Vaisala Radiosonde RS41 Measurement Performance WHITE PAPER WEA-MET-RS41-Performance-White-paper-B211356EN-B.indd 1 19.10.2017 11.10 WEA-MET-RS41-Performance-White-paper-B211356EN-B.indd 2 19.10.2017 11.10 Table of Contents CHAPTER 1 1.1 Executive summary...................................................................................................................... 5 1.2 How the Vaisala Radiosonde RS41-SG measurement accuracy specifications are derived................ 6 CHAPTER 2 Temperature Measurement .......................................................................................................................... 7 2.1 Specifications .............................................................................................................................. 7 2.2 Temperature measurement performance after ground preparation ............................................... 7 2.3 Temperature measurement performance in sounding ................................................................... 9 CHAPTER 3 Humidity Measurement ...............................................................................................................................13 3.1 Specifications .............................................................................................................................13 3.2 Humidity measurement performance after ground preparation ....................................................13 3.3 Humidity measurement performance in sounding ........................................................................15 CHAPTER 4 Geopotential Height Measurement ...............................................................................................................18 4.1 Specifications .............................................................................................................................18 4.2 Geopotential height measurement performance in sounding ........................................................18 CHAPTER 5 Pressure Measurement ................................................................................................................................21 5.1 Specifications .............................................................................................................................21 5.2 GPS-derived pressure measurement performance in sounding .................................................... 22 CHAPTER 6 Wind Measurement .................................................................................................................................... 23 6.1 Specifications ............................................................................................................................ 23 6.2 Wind measurement performance at ground level ........................................................................ 23 6.3 Wind measurement performance in sounding ............................................................................. 24 CHAPTER 7 Data Continuity .......................................................................................................................................... 25 7.1 Data continuity following the replacement of RS92 with RS41 ....................................................... 25 7.2 Data continuity with RS41 in operational use ............................................................................... 25 APPENDIX I Definitions of terms related to measurement performance analysis .............................................................. 26 APPENDIX II Standards and recommendations ............................................................................................................... 27 References ................................................................................................................................................. 28 3 WEA-MET-RS41-Performance-White-paper-B211356EN-B.indd 3 19.10.2017 11.10 CHAPTER 1 The purpose of this document is to present the measurement performance of the Vaisala Radiosonde RS41. The Vaisala Radiosonde RS41 responsive yet highly reproducible phase. Comparison results against introduces improvements in in all atmospheric conditions. applicable reference instruments accuracy and consistency of are also included. The Vaisala The Vaisala Radiosonde RS41 fulfills upper air measurement data. Radiosonde RS41 and Vaisala all recommendations for radiosonde Each technical solution of RS41, Radiosonde RS92 are compared accuracy detailed in Annex 12.A from the state-of-the-art sensor in detail in the Comparison of of the current version of the WMO technology to the highly automated Vaisala Radiosondes RS41 and RS92 Guide to Meteorological Instruments manufacturing process, has been White Paper [2]. RS41 pressure and Methods of Observation [1] carefully planned and thoroughly measurement technologies tested. This, together with extensive This document presents a are reviewed in more detail in quality control – applied all the technical assessment of the separate white papers: GPS-based way from the manufacturing stage measurement performance of Measurement of Height and to the sounding preparation and the Vaisala Radiosonde RS41-SG, Pressure with Vaisala Radiosonde the sounding process – results -SGP, and, -SGM. The assessment RS41 [3], and, Vaisala Radiosonde in excellent measurement covers measurement uncertainty RS41-SGP Pressure Measurement performance. In practice this analysis as well as results from Performance [4]. is demonstrated in upper air sounding campaigns carried out measurements that are extremely during the product development 4 WEA-MET-RS41-Performance-White-paper-B211356EN-B.indd 4 19.10.2017 11.10 1.1 Executive summary In terms of measurement • GPS-based height, atmospheric correction. As this correction is performance, the key characteristics pressure, and wind measurements based on sensor heating, it does of the Vaisala Radiosonde RS41 use customized signal processing not require desiccant-based zero are its excellent repeatability and algorithms developed by Vaisala. RH conditions. reliability in all sounding conditions. These algorithms are optimized • The user interface of the Vaisala for sounding applications, taking A number of factors contribute to DigiCORA® Sounding System into account such factors as this high-level performance. The MW41, as well as the functionality typical radiosonde motion. first of these is the state-of-the-art of the RS41 and the ground check sensor technology and advanced In addition to the sophisticated device, are designed to be user correction methods used in the measurement technologies friendly and to minimize the RS41: highlighted above, three other risk of human error. As a result, important factors help ensure high- the Vaisala fourth-generation • The temperature sensor is quality sounding data: sounding system is efficient to tailored for sounding applications. operate and delivers consistent It is based on platinum resistor • Extensive quality control results. technology, which gives reference- is deployed throughout the class linearity and stability. In manufacturing and calibration Over one thousand test soundings, sounding conditions the excellent processes. The final quality numerous laboratory tests, and in- measurement accuracy is a result assurance checks before launch depth uncertainty analysis carried of optimized sensor design and are done automatically during out during the product development thoroughly verified radiation sounding preparation. phase have demonstrated that the correction. Vaisala Radiosonde RS41 takes • Basically, if corrections are made sounding data quality to a whole • The humidity sensor chip in conjunction with sounding new level. combines a capacitive polymer preparation, the references on sensor with a temperature which the corrections are based sensor and a heating element. must be carefully maintained. This enables accurate, ice-free For the RS41, the only correction humidity measurement in clouds applied in the preparation and in varying solar radiation phase is physical zero humidity exposures. RS41 specification P T U (hPa) (°C) (%RH) Uncertainty after ground preparation N/A 0.2 3 Uncertainty in sounding >100 hPa 1.0 100 ... 10 hPa 0.3 <10 hPa 0.04 <16 km 0.3 4 >16 km 0.4 4 Reproducibility in sounding >100 hPa 0.5 0.15 2 100...10 hPa 0.2 0.30 2 <10 hPa 0.04 0.30 2 Table 1.1. Key measurement performance figures for the Vaisala Radiosonde RS41. For detailed specifications, see Table 2.1, 3.1, 4.1, 5.1, and 6.1. 5 WEA-MET-RS41-Performance-White-paper-B211356EN-B.indd 5 19.10.2017 11.10 1.2 How the Vaisala Radiosonde RS41-SG measurement accuracy specifications are derived During the development of the The uncertainty analysis is • The combined uncertainty for Vaisala Radiosonde RS41, a wide implemented following the the measurand is determined range of laboratory tests and over recommendations of JCGM 100:2008 by calculating the effect of each one thousand comparative test [5]. In short, the uncertainty uncertainty component on the soundings were conducted. These analysis consists of the following end result. This is based on the results served as input data for a steps (adapted from the guide): mathematical model created in comprehensive uncertainty analysis the first step and the general rules • The relationship between the that was carried out in order to for combining uncertainties. measurand and all the input estimate measurement uncertainties quantities are expressed The calibration uncertainty is in a wide range of atmospheric