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Abstract
This study utilized the MM5 mesoscale model to simulate the landfalling process of Typhoon Talim.
The simulated typhoon track, weather patterns, and rainfall process are consistent with the observation.
Using the simulation results, the relation of the second type thermal helicity (H2) to rainfall caused by the
landfalling typhoon Talim was analyzed. The results show that H2 could well indicate the heavy inland
rainfall but it did not perform as well as the helicity in predicting rainfall during the beginning stage of
the typhoon landfall. In particular, H2 was highly correlated with rainfall of Talim at 1-h lead time. For
15-h lead time, it also had a higher correlation with rainfall than the helicity did, and thus showing a
better potential in forecasting rainfall intensification. Further analyses have shown that when Talim was in
the beginning stage of landfall, 1) the 850-200-hPa vertical wind shear around the Talim center was quite
small (about 5 m s-1); 2) the highest rainfall was to the right of the Talim track and in the area with a
300-km radius around the Talim center, exhibiting no obvious relation to low-level temperature advection,
low-level air convergence, and upper-level divergence; 3) the low-level relative vorticity reflected the rainfall
change quite well, which was the main reason why helicity had a better performance than H2 in this period.
However, after Talim moved inland further, 1) it weakened gradually and was increasingly affected by the
northern trough; 2) the vertical wind shear was enhanced as well; 3) the left side of the down vertical
wind shear lay in the Lushan and Dabieshan mountain area, which could have contributed to triggering a
secondary vertical circulation, helping to produce the heavy rainfall over there; hence, H2 showed a better
capacity to reflect the rainfall change during this stage.
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Citation
YU Zifeng, YU Hui. 2011: Relation of the Second Type Thermal Helicity to Precipitation of Landfalling Typhoons: A Case Study of Typhoon Talim. Journal of Meteorological Research, 25(2): 224-237. DOI: 10.1007/s13351-011-0029-4
YU Zifeng, YU Hui. 2011: Relation of the Second Type Thermal Helicity to Precipitation of Landfalling Typhoons: A Case Study of Typhoon Talim. Journal of Meteorological Research, 25(2): 224-237. DOI: 10.1007/s13351-011-0029-4
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YU Zifeng, YU Hui. 2011: Relation of the Second Type Thermal Helicity to Precipitation of Landfalling Typhoons: A Case Study of Typhoon Talim. Journal of Meteorological Research, 25(2): 224-237. DOI: 10.1007/s13351-011-0029-4
YU Zifeng, YU Hui. 2011: Relation of the Second Type Thermal Helicity to Precipitation of Landfalling Typhoons: A Case Study of Typhoon Talim. Journal of Meteorological Research, 25(2): 224-237. DOI: 10.1007/s13351-011-0029-4
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