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Occurrence and Coverage of Winter Season Fog in the Northern Mid-Atlantic Paul J. Croft & Aaron N. Burton G&MDepartment of Geology and MeteorologyKean University
Why Fog?? • Low C/V directly impacts aviation as well as regular transportation particularly in the winter season • Improve forecasts of coverage & occurrence • Lack of knowledge • Fog studied widely from a micro-physical & mesoscale standpoint • Synoptic considers type of atmospheres that potentially produce fog • Improving forecasting and dispersal techniques
Methods • Data collection • Fog frequencies obtained from F-6 reports @ http://www.erh.noaa.gov • Study Period: 3 seasons (Dec-Feb) 2003-2004, 2004-2005, & 2005-2006 • Synoptic Classification • Classic approach • Microphysical approach • Physiographic approach • Spatial Distribution & Frequency of fog according to observed Synoptic Type
Spatial Coverage Defined Less than 4 sites report (<29% of sites): Localized 4 -10 sites report (29% to 71% of sites): Scattered More than 10 sites report (>71% of sites): Widespread Fog Criteria Capture as many events as possible for region – liberal/conservative Fog is defined as FG or BR @ 5sm or less Criteria for dense fog is visibility <1/4SM Fog event defined when any one of the 14 stations reported fog on any day Methods (cont.)
Methods (cont.) • Each fog event & non-event classified by synoptic type through inspection of DWM series • Type “A”: High; Type “B”: Low; Type “C”: Frontal • Subtypes determined by location of H/L with regard to the center of the region & FROPA type • Why Synoptic Typing? • To help determine the coverage according to the synoptic regime and local physiographic features • Isolate the primary factors related to fog coverage during those regimes and improve regional forecast
Total Frequency (days) Fog by Location Very Frequent in Winter! MPO Max 79% 215 events out of 271 possible days Only 56 Non-Events
High Pressure Frequencies NE Urban Minimum Very Sparse
Low Pressure Frequencies Northern Preference
Frontal Frequencies Western Preference/MPO Max Orographic/Marine Influences
Composites Examine synoptic regime Consider zone forecasts
Conclusions/Findings • Prime Locations – MPO, ISP, RDG • Although type “A” (High) was most frequent of all synoptic types, type “B” (Low) & “C” (Front) were more prolific & efficient at generating fog • “B” and “C” also had greater coverage & intensity • Warm Fronts and Low ‘S-SW’ significant • Maximum percentage of dense events occurred with the warm frontal events • Events associated with a Low S-SW were widespread • Forecast & Verification aspects to be considered
References • Baker, R., Cramer, J., and Peters, J., year: Radiation fog: UPS airlines conceptual models and forecast methods. • Bendix, J., 2002: A satellite-based climatology of fog and low-level stratus in Germany and adjacent areas. J. Atmos. Res., 64: 3-18. • Bott, A., and Trautmann, T., 2002: PAFOG: A new efficient forecast model of radiation fog and low-level stratiform clouds. J. Atmos. Res., 64: 191-203. • Croft, P. J., 2002: Encyclopedia of Atmospheric Sciences - Fog, Edited by James R. Holton, John Pyle, and Judith A. Curry December 2002, Elsevier / Academic Press, ISBN: 0-12-227090-8 • Croft, P. J., Pfost, R., Medlin, J., Johnson, A., 1997. Fog forecasting in the southern region: A conceptual model approach. Weather and Forecasting, 12, 545-556. • Chang, Kang-tsung. Introduction to Geographic Systems. New York, New York, 2004. • Fuchs, W., Schickel, K. P., 1995: Aircraft icing in visual meteorological conditions below low stratus clouds. J. Atmos. Res., 36: 339-345. • George, J. J., 1963: Weather forecasting for Aeronautics. Eastern Airlines – Atlanta, Georgia. • Leipper, D. F., 1994: Fog on the U. S. west coast: A review. Bull. Amer. Met. Soc., 75, 229-240.
Acknowledgements • Department of Geology and Meteorology faculty and staff at Kean University • The Department in access to GIS software and laboratory resources • Dr. John F. Dobosiewicz and Will Heyniger • Philadelphia NWS and the Office of the New Jersey State Climatologist • Thankful for their support and helpful insights during the completion of this project. • The images provided by the NOAA-CIRES Climate Diagnostics Center, Boulder Colorado • http://www.cdc.noaa.gov/based on the NCEP Re-Analysis data. NCEP Reanalysis data provided by the NOAA-CIRES Climate Diagnostics Center, Boulder, Colorado, USA Questions? Thank you!