"The Effects of Humidity on Aerosol Radiative Properties"
The understanding of the direct effect of aerosols on the atmospheric radiation balance is of importance if climate simulations are to become more accurate. To address this issue, during July 1996, the Tropospheric Aerosol Radiative Forcing Observational eXperiment, TARFOX, was held off the East coast of the USA. This multi-platform international experiment aimed to carry out column closure experiments where the physical and chemical properties of the aerosol, coming off the continental USA, were studied, along with observations being made of the radiation balance.
An important issue that needs to be addressed is the effects of humidity on aerosol growth and the radiative scattering properties of the aerosol. This paper will present some results of aerosol studies carried out using data gathered by the UK Meteorological Office Meteorological Research Flight (MRF) C130 aircraft during the TARFOX field experiment.
Measurements of the accumulation mode aerosol size spectra, over the size range 0.1 - 3.0 mm diameter, were made on board the MRF C130 simultaneously using a PCASP and an ASASP-X. The PCASP measured the aerosol at their ambient relative humidity whilst the ASASP-X dried the aerosol before sizing them.
These data are used to show the effects of relative humidity on aerosol growth and to test a range of aerosol growth models. The effects of dilution of the aerosol on its refractive index and results showing the resulting sensitivity to the aerosols radiative properties will be presented.
It is found that it is of great importance to account for the hygroscopic nature of the aerosols in radiative transfer calculations if realistic estimates of their effects are to be achieved.
Return to Abstracts page|
Last updated Apr-30-1997
Responsible NASA Official: Dr. Philip Russell
Webmaster: Ken Bollinger