Evaporation Minus Precipitation Research Articles

Lake levels in the southern Bolivian Altiplano (19°–21°S.) during the Late Glacial based on diatom studies

This study is focused on the endorheic Uyni-Coipasa Basin located in the southern Bolivian Altiplano. Stratigraphical and fossil diatom studies based on a detailed radiocarbon chrnology revealed six phases in water-level changes and paleosalinity variations. At 15,430±80 yr B.P., lacustrine conditions settled in the southern Bolivian Altiplano. A saline lake, characterized by benthic meso-metasaline species, reached ∼+4 m altitude above the present bottom of the basin. After 15,430±80 yr B.P., the level rapidly rose to ∼+27 m, as suggested by a tychoplanktonic mesosaline flora. Between ∼14,500 years and ∼13,000 years, finely lanminated sediments at ∼+32 m contained successively a dominance of epiphytic mesosaline to hypersaline species and tychoplanktonic oligosaline diatoms, indicating weak fluctuations in water-level and salinity. At 13,000 years, strong changes in the diatom flora occurred; epiphytic oligo-hypersaline diatoms were replaced by planktonic meso-polysaline species. They indicate a deep salt lake (the lake reached ∼+100 m). After ∼12,000 years, the lake level abruptly dropped, as suggested by fluviatile sediments with a benthic mesopolysaline diatom flora. The main lake was replaced by shallow saline ponds. A wet pulse occurred at ∼11,400 years, characterized by low water level (∼+7 m) and high salinity. This lacustrine phase remained until 10,400 yr B.P. These data indicate changes in Precipitation minus Evaporation (P-E). Our regional interpretations are based on a comparison with teh available data on the northern (Lake Titicaca) and southern (Lipez are) Bolivian Altiplano and on the northern Chilean Altiplano (Atacama Desert).

Evaluation of the Global Atmospheric Moisture Budget as Seen from Analyses

Abstract For the period 1987 to 1993, quantities central to the global moisture budget from the global analyses of the European Centre for Medium-Range Weather Forecasts (ECMWF), the U.S. National Meteorological Center (NMC), and NASA/Goddard have been computed and compared. The precipitable water is computed and compared with satellite data from the Special Sensor Microwave Imager (SSM/I). Fluxes of moisture and their divergence have been used to estimate the vertically integrated moisture budget and thus evaporation minus precipitation (E − P) as residuals. Results of several test computations show that small biases exist in precipitable water as vertical resolution and methods of computing vertical integrals are changed, but the impact is small on the moisture budget. In the Tropics and subtropics the moisture budget is dominated by the divergence field rather than the moisture amounts, and consequently initialization of the analyses has an impact on the perceived moisture budget. The diurnal cycle is ...

A groundwater model to explain past lake levels at Parkers Prairie, Minnesota, USA

The response of a lake level to a shift in climate depends on characteristics of surficial and groundwater hydrology that are unique to that lake. Determination of the past levels of several lakes, rather than just one, can help provide a more precise determination of past hydrology and climate for a given region. The levels of several closed-basin lakes in the Parkers Prairie sandplain in west-central Minnesota were lowest about 7 ka. A steady-state analytic-element groundwater model was used to quantify the effect of changing regional groundwater recharge (N) on the altitude of the water table surrounding these lakes. Because overland flow on the sandplain is limited, the surficial hydrology of the lakes can be simplified to the net quantity lake evaporation minus precipitation ( E-P) . Both N and E - P were manipulated to force the model water table to coincide with the palaeolake levels. Model results indicate that lake levels at 7 ka can be explained primarily by reducing N to about 50-60 mm yr-1 (40-50% of the modern value), coupled with an E - P of about 100-400 mm yr-1 (100-400% of the modem value).

Evaporation Minus Precipitation and Density Fluxes for the North Atlantic

Abstract Estimates of evaporation (E) over the North Atlantic Ocean by Bunker have been combined with estimates of precipitation (P) by Dorman and Bourke to produce new annual and seasonal maps of E–P and surface density flux. Although uncertainties about precipitation algorithms and exchange coefficients still presist, it is felt that the high spatial resolution of these data set permits an estimate of E–P that is a significant improvement over previous work. The maps of E–P show considerably more detail than earlier maps, including a previously uncharted minimum with a northeast to southwest trend across the subtropical gyre. The two regions of maximal E–P display a close connection with continental air flows off Africal and North America, suggesting that the relative narrowness of the North Atlantic contributes to its status as a net evaporation basin. The zonally integrated E–P values are combined with river runoff estimates to obtain the meridional flux of freshwater, which can be compared with fluxe...

Precipitation Minus Evaporation Data for Lagoon Design and Management in the Central and Southeastern United States

ABSTRACT NATIONAL Weather Service data for precipitation and evaporation were used to determine monthly values for precipitation minus evaporation. Totals for various combinations of monthly values were computed. Probability values were then computed. These data are plotted on maps and presented as a tool to use in designing and managing livestock waste lagoons.