<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Francesco,<div><br></div><div>Thank you for calling our attention to this error in our documentation. The omission of the 1- piece is a typo. </div><div><br></div><div>However, it turns out that the actual formula used for the calculation is not this one, as it fails to handle ties in the ranks. To handle ties, we use the formula for the Pearson correlation, but with the ranks as input rather than the raw data. The most accessible reference for this is on Wikipedia ( we use the second formula listed ). </div><div><br></div><div><a href="http://en.wikipedia.org/wiki/Spearman's_rank_correlation_coefficient">http://en.wikipedia.org/wiki/Spearman's_rank_correlation_coefficient</a></div><div><br></div><div>We will update the documentation to reflect the correct formula for this statistic. </div><div><br></div><div>Thanks much,</div><div><br></div><div>Tressa</div><div><br></div><div><br><div><div>On Apr 20, 2009, at 4:55 AM, Francesco Piani wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; "><div bgcolor="#ffffff"><div><font face="Arial" size="2">Good morning.</font></div><div><font face="Arial" size="2">I'm a weather forecaster working for Tuscany Region, Italy. We use WRF-NMM as an operational model and MET to verify its results. In the MET user guide, appendix C, the Spearman rank correlation is indicated as 6/n(n2-1)*... instead of 1-6/n(n2-1)*..., as indicated in many articles (Schultz, 1995, An explicit cloud physics parameterization for operational numerical weather prediction, Mon. Wea. Rev., 123, 3331-3343).</font></div><div><font face="Arial" size="2">I would like what is the method used in MET to calculate this index, in order to interpret statistical results in a reasonable way.</font></div><div><font face="Arial" size="2"></font> </div><div><font face="Arial" size="2">Thanks in advance.</font></div><div><font face="Arial" size="2"></font> </div><div><font face="Arial" size="2">Francesco Piani</font></div><div> </div><div><font face="Arial" size="2">-------------------------------------------------------------<br>Dott.Ing. Francesco Piani<br>Weather Forecaster<br>Tuscany Region - Hydrological Service - Centro Funzionale<br>Laboratory for Meteorology and Environmental Modelling - National Council of Research<br>Via Madonna del Piano, 10 - Building D<br>50019 Sesto Fiorentino (Fi)<span class="Apple-converted-space"> </span><br> Italy</font></div><div> </div><div><font face="Arial" size="2">Tel. +39 055 44 830.23<br>Fax +39 055 44 40 83<br>email:<span class="Apple-converted-space"> </span><a href="mailto:piani@lamma.rete.toscana.it">piani@lamma.rete.toscana.it</a><br>email:<span class="Apple-converted-space"> </span><a href="mailto:francesco.piani@regione.toscana.it">francesco.piani@regione.toscana.it</a></font></div>_______________________________________________<br>Met_help mailing list<br><a href="mailto:Met_help@mailman.ucar.edu">Met_help@mailman.ucar.edu</a><br><a href="http://mailman.ucar.edu/mailman/listinfo/met_help">http://mailman.ucar.edu/mailman/listinfo/met_help</a><br></div></span></blockquote></div><br></div></body></html>