Atmospheric Water Vapor Transport Research Articles

Transport of atmospheric water vapor by volcanic eruption columns

Contrary to assumptions often made in the literature, explosive volcanic eruptions are capable of transporting significant amounts of water into the stratosphere. In addition to the magmatic water component, atmospheric water vapor is entrained by the column at lower levels. A theoretical model for the conservation of mass, momentum, and thermal energy of four separate components (dry air, water vapor, liquid condensates, and solid particles) is used to determine the extent of atmospheric water redistribution. We examine the effects of water vapor condensation on dynamical characteristics and ambient water vapor transport. A simple technique is presented for deriving canonical forms for the complex system of ordinary differential equations governing the column components. Solutions of this model are presented that show the influence of different volcanic boundary conditions and a range of ambient water vapor distributions on transport of the buoyant column. We show that the water component (vapor + liquid) of small eruption columns rising through a wet atmosphere is dominated by entrained water, whereas larger columns are dominated by the magmatic water. This is due, in part, to the proportionately smaller entrainment surface area in relation to the control volume for the larger columns. We also show that a maintained column with an initial mass flux of 2.7×108 kg s−1 erupted into a wet atmosphere would inject 96 Mt of water vapor into the stratosphere over 24 hours, comparable to the annual input from methane oxidation or 100 midlatitude thunderstorms. This increase may accelerate the conversion of simultaneously erupted volcanic SO2 into sulfuric acid.

The distribution and transport of atmospheric water vapour over the Arctic Basin

AbstractA comprehensive rawinsonde archive, comprising atmospheric soundings from fixed stations, ships, and the former Soviet Union ‘North Pole’ series of drifting ice stations, is used to examine features of the distribution and transport of Arctic water vapour. Results are based on analysis of climatological, gridded seasonal and monthly fields north of 65°N of precipitable water, vertically integrated vapour fluxes, and profiles of specific humidity, vapour fluxes, temperature, and winds, compiled from objective interpolation of the quality controlled soundings. Emphasis is placed on contrasting conditions for winter and summer, with due attention paid to the potential effects of uncertainties in the rawinsonde humidity data.For zonal means, specific humidity for all seasons typically displays a surface maximum, decreasing poleward at all levels. Precipitable water (surface‐300 hPa), has winter values ranging from 3.8 mm for 65°−70°N and 1.8 mm for 80°–90°N, with annual maxima in July of 18.2 and 12.5 mm, respectively. These zonal means, however, mask large spatial variations; precipitable water for winter, spring, and autumn shows a marked equatorward increase towards the Atlantic side of the Arctic only. Minima are found over north‐east Canada during spring, summer, and autumn.Vapour fluxes tend to peak in the lower troposphere at about 850 hPa in winter, but over a broader layer in summer. During winter, the largest vertically integrated (surface‐300 hPa) zonal and meridional vapour transports are found between Iceland and Scandinavia. The Beaufort Sea and western Canada are the only regions where vertically integrated meridional fluxes are equatorward. During summer, the vertically integrated total flux (zonal plus meridional components) increases sharply over the Beaufort Sea. Equatorward meridional fluxes are again found over western Canada, with strong poleward meridional transports over the Atlantic sector.

Atmospheric rivers and bombs

Filamentary structure is a common feature of atmospheric water vapor transport; the filaments may be termed “atmospheric rivers” because some carry as much water as the Amazon [Newell et al., 1992]. An extratropical cyclone whose central pressure fall averages at least 1 hPa hr−1 for 24 hours is known in meteorology as a “bomb” [Sanders and Gyakum, 1980]. We report here an association between rivers and bombs. When a cyclonic system is penetrated by a river, the cyclonic center moves to be close to the position occupied by the leading edge of the river twelve hours previously and the central pressure falls. If the river then moves away from the cyclone, the central pressure rises. Based on a pilot study of pressure fall and water vapor flux convergence for two winter months, the cause of the explosive deepening appears to be latent heat liberation. This is substantiated by composite maps of seven Atlantic and seven Pacific bombs which show that the flux convergence near the bomb center has a comma cloud signature. The observed association may be useful in forecasting 12‐hour direction of motion and pressure change of rapidly developing cyclonic systems; the incorporation of better moisture data into numerical forecasting models may be the reason for the reported increase of skill in the prediction of bombs in recent years.

Atmospheric water vapor transport and continental hydrology over the Americas

The advective transport of atmospheric water vapor, its role in global hydrology, and the water balance of continental regions are discussed and explored. A data set consisting of 10 years of global wind and humidity observations that has been interpolated onto a regular grid is used to estimate atmospheric water vapor fluxes across the boundaries of selected continental regions. The flux of water vapor from the waters surrounding the Americas is computed and graphically represented as integrated normal flux across meridional and zonal segments. The total flux is decomposed into transport by mean motion and transport by correlated transient anomalies in the wind and humidity fields. Seasonal maps of these observations for the Americas reveal the underlying mechanisms and illustrate the characterizing features of the hydrologic cycle and continental water balance for this large land mass.

A Comparison of Regional Isentropic-Sigma and Sigma Model Simulations of the January 1979 Chicago Blizzard

In an initial effort in regional numerical weather prediction, results from the University of Wisconsin isentropic-sigma (UW theta-sigma) hybrid model and an 'identical' sigma model are compared. The two main objectives are to demonstrate the capability of the UW theta-sigma model for regional numerical weather prediction and to identify advantages of the hybrid model in simulating atmospheric water vapor transport and precipitation relative to the sigma model. The 72-h simulations produced by the two models extend over a region covering the western Pacific Ocean, North America, and the western Atlantic Ocean. The simulations begin at 0000 UTC 13 January 1979, a period during which an intense Chicago blizzard develops over the central United States. This period also includes the rapid development of a cyclone in the western Pacific Ocean. Results using the Global Weather Experiment (GWE) ECMWF level IIIB data as initial and verification data indicate that both models produce reasonable and similar 72-h simulations, with the UW theta-sigma model mass and momentum distributions being slightly more accurate than the sigma model. Of particular importance for the Chicago blizzard is that the UW theta-sigma model more accurately simulates water vapor transport northward from the Gulf of Mexico and westward from the Atlantic Ocean. As a result, the hybrid model more accurately simulates observed precipitation, especially over the northeastern U.S. and southeastern Canada.

A bimodal climate response controlled by water vapor transport in a coupled ocean‐atmosphere box model

The importance of the hydrological cycle as a controlling factor on the magnitude of the thermohaline circulation is illustrated in a simple one‐hemisphere coupled ocean‐atmosphere box model. The ocean model includes differential surface heating and evaporation, horizontal and vertical exchange of heat and salt between boxes, and a simply parameterized thermohaline circulation. Surface heat fluxes and evaporation are determined through the coupled ocean and energy balance atmosphere models which treat fluxes of long‐ and short‐wave radiation and sensible and latent heat. Two parameters represent the most important physics: µ controls the magnitude of the thermohaline circulation; ε controls the strength of the hydrological cycle. For fixed µ, two regimes are distinguished. One, associated with small values of ε, has weak latitudinal water vapor transport in the atmosphere, a strong thermohaline circulation with sinking in high latitudes, upwelling in low latitudes, and strong latitudinal transport of heat by the ocean. The second regime for larger ε is characterized by strong latitudinal water vapor transport which, by reducing the surface salinity in high latitudes, shuts down the thermohaline circulation and has reduced ocean and net latitudinal heat transport. The bimodal response in the model is shown to be the consequence of a shift in the mechanism of supply of salt to the high‐latitude surface ocean from predominantly thermohaline transport, a nonlinear process, to or from predominantly eddy mixing transport, a linear process. In climatological terms, the bimodality represents two distinct climate regimes, one with an active ocean meridional circulation and relatively warm ocean and atmosphere temperatures in high latitudes, and the other with a less active ocean circulation and an increased latitudinal temperature gradient in atmosphere and ocean. The regime with an active thermohaline circulation tends to be less stable than the other, exhibiting over a range of ε a “halocline catastrophe” to perturbations in surface salinity. In many respects the model supports current concepts concerning the role of bimodal ocean physics and atmospheric water vapor transport in glacial to interglacial climate changes and in the more rapid events such as the Younger Dryas.

Circulation atmosphérique et sécheresse

Droughts are caused by an extended deficit of precipitations associated with anomalies in the general circulation of the atmosphere. An examination of the hydric balance of our planet shows indeed the essential role played by the general circulation of the atmosphere in the transport of atmospheric water vapour. The atmospheric circulation, which is subject to natural fluctuations of dynamical origin, can furthermore be influenced by the variations of its surface boundary conditions, like ocean surface temperatures, soil albedo and roughness. Persistent anomalies of these parameters can produce displacements of the precipitation zones, leading to droughts in some areas.

Global Water Vapor Flux and Maintenance during FGGE

Abstract The relative humidity, temperature and wind fields generated by the First Global GARP Experiment (FGGE) III-b analysis of the Geophysical Fluid Dynamics Laboratory (GFDL) are used to examine the global precipitable water distribution, and the water vapor transport and maintenance for two extreme seasons of atmospheric circulation, i.e., December–February and June–August 1979. It has been observed that the major water vapor content exists in tropical areas, especially over three regions: equatorial Africa, the northern part of South America, and equatorial western Pacific in December-February; equatorial Africa, Central America and the northern part of South America, and monsoon areas in June-August. The water vapor transport was analyzed to explore how the high water vapor content of these areas is maintained by the large-scale atmospheric circulation. It is concluded that 1) the nondivergent stationary mode describes most of the atmospheric water vapor transport; 2) the stationary divergent mode...

A Global Oxygen Isotope Model – Semi-Empirical, Zonally Averaged

A simple model, which is zonally averaged, for the transport of atmospheric water vapour is presented which uses as input the zonally averaged evaporation field and the mean meridional travel distance of tropospheric water vapour as functions of latitude. The model demonstrates that for polar regions each of the 10° latitude strips poleward of 25° is of equal importance as a moisture source. The model is used to predict zonal averages of δ(18O) for the present day and 18 ka BP. Both annual average values and seasonal amplitudes are presented and compared to observations. Sea-ice cover is an important factor in determining both annual averages and seasonal amplitudes today and at 18 ka BP. An earlier model (Jouzel and others 1983) linking δ(18O), the deuterium excess, and sea-salt content in an Antarctic ice core to the relative humidity of the source region is based on a single-source atmospheric water-vapour cycle type model and is re-evaluated using the present model.

A Global Oxygen Isotope Model – Semi-Empirical, Zonally Averaged

A simple model, which is zonally averaged, for the transport of atmospheric water vapour is presented which uses as input the zonally averaged evaporation field and the mean meridional travel distance of tropospheric water vapour as functions of latitude. The model demonstrates that for polar regions each of the 10° latitude strips poleward of 25° is of equal importance as a moisture source. The model is used to predict zonal averages of δ(18O) for the present day and 18 ka BP. Both annual average values and seasonal amplitudes are presented and compared to observations. Sea-ice cover is an important factor in determining both annual averages and seasonal amplitudes today and at 18 ka BP. An earlier model (Jouzel and others 1983) linking δ(18O), the deuterium excess, and sea-salt content in an Antarctic ice core to the relative humidity of the source region is based on a single-source atmospheric water-vapour cycle type model and is re-evaluated using the present model.

Deuterium and Oxygen 18 in Water Vapour and Precipitation: Application to Atmospheric Water Vapour Transport and to Paleoclimate

Spatial and temporal variations of δD and δ18O in mean monthly precipitation and groundwater are described by means of a simple water vapour advection model, which links the isotope data to the vertically integrated horizontal flow of vapour. This model yields a temperature dependence of the isotope precipitation data, which is compared with the experimental temperature effect. Short-term variations of δD and δ18O in mean daily water vapour reflect the varying influence of different air masses on the local weather. A spectral analysis of these short-term variations yields predominant periodicities of about 10, 20 and 30 days, which are related to the long-wave pattern of the zonal drift in the upper troposphere. δD and δ18O in plant material (tree rings, peat), solids, lake sediments, speleothems and in other carbonates of paleoclimatic interest is primarily influenced by the isotopic composition of local precipitation, atmospheric moisture and by temperature dependent isotope fractionation. The relevance...

Seasonal Variations in the Vertically Integrated Water Vapor Transport Fields over the Southern Hemisphere

Abstract Seasonal mean fields of precipitable water and the zonal and meridional components of the vertically integrated atmospheric water vapor transport fields are calculated from five years of Southern Hemisphere data (1 September 1973 through 31 August 1978). Data are the product of a numerical analysis procedure developed and implemented by Australian Numerical Meteorological Research Centre and are in the form of 47 × 47 matrices superimposed on a polar stereographic projection. Values of the mixing ratio and the u and v components of the wind are available at four levels between 1000 and 500 mb. Primary emphasis is directed toward examining the seasonal variations in the moisture transport fields. Large seasonal differences in precipitable water and in the zonal and meridional fluxes are found, most notably between summer and winter. Summer season, subtropical meridional water vapor fluxes exceed those in winter by a factor of 2. A seasonal asymmetry is noted in the fields of W and Qλ in which th...

Variability in the Annual Fields of Large-Scale Atmospheric Water Vapor Transport

Abstract Annual mean holds of the zonal and meridional components of the vertically integrated water vapor flux in the atmosphere have been computed objectively from six years of Northern Hemispheric upper air data. Emphasis is placed on the longitudinal structure of these fields in order to identify regional contributions to the annual variations of the zonally averaged moisture fluxes. These temporal changes, particularly those associated with the meridional transport of latent heat. appear large enough to impact significantly on the maintenance of the atmospheric energy balance. While the distribution and quality of some upper air data make it difficult to estimate the degree to which the analyses precisely duplicate atmospheric behavior everywhere, this study provides documentation of a wide range of interannual variability. In this regard, the behavior of one of the years chosen for study contrasts sharply with that of the rest of the sample, as was similarly noted for other quantities evaluated by R...

Correlation Analysis of Hydrometeorological Data

Mean monthly time series of precipitation, runoff, atmospheric water vapor transport, terrestrial storage, and evapotranspiration for watersheds distributed over the entire continental United States were analyzed by harmonic analysis to compute Fourier coefficients (with first four harmonics) and explained variances. In addition, linear cross-correlation coefficients for 10 combinations of the five time series are computed. The observed spatial variation of these parameters should be useful to those faced with the formulation of statistical models for simulation and prediction applications.

The role of eddies in atmospheric water vapour transport

It is demonstrated by applying a theory developed by Starr that the mean meridional circulations cannot transport atmospheric water vapour across surfaces of constant mean values of water vapour mixing ratio, and that the work of transferring the moisture from zonal regions of surplus to those of deficit must therefore be accomplished by eddy components of motion.

The role of eddies in atmospheric water vapour transport

AbstractIt is demonstrated by applying a theory developed by Starr that the mean meridional circulations cannot transport atmospheric water vapour across surfaces of constant mean values of water vapour mixing ratio, and that the work of transferring the moisture from zonal regions of surplus to those of deficit must therefore be accomplished by eddy components of motion.