Xuan Yuejian

Development of Cloud Detection Methods Using CFH, GTS1, and RS80 Radiosondes

The accuracies of three instruments in measuring atmospheric column humidity were assessed during an upper troposphere and lower stratosphere observation campaign conducted from 7 to 13 August 2009 in Kunming, China. The three instruments are a cryogenic frost-point hygrometer (CFH), a Vaisala RS80 radiosonde (RS80), and a GTS1 radiosonde (GTS1). The accuracy of relative humidity (RH) measurements made by the CFH, GTS1, and RS80 was similar between the surface and 500 hPa (∼5.5 km above sea level). However, above 500 hPa, the errors in RH measurements made by the RS80, relative to measurements made by the CFH, are much less than those detected with the GTS1. Three different retrieval methods for determining cloud boundaries from CFH, RS80, and GTS1 measurements were developed and take into account the differences in accuracy among the three instruments. The method for the CFH is based on RH thresholds at all levels, which demands high accuracy. Given that the accuracy of RH measurements decreases at higher altitudes, the cloud detection methods for RS80 and GTS1 are different for different altitude ranges. Below 5 km, the methods for the RS80 and the GTS1 are similar to that of the CFH; above 5 km, the methods for the RS80 and the GTS1 are both developed based on the second-order derivatives of temperature and RH with respect to height, but with different criteria applied. Comparisons of cloud-layer retrievals derived from the three measurements are also made.

Performance Evaluation of a Self-Developed Ozonesonde and Its Application in an Intensive Observational Campaign

Abstract To make a detailed test on the reliability and detection performance of the electrochemical concentration cell (ECC) type ozonesonde which had been developed and preliminarily evaluated by the authors, an intensive ozonesonde release experiment was held at two sites in Beijing and Changchun in June 2013. The results showed that the mean background current and its standard deviation were 0.03 (0.04) μA and 0.02 (0.03) μA in Beijing (Changchun). The average response time and its standard deviation were 27.8 s (30.4 s) and 4.0 s (3.7 s) in Beijing (Changchun). The ozone partial pressure profiles at both sites showed a central peak in the stratosphere and a side peak in the boundary layer. Large variation in ozone partial pressure was observed at the middle levels of the atmosphere (10–17 km). A more marked gradient of ozone change was observed in Beijing (3.4 mPa kmࢤ1) at the lower atmosphere level, as compared to that in Changchun (0.4 mPa kmࢤ1). The results presented in this paper indicate that this self-developed ozonesonde shows a high level of reliability and good performance. The ozonsonde is expected to play an important role in operational observations of ozone profiles.

An Optical Disdrometer for Measuring Present Weather Parameters

Abstract A new present weather identifier (PWI) based on occlusion and scattering techniques is presented in the study. The present weather parameters are detectable by the meteorological optical range (MOR) approximately up to 50 km and by droplets with diameters ranging from 0.125 mm to 22 mm with velocities up to 16 m s−1. The MOR error is less than 8% for the MOR within 10 km and less than 15% for farther distances. Moreover, the size errors derived from various positions of the light sheet by the particles were checked within ± 0.1 mm ± 5%. The comparison shows that the MOR, in a sudden shower event, is surprisingly consistent with those of the sentry visibility sensors (SVS) with a correlation coefficient up to 98%. For the rain amounts derived from the size and velocity of the droplets, the daily sums by the PWI agree within 10% of those by the Total Rain Weighing Sensor (TRwS205) and the rain gauge. Combined with other sensors such as temperature, humidity, and wind, the PWI can serve as a present weather sensor to distinguish several weather types such as fog, haze, mist, rain, hail, and drizzle.

国产ECC型O 3 探空仪性能测试及室外比对观测

该文介绍了中国科学院大气物理研究所（简称IAP）研制的电化学浓度电池（ECC）型臭氧（O3）探空仪基本性能测试和2013年上半年室外比对观测结果。结果表明：ECC的背景电流（Ibg）在0.1 μA以下或更低；测量O3的响应时间为21~26 s；NO2（SO2）使O3测值偏高（低）；抽气泵低压泵效系数（Cef）在100 hPa高度以下为1.0左右，在该高度以上上升，10 hPa达到1.17±0.10，5 hPa达到1.28±0.16，性能略低于同类进口产品（1.055以下）。国产和进口仪器在气象探空或抽气泵等部件上具有良好兼容性；两者所测O3垂直分布廓线总体一致。IAP O3探空仪O3总量与Brewer光谱仪测值比值为0.9~1.1；Cef和Ibg订正有效降低了IAP O3探空仪在平流层低层与进口仪器测值的差别，这一订正对O3柱浓度在平流层和对流层的贡献分别为约15 DU和4~6 DU；在对流层，IAP O3探空仪测值与进口仪器间的绝对差别稳定且低于0.5 mPa；而平流层受泵效影响较明显。因此，建议IAP O3探空仪提高其Cef的稳定性，参与国际比对测试，国产气象探空平台数据接收处理增加必要的滤波技术以降低平流层探测数据（包括O3）的振荡。