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UID:20250515T111326EDT-4991joEtoz@132.216.98.100
DTSTAMP:20250515T151326Z
DESCRIPTION:Speaker 1: Ya-Chien Feng\n\nTitle: Better use of ground targets
  for radar refractivity retrievals\n\nAbstract\n\nRadar refractivity retri
 evals provide insight on the high-resolution distribution of near-surface 
 moisture that is considered important to study convective and boundary lay
 er processes. These retrievals are based on the fact that the phase of a s
 tationary target changes with the refractivity index of air along the rada
 r beam path.  Accurate refractivity retrievals are critical for quantitati
 ve applications\, such as assimilating refractivity into numerical models 
 or radar network implementation.  To obtain a good quality refractivity fi
 eld at a given height above the terrain\, it is necessary to know the vert
 ical gradient of refractivity (dN/dh) between the radar and the target.\n
 \nA new method for determining the vertical profile of refractivity is pro
 posed based on the power pattern of selected point-like ground targets.  T
 he temporal evolution of the returned power from the targets records the d
 iurnal variation of the dN/dh associated with the near-surface mixing cond
 itions that affect the radar beam propagation.  The resulting dN/dh estima
 tion shows skill based on in-situ tower observation.  The newly obtained i
 nformation shall improve the original refractivity retrieval method\, espe
 cially on complex topography.\n\n \n\nSpeaker 2: Bryn Ronalds\n\nTitle:  O
 n the relationship between North Atlantic baroclinic growth rate regimes a
 nd surface cyclogenesis\n\nAbstract\n\nBaroclinic instability is the prima
 ry mechanism for midlatitude surface cyclogenesis. A metric used to measur
 e this is the baroclinic growth rate\, which is a calculation of both the 
 static stability and horizontal temperature gradients over the bottom laye
 r of the troposphere (850-600 hPa). An areal coverage of the North Atlanti
 c basin (25-60°N and 0-80°W) by high moist baroclinic growth rates (σm) wa
 s computed in order to identify large-scale ideal conditions for cyclogene
 sis\, and a time series of the standardized anomalies was obtained. Concen
 trating solely on the cold season months (DJF)\, all synoptically independ
 ent events with standardized anomalies greater than two and length greater
  than four consecutive days were identified (n=7). It was found that each 
 was associated with significantly anomalous cold thicknesses over a large 
 portion of North America prior to the event\, and warm thickness anomalies
  on the equatorward side of the jet during the event. Each event also had 
 very deep low pressure centres over the northeast quadrant of the North At
 lantic. Most of the cyclones within the basin deepened with a rate greater
  than 1 Bergeron\, therefore fitting the definition of bombogenesis\, and 
 were located within the poleward exit region of an anomalously strong and 
 zonally extended tropopause jet.\n\n \n
DTSTART:20151021T183000Z
DTEND:20151021T193000Z
LOCATION:Room 934\, Burnside Hall\, CA\, QC\, Montreal\, H3A 0B9\, 805 rue 
 Sherbrooke Ouest
SUMMARY:Student Seminar: Ya-Chien Feng
URL:/meteo/channels/event/student-seminar-ya-chien-fen
 g-255054
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