<descriptor thcode="2"><thesaurus thcode="2" name="USGS Thesaurus" scope="Topics and methods of scientific study carried out by USGS, with product types, scientific disciplines, geologic time, and types of institutional structure and activities.  Broad and shallow, used to help people find scientific information." creator="U.S. Geological Survey" rights="Public domain" edition="2.0" date="2020-01-09" codetype="number" prefix="topic" uri="https://www2.usgs.gov/science/USGSThesaurus" tblname="term" nonpref="nonpref" relterm="relterm" root_code="1" contact="pschweitzer"><category><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/><term thcode="25" code="29" name="distinct labels" parent="26" scope="Preferred labels (descriptor texts) are distinct within the thesaurus. A concept can be specified either by its unique identifier (code) or by the text of its descriptor."/><term thcode="25" code="16" name="hierarchical" parent="11" scope="Substantive broader-narrower relationships exist among the terms."/><term thcode="25" code="13" name="transitive" parent="12" scope="Narrower terms have an &quot;is a&quot; relationship with their broader terms, and generally can be described as part-of, type-of, or instance-of the broader term."/><term thcode="25" code="21" name="disciplines" parent="2" scope="Broad categories of human inquiry or activity, such as scientific disciplines."/><term thcode="25" code="20" name="methods" parent="2" scope="Actions taken to obtain or analyze information"/><term thcode="25" code="19" name="organizational functions" parent="2" scope="Things that organizations do, typically including various types of programs, projects, and services."/><term thcode="25" code="7" name="temporal" parent="2" scope="Terms indicate periods of time, such as chronostratigraphic units, named historical periods or intervals surrounding known historical events, or seasons."/><term thcode="25" code="5" name="theme" parent="2" scope="Terms indicate domains of human concern, such as scientific discipline, societal problems, or characteristics of earth, space, oceans, and living things."/></category><altlabel><altlabel>USGSThesaurus</altlabel><altlabel>USGSThesaurus</altlabel></altlabel></thesaurus><term thcode="2" code="68" name="atmospheric sciences" parent="291" scope="Studies relating to composition, structure, physics, chemistry, and dynamics of the atmosphere."/><bt><term thcode="2" code="291" name="earth sciences" parent="1019" scope="Broad term for all science related to the study of the earth."/><term thcode="2" code="1019" name="sciences" parent="1" scope="Major educational fields, fields of study, and professional groupings within USGS."/><term thcode="2" code="1" name="Categories" scope="Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."/></bt><nt><term thcode="2" code="170" name="climatology" parent="68" scope="Scientific study of the characteristic weather conditions of geographic areas."/><term thcode="2" code="731" name="meteorology" parent="68" scope="Branch of science dealing with the short-term variations of atmospheric conditions including wind, precipitation, temperature, humidity, cloud cover, and air pressure."/></nt><rt><term thcode="2" code="6" name="acid deposition" parent="66" scope="The process by which emissions, chiefly sulfur and nitrogen compounds, either react with the atmosphere when deposited on earth by precipitation of snow, rain, or fog with a pH of 5.5 or below, or settle out as acidic particles or gases."/><term thcode="2" code="27" name="air temperature" parent="67"/><term thcode="2" code="63" name="atmospheric and climatic processes" parent="101" scope="Phenomena affecting or occurring within the mass of gases that surrounds the earth, including its physics, chemistry, dynamics, and weather conditions."/><term thcode="2" code="64" name="atmospheric circulation" parent="63" scope="Movement of atmospheric gases around the earth."/><term thcode="2" code="65" name="atmospheric composition" parent="67" scope="Components of the mass of gases that surrounds a planet.  The earth's atmosphere consists of nitrogen, oxygen, and small portions of other gases."/><term thcode="2" code="66" name="atmospheric deposition (chemical &amp; particulate)" parent="63" scope="The transfer of substances from the air to the surface of the earth, either in wet form (rain, fog, snow, dew, frost, hail) or in dry form (gases, aerosols, particles)."/><term thcode="2" code="67" name="atmospheric properties" parent="287" scope="Characteristics of the mass of gases surrounding the earth  such as composition, temperature, pressure, and humidity."/><term thcode="2" code="284" name="droughts" parent="63" scope="Extended periods of moisture deficit over a sizeable area sufficient to have an adverse effect on vegetation, animals, or man."/><term thcode="2" code="485" name="effects of climate change" parent="1174" scope="Characteristics and behaviors of organisms and earth systems that are modified as a result of changes in global, regional, or local climate."/><term thcode="2" code="384" name="fires" parent="101" scope="Combustion, marked by flames or intense heat, in natural settings, often ignited by lightning or human activities.  For fires set as part of natural resource management, use 'controlled fires'."/><term thcode="2" code="506" name="greenhouse gases" parent="65" scope="Atmospheric gases, including carbon dioxide, fluorocarbons, methane, nitrous oxide, sulfur hexafluoride, ozone, and water vapor, that trap radiant (infrared) energy keeping the earth's surface warmer than it would otherwise be."/><term thcode="2" code="819" name="ocean temperature" parent="810" scope="Distribution of heat in the oceans, including surface water, thermocline and mode waters, and deep waters.  Includes discussion and measures of both in-situ and potential temperature."/><term thcode="2" code="823" name="ocean-atmosphere interaction" parent="63" scope="Processes, including momentum, heat, gas and other exchanges, which result in profound effects on climate and interactions between the air in the lowest part of the atmosphere and the oceans."/><term thcode="2" code="856" name="ozone layer" parent="65" scope="Upper atmosphere layer composed of ozone, a gas made up of molecules comprised of three oxygen atoms, which helps to shield the earth from ultraviolet rays."/><term thcode="2" code="927" name="precipitation (atmospheric)" parent="63" scope="Any or all forms of water particles that fall from the atmosphere, such as rain, snow, hail and sleet."/></rt></descriptor>