Shijiazhuang, China
Shijiazhuang, China

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Zhang D.-L.,Nanjing University of Information Science and Technology | Zhang D.-L.,University of Maryland University College | Tian L.,University of Maryland University College | Tian L.,Hebei Meteorological Observatory | And 2 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2011

In this study, the origin and genesis of Typhoon Nari (2001) as well as its erratic looping track, are examined using large-scale analysis, satellite observations, and a 4 day nested, cloud-resolving simulation with the finest grid size of 1.33 km. Observational analysis reveals that Nari could be traced 5 days back to a diurnally varying mesoscale convective system with growing cyclonic vorticity and relative humidity in the lower troposphere and that it evolved from a mesoscale convective vortex (MCV) as moving over a warm ocean under the influence of a subtropical high, a weak westerly baroclinic disturbance, an approaching-and-departing Typhoon Danas to the east, and the Kuroshio Current. Results show that the model reproduces the genesis, final intensity, looping track, and the general convective activity of Nari during the 4 day period. It also captures two deep subvortices at the eye-eyewall interface that are similar to those previously observed, a few spiral rainbands, and a midget storm size associated with Nari's relatively dry and stable environment. We find that (1) continuous convective overturning within the MCV stretches the low-level vorticity and moistens a deep mesoscale column that are both favorable for genesis; (2) Nari's genesis does not occur until after the passage of the baroclinic disturbance; (3) convective asymmetry induces a smaller-sized vortex circulation from the preexisting MCV; (4) the vortex-vortex interaction with Danas leads to Nari's looping track and temporal weakening; and (5) midlevel convergence associated with the subtropical high and Danas accounts for the generation of a nearly upright eyewall. Copyright 2011 by the American Geophysical Union.

Chai D.-H.,Hebei Meteorological Observatory | Chai D.-H.,Hebei Eco Environmental Monitoring Laboratory | Yang X.-L.,Hebei Meteorological Observatory | Li J.-B.,Hebei Meteorological Observatory | And 4 more authors.
Journal of Natural Disasters | Year: 2010

In the late December 2007, the greenhouse vegetables underwent serious damage over the central and southern plains of Hebei Province, leading to a considerable reduction of vegetable production. The main weather environment causing this disaster is the persistent heavy frog, which resulted from the long-duration of high humidity , lack of sunshine and low temperature. The high level westerly wind, preventing the cold air from high latitude intruding the plain, and the cold air spreading from the surface high pressure are suitable for the formation of heavy fog. In the early stage of the heavy fog, the low - level southerly wind, the water vapor convergence and the lowlevel shear provided good water vapor condition for the fog. The formation and maintenance of the temperature inversion produce the favorable stratification condition. Small northerly wind at night and little cloud are suitable for the formation of droplet. The strong cold air intrusion is the main cause for the persistent heavy fog. This work presents key points for persistent fog prediction and the disaster prevention measures for greenhouses vegetables.

Chai D.-H.,Hebei Meteorological Observatory | Chai D.-H.,Hebei Ecoenvironmental Monitoring Laboratory | Li Z.-T.,Hebei Meteorological Observatory | Tian Y.-T.,Hebei Lightning Protection Center | And 3 more authors.
Journal of Natural Disasters | Year: 2011

Using cloud-to-ground lightning data provided by electric department of Hebei Provinoe from January, 2003 to December 2007, spatiotemporal distribution of lightning activity was analyzed. The results indicate that the high density region of cloud-to-ground lightning is located in central and southern windward slope of the Taihang Mountains, eastern windward slope of Yanshan Mountains and plains of the partial area. The distribution mostly corresponds to valley and mountain areas, windward slope of mountains, water source and iron ore rich regions. The cloud-to-ground lightning activity exhibits a seasonal variation and the variation mainly occurs from April to October with a maximum activity period from June to August, which has a good correlation with the ridge line of Subtropical high. The cloud-to-ground lightning activity also exhibits a diurnal variation, which peaks during 15:00-17:00, reverses during 10:00-11:00.

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