WWOORRRLLLDDD INTERNATIONAL MEETTEEORROLLOGIICCAALL OCEANOGRAPHIC COMMISSION METEOROLOGICAL OORRRGGAAANNNIIIZZZAAATTTIIOIONNN OF UNESCO WORLD CLIMATE RESEARCH PROGRAMME BASELINE SURFACE RADIATION NETWORK (BSRN) Operations Manual Version 2.1 L.J.B. McArthur APRIL 2005 WCRP-121 WMO/TD-No. 1274 Acknowledgements The efforts required in creating any document far exceed the capabilities of any one person. This manual has been no exception. I would particularly like to thank the World Meteorological Organization for financial support during the initial drafting of this report and the Atmospheric Environment Service for providing me with the necessary time away from my regular duties to research the manual. I would also like to recognize the support of the International Council for Science and the International Oceanographic Commission of the UNESCO, the other sponsors of the World Climate Research Programme of which the Baseline Surface Radiation Network is part. The first draft was ably reviewed at the Boulder 1996 meeting of the BSRN. While all the participants at the meeting provided input I would especially like to thank the following individuals who acted as group leaders during that process: Klaus Dehne, Bruce Forgan, Roger Newson, Rolf Philipona and Tom Stoffel. Finally, I would like to thank Ellsworth Dutton as manager of the BSRN for his continuous encouragement throughout the production of this work. A number of individuals have graciously allowed manuscripts to be placed in the annexes for easy access. I would encourage readers, if they use these papers, to reference them directly to the original report or journal. I Preface to the First Edition Like all aspects of the Baseline Surface Radiation Network, this manual is in its infancy. The ideas contained within may be new to many, but have been applied successfully at various locations throughout the globe. On the one hand this indicates that these concepts should be considered seriously before being rejected, but on the other hand there may be some that are unworkable because of various climatic or operational factors. I would encourage all those using this manual not to reject any procedures without first carefully attempting to put them into operation. There is an anecdote within the meteorological community that must be overcome if the operation of the BSRN is to be successful. The question is asked, “How long does it take for a new instrument to be accepted as operational?” The answer, “One generation of meteorologists.” Let this not be the case within the BSRN! Some instructions or ideas within the manual may be unclear. If this is the case, I would appreciate having these reported to me as quickly as possible. I believe that everyone who has ever written step-by-step instructions has fallen into the trap of missing a step, or assuming too much. I would encourage scientists and technicians alike who use this manual to also apply “common sense” to the problem to overcome any omissions that I may have made. Although the WMO allowed me a significant amount of travel and opportunity to observe how various stations were operated, I am sure that excellent ideas have been missed within this first version of the manual, even with the significant help of those who reviewed it at the BSRN meeting in August 1996. Although only one person can place ideas on paper (or its virtual counterparts), the contents of this manual must remain a group effort if we are to build a radiation observing system of which we can be proud in our years of retirement. To this end I encourage new ideas be brought forward and new areas suggested for inclusion in the next revision. As paper gives way to electronic publications, the idea of editorial revisions has changed substantially over the last few years. Where once the second edition of a book might be expected a decade after the first printing, our expectations have increased to seeing something new on the WEB every day. It is hoped that minor revisions of the manual (clarifications etc.) can be put into place almost immediately and the revision number of the electronic version of the manual altered to reflect any changes. Major revisions (e.g. new sections) will obviously be less frequent, but will come out not only electronically, but also as a new printed manual. Finally, and again, this manual will improve with the feedback of the users. I urge anyone to contact me with any and all suggestions that might improve this manual.. Bruce McArthur Experimental Studies Division Atmospheric Environment Service 4905 Dufferin Street Downsview, Ontario, CANADA M3H 5T4 Telephone: 1 416 739 4464 Facsimile: 1 416 739 4281 Email: [email protected] II Preface to the Second Edition The World Climate Research Programme (WCRP) Baseline Surface Radiation Network (BSRN) has been operating as a network of surface radiation monitoring observatories for over 10 years. During this time period significant progress has been made in the measurement of various radiation quantities. Others have not progressed as rapidly. Observations of other quantities are now being requested by the user community. The process of improving measurements and the requirement for more information about the atmosphere and the radiation budget at the surface will continue indefinitely. The second edition of this manual recognizes the improvements that have been made during the time since the writing of the first edition. This is most evident in the inclusion of a chapter on the measurement of aerosol optical depth. Many advances that one would anticipate in a manual of this type have yet to be included, however, because questions remain about the veracity of these, they have not been left for a later addition until they prove themselves. In a number of cases, the thermal offset problem being the most notable, suggestions have been included in the hope that more research will proceed in these areas, especially in the various climatic regions of the network. Overall, the manual has been updated in a variety of places, rearranged where it was believed the flow could be improved and the Annexes that were considered dated removed. In turn, several new Annexes were included to provide the users of the manual more information on instruments and methods of observation. It is hoped that readers of this second version will find the overall presentation improved and therefore more useful. Bruce McArthur Experimental Studies Division Meteorological Service of Canada 4905 Dufferin Street Downsview, Ontario, CANADA M3H 5T4 Telephone: 1 416 739 4464 Facsimile: 1 416 739 4281 Email: [email protected] III Table of Contents Acknowledgements...................................................................... I Preface to the First Edition ................................................................ II Preface to the Second Edition ............................................................ III 1.0 Introduction......................................................................1 1.1 Overall goals and purpose of the BSRN ........................................2 1.2 Purpose and scope of the operations manual . 3 1.3 Specific objectives and research activities . 5 2.0 Sampling Frequency and Accuracy Requirements for BSRN Stations . 8 2.1 Sampling Frequency .......................................................8 2.1.1 Sampling Frequency of Radiation Measurements . 8 2.1.2 Sampling Frequency of Ancillary Measurements . 9 2.2 Uncertainty of Measurements ................................................9 2.2.1 Uncertainty in Radiation Measurements . 9 2.2.1.1 Direct Solar Irradiance ........................................9 2.2.1.2 Diffuse Radiation ............................................11 2.2.1.3 Global Radiation ............................................12 2.2.1.4 Reflected Solar Radiation.....................................12 2.2.1.5 Downwelling Infrared Radiation . 12 2.2.1.6 Upwelling Infrared Radiation ..................................13 2.2.2 Accuracy of Meteorological Measurements . 13 2.3 Accuracy of Data Acquisition Equipment ......................................13 2.3.1 Time......................................................13 2.3.2 Data Acquisition System Accuracy ....................................15 3.0 The BSRN Site..................................................................16 3.1 Geographic Location of Site ................................................16 3.1.1 General Considerations .............................................16 3.1.2 Horizon ..........................................................17 3.1.3 Latitude, Longitude, Elevation ........................................17 3.1.4 General site description for the Archive . 18 3.2. BSRN Station Information Document .........................................18 3.2.1 General Description ................................................19 3.2.2 Site Description....................................................19 3.2.3 Station Description .................................................19 3.3 Instrument Exposure ......................................................21 3.4. Additional Station Requirements .............................................21 3.4.1 Ease of Access ....................................................21 3.4.2 Electrical Power ...................................................21 3.4.3 Communication ...................................................22 3.4.4 Security ..........................................................24 3.5 Site Preparation ..........................................................24