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<div>Precipitation is any liquid or frozen water that forms in the atmosphere and falls back to the earth. It comes in many forms, like rain, sleet, and snow. Along with evaporation and condensation, precipitation is one of the three major parts of the global water cycle.</div><div></div><div></div><div>Precipitation is always fresh water, even when the water originated from the ocean. This is because sea salt does not evaporate with water. However, in some cases, pollutants in the atmosphere can contaminate water droplets before they fall to the ground. The precipitation that results from this is called acid rain. Acid rain does not harm humans directly, but it can make lakes and streams more acidic. This harms aquatic ecosystems because plants and animals often cannot adapt to the acidity.</div><div></div><div></div><div></div><div></div><div></div><div>precipitation ppt free download</div><div></div><div>Download Zip: https://t.co/dpGpv2FDVw </div><div></div><div></div><div>The Precipitation Frequency Data Server (PFDS) is a point-and-click interface developed to deliver NOAA Atlas 14 precipitation frequency estimates and associated information. Upon clicking a state on the map above or selecting a state name from the drop-down menu, an interactive map of that state will be displayed. From there, a user can identify a location for which precipitation frequency estimates are needed.</div><div></div><div></div><div>When La Ni|#a develops across the tropical central/eastern Pacific Ocean, it can affect areas thousands of miles away, including the United States. The effects are usually strongest in Northern Hemisphere winter. However, no two La Ni|#a winters will have identical precipitation patterns.</div><div></div><div></div><div>The most consistent signal is along the Gulf Coast, where almost all of the strong episodes were associated with greater-than-average precipitation. Other fairly reliable signals for the stronger events include a tendency for below-average precipitation in the Ohio and Tennessee Valleys and above-normal precipitation in southern California and the Southwest. Of course, these impacts are not ensured during every El Ni|#o, not even the strongest ones.</div><div></div><div></div><div>The Global Network of Isotopes in Precipitation (GNIP) is a worldwide isotope monitoring network of hydrogen and oxygen isotopes in precipitation, initiated in 1960 by the International Atomic Energy Agency (IAEA) and the World Meteorological Organization (WMO), and operates in cooperation with numerous partner institutions in Member States.</div><div></div><div></div><div>The analysis of the temporal and spatial variations of environmental isotopes in precipitation (mainly oxygen-18 and deuterium) provides basic data for the use of isotopes in hydrological investigations within the scope of water resources inventory, planning and development.</div><div></div><div></div><div>Annual precipitation has decreased in much of the West, Southwest,and Southeast and increased in most of the Northern and SouthernPlains, Midwest, and Northeast. A national average increase of 4%in annual precipitation since 1901 mostly a result of large increases in the fall season.(Medium confidence)</div><div></div><div></div><div></div><div></div><div></div><div></div><div>The frequency and intensity of heavy precipitation events areprojected to continue to increase over the 21st century (highconfidence). Mesoscale convective systems in the central UnitedStates are expected to continue to increase in number and intensityin the future (medium confidence). There are, however, importantregional and seasonal differences in projected changes in totalprecipitation: the northern United States, including Alaska, isprojected to receive more precipitation in the winter and spring,and parts of the southwestern United States are projected to receiveless precipitation in the winter and spring (medium confidence).</div><div></div><div></div><div>Northern Hemisphere spring snow cover extent, North Americamaximum snow depth, snow water equivalent in the western UnitedStates, and extreme snowfall years in the southern and westernUnited States have all declined, while extreme snowfall years inparts of the northern United States have increased (mediumconfidence). Projections indicate large declines in snowpack inthe western United States and shifts to more precipitation fallingas rain than snow in the cold season in many parts of the centraland eastern United States (high confidence).</div><div></div><div></div><div>Changes in precipitation are one of the most important potentialoutcomes of a warming world because precipitation is integral tothe very nature of society and ecosystems. These systems havedeveloped and adapted to the past envelope of precipitation variations.Any large changes beyond the historical envelope may have profoundsocietal and ecological impacts.</div><div></div><div></div><div>Historical variations in precipitation, as observed from bothinstrumental and proxy records, establish the context around whichfuture projected changes can be interpreted, because it is withinthat context that systems have evolved. Long-term station observationsfrom core climate networks serve as a primary source to establishobserved changes in both means and extremes. Proxy records, whichare used to reconstruct past climate conditions, are varied andinclude sources such as tree ring and ice core data. Projectedchanges are examined using the Coupled Model Intercomparison ProjectPhase 5 (CMIP5) suite of model simulations. They establish thelikelihood of distinct regional and seasonal patterns of change.</div><div></div><div></div><div>Observed changes in the 20-year return value of the seasonal dailyprecipitation totals for the contiguous United States over theperiod 1948 to 2015 using data from the Global Historical ClimatologyNetwork (GHCN) dataset. (Figure source: adapted from Kunkel et al.2013;61 American Meteorological Society. Used with permission.)</div><div></div><div></div><div>Detectability of trends (compared to internal variability) for anumber of precipitation metrics over the continental United Stateshas been examined; however, trends identified for the U.S. regionshave not been clearly attributed to anthropogenic forcing.27,28 One study concludedthat increasing precipitation trends in some north-central U.S.regions and the extreme annual anomalies there in 2013 were at leastpartly attributable to the combination of anthropogenic and naturalforcing.29</div><div></div><div></div><div>There is medium confidence that anthropogenic forcing has contributedto global-scale intensification of heavy precipitation over landregions with sufficient data coverage.30 Global changes in extremeprecipitation have been attributed to anthropogenically forcedclimate change,31,32 including annual maximum 1-day and 5-day accumulated precipitationover Northern Hemisphere land regions and (relevant to this report)over the North American continent.33 Although the UnitedStates was not separately assessed, the parts of North America withsufficient data for analysis included the continental United Statesand parts of southern Canada, Mexico, and Central America. Sincethe covered region was predominantly over the United States, thesedetection/attribution findings are applicable to the continentalUnited States.</div><div></div><div></div><div>Based on current evidence, it is concluded that detectable but notattributable increases in mean precipitation have occurred overparts of the central United States. Formal detection-attributionstudies indicate a human contribution to extreme precipitationincreases over the continental United States, but confidence islow based on those studies alone due to the short observationalperiod, high natural variability, and model uncertainty.</div><div></div><div></div><div>In summary, based on available studies, it is concluded that forthe continental United States there is high confidence in thedetection of extreme precipitation increases, while there is lowconfidence in attributing the extreme precipitation changes purelyto anthropogenic forcing. There is stronger evidence for a humancontribution (medium confidence) when taking into accountprocess-based understanding (increased water vapor in a warmeratmosphere), evidence from weather and climate models, and trendsin other parts of the world.</div><div></div><div></div><div>An event attribution study of the potential influence of anthropogenicclimate change on the extreme 3-day rainfall event associated withflooding in Louisiana in August 201639 finds that such extremerainfall events have become more likely since 1900. Model simulationsof extreme rainfall suggest that anthropogenic forcing has increasedthe odds of such a 3-day extreme precipitation event by 40% or more.</div><div></div><div></div><div>Changes in precipitation in a warmer climate are governed by manyfactors. Although energy constraints can be used to understandglobal changes in precipitation, projecting regional changes ismuch more difficult because of uncertainty in projecting changesin the large-scale circulation that plays an important role in theformation of clouds and precipitation.40 For the contiguous UnitedStates (CONUS), future changes in seasonal average precipitationwill include a mix of increases, decreases, or little change,depending on location and season (Figure 7.5). High-latitude regionsare generally projected to become wetter while the subtropical zoneis projected to become drier. As the CONUS lies between these tworegions, there is significant uncertainty about the sign and magnitudeof future anthropogenic changes to seasonal precipitation in muchof the region, particularly in the middle latitudes of the Nation.However, because the physical mechanisms controlling extremeprecipitation differ from those controlling seasonal averageprecipitation (Section 7.1.4), in particular atmospheric water vaporwill increase with increasing temperatures, confidence is highthat precipitation extremes will increase in frequency and intensityin the future throughout the CONUS.</div><div></div><div> dafc88bca6</div>
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