Comparison of Precipitable Water Derived from Ground-Based GPS Measurements with Radiosonde Observations over the Korean Peninsula

Abstract

Precipitable water (PW) obtained from a permanent ground-based Global Positioning System (GPS) network on the Korean Peninsula was evaluated by using radiosonde measurements for two years. The GPS-derived PW is also validated using 5-min and 2-hourly troposphere products from International GNSS Service (IGS).The GPS-derived PW from our analysis and the IGS products were reasonably consistent with mean bias (Ours minus IGS products) of À0.27 mm and a standard deviation of 0.78 mm.The PW derived from radiosonde measurement (radiosonde PW) shows dry bias relative to GPSderived PW, where the mean bias (GPS minus radiosonde) is 1.50 mm with a standard deviation of 2.45 mm. We also found systematic bias in radiosonde PW depending on the radiosonde launch time. At the site with 6-hourly high temporal resolution soundings, the bias is greater during day (0900 and 15 LST) than at night (2100 and 0300 LST) with a difference of 1.34 mm in the maximum. In addition, our results show the dependency of error statistics on the absolute amount of PW and seasons. The bias increased for large amounts of PW especially in the daytime. Standard deviation tended to increase under humid conditions, but does not vary with observation time. The possible bias in GPS-derived PW caused by un-modeled phase center variation is also simulated in this study. Most phase observation errors are attributed to multi-path effects caused by the structure of monuments, where the errors are relatively small against the dry biases found in radiosonde PW.Our results addressed the accuracy of GPS-derived PW with reasonable quality and showed strong temporal and spatial variability of PW due to geographic location. These results suggest that GPSderived PW produced by the Korean regional GPS network has great potential to be used for various meteorological applications and could also contribute global GPS climatology.

Radiosonde Sensors Bias in Precipitable Water Vapor From Comparisons With Global Positioning System Measurements

“…It was also shown that the dry bias of radiosonde was greatly affected by the solar radiation (Wang et al 2002) and the main factors of the radiosonde bias were relative humidity in the atmosphere and the solar radiation depending on the elevation (Wang & Zhang 2008). In addition, Kwon et al (2007) showed that a radiosonde observation had a dry bias compared to a GPS observation and the PWV difference between those two observations increased especially in daytime.…”

Comparison of the Characteristics of Precipitable Water Vapor Measured by Global Positioning System and Microwave Radiometer

“…The observation values of radiosonde which has been used for the longest period of time are used often for verification, calibration and analysis of characteristics for values measured by other systems. For example, in a relative comparison with values measured by MWR, average difference from radiosonde results was represented as 1-5 mm, and standard deviation was represented as 1-2 mm (Westwater et al 1989, Liou et al 2001, Basili et al 2002, Pacione et al 2002, and in a relative comparison with values measured by GPS, average difference from radiosonde results was represented as 1-4 mm, and standard deviation was represented as 1-5 mm (Moon et al 1999, Kwon et al 2007.…”

Intercomparison between Temperature and Humidity Sensors of Radiosonde by Different Manufacturers in the ESSAY (Experiment on Snow Storms At Yeongdong) Campaign

“…기존의 라디오존데 오차 및 편차 비교 실험연구 결 과를 보면 습도의 경우 Global Positioning System (GPS) 가강수량과 비교했을 때 과소 측정(건조 편차) 하는 경향이 있는 데 (Wang et al, 2002;Turner et al, 2003;Nakamura et al, 2004;Wang and Zhang, 2008), 이는 수치모델의 가강수량을 과소 모의할 수 있다 (Lorence et al, 1996). 이러한 상대습도의 과소 관측 경향은 외국에 비해 활발하게 수행된 편은 아니 지만 국내 일부 연구결과에서도 확인된 바 있다 (Kwon et al, 2007;Kim et al, 2009 (1)…”