Showing papers on "Water cycle published in 1990"

Remote sensing in hydrology

Abstract: Hydrologic cycle basic principles of remote sensing precipitation snow hydrology evapotranspiration run-off soil moisture groundwater water quality water resources management and monitoring future developments.

A scheme for parameterizing ice cloud water content in general circulation models

Abstract: The optical properties of ice clouds are a primary issue for climate and climate change. Evaluating these optical properties in three-dimensional models for studying climate will require a method to calculate the ice water content of such clouds. A procedure is developed to parameterize ice water content as a function of large-scale meteorological characteristics for use in circulation models in which the ice water content is not calculated by means of a three-dimensional prognostic equation for condensed water. The technique identifies large-scale flows in which ice clouds exist and calculates their ice water content by reconstructing the trajectory associated with cloud formation. As the cloud forms, its ice content changes both by deposition of ice from water vapor and by ice removal by sedimentation. The sedimentation process is found to modify significantly the ice water content expected from deposition alone. Ice water contents predicted by the parameterization are compared with aircraft observations collected in the middle latitudes and the tropics, and show reasonable agreement over four orders-of-magnitude of ice water content. A parameterization for the sublimation of ice crystals settling into ice-subsaturated environments is also presented.

Sublimation and transport of water from the north residual polar cap on Mars

Abstract: The possible role of the north residual cap in the current Martian water cycle was examined using models to assess the ability of the cap to supply water to the atmosphere and the ability of the atmospheric circulation to transport it out of the polar regions to low northern latitudes. Results indicate that rather extreme circumstances would be required for the cap to provide all of the observed increase in atmospheric water, such as a combination of high surface winds, low cap emissivities, or substantial evaporation from dark material. But even if these conditions could be met, the high-latitude circulation is too localized in scale to move much water vapor out of the polar environment. Both the present calculations and the data from the Viking's Mars Atmospheric Water Detection Experiment show that about two thirds of the water appearing in the Martian northern hemisphere during summer must be supplied by other sources. It is suggested that the additional source is water desorbing from the nonpolar regolith.

Hydrology and water quantity control

Abstract: Meteorology and the hydrologic cycle precipitation infiltration and evapotranspiration streamflow measurements hydrographs synthetic hydrographs flow routing probability and statistics for hydrologic processes groundwater hydrology volume/peak discharge management.

Hydrology in Mountainous Regions. I-Hydrological Measurements; The Water Cycle.

Abstract: Keywords: Hydrologie Reference HYDRAM-CONF-1990-001 Record created on 2005-10-11, modified on 2016-08-08

Effects of CO2-induoed climatic changes on soowpack and streamflow

Abstract: Atmospheric concentrations of carbon dioxide (CO2) may double during the next century, causing changes in the Earth's climate. Warming of up to 4°C, slight cooling, and 10% changes in precipitation have been projected. Researchers have studied the possible impacts these changes may have on various aspects of the hydrological cycle, but little emphasis has been placed on snow accumulation and melt. In this study, the effects of climatic change on streamflow from a snowmelt-dominated basin in southwestern Montana, USA, are investigated. The National Weather Service River Forecast System model (NWSRFS) was first calibrated using data for the 1973–1984 period. Daily temperature and precipitation values were then changed, and the model ran again to assess the effects on snowpack and streamflow of some possible climatic changes. Results indicate that streamflow may vary by from −22 to +45% depending on the combination of climatic changes imposed.

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

Abstract: 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; e controls the strength of the hydrological cycle. For fixed µ, two regimes are distinguished. One, associated with small values of e, 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 e 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 e 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.

Remote sensing of surface turbulence heat flux

Abstract: The ocean interacts with the atmosphere through exchanges of momentum, heat and moisture. The differential heating of the atmosphere by the ocean fuels atmospheric circulation which, in turn, drives ocean currents and redistributes the fuel. Short-term climate changes are believed to be strongly influenced by such exchanges. Locally, the ocean absorbs heat in the summer and releases it in the winter; globally, heat accumulated in the tropics is transported poleward by ocean currents. The redistribution of heat reduces the extreme temperature contrasts that otherwise would exist. The heat and moisture fluxes change both the horizontal and the vertical density gradients (baroclinicity and stability) of the atmosphere and the ocean. They, in turn, modify the wind and current shears. The moisture flux connects the energy cycle to the hydrological cycle. In the atmosphere, condensation provides not only the means for precipitation but also much of the diabatic heating. In the ocean, evaporation cools the upper layer and increases the salinity.

Global atmospheric circulation experiments on an Earth with polar and tropical continents

Abstract: Two general circulation models forced by mean annual insolation and having an energy balance ocean have been run on an Earth with polar continents and a tropical continent. Polar continents produce strong meridional temperature gradients and a maximum hydrological cycle. A tropical continent produces the warmest planet and a minimal hydrological cycle. Both models produce more arid continents than exist today.

A new method to determine regional evapotranspiration

Abstract: A method is described whereby the chloride concentration and the ratio of 36Cl to total chloride of a given water body are compared with those of precipitation to determine the fraction of the original precipitation which was lost by evapotranspiration before it reached that water body. This method was applied to 11 water sources in the upper Jordan River basin, and the evapotranspirative loss was generally found to be in the range 40–90%. This method, which is much simpler than the other methods for determining regional evapotranspiration, will enable us to monitor the changes in the hydrological cycle which are expected to result from the greenhouse effect.

Weather Radar Precipitation Data And Their Use In Hydrological Modelling

Abstract: Most variables in the hydrological cycle show large and frequent spatial variations, and often exhibit rapid temporal variations. of particular importance is precipitation, and it is often necessary in many hydrological process studies and applications to monitor precipitation continuously at as many points as possible.

Prospects for operational remote sensing of surface water

Abstract: The major surface storages of liquid water in the land phase of the hydrological cycle comprise channel storage in lakes and rivers including ephemeral streams, overbank storage on floodplains, and soil moisture. Many workers have investigated the capacity, contents and behaviour of these storages using remote sensing techniques. These, despite problems of sampling frequency and spatial resolution, can yield useful information especially in the field of hazard monitoring. Of equal importance, however, is their indirect use for assessing landcover, information on which is commonly required for hydrological modelling.

Historique du concept de cycle de l'eau et des premières mesures hydrologiques en Europe

Abstract: In this paper we present quotations, historical texts and experiments which led to our current hydrological concepts. We distinguish two eras in the history of surface water hydrology: − the age of pragmatism and of speculations, from the first millenium B.C. to the end of the Middle Ages. − the age of the observations, measurements and experiments from the Renaissance (1400-1600) to about 1800. We then describe the first measurements of rain, water velocity, discharge and evaporation, especially the famous DALTON equation for evaporation (1802)

Device for improving water quality of shallow water area

Abstract: The utility model provides a water quality improving apparatus for lakes, pools, and rivers in shallow water areas (for example water depth is three meters) or for the water tank of purified water, comprising a water pumping-out barrel, an intermittent air supply device on the lower end, and a vessel for containing the treating agent of solid objects on the upper part. In the lakes, the water tanks or the rivers, the treating agent of solid objects is diffused by the water pumping-out barrel lift in the flowing process of water cycle, and the amount of oxygen storing is increased in the process of floating solid objects processing.

Water on Mars - Volatile history and resource availability

Abstract: The existence of water on Mars is undisputed today. Measurements of atmospheric water vapor have shown that the abundance varies with location and season in a systematic way which depends on processes of exchange with the polar caps, regolith, and atmosphere. Channels, which give the appearance of having been carved by water or of having had water involved in their formation, appear in various locations on the surface; some were formed by catastrophic outflow of water from beneath the surface, while others form valley networks which give the appearance of having formed over long periods of time primarily early in the planet's history. The north polar residual cap consists of water ice, possibly containing an amount of water equivalent to a global layer several tens of meters thick. Finally, water is observed within the regolith, as adsorbed water or as water of hydration.

Multispectral remote sensing contribution to land surface evaporation

Abstract: The global water cycle is perhaps the most important of all the biogeochemical cycles and evaporation, which is a significant component of the water cycle, is also linked with the energy and carbon cycles. Long-term evaporation over large areas has generally been computed as the difference of precipitation and river runoff. Analysis of short-term evaporation rate and its spatial pattern, however, is extremely complex, and multispectral remotely sensed data could aid in such analysis. Multispectral data considered here are visible and near-infrared reflectances, infrared surface temperature and the 37 GHz brightness temperatures. These observations are found to be not totally independent of each other. A few of their relationships are established and discussed considering physically-based models.