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Aircraft observations of cloud droplet number concentration: Implications for climate studies
Author(s) -
Gultepe I.,
Isaac G. A.
Publication year - 2004
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1256/qj.03.120
Subject(s) - atmospheric sciences , environmental science , radiative forcing , cloud forcing , cloud computing , forcing (mathematics) , aerosol , atmosphere (unit) , planetary boundary layer , function (biology) , meteorology , boundary layer , physics , thermodynamics , evolutionary biology , biology , computer science , operating system
Droplet number concentration ( N d) is a major parameter affecting cloud physical processes and cloud optical characteristics. In most climate models, N d is usually assumed to be constant or a function of the droplet and aerosol number concentration ( N a). Three types of cloud systems over Canada, namely Arctic clouds, maritime boundary‐layer clouds, and winter storms, were studied to obtain values of N d as a function of temperature ( T ). The probability density function of N d was also calculated to show the variability of this parameter. The results show that N d reaches a maximum at about 10 °C (200 cm −3 ) and then decreases gradually to a minimum (∼1–3 cm −3 ) at about −35 ° C. A comparison of relationships between N d and N a indicates that estimates of N d from N a can have an uncertainty of about 30–50 cm −3 , resulting in up to a 42% uncertainty in cloud short‐wave radiative forcing. This study concludes that the typical fixed values of N d, which are ∼100 cm −3 and ∼200 cm −3 for maritime and continental clouds, respectively, and the present relationships of N d to N a, could result in a large uncertainty in the heat and moisture budgets of the earth's atmosphere. It is suggested that the use of relationships between N d and T can improve climate simulations. © Crown copyright, 2004. Royal Meteorological Society