the value, 5/9, expected for a passive scalar, probably indicating the presence of sources and/or sinks operating faster than mixing. Exchange between the upper tropical troposphere and the lower stratosphere studied with aircraft observations,
Geophysical Research Letters, 1996
Stratospheric n]casurcmcnts of }120 and C}14 by the. A[nmphcric Trace Molcctrlc Spectroscopy (&l'MOS) I;ouritv [1 ansform spcclromclcr on the AI'I .AS-3 Shulllc flight in Novcmhcr 1994 have been examined 10 invcs(igatc the altitude and gcogmphic va[ i ability of }120 and the quantity H = (}120 -1 20 14) in the tropics and at n]ict-latitudes (8-49['N) in the norlhcm hcmisphcrc. '1'hc mcasutcmcnts inclicalc an average value of 7.18 ~ 0.43 ppmv for total bydrcsgcn H bctwccn altitudes of abcsul 18 to 35 knl, concsprsndin,g 10 an average water vapor mixing ratio of 3,81 ~ 0.29 ppnw entering the stratosphere. '1'hc 1120 vcr[ical distribution in the tropics cxhitrits a wave-like structure in the 16-25 km altitucle ran:c. suggestive of seasonal variations in the water vapor transported fro]ll
Characteristics of stratosphere-troposphere exchange in a general circulation model
Journal of Geophysical Research, 1994
Air and trace gases are exchanged between the stratosphere and the troposphere on a variety of scales; but general circulation models (GCMs) are tinable to represent the smaller scales. It would be useful to see how a GCM represents stratosphere-troposphere exchange (STE), both to identify possible model deficiencies which would affect other studies and to see how important the smaller-scale physics might be in the atmosphere itself. Our understanding of observed STE depends largely on inferences from tracer distributions. In this study we exanfine mass exchange, water vapor exchange, and the behavior of idealized tracers and parcels to diagnose STE in the National Center for Atmospheric Research GCM, the Community Climate Model (CCM2). The CCM2 correctly represents the seasonality of mass exchange across 100 hPa, but values are uniformly too strong. Water vapor, however, indicates that tropical STE is not well represented in the CCM2; even though mean tropopause temperatures are colder than observed, the lower stratosphere is too moist. Most net mass flux occurs at water vapor mixing ratios of about 4-5 parts per million by volume (ppmv), about 1 ppmv too moist. Vertical resolution has little impact on the nature of tropical STE. In midlatitudes, CCM2 more successfully represents STE, which occurs in developing baroclinic waves and stationary anticyclones. Exchange from troposphere to stratosphere does occur but only influences the lowest few kilometers of the extratropical stratosphere, even for tracers with large vertical gradients. The quest for tropopause-level temperatures "sufficiently cold to explain observed mixing ratios," known as the "cold trap," has guided much research on STE. The very dry lower stratosphere, by inference, sharply limits the location and season of mass transfer from troposphere to stratosphere ]. Thus although annual mean, zonal mean tropical tropopause temperatures are too warm to explain observed lower stratospheric water vapor mixing ratios, the cold trap condition is met at some times and locations. Newell and , in an analysis of tropical radiosonde 100 hPa data, identified northern hemisphere winter and the western Pacific as the most probable time and location for troposphere-stratosphere mass transfer to occur; they termed this the "stratospheric fountain." Robinson and Atticks Schoen [1987] compiled statistics using radiosonde measurements of saturation mixing ratios at 100 hPa and at the profile minimum temperature. The observations occurred in intensive observing periods during the FGGE year (fall 1978 to summer 1979) between 20øS and 20øN. Their results essentially confirmed those of Newell and Gould-Stewart but also indicated the degree of variability on short time and spatial scales and showed that the minimum saturation vapor pressure often occurred well above 100 hPa. in the troposphere the tropical rising motion implied by the Brewer-Dobson circulation does not take the form of slow ascent over a broad area, as this would cause widespread cirrus cloud, which is not observed. Instead, most ascent takes place as convection.
Journal of Geophysical Research, 2001
The seasonal cycle of water vapor in the lower stratosphere is studied based on Halogen Occultation Experiment (HALOE) satellite observations spanning 1991-2000. The seasonal cycle highlights fast, quasi-horizontal transport between tropics and midlatitudes in the lowermost stratosphere (near isentropic levels -380-420 K), in addition to vertical propagation above the equator (the tropical "tape recorder"). The rapid isentropic transport out of the tropics produces a layer of relatively dry air over most of the globe throughout the year, and the seasonal cycle in midlatitudes of both hemispheres (and over the Arctic pole) follows that in the tropics. Additionally, the Northern Hemisphere summer monsoon has a dominant influence on hemispheric-scale constituent transport. Longitudinal structures in tropical water vapor and ozone identify regions of strong coupling to the troposphere; an intriguing result is that the solstice minima in water vapor and ozone are spatial separated from maximum convection and coldest tropical temperatures. Detailed comparisons with tropical aircraft measurements and the long record of balloon data from Boulder, Colorado, demonstrate the overall high quality of HALOE water vapor data. Oltmans, 1983; McCormick et al., 1993; Hintsa et al., 1994; Boering et al., 1995]. The inference from these analyses is that rapid transport occurs between the tropics and midlatitudes in the lower stratosphere; this conclusion is reinforced by observations of radioactive isotopes following tropical bomb explosions [Feely and Spar, 1960; Newell, 1963], volcanic aerosols after tropical eruptions [Trepte et al., 1993], and the seasonal cycle of CO 2 [Boering et al., 1995; Strahan et al., 1998]. This region of fast transport is most evident for altitudes between the tropopause
Spatial and temporal variation of water vapor mixing ratio (WVMR) is examined for its association with the convective activity in upper troposphere and lower stratosphere over tropical region particularly Asian monsoon region (AMR) and Indonesian–Australian West Pacific region (IAWPR) using WVMR obtained from MLS satellite with simultaneous daily mean OLR from NOAA and daily mean wind from NCEP reanalysis. An examination of WVMR at various pressure levels during high water vapor regime (moist Phase) indicates that water vapor (WV) transport, in troposphere, is rather fast up to a level of ~ 147 hPa. Seasonal variation of WVMR over tropical lower stratosphere (TLS) is noted to be closely associated with seasonal northward movement of intertropical convergence zone (ITCZ). Convection activity over AMR appears to be a prominent contributor to the moist phase of WVMR seasonal cycle in TLS. However, other tropical regions may also be contributing to the seasonal variability of WVMR. Low WV (dry) phase of the WVMR seasonal cycle in TLS observed during NH winter and early spring months may be caused by the appearance of extreme cold temperatures (≤ 191 K) close to tropopause heights over IAWPR. Mechanisms that could cause such low temperatures over IAWPR are discussed. Intraseasonal oscillations with period of 30–40 days are observed in WVMR at various pressure levels. At 100 hPa level such oscillations are noted to be closely associated with similar oscillation in OLR and temperature. These observations suggest that variations in OLR (proxy of convection activity) produce such oscillation in WVMR. Present analysis thus report signature of convection in upward transport of WV, seasonal and intraseasonal oscillation in WVMR in upper troposphere and lower stratosphere (UTLS).► A signature of convection in upward transport of water vapor mixing ratio (WV) ► Seasonal variability of WVMR ► Intraseasonal oscillations with period of 30–40 days are observed in WVMR at various pressure levels.
Simulations of Water Vapor in the Upper Troposphere and Lower Stratosphere
1999
Upper troposphere and lower stratosphere (UTLS) water vapor is investigated using a general circulation model, the Community Atmosphere Model 3.0 (CAM3.0). Seasonal variability in UTLS water vapor, temperature and zonal wind, based on model simulation results for the period 1991 -2000, are analyzed. Results are validated against satellite data from the Halogen Occultation Experiment (HALOE) and ERA-40 reanalyzes from ECMWF. The model captures the seasonal cycle in temperature as well as water vapor. The zonal wind deviates from the reanalysis data in the tropics as the model is not able to reproduce the Quasi-Biennial Oscillation (QBO). Outside the tropics, the zonal wind corresponds very well with the ERA-40 zonal wind. The model is able to reproduce the seasonal signal in the tropical stratospheric water vapor; i.e., the Tape Recorder Signal. This indicates a realistic Brewer-Dobson circulation in the model. However, the Tape Recorder signal attenuates too fast compared to the HALOE data, suggesting a too strong horizontal mixing between the tropical stratosphere and mid latitudes. CAM3.0 shows considerable improvements in UTLS temperatures as well as water vapor compared to earlier generations of the NCAR general circulation models.
Simulations of the Interannual Variability of Stratospheric Water Vapor
Journal of the Atmospheric Sciences, 2002
Observations and model results indicate that the quasi-biennial oscillation (QBO) modulation of stratospheric water vapor results from two causes. Dynamical redistribution of water vapor from the QBO-induced mean meridional circulation dominates the observed variability in the middle and upper stratosphere. In the lower stratosphere, the QBO water vapor variability is dominated by a ''tape recorder'' that results from the dehydration signal accompanying the QBO variation of the tropical cold point tropopause. It is suggested that another low frequency tape recorder exists due to ENSO modulations of the tropical tropopause, but insufficiently long observations of stratospheric water vapor exist to identify this in the observations.
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.