New Tools for Climate Measurement - the Vaisala Climate Reference Radiosonde Program

Transcription

1 New Tools for Climate Measurement - the Vaisala Climate Reference Radiosonde Program Presentation in the 23rd Conference on Climate Variability and Change Seattle, WA, 26 January 2011 Heikki Turtiainen, Hannu Jauhiainen, Terhi Lehtola, Johanna Lentonen, Ari Paukkunen, Petteri Survo, Markus Turunen, Veli-Pekka Viitanen, Hans von Bagh Vaisala Oyj, Helsinki, Finland Walter F. Dabberdt Vaisala Inc, Boulder, Colorado

2 Presentation Outline 1. Background Importance of reliable upper-air observations in climate science 2. Towards Better Climate Observations Global Climate Observation System (GCOS) GCOS Reference Upper-Air Network (GRUAN) 3. How Can an Instrument Manufacturer Contribute to Climate Research? - The Vaisala Reference Radiosonde Program Program objectives Improving the radiosonde performance Analyzing the measurement uncertainty of radiosonde observations Ensuring Data Continuity through metadata management Developing reference grade radiosonde Next steps Page 2 / Vaisala

3 1 Background Page 3 / Vaisala

4 Important decisions with vast economic implications rely on the accuracy of climate observations Assessing climate change depends crucially on the reliability of long-term atmospheric data sets. The bulk of atmospheric observations have been made for the purpose of short term weather forecasting. They very often lack the accuracy, continuity, homogeneity and representativeness required for longterm climate studies. Especially historical upper-air records of important climate variables most importantly temperature and humidity of upper troposphere and stratosphere - fail to fulfill these requirements. Page 4 / Vaisala

5 Both in-situ and remote sensing upperair datasets suffer from inhomegeneities and lack of continuity Complex inter-sensor biases exist between satellite instruments. Datasets of operational upper-air soundings with radiosondes have been particularly affected because of Poor sensor performance in the past Numerous and insufficiently documented changes in instruments and procedures Difficulties in estimating measurement uncertainties of the instruments. As a consequence, for example tropospheric water vapour trends, a key determinant of climate sensitivity to greenhouse gas forcing, are poorly known. Page 5 / Vaisala

6 2 Towards Better Climate Measurements Page 6 / Vaisala

7 The Global Climate Observing System (GCOS) is being built in order to provide continuous, reliable, comprehensive information on the state and behaviour of the global climate system GCOS is an internationally coordinated system, consisting of the climate relevant components of all established environmental observing networks and systems. It is co-sponsored by the World Meteorological Organization (WMO) Intergovernmental Oceanographic Commission (IOC) of UNESCO United Nations Environment Programme (UNEP) International Council for Science (ICSU). Page 7 / Vaisala

8 The GCOS Reference Upper Air Network (GRUAN) is a key component of the GCOS The current upper-air measurement network does not satisfy the requirements for climate observations. Therefore, in 2007, GCOS laid out the need for a GCOS Global Reference Upper-Air Network, or GRUAN (Seidel, 2009). The Initial GRUAN Stations The overall goal of GRUAN is to establish stations that will use reference grade radiosondes in addition to other instrumentation to represent climate around the world. The Deutscher Wetterdienst's Lindenberg Observatory is the GRUAN Lead Center, providing scientific leadership, managing the network and data archival, and ensuring free dissemination. Page 8 / Vaisala

9 The GCOS three-tiered upper air observing system architecture (Seidel, 2009) Page 9 / Vaisala

10 3 How Can an Instrument Manufacturer Contribute to Climate Research? - The Vaisala Climate Reference Radiosonde Program Page 10 / Vaisala

11 How can an instrument manufacturer contribute to climate research? As part of its corporate social responsibility commitment, Vaisala is making important contributions to the climate data challenge by providing the best possible tools for the meteorological community. improving the accuracy of instruments and analyzing their measurement uncertainty documenting all changes in instrument design, procedures and related software developing new reference grade instruments The development is done in close collaboration with the international scientific community. Page 11 / Vaisala

12 How can an instrument manufacturer contribute to climate research? Analyze the uncertainty budgets of your instruments - and make them public Example: Specifications of the RS92 Radiosonde Temperature Sensor * 2-sigma (k=2) confidence level (95.5 %), cumulative uncertainty including Repeatability Long-term stability Effects due to measurement conditions Dynamic effects (such as response time) Effects due to measurement electronics ** Standard deviation of differences between two successive calibrations, k=2 confidence level *** Standard deviation of differences in twin soundings Type: capacitive wire Measurement range +60 C to -90 C Response time (63.2%, 6 m/s flow) 1000 hpa < 0.4 s 100 hpa < 1 s 10 hpa < 2.5 s Resolution 0.1 C Accuracy Total uncertainty in sounding* 0.5 C Repeatability in calibration** 0.15 C Reproducibility in sounding*** hpa 0.2 C hpa 0.3 C 20-3 hpa 0.5 C Page 12 / Vaisala

13 How can an instrument manufacturer contribute to climate research? Continuosly improve the accuracy of your instruments based on feedback from the scientific community Example: Recent improvements of the RS92 Radiosonde performance Humidity measurement algorithm has been improved to take into account the sensor's response time and heating by solar radiation. Minor adjustments for the RS92 radiation correction table have been made. In addition to solar radiation, the correction algorithm now takes better into account the sensor ventilation during the flight. The new algorithms were verified in the WMO Yangjiang Radiosonde Intercomparison, July 2010, and taken into use in the sounding software update in December Page 13 / Vaisala

14 How can an instrument manufacturer contribute to climate research? Ensure Data Continuity through Metadata Management: Document and publish all changes in sensor design, procedures and related software An excerpt from the RS92 Data Continuity web pages documenting the RS92 sounding software and algorithm changes. Links provide detailed description and test data on the influence of the changes. Page 16 / Vaisala

15 How can an instrument manufacturer contribute to climate research? Develop new reference grade instruments In January 2009 Vaisala launched a program to develop an operational reference-grade radiosonde for climate studies and other applications where enhanced radiosonde performance is required (especially the GRUAN network). The program will concentrate first on upperair measurements of humidity, the most abundant and most important greenhouse gas in the earth's atmosphere. The first version of the operational reference radiosonde uses a new advanced capacitive DRYCAP humidity sensor. Page 17 / Vaisala

16 RR01: the first prototype of the Reference Radiosonde Goal: easy to use, reasonable cost reference grade sonde to enable frequent, operational climatological soundings. DRYCAP humidity sensor for upper tropospheric and stratospheric humidity measurements RS92 sensors for pressure, temperature and tropospheric humidity RS92 GPS wind finding Page 18 / Vaisala

17 Sounding example: December 2010, Sodankylä. Two RR01 sondes with CFH as a reference RR01 has been field tested against Altitude [m] CFH RR01 #14 RR01 #17 T_ambient Tfp [ C] the Cryogenic Frostpoint Hygrometer (CFH). In the tests RR01 has demostrated consistent performance and excellent repeatability. However, two technical challenges remain to be solved: A systematic bias of degc frost point is observed against CFH. In very humid conditions (rain, fog, condensing conditions) large measurement errors occur. Suspected reason is "moisture contamination": wetting or condensation, and consequent formation of ice on the sensor shield or nearby surfaces in the lower atmosphere. In the stratosphere, the accumulated ice begins to evaporate, causing observation error. Page 20 / Vaisala

18 How can an instrument manufacturer contribute to climate research? Make it easy to interface additional sensors to your measurement system RS92 Add-On Interface makes it possible to connect user's own sensors to the sonde. Technical details and the message protocol of RS92 interface are being made public so that all interested can interface their sensors. Vaisala RSA921 interface for Ozone Sensor can be used to connect any sensor with 1 or 2 analog outputs to the RS92 radiosonde. Page 21 / Vaisala

19 Next Steps Continue the development of RR01 towards an operational reference grade radiosonde Find and eliminate the reason for the Drycap CFH bias Improve performance in conditions with humid lower troposhere to achieve all-weather capability Develop volume manufacturing capability for RR01 Refine the measurement uncertainty analysis for radiosondes The GRUAN stations will need uncertainty estimates for each individual data point Page 22 / Vaisala

20 The Vaisala Climate Reference Radiosonde Program Program launch AMS 2009 Status report AMS 2010 Status report AMS 2011 Phase A First prototype of the Reference Radiosonde: RR01 Status report 2012 appr. 5 years OPERATIONAL REFERENCE RADIOSONDE Phase C Improved performance Regular RR01 soundings by pilot customers Phase B DRYCAP sensor module further development Improved RS92 Humidity and Temperature algorithms Metadata Management & Public Data Continuity web pages Thank You! Page 23 / Vaisala

21 References Report on the WMO-BIPM Workshop on Measurement Challenges for Global Observation Systems for Climate Change Monitoring. WMO/TD No. 1557, Seidel, D. et al., Reference Upper-Air Observations for Climate: Rationale, Progress, and Plans. Bulletin of the American Meteorological Society, March Implementation Plan for the Global Climate Observing System reference Upper Air network WMO/TD No. 1506, July 2009 Immler, F. J.; Dykema, J.; Gardiner, T.; Whiteman, D. N.; Thorne, P. W. and Vömel, H., Reference Quality Upper-Air Measurements: guidance for developing GRUAN data products. Atmospheric Measurement Techniques, 2010, 3, Dabberdt, W. F. et. al., Climate Monitoring and Research - Vaisala Contributes to Earth's Climate Knowledge. Vaisala White Paper, Page 24 / Vaisala