Interannual Variability of Snowfall Events Southwest Missouri and Snowfall to- Liquid Water Equivalents at the Springfield WFO

In order to address the difficult issue of forecasting snowfall amounts for the general public, forecasters must be intimately familiar with the climatological behavior of snowfall events, and associated snowfall-to-liquid precipitation (SL) ratios that accompany events impacting the region. In Southwest Missouri, an average of 4 to 5 snowfall events of 3 inches or more occurred every year within the period of 1949 to 2002. These events were associated with an average SL ratio of about 12 inches of snow to one inch of rain (12:1). Past studies have also demonstrated relationships between the synoptic environment and SL ratios for a particular locale. Indeed, while many atmospheric and environmental factors contribute to the observed SL ratios in a particular event, quite often, recurring synoptic patterns are typically associated with similar SL ratios in Southwest Missouri. This study identified four synoptic patterns that bring heavy snowfalls to Southwest Missouri and these are associated predominantly with certain SL ratios. In Southwest Missouri, synoptic disturbances classified as southwest lows or deepening lows, processed large amounts of moisture and produced heavy snow. Sixty-seven percent of these events produced SL ratios of 12:1 or less, and 90% produced SL ratios of 14:1 or less. Snowfall events (progressive troughs and northwest lows) which brought less snowfall were typically associated with higher SL ratios. There was no significant El Nino-Southern Oscillation (ENSO) related difference in the number of snowfalls per winter season. When the study period was stratified to include interdecadal variability, changes in ENSO- related variability did emerge. Additionally, the SL ratios were smaller during El Niño years and there has been no trend in this tendency

Spatial characteristics of a zero-pressure-gradient turbulent boundary layer in the presence of free-stream turbulence

Particle image velocimetry (PIV) measurements are performed to examine the structural organization inside a turbulent boundary layer under the influence of free-stream turbulence (FST). In particular, streamwise-wall-normal plane PIV measurements are presented for two cases at two different turbulent intensity levels (about 13% and 8%). The free-stream turbulence is generated using an active grid in a wind tunnel. The statistical information of the flow regarding the wall-normal velocity and Reynolds shear stress are presented. The effect of increasing the turbulence level in the free stream for these flows has been found to have similarities with increasing Reynolds number for high-Reynolds-number canonical flows. Quadrant analysis is performed to determine the contributions of different Reynolds-stress-producing events. In this regard, the distribution of momentum transport events shows some similarity with channel flows, which can be justified by comparison of similar intermittency characteristics of both flows. In addition, the coherent structures found inside the boundary layer have inclined features that are consistent with the previous studies for canonical flows. The fact that the external disturbance, such as FST in this study, does not alter the organization of the structures inside the boundary layer supports the growing evidence for a universal structure for wall-bounded flows

Response Acquisition and Fixed-Ratio Escalation Based on Interresponse Times in Rats

The effectiveness of a fixed-ratio (FR) escalation procedure, developed by Pinkston and Branch (2004) and based on interresponse times (IRTs), was assessed during lever-press acquisition. Forty-nine experimentally naïve adult male Long Evans rats were deprived of food for 24 hr prior to an extended acquisition session. Before the start of the session, three food pellets were placed in the magazine. Otherwise, no magazine training, shaping, nor autoshaping procedure was employed. The first 20 presses each resulted in the delivery of a 45-mg food pellet. Then, the FR increased (2, 4, 8, 11, 16, 20, 25, 30) when each IRT in the ratio was less than 2 s during three consecutive ratios. Sessions lasted 13 hr or until 500 pellets were earned. On average, rats reached a terminal ratio of 11 (mean) or 16 (median) during the first session. Seven rats reached the maximum value of FR 30 and only one rat did not acquire the response. In most rats, a break-and-run pattern of responding characteristic of FR schedules began to develop in this acquisition session. Subsequently, the ratio-escalation procedure continued during daily 2-hr sessions. In these sessions, the starting ratio requirement was set at the terminal ratio reached in the previous session. Using this procedure, over half (26) of the rats reached the FR 30 requirement by the fourth session. These data demonstrate that a ratio-escalation procedure based on IRTs provides a time-efficient way of establishing ratio responding