| In order to obtain more accurate cloud vertical structure and its evolution process,the observation of millimeter-wave radar has been one of the important way of cloud and precipitation research in recent years.Compare with traditional weather radar,millimeter wave are more sensitive to the detection of smaller particles due to its short wavelength.In this paper,the dual-frequency cloud radars,a W-band cloud radar and a Ka-band cloud radar,were first involved in the observation of APSOS system at Yangbajing Tibet site,and used to study the cloud parameters,including cloud macroscopic parameters and cloud water content,in addition,making full use of the unique advantages that CloudSat satellite W-band cloud radar transits Yangbajing area,to achieve the comparative analysis of space-borne and ground-based cloud radars.The main contents and conclusions are as follows:(1)Because millimeter wave is greatly affected by the attenuation caused by precipitation,the research object in this paper is non-precipitation cloud echo.First of all,Using the data observed continuously by W-band radar at Yangbajing Tibet site from December 2017 to February 2018,including the cloud base height and the cloud top height,cloud thickness and the ice water content.The results show that the main cloud type of the winter cloud is the middle and low level thin cloud at Yangbajing Tibet site,most of them are within 2~5km,the cloud thickness is between 0.3km and 2km,the cloud parameters have significant daily variations.the time of 10:00 BJT to 12:00 BJT is the period that has the lowest frequency of the cloud occurrence,and another time of02:00 BJT to 08:00 BJT is the one that has the most frequency;after the local sunrise time,it mostly appeared as thin clouds;the cloud base and top height both decrease first and then increase at the noon hour,the cloud base and cloud top height have been lifted,later sunset time,the cloud heights and the cloud thickness vary slightly;at the same time,a certain distribution of high clouds,emerge at 6km at the vertical direction mainly in the early morning;ice water content IWC was retrieval by using the method of many previous experience formulas,the result shows that IWC is mainly concentrated in the range of 0.01~0.04g?m ~3,the peak is around 0.01g?m~3.(2)This paper not only makes the statistical analysis of single cloud radar data,also compare two aspects,one is between the Ka-band and the W-band cloud radar,another is between space-borne and ground base cloud radars.From three cases analyses of a low cloud,a middle thick cloud and high cloud by this two wave cloud radar,and a preliminary discussion of the synchronous joint observation of space-borne and ground base cloud radars,it can be concluded that they can implement the detection of cloud macroscopic parameters and the preliminary retrieval of water contents in the cloud,which has great consistency and feasibility,but the strength of the detection ability is related to the cloud layer height and its thickness.The cause may be that due to the shorter wavelength of the millimeter wave,the attenuation increases,caused by the atmosphere and the cloud,as the detection altitude increases.In addition,the W-band cloud radar used in this paper is in the development period,the hardware performance may be not ideal,but in general,it has more far-reaching significance for the further preparation of plateau cloud and precipitation mechanism,the parametric study of cloud micro-physical process and multiple remote sensing facilities joint observation. |
PDF Full Text Request