Search Results

You are looking at 1 - 2 of 2 items for :

  • Author or Editor: William G. Pichel x
  • Weather and Forecasting x
  • Refine by Access: All Content x
Clear All Modify Search
Todd D. Sikora
,
Karen S. Friedman
,
William G. Pichel
, and
Pablo Clemente-Colón

Abstract

Polar mesoscale cyclones are intense vortices that form in cold, marine air masses poleward of major jet streams and frontal zones. Synthetic aperture radar (SAR) should be considered as a potential tool for the study of polar mesoscale cyclones because of its ability to remotely sense, at least qualitatively, the high-resolution near-surface wind field independent of daylight and atmospheric conditions. Four case studies demonstrating this ability are presented. SAR imagery from the Canadian Space Agency’s RADARSAT are compared to corresponding infrared imagery, surface analyses, and upper-air analyses. In three of the four case studies, it is argued that the addition of SAR imagery to the process of generating a manual surface analysis would have led to a better product. Moreover, it is demonstrated that the SAR imagery reveals a host of marine-meteorological phenomena in the vicinity of the polar mesoscale cyclones including atmospheric gravity waves, roll vortices, and cellular convection. Because of the high-resolution attributes of SAR imagery, SAR shows promise to aid the forecaster and researcher in the study of marine-meteorological phenomena such as polar mesoscale cyclones.

Full access
Karen S. Friedman
,
Todd D. Sikora
,
William G. Pichel
,
Pablo Clemente-Colón
, and
Gary Hufford

Abstract

The ever-changing weather and lack of in situ data in the Bering Sea warrants experimentation with new meteorological observing systems for this region. Spaceborne synthetic aperture radar (SAR) is well suited for observing the sea surface footprints of marine meteorological phenomena because its radiation is sensitive to centimeter-scale sea surface roughness, regardless of the time of day or cloud conditions. The near-surface wind field generates this sea surface roughness. Therefore, the sea surface footprints of meteorological phenomena are often revealed by SAR imagery when the main modulator of sea surface roughness is the wind. These attributes, in addition to the relatively high resolution of SAR products, make this instrument an excellent candidate for filling the meteorological observing needs over the Bering Sea.

This study demonstrates the potential usefulness of SAR for observing Bering Sea meteorology by focusing on its ability to image the sea surface footprints of polar mesoscale cyclones (PMCs). These storms can form unexpectedly and are threatening to maritime interests. In this demonstration, a veteran meteorologist at the Anchorage National Weather Service Forecast Office is asked to produce a surface reanalysis for three separate archived cases when SAR imaged a PMC but the original analysis, produced without the aid of SAR data, did not display it. The results show that in these three cases the inclusion of SAR data in the analysis procedure leads to large differences between the original surface analysis and the reanalysis. Of particular interest is that, in each case, the PMC is added into the reanalysis. It is argued that the reanalyses more accurately portray the near-surface meteorology for each case.

Full access