Mt Wilhelm Studies 2 The Climate of Mt Wilhelm RJ Hnatiuk JM B Smith D N Mcvean Mt Wilhelm Studies 2 TheRJ Hnatiuk Climate JM B Smith of DMt N Mcvean Wilhelm Research School of Pacific Studies Department of Biogeography & Geomorphology Publication BG/4 The Australian National University, Canberra Printed and Published in Australia at The Australian National University 1976 National Library of Australia Card No. and I.S.B.N. 0 7081 1335 4 © 1976 Australian National University This Book is copyright. Apart from any fair dealing for the purpose of private study, research, criticism, or review, as permitted under the Copyright Act, no part may be reproduced by any process without written permission . Printed at: SOCPAC Printery The Research Schools of Social Science and Pacific Studies H.C. Coombs Building, ANU Distributed for the Department by: The Australian National University Press The Climate of Mt Wilhelm PREFACE In 1966, the Australian National University with assistance from the Bernice P. Bishop Museum, Hawaii, established a field station beside the lower Pindaunde Lake at an altitude of 3480 m on the south- east flank of Mt Wilhelm, the highest point in Papua New Guinea. The field station has been used by a number of workers in the natural sciences, many of whose publications are referred to later in this work. The present volume arises from observations made by three botanists and their collaborators when members of the Department of Biogeography and Geomorphology, during the course of their work on Mt Wilhelm while based on the ANU field station. It is the second in the Departmental series describing the environment and biota of the mountain, and will be followed by others dealing with different aspects of its natural history. I am grateful to Dr Roger Barry of the Institute for Arctic and Alpine Research, Boulder, Colorado, for advice and careful reading of the manuscript. Nigel Wace ( Editor ) v CONTENTS Page LIST OF FIGURES ix LI ST OF PLATES xi LIST OF TABLES xi LIST OF APPENDIXES xi ii INTRODUCTION Equatorial mountain cl imates 1 Mt l�i lhelm 2 The regional cl imate on Mt Wil helm 3 The data 4 PRECIPITATION , RUNOFF AND EVAPOTRANSPIRATION Ra infall 11 Snow and hail 16 Runoff and lake level s 19 Evapotranspiration 20 Relative humidity and wind 22 RADIATION AND TEMPERATURE Radiation 27 Screen tempera tures 29 Temperatures near ground level 33 Topo thermal cl imates 35 Temperatures on slopes of different aspect 37 Soi l and lake temperatures 43 Frost and ice 43 COMPARISONS AND DISCUSSION The differen t val leys of Mt Wil helm 47 Comparison with other regions 48 Summary and conclusions 54 REFERENCES 57 APPENDIXES Summaries of Pindaunde meteorological data 61 vii LIST OF FIGURES Page 1. Maps of Mt Wi l helm and New Guinea ( facing ) 1 2. Map of Pindaunde val ley with meteorological sites 5 3 . ( a) Level of lower P indaunde Lake, 1972 14 (b) Daily rainfal l at Pindaunde, 1972 ( c) Daily rainfall at Kundiawa , 1972 4 . Typi cal actinograph traces 28 5. Thermoisopleth for Para , Brazil 30 6. Thermoisopleth fo r Framdrift expedi tion, North Polar Sea 30 7. Thermoisopleth for Pindaunde, 1.5 m 31 8. Thermoisopleth for Pangrango, Java 31 9. Thermoisopleth for El Misti , Peru 31 10. Thermoisopleth for Pindaunde, 0.2 m 36 11. Thermoisopleth for Upper Va11 ey , 0.5 m 36 12. Maximum and minimum temperatures on slopes of opposing aspect, Pindaunde 40 13. Max and min temperatures on slopes of opposing aspect on days with cloudy afternoons , Pindaunde 40 14 . Max and min temperatures on slopes of opposing aspect, 4020 m 41 15. Max and min temperatures on slopes of opposing aspect, 4380 m 41 16. Thermoisopleth from near Ridge Camp ( site 4) 51 17. Thermoisopleth for Macquarie Island 51 ix LIST OF PLATES Page 1. Kombuglomambuno (site 1) 8 2. Pindaunde valley showing position of research station (site 3) 8 3. Upper Guraguragugl valley 17 4. Snow on Mt Wil helm surrmit ridge as seen from fiel d station 17 5. Runoff after heavy rain 18 6. Install ation of evapotranspiration lysimeter, Pindaunde ( near site 3) 18 LIST OF TABLES 1 . Extent of Pindaunde meteorological records 6 2. Comparison between rai nfall at 3480 m and at 4380 m 12 3 . Annual rainfal l at places on and near Mt Wil helm 13 4. Rainfall and PET at Kombuglomambuno and Pindaunde 21 5. Summary of rel ative humidity records , Pindaunde, 1970 24 6 . Mt Wil helm, surrmary of temperature records (4400 m ) 34 7. Weekly temperatures at four sites of different aspect and topography , Mt Wilhelm 38 8. Climatic data for 8 equatorial mountain stations and Macquarie Island 49 9. Kotilainen 's Index of Oceanicity 53 xi LIST OF APPENDIXES Page 1. Mt Wil helm Climate Summary , 1965-72, Pindaunde Station 3480 3 61 m (site ) 2. Cl imate summary 1966, Pindaunde 62 3. Climate summary 1967, Pindaunde 63 4. Cl imate summary 1968, Pindaunde 64 5. Cl imate summary 1969, Pindaunde 65 6. Cl imate summary 1970, Pindaunde 66 7. Cl imate summary 1971-72, Pindaunde 67 8. 3480 1966 68 Pindaunde, m, temperature , oc, data for 9. 3480 1967 69 Pinda unde, m, temperature , oc, data for 10. 3480 1968 70 Pindaunde, m, temperature , oc, data fo r 11. 3480 1969 71 Pindaunde, m, temperature, oc, data for 12. 3480 1970 72 Pindaunde, m, temperature , oc, data for 13. 3480 1971 73 Pindaunde, m, temperature , oc, data for 14. 3480 1972 73 Pindaunde , m, tempera ture , oc, data for 15. Precipitation , mm , data for 1965-72 74 xiii MT WILHELM MT CARSTENZ National boundary 0 200 �Main range krlometres Forest l<OMANIMAMBUNO 2710m \ ', \ Keglsugl \ / airstrip _.., f N 2510m LJ Forest r1 \ .- Ridge '\'-' � I \I Cultivated \J land A Path \ ---- Unsealed road 0 • • • • • • • t Foot path kilometres �to GtJmb':t FIGURE 1. The Mt Wilhe lm region. Inset showing New Guinea with some major mountains and ranges . 1 INTRODUCTION Climatic data are few for equatorial mountains, largely because they are uncomfortable, economically unproductive , and usually uninhabited except at low altitudes . For most such mountains only short runs of records have been kept by expedition personnel , and con­ sistent records for periods of a year or more are rare . In Malesia such records are available for Mt Pangrango in Java (Braak 1923-25, summarized by van Steenis 1972; Troll 1961). Temperatu re data for South American mountainous areas (Oruro 3703 m in Bolivia, and El Mi sti 5850 m in Peru) are published by Troll (1959). EQUATORIAL MOUNTAIN CLIMATES Mountains exceeding 3000 m alti tude and lying wi thin ten degrees lati tude of the equator occur in Africa (East Afri ca , Ethiopia and Cameroon ) South America (the Andes mountains of Colombi a, Ecuador and north Peru ) and Mal esia (New Guinea, Sul awesi, Borneo, Java and Sumatra). Of these mountains , only those of East Afri ca, Ethiopia, the Andes and New Guinea belong to fairly extensive mountainous regions , the others bei ng isolated vol canic or plutonic peaks . Because of their height equatorial mountains have far colder cl imates than are normal in the tropics , but because of their latitude they experience no winter or summer, and in some cases virtually no seasons whatever. Their climates are comparable only wi th those of some oceanic isl ands of the temperate zones , for example Kerguelen and Macquarie Island . Herein lies one reason for their considerable bio­ logical interest, since they support biota which in many respects resemble those of temperate mountains and even arctic regions , but under quite different conditions. To describe such an environment as alp ine is, as Troll (1959) points out, misleading since it implies the exi stence of alternating winter and summer seasons the absence of which in equatorial mountains is a fact of considerable ecological importance. Equatorial mountain climates are geographically varied (and sometimes temporally variable) due mai nly to differences in total and seasonal precipitation, which are in turn affected by the interception of regional air movements by the mountains. Different mountains in the same region may be climati cally distinct, as has been emphasised for 2 a Java by van Steenis (1972), nd for the northern Andes by Lauer and others (1952). In New Guinea , Mt Carstensz probably has a wetter cl imate than Mt Wi lhelm to its east , whil e Mt Suckling further to the southeast is yet drier. Di fferent flanks of the same mountai n may differ markedly in precipitation and presumably also in cloudiness and radiation, as has been demonstrated by Coe (1967) for Mt Kenya, and Schmidt (1952) for the Columbian Andes. MT WILHELM Located at 504o•s; 145°11E, and 4510 m above sea level , the summit of Mt Wil helm marks the junction of the Bismarck Range ( running NW and ESE of the summit) and the Sepi k-Wahgi divide ( to the WNW), and is the highest point in Papua New Gui nea . Both the Bendenumbun valley ( by way of the Jimi , Yuat and Sepik Rivers) and Imbukum val ley ( by way of the Ramu River ) drain northwards to the Bismarck Sea . To the south several smaller valleys lead via the Chimbu and Wahgi rivers to the Purari and so to the Gulf of Papua. The most easterly of the southern vall eys is the Pindaunde, which provides the usual access route to Mt Wil helm and in which most of the meteorological data were coll ected ( Figure 1). Though a part of the Bismarck granodiorite, the rock of Mt Wil helm is better described as gabbro. Pleistocene glaciation has scoured steep val leys, often with lakes , and produced a rugged scenery.