Tropical and extratropical forecast sensitivity to subtropical observational enhancement

LEE BYERLE; JAN PAEGLE; JULIA NOGUÉS-PAEGLE; CELESTE SAULO; JUAN RUIZ

Tucson, Arizona - USA

Conferencia; 29th AMS conference on hurricanes and tropical meteorology; 2010

American Meteorological Society

<!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-1610611985 1107304683 0 0 415 0;} @font-face {font-family:"Century Gothic"; panose-1:2 11 5 2 2 2 2 2 2 4; mso-font-charset:0; mso-generic-font-family:swiss; mso-font-pitch:variable; mso-font-signature:647 0 0 0 159 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:ES; mso-fareast-language:ES;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt;} @page WordSection1 {size:8.5in 11.0in; margin:1.0in 1.0in 1.0in 1.0in; mso-header-margin:.5in; mso-footer-margin:.5in; mso-paper-source:0;} div.WordSection1 {page:WordSection1;} --> The purpose of this work is to explore relevance of new atmospheric observations for weather prediction.This study tests sensitivity using variety of models and examines model biases.Data are from South American Low-level Jet Experiment (SALLJEX), austral Summer of 2002-2003 (Vera et al., 2006), and from North American Monsoon Experiment (NAME), boreal summer of 2004 (Higgins et al., 2006). Nonyhydrostatic Euler model displays at least twice as much 48-hr forecast sensitivity to the special field observations as do the regional WRF model or the global PE model. Model forecast sensitivity to initial state perturbations is strongly influenced by model diffusion.  Euler model retains the least diffusion. PE model shows greater sensitivity to initial obs when horizontal diffusivity depends upon local flow gradients. Although field experiment observations were centered in the sub- tropics, some of the strongest shorter term impact on forecast winds occurs in the tropics and then spreads to the extra-tropics later in the forecast. Growing biases in the global research/operational models w/time suggest common model deficiencies, as in Roman et al., 2004, which implied the current models do not adequately retain slowly-changing anomalous features characterized by intraseasonal variability.