Land surface topography map, Jo Daviess County, Illinois

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Evapotranspiration and runoff from large land areas: Land surface hydrology for atmospheric general circulation models

A land surface hydrology parameterization for use in atmospheric GCM's is presented. The parameterization incorporates subgrid scale variability in topography, soils, soil moisture and precipitation. The framework of the model is the statistical distribution of a topography-soils index, which controls the local water balance fluxes, and is therefore taken to represent the large land area. Spatially variable water balance fluxes are integrated with respect to the topography-soils index to yield our large topography-soils distribution, and interval responses are weighted by the probability of occurrence of the interval. Grid square averaged land surface fluxes result. The model functions independently as a macroscale water balance model. Runoff ratio and evapotranspiration efficiency parameterizations are derived and are shown to depend on the spatial variability of the above mentioned properties and processes, as well as the dynamics of land surface-atmosphere interactions

A global low order spectral model designed for climate sensitivity studies

A two level, global, spectral model using pressure as a vertical coordinate is developed. The system of equations describing the model is nonlinear and quasi-geostrophic. A moisture budget is calculated in the lower layer only with moist convective adjustment between the two layers. The mechanical forcing of topography is introduced as a lower boundary vertical velocity. Solar forcing is specified assuming a daily mean zenith angle. On land and sea ice surfaces a steady state thermal energy equation is solved to calculate the surface temperature. Over the oceans the sea surface temperatures are prescribed from the climatological average of January. The model is integrated to simulate the January climate

An initial intercomparison of atmospheric and oceanic climatology for the ICE-5G and ICE-4G models of LGM paleotopography

This paper investigates the impact of the new ICE-5G paleotopography dataset for Last Glacial Maximum (LGM) conditions on a coupled model simulation of the thermal and dynamical state of the glacial atmosphere and on both land surface and sea surface conditions. The study is based upon coupled climate simulations performed with the ocean–atmosphere–sea ice model of intermediate-complexity Climate de Bilt-coupled large-scale ice–ocean (ECBilt-Clio) model. Four simulations focusing on the Last Glacial Maximum [21 000 calendar years before present (BP)] have been analyzed: a first simulation (LGM-4G) that employed the original ICE-4G ice sheet topography and albedo, and a second simulation (LGM-5G) that employed the newly constructed ice sheet topography, denoted ICE-5G, and its respective albedo. Intercomparison of the results obtained in these experiments demonstrates that the LGM-5G simulation delivers significantly enhanced cooling over Canada compared to the LGM-4G simulation whereas positive temperature anomalies are simulated over southern North America and the northern Atlantic. Moreover, introduction of the ICE-5G topography is shown to lead to a deceleration of the subtropical westerlies and to the development of an intensified ridge over North America, which has a profound effect upon the hydrological cycle. Additionally, two flat ice sheet experiments were carried out to investigate the impact of the ice sheet albedo on global climate. By comparing these experiments with the full LGM simulations, it becomes evident that the climate anomalies between LGM-5G and LGM-4G are mainly driven by changes of the earth’s topography

SCS Natinoal Engineering Handbook: Section 15, Irrigation, Chapter 12--Land Leveling

Land leveling or land grading for irrigation is modifying the surface relief of a field to a planned grade to provide a more suitable surface for efficiently applying irrigation water. Normally land leveling requires moving a lot of earth over several hundred feet. This should not be confused with land planning, land smoothing, or land floating. They are usually accomplished with special equipment to eliminate minor irregularities, and they do not change the general topography of the land surface. Rough grading is removing knolls, mounds, or ridges and filling pockets or swales in a field that is not to have a planned grade. Often no construction stake. are set and reliance is placed on the eye of the equipment operator to obtain the desired field surface. Rough grading is seldom adequate for lands to be surface irrigated

Links between topography, wind, deflation, lakes and dust: The case of the Bodélé Depression, Chad

The Bodélé Depression, Chad is the planet's largest single source of dust. Deflation from the Bodélé could be seen as a simple coincidence of two key prerequisites: strong surface winds and a large source of suitable sediment. But here we hypothesise that long term links between topography, winds, deflation and dust ensure the maintenance of the dust source such that these two apparently coincidental key ingredients are connected by land-atmosphere processes with topography acting as the overall controlling agent. We use a variety of observational and numerical techniques, including a regional climate model, to show that: 1) contemporary deflation from the Bodélé is delineated by topography and a surface wind stress maximum; 2) the Tibesti and Ennedi mountains play a key role in the generation of the erosive winds in the form of the Bodélé Low Level Jet (LLJ); 3) enhanced deflation from a stronger Bodélé LLJ during drier phases, for example, the Last Glacial Maximum, was probably sufficient to create the shallow lake in which diatoms lived during wetter phases, such as the Holocene pluvial. Winds may therefore have helped to create the depression in which erodible diatom material accumulated. Instead of a simple coincidence of nature, dust from the world's largest source may result from the operation of long term processes on paleo timescales which have led to ideal conditions for dust generation in the world's largest dust source. Similar processes plausibly operate in other dust hotspots in topographic depressions

Seasonality of MODIS LST over Southern Italy and correlation with land cover, topography and solar radiation

AbstractLand Surface Temperature (LST) is a key variable in the interactions and energy fluxes between the Earth surface and the atmosphere. Satellite data provide consistent, continuous and spatially distributed information on the Earth's surface conditions among which LST. Ten years of NASA-MODIS day-time and night-time 1 km LST data over Southern Italy have been analyzed to quantify the influence of factors such as topography and the land cover on LST spatio-temporal variations. Results show that topography significantly influence LST variability as a function of the land cover and to a different extent for day-time and night-time data. Moreover, the relation between LST and the influential factors varies with the season during the year. This study contributes to a further understanding of the complex relationship between the spatio-temporal variability of the surface thermal conditions and its driving factors highlighting how these relationships might change within the year

Response of corn yields in a Planosol soil to surface drainage, cropping system and variable fertilizer treatments

The Edina soil series of southeastern Iowa and northern Missouri are areas of relatively flat topography and poor internal drainage. For these areas, where the topography and soils permit, surface drainage is the most practical method of removing excess water from the land. One method of surface drainage that has been used on the Edina soils is bedding, in which the field is divided into narrow-width plow lands with the deadfurrows running parallel to the prevailing land slope. Little is known about the relative returns from investment in a bedding system in comparison with other surface or subsurface drainage methods. Bedding requires that some topsoil be moved to obtain the desired grade for drainage. The effect on crop yields of topsoil removal and movement in land-forming operations such as bedding, however, is not quantitatively understood. It is the general purpose of this bulletin to present and analyze 6 years of corn-yield data involving drainage (bedded versus level), cropping and fertilizer variables from a study on the Southern Iowa Experimental Farm near Bloomfield

Pengaruh Kemiringan Lahan dan Mucuna Bracteata terhadap Aliran Permukaan dan Erosi di PT Perkebunan Nusantara V Kebun Lubuk Dalam

One of the problems that became a threat to the sustainability of the ecosystem and the balance of the farm is land degradation caused by soil erosion due to rains. Elevation and topography that concerns with the land slope also gives effect to the surface run off rate and erosion. The use of Mucuna bracteata became one of efforts to address land degradation due to surface run off and soil erosion. This research uses Split Plot Design where the land slope as the main plots and the use of Mucuna bracteata swath as sub plots. The main plots consists of 3 levels namely land slope 0 - 8%, land slope 8 - 15% and land slope 15 - 25%, whereas the sub plots consists of 2 levels, namely the use of Mucuna bracteata and without the use of Mucuna bracteata. Research results show that the land slope and the use of Mucuna bracteata effects surface run off and erosion. Significantly the existence interaction between the land slope with the use of Mucuna bracteata. The positive correlation between the intensity of rain with surface run off, and surface run off with erosion