3.2 IOP 16/LOW 39A

This system is proposed as a case study primarily because it has received attention from CETP and JCMM in the past years. It was very successfully surveyed by two aircrafts. This perturbation was associated to a fast moving, rapidly deepening, secondary frontal wave, which unusually intensified in the eastern part of the North Atlantic. A very nice feature of this IOP is that the low was actually forming during the MSA mission. The clouds were initially confined to the baroclinic jet-stream, and evolved into a cyclonic cloud-head. A few hours after the MSA flights, Low 39 underwent a rapid development, accompanied with an amplification of vorticity of 2.1 in 18 hours.

The following figures give a brief summary of IOP 16.

  

Figure 7: IOP 16: METEOSAT infrared images (left) and ARPEGE MSLP and 2 meter-T fields (right) for for 970216 at 18hUTC (top), 970217 at 12hUTC (middle), and 970217 at 18hUTC (bottom).

  

Figure 8: IOP 16: Available FASTEX observations.

The following pictures display cloud related fields, either simulated by the operational model ARPEGE, or retrieved from satellites observations, on 970217 at 12hUTC.

  

Figure 9: IOP 16: Composite infrared satellite image from 970217 at 12hUTC.

  

Figure 10: IOP 16: Outgoing longwave radiation at the top of the atmosphere (W/m²), from the ARPEGE operational 12-hour forecast, on 970217 at 12hUTC.

  

Figure 11: IOP 16: SSM/I composite liquid water content (g/m²) on 970217 around 12hUTC (from NASA/MSFC DAAC).

  

Figure 12: IOP 16: SSM/I composite water vapor content (kg/m²) on 970217 around 12hUTC (from NASA/MSFC DAAC).