| Tropical cyclones(TCs)are destructive weather systems that can generate severe natural disasters in many coastal areas.The TCs occurring in the Northwest Pacific Ocean account for more than 36%in the globe.Researches of the cloud parameters,precipitation and latent heating(LH)in this area help to improve our understandings of typhoon generation,evolution and dissipation.Furthermore,these studies provide an observational foundation for the simulation of cloud-to-precipitation transitions in models,thereby improving the capability to predict the track and intensity of TCs.In this thesis,on the basis of cloud parameters retrieval and cross-comparison of various parameters,we used the Tropical Rainfall Measurement Mission(TRMM),Global Precipitation Measurement(GPM)and other platforms observations,as well as combined with the historical typhoon information provided by Japan Aerospace Exploration Agency(JAXA)and China Meteorological Administration(CMA),to analyze the distribution characteristics and indicate relationships between cloud water path(CWP)and near-surface rain rate(RR)of TCs.Evolutions over the life cycle of TCs and the relationships between RR and LH were further studied.The main innovations and conclusions of this thesis are listed as follows.1.The quality of CWP retrieved by Bispectral reflectance(BSR)algorithm,RR and LH estimated by Precipitation Radar were evaluated through the cross-comparison of multi-source observations and the spatial-temporal matching between parameters.Cloud microphysical parameters retrieved by Visible and Infrared Scanner(VIRS)onboard the TRMM satellite through BSR method were compared with the cloud products of Moderate Resolution Imaging Spectroradiometer(MODIS)onboard the Aqua satellite.The results showed that the correlation coefficient of CWP was 0.88.On the basis of spatial-temporal matching,RR retrieved by GPM/KuPR was compared by ground-based rain gauge and S-band Doppler radar.The results showed that the precipitation pixels detected by rain gauge and KuPR was almost consistent,and the reflectivity factor displayed by ground-based S-band Doppler radar agreed well with the precipitation distributions detected by KuPR.The LH products released by GPM in typhoon large-scale system were evaluated.It was found that there were differences in the maximum value and height of convective LH between 2HSLH and 2HCSH products.Furthermore,we confirmed that reasonable information could be achieved by analyzing the vertical and average properties of LH.2.The distribution characteristics and relationships between CWP and RR of TCs were revealed by the calculation and analysis of TRMM merged datasets.We combined time-and-space-synchronized precipitation and spectral data obtained by the Precipitation Radar(PR)as well as VIRS onboard the TRMM satellite,to overcome the limitations of precipitation properties and cloud parameters not being synchronized in previous studies.A merged dataset of RR and corresponding CWP was established to analyze the potential correlations between cloud microphysical properties and precipitation.25 collocated satellite overpasses of TCs in the Northwest Pacific Ocean from 1998 to 2012(15 years)were obtained to analyze the characteristics of the CWP and RR of 144 515 pixels in detail.The results showed that CWP increased with RR for light-middle precipitation,while changed little for heavy precipitation,indicating that cloud water content ultimately tended to saturation.CWP and RR of TCs with different precipitation types,precipitation cloud phases,and vertical depths of precipitation can be fitted by a notable sigmoid function,which is useful for estimating CWP and parameterizing precipitation in models.Furthermore,the relationship was applied and tested for an independent sample,showing that RR was a significant indicator of CWP.3.Characteristics of cloud parameters,precipitation and latent heating in the whole life cycle evolution process of Typhoon "Halong" were analyzed by GPM datasets.According to the 2-min average maximum wind speed near the typhoon center,the life cycle of Typhoon "Halong" was divided into developing stage,mature stage and decaying stage.Using the precipitation and latent heating products retrieved by GPM,as well as cloud top parameters from MODIS,the evolution characteristics of cloud,precipitation and latent heating structures during the whole life cycle of Typhoon"Halong" were analyzed.With the development of Typhoon "Halong",cloud top height first increases and then decreases,while storm top height was highest in the developing stage.This is closely related to the difference in the leading role of motivation and thermal factor for different life cycle of TCs.With the maturity of typhoon,cloud and rain particles gather towards the center of the typhoon eyewall,and the particle spectrum concentration around the eye area increases.The mechanism is the strong convergence in mature stage.RR and column average of latent heating(CLH)in decaying stage were weaker than those in developing and mature stages,indicating that upward movements and phase changes were both weakened in this period.4.Using typical TCs in the Northwest Pacific Ocean observed by GPM from 2014 to 2019,the synthetic analysis method was used to study the characteristics and relationships between precipitation and latent heating in different life stages of TCs.The proportion of convective precipitation was the highest in the developing stage,but the average RR was the largest in the mature stage,mainly because the liquid water content was sufficient for mature stage,which was more conducive to precipitation.The average RR and CLH in each life stage decreased continuously along the radial direction to outside,and the precipitation probability was the highest in the inner spiral rain belt.RR and CLH in mature stage were the largest within the eyewall.There were differences in precipitation intensity profiles in different life stages.To be specific,the precipitation rate in mature stage was the largest,followed by developing stage at the same height.Statistically determined that the CLH of convective and deep stratiform precipitation in TCs can be estimated by a double-logarithm function of RR,which passed the test and application of independent samples.It provided a new method to quantitatively estimate the CLH of TCs. |
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