TITLE

Radar Observations of the Diurnally Forced Offshore Convective Lines along the Southeastern Coast of Taiwan

AUTHOR(S)
Cheng-Ku Yu; Ben Jong-Dao Jou
PUB. DATE
June 2005
SOURCE
Monthly Weather Review;Jun2005, Vol. 133 Issue 6, p1613
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
This study documents offshore convective lines along the southeastern coast of Taiwan, a frequent but poorly understood mesoscale phenomenon that influences coastal weather during the Taiwan mei-yu season. Doppler radar and surface observations were gathered from a specially chosen period (11–15 May 1998) when the offshore convective lines were active off the southeastern coast of Taiwan. These observations were used to show the basic character, structure, and possible formative processes of offshore convective lines. The synoptic environment accompanying these events was found to be relatively undisturbed and featured uniformly prevailing southerly/south-southeasterly winds in the boundary layer with southwesterlies/westerlies aloft. Examination of radar data during the study period indicates that the lines generally occurred ∼10–30 km offshore and were characterized by an elongated narrow zone (∼5–10 km wide) of heavy precipitation. The lines were oriented roughly parallel to the coastline and generally did not move significantly. The intensity of the radar reflectivity associated with the lines exhibited a marked diurnal variation and was closely related to the coastal offshore flow developing at night. Detailed analyses of an event on 14–15 May 1998 further show the important physical link between the offshore flow and the development of the line. The offshore line was found to be located near and immediately ahead of the seaward extent of the offshore flow. Particularly, a very narrow zone (∼2 km) of low-level heavy precipitation (40–45 dBZ) coincided with regions of strong updrafts and convergence, where the prevailing southerly onshore flow encountered the cool offshore flow nearshore. This offshore flow–induced convergence, given a stable thermodynamic condition in the lowest ∼1 km in the inflow region, was a crucial low-level forcing that provided lifting to trigger moist deep convection in this case. The line’s precipitation tilt eastward was confined primarily to the warmer inflow side rather than feeding the offshore flow to the west of the line. No consistent upshear tilt of updrafts throughout the storm layer was observed, which is consistent with the presence of a strong westerly shear in the line’s environment. Both of these observations explain a relatively strong (weak) modification of low-level onshore (offshore) flow by precipitation. Additionally, a combination of surface and Doppler radar observations indicates that the leading edge of the offshore flow moved seaward very slowly at 0.7 m s-1 and possessed a frontal character with notable discontinuities in near-surface wind and temperature (instead of pressure and dewpoint temperature).
ACCESSION #
17434838

 

Related Articles

  • Secular change of extreme monthly precipitation in Europe. C.-D. Schönwiese; J. Grieser; S. Trömel // Theoretical & Applied Climatology;2003, Vol. 75 Issue 3/4, p245 

    Summary ¶Temporal changes in the occurrence of extreme events in time series of observed precipitation are investigated. The analysis is based on a European gridded data set and a German station-based data set of recent monthly totals (1896/1899?1995/1998). Two approaches are used. First,...

  • An evaluation of UKMO one-month ensemble forecasts of MSLP in the Southern Hemisphere. R. I. C. C. Francis; A. B. Mullan; J. A. Renwick // Theoretical & Applied Climatology;2003, Vol. 75 Issue 1/2, p1 

    summary�we evaluate united kingdom meteorological office (ukmo) one-month ensemble forecasts of mean sea-level pressure (mslp) in the southern hemisphere (sh) to 60� s, with a special focus on their utility near new zealand (nz). there are 105 9-member ensembles, at approximately...

  • CANADA DRY. Shilts, Elizabeth // Canadian Geographic;Nov/Dec2001, Vol. 121 Issue 6, p25 

    Presents information on the weather condition of Canada in summer 2001. Effect of the lack of rain in southern areas; Weather forecast for winter 2002.

  • Tropical tele-connections to the Mediterranean climate and weather. Alpert, P.; Price, C.; Krichak, S. O.; Ziv, B.; Saaroni, H.; Osetinsky, I.; Barkan, J.; Kishcha, P.; Ferraris, L.; Pawlowsky-Glahn, V. // Advances in Geosciences;2005, Vol. 2, p157 

    Some strong natural fluctuations of climate in the Eastern Mediterranean (EM) region are shown to be connected to the major tropical systems. Potential relations between EM rainfall extremes to tropical systems, e.g. El Niño, Indian Monsoon and hurricanes, are demonstrated. For a specific...

  • Attribution and Characteristics of Wet and Dry Seasons in the Upper Colorado River Basin. Bolinger, Rebecca A.; Kummerow, Christian D.; Doesken, Nolan J. // Journal of Climate;Dec2014, Vol. 27 Issue 23, p8661 

    Previous research has shown that the temperature and precipitation variability in the Upper Colorado River basin (UCRB) is correlated with large-scale climate variability [i.e., El Niño-Southern Oscillation (ENSO) and Pacific decadal oscillation (PDO)]. But this correlation is not very...

  • World weather.  // Travel Weekly: The Choice of Travel Professionals;10/29/2004, Issue 1742, p115 

    This article presents weather conditions around the world. Some of the countries where the weather is fogy are Amsterdam, Athens, Bahamas, Barbados, Barcelona, Berlin, Brussels, and Cairo.

  • Weather. Georges, Jason; Irons-Georges, Tracy // Rourke's World of Science Encyclopedia;1999 Earth Science, Vol. 4, p30 

    The weather influences many things on Earth. Air and water can be hot or cold. It can have a lot of moisture or none at all. Wind is created by changes in atmospheric pressure. Sometimes it develops into tornadoes and hurricanes, and causes destruction. Clouds are formed by evaporation. They...

  • The Four seasons. Love, Chad // Oklahoma Today;May/Jun2005, Vol. 55 Issue 3, p42 

    The article present information about the weather conditions in Oklahoma. Oklahoma weather can be broken down into two distinct terms: climate and weather. Oklahoma's climate is a product of geography. The comings and goings of far-off Pacific Ocean currents, the rotation of the atmosphere from...

  • Measuring the Mississippi. Kowalski, Kathiann M. // Appleseeds;Apr2005, Vol. 7 Issue 8, p30 

    This article reports that the Mississippi River is ever-changing. The length, width, depth, shape, and water flow are different at any given time or place along the river. Weather has a huge effect on the river. When it rains or snows either a great deal or very little, the amount of water in...

Share

Read the Article

Courtesy of THE LIBRARY OF VIRGINIA

Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics