GTS1 digital radiosonde, developed by the Shanghai Changwang Meteorological Science and Technology Company in 1998, is now widely used in operational radiosonde stations in China. A preliminary comparison of simultane...GTS1 digital radiosonde, developed by the Shanghai Changwang Meteorological Science and Technology Company in 1998, is now widely used in operational radiosonde stations in China. A preliminary comparison of simultaneous humidity measurements by the GTS1 radiosonde, the Vaisala RS80 radiosonde, and the Cryogenic Frostpoint Hygrometer （CFH）, launched at Kunming in August 2009, reveals a large dry bias produced by the GTS1 humidity sensor. The average relative dry bias is in the order of 10% below 500 hPa, increasing rapidly to 30% above 500 hPa, and up to 55% at 310 hPa. A much larger dry bias is observed in the daytime, and this daytime effect increases with altitude. The GTS1 radiosonde fails to respond to humidity changes in the upper troposphere, and sometimes even in the middle troposphere. The failure of GTS1 in the middle and upper troposphere will result in significant artificial humidity shifts in radiosonde climate records at stations in China where a transition from mechanical to digital radiosondes has occurred. A comparison of simultaneous temperature observations by the GTS1 radiosonde and the Vaisala RS80 radiosonde suggests that these two radiosondes provide highly reproducible temperature measurements in the troposphere, but produce opposite biases for daytime and nighttime measurements in the stratosphere. In the stratosphere, the GTS1 shows a warm bias （〈0.5 K） in the daytime and a relatively large cool bias （-0.2 K to -1.6 K） at nighttime.展开更多
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 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.展开更多
基金supported by the CAS Knowledge Innovation Project (Grant No KZCX22-YW-207)the National Basic Research Program of China (Grant No 2010CB428602)the National Natural Science Foundation of China (Grant Nos 40830102 and 40775030)
文摘GTS1 digital radiosonde, developed by the Shanghai Changwang Meteorological Science and Technology Company in 1998, is now widely used in operational radiosonde stations in China. A preliminary comparison of simultaneous humidity measurements by the GTS1 radiosonde, the Vaisala RS80 radiosonde, and the Cryogenic Frostpoint Hygrometer （CFH）, launched at Kunming in August 2009, reveals a large dry bias produced by the GTS1 humidity sensor. The average relative dry bias is in the order of 10% below 500 hPa, increasing rapidly to 30% above 500 hPa, and up to 55% at 310 hPa. A much larger dry bias is observed in the daytime, and this daytime effect increases with altitude. The GTS1 radiosonde fails to respond to humidity changes in the upper troposphere, and sometimes even in the middle troposphere. The failure of GTS1 in the middle and upper troposphere will result in significant artificial humidity shifts in radiosonde climate records at stations in China where a transition from mechanical to digital radiosondes has occurred. A comparison of simultaneous temperature observations by the GTS1 radiosonde and the Vaisala RS80 radiosonde suggests that these two radiosondes provide highly reproducible temperature measurements in the troposphere, but produce opposite biases for daytime and nighttime measurements in the stratosphere. In the stratosphere, the GTS1 shows a warm bias （〈0.5 K） in the daytime and a relatively large cool bias （-0.2 K to -1.6 K） at nighttime.
基金supported by National Natural Science Foundation of China (GrantNo 40830102)the program "The Multi-scale Comprehensive Observation and Study of Spatial-Temporal Properties of Aerosol Project (MOSTap)" of National Basic Research Program of China (973 Program Grant No 2010CB950804)
文摘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.
