Open AccessDewpoint and Humidity Measurements and Trends at the Summit of Mount Washington, New Hampshire, 1935–2004
Author(s) -
Thomas M. Seidel,
Andrea Grant,
Alexander A. P. Pszenny,
Daniel J. Allman
Publication year - 2007
Publication title -
journal of climate
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.315
H-Index - 287
eISSN - 1520-0442
pISSN - 0894-8755
DOI - 10.1175/2007jcli1604.1
Subject(s) - dew point , relative humidity , environmental science , humidity , mixing ratio , atmospheric sciences , climatology , dew , wet bulb temperature , spring (device) , meteorology , geography , geology , mechanical engineering , engineering , condensation
Meteorological conditions have been recorded at the summit of Mount Washington, New Hampshire, (44°16′N, 71°18′W, 1914 m ASL) since November 1932. Use of consistent instrumentation allows analysis of humidity measurements as calculated from error-checked dry bulb temperature, wet bulb temperature, and pressure during the period 1935–2004. This paper presents seasonally and annually averaged dewpoint temperature, mixing ratio, and relative humidity means and trends, including clear-air and fog subsets and, beginning in 1939, day and night subsets. The majority of linear trends are negative over the full study period, although these decreases are not constant, with relatively large (small) values in the mid-1950s (late 1970s). Annual mean dewpoint (water vapor mixing ratio) over the 70-yr period has decreased by 0.06°C decade−1 (0.01 g kg−1 decade−1). During this period the annual frequency of fog increased by 0.5% decade−1. Dewpoint and mixing ratio trends, both generally decreasing, differ by season; they are smallest in spring and greatest in fall. Relative humidity has decreased most in winter. The clear-air subset shows significant decreases in both dewpoint and mixing ratio for all seasons except spring.