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Xie Q.,CAS South China Sea Institute of Oceanology | Xie Q.,Chinese Academy of Sciences | Huang K.,CAS South China Sea Institute of Oceanology | Huang K.,University of Chinese Academy of Sciences | And 6 more authors.
Acta Oceanologica Sinica | Year: 2014

Temperature and relative humidity profiles derived from two China-made global positioning system (GPS) radiosondes (GPS-TK and CF-06-A) during the east tropical Indian Ocean (ETIO) experiment were compared with Vaisala RS92-SGP to assess the performances of China-made radiosondes over the tropical ocean. The results show that there have relative large biases in temperature observations between the GPSTK and the RS92-SGP in the low troposphere, with a warmbias of greater than 2 K in the day and a cooling bias of 0.6 K at night. The temperature differences of the CF-06-A were small in the troposphere both in daytime and nighttime, and became large peak-to-peak fluctuations in the stratosphere. The intercomparison of the relative humidity showed that the CF-06-A had large random errors due to the limitation of sensors and the lack of correction scheme, and the GPS-TK had large systematic biases in the low troposphere which might be related to the temperature impact. GPS height measurements are clearly suitable for China-made radiosonde systems operation. At night, the CF-06-A and the GPS-TK could provide virtual potential temperature and atmospheric boundary layer height measurements of suitable quality for both weather and climate research. As a result of the intercomparison experiment, major errors in the China-made radiosonde systems were well indentified and subsequently rectified to ensure improving accuracy for historical and future radiosondes. © The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2014.

Qian Y.-K.,Sun Yat Sen University | Liang C.-X.,Sun Yat Sen University | Liang C.-X.,South China Sea Marine Prediction Center | Liang Q.,Guangzhou Meteorological Observatory | And 2 more authors.
Advances in Atmospheric Sciences | Year: 2011

A real case study for the transformation of Tropical Storm (TS) Haima (2004) into an extratropical cyclone (EC) is carried out numerically since, after landfall, Haima (2004) (as an EC) brought severe weather to a large area (from the south to the north) in China during 13-16 September 2004. With the linear diagnostic model (derived in a previous study) for the tangentially-averaged radial-vertical circulation within vortices moving on the spherical Earth, Haima's (2004) life cycle is reconstructed noticeably well. Therefore, the major contributor could be identified confidently for Haima's (2004) extratropical transition based on the diagnostic model outputs. The quantitative comparison shows that up to a 90% contribution to the innerregion updraft and a 55% contribution to the upper-layer outflow come from latent heating during Haima's (2004) TS stage. Up to a 90% contribution to the inner-region updraft and nearly a 100% contribution to the upper-layer outflow come from the upper-layer eddy angular momentum advection (EAMA) during Haima's (2004) EC stage. Representing the asymmetric structure of the storm, the predominantly positive contribution of the upper-layer EAMA to Haima's (2004) transformation is closely associated with the Sshaped westerlies in the upper layer with two jets. One jet in the cyclonic-curvature area carries cyclonic angular momentum into the storm, and the other jet in the anticyclonic-curvature area carries anticyclonic angular momentum out of the storm. Consequently, the newly-increased cyclonic tangential wind is deflected by the Coriolis force to the right to form the upper-layer outflow accompanied by the central-area rising motion, leading to Haima's (2004) extratropical transition after its landfall. © 2011 China National Committee for International Association of Meteorology and Atmospheric Sciences (IAMAS), Institute of Atmospheric Physics (IAP) and Science Press and Springer-Verlag Berlin Heidelberg.

Lu S.,Guangzhou Meteorological Observatory | Wu N.-G.,Guangzhou Meteorological Observatory
Journal of Tropical Meteorology | Year: 2010

The NCEP Global Data Assimilation System analysis of grid data, satellite products of Naval Research Laboratory, conventional meteorological data and observations of automatic weather stations in Guangdong province were used together with environmental conditions, atmospheric circulation, and physical characteristics to diagnose the cause and mechanism of the intensification of tropical cyclone Higos in Southern China. The results showed that favorable environmental conditions of high temperature, humidity of the underlying surface, strong upper divergence, weak vertical wind shear, and the persistence of a southwest jet stream beside the southern Higos were the necessary ingredients that contributed to the maintenance of intensity and re-intensification of Higos. The sinking intrusion of cold air from the lower troposphere was the critical condition for its intensification over land. The frontal genesis caused by weak cold air increased the lower tropospheric convergence and updraft, and the condensation latent heat released by heavy rains promoted convergence. From this positive feedback process, Higos obtained an increasing of positive vorticity and re-intensified over land. The re-intensification was due not only to the build-up of wind and the reduction of pressure but also to the simultaneous warm-up of its warm core.

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