Effects of Extreme Drought on Vegetation of a Lava Flow on Mauna Loa, Hawai'i

Effects of an extreme drought were examined along an elevational gradient on Mauna Loa Volcano, Hawai'i. The composition, vigor, and survivorship of plants were examined on a 2400-yr-old pahoehoe lava flow at three elevations: 1755,2000, and 2195 m above sea level. Three plant species, Coprosma ernodeoides A. Gray, Styphelia tameiameiae (Cham. & ScWechtend.) F. v. Muell., and Vaccinium reticulatum Sm., were encountered most frequently at the three sites. Greatest mortality occurred at the site at 2000 m elevation, where the drought caused a shift from a slight excess of precipitation over evaporation to a large excess of evaporation. Occasional severe droughts may play an important part in shaping primary succession in this region

Recent Climate History of Hawaii

The recent energy and synoptic climate of Hawaii is examined in this article. The results indicate trends in the energy climate, increasing temperature and decreasing solar radiation, though no evidence is found of trends or cycles in the synoptic climatic elements, rainfall and sea level pressure

Potential evapotranspiration on small Pacific islands

M.A. University of Hawaii at Manoa 1984Includes bibliographical references (leaves 38-51).M.A

Climatic Controls on Evaporation in Hawaiʻi

PhD University of Hawaii at Manoa 1989Includes bibliographical references (leaves 189–198).The primary aims of this dissertation are to identify and explain variation in potential evaporation at different elevations and different exposures on tropical high islands, to provide reference data for modeling evaporation, and to suggest how an evaporation model appropriate for tropical high islands might be developed. New evaporation measurements on Haleakala, Maui, existing data from climate stations on Haleakala (Mauinet), pan evaporation data, and rawinsonde data are analyzed to study the effects of radiation, advection, and high elevation on the evaporation rate. The most important contribution of this study is in quantifying the importance of advection in controlling the evaporation rate on tropical high islands. Sensible heat advection from the surrounding ocean moderates the evaporation rate at coastal sites. This effect ranged, on average, from 0.85 mm/day enhancement in November to 0.71 mm/day suppression in June. Heat advection from land sources increases the evaporation rate by as much as 2.8 mm/day in central Maui. Large-scale subsidence over the Hawaiian Islands region accounts for an additional source of advection enhancing evaporation above approximately above 1200 m on the mountain. Preliminary results indicate that this effect increases with elevation in conjunction with the night evaporation rate. Cloud patterns over the mountain slopes and optical air mass determine the solar radiation receipt (the primary source of energy for evaporation) pattern which ranged from 85% to 51% of clear-day radiation in summer and 80% to 63% in winter. Insolation declined with elevation over the study site, except above 1200 meters in winter where it increased with elevation. Results of the study indicate that climatic-average potential evaporation can be modeled using the Priestley-Taylor equation modified by advection approximations. Temperature and vapor pressure on the mountain can be estimated using rawinsonde data. Net radiation can be mapped from global radiation using a clear-day radiation baseline reduced to the open-ocean global radiation value, 80%, and further reduced based on a cloud index derived using a wind flow model. Ocean advection can be accounted for at the lower elevations by simply adding a monthly modifier based on results presented in the study. Land advection can be related to soil moisture, estimated using a water balance. The influence of the evaporation enhancement at high elevations would probably have to be determined empirically, and related to season and elevation

Elevational patterns of climate on the leeward slope of East Maui, Hawaii

Reports were scanned in black and white at a resolution of 600 dots per inch and were converted to text using Adobe Paper Capture Plug-in.The climate of the main Hawaiian islands is strongly influenced by persistent subsidence inversion and trade winds characteristic of the region. In the middle and upper elevations of the high volcanic peaks climate is directly affected by the presence and movement of this inversion. Five climate stations have been operating on an altitudinal transect between 950 meters and 3000 meters elevation on the leeward side of East Maui in order to measure and describe the climate zones created by the inversion layer. Hourly measurements of solar radiation, net radiation, air temperature, relative humidity, wind, rainfall and atmometer evaporation were made. This report documents the results of these measurements in terms of elevational, annual and diurnal patterns, as well as addressing some aspects of climate variability and the applications of this data in estimating rates of potential evapotranspiration. This report summarizes two to three years of data from these climate stations and can be used as a reference for future research on the relationship between native ecosystems and climate within the area of study.National Park Service Cooperative Agreement CA 8032 2 000