<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>1405-3195</journal-id>
<journal-title><![CDATA[Agrociencia]]></journal-title>
<abbrev-journal-title><![CDATA[Agrociencia]]></abbrev-journal-title>
<issn>1405-3195</issn>
<publisher>
<publisher-name><![CDATA[Colegio de Postgraduados]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S1405-31952007000300253</article-id>
<title-group>
<article-title xml:lang="es"><![CDATA[Caracterización de la sequía a diversas escalas de tiempo en Chihuahua, México]]></article-title>
<article-title xml:lang="en"><![CDATA[Characterization of drought at different time scales in Chihuahua, México]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Núñez-López]]></surname>
<given-names><![CDATA[Daniel]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Muñoz-Robles]]></surname>
<given-names><![CDATA[Carlos A.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Reyes-Gómez]]></surname>
<given-names><![CDATA[Víctor M.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Velasco-Velasco]]></surname>
<given-names><![CDATA[Israel]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Gadsden-Esparza]]></surname>
<given-names><![CDATA[Héctor]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Instituto de Ecología A.C. Centro de Investigación sobre Sequía ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>Mexico</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,Instituto Mexicano de Tecnología del Agua  ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>Mexico</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>05</month>
<year>2007</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>05</month>
<year>2007</year>
</pub-date>
<volume>41</volume>
<numero>3</numero>
<fpage>253</fpage>
<lpage>262</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S1405-31952007000300253&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S1405-31952007000300253&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S1405-31952007000300253&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="es"><p><![CDATA[Resumen En este documento se analizaron las principales características de los eventos de sequía ocurridos en las regiones climáticas más representativas del Estado de Chihuahua. La evaluación de la sequía se basó en el cálculo del Índice de Precipitación Estandarizado (Standardized Precipitation Index SPI) en escalas de tiempo de tres, seis y doce meses: SPI-3, SPI-6 y SPI-12. Para cada región climática y escala de tiempo se obtuvo la frecuencia, duración e intensidad de los eventos de sequía de 1970 a 2004. Predominaron condiciones de sequía entre 23 y 31% del tiempo analizado en las tres escalas de tiempo, en diferentes periodos en cada región climática. Los eventos de sequía identificados en series históricas del SPI-3 tuvieron gran frecuencia y corta duración, en tanto que en series de seis y doce meses fueron menos recurrentes pero más prolongados. Los eventos de sequía más destacados por su intensidad y duración ocurrieron a mediados y finales de la década de 1990, con efectos negativos en la actividad agrícola, en la incidencia de incendios forestales y en el almacenamiento de los embalses más importantes del Estado.]]></p></abstract>
<abstract abstract-type="short" xml:lang="en"><p><![CDATA[Abstract In this paper analyzes the principal characteristics of droughts that occur in the most representative climatic regions of the state of Chihuahua are analyzed. Assessment of drought was based on the calculation of the Standardized Precipitation Index (SPI) at time scales of three, six and twelve months: SPI-3, SPI-6 and SPI-12. Frequency, duration and intensity of drought events between 1970 and 2004 were obtained for each climatic region and time scale. Drought conditions predominated during 23 to 31% of the time analyzed at the three time scales in different periods in each climatic region. The drought events identified in historical series of SPE-3 were of high frequency and short duration, while in the series of six and twelve months they were less recurrent, but longer. The most outstanding drought events for their intensity and duration occurred from mid-to late 1990, when agriculture, incidence of forest fires, and the State&#8217;s most important water reservoirs were negatively affected.]]></p></abstract>
<kwd-group>
<kwd lng="es"><![CDATA[eventos de sequía]]></kwd>
<kwd lng="es"><![CDATA[SPI]]></kwd>
<kwd lng="es"><![CDATA[déficit de precipitación]]></kwd>
<kwd lng="es"><![CDATA[escasez de agua]]></kwd>
<kwd lng="en"><![CDATA[Drought]]></kwd>
<kwd lng="en"><![CDATA[SPI]]></kwd>
<kwd lng="en"><![CDATA[precipitation deficit]]></kwd>
<kwd lng="en"><![CDATA[water scarcity]]></kwd>
</kwd-group>
</article-meta>
</front><back>
<ref-list>
<ref id="B1">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Byun]]></surname>
<given-names><![CDATA[H.]]></given-names>
</name>
<name>
<surname><![CDATA[Wilhite]]></surname>
<given-names><![CDATA[D.A.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[Objective quantification of drought severity and duration]]></article-title>
<source><![CDATA[J. Climate]]></source>
<year>1999</year>
<volume>12</volume>
<page-range>2747-56</page-range></nlm-citation>
</ref>
<ref id="B2">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Chang]]></surname>
<given-names><![CDATA[T. J.]]></given-names>
</name>
<name>
<surname><![CDATA[Kleopa]]></surname>
<given-names><![CDATA[X. A.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[A proposed method for drought monitoring]]></article-title>
<source><![CDATA[Water Res. Bull.]]></source>
<year>1991</year>
<volume>27</volume>
<numero>2</numero>
<issue>2</issue>
<page-range>275-81</page-range></nlm-citation>
</ref>
<ref id="B3">
<nlm-citation citation-type="">
<collab>CNA (Comisión Nacional del Agua)</collab>
<source><![CDATA[Programa Hidráulico de Gran Visión del Estado de Chihuahua 1996-2020]]></source>
<year>1996</year>
<edition>1</edition>
<page-range>482</page-range><publisher-loc><![CDATA[Chihuahua, México ]]></publisher-loc>
</nlm-citation>
</ref>
<ref id="B4">
<nlm-citation citation-type="">
<collab>CNA (Comisión Nacional del Agua)</collab>
<source><![CDATA[Estadísticas del Agua en México]]></source>
<year>2003</year>
<edition>1</edition>
<page-range>106</page-range><publisher-loc><![CDATA[México, D.F. ]]></publisher-loc>
</nlm-citation>
</ref>
<ref id="B5">
<nlm-citation citation-type="">
<collab>CNA (Comisión Nacional del Agua)</collab>
<source><![CDATA[Programa Hidráulico Regional 2002-2006 Región VI Río Bravo]]></source>
<year>2003</year>
<edition>1</edition>
<page-range>242</page-range><publisher-loc><![CDATA[México, D. F. ]]></publisher-loc>
</nlm-citation>
</ref>
<ref id="B6">
<nlm-citation citation-type="book">
<collab>CONAFOR (Comisión Nacional Forestal)</collab>
<source><![CDATA[Estadísticas semanales de incendios forestales en Chihuahua 1990-2004]]></source>
<year>2004</year>
<publisher-loc><![CDATA[Chihuahua, Chih. ]]></publisher-loc>
<publisher-name><![CDATA[Gerencia Región VI Río Bravo]]></publisher-name>
</nlm-citation>
</ref>
<ref id="B7">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Dracup]]></surname>
<given-names><![CDATA[J. A.]]></given-names>
</name>
<name>
<surname><![CDATA[Lee]]></surname>
<given-names><![CDATA[K.]]></given-names>
</name>
<name>
<surname><![CDATA[Paulson]]></surname>
<given-names><![CDATA[E.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[On the definition of droughts]]></article-title>
<source><![CDATA[Water Resources Res.]]></source>
<year>1980</year>
<volume>16</volume>
<page-range>297-302</page-range></nlm-citation>
</ref>
<ref id="B8">
<nlm-citation citation-type="book">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Edwards]]></surname>
<given-names><![CDATA[D.]]></given-names>
</name>
<name>
<surname><![CDATA[McKee]]></surname>
<given-names><![CDATA[T. B.]]></given-names>
</name>
</person-group>
<source><![CDATA[Characteristics of 20 century drought in the United States at multiple time scales]]></source>
<year>1997</year>
<page-range>155</page-range><publisher-loc><![CDATA[Fort Collins, Colorado, U.S.A. ]]></publisher-loc>
<publisher-name><![CDATA[Department of Atmospheric Sciences]]></publisher-name>
</nlm-citation>
</ref>
<ref id="B9">
<nlm-citation citation-type="book">
<person-group person-group-type="author">
<name>
<surname><![CDATA[García]]></surname>
<given-names><![CDATA[E.]]></given-names>
</name>
</person-group>
<source><![CDATA[Modificación del Sistema de Clasificación de Köppen]]></source>
<year>1973</year>
<page-range>247</page-range><publisher-loc><![CDATA[México D. F. ]]></publisher-loc>
<publisher-name><![CDATA[Instituto de Geografía. Universidad Autónoma de México]]></publisher-name>
</nlm-citation>
</ref>
<ref id="B10">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Glantz]]></surname>
<given-names><![CDATA[M.]]></given-names>
</name>
<name>
<surname><![CDATA[Katz]]></surname>
<given-names><![CDATA[R. W.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[When is a drought a drought?]]></article-title>
<source><![CDATA[Nature]]></source>
<year>1977</year>
<volume>267</volume>
<page-range>192-3</page-range></nlm-citation>
</ref>
<ref id="B11">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Guttman]]></surname>
<given-names><![CDATA[B. N.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[Comparing the Palmer Drought Index and the Standardized Precipitation Index]]></article-title>
<source><![CDATA[J. Am. Water Res. Asocc.]]></source>
<year>1998</year>
<volume>34</volume>
<numero>1</numero>
<issue>1</issue>
<page-range>113-21</page-range></nlm-citation>
</ref>
<ref id="B12">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Guttman]]></surname>
<given-names><![CDATA[B. N.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[Accepting the standardized precipitation index: a calculation algorithm]]></article-title>
<source><![CDATA[J. Am. Water Res. Asocc.]]></source>
<year>1999</year>
<volume>35</volume>
<numero>2</numero>
<issue>2</issue>
<page-range>311-22</page-range></nlm-citation>
</ref>
<ref id="B13">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Hayes]]></surname>
<given-names><![CDATA[M.]]></given-names>
</name>
<name>
<surname><![CDATA[Svoboda]]></surname>
<given-names><![CDATA[M. D.]]></given-names>
</name>
<name>
<surname><![CDATA[Wilhite]]></surname>
<given-names><![CDATA[D.A.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[Monitoring the 1996 drought using the Standardized Precipitation Index]]></article-title>
<source><![CDATA[Bull. Am. Meteorol. Soc.]]></source>
<year>1999</year>
<volume>80</volume>
<numero>3</numero>
<issue>3</issue>
<page-range>429-38</page-range></nlm-citation>
</ref>
<ref id="B14">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Komuscu]]></surname>
<given-names><![CDATA[A. U.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[Using the SPI to analyze spatial and temporal drought patterns in Turkey]]></article-title>
<source><![CDATA[Drought Network News]]></source>
<year>1999</year>
<volume>11</volume>
<numero>1</numero>
<issue>1</issue>
<page-range>7-13</page-range></nlm-citation>
</ref>
<ref id="B15">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Narasimhan]]></surname>
<given-names><![CDATA[B.]]></given-names>
</name>
<name>
<surname><![CDATA[Srinivasan]]></surname>
<given-names><![CDATA[R.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[Development and evaluation of Soil Moisture Deficit Index and Evapotranspiration Deficit Index for agricultural drought monitoring]]></article-title>
<source><![CDATA[Agric. For. Meteorol.]]></source>
<year>2005</year>
<volume>133</volume>
<page-range>69-88</page-range></nlm-citation>
</ref>
<ref id="B16">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Quiring]]></surname>
<given-names><![CDATA[M. S.]]></given-names>
</name>
<name>
<surname><![CDATA[Papakryiakou]]></surname>
<given-names><![CDATA[T. N.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[An evaluation of agricultural drought indices for the Canadian prairies]]></article-title>
<source><![CDATA[Agric. For. Meteorol.]]></source>
<year>2003</year>
<volume>118</volume>
<page-range>49-62</page-range></nlm-citation>
</ref>
<ref id="B17">
<nlm-citation citation-type="">
<collab>SAGARPA (Secretaría de Agricultura Ganadería y Pesca)</collab>
<source><![CDATA[Sistema de Información Agropecuaria de Consulta. Versión 1.1]]></source>
<year>2004</year>
<publisher-loc><![CDATA[México, D. F. ]]></publisher-loc>
</nlm-citation>
</ref>
<ref id="B18">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Steinemann]]></surname>
<given-names><![CDATA[Anne]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[Drought indicatos and triggers: A stochastic approach to evaluation]]></article-title>
<source><![CDATA[Journal of the American water Resource association]]></source>
<year>2003</year>
<volume>39</volume>
<numero>5</numero>
<issue>5</issue>
<page-range>1217-33</page-range></nlm-citation>
</ref>
<ref id="B19">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Tadesse]]></surname>
<given-names><![CDATA[T.]]></given-names>
</name>
<name>
<surname><![CDATA[Wilhite]]></surname>
<given-names><![CDATA[D. A.]]></given-names>
</name>
<name>
<surname><![CDATA[Harms]]></surname>
<given-names><![CDATA[S. K.]]></given-names>
</name>
<name>
<surname><![CDATA[Hayes]]></surname>
<given-names><![CDATA[M. J.]]></given-names>
</name>
<name>
<surname><![CDATA[Goddard]]></surname>
<given-names><![CDATA[S.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[Drought monitoring using data mining techniques: A case study for Nebraska, USA]]></article-title>
<source><![CDATA[Natural Hazards]]></source>
<year>2004</year>
<volume>33</volume>
<numero>1</numero>
<issue>1</issue>
<page-range>137-59</page-range></nlm-citation>
</ref>
<ref id="B20">
<nlm-citation citation-type="">
<collab>U.S. Drought Monitor</collab>
<source><![CDATA[Drought severity classification]]></source>
<year>1999</year>
<publisher-loc><![CDATA[Lincoln, Nebraska, U.S.A. ]]></publisher-loc>
</nlm-citation>
</ref>
<ref id="B21">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Velasco]]></surname>
<given-names><![CDATA[V. I.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[Severe droughts becoming recurrent more persistent in Mexico]]></article-title>
<source><![CDATA[Drought Network News]]></source>
<year>1999</year>
<volume>11</volume>
<numero>1</numero>
<issue>1</issue>
<page-range>3-6</page-range></nlm-citation>
</ref>
<ref id="B22">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Velasco]]></surname>
<given-names><![CDATA[V. I.]]></given-names>
</name>
<name>
<surname><![CDATA[Aparicio]]></surname>
<given-names><![CDATA[F. J.]]></given-names>
</name>
<name>
<surname><![CDATA[Valdés]]></surname>
<given-names><![CDATA[J.]]></given-names>
</name>
<name>
<surname><![CDATA[Velázquez]]></surname>
<given-names><![CDATA[J.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[Evaluación de índices de sequía en las cuencas afluentes del Río Bravo/Grande]]></article-title>
<source><![CDATA[Ing. Hidráulica Méx.]]></source>
<year>2004</year>
<volume>IX</volume>
<numero>3</numero>
<issue>3</issue>
<page-range>37-53</page-range></nlm-citation>
</ref>
<ref id="B23">
<nlm-citation citation-type="book">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Wanielista]]></surname>
<given-names><![CDATA[M. P.]]></given-names>
</name>
<name>
<surname><![CDATA[Kersten]]></surname>
<given-names><![CDATA[R.]]></given-names>
</name>
<name>
<surname><![CDATA[Eaglin]]></surname>
<given-names><![CDATA[R.]]></given-names>
</name>
</person-group>
<source><![CDATA[Hydrology]]></source>
<year>1997</year>
<page-range>567</page-range><publisher-loc><![CDATA[New York, U.S.A. ]]></publisher-loc>
<publisher-name><![CDATA[Wiley and Sons]]></publisher-name>
</nlm-citation>
</ref>
<ref id="B24">
<nlm-citation citation-type="book">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Wilhite]]></surname>
<given-names><![CDATA[D. A.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[Drought as a natural hazard]]></article-title>
<person-group person-group-type="editor">
<name>
<surname><![CDATA[Wilhite]]></surname>
<given-names><![CDATA[D. A.]]></given-names>
</name>
</person-group>
<source><![CDATA[Drought: A Global Assessment]]></source>
<year>2000</year>
<page-range>3-18</page-range><publisher-loc><![CDATA[London, UK ]]></publisher-loc>
<publisher-name><![CDATA[Routledge Publishers]]></publisher-name>
</nlm-citation>
</ref>
<ref id="B25">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Wilhite]]></surname>
<given-names><![CDATA[D. A.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[Combating drought through preparedness]]></article-title>
<source><![CDATA[Natural Resources Forum]]></source>
<year>2002</year>
<volume>26</volume>
<page-range>275-85</page-range></nlm-citation>
</ref>
<ref id="B26">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Wilhite]]></surname>
<given-names><![CDATA[D. A.]]></given-names>
</name>
<name>
<surname><![CDATA[Glantz]]></surname>
<given-names><![CDATA[M. H.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[Understanding the drought phenomenon: The role of definitions]]></article-title>
<source><![CDATA[Water Int.]]></source>
<year>1985</year>
<volume>10</volume>
<page-range>111-20</page-range></nlm-citation>
</ref>
<ref id="B27">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Wu]]></surname>
<given-names><![CDATA[H.]]></given-names>
</name>
<name>
<surname><![CDATA[Hubbard]]></surname>
<given-names><![CDATA[K. G.]]></given-names>
</name>
<name>
<surname><![CDATA[Wilhite]]></surname>
<given-names><![CDATA[D. A.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[An agricultural drought risk assessment model for corn and soybeans]]></article-title>
<source><![CDATA[Int. J. Climatol.]]></source>
<year>2004</year>
<volume>24</volume>
<page-range>723-41</page-range></nlm-citation>
</ref>
<ref id="B28">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Wu]]></surname>
<given-names><![CDATA[H.]]></given-names>
</name>
<name>
<surname><![CDATA[Hayes]]></surname>
<given-names><![CDATA[M. J.]]></given-names>
</name>
<name>
<surname><![CDATA[Wilhite]]></surname>
<given-names><![CDATA[D. A.]]></given-names>
</name>
<name>
<surname><![CDATA[Svoboda]]></surname>
<given-names><![CDATA[M. D.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[The effect of the length of record on the Standardized Precipitation Index Calculation]]></article-title>
<source><![CDATA[Int. J. Climatol.]]></source>
<year>2005</year>
<volume>25</volume>
<page-range>505-20</page-range></nlm-citation>
</ref>
<ref id="B29">
<nlm-citation citation-type="book">
<collab>WMO (World Meteorological Organization)</collab>
<source><![CDATA[Drought and Agriculture]]></source>
<year>1975</year>
<page-range>53</page-range><publisher-loc><![CDATA[Geneva, Switzerland ]]></publisher-loc>
<publisher-name><![CDATA[Report of CAg WorkingGroup on the Assessment of Drought]]></publisher-name>
</nlm-citation>
</ref>
<ref id="B30">
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname><![CDATA[Young]]></surname>
<given-names><![CDATA[K. C.]]></given-names>
</name>
</person-group>
<article-title xml:lang=""><![CDATA[A three-way model for interpolating for monthly precipitation values]]></article-title>
<source><![CDATA[Monthly Weather Rev.]]></source>
<year>1992</year>
<volume>120</volume>
<page-range>2561-9</page-range></nlm-citation>
</ref>
</ref-list>
</back>
</article>
