Errors in Estimated Temporal Tracer Trends Due to Changes in the Historical Observation Network: A Case Study of Oxygen Trends in the Southern Ocean

Abstract A case study illustrating the impact of moisture variability on convection initiation in a synoptically active environment without strong moisture gradients is presented. The preconvective environment on 30 April 2007 nearly satisfied the three conditions for convection initiation: moisture, instability, and a low-level lifting mechanism. However, a sounding analysis showed that a low-level inversion layer and high LFC would prevent convection initiation because the convective updraft velocities required to overcome the convective inhibition (CIN) were much higher than updraft velocities typically observed in convergence zones. Radar refractivity retrievals from the Twin Lakes, Oklahoma (KTLX), Weather Surveillance Radar-1988 Doppler (WSR-88D) showed a moisture pool contributing up to a 2°C increase in dewpoint temperature where the initial storm-scale convergence was observed. The analysis of the storm-relative wind field revealed that the developing storm ingested the higher moisture associated with the moisture pool. Sounding analyses showed that the moisture pool reduced or nearly eliminated CIN, lowered the LFC by about 500 m, and increased CAPE by 2.5 times. Thus, these small-scale moisture changes increased the likelihood of convection initiation within the moisture pool by creating a more favorable thermodynamic environment. The results suggest that refractivity data could improve convection initiation forecasts by assessing moisture variability at finer scales than the current observation network.

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Numerical Modelling of Iceberg Towing for Water Supplies—A Case Study

Journal of Glaciology ◽

10.1017/s002214300002092x ◽

1978 ◽

Vol 20 (84) ◽

pp. 533-542 ◽

Cited By ~ 10

Author(s):

J.G. Job

Keyword(s):

Numerical Modelling ◽

Southern Ocean ◽

Hydrodynamic Model ◽

Minimum Energy ◽

Two Dimensional ◽

Water Supplies ◽

Antarctic Continent ◽

Energy Consumptions ◽

The Antarctic

AbstractsThe towing of unprotected icebergs from the Antarctic continent (66° S.) to latitude 38° S. has been simulated using an explicit hydrodynamic model and an extended two-dimensional melting model. It was found that nominal towing accelerations in excess of 2 × 10-5m s-2were required to deliver ice over this route in most circumstances, and minimum energy consumptions were obtained at accelerations around 10-4m s-2. Unprotected icebergs could be delivered with about 50% yield to latitude 38° S., but the rate of deterioration in the warm waters indicates that protection would be required for longer journeys. The towing simulation was most sensitive to north-south current components, the total towing distance and the rate of iceberg deterioration. Efforts directed towards locating suitable icebergs in the region 50° S. to 60° S., and towards increasing knowledge of the changing current patterns in the Southern Ocean would be most valuable, as would a knowledge of the mechanisms and rates of deterioration of icebergs in warm seas.

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